| HSTF | heat shock transcription factor; human serum thymus factor |
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| LAF | laminar air flow; Latin American female; leukocyte-activating factor; lymphocyte-activating factor |
| LF | labile factor; lactoferrin; laryngofissure; Lassa fever; latex fixation; left foot; left forearm; le... |
| LRF | latex and resorcinol formaldehyde; liver residue factor; luteinizing hormone-releasing factor |
| LRSF | lactating rat serum factor; liver regenerating serum factor |
| termination factor | <molecular biology> Any of several proteins in the cytosol that cut a completed polypeptide loose from a ribosome. (13 Jan 1998) |
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| testis-determining factor | The product of a gene on the short arm of the Y chromosome that is responsible for production of testes. (05 Mar 2000) |
| thymic factor, circulating | <chemical> A thymus-dependent nonapeptide found in normal blood. Stimulates the formation of e rosettes and is believed to be involved in T-cell differentiation. Chemical name: Thymulin (12 Dec 1998) |
| thymic lymphopoietic factor | A glycoprotein (MW about 12,000) that has been extracted from thymus; this thymus-produced hormone(s) confers immunological competence on thymus-dependent cells and induces lymphopoiesis. (05 Mar 2000) |
| thyroid-stimulating hormone-releasing factor | <protein> See thyrotrophic releasing hormone. (18 Nov 1997) |
| thyrotoxic complement-fixation factor | A form of thyrotoxin; an antigen found most readily in thyroid tissue from thyrotoxic individuals; known to be chemically and immunologically distinct from thyroglobulin, and fixes complement when combined with antibody related to the gamma-globulin fraction of serum. With the exception of extremely small concentrations, the antigen is rarely found in normal glands or in diseased glands that are not associated with thyrotoxicosis; it is probably an intracellular substance (possibly a constituent of the "microsomal fraction"), and does not contain iodine in significant quantity. Not related to the complement-fixation reaction occurring with serum in Hashimoto's disease, in which the antigen is thyroglobulin. (05 Mar 2000) |
| thyrotropin-releasing factor | Former name for thyrotropin-releasing hormone. (05 Mar 2000) |
| tissue factor | <cell biology> Integral membrane glycoprotein of around 250 residues, that initiates blood clotting after binding factors VII or VIIa. (18 Nov 1997) |
| tissue weighting factor | In radiation protection, a factor weighting the equivalent dose in a particular tissue or organ in terms of its relative contribution to the total deleterious effects resulting from uniform irradiation of the whole body. See: effective dose. (05 Mar 2000) |
| elongation factor | <biochemistry> Peptidyltransferase components of ribosomes that catalyse formation of the acyl bond between the incoming amino acid residue and the peptide chain. There are three classes of elongation factor: EF1_ (EF Tu in prokaryotes) binds GTP and aminoacyl tRNA, delivering it to the A site of ribosomes. EF 1_ (EF Ts) helps in regeneration of GTP EF 1_. EF 2 (EF G) binds GTP and peptidyl tRNA and translocates it from the A site to the P site. Diptheria toxin inhibits protein synthesis in eukaryotes by adding an ADP ribosyl group to a modified histidine residue (dipthamide) in elongation factor II. (18 Nov 1997) |
| transcription factor | <molecular biology> Protein required for recognition by RNA polymerases of specific stimulatory sequences in eukaryotic genes. Several are known that activate transcription by RNA polymerase II when bound to upstream promoters. Transcription of the 5S RNA gene in Xenopus by RNA polymerase III is dependent on a 40 kD protein TFIIIA that binds to a regulatory site in the centre of the gene and was the first protein found to exhibit the metal binding domains known as zinc fingers. (17 Mar 1998) |
| transcription factor ap-1 | A multiprotein complex composed of the products of c-jun and c-fos proto-oncogenes. These proteins must dimerise in order to bind to the ap-1 recognition site, also known as the tpa-responsive element (tre). Ap-1 controls both basal and inducible transcription of several genes. (12 Dec 1998) |
| transcription factor, sp1 | Promoter-specific RNA polymerase II transcription factor that binds to the gc box, one of the upstream promoter elements (upe) in mammalian cells. The binding of sp1 is necessary to initiate transcription in the promoters of a variety of cellular and viral genes including c-ha-ras and HIV. (12 Dec 1998) |
| transfer factor | A dialysable factor obtained from sensitised T-cells by freezing and thawing, that may possibly immunopotentiate animals.The transfer of specific immunity from one animal to another has been claimed. (18 Nov 1997) |
| transforming factor | The DNA responsible for bacterial transformation. (05 Mar 2000) |