| focal reaction | A reaction which occurs at the point of entrance of an infecting organism or of an injection, as in the Arthus phenomenon. Synonym: local reaction. (05 Mar 2000) |
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| Folin's reaction | The reaction of amino acids in alkaline solution with 1,2-naphthoquinone-4-sulfonate (Folin's reagent) to yield a red colour; useful for quantitative assay. Synonym: Folin's reagent. (05 Mar 2000) |
| foreign-body reaction | Chronic inflammation and granuloma formation around irritating foreign bodies. (12 Dec 1998) |
| Forssman antigen-antibody reaction | The combination of Forssman antibody with heterogenetic antigen of the Forssman type, as in the agglutination of sheep erythrocytes (which contain Forssman antigen) by serum from a person with infectious mononucleosis which contains Forssman antibody. Synonym: Forssman reaction. (05 Mar 2000) |
| Forssman reaction | The combination of Forssman antibody with heterogenetic antigen of the Forssman type, as in the agglutination of sheep erythrocytes (which contain Forssman antigen) by serum from a person with infectious mononucleosis which contains Forssman antibody. Synonym: Forssman reaction. (05 Mar 2000) |
| fragment reaction | A reaction used to assay the activity of peptidyl transferase. (05 Mar 2000) |
| Frei-Hoffmann reaction | <investigation> A clinical test where dead disease-causing microbes are injected into the skin to see if this causes a skin reaction. It indicates whether the patient is infected with the the injected microbe and is not used commonly. (07 Apr 1998) |
| fright reaction | After section and degeneration of the facial nerve of an animal, the denervated facial muscles contract if the animal is frightened or becomes angry; due to the release of acetylcholine into the circulation. (05 Mar 2000) |
| lengthening reaction | In the decerebrate animal, the rather sudden relaxation with lengthening of the extensor muscles when a limb is passively flexed; associated with clasp-knife spasticity. (05 Mar 2000) |
| fuchsinophil reaction | The property possessed by certain elements, when stained with acid fuchsin, of retaining the stain when treated with picric acid alcohol. (05 Mar 2000) |
| lepromin reaction | A delayed hypersensitivity reaction at the site of an intradermal injection of a lepromin, such as the Dharmendra antigen or Mitsuda antigen, in a lepromin test; the reaction's, such as the Fernandez or Mitsuda reaction, are variable, occurring in 48 hours or three to five weeks, but are uniformly negative in lepromatous leprosy, borderline leprosy, and mid-borderline leprosy. (05 Mar 2000) |
| furfurol reaction | Production of a red colour on addition of furfurol to a solution of aniline. (05 Mar 2000) |
| leukemoid reaction | A benign blood picture resembling leukaemia. For example, in infectious mononucleosis. (12 Dec 1998) |
| lid-closure reaction | A constriction of both pupils when an effort is made to close eyelids forcibly held apart. A variant of the pupil response to near vision. Synonym: Galassi's pupillary phenomenon, Gifford's reflex, lid-closure reaction, orbicularis phenomenon, orbicularis pupillary reflex, Piltz sign, Westphal's pupillary reflex, Westphal-Piltz phenomenon. (05 Mar 2000) |
| ligase amplification reaction | <molecular biology> Method for detecting small quantities of a target DNA, with utility similar to PCR. It relies on DNA ligase to join adjacent synthetic oligonucleotides after they have bound the target DNA. Their small size means that they are destabilised by single base mismatches and so form a sensitive test for the presence of mutations in the target sequence. (18 Nov 1997) |