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)

Chicken parathyroid hormone (cPTH) has been reported to stimulate adrenal steroidogenesis and to have unusual potency on traditional PTH target tissues. To evaluate these properties, chicken PTH-(1-88) has been expressed in Escherichia coli using a plasmid encoding a fusion protein which links together growth hormone, a factor Xa recognition site, and chicken PTH-(1-88). The growth hormone-cPTH fusion protein required the presence of 0.02% sodium dodecyl sulfate to remain in solution and be cleaved by factor Xa. The high performance liquid chromatography-purified recombinant cPTH-(1-88) and chemically synthesized cPTH-(1-34) had similar potency in rat osteosarcoma (ROS 17/2.8) cells, opossum kidney (OK) cells, and dispersed primary chicken kidney cells. The biologic potencies of cPTH-(1-34) and cPTH-(1-88) in radioreceptor binding and cAMP generation in both bone- and kidney-derived cell lines were less than those of human (h)PTH-(1-34). In dispersed chicken kidney cells, cAMP production by cPTH-(1-34) and cPTH-(1-88) was similar to that stimulated by human PTH-(1-34). No stimulation of steroidogenesis could be detected when recombinant chicken PTH-(1-88) was added to dispersed chicken adrenal cells. The biologic activity of recombinant chicken PTH-(1-88) purified from E. coli was comparable with that of chicken PTH-(1-88) expressed by mammalian COS cells. Thus, the full-length chicken PTH did not exhibit enhanced potency, when compared with human PTH in ROS 17/2.8, OK cell lines, and dispersed chicken kidney cells and did not demonstrate the novel steroidogenic action previously reported in adrenal cells. The successful production of chicken PTH-(1-88) will enhance our understanding of the structure-activity relationships for PTH, particularly the sequence-dependent metabolism of the hormone.
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PMID:Full-length chicken parathyroid hormone. Biosynthesis in Escherichia coli and analysis of biologic activity. 184 86

Cultured human umbilical vein endothelial cells responded to thrombin (10(-2) - 10 NIH u/ml) with a 2-5 fold increase in thromboplastin activity. The maximum response was reached after 4 hr in serum-free medium. The effect of thrombin was fully inhibited by the presence of 50% (v/v) fetal calf serum or more in the medium, by preincubation of thrombin with hirudin or by treatment of thrombin with N-bromosuccinimide or phenylmethylsulfonyl fluoride. The thrombin-induced thromboplastin activity was inhibited by incubation of the cells with cycloheximide (2 micrograms/ml) or actinomycin D (2 micrograms/ml) showing that the response depended on de novo protein and RNA synthesis. It was also suppressed by exposure of the cells to two different phosphodiesterase inhibitors, 3-butyl-1-methyl-xanthine (5 X 10(-4) M) and rac-4 (3-butoxy-4-methoxybenzyl)-2-imidazole (5 X 10(-4) M), to the transmethylation inhibitors 3-deazaadenosine (10(-5) M) and 1-homocysteine thiolactone (2 X 10(-5) M) in combination and to the intracellular calcium antagonist 8-(N,N-diethylamino)-octyl 3,4,5,-tri-methoxybenzoate hydrochloride (8 X 10(-5) M). Our results suggest that small amounts of thrombin can induce thromboplastin synthesis in endothelial cells in vitro and that this synthesis probably is regulated by the intracellular level of cAMP, by cytoplasmic Ca2+ and possibly also by transmethylation reactions.
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PMID:Thrombin induces thromboplastin synthesis in cultured vascular endothelial cells. 241 48

Prostacyclin is able to inhibit the development of platelet prothrombinase activity. This inhibition, which also occurs with dibutyryl cAMP, is presumably due to the ability of prostacyclin to prevent the formation of a negatively charged phospholipid surface at the exterior half of the platelet membrane. Generation of this procoagulant surface, as induced by platelet activation with collagen plus thrombin, does not depend on thromboxane A2 formation.
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PMID:The inhibition of platelet prothrombinase activity by prostacyclin. 609 19

