ABO antigens:
A system of genetically determined antigens (proteins) located on the surface of the erythrocyte. The presence of these specific antigens gives a blood its unique properties. Because of the antigen differences existing between individuals, blood groups are significant in blood transfusions, maternal-fetal incompatibilities (erythroblastosis fetalis), tissue and organ transplantation.
ABO blood group:
The major human blood type system which describes the oligosaccharide glycoprotein antigens found on the surface of human blood cells. According to the type of antigen present, a person may be assigned a blood type of A, B, AB or O. A second type of antigen, the Rh factor, renders a positive or negative blood type. The ABO blood group system is important because it determines who can donate blood to or accept blood from whom. Type A or AB blood will cause an immune reaction in people with type B blood and type B and AB blood will cause a reaction in people with type A blood. Conversely, type O blood has no A or B antigens, so people with type O blood are universal donors. And since AB blood already produces both antigens, people who are type AB can accept any of the other blood types without suffering an immune reaction.
ACD:
A solution of acid, citrate, and dextrose used as an anticoagulant and preservative in storing blood for transfusions.
Abscess:
Localized collection of pus.
Accolé:
Early ring form of Plasmodium falciparum found at margin of red cell.
Accuracy:
The agreement of the test result with the true value of the sample.
Acetal:
Product of a reaction between two alcohol molecules with an aldehyde. The product of a hemiacetal and an alcohol. Eg., the formation of a glycosidic bond in polysaccharide formation.
Acetaminophen:
A pain reliever and fever reducer; the active ingredient in many medications. An overdose may be toxic.
Acetic acid:
The acid found in vinegar, often used as a reagent: also used in the preparation of pharmaceuticals, and in industry.
Acetobacterium:
Gram negative, anaerobic, ellipsoid bacterium that may oxidize hydrogen gas and reduce carbon dioxide or ferment carbohydrates to acetic acid (vinegar).
Acetoin:
The same as acetylmethylcarbinol. An intermediate in the 2,3-butanediol fermentation which is used to detect the pathway. See Voges-Proskauer test.
Acetone-butanol fermentation:
A fermentation pathway in which the major waste products are carbon dioxide, acetone, and butanol. Species of Clostridium carry out this type of fermentation.
Acetylcholinesterase (AChE):
An enzyme present in various tissues, including muscle and red cells, that breaks down acetylcholine (a chemical released by nerves that activates muscle contractions) and
helps to maintain proper transmission of impulses between nerve cells and between nerve cells and muscles; also called true cholinesterase. Measuring acetylcholinesterase in
amniotic fluid may help confirm a suspected neural tube defect in the fetus.
Acetylsalicylic acid (ASA):
Aspirin; salicylate. A pain reliever and fever reducer. See salicylates. An overdose can be toxic.
Achiral:
Not chiral. A compound that is superimposible on its mirror image. For example CH4.
Acid:
A molecule which is capable of donating a proton (H+). Since the hydrogen ion is a bare proton, it usually exists in a solvated form (such as H3O+). Eg., Formic acid is an organic acid. HCOOH = HCOO- + H+ .
Acid dyes:
Dyes in which the colored portion is negatively charged. Used to stain positively charged structures within cells or the background.
Acid-fast:
Characteristic of certain bacteria, such as mycobacteria, that involves resistance to decolorization by acids when stained by an aniline dye, such as carbolfuchsin. The property, shared by most mycobacteria and some nocardiae, of retaining heated carbofuchsin, even after treating with an acidified decolorizing (leaching) agent.
Acid phosphatase (Acid phos):
An enzyme found primarily in the prostate and semen. Increased blood serum levels may indicate cancer of the prostate or may follow prostatic massage.
Acidophile:
An organism that grows at (or requires) low pH values.
Acidosis:
A condition marked by an accumulation of acids in body tissues and blood that may result from prolonged diarrhea or disorders such as diabetes and kidney disease, when not
under control. Urine tests screen for acidosis. Determination of blood pH provides more accuracy.
Acinetobacter calcoaceticus:
Gram negative, aerobic, short bacilli in pairs and short chains, which oxidize carbohydrates.
Acinus:
A small group of cells arranged in a "grape-like" cluster. A classical example is the arrangement of pancreatic exocrine cells, but the term is also applied to larger groups of cells, as in the liver.
Acquired immunodeficiency syndrome:
Severe immune deficiency disease caused by human imunodeficiency virus (HIV-1) infection of the T cells, characterized by opportunistic infections and other complications. See AIDS.
Acrasiomycetes:
A class of fungi known as cellular slime molds. During part of their life cycle, they resemble amebae. Upon nutrient deprivation, the amebae congregate and form a multicellular structure called a pseudoplasmodium. The pseudoplasmodium forms a fruiting body that contains spores. The spores germinate into amebae. The cells may develop cellulose cell walls - unusual for fungi, which generally have chitin cell walls.
Acrocentric:
A chromosome structure in which the centromere is close to one end.
Acromegaly:
A disease state associated with excessive secretion of growth hormone in adults.
Acrosome reaction:
A membrane fusion event that releases enzymes from the head of the sperm to facilitate fertilization.
ACTH:
Adrenocorticotropic hormone - a peptide hormone secreted from the anterior pituitary that stimulates secretion of glucocorticoids from the adrenal cortex. More specifically, it stimulates secretion of glucocorticoids such as cortisol, and has little control over secretion of aldosterone, the other major steroid hormone from the adrenal cortex. Another name for ACTH is corticotropin. ACTH is secreted from the anterior pituitary in response to corticotropin-releasing hormone from the hypothalamus. Corticotropin-releasing hormone is secreted in response to many types of stress. Corticotropin-releasing hormone itself is inhibited by glucocorticoids, making it part of a classical negative feedback loop.
Actinomycetes:
Gram positive, irregularly-staining, rod-shaped, diphtheroid or branched, nonmotile, aerotolerant or anaerobic bacteria. In the 8th edition of Bergey’s there were eight families in the order Actinomycetales: Actinomycetaceae, Mycobacteriaceae, Frankiaceae, Actinoplanaceae, Dermatophilaceae, Nocardiaceae, Streptomycetaceae, and Micromonosporaceae. In the 9th edition the actinomycetes have been broken up and placed in a number of sections (16, 17, 27, 28, 29, and 30).
Activated partial thromboplastin time (aPTT):
The activated partial thromboplastin time (aPTT) is an assay used to screen for abnormalities of the intrinsic clotting system. It is also used to monitor the anticoagulant effect of circulating heparin.
Activation energy:
The amount of energy (expressed in joules) that is needed to convert all the molecules in one mole of a reacting substance from a ground state to the transition state.
Acute:
Having a short and relatively severe course.
Acute lymphoblastic leukemia (acute lymphocytic leukemia) (ALL):
A rapidly progressing cancer of the blood affecting the type of white blood cell known as lymphocytes. It is the most common form of childhood leukemia.
Acute serum:
Serum collected for antibody determination early in the course of an illness when there
would have been little or no antibody produced.
Acute urethral syndrome:
Lower urinary tract infection that may be difficult to differentiate from cystitis; seen most commonly in younger, sexually active females and caused by Escherichia coli (counts as low as 100 per milliliter may be significant in this situation), Chlamydia, and other organisms.
Acyl group:
An alkyl group whose functional group is a carboxyl group, -RHCOO.
Ad:
Symbol for a dichromatic absorbance. It is equal to the absorbance at the secondary wavelength subtracted from the absorbance at the primary wavelength.
Addison's disease:
A rare endocrine disease that results from the underproduction of aldosterone and cortisol (hormones) by the adrenal glands. Symptoms include weakness, low blood pressure, anemia, low blood sugar and electrolyte abnormalities.
Addition reaction:
Reaction in which an unsaturated system is saturated or part saturated by the addition of a molecule across the multiple bond. E.g. the addition of bromine to ethene to form 1,2-dibromoethane.
Adenosine triphosphate:
ATP
Adenylyl cyclase:
An enzyme and integral membrane protein that converts ATP to cyclic AMP.
Adipocyte:
A fat cell. Adipose tissue is composed predominantly of adipocytes.
Adipose tissue:
Fatty tissue.
Adjuvant:
Compound that increases the efficiency of antigens to induce an immune response.
Adrenal glands:
Located near the kidneys, the adrenal glands produce a small amount of the male hormone, testosterone.
Adrenalin:
A trade name for the hormone epinephrine.
Adrenocorticotropic hormone:
A peptide hormone secreted from the anterior pituitary that stimulates secretion of glucocorticoids from the adrenal glands.
Aedes sp.:
Mosquito vectors for encephalitis (EFE, WEE, yellow fever).
Aedes aegypti:
Mosquito vector for the yellow fever virus and the Dengue fever virus.
Aerobe, obligate:
Microorganism that lives and grows freely in air and cannot grow anaerobically. Examples are Micrococcus and Pseudomonas.
Aerobic:
In the presence of oxygen (opposite of anaerobic).
Aerogenic:
Producing gas (in contrast to anacrogenic: non-gas-producing).
Aerosol:
Atomized particles suspended in air; microorganisms suspended in air.
Aerotolerant:
Ability of an anaerobic microorganism to grow in air, usually poorly, especially after initial anaerobic isolation. Examples are Streptococcus and Lactobacillus.
AFB:
Acid-fast bacilli.
Aflatoxins:
Toxins harmful to animals and humans, produced by fungi growing on wheat, rye, corn, and other grains. Some of the toxins cause cancer in animals and humans.
Agar:
A medium used to grow microorganisms.
Aeromonas hydrophila:
Gram negative, polarly flagellated, facultatively anaerobic, oxidase-positive, rod-shaped bacterium.
Aeromonas shigelloides:
Afferent:
Conveying or carrying toward a center (opposite of efferent). Example: an afferent neuron carries information from the hand toward or to the central nervous system.
Agarose gel electrophoresis
Separation of proteins based on molecular weight and isoelectric character by electrical-current-stimulated movement through a semisolid gel matrix.
Agglutination:
The clumping together of cells due to the binding of agglutinin (a protein) molecules on the surface of each cell. The clumping together of two organisms of the same species for the purpose of sexual reproduction. Often conducted by means of a carbohydrate on one organism and a protein on the other, resulting in a glycoprotein.
Agglutinins:
Antibodies that bind cells together, causing them to clump.
Agonist:
In receptor-ligand interactions, an agonist is a molecule that binds receptor and fully induces post-receptor signalling events. The opposite of antagonist.
AIDS:
Acquired immunodeficiency syndrome. A condition in which the normal immune system becomes depressed, rendering the affected individual unable to fight a number of serious and fatal infections. Human T-cell leukemia/lymphoma virus (HTLV-III) is associated with AIDS. The virus has been renamed Human Immunodeficiency Virus (HIV). The presence of HIV
antigen in the blood will confirm that an individual is infected with the virus and has AIDS. The presence of HIV antibody in the blood confirms that an individual has been infected with the AIDS virus. See antigen and antibody.
AIDS-related complex:
Prodromal symptoms in patients infected with HIV virus, including lymphadenopathy, fever, weight loss, and malaise. See ARC.
Albumin:
The most abundant protein component of blood, Produced primarily in the liver, albumin helps to keep the fluid portion of blood within the vessels, and helps transport drugs
and other substances by way of the bloodstream. Low levels of albumin in the blood or its presence in urine may signal edema (the accumulation of fluid) as in pedal edema (in
the ankles) or pulmonary edema (in the lungs), which may be symptoms of congestive heart failure, kidney or liver disease.
Albuminuria:
The presence of protein in the urine, principally albumin, generally indicating kidney disease.
Alcaligenes:
Gram negative, peritrichously flagellated, aerobic, oxidase positive coccobacilli.
Alcohol:
Organic molecule which contains an hydroxyl functional group, eg., R-CH2OH.
Alcoholic (ethanolic) fermentation:
A fermentation in which the major waste products are carbon dioxide and alcohol (ethanol).
Alcoholism:
A disorder characterised by pathological pattern of alcohol use that causes a serious impairment in social or occupational functioning. Termed alcohol abuse or, if tolerance or withdrawal is present, alcohol dependence.
Aldehyde:
Carbonyl carbon with at least one hydrogen bonded to the carbon. Compound or molecule whose functional group is an aldehyde, eg., R-CH=O.
Aldosterone:
A steroid hormone produced by the adrenal cortex that participates in control of sodium, potassium and water balance.
Alk (or K):
Alkaline.
Aliphatic:
An open chain carbon molecule; a non-aromatic hydrocarbon.
Alkaline phosphatase (Alk phos or ALP):
An enzyme found mainly in liver and bone. Blood serum alkaline phosphatase is usually measured to detect liver or bone disease.
Alkalinophile or Alkalophile:
An organism that grows under basic conditions or at a high pH.
Alkalosis:
A condition in which the blood and tissues contain an abnormally high level of alkali (usually too much bicarbonate), often caused by prolonged vomiting or hyperventilation.
Symptoms include dizziness and jerky muscular contractions. Alkalosis can be detected in a urine test. Determination of blood pH provides more accuracy.
Alkane:
A saturated hydrocarbon containing single carbon-carbon bonds, eg., Butane, CH3CH2CH2CH3.
Alkene:
A hydrocarbon compound containing one or more carbon-carbon double bond(s); an unsaturated hydrocarbon, eg., 2-Butene, CH3-HC=CH-CH3.
Alkyl:
An alkane with a hydrogen replaced by a bond to another molecule or functional group, eg., Butyl, CH3CH2CH2CH2-.
Allele:
An alternate form of a gene.
Allergens:
Antigens that initiate a hypersensitive (allergic) reaction.
Allergy:
An overactive response by the immune system to an antigen which results in a diseased state (e.g. asthma, rash, welts). An allergy may be mediated by humoral antibodies or T-lymphocytes.
Allosteric regulation:
A type of enzyme regulation in which a small molecule (effector) binds to the enzyme at a site other than the catalytic site, thereby altering the conformation of the enyzme and its catalytic activity.
Allyl group:
A group containing 3 carbon atoms and a double bond: C1=C2-C3, where C3 is called the allylic position or allylic carbon atom.
Allylic rearrangement:
The migration of a double bond in a 3-carbon group from carbon atoms one and two to carbon atoms two and three, e.g. C1=C2-C3-R to R-C1-C2=C3.
Alopecia:
Baldness.
Alpha-fetoprotein (AFP):
A substance produced by the fetus that is found in fetal serum, amniotic fluid, and the mother's bloodstream. Elevated levels of AFP may indicate that the baby has a neural
tube defect such as spina bifida (incomplete closure of the spinal column) which can lead to paralysis of the lower limbs, repeated urinary tract infections, mental retardation
or hydrocephalus ("water on the brain"). It is also a useful nonspecific tumor-associated antigen (tumor marker).
Alpha cell:
A type of cell in the endocrine pancreas that secretes the hormone glucagon.
Alpha helix:
Secondary structure of large biomolecules involving a uniformed right-handed coiling of the molecule. This structure is stabilized by hydrogen bonds. Associated with proteins and DNA.
Alzheimer's disease:
A disorder marked by progressive mental deterioration (dementia), including memory loss, confusion, reduction of functional activity, and fluctuations in alertness, usually
beginning in later middle life. Use of dexamethasone suppression test (DST) has been suggested to help in differential diagnosis of dementia and depression (also a frequent disease of later life). This is important, as adequate treatment may produce improvement in depressive disease. See dexamethasone suppression test.
AMI:
Antibody-mediated immune response. Also, Acute Myocardial Infarction.
Amide:
A compound containing a nitrogen covalently linked to a carbonyl carbon.
Amine:
Organic compound which contains an ammonia nitrogen for a functional group. One or more hydrogens of ammonia have been substituted for an organic substiuent.
Amino acid:
A class of organic molecules that contains an amino group and can combine in linear arrays to form proteins in living organisms. There are twenty common amino acids: alanine, arginine, aspargine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. They are key components in all living things from which proteins are synthesised by formation of peptide bonds during ribosomal translation of messenger RNA. All the amino acids have the L configuration, except glycine which is not optically active. Other amino acids occurring in proteins, such as hydroxyproline in collagen, are formed by post translational enzymatic modification of amino acid residues in polypeptide chains. There are also several important amino acids, such as the neurotransmitter gamma-aminobutyric acid, that have no relation to proteins. Amino acids can now be produced by biotechnology in bulk using fermentation and biotransformation. See Table of Amino Acids.
Amino terminus (amino terminal):
The end of a polypeptide that carries a free amino group. The first amino acid in a peptide or protein is called the amino terminal or N-terminal amino acid.
Aminoacyl-tRNA:
An amino acid-tRNA complex.
Aminoacyl-tRNA synthetase:
An enzyme that hooks together a specific tRNA and a specific amino acid.
Aminoglycosides:
Group of related antibiotics including streptomycin, kanamycin, neomycin, tobramycin, gentamicin, and amikacin specific for gram negative bacteria.
Ammonification:
The release of ammonium from organic molecules.
Amniotic:
Pertaining to the innermost fetal membrane forming a fluid-filled sac.
Amniocentesis:
A prenatal diagnostic procedure in which a needle is inserted through the mother's abdomen into the uterus and amniotic sac to remove a sample of amniotic fluid. The fluid,
containing fetal cells, proteins, and other substances, may be analyzed to detect genetic disorders, including Down syndrome (mongolism). An elevated level of AFP can indicate
neural tube defects. See neural tube defects.
Amniography:
A prenatal diagnostic procedure in which X-ray of the mother's uterus, after injection of a radiopaque substance, allows visualization of the fetus, the placenta, and the uterine lining. This may be used to confirm a diagnosis of neural tube defects.
Amniotic fluid:
The fluid surrounding the developing fetus that is found within the amniotic sac contained in the mother's womb.
Amoeba:
A protozoan that moves by extending pseudopodia and retracting terminal portions of the cell.
Amoeboid motion:
Movement due to the extension of one edge of a cell and the retraction of another edge.
Amperometry (amperometric):
An electroanalytical technique based upon the measurement of the current flowing through the working electrode of an electrochemical cell.
Amphetamine:
A compound (or its derivatives) that acts as a central nervous system stimulant. Used as a stimulant in depressed states, to reduce appetite, and in attention-deficit disorders, it can also alleviate nasal congestion. Amphetamine use can lead to dependence. It has a high potential for abuse. Blood and urine tests can detect amphetamine use and toxic
levels.
Amphipathic:
Having both hydrophilic ("water loving") and hydrophobic ("water hating") regions within the same molecule. Phospholipids and bile salts are examples of amphipathic molecules.
Amphoteric:
A state in which a molecule possesses both acid and base traits. Amino acids are amphoteric molecules.
Amplicon:
The product of PCR or LCR; a piece of DNA that has been synthesized using amplification techniques.
Amylase:
A digestive enzyme produced largely by the pancreas and salivary glands that converts starches to sugars (maltose). Abnormally high levels of amylase in the blood or urine may be found in patients with inflammation of the pancreas or salivary glands (mumps).
Anabolism:
The synthesis of compounds within a cell. The process by which organisms build complex molecules from simple molecules by expenditure of energy. The opposite of catabolism. See also Catabolism.
Anaerobe:
An organism that is inhibited or killed by the presence of molecular oxygen and obtains its energy by fermentative processes or anaerobic respiration.
Anaerobic:
In the absence of oxygen (opposite of aerobic).
Anaerobic respiration:
Respiration in which the final electron acceptor is an inorganic molecule (sulfate or nitrate) other than molecular oxygen.
Analyte:
A substance that is undergoing analysis or is being measured.
Analytic reagent (AR):
Grade of chemical of high purity.
Anamnestic response:
More rapid production of antibodies in response to exposure to an antigen previously encountered.
Anaphylactic shock:
Severe contraction of smooth muscle and excessive loss of fluid from the blood into the tissues due to an immediate allergic reaction (atopic hypersensitivity) mediated by IgE.
Anaphylatoxin:
The C3 and C5 complement proteins that cause basophils and mast cells to release various molecules, such as histamine, which cause inflammation.
Anaplasia:
Loss of a cell's differentiated state, or reversion to a more "primative" cellular phenotype. This usually is seen in association with cancer cells.
Anemia:
Below normal levels of red blood cells or hemoglobin, or both, which can be caused by many different conditions, including iron deficiency. Symptoms may include fatigue, weakness, headache, and dizziness. Appropriate blood tests will confirm the diagnosis of anemia and shed light on its etiology.
Anencephaly:
Abnormal development of the brain in the fetus accompanied by absence of the bones of the cranial vault. Children born with this severe disorder die shortly after birth. Measurement of maternal blood and amniotic fluid levels of alpha-fetoprotein (AFP) can help diagnose this condition and other neural tube defects. See alpha-fetoprotein.
Anergy:
Absence of reaction to antigens or allergens.
Aneuploid (aneuploidy):
Having less than or more than the normal diploid number of chromosomes; a common type of cytogenetic abnormality.
Angioplasty:
The surgical repair of a blood vessel. A balloon angioplasty is a noninvasive procedure where a balloon-tipped catheter is introduced into a diseased blood vessel. As the balloon is inflated, the vessel opens further allowing for improved flow of blood.
Angiotensin converting enzyme (ACE):
Angiotensin converting enzyme cleaves the decapeptide angiotensin I (biologically inactive) to form active angiotensin II. Angiotensin II causes contraction of vascular smooth muscle and thus raises blood pressure and stimulates aldosterone release from the adrenal glands. Angiotensin is finally broken down by angiotensinases. Elevations in angiotensin converting enzyme are seen in sarcoidosis, histoplasmosis, alcoholic cirrhosis, asbestosis, berylliosis, diabetes, Hodgkin's disease, hyperthyroidism, amyloidosis, primary biliary cirrhosis, idiopathic pulmonary fibrosis, pulmonary embolism, scleroderma, silicosis, tuberculosis, Gaucher's disease and leprosy. The normal values are 18 to 67 U/ml over 20 years of age (people under 20 have higher levels).
Anhydrous:
A substance that does not contain water. The opposite of hydrous.
Anion:
A negatively charged ion.
Annealing of DNA:
The joining together, through hydrogen bonding, of complementary strands of DNA.
Anomeric carbon:
The asymmetric carbon created with carbohydrates form the closed ring structure with a hydroxyl oxygen (i.e. furanose or pyranose). The carbon that is responsible for defining whether a carbohydrate anomer is in an alpha or beta configuration.
Anopheles sp.:
Mosquito vectors for the malaria parasite and the western equine encephalitis (WEE) virus.
Anorexia:
A lack or loss of appetite for food.
Antagonism:
Diminution of activity of one drug by a second one.
Antagonist:
In receptor-ligand interactions, an antagonist is a molecule that binds receptor, blocks the binding of agonist but fails to induce post-receptor signalling events.
Anthrax:
See Bacillus anthracis.
Antiarrhythmic:
Any one of a group of drugs which prevent or control irregularities in the heart beat.
Antiasthmatic:
Any one of a group of drugs which prevent or control spasms and narrowing of the lung's bronchi and bronchioles.
Antibiogram:
Distinctive pattern of susceptibility of an organism to a battery of antimicrobial agents.
Antibiotics:
Any substance derived from fungi or bacteria that destroys or inhibits the growth of microorganisms.
Antibody (Ab):
A substance produced by the body in response to an antigen that specifically reacts with the antigen to destroy, inhibit, or neutralize it. The body produces antibodies as
a defense against foreign substances. Antibodies may be identified and measured to determine whether an individual has been infected by a pathogen.
Antibody assays:
Tests to determine levels of specific antibodies in the blood.
Anticoagulant:
A chemical used to prevent blood clotting. Examples: EDTA, heparin, sodium citrate, sodium oxalate.
Anticonvulsant:
Any of a group of drugs that prevent seizures or control their incidence or severity.
Antidiuretic hormone (ADH):
A peptide hormone secreted from the posterior pituitary that affects the kidney and vascular system to conserve body water and increase blood pressure. Also known as vasopressin.
Antigen (Ag):
Any substance that when introduced into the body (such as the protein coat of an invading pathogen) causes the formation of antibodies. Ag is also found on tissue and blood cells, and in body fluids. Measurement of antigen can help determine whether a particular disease will become active.
Antimicrobial
Chemical substance, either produced by a microorganism or by synthetic means, that is
capable of killing or suppressing growth of microorganisms.
Antiseptic:
Compound that stops or inhibits growth of bacteria without necessarily killing them.
Antitoxin:
Antibody that inactivates a toxin. A purified antiserum from animals (usually horses) immunized by injections of a toxin or toxoid, administered as a passive immunizing agent to neutralize a specific bacterial toxin, for example, botulinus, tetanus or diphtheria.
Apheresis:
A method of blood collection in which whole blood is withdrawn, a desired component separated and retained, and the remainder of the blood returned to the donor.
Aplastic Anemia:
Anemia caused by the reduction or depletion of hematopoietic precursor cells due to the
destruction of bone marrow by chemical agents or physical factors. The decreased production of erythrocytes, leukocytes, and platelets results in peripheral pancytopenia.
Apoptosis:
Programmed cell death.
Appendix:
A wormlike extension of the cecum in humans; part of the large intestine.
Aquaporins:
A family of proteins that function as water channels in cell membranes.
Arboviruses:
Viruses carried by arthropod vectors which multiply in the arthropod and in the vertebrate host. The arboviruses cause various types of encephalitis (EEE, VEE, WEE, St. Louis) and yellow fever.
ARC:
AIDS-related complex. A condition in which antibody tests for AIDS virus are positive and patients may exhibit enlarged lymph nodes, fatigue, fever, night sweats, weight loss,
and unexplained diarrhea, but do not have any of the more serious complications of AIDS. Also, American Red Cross.
Archaebacteria:
Prokaryotes that lack the usual peptidoglycan (murein) in their cell walls, and that have phospholipids with ether bonds rather than the usual ester bonds. Many of the archaebacteria are chemoautotrophic methanogens, reducing carbon dioxide with electrons from hydrogen. Another large group are the sulfur oxidizing chemoautotrophic extreme thermophiles. The archaebacteria are generally found in extreme environments where high temperatures, high salinity, and high acid content are the rule. Examples of archaebacteria are Sulfolobus, Thermoplasma, Halobacterium, and Methanobacterium.
Aromatase:
An enzyme which converts androgens to estrogens by desaturating the A-ring of the steroid. This enzyme complex is located in the endoplasmic reticulum of estrogen-producing cells including ovaries, placenta, testicular sertoli and leydig cells, adipose, and brain tissues. The enzyme complex has two components, one of which is the cyp19 gene product, the aromatase cytochrome p-450. The other component is NADPH-cytochrome p-450 reductase which transfers reducing equivalents to p-450(arom).
Aromatic or Aryl:
Ringed, unsaturated, hydrocarbon with the electrons of the carbon double bonds being shared resonance among the carbons involved. These are often fragrant and are commonly called aromatic. A Benzene ring or its derivative. An aromatic molecule or ion possesses aromaticity. Aromaticity is the property of planar (or nearly planar) cyclic, conjugated systems having (4n+2) conjugated pi electrons. The delocalization of the (4n+2) pi electrons gives them stability. For benzene, the most common aromatic system (n = 1, therefore 6 pi electrons), the aromaticity confers the characteristic reactivity of electrophilic substitution.
Arrhenius plot:
A plot of the logarithm of reaction rate against the reciprocal of absolute temperature. For a single stage reaction this gives a straight line from which the activation energy and the frequency factor can be determined. Often applied to data from complex biological systems when the form observed is frequently a series of linear portions with sudden changes of slope. Great caution must be observed in interpreting such slopes in terms of activation energies for single processes.
ART:
Automated Reagin Test for syphilis.
Arteriogram:
X-ray visualization of the arterial lining after injection of radiopaque dye into a specific artery or into the bloodstream. It aids in the diagnosis of vascular occlusions
and of athrosclerotic plaques, as well as of other cardiovascular abnormalities.
Arthritis (septic):
Infection of synovial tissue and joint fluid of one or more joints; characterized by
joint pain, stiffness, swelling, and fever.
Arthrobacter:
Gram positive, aerobic coccobacilli, showing great variation in size; may be flagellated.
Arthroconidium:
Spore formed by septation of a hypha and subsequent separation of septa.
Arthropods:
Invertebrate animals with jointed legs, such as the insects and arachnids.
Ascites:
An effusion and accumulation of serous fluid in the abdominal cavity. Synonym: abdominal dropsy, peritoneal dropsy, hydroperitonia, hydrops abdominis.
Ascitic fluid:
Serous fluid in peritoneal cavity.
Ascomycetes:
A class of fungi that produces sexual spores called ascospores inside a sack known as the ascus. Ascomycetes produce asexual spores called conidia. Examples include the mold Neurospora and the yeast Saccharomyces.
Asepsis:
The absence of contaminating or infecting microorganisms. Asepsis does not imply sterility See Sepsis.
Aseptic technique:
Procedures that reduce the risk of contaminating materials or infecting patients.
Aspergillus:
A fungus belonging to the class Deuteromycetes.
Assay:
Analysis of a substance, or of components in a mixture, or of the biological, chemical, or pharmacological potency of a drug. Forms of assay include: Endpoint assay —
a single measurement is made at a fixed time. Kinetic assay - increasing amounts of a product are formed with time, and are monitored at multiple points. Microbiological assay
— measurement of the concentration of antimicrobials in biological material. Immunological assay — analysis or measurement is based on antigen-antibody reactions.
Assay (immunological):
There are many types of immunological assays, including agglutination, complement-fixation, precipitation, immunodiffusion, and electrophoretic assays. Each type of assay utilizes either a particular type of antibody or a specific support medium (such as a gel) to determine the amount of antigen present.
Assay (Indicator-labeled immunoassays):
Indicators are attached to the antigen or to the antibody to demonstrate that the antigen-antibody reaction has occurred. These assays have enabled measurement of many substances not previously measurable. Among these assays are:
Enzyme immunoassay (EIA): An enzyme is used to label antibody or antigen to determine the concentration of either.
Enzyme-linked immunosorbent assay (ELISA): A form of enzyme immunoassay in which an enzyme-labeled antibody or antigen competes with the unknown substance.
Enzyme-multiplied immunoassay technique (EMIT): A form of EIA used frequently for assays of drugs and hormones, as well as for viral antigens.
Fluorescence immunoassay (FIA): A fluorescent label that can be measured is used in a competitive-binding assay.
Fluorescence polarization immunoassay (FPIA): A technique used to analyze low molecular weight substances by polarization — forcing natural light into a single plane by
prisms and lenses — and by labeling molecules with fluorescence.
Radioimmunoassay (RIA): A competitive-binding assay that employs radiolabeled antigen or antibody.
Assimilation (microbiologic):
Utilization of nutrients. Assimilation tests are used to determine whether yeasts are
able to grow with only a single carbohydrate or nitrate; these tests are useful for classification of yeasts.
Asymmetric carbon:
A chiral carbon that is responsible for stereoisomers. Any carbon to which there are 4 different groups attached.
ATCC:
American Type Culture Collection.
Atherosclerosis:
The progressive narrowing and hardening of the arteries over time. This is known to occur to some degree with aging, but other risk factors that accelerate this process have been identified. These factors include: high cholesterol, high blood pressure, smoking, diabetes and family history for atherosclerotic disease.
Attenuation:
A decrease in light due to absorption by a chromagen in radiative energy attenuation technologies.
Atopic hypersensitivity:
IgE-mediated immediate allergic reaction.
ATPase: Na(+)-K(+):
The "sodium pump". A membrane protein that pumps 3 sodium ions out of cells in exchange for 2 potassium ions in a reaction that hydrolyzes ATP. Critical in maintaining low intracellular sodium and resting membrane potential.
Autoclave:
Instrument consisting of a double-walled, sealable enclosure in which steam heat at greater than atmospheric pressure is used to sterilize biologically contaminated material.
Autocrine:
The activity of a hormone or growth factors that binds to and affects the same cell that secreted it.
Autoimmune (autoimmunity):
A condition characterized by a specific humoral or cell-mediated immune response against constituents of the body's own tissues.
Autoradiography:
A specimen containing radioactive atoms is overlaid with a photographic emulsion (X-ray film), which is subsequently developed, revealing the localization of radioactivity as a pattern of silver grains. Resolution is determined by the path length of the radiation and so the low energy beta emitting isotope, tritium, is usually used. The technique can be used to visualise radioactively labelled molecules or fragments of molecules, used in analyzing length and number of DNA fragments after they are separated by gel electrophoresis.
Autotroph:
Organism that can utilize inorganic carbon sources (CO2).
Auxotroph:
Differing from the wild strain (prototroph) by an additional nutritional requirement. A mutant that cannot synthesize simple compounds, such as amino acids, nucleosides, and vitamins. A medium must be supplemented with these growth factors if the organism is to proliferate.
Avid:
The property of binding strongly, such as an antibody that strongly binds to an antigen.
Avidity:
Firmness of union of two substances; used commonly to describe union of antibody to antigen.
Axenic culture:
Pure culture of microorganisms.
Azotemia:
A higher than normal blood level of urea or other nitrogen containing compounds in the blood. The hallmark test is the serum BUN (blood urea nitrogen) level. Usually caused by the inability of the kidney to excrete these compounds.
Azotobacter:
Gram negative, aerobic, oval cocci; may be peritrichously flagellated; carries out nonsymbiotic nitrogen fixation.
Azurophilic Granules:
Cytoplasmic granules which may be present in all ypes of leukocytes as seen using Romanowsky-type stains. These are usually reddish blue in color, but vary in color intensity, number, and size within different leukocytes. These granules may be absent in certain forms of lymphocytes and monocytes, but not in normal granulocytes. Most of the azurophilic granules are lysosomal in nature, but not those of basophils. The affinity of the granules for azure dyes depends on the chemical nature of the granules, not in the functional classification.
B-cells:
B-lymphocytes that circulate in the lymph and blood and mature in the bone marrow and spleen. B-cells, when stimulated by foreign materials, differentiate into plasma cells and release antibodies into the lymph and blood.
Bacillus:
(1) A rod-shaped bacterium. (2) When capitalized and italicized (or underscored), the term refers to a bacterial genus: Gram positive, rod-shaped, flagellated or nonmotile, aerobic or facultatively anaerobic, endospore-forming bacteria.
Bacillus anthracis:
Bacillus anthracis is the cause of anthrax, primarily a disease of herbivorous animals, and relatively uncommon in man in the United States. The usual source of infection in man is cutaneous inoculation through cuts or scratches of the skin of men who occupationally handle livestock or hides. Pulmonary and alimentary infection are also possible. Neither exotoxins nor endotoxins have been demonstrated.
B. anthracis is a very large bacterium, a straight rod 5 to 10 microns in length and 1 to 3 microns in width, with square or concave ends. Individuals may occur singly, in pairs, or in long chains. They are encapsulated, non-motile, and stain Gram-positive. Spores are ellipsoidal or cylindrical, located centrally or paracentrally, and 0.8 to 1.0 micron by 1.3 to 1.5 microns. Germination is polar.
The species is aerobic but facultatively anaerobic. Optimal growth temperature is 37°C, but species will continue to grow at considerably higher or lower temperatures. Colonies will grow profusely on most common laboratory media. Agar colonies are large, dense, and irregular, composed of parallel chains of cells giving a curled or combed appearance. Broth cultures show a thick pellicle, but little or no turbidity. Blood hemolysis is variable. Lactose is not fermented, but acid without gas is produced from glucose. Neither morphological nor cultural characteristics will absolutely differentiate B. anthracis from similar but non-pathogenic species; testing for pathogenicity is essential.
Bacillus cereus:
Bacillus cereus closely resembles Bacillus anthracis in morphology and cultural characteristics.
Bacillus subtilis:
Bacillus subtilis is a common laboratory contaminant. The Gram-positive rods are 2.0 to 8.0 microns long and 0.7 to 0.8 microns wide, unencapsulated, and occurring as short chins or singly. Spores are ellipsoidal or cylindrical, located centrally or paracentrally. Spore germination is equatorial. Agar colonies are rough, opaque, dull, spreading, and off-white, but considerable variations occur. The species is considered non-pathogenic.
Bacteremia:
Presence of viable organisms in blood.
Bacterial vaginosis:
Noninflammatory condition in vagina characterized by foul-smelling vaginal discharge and presence of mixed bacteria.
Bactericidal:
Term used to describe a drug that kills microorganisms.
Bacteriocins:
Antibiotic-like substances, produced by bacteria, that exert a lethal effect on other bacteria. A special class of antibiotics.
Bacteroides:
Gram negative, rod-shaped, nonmotile, anaerobic, catalase negative (or weakly catalase positive) bacterium.
Bacteriophage:
Virus that infects a bacterial cell, sometimes bringing about its lysis.
Bacteriostatic:
Term used to describe a drug that inhibits growth of an organism without killing it.
Bacterium (plural, bacteria):
Any microorganism of the class Schizomycetes; composed of several structures, including a nucleus, cytoplasm and cytoplasmic membrane, cell wall, and capsule. Motile forms
may have flagella. Some of these one-celled organisms cause diseases.
Bacteriuria:
Presence of bacteria in urine.
Balantidium coli:
Ciliated protozoan that may cause diarrhea and dysentery.
Band neutrophil:
An immature neutrophilic granulocyte with a horseshoe- or sausage-shaped nucleus. A neutrophil in which the nucleus is not lobulated but is in the form of a continuous band, horseshoe-shaped, twisted or coiled. Composes 1 to 5 percent of the normal differential WBC count. Increased numbers are seen in acute infections and trauma.
BAP:
Blood agar plate.
Base:
A molecule that is capable of accepting a hydrogen ion (H+). Eg., NH3 + H+ = NH4+ where ammonia (NH3) is a base.
Basic dye:
A dye in which the colored portion is positively charged. A dye that stains cells.
Basidiomycetes:
A class of fungi that produces sexual spores, called basidospores, from a structure called the basidium. The meadow mushroom, Agaricus compestris, is an example of a Basidiomycete.
Basophil:
White blood cell that releases histamines and other compounds that act on smooth muscle and other tissues.
Basophilia:
The reaction of a cellular structure to basic dyes resulting in a blue, gray, or grayish-blue appearance.
Basophilic Stippling:
Red blood cell inclusion that consists of precipitated ribonucleoprotein and mitochondrial remnants. Stippling may be fine, coarse, or punctate and is seen in toxic states such as metal poisoning, severe bacterial infection or drug exposure.
