PRINCIPLES OF TOXICOLOGY - Biology East Borneo

560 GLOSSARYcytokinesis The division of the cytoplasm of a cell following the division of the nucleus.cytoplasm The protoplasm of a cell exclusive of the nucleus, consisting of a continuous aqueoussolution (cytosol) and the organelles and inclusions suspended in it (phaneroplasm); the site of mostof the chemical activities of the cell.cytosol The liquid medium of the cytoplasm (i.e., cytoplasm minus organelles and nonmembranousinsoluble components).dalton A unit of mass, one-twelfth the mass of the carbon-12 atom. Carbon-12 has a mass of 12.011,and thus the dalton is equivalent to 1.0009 mass units, or 1.66 × 10 –24 g. Also called the atomicmass unit (amu).denaturation The destruction of the usual nature of a substance, usually the change in the physicalproperties of proteins caused by heat or certain chemicals.depolarize Loss of the ionic gradient across a nerve cell membrane, resulting in an action potentialand propagation of a nerve impulse.dermatitis Inflammation of the skin. Contact dermatitis is a delayed allergic skin reaction resultingfrom contact with an allergen. Irritant dermatitis describes irritation of the skin accompanyingexposure to a toxic substance.detoxification The metabolic process by which the toxic qualities of a poison or toxin are reducedby the body.diethylstilbestrol (DES) A synthetic estrogenic compound, C 18H 20O 2, prepared as a white odorlesscrystalline powder.dimethyl sulfoxide (DMSO) An alkyl sulfoxide, C 2H 6OS, practically colorless in its purified form.As a highly polar organic liquid, it is a powerful solvent, dissolving most aromatic and unsaturatedhydrocarbons, organic compounds, and many other substances.diplopia A condition in which a single object is perceived as two objects; double vision.direct carcinogen See primary carcinogen.dissociation constant The equilibrium constant for the reaction by which a weak acid compound isdissociated into hydrogen ions and a conjugate base, in solution. See also pK.distal alveolar region The part of the lung composed of the alveoli, or tiny air sacs, through whichgas exchange between alveolar air and blood takes place.DMSO See dimethyl sulfoxide.dose The amount of a drug needed at a given time to produce a particular biologic effect. In toxicitystudies it is the quantity of a chemical administered to experimental animals at specific timeintervals. The quantity can be further defined in terms of quantity per unit weight or per body surfacearea of the test animal. Sometimes the interval of time over which the dose is administered is partof the dose terminology. Examples are: grams (or milligrams) per kilogram of body weight (or persquare meter of body surface area).dose–response relationship One of the most basic principles of both pharmacology and toxicology.It states that the intensity of responses elicited by a chemical is a function of the administered dose(i.e., a larger dose produces a greater effect than a smaller dose, up to the limit of the capacity ofthe biologic system to respond).drug-induced toxicity Toxicities that are “side effects” to the intended beneficial effect of a drug.They represent pharmacologic effects that are undesirable but that are known to accompanytherapeutic doses of the drug.dyscrasia A morbid general state resulting from the presence of abnormal material in the blood.dysplasia Abnormal development or growth of tissues, organs, or cells.dyspnea Difficult or labored breathing.dysrhythmia Disturbances of rhythm, such as speech, brain waves, and heartbeat.