| PRF | partial reinforcement; patient report form; perforin; plasma recognition factor; pontine reticular f... |
|---|---|
| PSF | peak scatter factor; peptide supply factor; point spread function; pseudosarcomatous fasciitis |
| RIF | radiological interface; release-inhibiting factor; rifampin; right iliac fossa; rosette-inhibiting f... |
| SBF | serologic-blocking factor; specific blocking factor; splanchnic blood flow |
| SDF | slow death factor; stress distribution factor |
| 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) |
| 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) |
| endothelium-derived relaxing factor | A labile humoral agent released by the vascular endothelium that mediates the relaxation induced by some vasodilators such as acetylcholine and bradykinin. Edrf also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. These actions are believed to be mediated through stimulation of guanylate cyclase and the consequent elevation of cyclic guanosine 3',5'-monophosphate. Edrf is thought to be nitric oxide or a ready source of it. The factor is believed to be unstable and acts only locally in vivo. (12 Dec 1998) |