Barbiturates:
A group of drugs derived from barbituric acid that is used to sedate, to control convulsions, or to induce sleep. Blood and urine tests can determine toxic levels of these compounds. Barbiturates may be habit forming and are controled substances.
Batch testing:
A laboratory testing procedure in which one test is done simultaneously on multiple specimens in a "batch analyzer," such as a centrifugal analyzer.
B cells (B lymphocytes):
Lymphocytes which transform into plasma cells and produce antibodies.
BCG:
Bacille Calmette-Guerin, an attenuated strain of Mycobacterium tuberculosis used for immunization.
Bdellovibrio bacteriovorus:
Small curved or spiral, gram negative, polarly flagellated, aerobic bacteria.
Beer-Lambert law:
The equation A=ECL, where A is the absorbance at a given wavelength of light, E is the molar extinction coefficient, C is the concentration of the molar solution, and L is the length of the light path. In words, the equation means that the concentration of a substance in moles is proportional to the absorption of a given wavelength of light by a solution of the substance. The equation is used in the study of spectroscopy.
Beggiatoa:
Gram negative, filamentous, gliding, aerobic to microaerophilic, hydrogen sulfide-oxidizing bacteria with numerous sulfur granules within their cytoplasms. These bacteria require organic compounds as their carbon source.
Behring, Emil von:
Beijerinckia:
Gram negative, oval or rod-shaped, peritrichously flagellated or nonmotile, aerobic bacteria, Molybdenum required for nitrogen fixation.
Benign tertian malaria
Malaria caused by Plasmodium vivax.
Benign tumor:
A tumor which is noncancerous.
Benzodiazepine:
A chemical that is often used as the active ingredient in mind-affecting drugs such as tranquilizers. Long term use can result in dependence. Benzodiazepine overdose can be
determined through blood or urine tests.
Bergey's Manual:
A book in four volumes that characterizes and classifies bacteria.
Beta cell:
A type of cell in the endocrine pancreas that secretes the hormone insulin.
Beta-lactamases:
Enzymes that destroy penicillins and/or cephalosporins and are produced by a variety of bacteria.
BFP:
Biological false-positive.
Bicarbonate:
Essential for regulating vital functions and one of the important buffers necessary to maintain normal acid-base balance in the body. Body metabolism results in mainly acid
production, and neutralizing some of such acids is its constant activity, thus it plays a key role in metabolic acidosis or alkalosis. Bicarbonate may be lost through watery
feces, or can decrease when lungs cannot expel carbon dioxide.
Bichromatic chemical analyzer:
Laboratory instrumentation that provides spectrophotometric-photometric monitoring at two different wavelengths to correct for background color which might interfere with measurement of an analyte.
Bichromatics:
Spectrophotometry which uses a secondary wavelength absorbance reading subtracted from a primary wavelength absorbance reading to obtain a delta absorbance reading (Ad). The
delta absorbance is used in conjunction with the calibration data to calculate concentration or activity.
Bi-directional:
Refers to communication between an instrument and a computer that allows the computer to send instructions to the instrument and for the instrument to send results back to
the computer.
Bifidobacterium:
Gram positive, highly variable, rod-shaped, nonmotile, anaerobic, catalase negative bacteria.
Bifurcated:
Divided into two branches.
Bile acids and bile salts:
Molecules derived from cholesterol and secreted into bile by liver cells.
Biliary:
Pertaining to or derived from bile, bile ducts and the gall bladder.
Biliary obstruction:
A blockage of the bile ducts can occur by a stone, tumour, pancreas (pancreatic tumour or swelling), bile duct inflammation, bile duct cysts, trauma, bile duct stricture or enlarged lymph nodes in the area. When bile duct obstruction occurs, bile accumulates in the liver and jaundice develops due to the accumulation of bilirubin in the bloodstream.
Bilirubin:
The orange-yellow pigment of bile, the green fluid that aids in digestion and that is secreted by the liver. Bilirubin is formed mainly by hemoglobin breakdown at the end of
red cell life and eventually most of it leaves the body in the feces. Two types are in the blood. Water insoluble or unconjugated bilirubin refers to the pigment before it reaches
the liver. In the liver it is converted to the water-soluble or conjugated bilirubin which is excreted into the bile. Blood tests for total bilirubin measure both unconjugated
and conjugated bilirubin, and are performed to evaluate jaundice. anemia, various liver diseases (including hepatitis), and impaired bile excretion.
Biochemistry:
The chemistry of living organisms and their vital processes.
Biological safety cabinet:
Enclosure in which one can work with relatively dangerous organisms without risk of acquiring or spreading infection caused by them. These cabinets, also called biosafety hoods, vary in design according to nature of agents to be worked with. The simpler ones maintain a negative pressure within the work area and a laminar air curtain, both of which operate to prevent escape of organisms from the interior of the hood. Air that is exhausted may be passed through a high-efficiency bacterial filter that will trap all microorganisms that are anticipated or may be passed through a furnace that will incinerate any organisms.
Bioluminescence:
Light generation by living organisms.
Biopsy:
Excision, for examination, of a small amount of tissue from a living body to determine the presence of disease. Also, the tissue excised is called a biopsy (e.g., lymph node biopsy).
Biotechnology:
Application of biological science information which can lead to the production of commercial products by biologic processes. These include recombinant DNA techniques, development of monoclonal antibodies, as well as gene splicing.
Biotin:
Small vitamin with two binding sites, one of which can bind covalently with nucleic acid leaving the other free to form a strong bond with the protein avidin, which in turn can be bound to enzymes. The system is used as a label for nucleic acid probe detection.
Biotype:
Biological or biochemical type of an organism. Organisms of the same biotype will display identical biological or biochemical characteristics. Certain key markers are used to define and recognize biotypes in tracing the spread of organisms in the environment and in epidemics or outbreaks.
Blackwater fever:
Condition in which the diagnostic symptom is passage of reddish or red-brown urine, which indicates massive intravascular hemolysis (Plasmodium falciparum).
Blastoconidium:
A spore formed by budding, as in yeasts.
Blastocyst:
A stage during early embryogenesis in mammals in which the embryo develops a fluid-filled interior and segregates into trophoblast and inner cell mass.
Blepharitis:
Inflammation of eyelids.
Blind loop:
A condition in which continuity of the bowel has been interrupted in such a way that a
segment of bowel receives material from higher in the bowel in the usual way but cannot empty normally because it ends in a blind sac. This leads to proliferation of microorganisms, especially anaerobes, in the blind loop of bowel and may produce profound pathophysiologic effects. There are other situations in which there may be bacterial overgrowth in a segment of the bowel by other mechanisms.
BOD:
Biochemical oxygen demand. The amount of oxygen required to metabolize dissolved organic material to carbon dioxide and water is referred to as the biological oxygen demand.
Boltzmann constant:
K = 1.38 x 10-16 erg/degree. This is the ratio of the universal gas constant to Avogadro's number. It is also used to relate temperatures (Kelvin) to energies (ergs or Joules) via E = (constant of order unity) kT.
Bordetella pertussis:
Gram negative, small coccobacilli; nonmotile, aerobic bacterium. Causes whopping cough.
Borborygmus:
The "growling" sounds produced by propulsion of gas through the intestinal tract. Due to a pattern of motility called the migrating motor complex.
Borrelia recurrentis:
Gram negative spirochete with axial filaments; anaerobic bacterium. Causes relapsing fever.
Bovine:
Pertaining to or derived from cattle.
Brain electrical activity mapping (BEAM):
A noninvasive diagnostic technique used to detect certain kinds of epilepsy, head injuries, dyslexia, brain tumors, dementia, and other brain diseases. This procedure utilizes a computer to convert data from brain electrical potentials into colored topographical maps of the brain which are then automatically compared with those of an appropriate control group to indicate the degree of deviation from the norm.
Branhamella catarrhalis:
Gram negative, flattened, nonmotile, aerobic cocci.
Breakpoint:
Level of an antibacterial drug achievable in serum; organisms inhibited by this level of drug are considered susceptible. In certain situations, clinicians strive to achieve serum or body fluid levels several times that of the breakpoint.
Bright field microscopy:
Optical microscopy, in which absorption to a great extent and diffraction to a minor extent give rise to the image, as opposed to phase contrast or interference methods of microscopy.
Bronchial lavage:
Similar to bronchial washings but this term implies instillation of a larger volume of
fluid before aspiration. Alveolar organisms may be present in the lavage.
Bronchial washings:
Fluid that may be aspirated from the bronchial tree during bronchoscopy.
Bronchitis:
Inflammation of mucous membranes of bronchi; often caused by infectious agents, viruses in particular.
Bronchoscopy:
The direct visualization of the trachea and bronchi through a rigid or flexible tube (bronchoscope). The procedure can be used to remove foreign bodies or to obtain a specimen for biopsy or other examination.
Brucella:
Gram negative coccobacilli or short rod-shaped bacteria; nonmotile, aerobic, oxidase positive. Facultatively intracellular. Cause of brucellosis (undulant fever, Bang's disease).
Brush border:
A term describing the microvillus-covered surface of small intestinal epithelial cells.
BSC:
Biological safety cabinet.
Bubo:
Inflammatory enlargement of lymph node, usually in the groin or axilla.
Bubonic plague:
A bacterial infection of the lymphatic system which causes swelling of the lymph nodes. A swollen lymph node is known as a bubo.
Buffer solution:
A solution with a constant, specified pH. The pH of the solution "resists" any change: addition of small amounts of solvent or even acid or base will not appreciably change the pH. This is called "buffer capacity." See Henderson-Hasselbalch equation.
Buffy coat:
Layer of white blood cells and platelets above red blood cell mass when blood is sedimented. A thin grayish white layer of white blood cells (leukocytes) and platelets covering the top of the packed red blood cells of a hematocrit.
Bullae:
Large blebs or blisters, filled with fluid, in or just beneath the epidermal layer of skin.
Bursitis:
Inflammation of a bursa, which is a small sac lined with synovial membrane and filled with fluid interposed between parts that move on each other.
2,3-Butanediol fermentation:
A fermentation in which the major waste products are 2,3-butanediol and carbon dioxide. Bacteria such as Enterobacter aerogenes carry out a 2,3-butanediol fermentation.
Butt:
Lower portion or medium in a tube that has the medium dispensed in such a way that the lower portion fills the tube entirely while the upper portion is distributed in the form of a slanted surface leaving an air space between the slant and the opposite wall of the tube.
Butyric acid bacteria:
Bacteria that release butyric acid when they ferment. An example is Clostridium.
Butyric acid-butanol fermentation:
A fermentation in which the major waste products are butyric acid, or butanol, and carbon dioxide. Bacteria such as Clostridium carry out a butyric acid-butanol fermentation.
Butyrous:
Butterlike consistency.
C and S (C&S):
Culture and sensitivity; bacterial culture and antibiotic sensitivity.
C terminus (C-terminal):
Synonym for carboxy terminus. The end of a polypeptide that carries a free carboxyl (COOH) group. The last amino acid in a peptide or protein is called the carboxy terminal or C-terminal amino acid.
Cabot's Rings:
A threadlike blue ring resembling a "figure 8", entirely contained within an abnormal red blood cell. Cabot's rings are rare morphologically, but may be found in megaloblastic
anemias, in homozygous thalassemia syndromes, and following splenectomy.
Calcitonin:
A protein hormone produced by cells in the thyroid gland which participates in control of calcium and phosphorus metabolism.
Calcium (Ca):
An alkaline element found in most tissues, it is an abundant mineral in the body. It is essential for maintenance of bones and teeth, normal heart, muscle, and nerve functions,
as well as normal blood clotting. Calcium levels can be measured in the blood or urine to help detect thyroid and parathyroid disorders, bone diseases, and certain cancers. It
may also point to the presence of kidney stones.
Calcium-sensing receptor:
A membrane protein that serves as a sensor for extracellular calcium concentration.
Calibrated loop:
Bacteriological loop that is carefully calibrated to deliver a specified volume of fluid providing that directions are followed carefully and the loop has not been damaged; used as a simple means of quantitating the number of organisms present, especially for urine culture.
Calorie (cal):
The amount of heat energy required to raise the temperature of 1 gram of water 1 degree C. This is equivalent to the amount of heat energy released by 1 gram of water when it cools by 1 degree C. A "Calorie" (capital C) is a term used especially by nutritionists and is the same as 1000 calories (1 kcal).
Calvin cycle:
A cyclic series of chemical reactions in which large amounts of carbon dioxide are fixed into organic molecules. The dark reactions of photosynthesis.
CAMP:
Lytic factor named after Christie, Atkins, and Munch-Peterson.
Campylobacter jejuni:
Gram negative, curved, rod-shaped, flagellated, microaerophilic, oxidase positive bacterium. Causes dysentery and enterocolitis.
Candida albicans:
A yeast belonging to the class Deuteromycetes that causes thrush of the mouth and yeast infections of the vagina.
Candle jar:
A jar with a lid providing a gas-tight seal in which a small white candle is placed and lit after the culture plates have been placed inside. The candle will burn only until the oxygen concentration has been lowered to the point where it will no longer support the flame. The atmosphere of such a jar has a lower oxygen content than room air and a carbon dioxide content of about 3%.
Canine:
Pertaining to or derived from dogs and their relatives.
Cannabinoids:
The psychoactive chemical substances found in marijuana (Cannabis sativa). The presence of cannabinoids in urine or blood indicates recent marijuana use or close contact with
it.
Cannula:
An artificial tube for insertion into a tube or cavity of the body.
CAP:
Chocolate agar plate. Also, College of American Pathologists.
Capacitation:
Changes in the sperm that prepare it for fertilization.
CAPD:
Chronic ambulatory peritoneal dialysis.
Capneic incubation:
Incubation under increased CO2 tension, as in a candle extinction jar (approximate 3% CO2).
Capnophilic:
Term used to describe microorganisms that prefer an incubation atmosphere with increased carbon dioxide concentration.
Caprine:
Pertaining to or derived from goats.
Capsid:
Protein layer or coat surrounding viral nucleic acid core.
Capsomere:
Protein subunits that serve as components of the viral capsid.
Capsule:
Gelatinous material surrounding bacterial cell wall. Usually of polysaccharide nature.
Carbamazepine:
A pain relieving and anticonvulsant drug often used to treat trigeminal neuralgia (pain along the route of the facial nerve) and epilepsy (a neurological disorder characterized
by convulsive seizures). Blood testing can determine carbamazepine levels in the body and aid in maintaining appropriate dosage.
Carbohydrate:
A group of organic compounds, including starches and sugars, that is a major source of body energy and is necessary for metabolism. Excessive intake is associated with tooth
decay and obesity. Its concentration can be assayed in serum and urine.
Carbonic anhydrase:
Enzymes that catalyze the hydration of carbon dioxide and the dehydration of bicarbonate. Critical for such processes as production of gastric acid.
Carbonyl carbon:
A functional group composed of a carbon with double bond to oxygen. This is the functional group of ketones and aldehydes. The C=O double bond is planar.
Carboxy terminus (carboxy terminal):
The end of a polypeptide that carries a free carboxyl (COOH) group. The last amino acid in a peptide or protein is called the carboxy terminal or C-terminal amino acid.
Carboxyl carbon:
The carboxylic acid functional group. A carbonyl carbon to which is also attached a hydroxyl group.
Carcinogen:
A physical or chemical agent that causes cancer.
Carcinoid syndrome:
Carcinoid syndrome is a constellation of symptoms associated with a serotonin-secreting neoplasm known as carcinoid tumor. These tumors may grow anywhere in the gastrointestinal tract (and in the lungs) with approximately 90% in the appendix. The remainder occur in the ileum, stomach, colon, or rectum. Symptoms include flushing, rapid pulse, facial swelling, swelling around the eyes, low blood pressure, abdominal pain, weight loss, and diarrhea. The diagnosis of carcinoid syndrome is made by the measurement of 5-hydroxy indole acetic acid (5-HIAA) in the urine. 5-HIAA is a breakdown (waste) product of serotonin. Sandostatin LAR Depot, marketed by Novartis, is administered as a single injection to effectively treat the carcinoid tumor and its symptoms for up to a month.
Carrier:
One who harbors a pathogenic organism but is not affected by it.
Casual Glucose Test:
A blood test done to determine the non-fasting plasma glucose concentration at any time. Levels of > 200 mg/dl plus classic signs and symptoms of diabetes including polydipsia, polyuria, polyphagia and weight loss are diagnostic for diabetes mellitus.
Catabolism:
The breakdown of nutrients or cellular material. See also Anabolism.
Catalase:
Bacterial enzyme that breaks down peroxides with liberation of free oxygen.
Catalyze:
To accelerate the rate of a chemical reaction by a substance that is not permanently affected in the process.
CAT scan (computer or computerized axial tomography):
See computed tomography.
Catecholamine:
A group of compounds which include dopamine, epinephrine and norepinephrine which are used to mediate signalling in the sympathetic nervous system. They are synthesized and secreted from sympathetic neurons and the adrenal medulla.
Catheter:
Flexible tubular (rubber or plastic) instrument used for withdrawing fluids from (or introducing fluids into) a body cavity or vessel (e.g., urinary bladder catheter).
Cation:
A positively charged ion.
Caulobacter:
Gram negative, aerobic, flagellated, rod-shaped or nonmotile, prosthecate bacterium.
CD4:
55-kd glycoproteins originally defined as differentiation antigens on T-lymphocytes, but also found on other cells including monocytes/macrophages. CD4 antigens are members of the immunoglobulin supergene family and are implicated as associative recognition elements in mhc (major histocompatibility complex) class II-restricted immune responses. On T-lymphocytes they define the helper/inducer subset. Cd4 antigens also serve as HIV receptors, binding directly to the envelope protein gp120 on HIV.
The protein structure on the surface of a human cell that allows HIV to attach, enter, and thus infect a cell. CD4 receptors are present on CD4 cells (helper T-cells), macrophages and dendritic cells, among others. Normally, CD4 acts as an accessory molecule, forming part of larger structures (such as the T-cell receptor) through which T-cells and other cells signal each other.
CD4:CD8 ratio:
The ratio of CD4 to CD8 cells. A common measure of immune system status that is around two in healthy individuals. The ratio of T-lymphocytes that express the CD4 antigen to those that express the CD8 antigen. This value is commonly assessed in the diagnosis and staging of diseases affecting the immune system including HIV infection.
CD4 lymphocyte count:
A count of the number of CD4-positive lymphocytes in the blood. Determination requires the use of a fluorescence-activated flow cytometer.
CD8:
Differentiation antigens found on thymocytes and on cytotoxic and suppressor T-lymphocytes. Cd8 antigens are members of the immunoglobulin supergene family and are associative recognition elements in mhc (major histocompatibility complex) class I-restricted interactions.
CD8 cell:
A critical subpopulation of regulatory T-lymphocytes involved in mhc class I-restricted interactions. They include both cytotoxic T-lymphocytes and suppressor T-lymphocytes. A type of T-lymphocyte which bears the CD8 molecular marker on its surface. Some CD8 cells recognize and kill cancerous cells and those infected by intracellular pathogens (some bacteria, viruses and mycoplasma). These cells are called cytotoxic T-lymphocytes.
CDC:
Centers for Disease Control.
Cell line:
A cell culture that has been passed (subcultured) in vitro.
Cell line, continuous:
Line of tissue cells that is maintained by serial culture of an established cell line.
Cell line, primary:
Line of tissue cells established by cutting up fresh tissue, often kidney, into tiny
pieces, trypsinizing, and putting in a flask with appropriate medium.
Cell wall:
A rigid layer of material outside the cytoplasmic membrane which protects the cell. The cell wall of most bacteria contains a layer of peptidoglycan. The gram positive bacteria have a wall that consists of peptidoglycan and teichoic acids, but most gram negative bacteria have a wall that consists of a peptidoglycan layer and an outer membrane containing proteins and lipopolysaccharide.
Cellular immunity:
Immunity mediated by thymus-derived lymphocytes (T-cells) and macrophages.
Cellulases:
A group of enzymes that hydrolyze cellulose. Vertebrate cells do not synthesize cellulases, but microbes in the digestive tract do, allowing herbivores to take advantage of cellulose as an energy source.
Cellulitis:
Inflammation of subcutaneous tissue.
Cellulose:
A structural polysaccharide of plants composed of linear chains of glucose. Present in the diet of man and many animals.
Centric fusion:
A type of translocation in which the centromeres of two acrocentric chromosomes fuse to generate one large metacentric chromosome.
Cephalosporium acremonium:
A fungus that produces the antibiotic cephalosporin C.
Cerebriform:
With brainlike folds.
Cervical:
Pertaining either to the neck or to the cervix of the uterus.
Ceseation necrosis:
Tissue death with loss of cell outlines and a cheeselike, amorphous appearance.
CF:
Complement fixation.
CFU:
Colony-forming unit (i.e., colony count).
Charcot-Leyden crystals:
Slender crystals shaped like a double pyramid with pointed ends, formed from the breakdown products of eosinophils and found in feces, sputum, and tissues: indicative of an immune response that may have parasitic or nonparasitic causes.
Chemiluminescent:
Exhibiting light as a result of a chemical reaction without the production of heat; emitted from some bacteria, fungi, and fireflies.
Chemiosmotic hypothesis:
The theory that proton gradients are created by the movement of electrons and protons through an electron transport system, and that this proton gradient provides energy for doing work (concentrating nutrients and moving flagella) or synthesizing ATP from ADP and inorganic phosphate.
Chemistry:
In clinical testing, refers to the solutes dissolved in the plasma such as uric acid, etc.
Chemoheterotroph:
An organism that derives its energy from various chemicals and its carbon from organic molecules other than carbon dioxide. Usually, the same chemicals supply both the energy and the carbon.
Chemolithotroph:
An organism that derives its energy from inorganic chemicals, such as ferrous iron, hydrogen sulfide, or ammonium.
Chemotaxis:
A response of motile cells or organisms in which the direction of movement is affected by the gradient of a diffusible substance. Differs from chemokinesis in that the gradient alters probability of motion in one direction only, rather than rate or frequency of random motion.
Chemotherapeutic:
Chemical agent used in the treatment of infections (e.g., sulfonamides), cancer, or other disease conditions.
Chimera (chimerism):
In genetics, an animal that has more than one genetically-distinct population of cells derived from more than one zygote. Derived experimentally by aggregation or mixing of multiple early embryos or naturally by such processes as exchange of blood between twin fetuses.
Chiral compound:
A molecule that has an asymmetric center and can be found in two non-superimposable mirror-image forms (enantiomers).
Chiral carbon:
A carbon which has 4 different groups attached to the carbon. This carbon is considered asymmetrical and will have a stereoisomer.
Chitin:
A homopolymer of N-acetyl-D-glucosamine, which is the major structural molecule in the cell walls of most classes of fungi and in the exoskeletons of insects and crustaceans.
Chlamydia psittaci:
Gram negative, spherical, nonmotile, ATP-requiring, intracellular bacterium. Causes lung infections in birds (ornithosis or psittacosis) and humans.
Chlamydia trachomatis:
The causative microorganism of one of the most prevalent sexually transmitted diseases, Chlamydia infection can lead to urethritis (inflammation of the urethra), pelvic inflammatory disease, ectopic pregnancy, and infertility. The infection may be asymptomatic, but patients may experience vaginal irritation or burning, discharge from penis or vagina, or pain. This microorganism is also the cause of serious eye infections. Causes trachoma, inclusion conjunctivitis, infant pneumonia, nonspecific urethritis, and lymphogranuloma venereum. At one time testing for Chlamydia was somewhat difficult; now, however, immunoassay can detect the antigens from swab specimens.
Chlamydospore
Thick-walled spore formed from a vegetative cell.
Chloride:
A compound in which one of the elements is chlorine (sodium chloride — table salt — is the most common example); found in the body in large amounts. It is an electrolyte, thus is involved in water balance and acid-base balance. (Electrolytes affect movement of substances throughout the body and are crucial for normal function and metabolism.) To help determine electrolyte, fluid, kidney, and adrenal gland disorders, chloride levels usually are measured in blood, but also may be tested for in urine and other fluids.
Cholecystokinin:
A peptide hormone secreted by cells in the small intestine that stimulates contraction of the gallbladder and secretion of digestive enzymes from the pancreas.
Cholelithiasis:
The presence or formation of gallstones.
Cholesterol:
A fat-soluble substance present in the blood and in animal fats that facilitates absorption and transport of fatty acids, and is necessary in hormone production. High levels of blood cholesterol have been linked to atherosclerosis and heart disease. See high and low density lipoprotein cholesterols.
Cholinesterase:
1. An enzyme that breaks down acetylcholine to stop its action. 2. Cholinesterase occurs principally in two forms, cholinesterase and pseudocholinesterase; several isoenzymes have been identified. Physiologically active cholinesterase is found in RBC and neurologic tissues and is responsible for depolarization of nerve tissues - necessary for the transmission of nerve impulses. Pseudocholinesterase is normally produced by the liver, and its serum enzymatic activity may be measured. Pseudocholinesterase measurement is useful in evaluating hepatotoxicity and neurotoxicity in agricultural workers who may have exposure to organophosphate insecticides such as Parathion, Sarin and tetraethyl pyrophosphate; which inactivate cholinesterase. Exposure to large amounts of these agents is potentially lethal if there is sufficient exposure to inactivate all nervous tissue cholinesterase.
There are several methods for measurement of serum pseudocholinesterase. The blood specimen is usually collected in a red-topped clot tube, allowed to clot, and the serum removed promptly after centrifugation. Serum specimens should be refrigerated or frozen for storage or shipment.
Chorionic villi sampling:
A means of testing the fetus for various abnormalities, such as congenital defects, blood disorders, and inborn errors of metabolism. This test can be performed during the
first trimester of pregnancy, but is easier to carry out between the 14th and 16th weeks of pregnancy.
Chromaffin cells:
The predominant cell type in the medulla of the adrenal gland; secretes the hormones epinephrine and norepinephrine.
Chromatin:
Strands of DNA. The more readily stainable portion of the cell nucleus, forming a network of nuclear fibrils within the achromatin of a cell. It is a deoxyribonucleic acid attached to a protein structure base and is the carrier of genes in inheritance.
Chromatography:
Techniques for separating molecules based on differential absorption and elution. Term for separation methods involving flow of a fluid carrier over a nonmobile absorbing phase.
Chromatophore:
Vesicular membranes found in the cytoplasm of the anaerobic photosynthetic bacteria.
Chromogen:
A colored substance or bacterial species whose colonial growth is pigmented (e.g., Flavobacterium species, yellow).
Chromogenic:
Giving rise to color, as chrornogenic substrates for colored products of biochemical reactions or chromogenic bacteria that produce pigmented colonies.
Chromophore:
The colored portion of a dye.
Chromoplast:
A colored organelle (plastid), such as a chromosome or a chromoplastid.
Chromosomes:
The 46 (in human beings) structures in the nuclei of cells on which the genes, which contain hereditary information, are arranged.
Chronic:
Persisting over a long period of time.
Chronic carrier:
Carrier; someone who has been infected by a pathogenic organism and has no symptoms of the illness, but has the ability to infect others.
Chronic hepatitis B:
Long-term infection with the hepatitis B virus. (Hepatitis B also has been called serum hepatitis.) Such infection may lead to liver cell destruction and cirrhosis.
Chronic myeloid leukemia (Chronic myelogenous leukemia) (CML):
A leukaemia which is initially slowly-progressing. It is characterised by the presence of large numbers of abnormal mature granulocytes, circulating in the blood. Synonym: Chronic granulocytic leukaemia.
Chylomicron:
A package of lipids synthesized in small intestinal epithelial cells and delivered into intestinal lymphatic vessels. Consists of triglycerides, cholesterol and lipoproteins.
Chymotrypsin:
A proteolytic enzyme produced by the pancreas that digests proteins into peptides.
CIE:
Counterimmunoelectrophoresis.
CIP:
An acronym for calf intestinal phosphatase, which is used in the laboratory to dephosphorylate DNA.
Cirrhosis:
A degenerative disease of the liver — the organ that helps eliminate toxic materials from the body — often caused by alcoholism, but also may result from certain forms of hepatitis. Cirrhosis is characterized by formation of fibrous tissue, nodules, and scarring, which interfere with liver cell function and blood circulation. Symptoms
include weakness, weight loss, fatigue, abdominal swelling due to fluid accumulation, and tenderness and enlargement of the liver. Tests for prolonged prothrombin time and decreased albumin are among those used to detect cirrhosis. See prothrombin and albumin.
Cistron:
A gene or region of DNA that codes for a single polypeptide.
Citric acid cycle, Krebs cycle, tricarboxylic acid cycle:
A cycle sequence of chemical reactions that produces carbon dioxide, reducing electrons, and ATP. The citric acid cycle also provides building blocks for the synthesis of cellular material.
Citrobacter freundii:
Gram negative, rod-shaped, flagellated, facultative anaerobic bacterium.
Clark electrode:
An amperometric sensor assembly used for the measurement of dissolved oxygen concentration in water or aqueous solutions. It is a two-electrode electrochemical cell with the working electrode (typically positioned at the end of a tubular structure) separated from the test solution by a thin membrane permeable to oxygen. The oxygen diffusing through the membrane is reduced at the electrode and the current produced is proportional to the concentration of the dissolved oxygen. Calibration is required.
Clavate:
Club-shaped.
Claviceps purpurea:
A fungus that belongs to the class Ascomycetes. Causes ergot of rye.
Clone:
Group of microorganisms of identical genetic makeup derived from a single common ancestor.
Clostridia:
Gram positive, rod-shaped, flagellated or nonmotile, endospore forming, anaerobic or microaerotolerant, generally catalase negative bacteria. Clostridium botulinum causes botulism.
Clostridium perfringens:
Causes intestinal infections, gas gangrene, and food poisoning.
Clostridium tetani:
Causes tetanus.
CMI:
Cell-mediated immunity.
CNS:
Central nervous system.
Coagglutination:
Agglutination of protein A-containing cells of Staphylococcus aureus coated with antibody molecules when exposed to corresponding antigen.
Cocaine:
A substance used as a local anesthetic, also used as a recreational inhalant, that can lead to psychological dependence with prolonged use. Its use can cause damage to mucous
membranes and cardiovascular disorders. Cocaine metabolites can be detected in urine and may indicate recent use of the drug.
Coenocytic:
The condition in which a cell contains many nuclei.
Coenzyme:
A small organic molecule that works with enzymes, carrying chemical groups to or away from chemical reactions. Coenzymes are required for enzyme activity. Many vitamins are used to make coenzymes.
Cofactor:
Generally, a metal ion that is required for enzyme activity.
Coccidioidomycosis:
Valley fever.
Coccidioides immitis:
The fungus that causes coccidioidomycosis.
Colicin:
A bacteriocin produced by coliform bacteria (and some enterics).
Colitis:
Inflammation of the mucosa of the colon.
Colligative properties:
Properties (freezing-point depression, osmotic pressure, boiling point elevation and vapour pressure depression) of solutions that vary according to how much solute is in the solution.
Colon:
1) A section of the large intestine. 2) Macroscopically visible growth of a microorganism on a solid culture medium.
Colonoscopy:
Visualization of the lining of the anus, rectum and colon through a rigid proctosigmoidoscope or a flexible fiber optic endoscope (types of viewing tubes). This procedure allows diagnosis of tumors and inflammatory diseases.
Colorectal cancer:
A malignant disease of the colon and/or rectum which often begins as a polyp. The first indication of colorectal cancer is usually hidden, or occult, blood in the stool. Symptoms may include changes in bowel habits (diarrhea, constipation) or in consistency or color of the stool. A stool specimen blood test is commonly performed to screen for colorectal
cancer.
Colorimetric:
Pertaining to measurement of concentration of a solution based on its absorption or transmission of light, or on the intensity of color in a liquid.
Combination testing:
A series of independent tests done on single specimens to arrive at a medical decision.
Commensal:
Microorganism living on or in a host but causing the host no harm.
Competitive-binding assay:
An analytic procedure in which an unlabeled and a labeled analyte compete for sites to bind to a specific protein.
Complement:
A group of serum proteins that destroy sensitized cells or bacteria. A group of serum proteins involved in immune reactions which have cytolytic and chemotactic properties.
Complementation:
In genetics, a situation in which two defective DNA molecules, together, supply a missing function.
Complement fixation test
Antigen-antibody test based on fixation of completnent in the presence of both elements and use of an indicator system to determine whether or not complement has been fixed.
Complete blood count (CBC):
The determination of and report of the blood cells in a definite volume of blood that includes separate counts for red and white blood cells; also known as a hemogram.
Complex medium:
A medium that contains an unknown mixture of many different nutrients. Generally, a rich medium that is used to grow fastidious (demanding) microorganisms. See Minimal medium.
Computer tomography (CT):
A radiographic scanning procedure to obtain cross-sectional images. The X-ray source rotates about the patient, generating X-rays which pass through the individual and are
monitored as they exit, by detectors that are linked to a computer. The computer constructs three-dimensional images for examination and analysis. CT has revolutionized the diagnosis of intracranial, intrathoracic, and intraabdominal tumors, as well as other space-occupying lesions. CAT scan (computer axial tomography), CTAT (computerized transaxial tomography), CRT (computerized reconstruction tomography), and DAT (digital axial tomography) are diagnostic radiographic tools that are now collectively called computed tomography.
Configuration (molecular):
The 3-dimensional arrangement of the atoms of a molecule that are defined by covalent bonds and bond angles. This implies it takes the breaking of a covalent bond to change the configuration.
Conformation:
The spatial arrangements of the atoms of a molecule.
Congenital:
Existing before or at birth. This term says nothing about cause and is not equivalent to "genetic".
Congestive heart failure:
A condition where there is ineffective pumping of the heart leading to an accumulation of fluid in the lungs. Typical symptoms include shortness of breath with exertion, difficulty breathing when lying flat and leg or ankle swelling. Causes include chronic hypertension, cardiomyopathy and myocardial infarction.
Conjugate:
An analyte or antibody which has been tagged with an enzyme tracer.
Conjugation:
1) A sequence of alternating double (or triple) and single bonds. E.g. C=C-C=C and C=C-C=O. Conjugation can also be relayed by the participation of lone pairs of electrons or vacant orbitals. 2) Passing genetic information between bacteria by transferring chromosomal material, often via pili. Transfer requires cell-to-cell contact.
Conjunctivitis:
Inflammation of the conjunctivae or membranes of the eye and eyelid.
Contact inhibition:
Cells of higher animals generally cease growing and proliferating when they touch one another.
Continuous cultures:
Cultures that are maintained in the exponential phase of growth for extended periods of time by continuously supplying the culture with fresh medium.
Convalescent serum:
Serum collected later in the course of an illness than the acute serum, usually at least 2 weeks after initial collection.
Coordinate bond:
The linkage of two atoms by a pair of electrons both electrons being provided by one of the atoms (the donor). Coordinate bonds are covalent bonds.
Core window:
The period during which a person infected by the hepatitis B virus may infect others, even though blood tests show neither hepatitis B surface antigen nor antibodies to hepatitis core antigen.
Cortical granules:
Lysosome-like granules in the mature ovum that participate in fertilization.
Corticosterone:
A steroid hormone similar to cortisol produced by the adrenal cortex that participates in control of blood glucose concentration as well as several other processes.
Corticotropin:
Another name for adrenocorticotropic hormone (ACTH) - a peptide hormone secreted from the anterior pituitary that stimulates secretion of glucocorticoids from the adrenal glands.
Corticotropin-releasing hormone:
A peptide hormone secreted by the hypothalamus that stimulates secretion of adrenocorticotropic hormone from the anterior pituitary gland.
Cortisol:
A steroid hormone produced by the adrenal cortex that participates in control of blood glucose concentration as well as several other processes.
Corynebacteria:
Gram positive, rod-shaped, nonmotile, aerobic or facultative anaerobic bacteria.
Corynebacterium diphtheriae:
Causes diphtheria.
Counterimmunoelectrophoresis (CIE):
Detection of antibody or antigen by precipitin reaction that occurs in solid-phase (gel or paper) system that uses electric current to carry reactants toward each other.
Covalent bond:
The linkage of two atoms by the sharing of two electrons.
Coxiella burnetii:
Gram negative, rod-shaped, nonmotile, spore forming, obligate intracellular bacterium. Causes Q-fever.
CPC:
Clinical pathologic conference.
CPE:
Cytopathogenic (cytopathic) effect; visual effect of virus infection on cell culture.
C-peptide:
C-peptide is a byproduct of normal insulin production by the beta cells in the pancreas. Normal values are 0.5 to 3.0 ng/ml. Normal levels indicate that the body is still producing its own insulin. Low levels indicate that the pancreas is producing little or no insulin. Elevations can be seen in cases of insulinomas and islet of Langerhans tumours.
C-reactive protein (CRP):
A protein that appears, usually within 24 hours, in the blood during the acute stage of inflammatory disorders such as rheumatic fever, or after a myocardial infarction (heart
attack). The serum level of CRP is a sensitive indicator and monitor of rheumatic activity.
Creatine kinase (CK):
An isoenzyme (an enzyme that appears in multiple forms) found in high concentrations in heart and skeletal muscles, and, in smaller amounts, in brain tissue. Each form of CK
is predominant in specific tissues. Determining blood levels of the isoenzyme will aid in detection of myocardial infarction and muscle diseases such as muscular dystrophy.
Creatinine:
Found in muscle and blood and excreted in urine, creatinine is the end product of muscle (creatine) metabolism. By ascertaining levels of creatinine in blood or urine or in both, presence or severity of kidney malfunction can be indicated.
Cretinism:
A syndrome of growth and mental retardation in young children due to congenital deficiency in thyroid hormones.
Creutzfeldt-Jakob Disease:
Creutzfeldt-Jakob Disease is a neurological illness believed to be caused by a prion, a newly identified type of disease-causing agent. It is different from a virus in that there is no immune response to infection, and that there is a very long time between infection and onset of symptoms. However, like viruses, it must invade living cells to cause damage and to multiply.
Creutzfeldt-Jakob Disease tends to strike the elderly. Most individuals who have become ill with Creutzfeldt-Jakob Disease in the United States have been between 65 and 80 years of age. An individual with Creutzfeldt-Jakob Disease has slowly progressing confusion, difficulty with coordination, loss of memory and thinking skills. All of this occurs over a period of 3 to 12 months and ends in death. There is no treatment for Creutzfeldt-Jakob Disease other than supportive care.
