PRINCIPLES OF TOXICOLOGY

GLOSSARY 557
antipyretic An agent that relieves or reduces fever.
aplasia Lack of development of an organ or tissue, or of the cellular products of an organ or tissue.
aplastic anemia A form of anemia generally unresponsive to specific antianemia therapy, in which
the bone marrow may not necessarily be acellular or hypoplastic but fails to produce adequate
numbers of peripheral blood elements; term is all-inclusive and probably encompasses several
chemical syndromes.
apnea Cessation of breathing; asphyxia.
aromatic A major group of unsaturated cyclic hydrocarbons containing one or more rings. These
are typified by benzene, which has a six-carbon ring containing three double bonds. These are also
known as arene compounds.
arrhythmia Any variation from the normal rhythm of heart beat, including sinus arrhythmia,
premature beat, heart block, atrial fibrillation, atrial flutter, pulsus altemans, and paroxysmal
tachycardia.
arteriosclerosis A disease of the arteries characterized by thickening, loss of elasticity, and calcification
of arterial walls, resulting in a decreased blood supply particularly to the cerebrum and lower
extremities; it often develops with aging, and in hypertension and diabetes.
arthralgia Neuralgic pain in a joint or joints.
arthroosteolysis Dissolution of bone; the term is applied especially to the removal or loss of calcium
from the bone; the condition is attributable to the action of phagocytic kinds of cells.
asbestosis A bilateral, diffuse, interstitial pulmonary fibrosis caused by fibrous dust of the mineral
asbestos; also referred to as asbestos pneumoconiosis.
asphyxiant A substance capable of producing a lack of oxygen in respired air, resulting in pending
or actual cessation of apparent life.
asthmatic response Condition marked by recurrent attacks of paroxysmal dyspnea, with wheezing
caused by spasmodic contractions of the bronchi; the response is a reaction in sensitized persons.
ataxia Failure of muscular coordination; irregularity of muscular action.
atherosclerosis A form of arteriosclerosis characterized by the deposition of atheromatous plaques
containing cholesterol and lipids on the innermost layer of the walls of large and medium-sized
arteries.
atresia A congenital absence of closure of a normal body orifice or tubular organ; the absence or
closure of a normal body orifice or tubular passage such as the anus, intestine, or external ear canal.
atrophy A decrease in the size and activity of cells, resulting from such factors as hypoxia, decreased
work, and decreased hormonal stimulation.
atropine An alkaloid forming white crystals, C17H23NO31, soluble in alcohol and glycerine. Used
as an anticholinergic for relaxation of smooth muscles in various organs, to increase the heart rate
by blocking the vagus nerve.
autonomic nervous system The part of the nervous system that regulates the activity of cardiac
muscle, smooth muscle, and glands.
auxotroph Any organism (e.g., a bacterium) that, as a result of mutation, can no longer synthesize
a substance that is necessary for its own nutrition (usually an amino acid), and thus requires an
external supply of that substance.
autosome Any chromosome that is not a sex chromosome.
B cell An immunocyte produced in the bone marrow. B cells are responsible for the production of
immunoglobulins but do not play a role in cell-mediated immunity. They are short-lived.
bactericidal Destructive to bacteria.
basophil A granular leukocyte with an irregularly shaped, relatively palestaining nucleus that is
partially constricted into two lobes; cytoplasm contains coarse, bluish black granules of variable
size.