| 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) |
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| 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) |
| delayed reaction | A local or generalised response that begins 24 to 48 hours after exposure to an antigen. See: cell-mediated reaction. Synonym: contact hypersensitivity, delayed hypersensitivity, late reaction, tuberculin-type hypersensitivity. (05 Mar 2000) |
| delayed reaction experiment | A method of measuring memory: a stimulus is presented and removed before the organism is permitted to respond to it; the interval during which the stimulus is absent, providing the organism responds correctly, is an indication of the length of memory. (05 Mar 2000) |
| symptomatic reaction | An allergic response similar to the original one, but occurring after the use of a test or therapeutic dose of an allergen or atopen. (05 Mar 2000) |
| depot reaction | Reddening of the skin at the point where the needle entered, in the subcutaneous tuberculin test. (05 Mar 2000) |
| depressive reaction | 1. A lowering or decrease of functional activity. 2. <psychiatry> A mental state of depressed mood characterised by feelings of sadness, despair and discouragement. Depression ranges from normal feelings of the blues through dysthymia to major depression. It in many ways resembles the grief and mourning that follow bereavement, there are often feelings of low self esteem, guilt and self reproach, withdrawal from interpersonal contact and somatic symptoms such as eating and sleep disturbances. Origin: L. Depremere = to press down (18 Nov 1997) |
| dermotuberculin reaction | A cutaneous tuberculin test. (05 Mar 2000) |
| detoxification reaction | Reactions taking place generally in the liver or kidney in order to inactivate toxins, either by degradation or else by conjugation of residues to a hydrophilic moiety to promote excretion. (18 Nov 1997) |
| diazo reaction | The reaction of diazotised sulfanilic acid with bilirubin to form azobilirubin, which forms the basis of quantitating the amount of bilirubin in biological fluids. See: van den Bergh's test. Synonym: Ehrlich's diazo reaction. (05 Mar 2000) |