It is not known how most cases of Creutzfeldt-Jakob Disease were transmitted. Creutzfeldt-Jakob Disease does not appear to be transmitted from person-to-person while the infected person is alive. It is known that some types of surgery, such as corneal transplants and tissue grafts taken from individuals who died of Creutzfeldt-Jakob Disease occasionally have transmitted Creutzfeldt-Jakob Disease. Precautions are now in place to ensure that this does not occur. Organ transplants are not taken from anyone who has died or is suspected to have died from Creutzfeldt-Jakob Disease.
Creutzfeldt-Jakob Disease is diagnosed primarily by clinical symptoms and an EEG (a test which measures electrical activity in the brain). A CT scan (a computer generated image of the brain) showing wasting of the brain may also be helpful in diagnosis.
Cross-reactivity:
The ability of an antibody to react with or bind an antigen that did not stimulate its production.
Croup:
Inflammation of upper airways (larynx, trachea) with respiratory obstruction, often caused by virus infections in children.
Cryptococcus neoformans:
A fungus in the class Deuteromycetes or Fungi Imperfecti. Causes cryptococcosis, a mild pneumonia, meningitis, or systemic infection. Fillobasidiella neoformans is the perfect state (a Basidiomycete) of C. neoformans.
CSF:
Cerebrospinal fluid.
Culdocentesis:
Aspiration of fluid from the cul-de-sac by puncture of the vaginal vault.
Culex sp.:
Mosquito vectors for encephalitis (EEE, WEE, St. Louis).
Culture:
(1) A procedure in which material or microorganisms from varying sources are cultivated in culture media for diagnostic or treatment purposes. Cultures also are performed to detect whether viable microorganisms are present, and, therefore, whether an infection exists. Growth and identification of the organisms present allow suitable selection of treatment (antibiotics). (2) Population of microorganisms growing in an artificial medium. (3) The cultivation product or the material to be cultivated also may be referred to as a culture.
Cushing's syndrome:
An increased concentration of glucocorticoid hormone (ACTH) in the bloodstream that is being produced by an adrenal gland tumour (adenoma). Ectopic Cushing syndrome refers to the production of ACTH in a location other than the pituitary gland or adrenal gland. Examples of ectopic sites include thymoma, medullary carcinoma of the thyroid, pheochromocytoma, islet cell tumours of the pancreas and oat cell carcinoma of the lung. Symptoms include weight gain, central obesity, moon face, weakness, fatigue, backache, headache, increased thirst, increased urination, impotence, mental status changes and muscle atrophy. Treatment varies with cause. If an ACTH secreting tumour is involved, it must be removed surgically.
Cyanobacteria:
Photosynthetic bacteria that release molecular oxygen as a consequence of their photosynthesis. Also known as blue-green bacteria, blue-green algae.
Cyclic AMP (cAMP):
3',5'-cyclic adenosine monophosphate. The phosphate group is connected to the 3' and 5' carbons of the ribose sugar, thus creating a cyclic structure; a nucleotide derived from ATP thorough the action of adenylyl cyclase. Used as a second messenger by a number of hormones.
CYE:
Charcoal yeast extract (agar plate).
Cystic duct:
A section of the biliary system that conveys bile into the gall bladder.
Cystitis:
Inflammation of urinary bladder, most often caused by bacterial infection.
Cytochrome:
Complex metal-containing porphyrin-protein molecules that are readily reduced and oxidized. They are important components of electron transport systems.
Cytogenetics:
The study of normal and abnormal chromosomes.
Cytology:
The study of cells, their origin, structure and function. In medicine, often used to describe the study and identification of cells from clinical specimens, particularly fluid specimens.
Cytomegalovirus (CMV):
One of a group of species-specific herpes viruses.
Cytopathic effect (CPE):
Alteration in cell morphology resulting from viral, bacterial, fungal, or protozoan
infection of a cell culture monolayer.
Cytophaga:
Gram negative, rod-shaped, gliding, facultative anaerobic or aerobic bacteria.
Cytoplasmic membrane:
See Plasma membrane.
Cytotoxin:
Toxin that produces cytopathic effects in vivo or in a tissue culture system.
Dalton (Da):
A unit of molecular mass approximately equal to that of a hydrogen atom or 1.66 x 10-24 grams. Alternatively, there is approximately 1 mole of daltons per gram.
D-value (decimal reduction time):
The time that it takes for an antimicrobial agent to reduce a population to 10 percent of its original size at a specified temperature.
Dark field illumination:
Any method of microscopic illumination which illuminates the specimen but does not admit light directly to the objective. It may be by substage (dark field) condensers, by stagespot lighting, by special condensers fitted around special objectives for reflected illumination or by the slit ultramicroscope.
Debridement:
Surgical or other removal of nonviable tissue.
Dcontamination:
Process of rendering an object or area safe for unprotected people by removing or making harmless biological or chemical agents.
Decubitus ulcer:
A craterlike defect in skin and subcutaneous tissue caused by prolonged pressure on
the area. This occurs primarily over bony prominences of the lower back and hips in individuals who are unable to care for themselves well and unable to roll or move periodically; also known as pressure sore or bedsore.
Definitive host:
Host in which the sexual reproduction of a parasite occurs.
Dihydrotestosterone (DHT):
Dihydrotestosterone is a metabolite of testosterone and is believed to be the hormonally active form of testosterone in males. The majority of dihydrotestosterone is produced in androgen target glands like the prostate, with small amounts produced by the testes, skin and submallixary glands.
Deionized Water:
Water that has had the ions removed. Used in laboratories for making reagents.
Denaturation:
(1) Reversible or irreversible loss of function in proteins and nucleic acids resulting from loss of higher order secondary, tertiary or quaternary structure) produced by nonphysiological conditions of pH, temperature, salt or organic solvents. (2) Alteration of the normal shape or activity of a molecule.
Denitrifying bacteria:
Bacteria that convert nitrate to nitrite or to nitrogen gas by anaerobic respiration.
Dental caries:
Areas of tooth decay.
Deoxyribonucleic acid (DNA):
The carrier of genetic information, it is found on chromosomes in the cell nucleus. It is a complex protein composed of different subunits that contain nitrogen, a complex
sugar, phosphoric acid, and other constituents arranged in specific sequences. Genes consist of DNA.
Dermatomycosis:
A fungal skin infection.
Dermatophyte:
A fungus parasitic on skin, hair, or nails. Dermatophytes digest keratin.
Desquamation:
Shedding or scaling of skin or mucous membrane.
Desulfotomaculum:
Gram positive, rod-shaped, flagellated, endospore forming, anaerobic, sulfate- and sulfite-reducing bacteria that produce hydrogen sulfide.
Desulfovibrio:
Gram negative, curved, flagellated, anaerobic, sulfate- and sulfite-reducing bacterium that produces hydrogen sulfide.
Deuteromycetes:
A class of fungi also known as the Fungi Imperfecti. These fungi have no known sexual stage; they produce asexual spores called conidia. Examples are Penicillium and Aspergillus.
Dexamethasone suppression test (DTST):
A procedure to evaluate the neuroregulatory mechanism of cortisol secretion into blood plasma. following the administration of dexamethasone (a synthetic steroid which normally
causes decreased secretion). Cortisol levels may be determined by various immunoassay methods. DTST is often done to help identify a depression disease, as patients may not suppress cortisol secretion after dexamethasone administration.
Dextran:
Polysaccharides in which most of the glucose is held together by alpha (1,6) linkages, whereas alpha (1,2), alpha (1,3), or alpha (1,4) linkages are responsible for the branching. The dextrans form viscous, slimy solutions. Dextran solutions have been used as plasma volume expanders in cases of shock.
Dextrin:
A branched polysaccharide of glucose which remains after limited amylase hydrolysis of starch or glycogen. Most of the glucose is held together by alpha (1,4) linkages, whereas alpha (1,6) linkages are responsible for the branching.
Dextrose:
Glucose.
Diabetes insipidus:
A disease associated with inadequate production of or response to antidiuretic hormone. A major clinical sign is production of very large volumes of urine.
Diabetes Mellitus:
A chronic syndrome of impaired carbohydrate, protein, and fat metabolism owing to insufficient secretion of insulin or to target tissue insulin resistance, characterized by polydipsia, polyuria and polyphagia.
Diabetes Control and Complications Trial:
This study of 1,441 type 1 patients with diabetes over a period of nine years was completed and reported in September 1993. It conclusively demonstrated that glycemic control is a major deterrent to the development and progression of diabetic microvascular and neuropathic disease.
Diacetyl:
A compound relased by certain bacteria and yeast which gives an off-flavor to beer and a buttery aroma and taste to butter.
Dialysis:
The removal of low molecular weight ions and molecules by diffusion across a membrane.
Diastereomers:
Stereoisomers which are not mirror images of each other.
Diatomaceous earth:
Earth consisting of diatom cell walls.
Diauxic:
The two-step growth curve that results when a population of organisms metabolizes one carbon source completely before beginning to metabolize another.
DIC:
Disseminated intravascular coagulation.
Dichotomous:
Branching in two directions.
Dictyostelium:
A slime mold that produces a pseudoplasmodium.
Didinium:
A large ciliated protozoan.
Differential:
Microscopic examination of a stained blood smear to: 1.Determine the relative percentages of each type of white blood cell; 2.Verify by estimate, the automated white cell, red cell, and platelet counts; and 3. Examine the morphology of red cells, white cells, and platelets.
Diffusion:
The net movement of a solute from a region of high concentration to a region of low concentration. In passive diffusion across a membrane, the rate of diffusion is directly proportional to the concentration of the solute; in facilitated diffusion across a membrane, the rate of diffusion at low solute concentrations is dependent upon the concentration of the solute, but at high solute concentrations the rate of diffusion is dependent upon the mechanisms that are aiding the diffusion (e.g., concentration of carrier molecules on membrane).
Digital rectal examination:
A common screening procedure for prostate cancer, whereby a physician inserts a gloved, lubricated finger into the rectum, in order to feel the size and shape of the prostate
through the rectal wall.
Digoxin:
A drug commonly used to treat congestive heart failure and certain heartbeat irregularities that is obtained from leaves of the Foxglove (digitalis) plant. Digoxin overdose can be toxic. The level of the drug can be obtained from blood testing, which can aid in setting appropriate dose amounts.
Dikaryon:
A cell that contains two different types of nuclei.
Diluent:
Fluid used to dilute a substance.
Dilution:
To mix sample with water, saline, buffer or other diluent to decrease the concentration of a solute or analyte.
Dimer:
A protein complex composed of two proteins. In a homodimer, the two proteins are identical, whereas a heterodimer contains two different proteins.
Dimorphic fungi:
Fungi that have two different morphologies that change, depending upon the environmental conditions. For example, the formation of a mycelium at room temperature and yeastlike structures at 35°C. Fungi with both a mold phase and a yeast phase.
Diploid:
Containing two sets of homologous chromosomes and thus two copies of each gene.
Direct fluorescent antibody test (DFA):
A test that uses a fluorescent antibody to directly detect an antigen.
Direct wet mount:
A preparation from clinical material suspended in sterile saline or other liquid medium on a glass slide and covered with a coverslip; used for microscopic examination to detect
microorganisms in clinical material and, in particular, to detect motility directly.
Disinfectant:
Agent that destroys or inhibits microorganisms that cause disease.
Dissimilatory sulfate reduction:
The conversion of cellular sulfate to environmental hydrogen sulfide.
Dissociation:
Dissociation is the process whereby a molecule is split into simpler fragments which may be smaller molecules, atoms, free radicals or ions.
Dissociation constant:
The dissociation constant is the measure of the extent of dissociation, measured by the dissociation constant K. For the process AB = A + B, K = ([A][B])/[AB].
Distal:
Remote; further from a point of reference; away from the attached end or origin or a structure (opposite of proximal). The hand is distal to the elbow on the arm.
Diuresis:
Increased production of urine. A diuretic is an agent that promotes diuresis.
DNA:
Deoxyribonucleic acid, the nucleoprotein molecule that contains the genetic code for most living things.
DNA Polymerase:
A group of enzymes mainly involved in copying a single-stranded DNA molecule to make its complementary strand. Eukaryotic DNA polymerases participate in chromosomal replication, repair, crossing-over and mitochondrial replication. To initiate replication, DNA polymerases require a priming RNA molecule. They extend the DNA using deoxyribonucleotide triphosphates (dNTP) as substrates and releasing pyrophosphates. The dNMPs are added to the 3' OH end of the growing strand (thus, DNA replication proceeds from 5' to 3' end).
DNA testing:
The technology of using DNA to differentiate one individual from another, often used for forensic evidence and parentage determination.
DNase:
Deoxyribonuclease, an enzyme that depolymerizes DNA.
Döhle Bodies:
Single or multiple, round or oval, blue (with Romanowsky Stain) cytoplasmic inclusions which contain strands of endoplasmic reticulum that have aggregated. They are seen in neutrophils, usually associated with toxicity.
Double helix:
The double-stranded DNA molecule.
Doubling time:
The time that it takes a population to double its size. Same as generation time.
DRGs:
Diagnosis related groups; system introduced to control rising medical costs under which hospitals are reimbursed for costs of caring for patients based on the primary diagnoses of the patients and what is considered to be a fair dollar value for treatment of usual patients with those diagnoses.
Droplet nucleus:
A tiny aerosolized particle that, because of its lack of mass, may stay suspended in air for extended periods of time.
Duodenum:
The first section of the small intestine.
Durham tube:
Small tube placed in an inverted position below the surface of a growth-supportive broth and filled completely with the broth solution. Gas produced by the organism displaces the broth in the Durham tube, and the resulting gas bubble is visual evidence of gas production.
Dx:
Symbolic abbreviation for diagnosis
Dysentery:
Clinical syndrome resulting from an inflammation of the large intestine. It is characterized by diarrhea with blood and mucus, tenesmus, fever, and malaise (e.g., bacillary dysentery).
Dysgonic:
Growing poorly (bacterial cultures).
Dyspepsia:
Chronic or recurrent pain or discomfort centered in the upper abdomen. Usually the result of gastric or esophageal disease.
Echocardiography:
A noninvasive procedure that utilizes reflected ultrasonic waves (echoes) directed to the heart that are converted and recorded as an image showing internal structures. It
is used to study the heart structure and motion in diagnosis of pathologic cardiovascular changes.
Eclampsia:
Convulsions and coma occurring in a pregnant or puerperal woman, associated with preeclampsia, i.e., with hypertension, edema, and/or proteinuria.
Eclipse period:
The time from the initiation of a virus infection until new infectious virus particles appear within the host cell. See Latent period.
Ectoparasite:
Organism that lives on or within skin.
Ectopic:
Located away from the normal position. Synthesis in the brain of a protein that is normally produced only in skin would be called ectopic production. Ectopia cordis is a congenital defect in which the heart is found outside of its normal position in the thorax.
Ectothrix:
Outside of hair shafts.
Edema:
Excessive accumulation of fluid in tissue spaces.
Efferent:
Conveying or carrying away from a center (opposite of afferent). Example: an efferent neuron carries information from the central nervous system to the periphery.
Efficacy:
Capacity for producing the desired result or effect. A drug that cures a particular disease has efficacy for treating that disease and is efficacious.
Effusion:
Fluid escaping into a body space or tissue (e.g., pleural effusion).
Eh:
Oxidation-reduction potential.
Eicosanoid:
A hormone derivative of the 20 carbon fatty acid, arachadonic acid; eg., Prostaglandins, Prostacyclins, Leukotrienes, Thromboxanes.
Ejaculation:
A sudden release of fluid, especially of semen, from the body.
Electroblot tests:
A number of diagnostic transfer methods (blots) which allow shifting of proteins from gels to cellulose, where they are isolated and imobilized and can be detected and identified by a variety of techniques. The cellulose soaks up proteins like a blotter.
Electrocardiogram (ECG or EKG):
A graphic recording that shows electrical activity generated by the heart muscle. It is used to help diagnose specific cardiac anomalies, such as disturbances of heart rhythm
and conduction.
Electrocardiograph:
The instrument used to detect and record the electrical activity of the heart muscle. It produces the ECG.
Electrochemical cell:
A device that converts chemical energy into electrical energy or vice versa when a chemical reaction is occurring in the cell. Typically, it consists of two metal electrodes immersed into an aqueous solution (electrolyte) with electrode reactions occurring at the electrode-solution surfaces. See also galvanic cell and electrolytic cell. It consist of two electronically conducting phases (e.g., solid or liquid metals, semiconductors, etc) connected by an ionically conducting phase (e.g. aqueous or non-aqueous solution, molten salt, ionically conducting solid). As an electrical current passes, it must change from electronic current to ionic current and back to electronic current. These changes of conduction mode are always accompanied by oxidation/reduction reactions. An essential feature of the electrochemical cell is that the simultaneously occurring oxidation-reduction reactions are spatially separated. E.g., in a spontaneous "chemical reaction" during the oxidation of hydrogen by oxygen to water, electrons are passed directly from the hydrogen to the oxygen. In contrast, in the spontaneous electrochemical reaction in a galvanic cell the hydrogen is oxidized at the anode by transferring electrons to the anode and the oxygen is reduced at the cathode by accepting electrons from the cathode. The ions produced in the electrode reactions, in this case positive hydrogen ions and the negative hydroxyl (OH-) ions, will recombine in the solution to form the final product of the reaction: water. During this process the electrons are conducted from the anode to the cathode through an outside electrical circuit where the electrical current can drive a motor, light a light bulb, etc. The reaction can also be reversed, water can be decomposed into hydrogen and oxygen by the application of electrical power in an electrolytic cell.
Electroencephalogram (EEG):
A chart that provides a record of the electrical activity of the brain. which is derived from electrodes placed on the scalp. The instrument used is an electroencephalograph. An electroencephalogram is useful in diagnosis of seizure disorders and tumor detection.
Electrolyte:
A solution of a compound that dissociates into ions and can conduct electricity. Electrolytes affect the movement of substances between body fluids and tissues, and are crucial for normal function and metabolism. In many illnesses, monitoring proper balance among the most important ones is vital. Calcium and potassium, for example, are necessary for cardiac and skeletal contractions and relaxations, and sodium is essential for fluid balance. An electrolyte imbalance can be caused by disease conditions or medications. Electrolytes also are used as electrical conductors in electrophoretic test methods.
Electron microscope:
An electron-optical instrument that utilizes a beam of electrons, rather than light, to focus on cell surfaces of a very thin specimen to produce an enlarged image on a fluorescent screen or photographic plate. Because resolution (the ability to distinguish adjacent objects as separate) is better and magnification 1,000 times that of an optical light microscope is possible, electron microscopy can help determine the nature of tumors and of kidney disease. See scanning electron microscope.
Electronic fetal monitoring:
The use of external and internal devices that record the fetal heart rate. An externally applied ultrasound transducer converts sound energy into electrical energy which is recorded on a graph. After rupture of the membranes, an electrode can be applied via the maternal vagina to the fetal scalp to obtain a fetal ECG. The maternal uterine contractions also are recorded on the graph so that they can be related to the fetal heart rate, to indicate fetal distress.
Electrophile:
An electrophile is an atom, molecule or ion able to accept an electron pair.
Electrophilic substitution:
An overall reaction in which an electrophile binds to a substrate with the expulsion of another electrophile. An example is the electrophilic substitution of a proton by another electrophile, such as a nitronium ion, on an aromatic substrate such as benzene.
Electrophoresis:
Movement of charged particles in an electrical field, a technique used to separate materials in a substance by placing a sample in a buffer solution through which an electrical current then is passed. Extent of migration and separation of components depends on molecular weight and electrical charge of the particles. This method often is used to determine the proportions of various proteins in serum.
Electrovalent bond:
Ionic bonding by electrostatic attraction.
Elek test:
Antitoxin which has been impregnated in a strip of sterile filter paper is placed on the surface of the agar medium after a heavy inoculum is streaked at right angles to the position of the paper strip, and allowed to incubate for 24 hours. If the organism is toxigenic, a visible Ag-Ab precipitin line will form.
Elementary body:
The infectious stage of Chlamydia or a cellular inclusion body of a viral disease. Intracellular chlamydia cells with an atypical structure which are the infectious form of the bacterium. Elementary bodies are sporelike structures that do not multiply, do not transport ATP, and do not carry out protein synthesis. The number of ribosomes in the elementary bodies is greatly reduced as compared with the number in the reticular bodies (initial bodies). The outer membrane proteins of elementary bodies are linked by disulfide bonds, making the cells rigid. See Reticular bodies (initial bodies).
Elephantiasis:
Condition caused by inflammation and obstruction of the lymphatic system, resulting in hypertrophy and thickening of the surrounding tissues, usually involving the extremities and external genitalia (often as a result of filariasis).
ELISA:
Enzyme-linked immunosorbent assay.
Elution:
Process of extraction by means of a solvent.
EMB:
Eosin-methylene blue (agar plate).
Embden-Meyerhof pathway:
A specific sequence of chemical reactions that converts glucose to pyruvic acid. Same as glycolysis.
Emetic:
Substance which induces vomiting.
Empyema:
Accumulation of pus in a body cavity, particularly empyema of the thorax or chest.
Enantiomers:
Two stereoisomers which are mirror images of each other.
Encephalitis:
Inflammation of the brain.
Endergonic reaction:
A reaction that absorbs heat or energy from its environment. See Exergonic reaction.
Endocarditis:
A serious infection of the endothelium of the heart, usually involving leaflets of the heart valves where destruction of valves or distortion of them by formation of vegetations may lead to serious physiological disturbances and death; also, an inflammation of the endocardial surface (much less common).
Endocervix:
Mucous membrane of the cervical canal.
Endocrine:
The activity of a hormone or growth factors that circulates in blood, and binds to and affect cells distant from the source of secretion.
Endocrinology:
The study of the endocrine system: hormones, their receptors and the intracellular signalling pathways they invoke.
Endogenous:
Developing from within the body.
Endonuclease:
An enzyme that cuts within a DNA or RNA molecule. A nuclease which cuts a nucleic acid molecule by cleaving the phosphodiester bonds between two internal residues. Best known examples are restriction endonucleases. See Exonuclease.
Endoparasite:
Parasite that lives within the body.
Endophthalmitis:
Inflammation of internal tissues of eye; may rapidly destroy the eye.
Endosymbiont:
An organism that lives within another in a symbiotic relationship.
Endothelial cells (endothelium):
Flat (squamous) cells that line the heart, blood vessels and lymphatic vessels. The single layer of these lining cells is called endothelium.
Endothrix:
Within the hair shaft.
Endotoxin:
Substance containing lipopolysaccharide complexes found in the cell wall of bacteria, principally gram-negative bacteria; felt to play an important role in many of the complications of sepsis such as shock, DIC, and thrombocytopenia.
Engineering controls:
Physical devices, such as needle resheathing holders and sharps containers, that help to remove biohazardous material from the workplace.
Enrichment:
Cultural selection for an organism, so that its relative abundance increases.
Entamoeba coli:
A nonpathogenic ameba that colonizes the intestines of about 30% of the human population.
Entamoeba histolytica:
An ameba that causes dysentery.
Enteric:
Referring to the intestine
Enteric bacteria:
Bacteria that normally live in the intestines.
Enteric fever:
Typhoid fever; paratyphoid fever.
Enterobacter aerogenes:
Gram negative, rod-shaped, flagellated, facultatively anaerobic bacterium. Sometimes involved in urinary tract infections.
Enterochromafin-like (ECL) cells:
A type of endocrine epithelial cell found in mucosa of the gastrointestinal tract; secretes histamine.
Enterococcus:
Spherical bacteria that live in the intestines, such as Streptococcus faecalis.
Enterocyte:
An epithelial cell in the lining of the intestine.
Enteroglucagon:
A term for peptides derived from proglucagon that are produced in the intestine.
Enteroinvasive:
Capable of invading the mucosal surface and sometimes the deeper tissues of the bowel.
Enteropathogenic Escherichia coli (EPEC):
Specific serotypes of E. coli isolated from feces of patients with diarrhea, usually associated with nursery epidemics.
Enterotoxigenic:
Producing an enterotoxin (e.g., enterotoxigenic Escherichia coli).
Enterotoxin:
Toxin affecting the cells of the intestinal mucosa.
Enterovirus:
Viruses that live or are commonly found in the intestines, such as the polioviruses and hepatitis A virus.
Enzyme:
A protein produced by cells that influences the speed of a specific chemical reaction without being used up or permanently changed in the process. Enzymes are catalysts. A biological catalyst, most often a protein, although ribozymes are RNA molecules.
Enzyme immunoassay (EIA):
An assay that uses an enzyme-bound antibody to detect antigen. The enzyme catalyzes a color reaction when exposed to substrate.
Enzyme-linked fluorescent assay (ELFA):
Similar to EIA except the enzyme catalyzes a fluorescence, not a color reaction.
Enzyme-linked immunosorbent assay (ELISA):
See assay.
Eosinophil:
A mature type of granulocyte (of the myeloid series) in which cytoplasmic granules are large, round, and refractile and stain orange or red with Wright's stain. Composes 0 to 4 percent of the normal WBC differential count. Phagocytic, particularly associated with helminth infections and with hypersensitivity (allergy).
EPEC:
Enteropathogenic Escherichia coli.
Epidemiology:
The study of the occurrence and distribution of disease and factors that control the presence, absence and transmission of disease.
Epidermophyton:
A fungus that causes skin infections, such as jock itch (ringworm of the groin) and athlete's foot (ringworm of the foot).
Epididymitis:
Inflammation of the epididymis characterized by fever and pain on one side of the scrotum; seen as a complication of prostatitis and cystitis.
Epiglottitis:
Inflammation of the epiglottis, a structure that prevents aspirating swallowed food and
fluids into the tracheobronchial tree; a serious infection because the swollen epiglottis may block the airway.
Epimerization:
A process in which the configuration about one chiral center of a compound, containing more than one chiral atom, is inverted to give the opposite configuration. The term epimers is often used to describe two related compounds which differ only in the configuration about one chiral atom.
Epinephrine:
A catecholamine hormone secreted from the adrenal medulla in response to various stressors.
Episome:
A plasmid that is able to integrate into the host's chromosomes.
Epithelium:
Tissue composed of contiguous, flat cells that forms the epidermis and lines hollow organs and all passages of the respiratory, digestive, and genitourinary systems.
Epizootic:
Disease that affects a large number of animals.
Equilibrium constant:
according to the law of mass action, for any reversible chemical reaction: aA + bB = cC + dD, the equilibrium constant (K) is defined as: K = ([C]c[D]d)/([A]a[B]b)
Equine:
Pertaining to or derived from horses and their relatives.
Ergot:
A fungus that grows on wheat and rye. See Claviceps purpurea.
Eructation:
Belching or elimination of gases from the proximal digestive tract.
Erysipelas:
An acute cellulitis caused by group A streptococci.
Erwinia amylovora:
Gram negative, rod-shaped, flagellated, facultatively anaerobic, oxidase negative bacterium.
Erythema:
Redness of the skin from various causes.
Erythema migrans:
Characteristic radial skin lesion of Lyme disease.
Erythrasma:
A minor, superficial skin infection caused by Corynebacterium minutissimium.
Erythrocyte (RBC):
A red blood cell.
Erythrocytic cycle:
Developmental cycle of malarial parasites within red blood cells.
Eschar:
A dry scar, particularly one related to a burn.
Escherichia coli:
Gram negative, rod-shaped, flagellated, facultatively anaerobic bacterium commonly found in the intestines.
Esophagus:
A section of the digestive tract between the mouth and stomach.
Ester:
The product of an organic acid and an alcohol. A molecule which contains a covalent bond between a carbonyl carbon and a hydroxyl oxygen.
Estrogen:
A female sex hormone.
ETEC:
Enterotoxigenic Escherichia coli. Strains of E. coli that produce a choleralike toxin; have been implicated as causes of diarrhea.
Ethanol:
Ethyl alcohol, the type used in alcoholic beverages, medicines, and food products. Blood levels of ethanol can be ascertained by tests that indicate the degree of intoxication. Alcohol affects brain function (central nervous system depressant) and may produce chronic illness in susceptible individuals.
Ethanol fermentation:
A fermentation in which the major waste products are carbon dioxide and ethanol.
Ether:
The product of a reaction between two alcohols which links two alkyl and/or aryl groups through the oxygen of a hydroxyl funtional group. A molecule that contains covalent bonds from oxygen to two different carbons, i.e., R-CH2-O-CH2-R'.
Etiology:
Cause or causative agent.
Eubacteria:
Classical bacteria that have peptidoglycan in their cell walls, lipids with unbranched fatty acids connected by ester bonds in their cell membranes, and distinctive rRNAs, tRNAs, and RNA polymerases. The mycoplasmas, which lack a cell wall, and the chlamydia, which lack peptidoglycan in their cell walls, are considered eubacteria but the cyanobacteria are not. The archaebacteria lack peptidoglycan in their cell walls, have lipids with branched hydrocarbon chains connected by ether bonds, and have distinctive rRNAs, tRNAs, and RNA polymerases are not considered to be eubacteria either.
Eugenics:
The idea of improving the quality of human species by selective breeding. Encouraging breeding of those with supposedly good genes is positive eugenics, whereas discouraging those with genes for undesirable traits is negative eugenics.
Eugonic:
Growing luxuriantly (bacterial cultures).
Eukaryotic:
Organisms with a true nucleus, in contrast to bacteria and viruses. A cell that has one or more nuclei and generally contains organelles and structures such as mitochondria, chloroplasts, Golgi bodies, endoplasmic reticulum, and vacuoles.
Euploid (euploidy):
Having the normal diploid number of chromosomes, as opposed to aneuploidy.
Euthyroidism:
A normal thyroid hormone status most precisely defined by a normal TSH level.
Eutrophication:
A massive growth of algae in lakes and other bodies of water, which leads to a decrease in dissolved oxygen and a decrease in animal life in the water. Eutrophication is due to an excess of nutrients from erosion or sewage (eg., phosphate polution).
Exanthem:
Skin eruption as a symptom of an acute disease, usually viral.
Exergonic reaction:
A reaction that gives off heat or energy. See Endergonic reaction.
Exoantigen test:
In vitro immunodiffusion test method for identifying fungal hyphae as Histoplasma, Biastomyces, or Coccidioides.
Exoenzyme:
Enzyme that functions outside the cell.
Exoerythrocytic cycle:
Portion of the malarial life cycle occurring in the vertebrate host in which sporozoites, introduced by infected mosquitoes, penetrate the parenchymal liver cells and undergo schizogony, producing merozoites, which then initiate the erythrocytic cycle.
Exogenous:
From outside the body.
Exonuclease:
An enzyme that removes nucleotides from the ends of DNA or RNA molecules. See Endonuclease.
Exotoxin:
A toxin produced by a microorganism that is released into the surrounding environment.
Exponential phase:
A period of growth during which a population is growing at a constant rate. Same as log phase. See also Lag, Stationary, and Death phases.
Extrinsic pathway:
Initiation of blood clotting as a result of factors released from damaged tissue, as opposed to contact with a foreign surface (the intrinsic pathway). Tissue thromboplastin (Factor III) in conjunction with Factor VII proconvertin) will activate Factor X that, once activated, converts prothrombin to thrombin.
Exudate:
Fluid that has passed out of blood vessels into adjacent tissues or spaces; high in protein content.
F-factor (fertility factor):
A plasmid that makes a bacterium able to transfer hereditary material to another bacterium during conjugation. In a conjugation, F- cells receive herditary information; F+ cells donate plasmid genes; F' cells donate plasmid genes and some genes also found on the main chromosome; and Hfr cells donate genes on the main chromosome and some genes on the integrated plasmid.
Facilitated diffusion:
Diffusion of molecules through a membrane by means of special pores or proteins that penetrate the membrane. See Diffusion.
Facultative anaerobe:
(1) Organism that usually respires aerobically, but occasionally proliferates under anaerobic conditions by fermenting or anaerobically respiring. (2) Microorganism that grows under either anaerobic or aerobic conditions.
False-negative:
A test result that shows no evidence of the disease or abnormality being investigated although the condition is actually present.
False-positive:
A test result that shows evidence of a disease or an abnormal condition although it (the condition being tested for) is not present.
Fascia:
Membranous covering of muscle.
Fasting Glucose Test:
A blood test done to determine the plasma glucose concentration in the fasting state (the person has not eaten for 8 to 12 hours). A fasting plasma concentration >
140 mg/dl on at least two occasions is diagnostic for diabetes mellitus.
Fatty Acid:
A member of the alkyl hydrocarbons which contain a carboxylic acid as its functional group.
Favus:
Dermatophyte infection of the scalp produced by Trichophyton schoenleinii.
Fermentation:
(1) The production of energy exclusively by substrate level phosphorylation and the use of organic molecules as electron acceptors. Fermentations generally result in the release of organic and inorganic molecules, such as carbon dioxide and molecular hydrogen (gases); lactic, formic, acetic, succinic, butyric, and propionic acids; and ethanol, butanol, and propanol (alcohols). (2) Anaerobic decomposition of carbohydrate; enzymatic decomposition and utililization of foodstuffs by microbes.
Ferritin:
The primary form of storage iron. An iron storage protein of mammals, found in blood, liver, spleen and bone marrow.
Fertilization:
Fusion between sperm and ovum to generate a new organism.
Fibrin:
Clot forming protein — these clots often remain suspended in the serum and cause problems with automated sampling equipment.
Fibrinogen:
Soluble plasma protein (340 kD, 46 nm long), composed of 6 peptide chains (2 each of A_, B_ and _C) and present at about 2-4 mg/ml.
Filamentous:
Threadlike.
Fimbriae:
(1) Proteinaceous fingerlike surface structures of bacteria that provide for adherence to host surfaces. (2) Various types of pilli that extend from the surface of bacteria.
Fistula:
Abnormal communication between two surfaces or between a viscus or other hollow structure and the exterior.
Fitz-Hugh-Curtis syndrome:
Inflammation of the capsule of the liver that may be seen in course of gonococcal or chlamydial infection in the female.
5-hydroxyindole acetic acid (5-HIAA):
5-HIAA is a metabolite of serotonin that is excreted in the urine. Serotonin is a neurotransmitter that is synthesized from the amino acid tryptophan by enterochromaffin cells in the gut and bronchi. It is metabolised to 5-hydroxyindole acetic acid in the liver and then excreted in the urine. Elevations in 5-hydroxyindole acetic acid can indicate carcinoid tumour. The normal range in a 24 hour urine collection is 3 to 15 mg per 24 hours.
Five-prime (5') end:
The end of a DNA or RNA strand with a free 5' phosphate group corresponding to the transcription initiation (see also three-prime end).
Fix:
(1) To attach bacteria to a slide. (2) To alter material such as carbon dioxide and molecular nitrogen, and incorporate the carbon and nitrogen into cellular material. See Nitrogen fixation and Photosynthesis.
Flatus:
Gas produced in the large intestine and expelled through the anus.
Flavobacterium:
Gram negative, spherical or rod-shaped, flagellated or nonmotile, aerobic bacteria.
Flavoprotein:
A protein that contains a covalently bonded flavin group. A component of electron transport systems.
Floccose:
Cottony, in tufts.
Flocculation test:
Antigen-antibody test in which a precipitin end product forms macroscopically or microscopically visible clumps.
Flow cytometry:
A method of measuring physical and chemical attributes of cells or other biological particles by sensors, as they move by, one after the other, homogeneously suspended in fluid. This rapid (about 10,000 particles per second) analytic method allows identification of important cell types, such as malignant cells, T cells and B cells. This process also
may utilize immunologic binding methods to further identify particular cell groups.
Fluorescein:
A molecule that emits light at certain wavelengths; often used to tag antibodies or other proteins and nucleic acids.
Fluorescence:
The emission of light of one wavelength after being exposed to light of a different wavelength. The emission of one or more photons by a molecule or atom activated by the absorption of a quantum of electromagnetic radiation. Typically the emission, that is of longer wavelength than the excitatory radiation, occurs within 10exp-8 seconds; phosphorescence is a phenomenon with a longer or much longer delay in re-radiation. Note that rays, X-rays, UV, visible light and IR radiations may all stimulate fluorescence.
Fluorescence microscopy:
Any type of microscopy in which intrinsic or applied reagents are visualised. Intrinsic fluorescence is often referred to as auto-fluorescence. The applied reagents typically include fluorescently labelled proteins that are reactive with sites in the specimen. In particular, fluorescently labelled antibodies are widely used to detect particular antigens in biological specimens.
Fluorescence polarization immunoassay (FPIA):
See assay.
Fluorescent immunoassays (FIAS):
Similar to RIA but employ fluorescent molecules as labels.
Fluoroscopy:
A radiologic technique in which a fluoroscope is used to visually examine the body or an organ. (A fluoroscope utilizes an X-ray tube and fluorescent screen, with the area
to be viewed placed between the screen and the tube.) This immediate imaging, when coupled with an image intensifier, is invaluable in situations such as cardiac catheterization,
thin needle biopsies of tumors, and localization of foreign bodies.
Fluorochrome:
A dye that becomes fluorescent or self-luminous after exposure to ultraviolet light.
Follicle-stimulating hormone (FSH):
Follicle stimulating hormone is an acidic glycoprotein secreted by the anterior pituitary gland. In women, follicle stimulating hormone stimulates the development of ovarian follicles (eggs) and stimulates the release of estrogens. In men, follicle stimulating hormone stimulates the production of sperm. Abnormal follicle stimulating hormone levels may be seen in hypopituitarism, Klinefelter syndrome, polycystic ovary disease, Turner's syndrome and ovarian failure.
Fomite:
Any inanimate object that may be contaminated with disease-causing microorganisms and
thus serves to transmit disease.
Franciscella tularensis:
Small Gram-negative, elipsoid, rod-shaped, nonmotile, nonsporulationg, aerobic bacteria. Causes tularemia. It enters the body by ingestion, inoculation, inhalation, or contamination. It can penetrate apparently unbroken skin, but may actually enter through microlesions. Also see: tularemia
Free energy:
Energy that can do useful work.
Free radicals:
Molecules or ions with unpaired electrons which are generally extremely reactive. 'Stable' free radicals include molecular oxygen, NO, and NO2. Organic free radicals range from those of transient existence only to very long-lived species. Alkyl free radicals tend to be very reactive and short lived.
FTA:
Fluorescent treponemal antibody.
FTA-ABS:
Fluorescent Treponemal Antigen-Antibody absorption test; indirect fluorescent antibody stain used to detect antibodies directed against whole cell antigens of Treponema pallidum
(syphilis bacillus).
