| anaphylactic reaction | <immunology> A serious, often life-threatening allergic reaction that is characterised by low blood pressure, shock (poor tissue perfusion) and difficulty breathing. (27 Sep 1997) |
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| anaplerotic reaction | <biochemistry> An enzyme-catalysed chemical reaction that recharges the supply of intermediate molecules in various metabolic reactions such asthe citric acid cycle. (09 Oct 1997) |
| antigen-antibody reaction | The phenomenon, occurring in vitro or in vivo, of antibody combining with antigen of the type that stimulated the formation of the antibody, thereby resulting in agglutination, precipitation, complement fixation, greater susceptibility to ingestion and destruction by phagocytes, or neutralization of exotoxin. See: skin test. (05 Mar 2000) |
| anxiety reaction | A sudden bout of anxiety that is often accompanied by the features of hyperventilation (tingling around mouth and in fingertips, rapid breathing, faintness or fainting). (27 Sep 1997) |
| Arias-Stella reaction | 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) |
| arousal reaction | Change in pattern of the brain waves when the subject is suddenly awakened and becomes alert. (05 Mar 2000) |
| Arthus reaction | <dermatology, immunology> A localised inflammation due to injection of antigen into an animal that has a high level of circulating antibody against that antigen. A haemorrhagic reaction with oedema occurs due to the destruction of small blood vessels by thrombi. It may occur, as in Farmer's Lung, as a reaction to natural exposure to antigen. (18 Nov 1997) |
| arthus-type reaction's | Reaction's in man and other species that result from the same basic immunologic (allergic) mechanism which evokes, in the rabbit, the typical Arthus phenomenon. See: immune complex disease. (05 Mar 2000) |
| Ascoli reaction | A method for confirming the diagnosis of anthrax by means of a precipitin reaction which indicates the presence of heat-stable Bacillus anthracis antigen in the extracted tissue. (05 Mar 2000) |
| associative reaction | A secondary or side reaction. (05 Mar 2000) |
| basic reaction | Any test by which an alkaline reaction is recognised, such as the change of red litmus paper to blue, an excess of hydroxide ions over hydrogen ions in aqueous solution as indicated by a pH value greater than 7 (at 22캜). Compare: dissociation constant of water. Synonym: basic reaction. (05 Mar 2000) |
| beam-beam reaction | <radiobiology> Fusion reaction which occurs from the collision of two fast ions originating in injected neutral beams. (09 Oct 1997) |
| beam-plasma reaction | <radiobiology> Fusion reaction which occurs from the collision of a fast beam ion with a thermal plasma ion. (09 Oct 1997) |
| beam-wall reaction | <radiobiology> Fusion reaction which occurs from the collision of a fast beam ion with an ion embedded in or adsorbed onto the reactor wall. (09 Oct 1997) |
| Bence Jones reaction | <investigation> The classic method of identifying Bence Jones protein. This protein precipitates from urine in the range of 45 to 70 degrees Centigrade. It goes into solution at temperatures above or below this range. Used in the diagnosis of multiple myeloma. Less commonly, this test is positive in Waldenstrom's macroglobulinaemia, chronic lymphocytic leukaemia and amyloidosis. (27 Sep 1997) |