PRINCIPLES OF TOXICOLOGY

GLOSSARY 571
cells have both endothelial and reticular attributes and the ability to take up particles of colloidal
dyes.
risk assessment A methodologic approach in which the toxicities of a chemical are identified,
characterized, and analyzed for dose–response relationships, and a mathematical model is applied
to the data to generate a numerical estimate that can serve as a guide to allowable exposures.
risk estimation Mathematical modeling of the animal and/or human toxicity data, combined with
evaluation of human exposures, so as to estimate the probability or incidence of effects on human
health.
risk management The process of applying a risk assessment to the conditions that exist in society,
so as to balance exposures to toxic agents against needs for products and processes that may be
inherently hazardous.
safety factor A factor that presumably reflects the uncertainties inherent in the process of extrapolating
data about toxic exposures (i.e., intraspecies and interspecies variations). With this approach,
an allowable human exposure to a compound can be determined by dividing the no-observableeffect
level (NOEL) established in chronic animal toxicity studies by some safety factor. Also called
uncertainty factor.
sarcoma A cancer that arises from mesodermal tissue (supporting or connective tissue).
sclerodermatous skin change A chronic hardening and shrinking of the connective tissues of any
part of the body, including the skin, heart, esophagus, kidney, and lung. The skin may become
thickened and hard, and the condition may be generalized and rigid, and pigmented patches may
occur, limited to the distal parts of the extremities and face, or to the digits, or localized to oval or
linear areas a few centimeters in diameter.
sclerosis A thickening or hardening of a body part, as of an artery, especially from excessive
formation of fibrous interstitial tissue.
sensitization reaction An immunologic response to a chemical. The mechanism of immunization
involves the following events: initial exposure of an animal to a chemical substance, an induction
period in the animal; and the production of a new protein termed an antibody. The initial exposure
does not result in cellular damage but causes the animal to be “sensitized” to subsequent exposure
to the chemical. Exposure of the animal to the same chemical on a subsequent occasion will lead
to the formation of sensitized antigen, which will react with the preformed antibodies and lead to
a response in the tissues in the form of cellular damage.
SGOT Serum glutamic–oxaloacetic transaminase. An enzyme found in the liver and muscle tissue
and used to detect early membrane permeability as part of a test of the activity of enzymes present
in liver cells.
SGPT Serum glutamic–pyruvic transaminase. An enzyme used in the identification and measurement
of the activity of enzymes present in liver cells. SGPT is found in the liver and heart tissues.
It is an indicator of early membrane permeability, as is SGOT.
silicosis A type of pneumocomosis due to the inhalation of the dust of stone, sand, or flint containing
silicon dioxide. It results in the formation of generalized nodular fibrotic changes in both lungs.
site of action See locus of action.
SNARL Suggested no-adverse-response level. A measure of toxicity established by the National
Research Council.
somatic cell Any cell of a plant or an animal other than a germ cell. Also called body cell.
specific receptor Macromolecular constituent of tissue capable of combining reversibly with a
compound by means of chemical bonds; the tissue element with which a compound interacts to
provide its characteristic biologic effect.
spermatozoa The mature fertilizing gamete of a male organism, usually consisting of a round or
cylindrical nucleated cell, a short neck, and a thin, motile tail. Also called sperm cell.
spirometer An instrument for measuring the air taken into and exhaled from the lungs.