Fulminant:
Sudden, severe or rapid.
Functional group:
Those particular atoms of a biomolecule which are capable of undergoing a chemical reaction with another molecule. Phosphates, Amines, Alcohols, Carbonyl carbons, Carboxylic carbons are examples.
Fungemia:
Presence of viable fungi in blood.
Fungi imperfecti:
See Deuteromycetes.
Fungus (pl. fungi):
Eukaryotic, nonphotosynthetic, micro- and macroscopic organisms that form tubular cells with a rigid cell wall. The cells are interconnected, forming hyphae. Fungi grow typically by extention of hyphal tips.
FUO:
Fever of unknown origin.
Furan/furanose:
Organic compound composed of oxygen and 4 carbons in a ring. The structure of some carbohydrates in an aqueous environment.
Furuncle:
An abscess in the skin, similar to a boil, which sometimes results from an infection of a hair follicle.
Fusiform:
Spindle-shaped, as in the anaerobe Fusobacterium nucleatum.
Fusobacteria:
Gram negative, cigar-shaped, nonmotile or flagellated, anaerobic, catalase negative bacteria.
Gaffkya:
Gram positive, spherical, nonmotile, facultative anaerobic bacterium, usually found in groups of four.
Galactoside:
Molecule that has the sugar galactose attached to it. Examples are lactose, isopropyl thiogalactoside (IPTG), and thiomethyl galactoside (TMG).
Gallbladder:
A sac-like component of the biliary system that stores bile.
Gallionella:
Gram negative, kidney-shaped, flagellated or nonmotile, microaerophilic, ferrous oxidizing bacteria that form a fibrous (noncellular) stalk.
Gallstones:
Concretions or "stones" that form in the gallbladder or bile ducts. Usually composed of precipitated cholesterol.
Gametes:
Sperm or eggs.
Gamma globulins:
A group of serum proteins, some of which function as antibodies.
Gamma hemolysis:
The absence of hemolysis around bacterial colonies growing on blood agar plates.
gamma-Aminobutyric acid (GABA):
Gamma-Aminobutyric acid (GABA) is the product of a biochemical decarboxylation
reaction of glutamic acid by the vitamin pyridoxal. GABA serves as an inhibitory
neurotransmitter to block the transmission of an impulse from one cell to another in the central nervous system. Medically, GABA has been used to treat both epilepsy and hypertension where it is thought to induce tranquility in individuals who have a high activity of manic behavior and acute agitation.
Gamma-glutamyltranspeptidase (GGTP):
An enzyme associated with the uptake of amino acids (protein building blocks) by cells. Normal ranges: Male: 8-38 U/L, Female: 5-27 U/L. Elevated blood levels are frequently seen in alcoholic liver disease (cirrhosis), hepatobiliary disease, Epstein Barr (infectious mononucleosis), pancreatitis and Reye's syndrome.
Gangrene:
Death of a part of tissue resulting from disease, injury, or failure of blood supply.
Gardnerella vaginalis:
Gram negative, rod-shaped, nonmotile, facultatively anaerobic, catalase negative bacteria with many growth requirements. May be involved in nonspecific vaginosis.
Gas constant:
A constant, R, equal to 0.0820 liter-atmosphere/mole-degree at standard conditions (273 degree K, 1 atmosphere); see Perfect-Gas Equation
Gas-liquid chromatography (GLC):
A method for separating substances by allowing their volatile phase to flow through a heated column with a carrier gas and measuring the time required to detect their presence at the distal end of the column.
Gastric:
Referring to the stomach.
Gastric aspirate:
Fluid that may be aspirated from the stomach via a tube placed in the stomach by way of the nose or mouth.
Gastric inhibitory peptide:
A peptide hormone produced in the small intestine that inhibits gastric motility and secretion.
Gastrin:
A peptide hormone secreted by G-cells in the stomach antrum that stimulates secretion of acid into the lumen of the stomach. Normal serum values: <200 pg/mL. Elevations in serum gastrin are seen in Zollinger-Ellison (ZE) syndrome, G-cell hyperplasia, peptic ulcer disease and surgery, high-protein food ingestion, antacid, H2-blocking agent (Tagamet, Zantac) ingestion and insulin injection.
Gastroenteritis:
Inflammation of the mucosa of the stomach and intestines.
Gastroschisis:
A congenital defect in which a fissure is present in the wall of the abdomen, often with protrusion.
GC:
Gonococcus. Also, Gas Chromatography
Gene:
The segment of DNA or RNA that codes for a protein, rRNA, or tRNA. See also Cistron.
Generation time:
The time it takes for a population to double its size. Same as doubling time.
Genetic code:
The representation of amino acids by specific sequences of three nucleotides in DNA or RNA. The specified amino acids are incorporated during protein synthesis.
Genetic map:
An ordered sequence of mutations or genes in a chromosome.
Genome:
A complete set of an organism's hereditary material. In polyploid organisms, a monoploid set of the chromosomes. In bacteria, the circular chromosome and any plasmids. In viruses, the DNA or RNA molecules.
Geotrichum candidum:
A filamentous fungus in the class Deuteromycetes which forms arthrospores.
Germ cells:
Sperm and eggs, and their progenitor cells.
Germ tube:
Tubelike process, produced by a germinating spore, that develops into mycelium.
Germicide:
An agent that destroys germs; disinfectant.
Giantism:
A disease state associated with excessive production of growth hormone.
Giardia lamblia:
A flagellated protozoan. The cause of beaver fever and traveler's diarrhea.
Gibbs Free Energy:
Gibbs Free Energy is a thermodynamic quantity which can be used to determine if a reaction is spontaneous from the equation: G = H - TS, where G is the free energy, H is the enthalpy, S is the entropy and T is temperature (degrees K). For the change in G for a reaction where the temperature does not change, DG = DH - TDS. This equation is often known as the "Gibbs-Helmholtz equation". DH and DS are usually obtained from standard entropy and enthalpy tables, where entropy
is usually given in Joules/mol*K, and enthalpy is usually given in kiloJoules. After suitable unit transformaton and substitutions, DG is usually computed as kJ/mol. If DG < 0, the reaction is spontaneous; if DG > 0, the reaction is not spontaneous; if DG = 0, the reaction is at equilibrium.
Glabrous:
Smooth.
Glaucoma test:
Examination of the eye for the presence of disease that can result in complete and permanent vision loss and that is characterized by increased pressure within the eyeball
and damaged optic disk. When diagnosed early, glaucoma usually can be controlled by the use of suitable eye drops. Continued use of the medication is vital for sight preservation.
A test for glaucoma is advised for all adults every three to five years, as the onset of the chronic form of the disease may be without noticeable symptoms.
GLC:
Gas-liquid chromatography.
Gliding bacteria:
A large group of diverse bacteria that move slowly and smoothly over moist surfaces. They lack axial filaments, flagella, or other protrusions that could be involved in their movement.
Glomerulonephritis:
A variety of nephritis characterised by inflammation of the capillary loops in the glomeruli of the kidney. It occurs in acute, subacute and chronic forms and may be secondary to hemolytic streptococcal infection. Evidence also supports possible immune or autoimmune mechanisms.
Glove box:
A device with flexible, semirigid, or rigid plastic walls used for cultivation of anaerobic bacteria. Bacteriologist must work by way of glove ports, and materials are brought into and out of the anaerobic work area by way of an interchange (airlock) that can be evacuated and refilled with an anaerobic atmosphere repeatedly until it itself is anaerobic. The interchange has one door leading into the glove box per se and another door to the outside. Some glove boxes have incubators within them. Also called anaerobic chamber or anaerobic cabinet.
Glucagon:
A polypeptide hormone secreted by the alpha cells of the islets of Langerhans in response to hypoglycemia. Can be given as a intramuscular injection to treat severe hypoglycemia.
Glucagon-like peptides:
Two peptides derived from proglucagon that are produced in the intestine: GLP-1 and GLP-2.
Glucose:
The main sugar and source of energy in blood. It is contained in common dietary sugar (sucrose). Also known as dextrose, it occurs widely in nature, especially in certain plants. Blood and urine levels of glucose can help diagnose diabetes, hypoglycemia, and hormone disorders. Glucose tests are often called tests for "sugar." A glucose tolerance test, usually performed to assist in the diagnosis of diabetes or hypoglycemia, measures the ability of the body to metabolize a standard amount of the sugar.
Glucose transporters:
Membrane proteins that transport glucose and other hexoses into and out of cells.
Glycocalyx:
Stringy polysaccharides that emanate from the surfaces of cells and help the cells attach to one another and to inanimate objects. In bacteria, the glycocalyx can become so thick that it is indistinguishable from a capsule.
Glucocorticoid:
A type of steroid hormone synthesized and secreted from the adrenal cortex. The major glucocorticoid is cortisol.
Gluconeogenesis:
A metabolic pathway in which non-hexose substrates (amino acids, lipids) are converted to glucose ("formation of new glucose"); occurs predominantly in the liver and, to a lesser extent, in kidney.
Glycolysis:
Same as Embden-Meyerhof pathway.
Glycosidic Bond:
The covalent bond between the anomeric carbon of a carbohydrate and an alcohol (which often is supplied by another sugar).
Glycosylated hemoglobin:
The iron-containing red pigment of red blood cells (hemoglobin) combined with a glucose derivative. When glucose is elevated, more glycosylate product is formed in the cells.
Measurement of this hemoglobin reflects the blood glucose level over the previous several weeks; thus, it is a good indicator of blood glucose control in diabetics.
GN:
Gram-negative (broth).
Goblet cell:
A type of cell that secretes mucus. Found in abundance in the gastrointestinal and respiratory epithelium.
Goiter:
A swelling of the thyroid gland, possible symptom of hypo- or hyperthyroidism.
Gonadotropin:
A term used to describe luteinizing and follicle-stimulating hormones, hormones secreted from the anterior pituitary gland that control several aspects of reproductive function.
Gonadotropin-releasing hormone:
A peptide hormone secreted from the hypothalamus that stimulates secretion of the gonadotropins luteinizing hormone and follicle-stimulating hormone from the anterior pituitary gland.
Gonorrhea:
A chiefly sexually transmitted infection caused by gonococci bacteria. If left untreated, gonorrhea can result in complications including sterility, blindness (preventive treatment is thus routinely given to newborns), or spread to the heart and joints. Women with gonorrhea may be asymptomatic, whereas men often present with a noticeable discharge from the penis.
Goodpasture's syndrome:
Also referred to as the more descriptive name, anti-glomerular basement membrane antibody disease. This autoimmune disease results from severe inflammation in the basement membranes of the glomerulus and the alveolus of the lung. Inflammation occurs due to the formation of antibodies to components of the basement membrane at both sites. Symptoms include bloody urine, decreased urine output, cough with bloody sputum, weakness, fatigue and weight loss. Hypertension and swelling are also common findings on physical examination.
Gout:
Recurrent acute arthritis of peripheral joints caused by the accumulation of monosodium urate crytals. Often presents as pain and swelling confined to one joint. The big toe joint is commonly affected. The arthritis occurs secondary to an inherited abnormality of purine metabolism, resulting in the deposition of uric acid crystals (sodium urate) within the joint space and articular cartilage. Usually due to overproduction of uric acid but may be a result of under excretion. The problems partly arise because neutrophils release lysosomal enzymes as a result of damage to the phagosome membrane by ingested crystals: colchicine acts to reduce the attack by inhibiting lysosome phagosome fusion.
Gram stain:
A method of staining bacteria using crystal violet and safranin stains. The gram staining characteristics (denoted as positive or negative) can assist in the identification of bacteria. A heat fixed bacterial smear is stained with crystal violet (methyl violet), treated with 3% iodine/potassium iodide solution, washed with acetone/alcohol and counterstained with safranin stain. The method differentiates bacteria into two main classes, gram-positive and gram-negative. Certain bacteria, notably mycobacteria, that have walls with high lipid content require acid fast staining.
Gram-negative bacteria:
A common class of bacteria normally found in the gastrointestinal tract that can be responsible for disease in man (sepsis). Bacteria are considered to be gram-negative because of their characteristic staining properties under the microscope, where they either do not stain or are decolorized by alcohol during Gram's method of staining. This is a primary characteristic of bacteria that have a cell wall composed of a thin layer of peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharide containing endotoxin. The gram staining characteristics of bacteria have resulted in an important classification system for the identification of bacteria.
Gram-positive bacteria:
Bacteria that retain the stain or that are resistant to decolorization by alcohol during Gram's method of staining. This is a primary characteristic of bacteria whose cell wall is composed of a thick layer of peptidologlycan containing teichoic and lipoteichoic acid complexed to the peptidoglycan.
Granulocytes:
White blood cells that contain numerous large granules in their cytoplasm: neutrophils, basophils, and eosinophils.
Granulocytopenia:
Reduced number of granulocytic white blood cells in the blood.
Granuloma:
Aggregation and proliferation of macrophages to form small (usually microscopic) nodules.
Grave's Disease:
A disease characterized by excess thyroid hormone production, caused by a stimulation of the thyroid gland by antibodies to the TSH receptor. Ophthalmopathy may or may
not be present.
Growth curve:
A curve tracing the growth of a population in a broth medium. It is divided into phases: lag, exponential (log), stationary, and death.
Growth factors:
Various organic molecules such as amino acids, nucleosides, and vitamins which an organism is unable to synthesize and with which it must be supplied.
Growth hormone:
A protein hormone secreted from the anterior pituitary that has potent metabolic and growth-promoting activities.
Growth rate:
The increase in the number of individuals in a population as a function of time.
Growth yield:
The mass of cells that can be harvested.
HAA:
Hepatitis-associated antigen.
Haemophilus:
Gram negative, spherical to rod-shaped, nonmotile, aerobic or facultatively anaerobic, intracellular bacteria that require growth factors.
Haemophilus ducreyi:
Requires hemin (X-factor). Causes soft chancre known as chancroid, a venereal disease.
Haemophilus influenzae:
Requires hemin (X-factor) and NAD+ (V-factor). Causes meningitis, sinusitis, and pneumonia.
Hafnia:
Gram negative, rod-shaped, peritrichously flagellated, facultatively anaerobic bacteria that resemble Enterobacter.
HAI:
Hemagglutination inhibition.
Halobacterium:
Gram negative, rod-shaped, polarly flagellated or nonmotile, sodium chloride-requiring (more than 2 M), aerobic, oxidase positive bacteria.
Halococcus:
Gram negative, spherical, nonmotile, sodium chloride-requiring (more than 2.5 M), aerobic bacteria.
Halophiles:
Organisms that grow best at (or require) high concentrations of salt.
Halophilic:
Preferring high halide (salt) content.
Haploid:
Cells containing a single set of chromosomes. Mature eggs and sperm, and bacteria are examples of haploid cells.
Hapten:
A molecule that is specifically bound by antibodies, but is unable to induce the production and release of antibodies by plasma cells. A hapten may induce a specific immune response if it is attached to a large protein (carrier molecule).
Hashimoto's Thyroiditis:
An autoimmune destructive disease characterized by atrophy of the thyroid gland.
HATTS:
The hemagglutination treponemal test for syphilis.
HDL cholesterol:
See high density lipoprotein cholesterol.
Headspace gas:
Gas generated during growth of an organism in a closed tube that accumulates between the upper surface of the broth in the tube and the top of the tube.
Heavy chain:
In general, the larger polypeptide in a multimeric protein. Thus the immunoglobulin heavy chain is of 50 kD, the light chain of 22 kD, whereas in myosin the heavy chain is very much larger (220 kD) than the light chains (~20 kD).
Heinz Bodies:
Large red blood cell inclusions that are formed as a result of denatured or precipitated hemoglobin. May be seen in the thalassemia syndromes, G6PD deficiency, or any of the unstable hemoglobin conditions.
Hemadsorption:
Ability of certain virally infected cells to bind erythrocytes; mediated by glycopeptide adherence molecules (induced by viral activities within the cell) on the cell's surface.
Hemagglutination:
Agglutination of red blood cells caused by certain antibodies, virus particles, or high molecular weight polysaccharides.
Hematogenous:
Disseminated by the bloodstream.
Hemiacetal:
The product of a reaction between an aldehyde's carbonyl carbon and an alcohol's oxygen. The spontaneous 6 member ring formed by some carbohydrates is the result of an intra-molecular hemiacetal formation. R-HCOH-O-R'.
Hemicelluloses:
Polymers of D-xylose held together by beta (1,4) linkages with side chains of arabinose and other sugars.
Hemiketal:
The product of a reaction between a ketone carbonyl carbon and an alcohol's oxygen. The spontaneous formation of the furanose ring structure by some carbohydrates is the result of an intra-molecular hemiketal formation: R-HCOR'-O-R".
Hemochromatosis (Iron overload):
Chronic iron (Fe) overload is characterized by increased focal or generalized deposition within the tissues. On tissue examination, this has been commonly termed hemosiderosis. When excess Fe deposition is associated with tissue injury or the total body Fe estimate is > 5 g, the term hemochromatosis has been applied. Hemochromatosis, an HLA-linked genetic Fe overload disorder, must be differentiated from other inherited disorders accompanied by increased Fe stores (eg, aceruloplasminemia, hypotransferrinemia/atransransferrinemia) and from nongenetic Fe overload and Fe overload of undetermined etiology.
Hemochromatosis in its primary form is a genetic disorder with a homozygous frequency of 1:200 and a heterozygous frequency of 1:8. The hemochromatosis gene (HLA-H) was recently identified on the short arm of chromosome 6 as a single point mutation in which the amino acid cysteine at position 282 changes to a tyrosine (nt 845A, 845A; Cys 282 Tyr). Of patients with clinical hemochromatosis, 83% are homozygous for this mutation, which encodes for an HLA-A-like molecule. A mutation at nt 187C(His 63 Asp) linked to the major histocompatibility complex has also been found; these changes have been termed hemochromatosis-associated mutations. Finding these mutations does not explain the pathophysiologic mechanism of the increased Fe absorption. Increased Fe absorption from the GI tract appears to cause the overload. Because physiologic mechanisms for Fe excretion are limited, Fe accumulates in the body. Total body Fe content can reach as high as 50 g, compared with the normal levels of about 2.5 g in women and 3.5 g in men.
In genetic hemochromatosis, the serum Fe is elevated (> 300 mg/dL). The serum transferrin saturation is a sensitive parameter of increased Fe and merits evaluation when > 50%. The serum ferritin is increased, and RBC ferritin is increased to > 200 attograms/RBC. Urinary Fe excretion is markedly increased (> 2 mg/24 h) by the chelating drug deferoxamine (500 to 1000 mg IM based on the size of the patient), and this has been used as a diagnostic test in some circumstances when the diagnosis is uncertain. In addition, when the Fe content in the liver is significantly increased, an MRI may reflect this change. Liver biopsy had been the gold standard in diagnosis; it now serves only to provide evidence of fibrosis (cirrhosis). Gene assay is the diagnostic test of choice. Demonstration of hepatic siderosis and a quantitative increase in liver content (mean hepatic Fe index, > 2; mean hepatic Fe concentration, > 250 µmol/g) confirms the diagnosis.
Phlebotomy is the simplest method for removing excess Fe in patients with hemochromatosis and improves survival but does not alter the incidence of hepatocellular carcinoma. Phlebotomy is best initiated as soon as the diagnosis is made. About 500-1000 mL/wk of blood (about 250-500 mg of Fe) is removed until serum Fe levels are normal and transferrin saturation is well below 50%. Usually, phlebotomy can be performed weekly. When Fe stores are normal, further phlebotomy can be performed to maintain transferrin saturation at < 10%. The serum ferritin level is a less valid parameter during Fe unloading. Diabetes mellitus, cardiac abnormalities, impotency, and other secondary manifestations are treated as indicated.
Hemoglobin:
The oxygen-carrying pigment of red blood cells, it is manufactured in bone marrow, and composed of iron-containing heme and the protein globin. Many types of hemoglobin have
been identified, however adult (A) and fetal (F) types are considered to be normal. Tests to measure hemoglobin concentration and to determine abnormal hemoglobin types are performed to identify anemias and other blood diseases.
Hemoglobin A2:
A small portion of adult hemoglobin (2 to 4 percent), composed of two alpha and two delta chains.
Hemoglobin A, glycosylated:
Minor hemoglobin components of human erythrocytes are designated a1a, a1b, and a1c. Hemoglobin a1c is most important since its sugar moiety is glucose covalently bound to the terminal amino acid of the beta chain. Since normal glycohemoglobin concentrations exclude marked blood glucose fluctuations over the preceding three to four weeks, the concentration of glycosylated hemoglobin A is a more reliable index of the blood sugar average over a long period of time.
Hemoglobin A1C:
The substance of red blood cells that carries oxygen to the cells and joins with glucose. Because the glucose stays attached for the life of the cell (about 4 months), a test to measure hemoglobin A1C shows what the person's average blood glucose level was for that period of time. See Hemoglobin A, glycosylated.
Hemoglobin C:
Hemoglobin C is an abnormal version of the protein hemoglobin. The sixth amino acid of the normal beta chain, glutamic acid, is replaced by lysine in hemoglobin C. This mutation causes the red blood cell to be less flexible.
Hemoglobin F:
The major fetal hemoglobin, composed of two alpha and two gamma chains. Hemoglobin F is the normal form of the protein hemoglobin which is found in the fetus.
Hemoglobin S:
Hemoglobin S is an abnormal version of the protein hemoglobin. The sixth amino acid of the normal beta chain, glutamic acid, is replaced by valine. This mutation causes the red blood cell to take on a sickle shape, and is the cause of the sickle cell trait condition (when the individual is heterozygous for this mutant hemoglobin) and the disease of sickle cell anaemia (when the individual is homozygous for this variant hemoglobin).
Hemoglobin SC disease:
A rare genetic disease of the hemoglobin. Consists of two abnormal hemoglobins: S and C. Estimated prevalence to be 0.04 to 0.13% in the African American population. Patients are anemic due to the premature breakdown of the blood cells in the spleen. Produces a sickle cell-like syndrome. Jaundice may be seen in some patients. Complications include thromboembolic disease, renal papillary necrosis, aseptic necrosis of the femoral (and humeral) head, increased rates of early spontaneous abortion (in pregnant women with SC disease) and proliferative retinopathy. There is no specific treatment other than supportive care.
Hemoglobinopathy:
Disorder due to abnormalities in the hemoglobin molecule, the best known being sickle cell anaemia in which there is a single amino acid substitution (valine for glutamate) in position 6 of the beta chain. See Thalassaemia.
Hemolysis:
Hemolysis results when red blood cells rupture, releasing free hemoglobin and other RBC cytoplasmic content into the plasma or serum. Hemolysis can cause interference for many assays, e.g., potassium, chloride, phosphorus and many enzyme assays. In vivo hemolysis may be caused by RBC antibody sensitivations, RBC osmotic fragility and other diseases. In vitro hemolysis most often results from traumatic blood collection, e.g., aspiration of the blood specimen through too small a hypodermic needle or subjecting the specimen to high vacuum for a prolonged time.
Hemolysis, alpha:
Partial destruction of, or enzymatic damage to, red blood cells in a blood agar plate, leading to greenish discoloration about the colony of the organism producing the alpha
hemolysin.
Hemolysis, beta:
Total lysis of red blood cells about a colony on a blood agar plate, leading to a completely clear zone surrounding the colony.
Hemolysis, gamma:
No hemolysis is seen with organisms classed as gamma hemolytic; non-hemolytic would be a better designation.
Hemolytic Disease of the Newborn (HDN):
A disease characterized by anemia, jaundice, enlargement of the liver and spleen, and
generalized edema (hydrops fetalis), owing to the maternal IgG antibodies that cross the placenta and attack fetal red cells when there is a fetomaternal blood group incompatibility. Usually caused by ABO or Rh antibodies.
Hemolytic-uremic syndrome:
A pathologic condition which involves the rupture (hemolysis) of red blood cells, subsequent anemia, low platelet count and kidney failure. It is a syndrome of hemolytic anemia, thrombocytopenia, and acute renal failure, with pathological finding of thrombotic
microangiopathy in kidney and renal cortical necrosis.
Hemophilia:
A hemorrhagic diathesis occurring in two main forms: 1) Hemophilia A (classic hemophilia, factor VIII deficiency), an X linked disorder due to deficiency of coagulation factor VIII. 2) Hemophilia B (factor IX deficiency, Christmas disease), also X linked, due to deficiency of coagulation factor IX. Both forms are determined by a mutant gene near the telomere of the long arm of the X chromosome (Xq), but at different loci and are characterised by subcutaneous and intramuscular hemorrhages, bleeding from the mouth, gums, lips and tongue, hematuria and hemarthroses.
Hemopoiesis:
The formation and development of blood cells involving both proliferation and differentiation from stem cells. In adult mammals usually occurs in bone marrow.
Henderson-Hasselbalch equation:
The Henderson-Hasselbalch equation is the equation: pH = pK + log ([A-]/[HA]), where pH is the acidity or alkalinity of the buffer solution, pK is the negative logarithm of the equilibrium constant (Kd) for the ionization of the acid form (A-) of the compound used to buffer the solution for the reaction HA = H+ +A-, [A-] is the molar concentration of the ionized form of the buffer compound, and [HA] is the molar concentration of the nonionized form of the buffer compound.
HEPA:
High-efficiency particulate air filter; used in biological safety cabinets to trap pathogenic microorganisms.
Heparin:
Sulphated mucopolysaccharide, found in granules of mast cells, that inhibits the action of thrombin on fibrinogen by potentiating antithrombins, thereby interfering with the blood clotting cascade. Heparin with its plasma co-factor Antithrombin III, inhibits coagulation immediately after being administered. It is the drug of choice for treating venous thrombosis by preventing fibrin formation. Platelet factor IV will neutralize heparin.
Hepatic:
Pertaining to the liver
Hepatitis:
Inflammation of the liver, usually caused by bacterial or viral infection, drugs (including alcohol), toxins, or parasites. This disease is characterized by an enlarged liver, jaundice, diminished appetite, nausea, and abdominal pain. There are at least three forms of viral hepatitis (hepatitis A, hepatitis B, and non-A, non-B hepatitis). Hepatitis A, also known as infectious hepatitis, is transmitted by contaminated food or water and personal contact, and is most often found in children or young adults. Hepatitis B, formerly called serum hepatitis, may be transmitted through contaminated blood or needles, as well as sexually, and has a longer incubation period than that of hepatitis A. Hepatitis B can result in chronic active hepatitis. Non-A, non-B hepatitis is also transmitted through blood and can cause severe liver damage. Radioimmunoassays and enzyme-linked immunosorbent assays may be used to screen for hepatitis.
Hepatitis B surface antigen (HBsAG):
A part of the hepatitis B virus that, when in the blood, is one of the earliest markers of infection with hepatitis B virus, appearing even before symptoms. Also found in blood
of a carrier. HBsAG is tested for in the differential diagnosis of hepatitis.
Hepatocyte:
The major functional cell in the liver
Hepatoma:
A malignant tumor of the liver (primary hepatocellular carcinoma) sometimes associated with hepatitis or cirrhosis. Elevated blood levels of alpha-fetoprotein (AFP) may indicate the presence of a hepatoma. AFP levels are useful in monitoring chemotherapeutic success in treating this condition.
Hepatotoxin:
A substance that is toxic to liver cells.
Hereditary Elliptocytosis (HE):
An inherited (autosomal dominant) intracorpuscular defect of the red cell membrane that is characterized by the presence of greater than 40 percent elliptical red cells on the peripheral blood smear. The condition is generally asymptomatic. There is a biochemical and genetic relationship to hereditary pyropoikilocytosis (HPP).
Hereditary Pyropoikilocytosis (HPP):
A relatively rare and severe autosomal recessive hemolytic anemia characterized by striking bizarre micropoikilocytosis in which the red cells bud, fragment, and form microspherocytes. In addition, the red cells are thermally unstable when heated to 45°C and
strikingly fragmented in comparison to normal red cells which fragment only at 49°C.
Hereditary Spherocytosis (HS):
An inherited (autosomal dominant) intracorpuscular defect of the red cell membrane (altered spectrin) that results in the most common hereditary hemolytic anemia found in whites. The morphologic hallmark of hereditary spherocytosis is the presence of spherocytes on the peripheral blood smear.
Hereditary Stomatocytosis (Hereditary hydrocytosis):
A heterogenous group of rare red cell membrane disorders inherited in an autosomal dominant fashion that are characterized by the presence of stomatocytes on the peripheral blood smear and alterations in the permeability of the red cell membrane to cations.
Herpes:
Inflammation of the skin characterized by clusters of small vesicles (e.g., caused by herpes simplex); disease caused by herpes simplex virus.
Heterodimer (heterodimeric):
A protein complex composed of two different proteins.
Heterokaryosis:
A condition in which a cell contains more than one type of nucleus.
Heterofermentation:
A fermentation in which there are a number of waste products. Used in connection with lactic acid bacteria that have major waste products other than lactic acid.
Heterotroph:
Organism that requires an organic carbon source.
Hexose:
A simple sugar or monosaccharide that contains six carbon atoms. Examples include glucose, galactose and fructose.
Hidradenitis suppurativa:
Inflammation of certain sweat glands leading to formation of abscesses and draining sinuses.
High density lipoprotein cholesterol (HDLC):
The fraction of plasma lipoprotein cholesterol component with most density (relative weight). It is thought to affect blood cholesterol levels by removing it from plasma and
tissues and carrying it back to the liver for excretion after being acted on by bile. High levels of HDLC are considered to place an individual at a lower risk for coronary heart
disease (atherosclerosis). Low levels of HDLC are associated with an increased risk for the disease. The density may be established by ultracentrifugation or electrophoresis.
High-pressure liquid chromatography (HPLC):
Similar to GLC but capable of higher resolution because of increased pressure of liquid carrier that runs through the column.
Hilum of lung:
Central area where major vessels and bronchi begin to branch.
Histogram:
A graphic means of comparing magnitudes of frequencies or numbers of items; usually shown in bar graphs or columns.
Histology:
The study of the microscopic structure or anatomy of tissues.
Histoplasma capsulatum:
A fungus in the class Deuteromycetes which causes histoplasmosis, usually a mild coldlike disease.
Homeostasis:
Maintenance of a stable and balanced environment in the body. For example, calcium homeostasis refers to the mechanisms that keep concentrations of calcium within a "normal range" despite temporary excursions below and above.
Homocysteine:
Homocysteine is an amino acid derived from the digestion of protein-rich foods.
Homodimer (homodimeric):
A protein complex composed of two identical proteins.
Homofermentation:
A fermentation in which there is only one major waste product. Used in connection with lactic acid bacteria that produce lactic acid and very minor amounts of other acids.
Hormone:
Chemical substances secreted by organs or parts of the body, especially the endocrine glands, into the bloodstream. Each hormone has a specific regulatory or functional effect. Hormones are categorized into four structural groups, with members of each group having many properties in common: 1) Peptides and proteins, 2) Steroids, 3) Amino acid derivatives, 4) Fatty acid derivatives - Eicosanoids.
Howell-Jolly Bodies:
Red cell inclusions that develop in periods of accelerated or abnormal erythropoiesis. They represent nuclear remnants containing DNA.
HPLC:
High-pressure (or performance) liquid chromatography.
Human Immunodeficiency Virus (HIV):
A type of retrovirus (human immunodeficiency virus) that is responsible for the fatal illness acquired immunodeficiency syndrome. Two strains have been identified. Type 1: the retrovirus recognised as the agent that induces AIDS. Type 2: a virus closely related to HIV-1 that also leads to immune suppression. HIV-2 is not as virulent as HIV-1 and is epidemic only in West Africa.
Human leukocyte antigen (HLA):
A genetic fingerprint on white blood cells and platelets, composed of proteins that play a critical role in activating the body's immune system to respond to foreign organisms.
Humidophilic:
Organisms preferring or requiring an increased moisture content; can be achieved by placing cultures in sealed jars or bags. For some organisms that do better in a candle jar than in the ambient atmosphere, it is the increased moisture content rather than the change in the gas content that is important.
Humoral immunity:
Immunity effected by antibody. Immunity mediated by antibodies that circulate through the lymphatic system and the blood system. "Humor" refers to the body fluids.
Hyaline:
Colorless, transparent, e.g., hyaline cast.
Hybridoma:
The product of fusion of an antibody-producing cell and an immortal malignant
antibody-producing cell.
Hydration:
A reaction involving the addition of water to a molecule. The addition of water to an alkene to produce an alcohol.
Hydrocarbon:
A compound composed only of carbons and hydrogens. The carbons are covalently linked to each other. The bonding valence for carbon is completed by bonds to hydrogens. See Alkanes.
Hydrocortisone:
A synonym for the hormone cortisol.
Hydrogen bacteria:
Bacteria that derive their energy by oxidizing molecular hydrogen. Examples include some species of Alcaligenes, Xanthobacter, Nocardia, and Paracoccus.
Hydrogen bond:
A weak attractive force between two electronegative atoms expressed through the "sharing" of a single hydrogen atom. R-H2C=O..H..O-CH2-R'.
Hydrolysis:
A chemical reaction in which a compound reacts with water, resulting in its decomposition or alteration. A reaction using water to break a covalent bond; a proton (H+) is added to one product and a hydroxyl (OH-) to the other. Breaking of an ester bond to produce a molecule containing a carboxyl group and a molecule with an alcohol group.
Hydronium ion:
The hydrated proton. The hydrogen cation in an aqueous solution. H3O+.
Hydrophilic forces:
Forces that arise from chemical groups or molecules that arrange themselves in an aqueous environment in such a way as to be surrounded by water.
Hydrophobic forces:
Forces that arise from chemical groups or molecules that arrange themselves in an aqueous environment in such a way as to exclude water.
Hydrostatic pressure:
Pressure of fluid in a system (e.g. vascular system or extracellular fluid). Often used as equivalent to osmotic pressure when dealing with flow of water across membranes.
Hydroxyl group:
The hydroxide (OH) attached to a compound as a functional group. The functional group of an alcohol. -OH.
Hygroma:
A fluid-filled sac, bursa or cyst. A cystic hygroma is lined with endothelial cells derived from the lymphatic system.
Hyper-:
Prefix meaning excess. Hypertension is the condition of blood pressure in excess of what is normal.
Hyperalimentation:
Process by which nutrition (literally, extra nutrition) is provided; typically done by the intravenous route in subjects who are not able to absorb foods well from the gut because of disease of the bowel, in subjects in whom it is desirable to put the bowel "at rest" to promote healing, and in malnourished individuals to improve the nutritional status (e.g., before surgery), usually done over an extended period of time and requires use of a special access IV catheter such as a Hickman catheter.
Hyperchromia:
Presence of red cells with abnormally increased cell hemoglobin content.
Hyperemia:
Increased blood in a part, resulting in distention of blood vessels.
Hyperglycemia (high blood sugar):
A condition in which the blood contains an abnormally high level of glucose, characteristic of diabetes mellitus.
Hyperkalemia:
Abnormally high concentrations of potassium in blood.
Hypernatremia:
Abnormally high concentrations of sodium in blood.
Hyperparathyroidism:
The over production of parathormone by the parathyroid glands. Usually secondary to an adenoma (an unregulated glandular tumour that produces parathormone in an increased quantity). Laboratory studies show an elevated calcium in the blood. Most patients are without symptoms. Symptoms in more advanced cases include lethargy, confusion, nausea, bone pain and weakness. Findings include hypertension and slow heart rate. Complications include pancreatitis, peptic ulcer disease and kidney stones.
Hyperplasia:
An increase in number of cells (rather than cell size); often associated with an increase in organ size.
Hypersegmentation:
An increase in the number of nuclear lobes or segments (more than 6) in segmented neutrophils; especially characteristic in vitamin B12 and folic acid deficiencies.
Hyperthyroidism:
A condition characterized by accelerated metabolism caused by an excessive amount of thyroid hormones (overactive thyroid).
Hypertonic:
Hyperosmotic. A solution with a relatively high concentration of solutes or dissolved materials. See Hypotonic and Isotonic.
Hypertrophy:
Increased size of an organ resulting from enlargement of individual cells.
Hypha:
1) A filament of fungal growth. 2) Tubular cell making up the vegetative portion of mycelium of fungi.
Hyphomicrobium:
Rod-shaped, hyphae forming, nonmotile or motile, aerobic bacteria that reproduce by a budding process.
Hypo-:
Prefix meaning below or deficient. Hypotension is the condition of blood pressure below normal.
Hypochromia:
Presence of cells with abnormally low cell hemoglobin content. Increased area of central pallor in red cells.
Hypoglycemia (low blood sugar):
A condition in which there is an abnormally diminished concentration of glucose in the blood, which may lead to convulsions or coma.
Hypokalemia:
Abnormally low concentrations of potassium in blood.
Hyponatremia:
Abnormally low concentrations of sodium in blood.
Hypoparathyroidism:
A term which describes the abnormally low production of parathyroid hormone by the parathyroid glands. Hypoparathyroidism may be congenital or occur in association with another disorder (autoimmune disease, haemochromatosis). Common symptoms are those of low blood calcium: muscle spasms, tetany, facial grimacing, laryngeal spasm and seizures.
Hypothalamus:
An area of the brain that regulates endocrine activity as well as somatic functions e.g.body temperature, sleep, appetite. Hypothalamic neurohormones (e.g.TRH) control various functions of the pituitary gland.
Hypothyroidism:
A condition characterized by deficient production of thyroid hormones (underactive thyroid).
Hypotonic:
A solution with a relatively low concentration of solutes or dissolved materials as compared to the cellular environment. See Hypertonic and Isotonic.
Hypovolemia:
A term which describes a condition of abnormally low intravascular volume with a decreased volume of circulating plasma in the body. It can be due to blood loss or dehydration.
Hypoxia:
Decreased oxygen content of tissues.
Iatrogenic:
Induced inadvertently by the medical treatment or procedures or actvity of a physician. Originally applied to disorders induced in the patient by autosuggestion based on the physician's examination, manner or discussion, the term is now applied to any adverse
condition in a patient occurring as the result of treatment by a physician or surgeon, especially to infections acquired by the patient during the course of treatment. See nosocomial.
Icteric:
A yellow color in the serum due to red cell destruction. Usually caused when the liver is not functioning properly. The presence of a yellow color from bilirubin in serum, plasma, csf or other body fluids; it is usually present in jaundice. Icteric serum is often graded on a scale of 1+ to 4+.
