Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human monocytes synthesize the protein component of thromboplastin and express increased procoagulant activity when appropriately stimulated in vitro. The activity reached maximum between 2 and 20 h depending on the stimulant used. The presence of lymphocytes (lymphocyte: monocyte ratio 4:1) enhanced this activity only very slightly (up to 1.3-fold) at the time of maximal monocyte thromboplastin expression. Lymphocytes had a marked potentiating effect on PHA stimulation that became clearly evident after 12 h, at which time the thromboplastin response of monocytes alone to PHA had subsided. The thromboplastin activity of monocytes remained at a high level for 24-40 h in the presence of PHA or endotoxin and lymphocytes, but lymphocytes did not influence the early (4-8 h) thromboplastin response. Neither did lymphocytes alter the magnitude or the time course of the response when monocytes were stimulated with PPD, TPA or immune complexes. The lymphoblastoid cell line Molt 4 (T cell like) was as effective as lymphocytes, Daudi cells (B cell like) were slightly less effective. The enhancement of thromboplastin activity in PHA-stimulated monocytes could be induced also by conditioned medium from PHA stimulated lymphocytes. We conclude that freshly isolated monocytes synthesize thromboplastin directly upon interaction with a stimulant, and are not dependent on a helper effect of lymphocytes or lymphocyte products. Such help, however, will prolong the ability of the monocytes to respond.
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PMID:Is lymphocyte co-operation necessary for thromboplastin synthesis by human monocytes? 661 64

Endothelial cells from human umbilical veins produce a procoagulant identified as thromboplastin (tissue factor, factor III) when stimulated with the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA), phytohaemagglutinin (PHA) or endotoxin, Inducible thromboplastin synthesis (i.e. synthesis of the protein component of thromboplastin, apoprotein III) was totally inhibited by cycloheximide and actinomycin D, indicating that de novo protein and RNA syntheses are necessary. Serum enhanced the induced apoprotein synthesis. Of the total thromboplastin activity in homogenates of stimulated endothelial cells, about 50--70% was available on the cell surface for interaction with other coagulation factors, inactivation by trypsin and neutralization with antiserum against apoprotein III. Induced synthesis of thromboplastin in endothelial cells was 2--7-fold enhanced by the presence of several other cell types in optimal ratio 4--10 cells per endothelial cell. Some of these cell types were themselves thromboplstin producers (U-937, U-937-4), some were not inducible (lymphocytes, granulocytes and the lymphoblast lines Daudi and Molt 4). This enhancing effect was also seen with cell-free culture supernatants, but these were generally somewhat less effective than the intact cells. Supernatants derived from cells cultured in the presence of TPA, PHA or endotoxin were in most cases more effective than supernatants from unstimulated cells.
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PMID:Cellular cooperation in endothelial cell thromboplastin synthesis. 684 29