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)

The effect of human plasmin on human coagulation factor V was studied using isolated proteins. Incubation of factor V with plasmin resulted in a rapid increase in procoagulant activity, followed by a subsequent decline in the ability of factor V to serve as a cofactor in the prothrombinase complex. Identical results were obtained when these reactions were conducted in the presence of dansylarginine-N-(3-ethyl-1,5-pentanediyl) amide (DAPA), indicating that the changes observed could not have occurred as a consequence of cleavage by alpha-thrombin. Analysis of the products of the reaction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a temporal correlation between the rise and fall in factor V activity and the presence of several transient intermediates. These fragments are distinct from the subunits of alpha-thrombin-activated factor V (factor Va). The activation phase of the reaction was not significantly affected by the presence of phospholipid. In contrast, the rate of degradation of active fragments of factor V and the accompanying loss of activity were markedly enhanced in the presence of phospholipid vesicles. These data suggest that the action of plasmin upon factor V results in the transient formation of proteolytic fragments which express significant procoagulant activity.
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PMID:Activation/inactivation of human factor V by plasmin. 252 Dec 93

Cells of monocytic differentiation can promote proteolytic activation of factor X following binding to the adhesive receptor Mac-1. We now show that the product, factor Xa, binds to a second receptor on these cells in a Ca2+-dependent reaction. Functionally, this results in the capacity to convert prothrombin to thrombin. The factor Xa receptor was identified by monoclonal antibody (7G12) reactive with plasma factor V/Va, but selected for reactivity with THP-1 cells. It reacted with 71.2 +/- 10.1% of monocytes, bound 153,600 +/- 33,500 sites/THP-1 cell, blocked binding of 125I-factor Xa, inhibited formation of thrombin, and immunoprecipitated 125I-factor Xa chemically cross-linked to its receptor on THP-1 cells. Following surface iodination or intrinsic labeling of THP-1 cells, antibody 7G12 immunoprecipitated a 74-kDa molecular species, similar to plasma factor Va light chain. Thus, monocytes and monocyte-like cells synthesize and express a factor V/Va-like receptor for factor Xa and organize a functional prothrombinase complex. The simultaneous membrane coexpression of a factor X receptor (Mac-1) and a factor Xa receptor as demonstrated by two-color flow cytofluorometric analysis of monocytes or THP-1 cells is consistent with a sequential receptor cascade for coordinated molecular assembly of coagulation proteins on specialized cells.
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PMID:Sequential receptor cascade for coagulation proteins on monocytes. Constitutive biosynthesis and functional prothrombinase activity of a membrane form of factor V/Va. 253 28

Combined deficiency of factor V and factor VIII, a rare bleeding disorder, was found in a 43 year-old male. He had often presented manifestations of easy bruising since childhood, but none of his family had shown evidence of a bleeding tendency. We examined him and his family as far as we could and his abnormality of blood coagulation was apparent, but the members of his family were normal. The prothrombin time and activated partial thromboplastin time of this patient were prolonged, but his thrombin time was normal. Factor V and factor VIII coagulant activity were low, but von Willebrand factor antigen and activity (ristocetin cofactor activity) levels were normal. Protein C and Protein C inhibitor antigen and activity levels were also found to be normal. Following 1-deamino-8-D-arginine vasopressin (DDAVP) injection, he had immediate increases in factor VIII coagulant activity, but both von Willebrand factor antigen, activity levels and factor V coagulant activity remained low. Moreover, there was no rapid decline in factor VIII complex activity. These findings suggest that the endogenous factor VIII in this patient is metabolized normally and that at least the deficiency of factor VIII does not result from accelerated degradation in plasma.
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PMID:[DDAVP administration in a case of congenital combined factor V and factor VIII deficiency]. 260 19