Icterus:
A yellow discoloration of mucous membranes and skin due to high concentrations of bilirubin in blood and tissues. The presence of jaundice seen in the sclera of the eye.
ID:
Infectious disease; identification; immunodiffusion.
Idiopathic:
Pertaining to conditions without clear pathogenesis or to disease without recognizable cause, as of spontaneous origin.
IE:
Infectious endocarditis.
IFA:
Indirect fluorescent antibody; test that detects antibody by allowing an antibody to react with its substrate and adding a second fluorescein dye-labelled antibody that will bind to the first.
Ig, IgG, etc.:
Immunoglobulin, immunoglobulin G, etc.
IgA:
Antibodies of the A class, found in secretions.
IgD:
Antibodies of the D class, found attached to the surfaces of B-lymphocytes.
IgE:
Antibodies of the E class, found in the lymph and blood, which are involved in allergic reactions.
IgG:
Antibodies of the G class, found in the lymph and blood, which bind complement. IgG are the most abundant antibodies.
IgM:
Antibodies of the M class, found attached to the surfaces of B-lymphocytes and in the lymph and blood, which bind complement. They are the first antibodies to be produced by B-lymphocytes.
Ileum:
The terminal section of the small intestine.
Immediate-type hypersensitivity:
An antibody-mediated allergic reaction that occurs within minutes after presentation of antigen to which the individual is sensitized.
Immunochemical:
Describing the chemistry of antigens, antibodies, and their relation to each other.
Immunodeficiency:
The lack of part or all of the immune system.
Immunodiffuslon:
Detection of antigen or antibody by observing the precipitin line formed in a semisolid gel matrix when homologous antigens and antibodies are allowed to diffuse toward each other and react.
Immunoelectrophoresis:
Pertaining to investigation of substances and their identifications by a method combining mobility in an electric field and utilizing an antigen-antibody reaction. It refers to a combination technique used to evaluate proteins in a mixture, or the characteristics of a specific protein.
Immunofluorescence:
A method of locating antigens in tissue, or of identifying an antigen by the fluorescence resulting when the antigenic material is exposed to a specific antibody coupled with a fluorescent dye. The antigen-antibody combination then is visible (luminous) using ultraviolet light. This technique is used in the diagnosis of syphilis, toxoplasmosis (a serious disease which may lead to blindness and brain defects in the congenital form, as well as myocarditis and other conditions), and other diseases.
Immunoglobulins (Ig):
A family of similar but distinctly different proteins which act as antibodies of five major types (IgA, IgD, IgE, IgG, and IgM). They are produced in lymphoid tissue by B lymphocytes and plasma cells, in response to the presence of antigenic substances.
Immunology:
The study of immunity — the security or protection against a foreign organism or poison introduced into an individual.
Immunoperoxidase stain:
Combination of an enzyme that catalyzes production of a colored product with an antibody to facilitate detection of certain antigens, particularly viral antigens.
Immunosorbence:
A method of (or preparation for) using an insoluble substance combined with specific antibody or antigen for absorbing antigen or antibody components from blood. This allows
determination of the amount of antigen or antibody in the specimen.
Immunosuppression:
Depression of the immune response caused by disease, irradiation, or administration of antimetabolites, antilymphocyte serum, or corticosteroids.
Impedance:
Vectoral sum of resistance, inductive reactance and capacitive reactance in an alternating current circuit; apparent resistance of a circuit to the flow of an alternating electric current.
Impetigo:
Acute inflammatory skin disease, caused by streptococci or staphylococci, characterized by vesicles and bullae that rupture and form yellow crusts.
Impotence:
The inability to have an erection.
IMViC:
A group of four biochemical tests (indole, methyl red, Voges-Proskauer, and citrate) used to differentiate enteric bacteria.
In situ hybridization:
Detection of nucleic acid of a pathogenic organism in tissue sections by separating the DNA into single-stranded molecules and allowing a labeled strand of homologous DNA to bind to the target. The target is visualized by developing the label (either enzymatic precipitate, fluorescence, or radiolabel).
In vitro:
Literally, within glass (i.e., in a test tube, culture plate, or other nonliving material; outside of the body).
In vivo:
Within the living body.
Inclusion bodies:
Microscopic bodies, usually within body cells; thought to be virus particles in morphogenesis.
Incontinence:
A loss of urinary control.
Indigenous flora:
Normal or resident flora.
Indole :
a compound obtained from coal tar and indigo and produced by decomposition of tryptophan in the intestine, where it contributes to the peculiar odor of feces. It is excreted in the urine in the form of indican.
Induced malaria:
Malaria infection acquired by parenteral inoculation (e.g., blood transfusion or sharing of needles by drug addicts).
Inducer:
A physical or chemical agent that causes the development of lysogenic viruses or turns on gene systems (operons). For example, ultraviolet light is an inducer of the
lambda prophage, whereas lactose if the inducer of the lactose operon. See Effector.
Induration:
Abnormal hardness of a tissue or part resulting from hyperemia or inflammation, as in a
reactive tuberculin skin test.
Infection:
Invasion by and multiplication of microorganisms in body tissue resulting in disease.
Infectious mononucleosis:
Self limiting disorder of lymphoid tissue caused by infection with Epstein Barr virus (infectious mononucleosis). Characterized by the appearance of many large atypical lymphocytes in the circulation.
Ingestion:
The act of taking food or other materials into the mouth.
Inhibitory quotient:
Ratio of the average peak achievable level of antibiotic in a body fluid from which an organism was isolated to the MIC of that organism.
Initial bodies:
Same as reticular bodies: intracellular chlamydia cells that grow and divide. They transport ATP and carry out protein synthesis, but they are not infectious because they are extremely sensitive to mechanical and osmotic shock. In electron micrographs, they have the appearance of typical prokaryotes except that they appear to lack a peptidoglycan layer. Initial bodies are also known as reticulate bodies (RBs). See Elementary bodies.
Insertion sequence:
Regions of DNA that are able to recombine readily with different regions within and between chromosomes. Insertion sequences in plasmids are believed to be involved in the plasmid's ability to insert into the cell's chromosomes.
Inspissation:
Process of making a liquid or semisolid medium thick by evaporation or absorption of fluid.
Insulin:
A protein hormone secreted by the beta cells of the pancreas that signals the fed state. It is secreted in response to elevated blood levels of glucose.
Insulin Resistance:
A defect present in the majority of individuals with impaired glucose tolerance and essentially in all patients with Type 2 diabetes and is an impairment of insulin action.
Insulin-like growth factors:
Polypeptide hormones synthesized by many tissues. Insulin-like growth factor-1 synthesis is stimulated by growth hormone.
Inter-:
Prefix meaning between. An intercellular substance is between cells.
Integral protein:
A membrane protein which is strongly associated with the lipid bilayer, needing harsh treatment to separate from the bilayer. Separating the integral protein from the lipid bilayer results in the protein's loss of function.
Interferon:
A class of proteins, released by virus-infected cells, which stimulate uninfected cells to produce proteins that inhibit the proliferation of viruses.
Intestine:
A section of the digestive system; includes both small intestine (duodenum, jejunum and ileum) and large intestine (colon, cecum and rectum).
Intra-:
Prefix meaning within or inside. An intracellular structure is inside a cell.
Intracytoplasmic membranes:
Membranes found in the cytoplasm of some bacteria. Many of these membranes are invaginations of the cytoplasmic membrane. See Chromatophore, Photosynthetic membrane, Thylakoid, and Chlorobium vesicle.
Intermediate host:
Required host in the life cycle in which essential larval development must occur before a parasite is infective to its definitive host or to additional intermediate hosts.
Intertrigo:
Erythematous skin eruption of adjacent skin parts.
Intramuscular (intraperitoneal, intravenous):
Within the muscle (peritoneum, vein), as in intramuscular injection.
Intrinsic factor:
A glycoprotein secreted from the lining of the stomach involved in the absorption of vitamin B12.
Involution forms:
Abnormally shaped bacterial cells occurring in an aging culture population.
Ion-exchange chromatography:
Separation of components of a solution by chromatography based on the reversible exchange of ions in the solution with ions present in or on an external matrix.
Ionic bond:
A weak electrostatic attractive force between atoms of opposite charge. R-NH3+...O-OC-R'.
Iron (Fe):
An essential element enabling the oxygen-carrying capacity of hemoglobin in red blood cells. A large portion of iron in the body is found in hemoglobin, muscle and other tissues, while some of the remaining iron is bound to an iron-transporting serum protein called transferrin. Tests to measure iron are performed to detect and evaluate iron-deficiency anemias or abnormally high levels of iron found in hemochromatosis (excess iron deposits throughout the body).
Iron bacteria:
Bacteria that derive energy by oxidizing ferrous iron (Fe+2) to ferric iron (Fe+3). An example is Thiobacillus ferrooidans.
Ischemia:
A low oxygen state usually due to obstruction of the arterial blood supply or inadequate blood flow leading to hypoxia in the tissue.
Isoantibodies:
Antibodies against foreign isoantigens. For instance, antibodies against A-type blood in persons with B- or 0-type blood.
Isoantigens:
Antigens that are present in some individuals of a population but not in other individuals. For example, people with A-type blood have antigens that people with B- and 0-type blood do not have.
Isoelectric:
A condition wherein a molecule containing both positive and negative charges in equal numbers so the molecule's net charge is zero.
Isoelectric focusing:
Isoelectric focusing is electrophoresis in a stabilized pH gradient. It provides a high resolution method for separating molecules, especially proteins, that carry both positive and negative charges. Molecules migrate to the pH corresponding to their isoelectric point. The gradient is produced by electrophoresis on amphiphiles (or ampholytes), heterogenous molecules giving a graduated continuum of isoelectric points. Resolution is determined by the number of amphiphile species and the evenness of distribution of their isoelectric points.
Isoenzyme:
Variants of enzymes that catalyze the same reaction, but owing to differences in amino acid sequence can be distinguished by techniques such as electrophoresis or isoelectric focusing. Different tissues often have different isoenzymes. The sequence differences generally confer different enzyme kinetic parameters that can sometimes be interpreted as fine tuning to the specific requirements of the cell types in which a particular isoenzyme is found.
Isoform:
A protein having the same function and similar (or identical) sequence, but the product of a different gene and usually tissue specific.
Isomer:
Molecules of the same composition and formula weight but differing in structure or configuration.
Isotonic:
A solution with the same osmotic pressure (usually the same concentration of solutes) as another solution. See Hypertonic and Hypotonic.
Isotopic assay techniques:
Methods of identifying and measuring substances such as hormones, by using procedures that employ labeling with material having radioactive properties (isotopes). Detection
of radiation enables measurement of the desired analyte.
Ixodes persulcatus:
A tick that transmits the virus responsible for Russian spring-summer encephalitis (RSSE).
Jaundice:
A yellow discoloration of mucous membranes and skin due to high concentrations of bilirubin in blood and tissues. The same as icterus.
Jaundice, neonatal:
A type of jaundice commonly seen in infants.
Jejunum:
The middle and largest section of the small intestine.
K-antigen:
The capsule material from enteric bacteria.
Karyotype:
The complete set of chromosomes of a cell or organism. Used especially for the display prepared from photographs of mitotic chromosomes arranged in homologous pairs.
Kawasaki disease:
Mucocutaneous lymph node syndrome; disease of children that may involve more serious phenomena such as cardiac disease.
Kell blood group system:
Blood type classification based on a group of erythrocyte antigens that is characterised by an antibody called anti-K.
Keratitis:
Inflammation of the cornea.
Kernicterus:
A severe form of neonatal jaundice resulting from high blood concentrations of bilirubin.
Ketal:
The product of a reaction that connects the carbonyl carbon of a ketone to the oxygens of two different alcohols. Ketals are formed with many glycosidic bonds of polysaccharides.
Ketoacidosis:
A condition in which acidosis is accompanied by the accumulation of ketone bodies in the body tissues and fluids as in diabetic acidosis and starvation acidosis.
Ketone:
A molecule which contains a carbonyl carbon covalently bonded to two other carbons.
KIA:
Kligler's iron agar (tube).
Killer T-Cells:
One class of T-lymphocytes involved in cell-mediated immunity.
Kinase:
A common name used to describe enzymes that covalently add phosphate residues to proteins (e.g. protein kinase A) or nucleic acids (e.g. polynucleotide kinase).
Kinetics:
The study of reaction rates and the study of the relationship between force and mass.
Kinins:
Small peptides, released into the blood and lymph upon trauma, which are involved in blood clotting and inflammatory reactions.
Klebsiella pneumoniae:
Gram negative, rod-shaped, nonmotile, encapsuled, facultatively anaerobic bacterium. A cause of pneumonia.
Kleihauer-Betke test:
An indicator of fetal (F) hemoglobin in red cells. The test is based on the property that hemoglobin F is not readily soluble in an acid buffer, unlike normal adult hemoglobin (hemoglobin A). Demonstration of these two hemoglobins aids in the diagnosis of a number of blood disorders, and of fetal-maternal hemorrhage.
Klenow fragment:
A fragment of the E. coli DNA polymerase that is widely used in recombinant DNA work.
Klinefelter's syndrome:
Klinefelter's syndrome is a congenital disorder characterized by small testes, azoospermia, infertility, increased urinary excretion of gonadotropin, tall long legs and gynecomastia. It is ssociated with a supernumerary X chromosome resulting in XXY sex chromosomes. Chronic manifestations begin at puberty.
Koch's postulates:
A set of procedures for proving that an organism is responsible for a disease.
KOH:
Potassium hydroxide.
Kohler illumination:
Modification of brightfield microscopy in which a substage condenser is used to avoid glare from illuminating source.
Krebs cycle:
Same as the citric acid cycle and the tricarboxylic acid cycle.
Kuppfer cells:
Phagocytic cells that reside within the sinusoids of the liver.
Kuru:
A progressive degenerative brain disease caused by a prion.
L form:
1) Cell wall-deficient form of a bacterium. 2) Common bacteria that do not produce a normal peptidoglycan layer or have lost the ability to manufacture the peptidoglycan layer of their cell walls. See Protoplasts and Spheroplasts.
Lactate dehydrogenase or lactic acid dehydrogenase (LDH):
An enzyme important in provision of muscle energy (carbohydrate metabolism), that is present in many cells, particularly those of the heart, kidneys, liver, and skeletal muscle. Elevated blood levels of LDH may confirm a suspected heart attack.
Lactic acid bacteria:
A group of gram positive, catalase negative, exclusively fermentative, spherical and rod-shaped bacteria that carry out a lactic acid fermentation. Examples are Streptococcus and Lactobacillus.
Lactic acid fermentation:
A fermentation in which the major waste product is lactic acid.
Lactobacilli (sing. lactobacillus):
Lactic acid bacteria. Gram positive, rod-shaped, nonmotile, aerotolerant, anaerobic,
catalase negative bacteria.
Lag phase:
Period of slow microbial growth that occurs following inoculation of the culture medium. The period of time during which a population is adapting to new environmental conditions before it reproduces exponentially. During the first part of a lag phase, a
population may not increase in number. In the latter part of the lag phase, the population multiplies at an ever increasing rate. See Exponential, Stationary, and Death phases.
Laked blood:
Hemolyzed blood; hemolysis may be effected in various ways, but alternate freezing and thawing is a simple method.
Lamina propria :
A thin layer of connective tissue that supports the epithelium in tubular organs like the intestine.
Laminar flow:
Nonturbulent flow of air in layers (flowing in a vertical direction in the case of a
biosafety hood).
Lapine:
Pertaining to or derived from rabbits.
Latent:
Not manifest; potential.
Latent period:
The time from the initiation of a virus infection until virus progeny are released.
Latex agglutination:
Agglutination of latex particles coated with antibody molecules when exposed to the corresponding antigen.
LDH:
See lactate dehydrogenase.
LDL cholesterol:
See low density lipoprotein cholesterol.
Lectin:
Naturally produced proteins or glycoproteins that can bind with carbohydrates or sugars to form stable complexes.
Leishman-Donovan (L-D) body:
Small, round intracellular form (called amastigote or leishmanial stage) of Leishmania species and Trypanosoma cruzi.
Leghemoglobin:
A hemoglobin-like molecule coded for by both the endosymbiotic bacteria in root nodules of leguminous plants and the host plant cells. Leghemoglobin binds molecular oxygen and protects the bacterial nitrogenase, which is oxygen sensitive.
Legionella pneumophila:
Gram negative, rod-shaped, nonmotile, aerobic, weakly oxidase positive bacteria with numerous growth requirements. Causes Legionnaires' disease, a pneumonia.
Legionnaires' disease:
A pneumonia. See Legionella.
Leishmania donovani:
A flagellated protozoan that reproduces in phagocytes and causes a serious leishmaniasis, called kala-azar.
Leptin:
A hormone produced by fat cells that participates in control of food intake.
Leptocyte:
Synonymous with Target Cell.
Leptospira iterrogans:
Gram negative, helical, motile by axial filament, microaerophilic, aerobic bacterium. Causes leptospirosis.
Leptothrix:
Gram negative, rod-shaped, nonmotile, anaerobic, catalase negative, carbon dioxide-requiring bacteria.
Leuconostoc mesenteroides:
A lactic acid bacterium that is gram positive, spherical, nonmotile, aerotolerant, anaerobic, and catalase negative.
Leucothrix:
Gram negative, oval, filament-forming, nonmotile, aerobic, sulfide-oxidizing bacteria that do not form sulfur granules.
Leukemia:
An acute or chronic disease of unknown cause in man and other warm blooded animals that involves the blood forming organs, is characterised by an abnormal increase in the number of leukocytes in the tissues of the body with or without a corresponding increase of those in the circulating blood and is classified according of the type leukocyte most prominently
involved.
Leukocyte:
White blood cells, such as neutrophils, basophils, and eosinophils.
Leukocyte chemotaxis:
The movement of leukocytes in response to a chemical concentration gradient or to products formed in an immunologic reaction.
Leukocytosis:
Elevated white blood cell count.
Leukopenia:
Low white blood cell count.
Levans:
A homopolymer of D-fructose connected by beta (1,2) linkages.
Lewis blood group:
A pair of blood group activities associated with the A, B, H substances. Lewis Lea is a separate gene, whereas Leb arises from the combined activity of the enzymes specified by Lea and H genes.
LGV:
Lymphogranuloma venereum; the name for certain strains of Chlamydia trachomatis that cause a systemically expressed sexually transmitted disease.
LH-RH:
Man-made compounds that are similar to the natural leutinizing hormone-releasing hormone which aids in the production of testosterone.
Lichen:
A symbiotic association between eukaryotic algae or cyanobacteria and fungi which creates an organism distinct from either of the mutuals.
Ligand:
A molecule that binds to a specific site on another molecule. Usually, the ligand is a hormone and the molecule to which it binds is a receptor. Example: insulin is the ligand for the insulin receptor.
Ligase:
An enzyme that catalyzes the formation of phosphodiester bonds in DNA. The enzyme from T4 bacteriophage is widely used in recombinant DNA work.
Ligase chain reaction (LCR):
A method of DNA amplification similar to PCR, except that it uses four primers instead of two and uses the enzyme ligase to ligate or join two segments of DNA. It can have
greater specificity than PCR.
Ligation:
To tie together or tie off. Examples include ligating a blood vessel to stop it bleeding, or ligating fragments of DNA together enzymatically.
Light chain:
The lighter of the two types of polypeptide chains that are found in immunoglobulin and antibody molecules. Also used as a nonspecific term for the smaller subunits of several multimeric proteins such as immunoglobulin, myosin, dynein, clathrin.
Lignin:
A polymer of aromatic alcohols that makes up 25 percent of wood.
Limit of resolution:
The minimum distance that must separate two points so that their image can be resolved. See Resolving limit.
Limulus amebocyte lysate:
Product of white blood cells of the horseshoe crab used in an assay for endotoxin.
Lipase:
An enzyme originating in the pancreas which helps to digest fats. Measuring blood levels of lipase will help screen for disease of the pancreas.
Lipemia:
Presence of an abnormally high amount of lipid in the bloodstream, often imparting a turbid or milkey appearance to serum or plasma due to high triglyceride content. The turbidity is often graded on a scale of 1+ to 4+.
Lipid:
Any of a heterogeneous group of fats and fatlike substances characterised by being water insoluble and being extractable by nonpolar (or fat) solvents such as alcohol, ether, chloroform, benzene, etc. All contain as a major constituent aliphatic hydrocarbons. The lipids, which are easily stored in the body, serve as a source of fuel, are an important constituent of cell structure and serve other biological functions. Lipids may be considered to include fatty acids, neutral fats, waxes and steroids. Glycolipids, lipoproteins and phospholipids comprise the compound lipids.
Lipopolysaccharide:
A molecule found in the outer membrane of gram negative bacteria, responsible for allergic reactions in some animals. Carbohydrate-lipid complex; integral substance in gram-negative cell walls. Also known as "endotoxin."
Liposome:
Small closed vesicle consisting of a single lipid bilayer.
Lipoteichoic acid:
Teichoic acids attach to lipids in the cytoplasmic membrane rather than to peptidoglycan. Lipoteichoic acids help some bacteria to attach to inanimate objects and to other organisms.
Liver:
A large abdominal organ that plays a critical role in digestion and metabolism.
Logarithmic phase or log phase:
Period of maximal growth rate of a microorganism in a culture medium.
Low density lipoprotein cholesterol (LDLC):
The protein-lipid combination that transports the major amount of the cholesterol in the blood. While LDLC helps in synthesis of bile acid and steroid hormones, elevated blood levels of LDLC (the "bad" cholesterol) have been linked to heart disease because it carries the cholesterol through the blood to the cells.
Low passage cell line:
Cell culture used for virus isolation that is sensitive to the virus only after the cells have been subcultured (passaged) between 20 and 50 times; further passages result in cell with lower affinity for the virus.
LPA:
Latex particle agglutination.
LPS:
Lipopolysaccharide; lipopolysaccharides found in the outer membrane of gram negative bacteria. See endotoxin.
L/S ratio:
The L/S ratio is the numeric ratio of lecithin to sphingomyelin levels found in amniotic fluid. The measurement of these phospholipids in amniotic fluid is commonly performed by TLC, and the ratio is used to assess fetal lung maturity. L/S values greater than 2 are rarely associated with neonate RDS (respiratory distress syndrome); L/S ratios of less than 2 indicate increased risk of RDS. See RDS.
Lumen:
The cavity inside a tubular or hollow organ (blood vessel, intestine, uterus).
Lupus erythematosus:
Skin disease in which there are red scaly patches, especially over the nose and cheeks. May be a symptom of systemic lupus erythematosus.
Lutinizing hormone (LH):
A glycoprotein hormone secreted from the anterior pituitary gland that controls several aspects of reproductive function.
Lymph nodes:
Small bean-shaped structures scattered along the vessels of the lymphatic system. The lymph nodes produce white blood cells and filter bacteria and cancer cells that may travel through the system.
Lymphocytes:
Cells derived from the lymphatic system which are involved in the immune response, specifically B-cells and T-cells.
Lyngbya:
A filamentous, nonmotile cyanobacterium.
Lysis:
Disintegration or dissolution of bacteria, cells or clotted blood.
Lysogeny:
Process by which a viral genome is integrated into that of its host bacterium.
Lysogen:
A cell that carries a provirus.
M-protein:
A protein on the surface of the bacterium Streptococcus pyogenes which helps it attach to host tissue.
MAC:
MacConkey (agar plate), a selective media which supports growth of many Gram negative enteric bacteria and excludes growth of most Gram positive bacteria.
Macroconidia:
Large, usually multiseptate, club- or spindle-shaped fungal spores.
Macrocytes:
Cells which are abnormally large, especially red blood cells.
Macrophage:
A large ameboid-like cell generally found in the reticulo-endothelial system. Involved in phagocytosis and in the immune response.
Macrovascular Disease - Large Vessel Disease:
Atherosclerosis involving the coronary, cerebrovascular, and peripheral vessels. Occurs at an earlier age and with greater frequency in those with diabetes than it does in
nondiabetic individuals.
Magnesium (Mg):
An essential element which influences many enzymes needed to produce cellular energy and nerve and muscle message transmission. It affects nervous, muscular and cardiovascular systems. Magnesium is found mainly in bone, also in muscle and other tissues: deficiency can lead to neuromuscular and central nervous system irritability, muscle twitches and
weakness. Magnesium excess has been found to result in mental depression and cardiac arrest.
Major histocompatibility complex (MHC):
The set of gene loci specifying major histocompatibility antigens. A genetic complex of vertebrates consisting of around 100 genes including the extremely polymorphic cell surface molecules (antigens) called HLA in humans, H2 in mice, RLA in rabbits, RT 1 in rats, DLA in dogs, SLA in pigs, etc. These molecules provide an immunological marker for selfness and a genetic self-identity to the individual. This information is used in mate choice, union of gametes, maintenance of pregnancy, and immune response against nonself (including a transplanted graft). These molecules are the most polymorphic ones in vertebrates. The polymorphism arises from point mutations not at an unusually higher rate than other genes, and mainly from interallelic gene conversion events. The polymorphism is maintained through pathogen and non-pathogen driven mechanisms via heterozygous advantage (overdominant selection) and negative frequency dependent selection. A 3.6 Mb long human MHC haplotype and the 92 kb chicken MHC have been totally sequenced.
Malabsorption syndrome:
A variety of conditions in which digestion and absorption in the small intestine are impaired. Multiple causes including lymphoma, amyloid and other infiltrations, Crohn's disease, gluten sensitive enteropathy and the sprue syndrome in which the villi atrophy for unknown reasons.
Malassezia furfur:
A fungus belonging to the class Deuteromycetes which is responsible for tinea versicolor, a pigmented fungal infection of the skin on the torso and upper legs.
Malignant tertian malaria:
Malaria caused by Plasmodium falciparum.
Malignant tumor:
A tumor which is cancerous.
Malnutrition:
Faulty or inadequate nutrition. Under nourishment.
Mammogram:
A low voltage X-ray photograph of the breast. It allows early detection of malignant or benign tumors and other microcalcification-containing lesions.
Mass spectrometry:
Method for determining composition of a substance by observing its volatile products during disintegration and comparing them with known standards.
Mast cell:
Resident cell of connective tissue that contains many granules rich in histamine and heparin sulphate. Release of histamine from mast cells is responsible for the immediate reddening of the skin in a weal and flare response. Very similar to basophils and possibly derived from the same stem cells. Two types of mast cells are now recognized, those from connective tissue and a distinct set of mucosal mast cells, the activities of the latter are T-cell dependent.
Mastication:
Chewing.
Maternal recognition of pregnancy:
A process by which the early embryo signals to the corpus luteum of its mother to prevent death of the corpus luteum and subsequent fall in progesterone concentrations.
MBC:
Minimum bactericidal concentration.
Meconium:
Pasty greenish mass in intestine of fetus; made up of mucus, desquamated cells, bile, and such.
Media, differential:
Media that permit ready recognition of a particular organism or group of organisms by virtue of facilitating recognition of a natural product of the organism being sought or by incorporating an appropriate substrate and indicator system so that organisms possessing certain enzymes will be readily recognized.
Media, enrichment:
Media, usually liquid, that favor the growth of one or more organisms while suppressing most of the competing flora in a specimen with a mixture of organisms.
Media, selective:
Culture media that contain inhibitory substances or unique growth factors such that one particular organism or group of organisms is conferred a real advantage over other organisms that may be found in a mixture. Efficient selective media will select out only the organism or organisms being sought, with little or no growth of other types of organisms.
Media, supportive:
Culture media that provide adequate nutrition for most nonfastidious microorganisms and that permit each organism to grow normally without conferring any special advantage to one organism over another.
Mediastinum:
Space in the middle of the chest between the medial surfaces of the two pleurae.
Megaloblastic Anemia:
Anemia in which megaloblasts are found in the blood; usually due to a deficiency of folic acid or vitamin B12.
Meiosis:
A specialised form of nuclear division in which there two successive nuclear divisions (meiosis I and II) without any chromosome replication between them. Each division can be divided into 4 phases similar to those of mitosis pro, meta, ana and telophase). Meiosis reduces the starting number of 4n chromosomes in the parent cell to n in each of the 4 daughter cells. Each cell receives only one of each homologous chromosome pair, with the maternal and paternal chromosomes being distributed randomly between the cells. This is vital for the segregation of genes. During the prophase of meiosis I (classically divided into stages: Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis), homologous chromosomes pair to form bivalents, thus allowing crossing over, the physical exchange of chromatid segments. This results in the recombination of genes. Meiosis occurs during the formation of gametes in animals, which are thus haploid and fertilization gives a diploid egg. In plants meiosis leads to the formation of the spore by the sporophyte generation.
Meleney's ulcer:
A chronic undermining ulcerative lesion of the subcutaneous tissue, usually caused by streptococcal infection.
Memory cells:
B-lymphocytes ot T-lymphocytes that have been sensitized to a specific antigen and which can mount an immune response more rapidly than unsensitized lymphocytes involved in a primary immune response. See Anamnestic response.
Meninges (sing. meninx):
The three membranes that cover the brain and spinal cord.
Meningitis:
Inflammation of the meninges, the membranes that cover the brain and spinal cord (e.g., bacterial meningitis).
Merozoite:
Product of schizogonic cycle in malaria that will invade red blood cells.
Mesenchyme:
The embryonic precursor to all connective tissues. Mesenchymal cells differentiate into fibroblasts, adipocytes, endothelial cells, etc.
Mesenteric adenitis:
Inflammation of mesenteric lymph nodes.
Mesentery:
A fold of the peritoneum that connects the intestine with the posterior abdominal wall.
Mesothelium:
A thin layer of flattened cells, derived from mesoderm, that lines body cavities and covers internal organs.
Messenger RNA (mRNA):
It is the first product of the DNA transcription by RNA polymerase. mRNA forms 1-5% of the total cellular RNA. Its molecular weight is generally less than 2x106. At any time, there are about 105 species of mRNA in a cell.
Meta-:
A prefix indicating either 1) change, transformation or exchange, or 2) after, between or next.
Metabolism:
The sum of all the physical and chemical processes by which living organised substance is produced and maintained (anabolism) and also the transformation by which energy is made available for the uses of the organism (catabolism).
Metacentric:
A chromosome structure in which the centromere is roughly equidistant between the two ends.
Metamyelocyte:
An immature neutrophilic granulocyte with a kidney-bean-shaped nucleus or an indent, with the presence of specific granules (neutrophilic, eosinophilic, or basophilic) in the cytoplasm.
Metaplasia:
Change from one type of cell or tissue to another. For example, connective tissue undergoes metaplasia to form cartilage or bone. Columnar epithelial cells can undergo "squamous metaplasia" to form squamous-type epithelial cells in response to chronic irritation.
Metastasis or metastatic:
The spread of an infectious (or other) process from a primary focus to a distant one via the bloodstream or lymphatic system, eg., metastatic carcinoma.
Methane-oxidizing bacteria:
Bacteria that utilize methane as a source of carbon and energy. Examples are Methylobacter and Methylococcus. See Methylotrophs.
Methane-producing bacteria:
Bacteria that release methane. These bacteria belong to the family Methanobacteriaceae. Examples are Methanobacterium, Methanosarcina, and Methanococcus. See Methanogenic bacteria.
Methanogenic bacteria:
Bacteria that generate methane during their metabolism. Same as methane-producing bacteria.
Methylmalonic acid (MMA):
Methylmalonic acid is present in physiological fluids at very low concentrations under normal conditions. In disorders of vitamin B12 metabolism or primary deficiencies in methylmalonic acid metabolism, the concentration of this metabolite becomes significantly elevated. Methylmalonic aciduria results from a defect in the adenosylcobalamin-dependent mitochondrial enzyme methylmalonyl-CoA-mutase, involved in branched-chain amino acid metabolism. Methylmalonic acid levels in plasma are often measured by using isotope dilution and gas chromatography/mass spectroscopy. Reference ranges: Plasma: 0.07-0.27 mM, B12 Deficiency: 0.27-200 mM; Random urine: 0.4-2.5 mol/mmol creatinine. See Vitamin B12.
Methylotrophs:
Bacteria that obtain their energy by metabolizing methane or methanol. These bacteria belong to the family Methylomonadaceae.
MHA-TP:
Microhemagglutination test for antibody to Treponema pallidum.
MIC:
Minimum inhibitory concentration. Minimum inhibitory concentration of a chemical that inhibits the growth of an organism.
Michaelis Menten equation:
Equation derived from a simple kinetic model of enzyme action that successfully accounts for the hyperbolic adsorption isotherm relationship between substrate concentration S and reaction rate V. V = Vmax x S/(S + Km), where Km is the Michaelis constant and Vmax is maximum rate approached by very high substrate concentrations.
Microaerobic:
Requiring a partial pressure of oxygen less than that of atmospheric oxygen for growth. New term for "microaerophilic."
Microaerophile, obligate:
Microorganism that grows only under reduced oxygen tension and cannot grow aerobically or anaerobically.
Microaerophiles:
Organisms that require reduced concentrations of oxygen, and elevated concentrations of carbon dioxide, in order to grow.
Microaerophilic:
See "microaerobic."
Microcalorimetry:
Study of microcalories, a measure of heat production.
Micrococcus luteus:
Gram positive, spherical, nonmotile, aerobic, oxidase positive bacterium.
Microconidia:
Small, single-celled fungal spores.
Microcytes:
Cells which are abnormally small, especially red blood cells.
Microfilaria:
Embryos produced by filarial worms and found in the blood or tissues of individuals with filariasis.
Microorganism:
Any microscopic single-celled organism or microscopic multicellular animal or mold: bacteria, protozoans, algae, fungi, and metazoans. May also be used when referring to viruses. "Infectious agent" is used when referring to viruses, viroids, and prions.
Microsporum:
A fungus belonging to the Deuteromycetes which is responsible for ringworm of the face, arms, and body.
Microvascular Disease - Small Vessel Disease:
Microvilli:
Thin cylindrincal projections of the plasma membrane that are particularly abundant on epithelial cells in the small intestine.
A group of disorders related to disease of small blood vessels particularly retinopathy and nephropathy characteristic of diabetes mellitus.
Miliary:
Of the size of a millet seed (0.5 to 1.0 mm); characterized by the formation of numerous lesions of the above size distributed rather uniformly throughout one or more organs.
Mineral corticoid:
A type of steroid hormone synthesized and secreted from the adrenal cortex. The major mineralocorticoid is aldosterone.
Minimal medium:
A medium in which all the constituents and their concentrations are known. Also known as a defined medium. A minimal medium generally consists of salts that supply phosphate, nitrate (or ammonium), sulfate, magnesium, and trace elements, and a carbon source such as glucose. See Complex medium.
Minimum bactericidal concentration (MBC):
The minimum concentration of antimicrobial agent needed to yield a 99.9% reduction in viable colony forming units of a bacterial or fungal suspension.
Minimum inhibitory concentration (MIC):
The minimum concentration of antimicrobial agent needed to prevent visually discernible growth of a bacterial or fungal suspension.
Mitosis:
A method of indirect division of a cell, consisting of a complex of various processes, by means of which the two daughter nuclei normally receive identical complements of the number of chromosomes characteristic of the somatic cells of the species. Mitosis, the process by which the body grows and replaces cells, is divided into four phases. 1. Prophase: formation of paired chromosomes, disappearance of nuclear membrane, appearance of the achromatic spindle, formation of polar bodies. 2. Metaphase: arrangement of chromosomes in the equatorial plane of the central spindle to form the monaster. Chromosomes separate into exactly similar halves. 3. Anaphase: the two groups of daughter chromosomes separate and move along the fibres of the central spindle, each toward one of the asters, forming the diaster. 4. Telophase: the daughter chromosomes resolve themselves into a reticulum and the daughter nuclei are formed, the cytoplasm divides, forming two complete daughter cells.
NOTE: the term mitosis is used interchangeably with cell division, but strictly speaking it refers to nuclear division, whereas cytokinesis refers to division of the cytoplasm. In some cells, as in many fungi and the fertilized eggs of many insects, nuclear division occurs within the cell unaccompanied by division of the cytoplasm and formation of daughter cells.
Mixed acid fermentation:
A fermentation in which a mixture of acids, alcohols, and gases is released. Carried out by bacteria such as Escherichia coli. Tested for by the methyl red test.
Mixed culture (pure culture):
More than one organism growing in or on the same culture medium, as opposed to a single organism in pure culture.
MN blood group antigens:
A pair of blood group antigens governed by genes that segregate independently of the ABO locus. The alleles are codominant and there are three types MM, NN and MN. Glycophorin has M or N activity and this is associated with oligosaccharides attached to the amino terminal portion of the molecule. M type glycophorin differs from N type in amino acid residues 1 and 5, although the antigenic determinants are associated with the carbohydrate side chains.
Molecule:
A compound, composed of 2 or more atoms chemically or covalently bonded together.
Monoarticular:
Occurring in only one joint.
Monoclonal antibodies:
Specific antibodies which react with a single epitope - derived from a single (mono) clone of plasma cells. It may be produced in large quantities, usually for use against a specific antigen, for diagnostic and possibly therapeutic use.
Myelomas are cancerous plasma cells with the unique property of being able to proliferate indefinitely in culture. In contrast, normal B cells die within 1-2 weeks of being placed into Petri dishes. In 1975, Kohler and Milstein developed a somatic cell hybridization technique that allowed them to fuse a myeloma cell with an antibody-secreting B cell from an immunized mouse, thereby combining the growth potential of myeloma cells with the predetermined antibody specificity of normal B cells. The resultant hybridoma secreted a monoclonal antibody.
Monocyte:
A monocyte is a mononuclear phagocytic leukocyte circulating in blood that will later migrate into tissue and differentiate into a macrophage.
Monolayer:
A confluent layer of tissue culture cells one cell thick.
Morbidity:
The number of diseased individuals existing during a given period or during a particular incident.
Mortality:
The number of deaths occurring during a given period or during a particular incident.
Morula:
A stage during early embryogenesis in which the embryo resembles a mulberry (roughly 16 to 32 cells).
Mosaic (mosaicism):
In genetics, an animal that has more than one genetically-distinct populations of cells derived from a single zygote; as most commonly used, the different populations of cells have differing numbers of chromosomes.
Motilin:
A peptide hormone secreted from the small intestine that appears to stimulate intestinal smooth muscle contractions in periods between meals.
MOTT:
Mycobacteria other than Mycobacterium tuberculosis.
Mucins:
A family of large glycoproteins that are the major constituent of mucus.
Mucopeptide:
See Peptidoglycan.