Confluent monolayers of human umbilical vein endothelial cells in culture responded with a 5-fold increase in thromboplastin (tissue factor) synthesis when exposed to 12-O-tetradecanoyl-phorbol-13-acetate (TPA) (50 ng/ml) or endotoxin (ETX) (25 micrograms/ml) for 16 hr. This induced thromboplastin synthesis was markedly inhibited by exposure of the cells to two different phosphodiesterase inhibitors, methylisobutylxanthine (MIX) and rac-4(3-butoxy-4-methoxybenzyl)-2-imidazole idinone (RO-20-1724) and to the transmethylation inhibitors 3-deazaadenosine (DZA) and 1-homocysteine thiolactone (Hcy) in combination. It was slightly (TPA) or not at all (ETX) inhibited upon exposure of the cells to the intracellular calcium antagonist 8-(N,N-diethylamino)-octyl 3,4, 5-trimethoxybenzoate hydrochloride (TMB-8). However, in the presence of MIX TMB-8 had a moderate additional inhibitory effect on TPA-induced thromboplastin response. The thromboplastin response of endothelial cells in vitro thus probably depends on transmethylation events for its full expression. It is also strongly modulated by the intracellular level of cAMP.
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PMID:Inhibition of the thromboplastin response of endothelial cells in vitro. 620 61

Human monocytes in vitro respond to various agents (immune complexes, lectins, endotoxin, the divalent ionophore A 23187, 12-O-tetradecanoyl-phorbol 13-acetate [TPA], purified protein derivative [PPD] of Bacille Calmette-Guerin) with an increased synthesis of the protein component of thromboplastin. The effect of cyclic AMP and cyclic GMP on this response has been studied. Dibutyryl-cyclic AMP, prostaglandin E1 and the phosphodiesterase inhibitors 3-butyl-1-methyl-xanthine (MIX) and rac-4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro 20-1724), separately and in combination have a pronounced inhibitory effect on the response to immune complexes and PPD, and a moderate effect on the response to endotoxin and lectins. The effect on TPA response and on the response to A 23187 was slight. Dibutyryl-cyclic GMP (1 mM) gave a slight inhibition of the TPA and IC response, but had essentially no effect on the response to other inducers. The intracellular cAMP level increased when monocytes were incubated with IC, TPA or A 23187 followed by a decrease to basal levels within 1-2 hr, whereas lectin (PHA) and PPD did not induce such changes. The cAMP response to endotoxin varied. Stimulation with IC induced an increase in monocyte cGMP levels, whereas the other stimulants did not cause such changes.
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PMID:Effect of cyclic AMP and cyclic GMP on thromboplastin (factor III) synthesis in human monocytes in vitro. 632 Apr 87

Endothelial cells (EC) in culture produce a procoagulant identified as thromboplastin when stimulated with 12-O-tetradecanoyl-phorbol-13-acetate, phytohemagglutinin, endotoxin, thrombin, histamine or epinephrine. Inducible thromboplastin generation most likely depends on de novo synthesis of RNA and the protein component of thromboplastin, apoprotein III. It is further probably regulated by intracellular mechanisms involving cAMP, transmethylation and calcium ions. The EC thromboplastin response is enhanced in lymphocyte-EC and platelet-EC cocultures and thromboplastin becomes partly available on the cell surface. Levels of procoagulant activity are reached which clearly may be of clinical importance if similar levels appear in vivo.
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PMID:Thromboplastin synthesis in endothelial cells. 653 8

Exposure of endothelial cells (ECs) to thrombin or cytokines leads to major changes in their biochemical properties, which confer procoagulant activities. Stimulated ECs express the procoagulant glycoprotein tissue factor (TF). Although some TF is expressed on the apical surface of the cells, most is deposited as a cryptic pool in the subendothelial matrix. This matrix-associated TF may play a role in thromboembolic complications associated with alterations in the integrity of the EC monolayer. We have measured TF activity on the surface and in the subcellular matrix of human saphenous vein ECs in culture, by assaying the TF-dependent formation of activated factor X in the presence of factor VII. The subcellular matrix was prepared by exposure of ECs to ammonium hydroxide. Incubation of ECs for 4 h with 1 U/ml human thrombin induced TF expression on the apical cell surface and in the matrix. Activity in the matrix was 4.1 +/- 0.5 times greater than on the cell surface. Pentoxifylline inhibited the expression of TF both on the cell surface and in the matrix. The EC50 was on the order of 3.9 mM in both cases. No signs of cell toxicity were observed at this concentration of pentoxifylline. Similar effects were obtained with trequinsin (HL 725), a phosphodiesterase inhibitor, with an EC50 of 40 microM. This suggests that an increase in cAMP may be involved in the mechanism of action of pentoxifylline. Inhibition of TF deposition in the matrix may be important in the prevention of thromboembolic episodes in conditions where ECs either retract or are removed by major injury.
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PMID:Inhibitors of phosphodiesterase (pentoxifylline, trequinsin) inhibit apical and subcellular matrix expression of tissue factor in cultured human endothelial cells. 869 70

