| toxic substances | A chemical or mixture of chemicals that presents a high risk of injury to human health or to the environment. (05 Dec 1998) |
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| toxic tetanus | Tonic spasms caused by strychnine or other tetanic. Synonym: toxic tetanus. (05 Mar 2000) |
| toxic unit | A unit formerly synonymous with minimal lethal dose but which, because of the instability of toxins, is now measured in terms of the quantity of standard antitoxin with which the toxin combines. See: L doses, minimal lethal dose. Synonym: toxin unit. (05 Mar 2000) |
| epidermal necrolysis, toxic | An exfoliative disease of skin seen primarily in adults and characterised by flaccid bullae and spreading erythema so that the skin has the appearance of being scalded. It results primarily from a toxic reaction to various drugs, but occasionally occurs as a result of infection, neoplastic conditions, or other exposure. (12 Dec 1998) |
| abscopal effect | A reaction produced following irradiation but occurring outside the zone of actual radiation absorption. (05 Mar 2000) |
| additive effect | <biochemistry, chemistry> An additive effect is the overall biological effect two chemicals acting together and which is the simple sum of the effects of the chemicals acting independently. Compare: antagonism. (15 Jan 1998) |
| adverse effect | This is an abnormal or harmful effect to an organism caused by exposure to a chemical. It is indicated by some result such as death, a change in food or water consumption, altered body and organ weights, altered enzyme levels, or visible illness. An effect may be classed as adverse if it causes functional or anatomical damage, causes irreversible change in the homeostasis of the organism, or increases the susceptibility of the organism to other chemical or biological stress. A non-adverse effect will usually be reversed when the organism is no longer being exposed to the chemical. (09 Oct 1997) |
| Anrep effect | A small transient positive inotropic effect of abrupt increases of systolic aortic and left ventricular pressures related to recovery from transient subendocardial ischemia (e.g., cold pressor test). (05 Mar 2000) |
| antagonistic effect | This is the consequence of one chemical (or group of chemicals) counteracting the effects of another chemical, the opposing chemicals cancel out each other's effects. (09 Oct 1997) |
| Arias-Stella effect | Focal, unusual, decidual changes in endometrial epithelium, consisting of intraluminal budding, and nuclear enlargement and hyperchromatism with cytoplasmic swelling and vacuolation; may be associated with ectopic or uterine pregnancy. Synonym: Arias-Stella effect, Arias-Stella reaction. (05 Mar 2000) |
| Auger effect | <physics> Transition of an electron in an atom from a discrete electronic level to an ionised continuous level with the same energy. Synonym: autoionisation. (13 Jan 1998) |
| autokinetic effect | In psychology, the apparent drifting about of a small, fixed, spot of light which is being observed in a dark room. (05 Mar 2000) |
| Bernoulli effect | <physics> The decrease in fluid pressure that occurs in converting potential to kinetic energy when motion of the fluid is accelerated, in accordance with Bernoulli's law. Applied in water aspirators, atomisers, and humidifiers in which a gas is accelerated across the end of a narrow, fluid-filled orifice. (05 Mar 2000) |
| Bohr effect | <physiology> Decrease in oxygen affinity of haemoglobin when pH decreases or concentration of carbon dioxide increases. (18 Nov 1997) |
| Bowditch effect | Homeometric autoregulation of cardiac function induced by changing heart rate. (05 Mar 2000) |