Mucopurulent:
Term used to describe material containing both mucus and pus (e.g., mucopurulent sputum).
Mucosa:
A mucous membrane.
Multiple myeloma:
Malignancy involving antibody-producing plasma cells.
Murein:
See Peptidoglycan.
Murine:
Pertaining to or derived from rats or mice.
Mutagen:
Physical or chemical agents that induce mutations. See also Carcinogen.
Mutualism:
A symbiotic association between two organisms in which both benefit.
Myasthenia:
Muscular debility, any constitutional anomaly of muscle.
Myasthenia gravis:
The characteristic feature of the disease is easy fatigue of certain voluntary muscle groups on repeated use. Muscles of the face or upper trunk are especially likely to be affected. In most and perhaps all cases due to the development of autoantibodies against the acetylcholine receptor in neuromuscular junctions. Immunization of mice or rats with this receptor protein leads to a disease with the features of myasthenia.
Mycelium (pl. mycelia):
The mass of intertwined, branched, filamentous growth of hyphae associated with many fungi.
Mycetoma:
Chronic infection, usually of feet, caused by various fungi or by Nocardia or Streptomyces, resulting in swelling and sinus tracts; pulmonary mycetoma is a mass of fungal hyphae ("fungus ball) growing in a cavity formed during previous tuberculosis infection or other pathological condition.
Myco-:
Having to do with fungi. Many bacteria showing filamentous and/or branching growth originally were thought to be related to fungi, or were mistaken for fungi, and consequently contain the prefix referring to fungi in their genus designation.
Mycobacteria:
One group of gram positive, rod-shaped, nonmotile, aerobic, acid-fast, slow-growing bacteria.
Mycoses:
Diseases caused by fungi (e.g., dermatomycosis, fungal infection of the superficial skin).
Myocarditis:
Inflammation of the heart muscle.
Mycobacterium leprae:
Causes leprosy
Mycobacterium tuberculosis:
Causes tuberculosis.
Mycology:
The study of fungi.
Mycoplasma pneumoniae:
Gram negative, pleiomorphic (spherical, filamentous, and branched), nonmotile, anaerobic, sterol-requiring, bacterium that lacks a cell wall. It causes primary atypical pneumonia.
Mycoplasmas:
A group of bacteria that lack cell walls.
Mycorrhiza:
A mutualistic association between a fungus and plant roots.
Mycosis:
A fungal infection.
Mycotoxin:
A fungal toxin.
Myelocyte:
An immature neutrophilic granulocyte characterized by an eccentrically located round nucleus and specific granules--neutrophilic, eosinophilic, or basophilic.
Myocardial infarction:
A term used to describe irreversible injury to heart muscle. Synonym: heart attack.
Myositis:
Inflammation of a muscle, sometimes caused by infection as in pyomyositis, an infection caused by Staphylococcus aureus that leads to small abscesses within the muscle substance.
Myxedema:
A severe form of thyroid hormone deficiency.
Myxobacteria:
Gliding bacteria that congregate upon nutrient deprivation and form fruiting bodies. The fruiting bodies contain microcysts, which are more tolerant of high heat, desiccation, and radiation than the vegetative cells. An example of a myxobacterium is Chondromyces crocatus.
Myxomycetes:
A class of fungi known as the plasmodial slime molds. During part of their life cycle, the Myxomycetes exist as flat, macroscopic cells, as much as 5 cm in diameter, with numerous diploid nuclei. This slimelike cell is called a plasmodium. Upon nutrient deprivation and/or exposure to light, the plasmodium develops into numerous fruiting bodies, which contain spores with a single nucleus. The spores germinate into a vegetative cell that develops into a plasmodium. The plasmodium is ameba-like in that it is able to phagocytize bacteria and other small single-celled organisms.
N terminal:
Synonym for amino terminus. The end of a polypeptide that carries a free amino group. The first amino acid in a peptide or protein is called the amino terminal or N-terminal amino acid.
Nares:
External openings of nose (i.e., nostrils).
Nasopharyngeal:
Pertaining to the part of the pharynx above the level of the soft palate.
Necrosis:
Pathological death of a cell or group of cells.
Necrotic tissue:
Dead tissue.
Necrotizing fasciitis:
A very serious, painful infection involving the fascia (membranous covering) of one or more muscles; may spread widely in short periods of time since there is no anatomic barrier to spread in this type of infection.
Negative feedback:
A mechanism commonly used for control of secretion in the endocrine system.
Negri bodies:
Characteristic virally-induced inclusions present in rabies-infected brain cells.
Nematodes:
Wormlike animals, often known as roundworms.
Neisseria:
Gram negative, spherical, nonmotile, aerobic, oxidase positive bacteria.
Neisseria gonorrhoeae:
Causes the venereal disease gonorrhea.
Neisseria meningitidis:
Causes an inflammation of the meninges, known as meningitis.
Neonatal:
First 4 weeks after birth.
Neoplasia:
New cell growth; cancer.
Nephelometry:
Determination of the degree of turbidity of a fluid by light scatter.
Nephritis:
Inflammation of the kidney, a focal or diffuse proliferative or destructive process which may involve the glomerulus, tubule or interstitial renal tissue.
Nephropathy:
A disease of the kidneys. Commonly accompanies later stages of diabetes mellitus; it begins with hyperfiltration, renal hypertrophy, microalbuminuria, and hypertension.
Nephrotic syndrome:
A type of nephritis that is characterised by low serum albumin, large amount of protein in the urine and swelling (edema). Swelling, weight gain, high blood pressure and anorexia are key features. Nephrotic syndrome can be seen with a number of illness that cause damage to the kidney glomerulus. Examples include diabetes, hereditary disorders, lupus, multiple myeloma, amyloidosis, glomerulonephritis, minimal change disease and membranous glomerulonephritis.
Nernst equation:
An equation defining the equilibrium potential of an electrode. The potential is the sum of the standard electrode potential and a correction term for the deviation from unit concentrations of the reactant and the product of the electrode reaction.
The correction term is the product of the "Nernst slope" and the logarithm of the ratio of the concentrations (strictly speaking, activities) of the oxidized species and the reduced species, according to the equation: E = E0 + S log(Cox/Cred). At room temperature, the Nernst slope is 0.05916 volt divided by the number of electrons transferred during the reaction. E.g., for a simple metal deposition/dissolution reaction the slope is 0.05916 for a single charged metal cation, 0.00296 volt for a double charged ion, etc.
Neural tube:
The tubular embryonic tissue from which the brain and spinal cord develop. Very serious congenital defects result from failure of this tube to close during the process of growth and differentiation.
Neural tube defect:
A congenital defect of the central nervous system, including the spinal cord, skull and brain, resulting from failure of the neural tube to properly close during fetal development. Defects may include absence of the skull, and protrusions of the brain or spinal cord. Most such defects can be detected before birth by determination of amniotic fluid or blood levels of alpha-fetoprotein and by ultrasonic scanning.
Neuritis:
Inflammation of a nerve; most often not caused by an infectious agent.
Neuropathy:
A functional disturbance or pathological change in the peripheral nervous system, the most common kind of chronic symmetrical sensory polyneuropathy affecting first the nerves
of the lower limbs and often affecting autonomic nerves, characteristic of diabetes mellitus.
Neurophysin:
A carrier protein co-expressed with the peptide hormones antidiuretic hormone and oxytocin.
Neurotrophic:
Having a selective affinity for nerve tissue. Rabies is caused by a neurotrophic virus.
Neutrophil:
A granulocyte, a white blood cell. A leukocyte with characteristic neutrophilic (pale-pink) granules when Wright stained. White blood cells involved in phagocytosis, in which the granules stain poorly with basic and acidic dyes.
NFB:
Glucose nonfermenting gram-negative bacteria.
NGU:
Nongonococcal urethritis.
Nick translation:
Use of enzymes to break DNA and repolymerize small sections of the molecule, usually for purposes of labeling the DNA with a radioactive nucleotide.
Nitrification:
The conversion of ammonium to nitrate by soil microorganisms.
Nitrate-reducing bacteria:
Bacteria that convert nitrate to nitrite and nitrogen gas. Examples are Pseudomonas and Thiobacillus. See Denitrifying bacteria.
Nitrobacter:
Gram negative, rod-shaped, nonmotile, aerobic, ammonium-oxidizing, carbon dioxide requiring bacterium. Chemolithotroph. Nitrifying bacterium.
Nitrogen cycle:
A cyclic series of chemical reactions carried out by various microorganisms in which molecular nitrogen is reduced to ammonium, the ammonium is converted to nitrite, the nitrite is further oxidized to nitrate, and the nitrate is reduced back to molecular nitrogen.
Nitrogen fixation:
The reduction of atmospheric molecular nitrogen to ammonium by enzyme nitrogenase, and the incorporation of the ammonium nitrogen into organic compounds.
Nitrogen-fixing bacteria:
Bacteria that are able to reduce molecular nitrogen to ammonium and then assimilate (fix) the nitrogen into organic compounds. Examples include Azotobacter, Klebsiella, Rhizobium, Anabaena, and Nostoc.
Nitrosococcus:
Gram negative, spherical, nonmotile, aerobic, ammonium-oxidizing, carbon dioxide-requiring bacteria. Chemolithotroph. Nitrifying bacteria.
Nitrosomonas:
Gram negative, rod-shaped, nonmotile, aerobic ammonium-oxidizing, carbon dioxide-requiring, bacterium. Chemolithotroph. Nitrifying bacterium.
NMR:
See nuclear magnetic resonance.
Nocardia asteroides:
Gram positive, acid-fast, rod-shaped, mycelium-forming, nonmotile, aerobic bacterium. Causes pulmonary cutaneous, and subcutaneous infections. May become systemic and infect various organs.
Nodule:
A small mass of cells found on the roots of legumes in which nitrogen-fixing bacteria reside.
Nondisjunction:
Failure of homologous chromosomes (at meiosis) or sister chromatids (at mitosis) to segregate properly, resulting in unequal distribution to daughter cells. A common error leading to chromosomal disease.
Nonisotopic immunoassay:
A method of identifying and measuring substances, such as hormones, by utilizing antigen-antibody reactions without the use of radioactive material (isotopes) for labeling. Such assays may employ other kinds of reaction-monitoring signals.
Nonphotochromogens:
Slow-growing, nonpigmented mycobacteria.
Nonsporulating:
Does not produce spores.
Nonthyroidal illness (NTI):
Illness that causes abnormal thyroid function test results in the absence of thyroid disease.
Norepinephrine:
A catecholamine secreted from the adrenal medulla and from certain sympathetic neurons.
Nosocomial:
Pertaining to or originating in the hospital, said of an infection not present or incubating prior to admittance to the hospital, but generally occurring 72 hours after admittance, the term is usually used to refer to patient disease, but hospital personnel may also acquire nosocomial infection. See iatrogenic.
Nosocomial infection:
An infection obtained while a patient or worker is in a hospital.
Nostoc:
A cyanobacterium.
Nuclear magnetic resonance (NMR):
The use of magnetic fields and radio waves (instead of the X-rays employed in the CT scan) to visualize body structures and how they function. The powerful magnet, large enough to enclose the body, forces the atomic nuclei in most material such as soft tissue to align themselves with the magnetic field. Radio waves are aimed at the selected area to
excite the atoms which, when the waves are stopped, emit signals that are converted to computer-generated pictures. NMR is used to detect diseases of soft tissues, heart, brain, and spinal cord. NMR is also called magnetic resonance imaging (MRI).
Nucleic acid hybridization:
Process by which the single-stranded probe unites with complementary DNA in an unknown sample.
Nucleic acid probe:
Piece of labeled single-stranded DNA used to detect complementary DNA in clinical material or a culture and thus to specifically identify the presence in these materials of an organism identical to that used to make the probe.
Nucleocapsid:
Name of viral particle that includes virus nucleic acid core enclosed in the protein capsid coat.
Nucleophile:
A substance which donates a pair of electrons in a reaction.
Nucleophilic substitution:
An overall reaction in which a nucleophile reacts with a compound displacing another nucleophile. Such reactions commonly occur in aliphatic chemistry. If the reaction is unimolecular they are known as SN1 reactions; for reactions which are bimolecular, they are known as SN2 reactions.
Nucleoside:
Purine or pyrimidine base linked glycosidically to ribose or deoxyribose, but lacking the phosphate residues that would make it a nucleotide. Ribonucleosides are adenosine, guanosine, cytidine and uridine. Deoxyribosides are deoxyadenosine, deoxyguanosine, deoxycytidine and deoxythymidine (the latter is almost universally referred to as thymidine).
Nucleotide:
The monomeric unit (phosphate esters of nucleosides) that makes up the DNA or RNA, formed by a phosphate group, a pentose and one of the nitrogenous bases (A, T/U, C, G). Nucleotides in RNA are adenylate, guanylate, cytidylate and uridylate; in DNA, they are (d)adenylate, (d)guanylate, (d)cytidylate and thymidylate. The metabolic precursors of nucleic acids are monoesters with phosphate on carbon 5 of the pentose (known as 5' to distinguish sugar from base numbering). Many other structures, such as adenosine 3'5' cyclic monophosphate (cAMP) and molecules with 2 or 3 phosphates are also called nucleotides.
Nucleus (pl. nuclei):
Membrane-enclosed organelle of eukaryotic cells containing the cell's genetic information (DNA).
O & P:
Ova and parasites; concentration, preservation and examination techniques applied chiefly to recovery of parasitic amoeba, cysts, ova and their trophozoites from feces.
O-antigen:
The outer portion of the polysaccharide that extends from the lipopolysaccharide found in the outer membrane of gram negative bacteria.
Objective lense:
The lens or system of lenses in a microscope (or telescope) that is nearest to the object under examination.
Ocular:
Ocular is an alternative name for an eyepiece that has been widely used. Eyepieces work in combination with microscope objectives to further magnify the intermediate image so that specimen details can be observed. Of, pertaining to or affecting the eye or an eyepiece or eye lense.
O-F:
Oxidation-fermentation medium.
Oil immersion microscopy:
Use of immersion oil to fill the space between the slide being studied and the special objective of the microscope; this keeps the light rays from dispersing and provides good
resolution at high magnification (total magnification of l000x).
Oligotroph:
An organism that can grow at very low concentrations of nutrients.
Oligotrophic waters:
Bodies of water that are low in nutrients.
Omentum:
Sections of peritoneum that extend from the stomach to other abdominal organs and to the abdominal wall.
Onchocerca volvulus:
A parasitic roundworm (nematode) that causes onchocerciasis and is responsible for the disease known as river blindness.
Oncogene:
A gene capable of causing malignant transformation.
Oncogenic:
Possessing the potential to cause normal cells to become malignant; causing cancer.
Oncogenic viruses:
Viruses that can cause cancer.
Oncologist:
A specialist in the treatment of cancer.
One-gene-one-enzyme hypothesis:
The idea that a region of DNA, called a gene, contains the information for making a functional enzyme. It was originally proposed by Beadle and Tatum.
One-step growth curve:
The growth curve shown by viruses that lyse their host cells.
ONPG:
o-nitrophenol-ß-galactopyranoside (ß-galactosidase test).
Ontogeny:
In developmental biology, the ontogeny of the brain refers to the events and processes by which the brain develops to attain its mature form and function.
Oomycetes:
A class of unicellular or filamentous fungi that produce flagellated gametes. The walls contain cellulose rather than chitin. Filamentous forms show nonseptated hyphae.
Operculated ova:
Ova possessing a cap or lid.
Operon:
One or more structural genes controlled by one or more controlling sites. The smallest operon consists of a gene that codes for a polypeptide and a promoter (RNA polymerase binding site is a controlling site).
Opiates:
Drugs containing or derived from opium (a poppy juice) used to relieve pain or induce sleep. They are addictive narcotics.
Opsonization:
A process through which a cell or microbe is treated with opsonin to make it more vulnerable to being engulfed by a phagocyte. Often done simply by incubating particles (e.g. Zymosan) with fresh serum. Opsonize: To facilitate destruction of pathogens by phagocytic ingestion or lysis by complement through the action of adherent antibodies.
Oral glucose tolerance test:
A series blood tests measuring plasma glucose concentration, the first after an 8 to 12 hour fast, then a liquid that contains 75 grams of glucose is ingested, after which
the second blood glucose is measured at 30 minutes, the third at one hour, the fourth at two hours and the fifth at three hours. A diagnosis of diabetes is made if the venous
plasma glucose level is > 200 mg/dl at 120 min. and one other blood glucose level is also > 200 mg/dl.
Orchiectomy:
Surgical removal of the testicles.
Oscillatoria:
A filamentous cyanobacterium.
Osmolality:
The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per kilogram of solvent. The osmolality is directly proportional to the colligative properties of solutions, osmotic pressure, boiling point elevation, freezing point depression and vapour pressure lowering.
Osmolarity:
A measure of solute concentration in aqueous solution. A 1 M solution of a single non-dissociating solute has an osmolarity of 1 osmol. A physiologic osmolarity is about 300 mOs, roughly equivalent to 150 mM NaCl (NaCl dissociates into Na+ and Cl -, both of which contibute to osmolarity).
Osmosis:
Osmosis is the movement of water across a selectively permiable membrane (a membrane through which water but not solutes can flow) caused by a difference in concentration of water on the two sides of the membrane. Water flows into the compartment having higher concentration of solute and in the process generates "osmotic pressure."
Osmotic pressure:
The pressure required to prevent the influx of water into a volume that is hypertonic. The internal water pressure on the cell membrane and wall due to the influx of water into the cell because of a hypotonic environment.
Osteomalacia:
A condition marked by softening of the bones (due to impaired mineralization, with excess accumulation of osteoid), with pain, tenderness, muscular weakness, anorexia and loss of weight, resulting from deficiency of vitamin D and calcium.
Osteomyelitis:
Inflammation of the bone and the marrow.
Otitis:
Inflammation of the ear from a variety of causes, including bacterial infection; otitis media: inflammation of the middle ear.
Ovalocyte:
An abnormal red cell that is egg shaped or elliptical (synonymous with elliptocyte).
Ovine:
Pertaining to or derived from sheep.
Oxidation:
1) The removal (or loss) of electrons (or electron density) from an atom, most commonly due to addition of oxygen or removal of hydrogen from a molecule. The opposite of reduction. 2) A metabolic pathway of microorganisms that involves use of oxygen as a terminal electron acceptor. This type of reaction occurs in air.
Oxidation-reduction potential:
Electromotive force exerted by a nonreacting electrode in a solution containing the oxidized and reduced forms of a chemical, relative to a standard hydrogen electrode; the more negative the value, the more anaerobic conditions are.
Oxidative phosphorylation:
Occurs when electrons and protons from oxidized substrates are used to create a proton gradient across a membrane, and this proton gradient is used to power the synthesis of ATP from ADP and inorganic phosphate. See Substrate phosphorylation and Photophosphorylation.
Oxytocin:
A peptide hormone secreted from the posterior pituitary that plays an important role in birth, lactation and maternal behavior.
Packed cell volume (PCV):
Measurement of the proportion of the blood occupied by the red blood cells. Normal values are 40-54% in males, 35-47% in females. See Hematocrit.
Pancreas:
An abdominal organ that produces exocrine secretions (digestive enzymes and bicarbonate) for delivery to the small intestine, and is a source of the hormones insulin and glucagon that are important in regulating glucose metabolism.
Pancreatitis:
Acute or chronic inflammation of the pancreas, which may be asymptomatic or symptomatic and which is due to autodigestion of a pancreatic tissue by its own enzymes. It is caused most often by alcoholism or biliary tract disease, less commonly it may be associated with hyperlipemia, hyperparathyroidism, abdominal trauma (accidental or operative injury), vasculitis or uremia.
Pancytopenia:
A depression of each of the normal bone marrow elements (white cells, red cells, and platelets) in the peripheral blood.
Pandemic:
Epidemic over a wide geographical area, or even worldwide.
Panel testing:
A laboratory procedure in which a series of tests is performed on one specimen, usually related to a single condition or disease, or for differential diagnosis.
Para-:
Prefix meaning beside, as the parathyroid gland is beside the thyroid gland; or opposite, as the chlorine atoms of paradichlorobenzene are attached to opposed carbon atoms of the benzine ring.
Parabiosis:
A surgical technique in which the vascular systems of two individuals are joined together.
Paracellular:
Transport across a sheet of cells by passage beside or between cells. In contrast to transcellular transport.
Paracentesis:
Surgical transcutaneous puncture of the abdominal cavity to aspirate peritoneal fluid.
Paracrine:
The activity of a hormone or growth factors that binds to and affects neighboring cells.
Paramecium:
A ciliated protozoan.
Parasite:
An organism that lives on or within and at the expense of another organism.
(for example Giardia).
Parathyroid glands:
Endocrine glands located close to the thyroid glands that secretes parathyroid hormone.
Parathyroid hormone:
A protein hormone secreted from the parathyroid gland in response to low concentrations of calcium in blood.
Parathyroid hormone-related protein:
A family of protein hormones that have significant sequence identity with parathyroid hormone, but much more diverse actions.
Parenchyma:
Meaning "anything that is poured in beside". If you consider an organ having a scaffolding of blood vessels, lymphatic vessels, nerves and connective tissue (i.e. stroma), all the other cells that are "poured in" around the scaffolding is parenchma. The parencyma is the distinctive part of the organ.
Parenteral:
Route of administration of a drug other than by mouth; includes intramuscular and intravenous administration.
Parietal:
Pertaining to the walls of a cavity. The abdomen is lined with parietal peritoneum.
Parietal cell:
An acid-secreting cell in the epithelium of the stomach.
Paronychia:
Purulent inflammation about margin of a nail.
Parotid gland:
One of the salivary glands.
Parotitis:
Inflammation of the parotid gland, the largest of the salivary glands; mumps is the most common cause of this.
Paroxysm:
Rapid onset (or return) of symptoms; term usually applies to cyclic recurrence of malaria symptoms, which are chills, fever, and sweating.
Partial pressure:
The independent pressure exerted by a component gase in a mixture.
Parturition:
The act of giving birth.
Passive diffusion:
See Diffusion.
Pasteurization:
The heating of material such as wine and milk to temperatures below the boiling point, in order to kill spoilage organisms or disease-causing organisms. Thermoduric organisms survive pasteurization. See Sterilization and Appertization.
Pathogenesis:
The mechanisms and changes involved in development of a disease state.
Pathogenic:
Producing disease.
Pathognomonic:
A sign or set of symptoms that characterize a specific disease and allow good differentiation from other diseases. Example: elevated blood glucose levels are pathognomonic for diabetes.
Pathological:
Caused by or involving a morbid condition, as a pathological state.
PCP:
See phencyclidine hydrochloride.
PCR:
Polymerase chain reaction.
Pectin:
A polymer of D-galacturonate.
Pediculus humanus:
Body louse. Vector of the bacterium that causes relapsing fever, Borrelia recurrentis.
Pediococcus:
Gram positive, spherical, nonmotile, microaerotolerant, anaerobic bacterium with complex growth requirements, often arranged in tetrads.
Pellicle:
(1) A film of microorganisms on the top of a broth. (2) An envelope that surrounds a microorganism. (3) A convoluted and cytoskeleton-strengthened plasma membrane found in some protozoans.
Pelvic inflammatory disease (PID):
Ascending infection from the vagina or cervix to the uterus, fallopian tubes and broad ligaments: most often caused by bacterial infections of chlamydia and gonorrhea.
Pelvic node dissection:
Removal of possible cancer carrying lymph nodes near the prostate or their evaluation.
Penicillinase:
(ß-lactamase I) Enzyme produced by some bacterial species that inactivates the antimicrobial activity of certain penicillins (e.g., penicillin G, a ß-lactam).
Penicillium:
A fungus belonging to the class Deuteromycetes which forms conidia from annellides. Some species produce the antibiotic penicillin.
Pentagastrin:
The C-terminal 5 amino acids of the hormone gastrin.
Pentose:
A 5 carbon monosaccharide.
Pepsin:
A proteolytic enzyme secreted from chief cells in the epithelium of the stomach.
Peptide bond:
An amide bond between the carboxyl group of one amino acid and the alpha-amine group of another amino acid.
Peptidoglycan:
A polysaccharide layer in the walls of most eubacteria, constructed from alternating units of N-acetyl-glucosamine and N-acetyl-muramic acid. Peptidoglycan is also known as murein or mucopeptide.
Peptones:
Derived proteins or mixtures of cleavage products produced by the partial hydrolysis of a native protein either by an acid or by an enzyme. Peptones are readily soluble in water, and are not precipitable by heat, by alkalis, or by saturation with ammonium sulfate.
Percutaneous:
Performed through the skin (e.g., percutaneous bladder aspiration).
Perfect-gas equation:
Boyle's, Charles, and Avogadro's laws may be combined into the Perfect-gas equation: pV=nRT, where p is pressure, V is volume, n is moles, R is the gas constant, and T is temperature. Typical units are pressure is in atmospheres, volume is in liters, R is 0.0820 liter-atmospheres/mole-degree and temperature is degrees Kelvin. The equation may be used to determine a number of physical and chemical properties of gases; eg., pressure, volume, density, weight, molecular weight, molecular formula.
Peri-:
Prefix meaning around. The perinatal period is around the time of birth and a perianal tumor is a tumor situated around the anus.
Pericarditis:
Inflammation of the covering of the heart (pericardium).
Perineum:
The portion of the body bound by the pubic bone anteriorly, the coccyx posteriorly, and the bony prominences (tuberosities) of the ileum on both sides.
Peripheral protein:
A membrane protein which can be isolated from the lipid bilayer with mild to moderate treatments (change in pH, ionic changes). Generally, the protein maintains its function when isolated from the lipid bilayer. See Integral protein.
Periplasmic space:
In gram negative bacteria, the region between the cytoplasmic membrane and the outer membrane of the wall. In gram positive bacteria, the region between the cytoplasmic membrane and the peptidoglycan layer.
Peristalsis:
A pattern of wave-like smooth muscle contractions that propels material through the digestive tube.
Peritoneal cavity:
Space between the visceral and parietal layers of the peritoneum; the serous membrane lining the abdominal cavity and surrounding the contained viscera.
Peritonitis:
Inflammation of the peritoneal cavity, most often caused by bacterial infection.
Permease:
A protein involved in the transport of materials into or out of a cell.
Pernicious Anemia:
A type of megaloblastic anemia due to a deficiency of vitamin B12 that is directly linked to absence of intrinsic factor (IF). Confirmational tests include: serum gastrin, methylmalonic acid, intrinsic factor blocking antibodies, parietal cell antibodies (IgG) and Schilling tests.
Peroxidase:
An enzyme that hastens the transfer of oxygen from peroxide to a tissue that requires oxygen; essential to intracellular respiration.
PET scan:
See Positron emission tomography..
Petechiae:
Tiny hemorrhagic spots in the skin or mucous membranes.
pH:
A logarithmic representation of the concentration of the hydrogen cation, log10[H+]. A solutions whose [H+] = 10-7 has a pH = 7.
Phage:
A bacterial virus.
Pharynx:
The muscular tube between the mouth and posterior nasal cavities and the esophagus.
Phase contrast microscopy:
A simple nonquantitative form of interference micoscopy of great utility in visualising live cells. Small differences in optical path length due to differences in refractive index and thickness of structures are visualised as differences in light intensity.
Phencyclidine hydrochloride (PCP):
An anesthetic agent used in veterinary medicine. Also an illegal hallucinogenic street drug, "angel dust." Its presence may be detected by urine testing.
Phenytoin:
An anticonvulsant drug used to treat seizure disorders including epilepsy, as well as digitalis-induced heartbeat rhythm disturbances. An overdose can have toxic effects. A
blood test can determine the phenytoin level to aid in correct dosing and avoid toxicity.
Phosphatase:
An enzyme that removes a phosphate group from another molecule.
Phosphatide:
The family of phospholipids based on 1, 2 diacyl 3 phosphoglyceric acid.
Phosphatidylglycerol (PG):
Phosphatidylglycerol (PG) is a phospholipid which is undetectable in amniotic fluid until lung maturity just prior to birth. The RDS risk is about 2% if PG is present. PG assay by latex agglutination is fast and relatively contaminant-resistant. It is not widely accepted as a replacement for L/S ratio, but it provides useful information and can be used if an L/S is not available. See RDS.
Phosphorus (P):
An element required for bone growth and metabolic energy. Stored in teeth and bones, mainly in combination with calcium, phosphorus blood levels are affected by parathyroid, blood, and bone diseases.
Phosphorylation:
A chemical reaction in which a phosphate group is covalently bonded to another molecule.
Photochromogens:
Mycobacteria that produce pigment after exposure to light but whose colonies remain buff-colored in the dark.
Photon:
A unit or particle of radiant or light energy. Photons have no electric charge. Gamma and X-rays may be referred to as photons.
Photophosphorylation:
The synthesis of ATP using energy derived from light. See Oxidative phosphorylation.
Photosynthesis:
The process that uses light to generate energy (ATP) and reducing power (NADPH), and that uses ATP and NADPH to fix carbon dioxide.
Phycomycosis:
Serious infection involving fungi of the zygomycete group, often beginning with necrotic lesions in the nasal mucous or palate but rapidly spreading to involve other tissues. Seen in immunocompromised patients.
Phytophthora infestans:
A fungus belonging to the class Oomycetes which causes late blight of potato.
PID:
Pelvic inflammatory disease.
Pili:
Structures in bacteria similar to fimbriae that participate in bacterial conjugation and transfer of genetic material.
Pilonidal cyst:
Hair-containing cyst in the skin or subcutaneous tissue, often with a sinus tract, commonly in the sacrococcygeal area.
Pipettes:
Calibrated devices used for liquid volume measurement and delivery.
Pitocin:
Another name for the hormone oxytocin, usually applied to its use as a drug.
Pituitary:
A bi-lobed endocrine gland located at the base of the brain that secretes several critical protein and peptide hormones for the regulation of other endocrine glands, including the secretion of TSH for stimulation of the thyroid. The pituitary is regulated by the neurohormones from the hypothalamus.
Plaque:
(1) A clearing in a bacterial lawn due to a virus infection. (2) A virus colony. (3) The bacteria, glycocalyx, food particles, and minerals that form a mat on teeth.
Plasma:
The watery fluid portion of blood in which the corpuscular elements are suspended. It transports nutrients as well as wastes throughout the body. Various compounds — including proteins, electrolytes, carbohydrates, minerals, and fats — are dissolved in it. Plasma specimens are obtained by centrifuging anticoagulated blood.
Plasma cells:
Cells that release antibodies and that develop when a B-lymphocyte is stimulated by antigen.
Plasma membrane:
The membrane that contains the cytoplasm and defines a cell.
Plasmids:
Small, autonomous piece of hereditary material distinct from the main genome. In bacteria, small circular chromosomes 5,000-100,000 base pairs long (5-100 genes).
Extrachromosomal DNA elements of bacteria carrying a variety of determinants that may permit survival in an adverse environment or successful competition with other microorganisms of the same or different species.
Plasmodium:
Flagellated protozoans. See Myxomycetes and Acrasiomycetes.
Plasmodium falciparum:
Causes malaria.
Plasmodium malariae:
Causes malaria.
Plasmodium vivax:
Causes malaria.
Plastids:
Organelles found in eukaryotic cells, such as chromosomes and chromoplasts.
Platelet:
A round or oval disc, 2 to 4 µm in diameter, that is derived from the cytoplasm of the megakaryocyte, a large cell in the bone marrow. Plays an important role in blood coagulation, hemostasis, and blood thrombus formation. Also known as a thrombocyte.
Pleomorphic:
Having more than one form, usually widely different forms, as in pleomorphic bacteria.
Pleura:
The serous membrane enveloping the lung and lining the internal surface of the thoracic cavity.
Pleural effusion:
A collection of fluid (or blood) in the pleural space (in one side of the chest cavity around the lung). May be secondary to trauma, cancer, nephrotic syndrome, kidney disease, pancreatitis, congestive heart failure and cirrhosis.
Pleuropulmonary:
Pertaining to the lungs and pleura.
PMC:
Pseudomembranous colitis.
Pneumonia:
Inflammation of the lungs, primarily caused by infectious agents.
Pneumonia, aspiration:
Pneumonia caused by aspiration of oropharyngeal or gastric contents.
Pneumothorax:
Introduction of air (usually inadvertently) into the pleural space, leading to collapse of the lung on that side.
Polar:
Describes a feature or phenomenon occuring at the end (pole) of an object (such as a planet) or organism (such as an amoeba) or describes a molecule (such as water) that has a permanent electric dipole.
Polarization:
The change of potential of an electrode from its equilibrium potential upon the application of a current.
Polarization microscopy:
Any form of microscopy capable of detecting birefringent objects. Usually performed with a polarizing element below the stage to produce plane polarized light and an analyzer that is set to give total extinction of the background and thus to detect any birefringence.
Poly-:
Prefix meaning many or multiple. Examples: polyploidy refers to having multiple haploid genomes in a cell; polypeptides consist of multiple linked amino acids.
Polyarticular:
Occurring in more than one joint.
Polycythemia:
Increase in the hemoglobin content of the blood, either because of a reduction in plasma volume or an increase in red cell numbers. The latter may be a result of abnormal proliferation of red cell precursors (polycythemia vera, Vaquez Osler disease).
Polycythemia rubra vera:
A condition characterised by enlargement of the spleen and the increased production of red blood cells by the bone marrow. Diagnosis is based on an increased number and volume of red cells. The total number of white blood cells and platelets may also be increased. Treatment will vary according to the age of the patient and severity of the disease. This condition carries an increased risk of developing acute leukemia. The disease usually begins in late middle life and is slightly more common in males.
Polydipsia:
A chronic excessive intake of water; a characteristic of uncontrolled diabetes mellitus.
Polymerase chain reaction (PCR):
A method for expanding small discrete sections of DNA by binding DNA primers to sections at the ends of the DNA to be expanded and using cycles of heat (to create single-stranded DNA) and cooler temperatures (to allow a DNA polymerase enzyme to create new sections of DNA between the primer ends).
Polymorphic:
Having more than one form.
Polymyositis:
An inflammatory condition of muscle of unknown etiology. Muscle pain and weakness are common symptoms of this condition. When associated with a skin rash the condition is referred to as dermatomyositis.
Polynucleotide kinase:
An enzyme that catalyzes the transfer of phosphate from ATP to the 5-prime termini of DNA or RNA.
Polyphagia:
Excessive eating or hunger, a characteristic of uncontrolled diabetes mellitus.
Polyuria:
The passage of a large amount of urine in a given period, a characteristic of diabetes mellitus.
Portal triad:
A term used to describe a microanatomical feature of liver consisting of branches of vein, artery and bile duct.
Positron emission tomography (PET):
A computerized radiographic technique that shows metabolic activity occurring in various body structures (in the heart and brain, for example). A radioactive substance that emits positively charged electrons (positrons) is injected into or inhaled by the patient, in whom they combine with negatively charged electrons. The resulting gamma radiation
is converted into color-coded images.
Postpartum Thyroiditis:
An autoimmune condition resulting in transient thyrotoxicosis followed by hypothyroidism occurring after parturition (giving birth). It may recur with subsequent pregnancies.
Potassium (K):
An essential element found primarily in the cells of the body. It helps to maintain proper muscle and nerve function; it also helps in some important metabolic processes. Blood serum potassium levels usually are determined to help evaluate heart rhythm irregularities, neuromuscular disorders and kidney function.
PPD:
Purified protein derivative (skin test antigen for tuberculosis).
PPNG:
Penicillinase-producing (i.e., penicillin-resistant) Neisseria gonorrhoeae.
PRAS:
Prereduced, anaerobically sterilized.
Precipitin test:
Detection of antigen by allowing specific antibody to diffuse through liquid or gel until an antigen-antibody complex forms, which can be viewed as a line of precipitated material.
Precision:
Reproducibility, the agreement of data points (test results) when a measurement is made more than once.
Primary structure:
In proteins and nucleic acids, the linear sequence of amino acids and nucleotides, respectively.
Primary wavelength:
The wavelength at which a chemistry has the greatest absorbance.
Prion:
1) Proteinaceous infectious agent associated with Creutzfeldt-Jakob disease and perhaps other chronic, debilitating central nervous system diseases. 2) An infectious agent that lacks nucleic acids and appears to consist entirely of protein. See Virus and Viroid.
Proctitis:
Inflammation of the rectum.
Prodromal:
Early manifestations of a disease before specific symptoms become evident.
Proglottid:
Segments of the tapeworm containing male and female reproductive systems; may be immature, mature, or gravid.
Prognosis:
Forecast as to the possible outcome of a disease.
Progranulocyte:
An immature white blood cell precursor found only in the bone marrow except in disease states. It is the characteristic stage of maturation where azurophilic non-specific granules first appear in the cytoplasm of the granulocytic maturation sequence. Also known as a promyelocyte.
Progressive bacterial synergistic gangrene:
Serious polymicrobial infection of skin and soft tissue, often a postoperative complication, involving a mixture of microaerobic streptococci and Staphylococcus aureus classically. At times the streptococci are anaerobic or gram-negative bacilli are seen in lieu of the staphylococci.
Prokaryotic:
Organisms without a true nucleus.
Prolactin:
A protein hormone secreted from the anterior pituitary and several other tissues. In females prolactin promotes lactation. In males its role is unclear, though male levels may increase two to threefold during sleep and equal female levels. Normal ranges: Adult female and male: 0-20 ng/mL; Pregnancy: 20-400 ng/mL. Increased values are associated with Galactorrhea, Amenorrhea, Pituitary tumors, Hypothyroidism. Decreased values are associated with Pituitary apoplexy, Pituitary destruction from tumor.
Proopiomelanocortin (POMC):
A large precursor protein synthesized in the anterior pituitary gland that is cleaved to form a number of hormones, including adrenocorticotropic hormone.
Prophage:
The phage DNA that is integrated into the host's hereditary material.
Prophylaxis:
Preventive treatment (e.g., the use of drugs to prevent infection).
Propionibacterium:
Gram positive, rod- to club-shaped diphtheroid, non-motile, aerotolerant and anaerobic bacteria.
Propionic acid bacteria:
Bacteria that carry out a propionic acid fermentation.
Propionic acid fermentation:
A fermentation in which the major waste products are propionic acid and carbon dioxide.
Bacteria such as Propionibacterium carry out this type of fermentation.
Prostate specific antigen(PSA):
A substance manufactured only by the prostate.
