| allelic exclusion | <cell biology, genetics> The process whereby one or more loci on one of the chromosome sets in a diploid cell is inactivated (or destroyed) so that the locus or loci is (are) not expressed in that cell or a clone founded by it. For example in mammals one of the X chromosome pairs of females is inactivated early in development (see Lyon hypothesis) so that individual cells express only one allelic form of the product of that locus. Since the choice of chromosome to be inactivated is random, different cells express one or other of the X chromosome products resulting in mosaicism. The process is also known to occur in immunoglobulin genes so that a clone expresses only one of the two possible allelic forms of immunoglobulin. (19 Dec 1998) |
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| gel exclusion chromatography | <investigation> A lab technique, a type of column chromatography, used to separate the components of a mixture by molecular size and to collect the molecules which are larger than a certain size. It is similar to gel filtration, small molecules are slowed or trapped by the pores in the gel beads filling the column, while large molecules, too large to fit into the pores, slide past the beads and get to the bottom of the column first. at this point, the large molecules are collected. Gel exclusion refers to the maximum size of molecule which will fit into the gel bead pores, and this lab technique is used to collect the molecules in the mixture which are larger than, or excluded from, the pores. (09 Oct 1997) |
| Pauli's exclusion principle | The theory limiting the number of electrons in the orbit or shell of an atom; that it is not possible for any two electrons to have all four quantum numbers identical. (05 Mar 2000) |
| Devine exclusion | Exclusion of the lower part of the stomach, followed by gastrojejunostomy, for treatment of duodenal ulcer. (05 Mar 2000) |
| diagnosis by exclusion | A diagnosis made by excluding those diseases to which only some of the patient's symptoms might belong, leaving one disease as the most likely diagnosis, although no definitive tests or findings establish that diagnosis. (05 Mar 2000) |
| dye exclusion test | A test to determine cell viability in which a dilute solution of certain dyes (e.g., trypan blue, eosin Y, nigrosin, Alcian blue) is mixed with a suspension of live cells; cells that exclude dye are considered to be alive while cells that stain are considered dead; it is not always an accurate test because it indicates only the structural integrity of the cell membrane. (05 Mar 2000) |
| exclusion | 1. The act of excluding, or of shutting out, whether by thrusting out or by preventing admission; a debarring; rejection; prohibition; the state of being excluded. "His sad exclusion from the doors of bliss." (Milton) "The exclusion of the duke from the crown of England and Ireland." (Hume) 2. <physiology> The act of expelling or ejecting a foetus or an egg from the womb. 3. Thing emitted. Origin: L. Exclusio: cf. F. Exclusion. See Exclude. Source: Websters Dictionary (01 Mar 1998) |
| exclusion of pupil | The condition resulting from posterior annular synechia, in which the iris is bound down throughout the entire pupillary margin, but the pupil is not occluded. Synonym: exclusion of pupil. (05 Mar 2000) |
| Abbott's method | A method of treatment of scoliosis by use of a series of plaster jackets applied after partial correction of the curvature by external force. (05 Mar 2000) |
| Abell-Kendall method | A standard method for estimation of total serum cholesterol involving saponification of cholesterol ester by hydroxide, extraction with petroleum ether, and colour development with acetic anhydride-sulfuric acid; the method avoids interference by bilirubin, protein, and haemoglobin. (05 Mar 2000) |
| activated sludge method | A method of sewage disposal in which the sewage is treated with 15% bacterially active, liquid sludge, which is produced by repeated vigorous aeration of fresh sewage to form floccules or sediment; when this flocculation process is complete, the resulting activated sludge contains large numbers of bacteria, together with yeasts, molds, and protozoa, which actively effect the oxidation of organic compounds; this mixture is piped to a sedimentation tank, the effluent from which is completely treated sewage. (05 Mar 2000) |
| Altmann-Gersh method | The method of rapidly freezing a tissue and dehydrating it in a vacuum. (05 Mar 2000) |
| Anel's method | Ligation of an artery immediately above (on the proximal side of) an aneurysm. (05 Mar 2000) |
| Antyllus' method | Ligation of the artery above and below an aneurysm, followed by incision into and emptying of the sac. (05 Mar 2000) |
| aristotelian method | A method of study that stresses the relation between a general category and a particular object. (05 Mar 2000) |