| 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) |
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| 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) |
| digitonin reaction | The reaction of naturally occurring steroids with 3b-hydroxyl groups with digitonin, a steroid glycoside, resulting in the formation of an insoluble precipitate; useful in determining the presence of cholesterol and ergosterol. (05 Mar 2000) |
| Dische reaction | The assay of DNA by means of the blue colour formed with diphenylamine in acid (Dische reagent). (05 Mar 2000) |
| dissociative reaction | Reaction characterised by such dissociative behaviour as amnesia, fugues, sleepwalking, and dream states. (05 Mar 2000) |
| DNA-driven reaction | <molecular biology> A lab technique to mark highly-repeated DNA sequences with a radioactive RNA tracer, by having a much larger amount of complementary DNA molecules than radioactive RNA tracer molecules. (09 Oct 1997) |
| dopa reaction | A dark staining observed in fresh tissue sections to which a solution of dopa has been applied, presumably due to the presence of dopa oxidase in the protoplasm of certain cells. Synonym: Bloch's reaction. (05 Mar 2000) |
| id reaction | An allergic manifestation of candidiasis, the dermatophytoses, and other mycoses characterised by itching, vesicular lesions that appear in response to circulating antigens at sites that are often far distant from the primary fungal lesion itself. See: dermatophytid, -id. (05 Mar 2000) |