Prostate specific antigen test:
A blood test which measures a patient's level of prostate specific antigen. If elevated, the antigens may be an indicator of prostate cancer.
Prostatic acid phosphatase test:
An enzyme that rises above normal in many patients when prostate cancer has spread beyond the prostate.
Prostatectomy:
Surgical removal of the prostate.
Prostatitis:
Inflammation of the prostate gland, usually caused by infection, characterized by fever, low back or perineal pain, and at times urinary frequency and urgency; a common background factor for recurrent cystitis in males.
Prostheca (pl. prosthecae):
Celular extensions of the cell, such as the stalk in Caulobacter and the hypha in Rhodomicrobium.
Prosthesis:
An artificial part such as a hip joint or eye.
Protein:
Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen and usually sulphur, the characteristic element being nitrogen and which are widely distributed in plants and animals. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function. They serve as enzymes, structural elements, hormones, immunoglobulins, etc. and are involved in oxygen transport, muscle contraction, electron transport and other activities throughout the body. (See also Table of Plasma Proteins)
Protein A:
A protein on the cell wall of strains of Staphylococcus aurus (Cowan strain) that binds the Fc portion of antibodies.
Proteinuria:
Too much protein in the urine. This may be a sign of kidney damage.
Proteus:
Gram negative, rod-shaped, peritrichously flagellated, facultatively anaerobic bacterium. Causes urinary tract infections.
Prothrombin:
A plasma protein, one of the coagulation factors and the precursor of thrombin, prothrombin is synthesized in the liver with the help of vitamin K. The prothrombin time (PT) test measures blood clotting time, evaluates bleeding disorders and liver damage, and monitors the use of anticoagulant drugs.
Proton-motive force (pmf):
An energized state of a membrane due to electrical potentials and proton gradients (pH differences). The potential created across a membrane when protons (hydrogen ions) are concentrated on one side of the membrane is: p = U — 2.3RT pH/F where U = membrane potential, R = gas constant, T = absolute temperature, pH = pH difference across the membrane, and F = faraday.
Protoplast:
Gram positive cell that lacks its peptidoglycan cell wall because of mutation or treatment with chemicals. In an isotonic solution, protoplasts become spherical. Lysozyme treatment of gram positive cells results in protoplasts. See Spheroplast.
Prototroph:
Naturally occurring or wild strain.
Providencia:
Gram negative, rod-shaped, peritrichously flagellated or nonmotile, facultatively anaerobic bacterium.
Provirus:
The virus DNA that is integrated into the host's hereditary material.
Proximal:
Nearest or closest to a point of reference; toward the attached end or origin or a structure (opposite of distal).
Pseudocholinesterase:
See cholinesterase.
Pseudomembrane:
Necrosis of mucosal surface simulating a membrane.
Pseudomembranous colitis (PMC):
Syndrome in the large bowel characterized by a layer of necrotic tissue and dead inflammatory cells often caused by the toxin of Clostridium difficile.
Pseudomonads:
Gram negative, rod-shaped, polarly flagellated, aerobic bacteria.
Pseudomonas aeruginosa:
Gram negative, rod-shaped, polarly flagellated, aerobic bacterium. Produces a green pigment. An opportunistic pathogen.
Pseudoplasmodium:
See Acrasiomycetes; Slime mold.
Psychrophile:
(1) An organism that has its maximum growth rate between 0°C and 20°C. (2) An organism that grows at temperatures below 5°C.
Psychrophilic:
Cold-loving (e.g., microorganisms that grow best at low [4°C] temperatures).
Puerperal sepsis:
A bacterial invasion of the blood, acquired during childbirth. Also known as childbed fever.
Purple nonsulfur bacteria:
Generally anaerobic, photosynthetic bacteria that use light to generate their energy (ATP) by cyclic photophosphorylation only. They may use simple organic acids such as acetate to generate their reducing electrons to fix carbon dioxide.
Purple sulfur bacteria:
Anaerobic, photosynthetic bacteria that use light to generate their energy (ATP) by cyclic photophosphorylation and hydrogen sulfide as a source of reducing electrons to fix carbon dioxide. They release sulfate rather than molecular oxygen as a result of their metabolism. The purple sulfur bacteria may use organic compounds as a source of reducing electrons and carbon, as do the purple nonsulfur bacteria.
Purulent:
Consisting of pus.
Pus:
Product of inflammation, consisting of fluid and many white blood cells; often bacteria and cellular debris are also present. See Pyo-
Putrefaction:
The decomposition of proteins by microorganisms, with resulting production of foul-smelling compounds from the amino acids.
Pyelonephritis:
Infection of the kidney and renal pelvis and the late effects of such infection.
Pyknosis (pyknotic):
A commonly-observed manifestation of cell aging referring to a nucleus that is very small in size, round, darkly staining and lacks identifiable structures such as nucleoli.
Pylorus:
The distal section of the stomach, where it joins the small intestine.
Pyo-:
Prefix meaning pus. Example: pyogenic means pus producing.
Pyocin:
Pigment produced by a bacterium that has antibacterial properties against other strains or species of bacteria.
Pyoderma:
Any of the pus-producing lesions of the skin such as boils or impetigo.
Pyogenic:
Pus-producing.
Pyometra:
A disease of the uterus involving accumulation of pus in the lumen.
QC:
Quality control.
Q-fever:
A disease caused by the bacterium Coxiella burnetii sometimes transmitted to humans through milk from diseased cattle. The bacterium is highly resistant to heat because of the sporelike structures it forms.
QNS:
Quantity not sufficient.
Qualitative:
A test in which the final result is positive/negative, reactive/nonreactive, present/absent.
Quantitative:
A test in which the final result is expressed as a specific quantity — ng, mg, mcg.
Quartan malaria:
Malaria caused by Plasmodium malariae.
Quarternary structure:
The structure that results when two or more folded proteins from a complex molecule, such as an antibody molecule or the hemoglobin molecule.
R factor:
A plasmid that confers fertility on the host cell and that carries genes that make the host cell resistant to antibiotics and drugs. Plasmid that carries gene coding for resistance to one or more antibacterial agents.
Radioactive:
Emitting radiation that results from atomic disintegration. The electromagnetic energy of, for example, X-rays and gamma rays is radioactive.
Radioactive energy attenuation:
Reduction of intensity of an X-ray beam by the partial absorption of radiation, as by a radiolucent structure. Soft tissue is radiolucent to some extent. In attenuation, the
number of X-rays left in an X-ray beam after penetration through matter is reduced, but never reaches zero.
Radioimmunoassay (RIA):
See assay.
Radioactive iodine excretion test:
A test of thyroid function in which the patient is given radioactive iodine by mouth. The amount of radioactivity excreted in the urine and/or accumulated in the thyroid reflects thyroid activity.
Radioisotopes:
Elements in a form with unstable nuclei that achieve a more stable nuclear configuration by emitting excess energy as radiation (radioactive decay). Radioisotopes can be used to label certain chemicals to measure body function by X-ray film exposure or by measurement in a scintillation counting instrument.
Radiometric analysis:
Determination of a substance that is not itself radioactive by means of an interaction with a radioactive substance.
Radiopaque dye:
A substance or chemical (such as certain iodine compounds) that is given before an X-ray procedure is performed to outline the interior of hollow organs. It does not permit
the passage of X-rays.
Radiopharmaceuticals:
Drugs that spontaneously emit nuclear particles. Different radiopharmaceuticals are chosen according to the organ and purpose (diagnostic, therapeutic, or research). The radioactive material allows differentiation between healthy and diseased tissue.
Raynaud's disease:
Paroxysmal spasm of the digital arteries causing pallor (blanching) of the fingers and toes.
RDS (Respiratory Distress Syndrome):
Neonatal respiratory distress syndrome (RDS, also called hyaline membrane disease) may result if a neonate is delivered before the lungs have had time to fully mature. A major element in the development of RDS is the inability of immature lungs to produce pulmonary surfactant, the lipid/protein material that reduces surface tension in the alveolar water layer and promotes uniform inflation of the lungs.
Pulmonary surfactant is rich in disaturated phophatidyl choline (lecithin). Lecithin synthesis in the lung increases dramatically
as the lung matures and begins producing surfactant. Because the amount of amniotic fluid and the concentration of material in it
may vary between pregnancies, lecithin levels are generally expressed as a ratio against sphingomyelin, a non-pulmonary lipid
whose concentration is relatively constant in amniotic fluid. Phosphatidylglycerol (PG) is a second lipid that shows a similar time course to the development of pulmonary surfactant; it is undetectable in amniotic fluid until lung maturity just prior to birth. The RDS risk is about 2% if PG is present.
Testing for lung maturity is important in management of premature labor, hemolytic disease of the newborn, premature rupture of membranes, and any other clinical situations in which early delivery of the fetus would be considered. The results of these tests are used to determine whether to attempt to suppress labor or to induce delivery. If delivery cannot be delayed when the lungs are immature, dexamethasone is often given to stimulate maturation of the surfactant production system.
Reagent:
A substance used to produce a specific chemical reaction. It may be used to detect, measure, or prepare other substances.
Reagin:
An antibody that reacts in various serologic tests for syphilis.
Receptor:
A cellular protein that binds hormones or neurotransmitters and initiates a physiologic response. Some types of receptors are located in the plasma membrane, while others are found within the cytoplasm or nucleus.
Recombinant DNA:
Spliced DNA formed from two or more different sources that have been cleaved by restriction enzymes and joined by ligases.
Rectum:
The last five or six inches of the intestine leading to the outside of the body.
Red Cell Distribution Width (RDW):
This measurement is included on some instrumentation as part of the complete blood count (CBC). It measures the distribution of red blood cell volume and is equivalent to anisocytosis on the peripheral blood smear. It is calculated as the coefficient of variation of the red cell volume and is expressed as a percentage (normal 11.5 to 14.5 percent).
Reduction:
The addition (or gain) of electrons (or electron density), most commonly due to addition of hydrogen to or removal of oxygen from a molecule. The opposite of oxidation. See Oxidation.
Refractive index:
The ratio of the speed of light in a vacuum to the speed of light in a material. The index of refraction of a glass lens is approximately 1.4.
Reference electrode:
An electrode that has a well known and stable equilibrium electrode potential. It is used as a reference point against which the potential of other electrodes (typically that of the working electrode or measuring electrode) can be measured in an electrochemical cell. In principle it can be any electrode fulfilling the above requirements. In practice, there are a few commonly-used (and usually commercially-available) electrode assemblies that have an electrode potential independent of the electrolyte used in the cell. For some common reference electrodes see e.g., the silver/silver-chloride electrode, calomel electrode, and hydrogen electrode. Strictly speaking, there can be a small change in the potential of these electrodes depending on the electrolyte because the presence of a liquid-junction potential. This is very often (justifiably or not) ignored. The liquid-junction potential is also
minimized by the use of high concentration potassium chloride as the filling solution of the reference electrodes, because the diffusion rate of both ions is very closely the same in these solutions.
Renin:
An enzyme of the hydrolase class that catalyses cleavage of the leucine-leucine bond in angiotensin to generate angiotensin I. The enzyme is synthesised as inactive prorenin in the kidney and released into the blood in the active form in response to various metabolic stimuli. Not to be confused with rennin (chymosin).
Renin-angiotensin system:
A system consisting of renin, angiotensin-converting enzyme, and angiotensin II. Renin, an enzyme produced in the kidney, acts on angiotensinogen, an alpha-2 globulin produced by the liver, forming angiotensin I. The converting enzyme contained in the lung acts on angiotensin I in the plasma converting it to angiotensin II, the most powerful directly pressor substance known. It causes contraction of the arteriolar smooth muscle and has other indirect actions mediated through the adrenal cortex.
Reservoir:
Source from which an infectious agent may be disseminated; for example, humans are the only reservoir for Mycobacterium tuberculosis.
Resin:
Plant product composed largely of esters and ethers of organic acids and acid anhydrides.
Resolving limit:
The resolving limit (R) is the minimum distance between two points such that the images of the two points can be distinguished from each other. The resolving limit (R) of a lens system depends upon the wavelength of light (h), the index of refraction (n) of the material between the object and the objective lens, and the diameter and working distance of the lens, given by sin Ø : R = h/n sin Ø. Same as the limit of resolution.
Respiration:
Involves the oxidation of inorganic or organic molecules, the generation of energy (ATP) by running electrons (and hydrogen ions) through an electron transport system, and the donation of electrons to an inorganic electron acceptor. Aerobic respiration occurs when the electron acceptor is molecular oxygen, and anaerobic respiration occurs when the electron acceptor is an inorganic molecule other than oxygen, such as sulfate or nitrate.
Restriction endonuclease:
Enzyme that breaks nucleic acid (usually DNA) at only one specific sequence of nucleotides. Bacterial enzymes that cut DNA within the DNA molecule. The most useful endonucleases are those that cut at specific sites. These enzymes are used in genetic engineering to splice genes. See Endonuclease and Exonuclease.
Restriction enzymes:
A common name for restriction endonucleases.
Restriction mapping:
A technique used to identify the number and order of sites in DNA where restriction enzymes cleave.
Reticular bodies:
The dividing, noninfectious chlamydia found in infected cells. Same as initial bodies. See Elementary bodies.
Reticulate body:
The metabolically more active form of elementary bodies of Chlamydia sp.
Reticulocyte:
A young red blood cell containing a network of basophilic substances. A red blood cell containing a network of granules or filaments representing an immature stage in development. Reticulocyte count normal range: 0.5 - 1.5% of circulating red blood cells. Requires supervital stains (eg., New Methylene Blue).
Reticuloendothelial system:
Macrophage system, which includes all the phagocytic cells of the body except for the granulocytic leukocytes.
Retinopathy:
This condition of the eye is associated with diabetes mellitus and is progressively characterized by microaneurysms, intraretinal punctuate hemorrhages, yellow waxy exudates, cotton-wool patches, and macular edema.
Retro-:
Prefix meaning behind or backward. Example: retroperitoneal, behind the peritoneum.
Reverse transcriptase:
An enzyme from retroviruses that copies RNA into DNA, and is also used in recombinant DNA work. Known formally as a RNA-dependent DNA polymerase.
Rheumatoid factor:
IgM antibodies produced by some patients against their own IgG in rheumatoid arthritis.
Rhizobium:
Gram negative, rod-shaped, flagellated, aerobic bacteria able to grow within certain plant cells. When growing within root nodules, the cells are pleomorphic. Carries out symbiotic nitrogen fixation.
Rhizoid:
Rootlike absorbing organ.
Rhizopus:
A fungus in the class Zygomycetes which forms asexual and sexual sporangiospores and sexual zygospores. The mycelium is coenocytic and nonseptated.
RIA:
Radiometric immunoassay (radioimmunoassay).
Ribonucleotide:
A nucleotide whose sugar moiety is ribose. Nucleotide used in making RNA.
Ribose:
A 5 carbon aldose.
Rickets:
A condition caused by deficiency of vitamin D, especially in infancy and childhood, with disturbance of normal ossification. The disease is marked by bending and distortion of the bones under muscular action, by the formation of nodular enlargements on the ends and sides of the bones, by delayed closure of the fontanelles, pain in the muscles and sweating of the head. Vitamin D and sunlight together with an adequate diet are curative, provided that the parathyroid glands are functioning properly.
Rickettsia:
Gram negative, oval to rod-shaped, nonmotile, obligately intracellular parasitic bacteria. See also Coxiella.
Rickettsia prowazekii:
Causes epidemic typhus.
Rickettsia typhi:
Causes rat and mouse (murine) typhus.
Rickettsia rickettsii:
Causes Rocky Mountain spotted fever.
Risk management:
The process of minimizing risk to an organization by developing systems to identify and analyze potential hazards to prevent accidents, injuries, and other adverse occurrences, and by attempting to handle events and incidents which do occur in such a manner that their effect and cost are minimised. Effective risk management has its greatest benefits in application to insurance in order to avert or minimize financial liability.
RNA:
Ribonucleic acid.
RNA polymerase:
An enzyme that transcribes an RNA molecule from the template strand of a DNA molecule. It adds to the 3' end of the growing RNA molecule one nucleotide at a time using ribonucleotide triphosphates (rNTPs) as substrates (this reaction releases pyrophosphates). RNA polymerase I is dedicated to the synthesis of only one type of RNA molecule (pre-rRNA). RNA polymerase II is required for general transcription reactions. RNA polymerase III produces small RNAs such as tRNAs and 5S rRNA.
Rouleaux:
A group of red blood cells arranged like a roll of coins, owing to an abnormal protein coating on the cells' surfaces; seen in multiple myeloma and Waldenström's macroglobulinemia.
RPR:
Rapid plasma reagin, nontreponemal test for antibodies developed in response to syphilis infection.
Rubella:
A contagious viral infection characterized by a red rash, fever, and enlarged lymph nodes. Maternal infection in the early stage of pregnancy may result in congenital defects of the fetus. Blood tests are performed to detect immunity (antibodies) to rubella. Rubella is commonly known as German measles.
Saccharide:
A sugar molecule, a carbohydrate. See Carbohydrate and Glucose.
Saccharolytic:
Capable of breaking down sugars.
Saccharomyces cerevisiae:
A yeast belonging to the class Ascomycetes which forms asci and sexual ascospores and carries out alcoholic fermentation. It is used in making bread, wine, and beer.
Salicylates:
The drugs or compounds derived from salicylic acid — such as aspirin — that have fever reducing, anti-inflammatory, and pain relieving properties. Toxic concentrations may lead to nausea, impaired hemostasis, and electrolyte disturbance. The serum concentration of salicylate may be measured by a blood test.
Saliva:
A viscous secretion of salivary glands.
Salmonella typhi:
Gram negative, rod-shaped, peritrichously flagellated, facultatively anaerobic bacteria. Causes typhoid fever.
Salmonella typhimurium:
Causes paratyphoid fever: gastroenteritis and bacteremia.
San Joaquin Valley Fever:
A pulmonary infection caused by the fungus Coccidioides. See Valley fever and Coccidioidomycosis.
Saponification:
Hydrolysis of a lipid molecule which liberates a fatty acid. Any lipid which contains a fatty acid as part of its structure.
Saprophytic:
Nonpathogenic.
Sarcina:
Gram positive, spherical, nonmotile, anaerobic, catalase negative bacteria that are found in packets of four, eight, or more cells. They have complex growth factors. The cell wall of this species has a thick outer layer of cellulose. This is the only bacterium known to have a wall with cellulose. Only one other bacterium, Acetobacter xylinum, is known to synthesize cellulose.
Sarcoidosis:
Disease of unknown etiology in which there are chronic inflammatory granulomatous lesions in lymph nodes and other organs.
Sarcoptes scabei:
The mite (arachnid) that burrows under the outer layer of skin and causes scabies.
Saturation or Saturated molecule:
A hydrocarbon consisting of only carbon-carbon single bonds and hydrogens. Eg., an Alkane or a saturated Fatty Acid.
SBA:
Suprapubic bladder aspiration.
SBE:
Subacute bacterial endocarditis.
Scanning electron microscope:
An electron microscope with a beam that scans (moves point-to-point) over the surface of a specimen, producing a lifelike, three dimensional view on film or screen. The magnification of the image is usually less than that of a non-scanning electron microscope. For visualization by a scanning microscope, tissues do not require extensive preparation and handling.
Schistocyte:
An abnormal red cell that is formed when pieces of the red cell membrane become fragmented. Whole pieces of the red cell membrane appear to be missing, causing bizarre-looking red cells.
Schistosoma:
A flatworm (fluke) that is responsible for schistosomiasis, an infection of the intestinal veins and liver which leads to liver destruction. Causes schistosomiasis.
Schizogony:
Stage in the asexual cycle of the malaria parasite that takes place in the red blood cells of humans.
Schlichter test:
Synonym for the serum bactericidal level test.
Sclerotic:
Hard, indurated.
Scolex (pl., scolices):
Head portion of a tapeworm; may attach to the intestinal wall by suckers or hooklets.
Scotochromogens:
Mycobacteria that are pigmented even in the absence of exposure to light.
Secondary structure:
In proteins, the structure formed from the folding of the primary structure due to disulfide bonds, and the alpha helix or pleated sheets formed from the hydrogen bonding. In nucleic acids, the structure formed from the folding of the primary structure due to the hydrogen bonding between complementary bases. See Tertiary structure.
Second messenger:
A small molecule generated inside cells in response to binding of a hormone to cell surface receptors. Examples include cyclic AMP and calcium.
Secondary wavelength:
A wavelength chosen because the color developed by the reaction is minimal. It is also usually the wavelength at which the common clinical interfering substances have little
or no absorbance.
Secretin:
A peptide hormone synthesized in the small intestine and brain. A major activity of this hormone is to stimulate bicarbonate secretion from the pancreas.
Self-monitoring of blood glucose:
A means of testing levels of blood glucose via a fingerstick blood sample and a blood glucose testing meter to determine the glucose result. Regular monitoring is an essential
component of any diabetes management regimen. 3 to 4 times a day is recommended by the American Diabetes Association, for those using insulin.
SEM:
Scanning electron micrograph.
Semen:
A thick, whitish fluid secreted by the prostate to carry sperm.
Sensitivity:
The extent to which a diagnostic test correctly detects an abnormality. In defining a laboratory test's accuracy, sensitivity indicates the frequency of positive test results
in patients who have the specific disease being tested for. Also, sensitivity as in antibiotic sensitivity (see MIC).
Sepsis:
Generally, infected tissue. See Asepsis.
Septa (pl. septae):
Generally used to describe the walls that segment fungal hyphae and filamentous and branching bacteria.
Septate:
Having cross walls.
Septic shock:
Acute circulatory failure caused by toxins of microorganisms; often leads to multiple organ failure and is associated with a relatively high mortality.
Septicemia (sepsis):
Systemic disease associated with presence of pathogenic microorganisms or their toxins in the blood. See Viremia
Sequestrum:
A detached or dead piece of bone within a cavity, abscess, wound, or area of osteomyelitis.
Sereny test:
Test for bacterial invasiveness; involves applying a supension of the organism to the conjunctiva of a small mammal and observing for development of conjunctivitis.
Serologic testing:
An analysis of blood serum for evidence of infection by evaluating antigen-antibody reactions; used in acute and chronic stages of infection.
Serosanguineous:
Like serous but with some blood present grossly.
Serotonin (5-hydroxytryptamine):
A neurotransmitter and hormone (176 kD), found in vertebrates, invertebrates and plants. It is synthesized from the amino acid tryptophan by enterochromaffin cells in the gut and bronchi. It is metabolised to 5-HIAA in the liver and then excreted in the urine. Serotonin is measured on a blood specimen in cases of suspected carcinoid syndrome (where it is elevated). The normal range for serum serotonin is 101-283 ng/ml. Acronym: 5-HT
Serous:
Like serum.
Serratia marcescens:
Gram negative, rod-shaped, peritrichously flagellated, facultatively anaerobic bacterium. Colonies form a red pigment at 18°C but not at 37°C.
Serum:
The clear, thin, watery portion of a liquid that can be separated from the more solid elements. The fluid portion of whole blood that separates after coagulation of the specimen. It is devoid of fibrinogen (a clotting protein). Serum may be separated out of whole blood by centrifugation.
Serum albumin:
The serum level of the low molecular protein albumin. Albumin, produced by the liver, plays an important role in maintaining plasma oncotic pressure. Normal serum albumin should be 3.5-5.0 grams per deciliter. Low serum albumin can be found in cases of liver disease and malnutrition.
Serum bactericidal level:
Lowest dilution of a patient's serum that kills a standard inoculum of an organism isolated from that patient; this, of course, is related to antibiotic level achieved in the patient's serum and the bactericidal activity of the drug being employed.
Serum globulins:
All blood proteins except albumin (serum albumin, which is not a globulin) and fibrinogen (which is not in the serum). The serum globulins are subdivided into alpha-globulins, beta-globulins, and gamma-globulins on the basis of their electrophoretic mobilities.
Serum glutamic oxaloacetic transaminase (SGOT):
An enzyme present in all tissue, primarily in the liver, heart, and skeletal muscles. It is released into the bloodstream following cell death or injury. Elevated blood levels
of SGOT may signal liver, heart, or skeletal muscle disease. It is also called aspartate aminotransferase (AST).
Serum glutamic pyruvic transaminase (SGPT):
An enzyme present in the same tissues as SGOT. Its appearance in serum is a marker of tissue damage similar to SGOT, but it is a more specific indicator of liver damage. It
is also known as alanine aminotransferase (ALT).
Sex pilus:
Pilus that is necessary if a bacterium is to be able to conjugate and donate genetic information to a recipient cell.
Sexually transmitted disease (STD):
A disease caused by a microorganism that is passed to another person during sexual contact.
SGLUT1:
A membrane transporter that co-transports sodium and a hexose (glucose or galactose) into cells. Important in the absorption of those sugars from the small intestine, and in the kidney.
SGOT:
See serum glutamic oxaloacetic transaminase.
SGPT:
See serum glutamic pyruvic transaminase.
Shift to the left:
An abnormal cell maturation situation that occurs when increased bands, less mature neutrophils, and smaller average number of lobes are found in segmented cells; may be caused by infection, hematologic disorders, or physiologic factors. Refers to early classification in the granulocytic maturation sequence.
Shigella dysenteriae:
Gram negative, rod-shaped, nonmotile, facultatively anaerobic bacterium. Causes dysentery.
Shigella flexneri:
Causes dysentery.
Shock:
1) A sudden disturbance of mental equilibrium. 2) A condition of profound hemodynamic and metabolic disturbance characterised by failure of the circulatory system to maintain adequate perfusion of vital organs, it may result from inadequate blood volume (hypovolemic shock), inadequate cardiac function (cardiogenic shock) or inadequate vasomotor tone (neurogenic shock, septic shock).
Sinus:
Suppurating tract; paranasal sinus, hollows, or cavities near the nose (e.g., frontal and maxillary sinuses).
Slant:
See definition of "butt." The slant is the upper surface of the medium in the tube described. It is exposed to air in the tube.
Slime molds:
Two classes of fungi: Acrasiomycetes (which form pseudoplasmodia) and Myxomycetes (which form plasmodia). The Acrasiomycetes exist as amebae or as pseudoplasmodia (multicellular structures) during one part of their life cycle and form fruiting bodies, similar to molds, during another part. The Myxomycetes exist as plasmodia (single, macroscopic cells with multiple nuclei) during one part of their life cycle and form fruiting bodies when deprived of nutrients.
SMA:
Simultaneous Multiple Analysis - A term first used by Technicon Instruments, Inc.
Smallpox:
Smallpox is an acute viral disease which once claimed a high mortality rate, but was officially announced as globally eradicated in 1979 through W.H.O. immunization programs.
Headache, vomiting and fever precede the eruption of a widespread rash that is raised, vesicular and finally pustular. The eruption follows a set pattern of dissemination, commencing on the head and face. When the final stage is passed, scars (pockmarks) are left to disfigure the skin.
Smallpox vaccine:
A live Vaccinia virus vaccine of calf lymph or chick embryo origin is used for immunization against smallpox. It is now recommended only for laboratory workers exposed to smallpox virus. Some countries continue to vaccinate those in the military service. Complications that result from smallpox vaccination include vaccinia, secondary bacterial infections, and encephalomyelitis.
Sodium (Na):
A chief electrolyte that regulates the amount of fluid inside and surrounding body cells. Measuring blood or urine levels of sodium will help to evaluate electrolyte and fluid balance disorders such as those that occur in edema, kidney, and liver or adrenal gland dysfunctions.
Sodium pump:
The Na+-K+-ATPase. A membrane protein that pumps 3 sodium ions out of cells in exchange for 2 potassium ions in a reaction that hydrolyzes ATP, critical in maintaining low intracellular sodium and resting membrane potential.
Solid-phase Immunosorbent assay (SPIA):
ELISA test in which the capture antigen or antibody is attached to the inside of a plastic tube, microwell, or to the outside of a plastic bead, in a filter matrix, or some other solid support. Allows faster interaction between reactants and more concentrated visual end roducts than ELISA tests performed in liquid.
Solutes:
The dissolved ions and small molecules in a solution.
Solution:
A liquid mixture of compounds in which one material, the solvent, uniformly distributes and dissolves other compounds (solutes). Examples are salt in water and ethanol in water.
Solvent:
A material, usually water, that uniformly distributes and dissolves another material.
Somatic:
Pertaining to the body (of a cell) (e.g., the somatic antigens of Salmonella species).
Sonography:
A noninvasive diagnostic technique, also known as ultrasonography, in which high frequency sound waves are aimed at a selected body area or organ, with the resulting echoes being converted to images. Diagnostic ultrasound often is employed for obstetrical conditions.
Southern blot:
Identification of specific genetic sequences by separating DNA fragments by gel electrophoresis and transferring them to membrane filters in situ. Labeled complementary DNA applied to the filter will bind to homologous fragments, which can then be identified by detecting the presence of the labeled DNA in association with bands of certain molecular size. Named after its discoverer, E.M. Southern.
Specificity:
The ability of a diagnostic test to rule out the presence of a disease. In defining a laboratory test's accuracy, specificity indicates the frequency of negative test results
in patients who do not have the specific disease being tested for. (Also see "sensitivity.")
Spectrin:
The major cytoskeleton protein, along with certain integral proteins, responsible for maintaining the biconcave shape of erythrocytes.
Spectrophotometer:
An instrument that measures the degree of absorption (or emission) of electromagnetic radiation by a substance. The measuring system generally includes a photomultiplier. Ultraviolet, infrared, visible, and microwave regions of the electromagnetic spectrum may be measured in this way.
Spectrophotometric:
Pertaining to the estimation of coloring matter in a solution using a device (spectrophotometer) that compares that color to the full spectrum.
Spectroscopy:
Spectroscopy is the science of measuring the emission and absorption of different wavelengths (spectra) of visible and non-visible light; this is done via a spectroscope, which consists of a slit, prism, collimator lens, object lens, and a grating.
Sphaerotilus:
Gram negative, rod-shaped, chain-forming, sheathed, aerobic bacterium. Individual cells may have subpolar flagella.
Spheroplast:
Gram negative cell that has lost its peptidoglycan layer. In an isotonic solution, spheroplasts become spherical. Speroplasts can be formed by treating gram negative cells with lysozyme.
Sphincter:
A ringlike band of muscle that constricts a passage or closes a natural orifice. Examples include esophageal sphincters and the anal sphincter.
SPIA
Solid-phase immunosorbent assay.
Spina bifida:
A congenital condition that is characterized by incomplete closure of the fetal vertebral arches. Defective closure of the bony canal that encases the spinal cord allows protrusion of portions of the brain and spinal cord through the defect.
Spinal tap (spinal or lumbar puncture):
Entrance by needle for removal of fluid from the spinal cavity, for diagnostic tests or to allow introduction of other fluids (anesthetics, diagnostic aids, for example). Spinal or cerebrospinal fluid (CSF) bathes the brain, providing mechanical support and maintaining the chemical balance. Central nervous system diseases or injury can cause changes
in CSF (elevated cell count, elevated protein, presence of tumor cells, bacteria, color change, for example) that are of diagnostic importance.
Spirillum:
Gram negative, spiral, polarly flagellated, aerobic, oxidase positive bacterium.
Spirochete:
A group of helical bacteria that have axial filaments rather than flagella. Examples are Treponema and Leptospira.
Spirogyra:
A filamentous eukaryotic green alga with spiral-shaped chloroplasts.
Spirulina:
A photosynthetic prokaryotic cyanobacterium that forms trichomes. Molecular oxygen is evolved from photosynthesis.
Spore:
Reproductive cell of bacteria, fungi, or protozoa; in bacteria, may be inactive, resistant forms within the cell.
Sporogony:
Stage in the sexual cycle in the malarial parasite that takes place in the mosquito.
Sporolactobacillus:
Gram positive, rod-shaped, peritrichously flagellated, endospore-forming, microaerophilic, catalase negative bacteria that lack cytochromes and ferments by the lactic acid route.
Sporosarcina:
Gram positive, spherical, tetrad-forming, endospore forming, nonmotile, aerobic bacterium.
Sporozoite:
Slender, spindle-shaped organism that is the infective stage of the malarial parasite; it is inoculated into humans by an infected mosquito and is the result of the sexual cycle of the malarial parasite in the mosquito.
Sputum:
Material discharged from the surface of the lower respiratory tract air passages and expectorated (or swallowed).
Stab culture:
Culture in which the inoculation of a tube of solid medium is made by stabbing with a needle to encourage anaerobic growth in the bottom.
Stage:
A term used to describe the extent of cancer.
Staging:
Tests conducted to determine the stage of a cancer.
Staphylococcus:
Gram positive, spherical, cluster-forming, nonmotile, facultatively anaerobic bacteria.
Staphylococcus aureus:
Commonly found in the nose. Causes skin infections and food poisoning.
Staphylococcus epidermidis:
Commonly found on the skin. A cause of endocarditis.
Stat:
Statim (Latin); immediately.
Stationary growth phase:
Stage in the growth cycle of a bacterial culture in which the vegetative cell population equals the dying population.
STD:
Sexually transmitted disease.
Steric hindrance:
The physical blockage of a particular site within a molecule by the presence of local atoms or groups of atoms. Steric hindrance impedes reaction at a particular site.
Sterile (sterility):
Free of living microorganisms (the state of being sterile).
Sterilization:
The killing of all microorganisms and infectious agents, such as prions and viroids.
Steroid:
A hydrophobic molecule derived from cholesterol, which itself is a steroid. Many steroids function as hormones.
Strep throat:
Infection of the throat and tonsils caused by group A streptococci. Symptoms include sore throat, fever, chills, and enlarged tonsils with white spots (pus). Strep throat or
streptococcal sore throat may be detected by immunofluorescence staining of material from throat swabs. If proper treatment, including antibiotic administration, is not given,
rheumatic fever can result.
Streptococci, Viridans group::
S. salivarius, S. sanguis, and S. mutans. Alpha-hemolytic on blood agar plates. Normally found in the oral cavity. May cause subacute bacterial endocarditis.
Streptococcus:
Gram positive, spherical, chain-forming, nonmotile, aerotolerant anaerobic, catalase negative bacteria that lack cytochromes. A member of a family of coccoidal (round) bacteria that can cause a variety of external and internal infections.
Streptococcus agalactiae:
Group B. Causes bovine mastitis and infections in newborn infants.
Streptococcus bovis:
Group D nonenterococcus. Causes subacute bacterial endocarditis.
Streptococcus cremoris:
Group N. Used in the fermentation of dairy products.
Streptococcus dysgalactiae:
Group C. Causes bovine mastitis.
Streptococcus equinus:
Group D nonenterococcus. Causes subacute bacterial endocarditis.
Streptococcus faecalis:
Group D enterococcus. May cause endocarditis.
Streptococcus mitis:
Viridans group. May cause subacute endocarditis.
Streptococcus mutans:
Viridans group. Responsible for tooth decay.
Streptococcus pneumoniae:
Pneumococcus group. A major cause of pneumonia.
Streptococcus pyogenes:
Group A. Causes strep throat, scarlet fever, rheumatic fever, impetigo, skin infections, and puerperal sepsis.
Streptococcus thermophilus:
Participates in the fermentation of milk to produce yogurt.
Streptomyces:
Gram positive, rod-shaped, mycelia-forming, aerobic bacteria. Many species produce antibiotics.
Strobila:
Entire chain of tapeworm proglottids, excluding the scolex and neck.
Stroma:
The structural elements or framework of an organ, as distinguished from its functional components or parenchyma
Substrate:
A substance on which an enzyme (or catalyst) acts.
Substrate level phosphorylation:
Occurs when a phosphorylated substrate donates the phosphate in the synthesis of ATP from ADP. See Oxidative phosphorylation and fermentation.
Sulfate-reducing bacteria:
Bacteria that use sulfate as an electron acceptor during anaerobic respiration. Examples include Desulfovibrio and Desulfotomaculum.
Sulfur granule:
Small colony of organisms with surrounding clublike material; yellow-brown; resembles grain of sulfur.
Sulfur-oxidizing bacteria:
Bacteria that use reduced forms of sulfur, such as hydrogen sulfide, elemental sulfur, and thiosulfate, as a source of reducing electrons or energy. Examples include the photosynthetic bacteria, such as Chromatium and Chlorobium, and the aerobic Beggiatoa and Thiothrix.
Superantigen:
Molecules produced by microbes (viruses, bacteria, and perhaps parasites) that act independently to stimulate T-cell activities, including cytokine release. Among the most potent T-cell mitogens, superantigen stimulation can result in anergy, or alternatively, systemic immune system activation.
Superinfection:
Strictly speaking, this refers to a new infection superimposed on another being treated with an antimicrobial agent. The new infecting agent is resistant to the therapy initially employed and thus survives and causes persistence of the infection (now resistant to the treatment) or a new infection at a different site. Term is also used to indicate persistence or colonization with a new organism without any evidence of resulting infection.
Suppuration:
Formation of pus.
Suprapubic bladder aspiration (SBA):
Obtaining urine by direct needle puncture of the full bladder through the abdominal wall above the pubic bone.
Syncytia:
Structure resulting from fusion of cell membranes of several cells to form a multinucleated cellular structure; usually the result of viral infection of the cells. Also, a multinucleated cell which results either from fusion of two or more cells, or from incomplete cell division where the nuclei but not the cell divides.
Syndrome:
Set of symptoms occurring together (e.g., nephrotic syndrome).
Synergism:
Combined effect of two or more agents that is greater than the sum of their individual effects.
Synovial fluid:
Viscid fluid secreted by the synovial membrane; formed in joint cavities, bursae, and so forth.
Systemic infection:
An infection that has spread throughout the body.
Systemic lupus erythematosus:
A disease of humans, probably autoimmune with antinuclear and other antibodies in plasma. Immune complex deposition in the glomerular capillaries is a particular problem. Acronym: SLE.
T4 cell or CD4 cell:
T helper cells which are targets for HIV infection.
T8 cell:
A type of immune cells, T8 cells close down the immune response after it has destroyed invading organisms. T8 cells are sensitive to high concentrations of circulating lymphokine hormones and release their own lymphokines after an immune response has achieved its goal, signalling all other participants to cease their attack. Some memory B-cells remain to ward off a repeat attack by the invading organism. T8 cells are also called t-suppressor cells.
