| safety factor | <radiobiology> The number of times a field line goes around a torus the long way for each time around the short way. In a tokamak, this number is typically near unity in the centre of the plasma and between two and 6 or 8 at the edge. So-called because it helps to determine the degree of stability the plasma has against certain instabilities. The safety factor is the inverse of the rotational transform, and can be expressed mathematically as q = (r Bt)/(R Bp), where r and R are the minor and major radii of the torus, and Bt and Bp are the toroidal and poloidal magnetic fields. (17 Dec 1997) |
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| heat-shock factor | <cell biology, protein> A class of molecular chaperones found in both prokaryotes and in several compartments of eukaryotic cells. There is evidence that these proteins can interact with polypeptides during a variety of assembly processes in such a way as to prevent the formation of nonfunctional structures. (12 Dec 1998) Previous: heat-shock factor, heat-shock gene, heat-shock protein, heat-shock protein 27 kinaseNext: heat-shock proteins 90, heat-shock responseheat-shock factor -->heat-shock proteins 90 <cell biology, protein> A class of molecular chaperones whose members act in the mechanism of signal transduction by steroid receptors. (12 Dec 1998) |
| helper factor | A group of factors apparently produced by helper T lymphocytes that act specifically or non-specifically to transfer T-cell help to other classes of lymphocytes. The existence of specific T-cell helper factor is uncertain. (18 Nov 1997) |
| prolactin-inhibiting factor | A substance of hypothalamic origin capable of inhibiting the synthesis and release of prolactin. Synonym: prolactin-inhibiting factor, prolactin-inhibiting hormone. Origin: prolactin + G. Stasis, standing still, + -in (05 Mar 2000) |
| prolactin-releasing factor | A substance of hypothalamic origin that stimulates the release of prolactin. Synonym: prolactin-releasing factor, prolactin-releasing hormone. Origin: prolactin + L. Libero, to free, + -in (05 Mar 2000) |
| sarcoma growth factor | <growth factor> Polypeptide released by sarcoma cells that promotes the growth of cells by binding to a cell surface receptor, the sarcoma cell is therefore self sufficient and independent of normal growth control. See: growth factors. The name is no longer commonly used. (18 Nov 1997) |
| heparin binding growth factor | <growth factor> Acidic fibroblast growth factor (alpha FGF, HBGF 1) and basic FGF (beta FGF, HBGF 2) are the two founder members of a family of structurally related growth factors for mesodermal or neuroectodermal cells. Synonym: heparin binding growth factor. Acronym: FGF (18 Nov 1997) |
| properdin factor A | A component of the properdin system; a hydrazine-sensitive b1-globulin (mw about 180,000), now known to be C3 (third component of complement). (05 Mar 2000) |
| properdin factor b | <enzyme> A glycine-rich, heat-labile beta-glycoprotein found in blood. It is a proactivator of complement 3 in the alternate pathway of complement activation. Factor b is converted by factor d to c3 convertase. Registry number: EC 3.4.21.47 (12 Dec 1998) |
| properdin factor d | <enzyme> A serum protein which during the alternate pathway of complement activation converts the inactive properdin factor b to c3 convertase. Registry number: EC 3.4.21.46 (12 Dec 1998) |
| properdin factor E | A serum protein (mw 160,000) required for activation of C3 (third component of complement) by cobra venom factor. See: properdin system. (05 Mar 2000) |
| hepatocyte growth factor | <growth factor> Polypeptide mitogen originally shown to cause cell division in hepatocytes. In the liver, the main sources of hepatocyte growth factor are nonparenchymal cells. It is now clear that hepatocyte growth factor is a mitogen for a number of cell types and it is found in many cells outside the liver, including platelets. Hepatocyte growth factor is synthesised as a single chain precursor that is proteolytically cleaved to give a heavy chain (70 kD) and a light chain (30 kD) linked by a single disulphide bond. It contains multiple copies of the kringle domain. However, both the single chain precursor and the two chain forms of hepatocyte growth factor are biologically active and hepatocyte growth factor is generally isolated as a mixture of the two forms. Hepatocyte growth factor also alters cell motility and is now known to be identical to scatter factor. Acronym: HGF (18 Nov 1997) |
| scatter factor | A motility factor (motogen) isolated from conditioned medium in which human fibroblasts have been grown. It causes colonies of epithelial and endothelial cells, in culture, to separate into single cells that move apart i.e. They scatter. It has been shown to be identical to human hepatocyte growth factor, but it is not mitogenic for all cell types. (18 Nov 1997) |
| proteinase inhibitor inducing factor | See: PIIF. (18 Nov 1997) |
| protein factor | The factor (6.25) by which the nitrogen content of a protein is multiplied to give the amount of protein. (05 Mar 2000) |