Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Studies of the clotting mechanisms in the plasma of a Burmese python (Python molurus bivittatus) confirm earlier information that both extrinsic and intrinsic pathways of thrombin formation participate in reptilian hemostasis. Plasma fibrinogen was present at a concentration comparable to that in human plasma. Other assays were hampered by the need to use nonreptilian reagents. The activated partial thromboplastin time was shorter than was that of human plasma, thus implying the presence of prothrombin in python plasma; however, this protein could be demonstrated only in trace amounts. Similarly, only small amounts of Hageman factor (factor XII) and antihemophilic factor (factor VIII) were detected, and none of plasma prekallikrein, high-molecular-weight kininogen, and Christmas factor (factor IX). The prothrombin time was slower than that of human plasma. Factor VII was not detected, but both proaccelerin (factor V) and Stuart factor (factor X) were present. Python plasma inhibited bovine thrombin and human plasmin, but it was deficient in fibrinolytic capacity.
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PMID:Notes on clotting in a Burmese python (Python molurus bivittatus). 234 66

A family with inherited combined deficiency of factor V and von Willebrand factor (vWF) is reported. Hematological examination of 41 year-old female proband and her younger brother revealed prolonged prothrombin time and Kaolin partial thromboplastin time. The level of both factor V activity and factor V antigen markedly decreased, below 15% of normal. The decreased levels of factor VIII activity and vWF activity are also seen. Furthermore, abnormal mobilities were observed in crossed immunoelectrophoresis. The protein C, S antigens and activities, and protein C inhibitor activity were within normal. Four sons have received the 50% levels of factor V from their parents. One of them also showed the 50% of factor VIII and vWF activities. From above results, this family is thought to be a case of inherited deficiency of factor V and vWF, which are transmitted as an autosomal trait apparently.
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PMID:[A family of congenital combined deficiency of factor V and von Willebrand factor]. 236 42

Activation of blood coagulation and local fibrin deposition may contribute to tumor metastasis. We have examined the ability of four human tumor cell lines (COLO 205, HepG2, J82 and CAPAN-2) to augment the conversion of prothrombin to thrombin by factor Xa and calcium in the presence and absence of exogenous factor Va. Using a chromogenic substrate assay to assess thrombin formation, we observed that all the above cell lines accelerated prothrombin activation in the absence of exogenous factor Va. The order of effectiveness was COLO 205 greater than HepG2 greater than J82 greater than CAPAN-2. In the absence of cells, no detectable thrombin formation occurred. Pretreatment of COLO 205 and HepG2 cells with anti-human factor V IgG inhibited prothrombin activation in a dose-dependent manner, but was without effect in J82 and CAPAN-2 incubation mixtures. Factor V coagulant activity was observed in COLO 205 and HepG2 cells as well as their culture media, but was not detected in J82 and CAPAN-2 cells or their culture media. Biosynthetic labeling and immunoprecipitation studies revealed that COLO 205 and HepG2 cells constitutively synthesized factor V or a factor-V-like molecule that comigrated with human factor V/Va on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All four tumor cell lines exhibited saturation binding of exogenous human factor Va resulting in a dose-dependent enhancement of their ability to augment prothrombin activation. Our results indicate that these tumor cells can readily assemble a functional cell surface prothrombinase complex that may be important in fibrin deposition associated with the growth and metastatic progression of these, and perhaps, other tumors.
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PMID:Tumor cells augment the factor Xa-catalyzed conversion of prothrombin to thrombin. 238 53

Human coagulation factor V is a protein cofactor that is an essential component of the prothrombinase complex. A full-length factor V cDNA has been subcloned into the mammalian expression vector pDX and used to transfect COS cells. Approximately 95 +/- 4% of the recombinant human factor V (rHFV) synthesized in COS cells is secreted into the culture medium. Forty-eight hours after transfection rHFV antigen levels in the conditioned medium were 70 +/- 15 ng/mL. Factor V activity determined by fibrometer assay increased approximately 5-fold from 0.027 +/- 0.012 to 0.124 +/- 0.044 unit/mL following activation by the factor V activating enzyme from Russell's viper venom (RVV-V). A chromogenic assay specific for factor Va indicated that recombinant factor V had 3.8 +/- 1.3% of the activity of the activated protein. The estimated specific activity of the recombinant factor Va was approximately 1800 +/- 500 units/mg, which is similar to the specific activity of purified plasma factor Va of 1700-2000 units/mg. Immunoprecipitation of [35S]methionine-labeled rHFV revealed a single high molecular mass component (approximately 330 kDa). Treatment of rHFV with thrombin or RVV-V resulted in the formation of proteolytic products that were similar to those seen with plasma factor V. We have also expressed a mutant, rHFV-des-B811-1441, that lacks a large portion of the highly glycosylated connecting region that is present in factor V. Immunoprecipitation of [35S]methionine-labeled rHFV-des-B811-1441 revealed a single-chain polypeptide with Mr approximately 230 kDa. This mutant constitutively expressed 38 +/- 7% of the activity of the RVV-V-activated protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Expression and characterization of recombinant human factor V and a mutant lacking a major portion of the connecting region. 239 12