T cells (T-lymphocytes):
1) Thymus-derived lymphocytes protect animals from intracellular infectious agents, such as viruses and some bacteria and protozoans. T-lymphocytes also modulate the antibody response to infectious agents. 2) Lymphocytes involved in cellular immunity. 3) A class of lymphocytes, so called because they are derived from the thymus and have been
through thymic processing. Involved primarily in controlling cell-mediated immune reactions and in the control of B-cell development. The T-cells coordinate the immune system by secreting lymphokine hormones. There are 3 fundamentally different types of t-cells: helper, killer, and suppressor. Each has many subdivisions. T-cells are also called t-lymphocytes. They bear T-cell antigen receptors (CD3) and lack Fc or C3b receptors. Major T-cell subsets are CD4 (mainly helper cells) and CD8 (mostly cytotoxic or suppressor T-cells). Uncontrolled proliferation of this type of cell gives rise to T-cell leukemia/lymphoma.
T-suppressor cell (T8 cells):
A type of immune cells, also called T8 cells, these cells close down the immune response after it has destroyed invading organisms. T8 cells are sensitive to high concentrations of circulating lymphokine hormones and release their own lymphokines after an immune response has achieved its goal, signalling all other participants to cease their attack. Some memory B-cells remain to ward off a repeat attack by the invading organism.
T3 Thyrotoxicosis:
A condition of hyperthyroidism where FT3, but not FT4, is elevated.
T3 Uptake(%):
A measurement of the unsaturated thyroxine binding sites of the serum thyroxine binding proteins.
Taenia:
Tapeworms. Cause taeniasis, an infection of the intestines, heart, spinal cord, and brain. The symptoms are diarrhea, abdominal pain and weight loss.
Target Cell:
An abnormal red cell which looks like a "Bull's Eye" with hemoglobin concentrated in the center and on the rim of the cell. Synonymous with Leptocyte. Also, a cell which is responsive to a particular hormone because it bears the receptor for that hormone.
Tartaric acid:
Of or pertaining to the acid of tartar; derived from, or resembling, tartar. Tartaric acid, is an acid widely diffused throughout the vegetable kingdom, as in grapes, mountain-ash berries, etc, and obtained from tartar as a white crystalline substance, C2H2(OH)2.(CO2H)2, having a strong pure acid taste. It is used in medicine, in dyeing, calico printing, photography, etc, and also as a substitute for lemon juice. Called also dextro-tartaric acid. By extension, any one of the series of isomeric acids (racemic acid, levotartaric acid, inactive tartaric acid) of which tartaric acid proper is the type.
TB:
Tuberculosis.
TDM:
Therapeutic drug monitoring, testing serum for levels of antibiotics or other therapeutic agents.
Teardrop Cell:
This abnormal red cell is seen with frequency in the myeloproliferative disorders, it is shaped like a tear (synonymous with Dacrocyte).
Teichoic acids:
Large polymers that are attached to the peptidoglycan layer in gram positive bacteria and may contribute as much as 50 percent to the weight of the cell wall. Teichoic acids are polymers of phosphate and molecules such as glycerol or ribitol. When teichoic acids are attached to membrane lipids, they are referred to as lipoteichoic acids.
Telophase:
The final stage of mitosis or meiosis, when chromosome separation is completed.
TEM:
Transmission electron micrograph.
Tenesmus
Painful, unsuccessful straining in an attempt to empty the bowels.
Terminal transferase:
An enzyme that catalyzes the addition of nucleotides to the 3-prime termini of DNA.
Tertiary structure:
In a protein, the final three-dimensional structure that forms from the folding of the polypeptide. The final folding is determined by the disulfide bonds, the hydrogen bonds, and the hydrophobic and hydrophilic interactions of the amino acids with water and with themselves.
Testosterone:
A male sex hormone produced mostly by the testicles with a small amount produced by the adrenal glands. Testosterone stimulates a man's sexual activity and growth of other
sex organs, including the prostate.
Thalassemia:
A genetic form of anemia in which there is abnormality of the globin portion of hemoglobin. Affected individuals cannot synthesise hemoglobin properly, and they produce small, pale, short-lived red blood cells. Widespread in Mediterranean countries.
Thalassemia major:
The disease also known as beta thalassemia. The clinical picture of this form of anaemia was first described in 1925 by the pediatrician Thomas Benton Cooley. Other names for the disease are Cooley's anemia and Mediterranean anemia. The term thalassemia was coined by the nobel prise winning pathologist George Whipple and the professor of pediatrics William Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean sea) + -aemia means in the blood; so thalassaemia means sea in the blood. Thalassemia is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent (and so are said to be homozygous for beta thalassemia). The parents with just one thalassemia gene (heterozygotes), are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth (because at birth we still have predominantly fetal hemoglobin which does not contain beta chains) but the anemia emerges in the first few months of life and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease.
Theophylline:
A drug used as a relaxant of bronchial smooth muscle. Toxic levels can cause increased heartbeats, nausea, and seizures. A blood test is available to monitor levels of the drug.
Therapy, antimicrobial:
Treatment of a patient for the purpose of combating an infectious disease.
Thermoduric:
Highly resistant to heat. Vegetative cells and many types of spores are thermoduric.
Thermolabile:
Adversely affected by heat (as opposed to thermostable, not affected by heat).
Thiobacillus:
Gram negative, rod-shaped, polarly flagellated or nonmotile, aerobic, carbon dioxide-fixing bacteria that oxidize hydrogen sulfide, sulfur, or thiosulfate to sulfate for energy and for reducing electrons.
Thiol:
An organic molecule that contains the sulfhydryl group (-SH) as a functional group; eg., the amino acid Cysteine.
Thiothrix:
Gram negative, oval to rod-shaped, filament-forming, aerobic, carbon dioxide-fixing, hydrogen sulfide- and sulfur-oxidizing bacteria that accumulate sulfur granules within the cell.
Thoracentesis:
Drainage of fluid from the pleural space.
Thoracic:
Pertaining to the chest cavity.
Three-prime (3') end:
The end of a DNA or RNA strand with a free 3' hydroxyl group corresponding to the end of transcription (see also five-prime end).
Thrombocytopenia:
Decreased numbers of platelets.
Thrombocytosis:
Increased numbers of platelets.
Thrombosis:
The formation, development or presence of a thrombus.
Thrombus:
An aggregation of blood factors, primarily platelets and fibrin with entrapment of cellular elements, frequently causing vascular obstruction at the point of its formation. Some authorities differentiate thrombus formation from simple coagulation or clot formation.
Thrush:
A form of Candida infection that typically produces white plaquelike lesions in the oral cavity.
Thymine:
A pyrimidine. A 6 member nitrogenous base used in deoxyribonucleotides.
Thyroglobulin (Tg):
A large dimeric protein found in thyroid follicular cells that serves as a precursor for the production of T3 and T4 from MIT and DIT.
Thyroglobulin antibodies (TgAb):
Autoantibodies produced by the body against its own thyroglobulin proteins. TgAb attacks the thyroid and disrupts thyroid function.
Thyroid (Thyroid gland):
A butterfly-shaped gland located at the base of the throat that controls metabolism through the secretion of T4 and T3 hormones and calcitonin.
Thyroid cancer:
A rare thyroid disease characterized by uncontrolled tissue proliferation in the thyroid gland.
Thyroid Hormone Binding Ratio (THBR):
Recommended nomenclature for T3 Uptake test. A ratio of the solid matrix uptake and the serum uptake.
Thyroid nodules:
Masses (usually benign) that can form in the thyroid gland and may produce excessive thyroid hormone.
Thyroid peroxidase (TPO):
A protein found in thyroid follicle cells that catalyzes the iodination of T4 and T3 in thyroid hormone biosynthesis.
Thyroid peroxidase antibodies (TPOAb):
Autoantibodies produced by the body against its own thyroid peroxidase enzymes. TPOAb attacks the thyroid and disrupts thyroid function.
Thyroid stimulating hormone (TSH, Thyrotropin):
Thyrotropin is a glycoprotein hormone (MW 26,600) secreted from the anterior pituitary, that stimulates the thyroid to produce thyroid hormones T4 and T3. The glycoprotein is composed of a specific beta-subunit and an alpha-subunit similar to the alpha-subunits of LH, FSH, and hCG. Elevated levels of thyroid hormones suppress TSH production
by a classical feedback inhibition mechanism.
Thyrotropin releasing hormone (TRH):
A tripeptide hormone produced by the hypothalamus which stimulates the anterior pituitary to produce TSH.
Thyroxine (T4):
The primary hormone, 3,5,3',5'-tetraiodothyronine, produced by the thyroid. Thyroxin circulates throughout the body primarily bound to carrier proteins. Free T4 is converted to triiodothyronine (T3) in peripheral tissues.
Thyroxine binding globulin (TBG):
The major thyroid hormone transport protein in human serum.
Thyroxine binding proteins (TBP):
Three serum proteins with binding affinities for T4 and T3; thyroxine binding globulin (TBG), prealbumin, and albumin.
Tinea:
Fungal infections of the skin. Dermatophyte infection (tinea capitis, tinea of scalp; tinea corporis, tinea of the smooth skin of the body; tinea cruris, tinea of the groin; tinea pedis, tinea of the foot).
Tissue:
A group of cells organized to perform a specialized function.
Titer:
The quantity of a substance or its maximal dilution that produces a measurable reaction with another specific substance. Antibody levels (titers) are measured to determine whether they are falling or rising. Titers are expressed as the reciprocal of the highest dilution at which the substance can still be detected, e.g., a titer of 80 represents a reactive dilution of 1:80.
T-M
Thayer-Martin agar plate used to cultivate neisseria sp., eg., gonococcus.
T-lymphocytes (or T cells):
Thymus-derived lymphocytes important in cell-mediated immunity.
Tolerance:
A form of resistance to antimicrobial drugs; of uncertain clinical importance. See tolerant.
Tolerant:
Characteristic of an organism that requires a great deal more antimicrobial agent to kill it than to inhibit its growth.
TORCH:
Toxoplasmosis, Rubella, Cytomegalovirus infection, and Herpes infection; acronym used for illnesses or tests.
Toxic Granulation:
Medium to large metachromatic granules that are evenly distributed throughout the cytoplasm. May be seen in severe bacterial infections, severe burns, and other conditions.
Toxicology:
The science that deals with the study of poisons and their effects in the body, including methods of detection and treatment.
Toxic Nodular Goiter:
Caused by autonomous production of thyroid hormone by solitary or multiple thyroid nodules.
Toxigenicity:
The ability of a pathogenic organism to produce injurious substances that damage the host.
Toxin::
A poison, frequently used to refer specifically to a protein produced by some higher plants, certain animals and pathogenic bacteria, which is highly toxic for other living organisms. Such substances are differentiated from the simple chemical poisons and the vegetable alkaloids by their high molecular weight and antigenicity.
Toxoplasma gondii:
The protozoan responsible for the disease toxoplasmosis. The protozoan is an intracellular parasite, often infecting various organs of the body. It is often spread to humans from cats.
TPI:
Treponema pallidum immobilization test, a test for antibodies against the agent of syphilis that uses live treponemes.
Trace element:
Minerals required in very small amounts by living organisms. Examples are zinc, copper, cobalt, and molybdenum.
Trachoma:
Serious eye infection caused by Chlamydia trachomatis; often leads to blindness.
Trans-:
Prefix meaning through, across or beyond.
Transcription factor:
A term used to describe any protein that participates in initiating transcription. Transcription factors bind either to DNA or to other proteins that bind DNA.
Transduction:
Moving genetic material from one prokaryote to another via a bacteriophage or viral vector. The transfer of hereditary material from one cellular organism to another by a virus, with subsequent recombination of the hereditary material with the recipient's genome and the transformation of the recipient.
Transferase:
An enzyme that catalyzes the transfer of a moiety from one molecule to another.
Transformation:
The alteration of an organism's hereditary material. In microbiology, the uptake of naked DNA by an organism and the subsequent recombination of the hereditary material with the organism's genome and alteration of the organism's genetics and physiology.
Translocation:
A chromosomal abnormality which occurs when chromosomes break and the fragments rejoin to other chromosomes.
Transposon:
Genetic material from a plasmid that can move between plasmids or from a plasmid to a chromosome; so-called "jumping genes."
Transtracheal aspiration:
Passage of needle and plastic catheter into the trachea for obtaining lower respiratory tract secretions free of oral contamination.
Transudate:
Similar to exudate but with low protein content.
Treponema carateum:
Gram negative, long helical, axially filamented (motile), anaerobic, catalase negative bacterium. Causes pinta, a skin disease that resembles syphilis. Generally found in tropical America.
Treponema pallidium:
The bacterium responsible for the venereal disease syphilis.
Treponema pertenue:
Causes yaws, a skin disease that resembles syphilis. Generally found in tropical Africa.
Triacylglycerol (Triglyceride):
A 3 carbon carbohydrate, Glycerol, esterified to 3 fatty acids. See triglyceride.
Tricarboxylic acid cycle:
See Citric acid cycle and Krebs cycle.
Trichome:
A filament of cells.
Trichomonas vaginalis:
A flagellated protozoan that infects the urinary and genital tract and is responsible for the venereal disease trichomoniasis.
Trichophyton:
A fungus that cuases ringworm (tinea).
Tricyclic antidepressants:
Widely used drugs for the treatment of depression; drug overdose may cause severe toxic effects. The dexamethasone suppression test may aid in the selection of patients who
might respond well to antidepressant treatment. Blood and urine tests may be used to determine levels of these drugs in the body.
Triglyceride:
A major food fat and blood lipid (fatty substance) produced by the liver from fatty acids. Excess triglycerides are stored in adipose tissue and are used to provide energy.
Elevated blood levels of triglycerides and of cholesterol may be associated with an increased risk for atherosclerosis and related disorders, such as coronary artery disease, heart attack, and hypertension.
Triiodothyronine (T3):
A thyroid hormone primarily converted from T4, though some excretion occurs from the thyroid directly. T3 is the metabolically active hormone.
Trophic level:
Feeding level. Relative position of a population in a food chain.
Trophozoite:
Feeding, motile stage of protozoa. An infectious vegetative (growing and reproducing) form of some protozoans.
Tropical sprue:
A malabsorption syndrome occurring in the tropics and subtropics. Protein malnutrition is usually precipitated by the malabsorption, and anemia due to folic acid deficiency is particularly common. Administration of antibiotics (especially tetracycline) and folic acid usually results in remission.
Tropism:
Preferred environment or destination. In viral infection, preference for a particular tissue site (rabies viruses have a tropism for neural tissue).
Trypanosoma cruzi:
The flagellated protozoan responsible for Chagas' disease.
Trypanosoma brucei gambiense:
A flagellated protozoan responsible for African sleeping sickness.
Trypanosoma brucei rhodesiense:
A flagellated protozoan responsible for African sleeping sickness.
Trypsin:
A proteolytic enzyme that digests proteins into peptides; produced in abundance by the pancreas.
TSI:
Triple sugar iron (agar tube).
TSS:
Toxic shock syndrome.
TTA:
Transtracheal aspiration.
Tubercle:
A mass of cells (granuloma) that develops in the lungs. The mass may contain the tubercle bacillus (Mycobacterium tuberculosis).
Tularemia:
Tularemia (Rabbit or Deer Fly Fever) is an acute disease usually characterized by a primary local ulcerative lesion, regional lymphadenopathy, profound systemic symptoms, a typhoidlike febrile illness, bacteremia, or, occasionally, atypical pneumonia caused by infection by Francisella tularensis. Onset occurs suddenly, 1 to 10 (usually 2 to 4) days after contact, with headache, chills, nausea, vomiting, fever of 39.5 or 40ø C (103 or 104ø F), and severe prostration. Extreme weakness, recurring chills, and drenching sweats develop. Within 24 to 48 hours, an inflamed papule appears at the infection site (finger, arm, eye, or roof of the mouth), except in glandular or typhoidal tularemia. The papule rapidly becomes pustular and ulcerates, producing a clean ulcer crater with a scanty, thin, colorless exudate.
Hunters, butchers, farmers, fur handlers, and laboratory workers are most commonly infected. In winter months, most cases result from contact (especially during skinning) with infected wild rabbits; in summer months, infection usually follows handling of other infected animals or birds or contact with infected ticks or other arthropods. Rarely, cases result from eating undercooked infected meat or drinking contaminated water. In the Western states, ticks, deer flies, horse flies, and direct contact with animals are other sources of infection. Human-to-human transmission has not been reported. In disseminated cases, characteristic focal necrotic lesions in various stages of evolution are scattered throughout the body.
T-uptake:
A measurement of the total binding capacity of the thyroxine binding proteins for thyroid hormones.
Tumor:
An abnormal growth of cells resulting from uncontrolled cell growth.
Turner syndrome:
A chromosomal abnormality in women in whom only one X chromosome is present instead of the normal two. The condition is characterized by growth abnormalities such as dwarfism
and underdeveloped reproductive organs. Learning problems and mild mental retardation may be present. A smear of scrapings from inside the mouth may show evidence of this condition. Culture and chromosomal analysis of fetal cells from amniotic fluid can forecast this syndrome.
Turnover number:
Equivalent to Vmax, being the number of substrate molecules converted to product by one molecule of enzyme in unit time, when the substrate is saturating.
Type 1 diabetes:
A condition characterized by abrupt onset of symptoms, insulinopenia, dependence on exogenous insulin to sustain life and a tendency to develop ketoacidosis.
Type 2 diabetes:
A disorder usually characterized by a gradual onset with minimal or no symptoms of metabolic disturbance, exogenous insulin is not required to prevent ketonuria and ketoacidosis; dietary control and exercise with or without oral diabetes medications is usually effective.
Typing:
Methods of grouping organisms, primarily for epidemiological purposes (e.g., biotyping,
serotyping, bacteriophage typing, and the antibiogram).
Tzanck test:
Stained smear of cells from the base of a vesicle examined for inclusions produced by HSV or VZV.
Unidirectional:
Refers to one-way communication between an instrument and a computer.
Universal gas constant:
R = 8.314 x 10^7 ergs per degree C per mole. See gas constant.
Unsaturated:
An organic compound which contains one or more double or triple carbon-carbon bond(s).
Uracil:
A pyrimidine. A 6 member nitrogenous base used in ribonucleotides.
Urea nitrogen:
The nitrogen that is found in urea (an end product of protein metabolism) which is recognized as different from nitrogen found in blood proteins. About 50 percent of urea is nitrogen. Urea is normally present in blood and excreted in urine. Increased blood levels may be found in kidney disease, and decreased amounts are associated with liver disease.
Ureaplasma urealyticum:
A mycoplasma. Gram negative, spherical, nonmotile, wall-less, anaerobic, catalase negative bacterium. Causes urethritis.
Urease:
An enzyme which catalyzes the hydrolysis of urea into ammonia and carbon dioxide.
Urethra:
The canal that carries urine from the bladder and semen from the sex glands to the outside of the body.
Urethritis:
Inflammation of urethra, the canal through which urine is discharged (e.g., gonococcal urethritis).
URI:
Upper respiratory tract infection.
Uric acid:
A product of protein metabolism. Measurement of uric acid in the blood is most commonly performed to evaluate gout. Gout is a metabolic disease marked by an accumulation of uric acid in the blood and of its salts in joints. This causes pain and swelling in the joints, especially in the great toe.
Uridine:
A nucleoside composed of a pentose and Uracil.
Urinalysis:
The physical, chemical, and microscopic analysis of urine to detect changes in important characteristics and values that may indicate diseases or disorders. These include protein, sugar, relative acidity or alkalinity, presence of blood and microorganisms, bilirubin, and an increased number of white cells. Special urine tests, such as tests for pregnancy, are not performed as part of a urinalysis.
Urobilinogen:
A colourless compound formed in the intestines by the reduction of bilirubin. Some is excreted in the feces where it is oxidised to urobilin. Some is reabsorbed and re-excreted in the bile as bilirubin. At times, it is re-excreted in the urine, where it may be later oxidized to urobilin. Chemical name: 21H-Biline-8,12-dipropanoic acid; 2,17-diethyl-1,4,5,10,15,16,19,22,23,24-decahydro-3,7,13,18-tetramethyl-1,19-dioxo-
Urologist:
A physician and surgeon who is specially trained in the diagnosis and treatment of diseases of the male genital tract and urinary tract in patients of any age or sex.
UTI (Urinary Tract Infection):
A bacterial infection of the urethra, bladder, ureters or kidneys (part of the urinary tract). Common symptoms of a urinary tract infection include pain with urination, urinary urgency and increased frequency of urination.
Vaccination:
The inoculation of an animal or human with microorganisms or material from microorganisms in order to induce an immune response that protects the animal or human from infections by a specific microorganism.
Valence electron:
Electrons of the principal quantum level or outermost shell of an atom. Determines chemical properties of an element.
Variolation:
Vaccination against smallpox, using the smallpox virus.
Vasopressin:
A peptide hormone secreted from the posterior pituitary that affects the kidney and vascular system to conserve body water and increase blood pressure. Also known as antidiuretic hormone.
VD:
Venereal disease.
VDRL:
Veneral Disease Research Laboratory; classic nontreponemal serologic test for syphilis antibodies. Uses cardiolipin, lecithin, and cholesterol as cross-reactive antigen that flocculates in the presence of "reaginic" antibodies produced by patients with syphilis. Best test for cerebrospinal fluid in cases of neurosyphilis.
Vector:
1) An arthropod or other agent that carries microorganisms from one infected individual to another. The organism that carries and transmits a disease-causing organism. (2) The DNA (plasmid or virus) that is used to carry and clone specific pieces of DNA.
Vegetation:
In endocarditis, the aggregates of fibrin and microorganisms on the heart valves or other endocardium.
Vegetative cell:
A cell that grows and divides.
Veillonella:
Gram negative, spherical, nonmotile, anaerobic, carbon dioxide-requiring bacteria, unable to ferment carbohydrates or polymeric alcohols, with complex growth requirements.
Vesicle:
A small bulla or blister containing clear fluid.
Vibrio cholerae:
Gram negative, curved or rod-shaped, polarly flagellated, facultatively anaerobic, oxidase positive bacterium. Responsible for cholera.
Vibrio parahaemolyticus:
A cause of gastroenteritis usually acquired from seafoods.
Villi:
Minute, elongated projections from the surface of intestinal mucosa that are important in absorption.
Vincent's angina:
An old term, seldom used presently, referring to anaerobic tonsillitis.
Vinyl group:
The ethenyl group, -CH=CH2.
Viremia:
Presence of viruses in the bloodstream. A virus infection of the blood. See Septicemia.
Viroids:
Naked, double-stranded RNA molecules that infect many different types of plant cells.
Virion:
A virus. The whole viral particle, including nucleocapsid, outer membrane or envelope, and all adherence structures.
Virulence:
Degree of pathogenicity or disease-producing ability of a microorganism.
Virus:
Protein-covered nucleic acids that infect all types of cells. One of a group of minute infectious agents (much smaller than bacteria) lacking independent metabolism. It is able to replicate only within living host cells. A virus consists of a core of nucleic acid surrounded by an inner protein mantle, sometimes encircled by an outer protein envelope. Viral infections usually lead to the production of antibodies.
Viscera:
The organs within the thoracic, abdominal and pelvic cavities.
Viscus (pl., viscera):
Any of the organs within one of the four great body cavities (cranium, thorax, abdomen, and pelvis).
Vitamin:
An organic compound that is required in small amounts to be supplied in the diet. Can be subdivided into 2 classes: water soluble and organic solvent (fat) soluble.
Vitamin A (retinol):
Derived from dietary provitamin A carotenoids like b-carotene, the vitamin is in two fat-soluble forms, retinol (vitamin A1) and 3-dehydroretinol (vitamin A2). Central cleavage of b-carotene into 2 molecules of retinol is catalyzed by the intestinal mucosal enzyme b-carotene 15,15'-dioxygenase. Vitamin A is necessary for the formation of rhodopson, and chronic deficiency results in progressive degenerative blindness and skin atrophy. The RDA for men has been established at 1000 mg retinol; for women, 800 mg retinol. The RDA may be expressed as retinol equivalents (1 R.E.= 1 mg retinol = 6 mg b-carotene, etc.). Hepatotoxicity and other degenerative disease may occur with increased intake of vitamin A. High Performance Liquid Chromatography is often used to detrmine plasma values. Age-dependent Reference Intervals: 0 - 1 mo: 0.18-0.50 mg/L; 2 mo-12 yrs: 0.20-0.50 mg/L; 13-17 yrs: 0.26-0.70 mg/L; Adult: 0.30-1.2 mg/L; Retinyl Palmitate: 0 - 0.10 mg/L. Serum retinol is typically maintained until hepatic stores are almost depleted. Values > 0.20 mg/L probably represent adequate liver stores, whereas values < 0.10 mg/L may indicate severe deficiency. Vitamin A toxicity occurs when retinol exceeds the capacity of retinol binding protein (RBP). Individuals with compromised renal function can retain RBP and may have moderate retinol elevations.
Vitamin B1 (Thiamine):
Thiamine (vitamin B1) consists of substituted pyrimidine and thiazole rings linked by a methelene bridge and exists mainly in various interconvertible phosphorylated forms, chiefly thiamine pyrophosphate. Thiamine functions as a coenzyme for the oxidative decarboxylation of a-keto acids and for the formation of a-ketols. As the triphosphate, thiamine is important in energy production and the synthesis of lipids and acetylcholine.
Beriberi is the chronic deficiency disease that results from inadequate dietary intake and/or impaired absorption (e.g., in chronic alcoholism: Wernicke-Korsakoff syndrome). Clinical signs of deficiency include anorexia, weight loss, apathy, decreased short-term memory, confusion, irritability, muscle weakness and enlarged heart (signs and symptoms are usually referable to the nervous and cardiovascular systems).
The determination of total thiamine in whole blood and/or plasma is the most accurate way to evaluate the nutritional status of thiamine in humans. A common method measures Thiochrome by High Performance Liquid Chromatography (HPLC). A close correlation also exists between the development of thiamine deficiency and the decreasing excretion of thiamine as measured in a 24-hour urine specimen. Deficiency of vitamin B1 causes an increase in alpha-ketoglutarate, lactate, pyruvate, and glyoxylate. The plasma and whole blood assays do not distinguish between thiamine and its phosphate esters.
Reference Intervals for Vitamin B1 (Thiamine): Plasma: 0.2-2.0 µg/dL; Urine: Adult: >100 µg/d; Adult deficient: <40 µg/d; Whole Blood: 1.6-4.0 µg/dL
Vitamin B2 (riboflavin):
Riboflavin is a widely distributed vitamin; all plant and animal cells contain it, but there are very few rich sources. Yeast and liver have the highest concentrations, but the most common dietary sources are milk products, meat, eggs and green leafy vegetables. The RDA has been established at 1.3 mg/day for men and 1.1 mg/day for women. Toxic levels have not been established. Food flavins are released in the stomach by acidification and absorbed in the upper part of the small intestine by an active, saturable transport mechanism with the involvement of bile salts. In the mucosal cells of the intestine, riboflavin is converted to the coenzyme form flavin mononucleotide (FMN). In the portal system it is bound to plasma albumin and transported to the liver, where it is converted to the other coenzyme form, flavin adenine dinucleotide (FAD), and bound to specific proteins as flavoproteins.
Riboflavin acts as an intermediary in the transfer of electrons in numerous essential oxidation-reduction reactions, participating in many metabolic reactions of carbohydrates, fats and proteins and in energy production via the respiratory chain. Riboflavin coenzymes are essential for the conversion of pyridoxine (vitamin B6) and folic acid into their coenzyme forms and for the transformation of tryptophan to niacin. Riboflavin deficiency rarely occurs in isolation but usually in combination with deficiencies of other water-soluble vitamins. Riboflavin deficiency may cause glossitis, angular stomatitis, pruritus (itching), scaling of the skin and seborrheic dermatitis (skin rash), particularly of the scrotum. Corneal vascularization may occur in riboflavin-deficient patients and may be associated with photophobia, impaired vision, itching and a feeling of grittiness in the eyes.
Riboflavin can be measured by a microbiological or a fluorimetric method. The microbiological assay is more sensitive, but requires several days to complete. Nutritional status can be assessed by measuring urinary excretion in 24 h or in relation to creatinine excretion. However, this method has limited use as an indicator of deficiency, since it reflects current intake rather than flavin stores. Also, it is affected by other factors. Plasma levels have similar limitations. Erythrocyte levels may serve as an indicator of riboflavin stores but, as changes are extremely small, interpretation of the results is problematical. A biochemical method that gives a valid indication of riboflavin status is based on the change in activity of erythrocyte glutathione reductase (EGR), an enzyme that requires FAD as a coenzyme. During riboflavin deficiency, EGR is no longer saturated with FAD, so that enzyme activity increases when FAD is added in vitro. The difference in activity in erythrocytes with and without added FAD is called the activity coefficient.
Vitamin B12:
Vitamin B12 is a water-soluble group of cobalamins; part of the vitamin B complex. Methylcobalamin, deoxyadenosyl cobalamin, hydroxocobalamin, aquocobalamin and cyanocobalamin are representatives of this group. The predominant physiologic serum cobalamin is methylcobalamin. The cobalamins serve as coenzymes for two important physiologic functions: 1) Enzymatic conversion of homocysteine to methionine; and 2) Enzymatic conversion of methylmalonic acid to succinic acid. Cyanocobalamin, the standard for serum measurement, has a MW of 1355. Normal serum values are 200 to 900 pg/ml (as cyanocobalamin).
Like the other B vitamins, it is important for metabolism. It helps in the formation of red blood cells and in the maintenance of the central nervous system. Because the body stores several years' worth of vitamin B12, nutritional deficiency of vitamin B12 is comparatively rare. An inability to absorb vitamin B12 from the intestinal tract can, however, occur. This can be caused by a disease known as pernicious anemia. Low levels of B-12 can cause anemia as well as numbness or tingling in the extremities or other neurologic symptoms. Vitamin B12 is found in eggs, meat, poultry, shellfish, and milk and milk products. Since vitamin B12 comes primarily from animal products, people following a strict vegetarian diet ( i.e., not consuming eggs or dairy products) may require vitamin B12 supplements.
Vitamin C:
A vitamin also known as ascorbic acid. Best known for its role in maintaining connective tissue integrity, vitamin C functions as a water-soluble antioxidant (reducing agent) for reactive oxidants in activated leukocytes, lung and gastric mucosa, lipid peroxidation and others. Vitamin C is an electron donor for at least eight known human enzymes. Three are associated with collagen hydroxylation (and other connective tissue components: elastin, fibronectin, proteoglycans and elastin-associated fibrillin); two with carnitine biosynthesis; and three with hormone and amino acid biosynthesis. Vitamin C refers to both ascorbic acid and dehydroascorbic acid. Ascorbic acid is the enolic form of an a-ketolactone (2,3-didehydro-L-threo-hexano-1,4-lactone). Clinical deficiency results in scurvy, a deterioration of elastic tissue. Normal plasma values: 0.4 - 2.0 mg/dL. The RDA is 90 mg/day for men; 75 mg/day for women - add 35 mg/day for smokers. The upper limit has been established at 2 g/day, beyond which osmotic diarrhea and gastritis may occur. With ingestion of >1 g/day, <50% is absorbed from the intestine.
Vitamin D:
A steroid hormone that contributes to calcium homeostasis.
Vitamin E:
A vitamin also known as tocopherol. Best known for its antioxidant properties.
Vitamin K:
A fat-soluble vitamin especially critical for synthesis of blood clotting factors.
Voges-Proskauer test:
A chemical test for acetoin (acetylmethylcarbinol), which indicates whether or not a bacterium carries out the 2,3-butanediol fermentation. One of the IMViC tests for differentiating among enterics.
Volatile fatty acids:
Also known as short chain fatty acids; primary species include acetic, propionic and butyric acids.
Vomition:
The act of vomiting.
Vorticella:
A ciliated protozoan common in pond water.
V-P:
Voges-Proskauer.
Waldenstrom's Mcroglobulinemia:
A condition characterised by proliferation of cells resembling lymphocytes or plasma cells in the bone marrow, anaemia, increased sedimentation rate and hyperglobulinemia. Physical findings include mucosal bleeding, skin purpura and enlargement of the lymph nodes, liver and spleen.
Wax:
Lipids which are esters between long chain fatty acids and long chain alcohols.
Weil-Felix test:
Whole cell agglutination assay that uses Proteus cell surface antigens to detect crossreactive rickettsial antibodies.
Western blot:
Similar to Southern blot, except that antigenic proteins of an organism are separated by gel electrophoresis and transferred to membrane filters. Antiserum is allowed to react with the filters, and specific antibody bound to its homologous antigen is detected using labeled anti-antibody detectors. Also, a method of immobilizing DNA (viral) fragments on a support medium where they can be identified using specific antibodies. One of the applications of the procedure is the determination of the specificity of antibodies to the AIDS virus.
Whipple's disease:
A disease caused by an uncultured bacterium, Trophyrema whippeli, and characterized by diarrhea, arthritis, and neurologic manifestations.
Wild-type:
The type found in nature. The organism from which mutants (which have growth requirements, or cannot utilize a carbohydrate) have been derived in the laboratory.
Wilm's tumour:
Wilm's tumour or nephroblastoma, is a cancerous tumour of the kidney in children.
Wilm's is the most common tumour of the kidney and the most common intra-abdominal tumour in children. The exact cause is unknown, but probably develops in foetal tissue due to an underlying genetic factor. Like retinoblastoma, both sporadic and inherited forms occur.
Believed to be caused by development of homozygosity for a deletion of the tip of the short arm of chromosome 11, which is presumed to contain a tumour suppressor gene.
Wilson's disease:
An inherited (autosomal recessive) disorder where there is excessive quantities of copper in the tissues, particularly the liver and central nervous system. Wilson's disease causes the body to absorb and retain copper. The copper deposits in the liver, brain, kidneys and eyes. Complications include dementia and liver failure. Symptoms include jaundice, vomiting, tremors, weakness and slow stiff movements. Blood tests show serum ceruloplasmin is low. Medications are given to remove the excess copper from the body. Even with life-long treatment, disabling (and life-threatening) side effects are common.
Wuchereria bancrofti:
A nematode (roundworm), transmitted by mosquito, that infects the lymphatics and connective tissue. In chronic cases, it may cause elephantiasis.
Xenodiagnosis:
Procedure involving the feeding of laboratory-reared triatomid bugs on patients suspected of having Chagas' disease; after several weeks, the feces of the bugs are checked for intermediate stages of Trypanosoma cruzi.
Xerocyte:
A dehydrated red blood cell having a peculiar morphologic appearance, i.e., hemoglobin concentration at one pole of the red cell.
Yeast:
Fungi that usually exist as single-celled organisms. They may form short hyphae, but a mycelium never develops.
Yersinia pestis:
Gram negative, rod-shaped, nonmotile, facultatively anaerobic bacterium. Causes the plague.
Yellow fever:
An acute febrile illness of tropical regions, caused by a group B arbovirus and spread by a mosquito (Aedes aegypti). Characteristic features include: jaundice, black vomit and the absence of urination. Vaccination is available for travelers to endemic areas.
Zollinger-Ellison syndrome:
A gastrin-producing pancreatic tumor.
Zone of inhibition:
The area of no bacterial browth around an antimicrobial agent in the disk-diffusion test.
Zoogleal mass:
Jellylike matrix in which microorganisms may be embedded.
Zoonoses:
Diseases of lower animals transmissible to humans (e.g., tularemia).
Zwitterion:
A molecule which exhibits both positive and negative charges. An amino acid at physiological pH has both negatively charged carboxylate and positively charged amine moieties.
Zygomycetes:
Group of fungi with nonseptate hyphae and spores produced within a sporangium. A class of fungi that produces sexual spores called zygospores and asexual spores called basidiospores. An example is Rhizopus.
Zymogen:
An enzyme which is inactive until the hydrolysis of one or more of its peptide bonds. Eg., Chymotrypsinogen is a zymogen which, when hydrolyzed, becomes active as chymotrypsin.
BIBLIOGRAPHY
American Diabetes Association: Diabetes A to Z, 1996.
Barron, E. J., Lance, R. P., Finegold, S. M.: Baily and Scott's Diagnostic Microbiology, 9th Ed., St. Louis,
1994, C.V. Mosby Company.
Bauer, J.: Clinical Laboratory Methods, ed. 9, St. Louis, 1982, The.
C.V. Mosby Company.
Bushong, S.: Radiologic Science for Technologists, ed. 3, St. Louis,
1984, The C.V. Mosby Company.
Cano, R. J., Colome, J.S. : Essentials of Microbiology, St. Paul,
1988, West Publishing Company.
Funnell, M, Arnold, Marilynn: Life with Diabetes, American
Diabetes Association, 1997.
Grunhaus, L.,Dilsaver, S.,Greden, J.,and Carroll, B.:Depressive
Pseudodementia: A suggested diagnostic profile. Biol Psychiatry 18: 215-225, 1983.
Jacobs, D., Kasten, B. Jr., Demott, W., and Wolfson, W.: Laboratory Test
Handbook with DRG INDEX, Stow, Ohio, 1984, Mosby/Lexi-Comp, Inc.
Kaplan, L. and Pesce, A.:Clinical Chemistry: Theory, Analysis, and
Correlation, St. Louis, 1984, The C.V. Mosby Company.
Lab Reports for Physicians, June 1985, Nov. 1985, March 1987, and Sept.
1987.
Lennette, E., (ed): Manual of Clinical Microbiology, ed. 3, Washington,
D.C., 1980, American Society for Microbiology.
Nakamura, R., Dito, W., and Tucker, E. Ill, (eds): Clinical Laboratory
Assays, New York, 1983, Masson Publishing USA, Inc.
Pagana, K., Pagana, T.: Mosby's Diagnostic and Laboratory Test Reference, 4th. Ed, Mosby, Inc., St. Louis, Philadelphia, 1999.
Shapiro, H.: Practical Flow Cytometry, New York, 1985, Alan R. Liss.
Sonnenwirth, A. and Jarett, L.,(eds):Gradwohl's Clinical Laboratory
Methods and Diagnosis, ed. 8, St. Louis, 1980, The C.V. Mosby
Company.
Tietz, N.: Clinical Guide to Laboratory Tests, Philadelphia, 1983,
Saunders.
Abbott Diagnostics Division of Abbott Laboratories. Prepared in consultation with John D. Bauer, M.D., pathologist and
laboratory director at Faith Family Hospital and assistant professor of pathology at
Washington University School of Medicine, St. Louis, MO.
|
E-mail
Irving