| 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 |
| Nadi reaction | Formation of indophenol blue by the action of an oxidizing enzyme present in certain cells and tissues when they are treated with a solution of alpha-naphthol and dimethylparaphenylenediamine; by this method, cells of the myelocyte series, which give a positive reaction, may be distinguished from those of the lymphocyte series, which give a negative reaction; endothelial leukocytes give a variable reaction, probably positive when they have phagocytised the debris of myeloid cells. Synonym: Nadi reaction. (05 Mar 2000) |
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| near reaction | The pupillary constriction associated with a near vision effort, i.e., with accommodation and convergence. (05 Mar 2000) |
| startle reaction | A complex involuntary response to an unexpected strong stimulus usually auditory in nature. (12 Dec 1998) |
| Neufeld reaction | Increase in opacity and visibility of the capsule of capsulated organisms exposed to specific agglutinating anticapsular antibodies. Synonym: Neufeld reaction, quellung phenomenon, quellung reaction, quellung test. Scrotal swelling, the swelling formed after the embryonic genital swellings have fused together, become spherical, and migrated caudally to the base of the penis; just before birth the testis comes to lie within it. Spielmeyer's acute swelling, a form of degeneration of nerve cells in which the cell body and its processes swell and stain palely and diffusely. (05 Mar 2000) |
| Straus reaction | A diagnostic test for glanders. Male guinea pigs are inoculated intraperitoneally with suspected material; if the glanders organism is present, it will usually set up a necrotizing inflammation in the scrotal sac within a few days and the specific organism can be confirmed bacteriologically. (05 Mar 2000) |
| neurotonic reaction | Muscular contraction continuing well after cessation of stimulation. (05 Mar 2000) |
| neutral reaction | PH of 7.00; H+ and OH- ion concentrations equal at 10-7 m at 22캜. Compare: dissociation constant of water. (05 Mar 2000) |
| stress reaction | An acute emotional reaction related to extreme environmental stress. Synonym: acute situational reaction. (05 Mar 2000) |
| ninhydrin reaction | <technique> A technique for detecting amino acids and proteins by heating a material with ninhydrin, if amino molecules are present, there is a colour reaction. (09 Oct 1997) |
| nitritoid reaction | A severe reaction resembling that following the administration of nitrites, sometimes following intravenous administration of arsphenamine or other drugs; consists of flushing of the face, oedema of the tongue and lips, vomiting, profuse sweating, a fall in blood pressure, and sometimes death. (05 Mar 2000) |
| nuclear reaction | The interaction of two atomic nuclei or of one such with a subatomic particle, or of the subatomic particles within an atomic nucleus, resulting in a change in the nature of the nuclei concerned or in the energy content of the nuclei or both, usually manifested by transmutation (accompanied by emission of alpha-, beta-, or gamma-rays) or by fission or fusion of the nuclei. (05 Mar 2000) |
| Dale reaction | The contraction of an excised intestinal loop (Schultz) or of an excised strip of virginal uterus (Dale) from a sensitised animal (guinea pig) which occurs when the tissue is exposed to the specific antigen. (05 Mar 2000) |
| dark reaction | <biochemistry, plant biology> The reactions in photosynthesis that occur after NADPH and ATP production and that take place in the stroma of the chloroplast. By means of the reaction, carbon dioxide is incorporated into carbohydrate. (18 Nov 1997) |
| decidual reaction | The cellular and vascular changes occurring in the endometrium at the time of implantation. (05 Mar 2000) |
| dehydration-condensation reaction | The joining of two molecules to each other with the release of a water molecule in the process. Compare: hydrolysis. (09 Oct 1997) |