| checkerboard assay | <procedure> Variant of the Boyden chamber assay for leucocyte chemotaxis introduced by Zigmond. By testing different concentrations of putative chemotactic factor in nongradient conditions, it is possible to calculate the enhancement of movement expected due simply to chemokinesis and to compare this with the distances moved in positive and negative gradients. Good experimental design thus allows chemotaxis to be distinguished from chemokinesis. (21 May 1997) |
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| chloramphenicol acetyltransferase assay | <investigation> A lab technique used to determine whether a given fragment of DNA has a promoter on it to encourage transcription to occur, by attaching the gene (called the CAT gene) which codes for the CAT enzyme to it, and observing whether the CAT enzyme is produced. (05 Jan 1998) |
| Grunstein-Hogness assay | A procedure for identifying plasmid clones by colony hybridization. (05 Mar 2000) |
| christmas factor assay | A test used to measure the activity of a blood clotting factor IX (Christmas factor). This test may be used to evaluate excessive bleeding. Abnormally low factor IX assays may be seen in the following conditions: congenital deficiency of factor IX, fat malabsorption, heparin administration, cirrhosis, vitamin K deficiency and warfarin administration. (27 Sep 1997) |
| clonogenic assay | In vitro culturing of neoplastic cells to test their radiosensitivity or chemosensitivity, and probable clinical efficacy of a therapeutic agent. (05 Mar 2000) |
| competitive binding assay | General term for an assay in which a binder competes for labelled versus unlabelled ligand; following separation of free and bound ligand, the ligand (the analyte assayed) is quantitated by relating bound and unbound ratios to known standards. See: enzyme-linked immunosorbent assay, radioreceptor assay, immunoassay, enzyme-multiplied immunoassay technique, radioimmunoassay. Synonym: displacement analysis, saturation analysis. (05 Mar 2000) |
| complement binding assay | A test for the detection of immune complexes. (05 Mar 2000) |
| complement haemolytic activity assay | Usual screening assay for complement. Dilutions of the serum to be tested are added to antibody-coated erythrocytes and the percentage of lysis is measured. The values are expressed by ch50, haemolytic complement units per milliliter, which is the dilution of serum required to lyse 50 percent of the erythrocytes in the assay. (12 Dec 1998) |
| plaque assay | 1. <investigation> Assay for virus in which a dilute solution of the virus is applied to a culture dish containing a layer of the host cells, convective spread is prevented by making the medium very viscous. After incubation the plaques, areas in which cells have been killed (or transformed), can be recognised and the number of infective virus particles in the original suspension estimated. 2. Assay for cells producing antibody against erythrocytes or against antigen that has been bound to the erythrocytes. The cell is surrounded by a clear plaque of haemolysis. Basic principle behind the assay is the same as for the virus plaque assay. (18 Nov 1997) |
| haemolytic plaque assay | <investigation> A haemolytic plaque assay is a lab technique used to show that certain antibodies are secreted by antibody-making cells when these cells are mixed with red blood cells. The mixture is spread onto a plate of agar, if a plaque appears, it means that the red blood cells have been destroyed (by haemolysis) by the antibodies. (09 Oct 1997) |
| Hageman factor assay | A test used to measure the activity of a blood clotting factor XII. This test may be used to evaluate excessive bleeding. Low factor XII may be seen in cases of congenital deficiency of factor XII, heparin administration and liver disease. (27 Sep 1997) |
| progesterone receptor assay | The progesterone receptor test (PgR assay) checks the tumour for its hormone status. (16 Dec 1997) |
| hemizona assay | <investigation> The hemizona assay is a laboratory test of the ability of sperm to penetrate into a human egg, first the egg is split in half, then one half is tested against the husband's sperm and the other half against sperm from a fertile man. (09 Oct 1997) |
| scintillation proximity assay | Assay system in which antibody or receptor molecule is bound to a bead that will emit light when _ emission from an isotope occurs in close proximity, i.e. From a radioactively labelled ligand. Avoids the need for scintillant in order to measure the amount of bound isotope and thus the amount of antigen or ligand present. (18 Nov 1997) |
| hormone receptor assay | A diagnostic test to determine whether a breast cancer's growth is influenced by hormones or if it can be treated with hormones. (09 Oct 1997) |