We have studied the effect of dietary supplementation with 25 mg (0.0025% of the total diet) of a lipophilic fraction (LF) from Panax ginseng on rat platelet aggregation induced by collagen or thrombin, and on blood coagulation. When platelets prepared from 15% corn oil plus LF-administered rats (COLF) were stimulated by thrombin (0.1 units/ml) and collagen (100 micrograms/ml), the cGMP level was significantly increased as compared with those from 15% corn oil only-administered rats (CO). The levels of cAMP in COLF were decreased by thrombin, but was increased by collagen. Furthermore, the levels of both cGMP and cAMP were also increased by the exogenous addition of LF to thrombin- and collagen-stimulated platelets. These results mean that LF increases cGMP directly and cAMP indirectly, and thus inhibits thrombin- or collagen-induced rat platelet aggregation. Both the thrombin time (TT) and activated partial thromboplastin time (APTT) were prolonged more in citrated platelet-poor plasma from COLF than in that from CO. The level of lipids such as triglyceride, total cholesterol, high density lipoprotein-cholesterol and low density lipoprotein-cholesterol was decreased in serum from COLF more than in that of CO. Thus, these results suggest that dietary LF regulates the levels of cGMP and cAMP, and prolongs the time interval (TT, APTT) between the conversion of fibrinogen to fibrin. Accordingly, our data demonstrate that dietary LF has an antithrombotic effect in vivo.
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PMID:Effects of dietary supplementation of lipophilic fraction from Panax ginseng on cGMP and cAMP in rat platelets and on blood coagulation. 895 Nov 59

Thrombocytopenia is observed with a frequency of up to 2% in patients treated with glycoprotein (GP) IIb/IIIa antagonists. We recently provided evidence that thrombocytopenia is caused by antibody binding to drug-induced conformational changes in GP IIb/IIIa. Here, we report that a murine monoclonal antibody binds to GP IIb/IIIa in an antagonist-dependent manner and activates platelets. Platelet stimulation is associated with a disruption of the phospholipid asymmetry, resulting in the assembly of catalytic active intrinsic Xase and prothrombinase complexes. Further mechanistic studies revealed that this response is (I) mediated in cis, (II) not associated with the formation of prothrombotic microparticles, and (III) requires intact platelet signaling and (IV) is blocked by increases in cAMP. The prothrombotic response is not observed using F(ab')2 fragments and is blocked by incubation of platelets with neutralizing antibodies to the platelet FcgammaRIIa receptor (CD 32).Taken together, these observations suggest that GPIIb/IIIa antagonist-dependent antibody binding to the platelet fibrinogen receptor has the propensity to lead to CD32-mediated platelet activation and accelerated platelet clearance, leading to thrombocytopenia.
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PMID:CD32-dependent platelet activation by a drug-dependent antibody to glycoprotein IIb/IIIa antagonists. 1262 36

We studied the effect on both platelet aggregation and blood coagulation, known to be major risk factors in thrombogenesis, of proteins from hen egg yolk (EP). EP potently inhibited collagen-induced human platelet aggregation in a dose-dependent manner. Furthermore, EP has a synergistic effect on the inhibition of human platelet aggregation with both molsidomine, an inhibitor of cGMP-specific phosphodiesterase, and theophylline, an inhibitor of cAMP-specific phosphodiesterase. These results indicate that the active mode of EP might be involved in elevation of the levels of both cGMP and cAMP. Prothrombin time and activated partial thromboplastin time were potently prolonged by EP. These data suggest that EP prolongs the time interval between the conversion of fibrinogen to fibrin. Accordingly, these findings demonstrate that EP might have antithrombotic effects by inhibiting platelet aggregation and fibrin formation.
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PMID:Effects of proteins from hen egg yolk on human platelet aggregation and blood coagulation. 1451 41


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