| RIF | radiological interface; release-inhibiting factor; rifampin; right iliac fossa; rosette-inhibiting f... |
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| SBF | serologic-blocking factor; specific blocking factor; splanchnic blood flow |
| SDF | slow death factor; stress distribution factor |
| SGF | sarcoma growth factor; skeletal growth factor |
| SMAF | smooth muscle activating factor; specific macrophage arming factor |
| tissue factor | <cell biology> Integral membrane glycoprotein of around 250 residues, that initiates blood clotting after binding factors VII or VIIa. (18 Nov 1997) |
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| 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) |
| transforming growth factor | <growth factor> Proteins secreted by transformed cells that can stimulate growth of normal cells. Unfortunate misnomer, since they induce aspects of transformed phenotype, such as growth in semi solid agar, but do not actually transform. Transforming growth factor alpha, 50 amino acid polypeptide originally isolated from viral transformed rodent cells, contains EGF like domain and binds to EGF receptor. Stimulates growth of microvascular endothelial cells, i.e. Is angiogenic. Transforming growth factor beta a homodimer of two 112 chains, polypeptide is secreted by many different cell types, stimulates wound healing but in vitro is also a growth inhibitor for certain cell types. The transforming growth factor family includes many of the bone morphogenetic proteins. Acronym: TGF (18 Nov 1997) |
| transforming growth factor alpha | Factor isolated in a variety of tissues including epithelium, and maternal decidua. It is closely related to epidermal growth factor (epidermal growth factor-urogasterone) and binds to the egf receptor. Tgf-alpha acts synergistically with tgf-beta in inducing phenotypic transformation, but its physiological role is unknown. (12 Dec 1998) |
| transforming growth factor beta | Factor synthesised in a wide variety of tissues including platelets, placenta, and both normal and transformed cell lines. It acts synergistically with tgf-alpha in inducing phenotypic transformation and can also act as a negative autocrine growth factor. Tgf-beta also has a potential role in embryonal development, cellular differentiation, hormone secretion, and immune function. There are at least three forms of tgf-beta: tgf-beta1, tgf-beta2, and tgf-beta1.2. The latter is a heterodimer made up of both tgf-beta1 and tgf-beta2. (12 Dec 1998) |
| transmethylation factor | <biochemistry> Esterified in the head group of phospholipids (phosphatidylcholine and sphingomyelin) and in the neurotransmitter acetylcholine. Otherwise a biological source of methyl groups. (18 Nov 1997) |
| endothelial relaxing factor | A molecule functioning as a neurotransmitter and produced by activated macrophages. It is capable of killing tumour cells, parasites, and intracellular bacteria. (05 Mar 2000) |
| endothelium-derived growth factor synthase | <enzyme> Converts l-arginine to a smooth muscle relaxing factor and stimulates the formation of cyclic-GMP Registry number: EC 1.5.1.- Synonym: edrf synthase (26 Jun 1999) |
| endothelium derived relaxation factor | <biochemistry> This compound is produced from L arginine by the enzyme nitric oxide synthase. Acts as a potent vasorelaxant via elevation of intracellular cGMP in vascular smooth muscle. Synthesis of nitric oxide is not confined to endothelium, isoforms of nitric oxide synthase are also found in brain, neutrophils and platelets. Synonym: endothelium derived relaxation factor. Acronym: NO (29 Dec 1997) |