Pentosane polysulfate (PP) is a sulfated polysaccharide known to exhibit anticoagulant properties that are in part independent of antithrombin III activity. These effects have only been studied in vitro or after single injections in healthy subjects. Our objective was to evaluate the modification of hemostasis induced by a 3-day continuous infusion of PP (4 mg/kg body weight/24 hr) in 10 subjects. No hemorrhagic complication was observed in any patient. Bleeding time was not modified by the infusion, despite a slight decrease in the platelet number. Among the other parameters measured, the automated partial thromboplastin time, prothrombin time, and anti-Xa activity were the most affected by PP. The kinetics of their modifications were quite uniform: clotting times and the anti-Xa effect increased gradually until reaching steady state 24 hours after the start of the infusion. A progressive return to the pretreatment level was then observed during the 6 hours after the end of the infusion. A significant decrease in the factor V concentration was found at day 4. Finally, in contrast with other reported results, no activation of fibrinolysis was induced by PP under the conditions we used, which suggests that discontinuous administration or the route of administration of the drug influences the fibrinolytic effect. In conclusion, we show the excellent tolerance of continuous infusion of PP, detail the modifications in biologic parameters of hemostasis during and after PP infusion, and demonstrate that PP decreases factor V activity.
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PMID:Pentosane polysulfate: the effect on hemostasis of a continuous 3-day infusion. 241 Jan 77

The plasma proteinase inhibitors are relatively ineffective in the inhibition of the activity of the platelet prothrombinase complex, due to the low rates of inhibition, and possibly due to the indirect protection from the potentiating effect of the vascular endothelium. The plasma proteinase inhibitors are more effective at inhibiting thrombin, thereby preventing the feedback activation of platelets and factor V and subsequent prothrombinase complex development. This may constitute a mechanism for the control of the development of the prothrombinase complex on the platelet surface. The protein C-thrombomodulin mechanism for the destruction of factor Va activity probably constitutes a major inhibitory mechanism for the prothrombinase complex in vivo.
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PMID:Mechanisms of inhibition of platelet coagulant activity. 242 87

Eight women who were going to have an abortion between the 18th and 23 week of gestation for chromosomal abnormalities or haemoglobinopathies received intravenously 50 mg of pentosan polysulfate (PSP). Maternal results of haemostasis prior and after the injection of the drug were compared. Fetal coagulation parameters were tested on samples obtained by direct puncture of the umbilical cord under ultrasound guidance, 30 min after injection. Results were compared to those of normal fetuses at the same stage of gestation, obtained in the same conditions. In mothers' plasma, 30 min after injection, APTT was prolonged, factor Xa generation was markedly impaired, and factor V level was deeply decreased. By contrast, no modifications of these parameters were observed in fetal plasma, 30 min after the injection of PSP to their related mothers when compared to control fetuses. Thus the absence of biological modifications induced by PSP injection could demonstrate that this drug does not cross through the placenta.
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PMID:Absence of transplacental passage of pentosan polysulfate during mid trimester of pregnancy. 243 27

We investigated the activation of the nonenzymatic protein cofactors factor VIII and factor V in plasma when coagulation was initiated by thromboplastin. With sensitive bioassays, we were able to measure specifically the generation of activated factor VIII and activated factor V in plasma. Our results showed that when plasma was triggered with a relatively high concentration of thromboplastin, factor VIII and factor V were completely activated at the clotting time of plasma. However, when the generation of thrombin, but not that of factor Xa, was delayed by addition of hirudin to the plasma, factor Va was generated only at the time thrombin generation overcame the hirudin inhibition. In addition, generation of factor VIIIa correlated with thrombin generation and not with factor Xa generation. Furthermore, addition of large amounts of factor Xa to hirudinized plasma did not show detectable factor VIII or factor V activation. We concluded that in plasma activated with thromboplastin the enzyme responsible for activation of factor V and factor VIII is thrombin, not factor Xa.
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PMID:In situ-generated thrombin is the only enzyme that effectively activates factor VIII and factor V in thromboplastin-activated plasma. 250 6

With the growth in autologous blood programs and the increased scrutiny of the indications for transfusion of fresh-frozen plasma (FFP), an increase has been seen in the number of occasions on which FFP was requested and thawed but then not transfused. The coagulation properties of FFP units that were refrozen and then rethawed were therefore studied. Fifty-eight units of plasma were studied, with each experimental unit of FFP paired with an identical control unit. Experimental units were frozen, stored at -65 degrees C, thawed, stored at 1 to 6 degrees C for various periods of time up to 24 hours, and then refrozen, stored at -65 degrees C, rethawed, and stored again in the refrigerator for up to 24 hours. Control units were frozen once at the time the experimental units were first frozen and thawed once at the time of the second thaw of the experimental units. Aliquots of plasma were sampled periodically and were later batch-tested for prothrombin time (PT), activated partial thromboplastin time (aPTT), and factor V and VIII:C activity. The results of coagulation testing of the twice-frozen plasmas were always within the normal range. There was a slight but statistically valid prolongation of the PT and aPTT and a decrease in the factor V and VIII:C levels for twice-frozen plasma compared with control plasma. The greatest decline occurred in the level of factor VIII:C. The measured deterioration in coagulation of twice-frozen FFP is unlikely to be of clinical importance. Refreezing FFP may eventually prove useful for rare donor, autologous, and massive transfusion programs.
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PMID:Refreezing previously thawed fresh-frozen plasma. Stability of coagulation factors V and VIII:C. 250 13

The relative abundance of factor V, factor X and prothrombin has enabled detailed analyses of the prothrombinase complex. Determination of the primary structure for factor V has provided the basis for examination of structure-function relationships. The imminent in vitro expression of recombinant factor V will provide the opportunity for site-specific mutagenesis and a verification of these structure-function relationships. A comparison of the physical properties and primary structures for factors V and VIII has revealed extensive similarities in these two cofactor proteins. This observation indicates that a direct application of the technology developed for the analysis of prothrombinase will lead to an equal understanding of the factor Xase complex. Whether similar relationships exist for other blood coagulation enzyme complexes remains to be determined.
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PMID:Factor V: a prototype pro-cofactor for vitamin K-dependent enzyme complexes in blood clotting. 251 10


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