| ARI | acute respiratory illness; airway reactivity index; anxiety reaction, intense |
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| ARM | adrenergic receptor material; aerosol rebreathing method; ambulatory renal monitor; anorectal manome... |
| ARMS | adverse reaction monitoring system; amplification refractory mutation system |
| ASR | aldosterone secretion rate; antistreptolysin reaction |
| ASSR | adult situation stress reaction |
| Mitsuda reaction | A delayed hypersensitivity lepromin reaction, in the form of erythematous papular nodules, at the site of intradermal injection of Mitsuda antigen in a lepromin test. (05 Mar 2000) |
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| mixed agglutination reaction | Immune agglutination in which the aggregates contain cells of two different kinds but with common antigenic determinants; when used to identify isoantigens, the test cells are exposed to appropriate isoantibody, washed, and then mixed with indicator erythrocytes that combine with free sites on the test cell-attached isoantibody. Synonym: mixed agglutination. (05 Mar 2000) |
| mixed lymphocyte reaction | <haematology, immunology, investigation> Reaction of mitogenesis produced in T lymphocytes when allogeneic (i.e. Mixed) lymphocytes are brought together, provided they are mismatched in histocompatibility loci. Once used as a test for possible graft compatibility in human grafting. Now known that a negative reaction is a poor predictor of graft acceptance. (18 Nov 1997) |
| cockade reaction | A test of historical interest: tuberculin, either pure or diluted, is injected intracutaneously into a guinea pig; if the animal is tuberculous, a large papule with a necrotic haemorrhagic centre appears in about 24 hours (cocarde or cockade reaction). (05 Mar 2000) |
| Wassermann reaction | <investigation> A complement fixation test used to diagnose syphilis. (31 Dec 1997) |
| monocytic leukemoid reaction | Leukocytosis of varying degree, e.g., 30,000 to 40,000 per cu mm, with adult monocytes and immature forms amounting to 30% (or more) of the total number of white blood cells in the circulating blood; may be observed in association with tuberculosis, especially the first infection, miliary type. (05 Mar 2000) |
| monomolecular reaction | A reaction involving a single molecule (e.g., decomposition, intramolecular rearrangement, intramolecular oxidation or reduction), even if a catalytic agent, such as acid or alkali, is present in large excess, on a molecular basis, or is not rate-determining; such reaction's are usually first-order reaction's. Compare: molecularity. Synonym: unimolecular reaction. (05 Mar 2000) |
| colloidal gold reaction | A test (now obsolete) based on precipitation of cerebrospinal fluid protein when mixed with colloidal gold. Abnormalities in this reaction were observed in patients with syphilis, multiple sclerosis, poliomyelitis, and encephalitis. (05 Mar 2000) |
| Weidel's reaction | A reaction showing the presence of xanthine; a solution of the suspected substance in chlorine water with a little nitric acid is evaporated in a water bath, and then exposed to the vapor of ammonia; the presence of xanthine is indicated when a red or purple colour develops. (05 Mar 2000) |
| Pirquet's reaction | A cutaneous tuberculin test. (05 Mar 2000) |
| Weil-Felix reaction | <investigation> A serologic fluorescent antibody screen that indicates infection with the rickettsial bacteria which is responsible for Rocky Mountain spotted fever. This test may also be positive in brucellosis, salmonella infection and tularaemia. (27 Sep 1997) |
| Weinberg's reaction | A complement fixation test of the presence of hydatid disease. (05 Mar 2000) |
| Wernicke's reaction | In hemianopeia, a reaction due to damage of the optic tract, consisting in loss of pupillary constriction when the light is directed to the blind side of the retina; pupillary constriction is maintained when light stimulates the normal side. This sign cannot be seen with a bright light because of intraocular scatter onto the seeing half of the retina. Synonym: Wernicke's sign. (05 Mar 2000) |
| combustion reaction | <chemistry> The vigorous and exothermic reaction that takes place between certain substances, particularly organic compounds, and oxygen. (09 Jan 1998) |
| wheal-and-erythema reaction | The characteristic immediate reaction observed in the skin test; within 10 to 15 minutes after injection of antigen (allergen), an irregular, blanched, elevated wheal appears, surrounded by an area of erythema (flare). Synonym: wheal-and-flare reaction. (05 Mar 2000) |