Influence of the protein C activator from snake venom on blood coagulation was studied. Incubation of different concentrations of the activator with rat blood plasma resulted in a dose-dependent prolongation of the activated partial thromboplastin time (APTT). Cleavage of the protein C to the active form was detected by electrophoresis. Intravenous administration of the activator (100 mg/kg) into rats led to prolongation of APTT to 242 +/- 80%, to increase in the plasminogen activator level to 145 +/- 29% and to decrease in the factor V activity to 57 +/- 14%. When thrombosis was induced by means of administration of the thromboplastin lethal dose, pretreatment with the activator prevented animal death in 90% of cases. The effects of the activator observed appear to occur via transformation of the endogenous protein C into its active form.
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PMID:[Antithrombotic effect of protein C activator from a snake venom]. 261 27

Phenylhydrazine (PHZ) is a hemolytic agent which has been used in the treatment of polycythemia vera. Recent studies performed in our laboratory have indicated that the PHZ-induced anemia is immuno-hemolytic in etiology, and a prolonged bleeding time was present in some of the rats chronically treated with PHZ. The nature of this bleeding tendency was explored in the present experiment. PHZ was administered to rats once a week for a six week period. During this time, the animals were monitored for prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration, and individual coagulation factor levels as well as routine plasma chemistries and blood cell counts. In addition, radioimmunoassays (RIA) for prostacyclin, a platelet aggregation inhibitor, and prostaglandin (PG) E2 were performed. PHZ-treated animals displayed a significant elevation in both PT and APTT when compared with saline injected controls, although plasma fibrinogen levels were not appreciably altered. Further tests revealed a PHZ-induced decrease in prothrombin and factor V levels. In addition, a significant increase in plasma serum glutamate oxaloacetate transaminase (SGOT), lactate dehydrogenase (LDH), and alkaline phosphatase levels was observed as well as a diminution in cholesterol and triglycerides following PHZ administration. PHZ treatment also induced an elevation in prostacyclin levels and transient thrombocytopenia. These findings indicate that several factors may contribute to the prolonged bleeding time in PHZ-treated rats including a drug induced thrombocytopenia possibly associated with enhanced synthesis of autologous immunoglobulin G (IgG) against the senescent red cell antigen, and diminished synthesis of vitamin K-dependent coagulation factors which may be mediated by reduced vitamin K uptake by the hypo-cholesterolemic subjects.
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PMID:Hemostatic alterations associated with phenylhydrazine-induced anemia in the rat. 262 15

The salient abnormalities of blood coagulation found in the acute phase of Argentine hemorrhagic fever (AHF) were thrombocytopenia, prolonged partial thromboplastin time activated with kaolin, low factor VIII:C activity concurrent with high levels of von Willebrand factor, and increased values of factor V. No evidence of disseminated intravascular coagulation (DIC) was observed. Therefore, the hemostatic abnormalities detected in patients with AHF could not be attributed to DIC. There was no correlation between severity of the disease and occurrence of impairment of coagulation. Complement activation was observed during the acute phase of AHF. There was reduction of total complement and C2 activity. Antigenic levels of C1q, C3, and C5 were low; level of C4 antigen was high. Degradation products of C3 and B were demonstrated before day 11. Experimental models of AHF were developed (guinea pigs, Callitrix jacchus). These models may be useful, but they reproduced only some of the features of blood coagulation and complement abnormalities described in human AHF.
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PMID:Hemostasis and the complement system in Argentine hemorrhagic fever. 266 12

The synergistic effect of antithrombin III (ATIII), activated protein C (APC) and heparin on the tissue thromboplastin (TP)-mediated coagulation cascade was studied. APC prolonged the activated partial thromboplastin time of human plasma with increasing APC concentration but affected the prothrombin time only slightly. Neither ATIII nor heparin prolonged the prothrombin time by itself, while a mixture of APC and heparin strongly inhibited the coagulation. When the effects of APC, heparin and ATIII on the TP-mediated coagulation were examined with a solution consisting of prothrombin, factor V, factor VII, factor X and fibrinogen at physiological concentrations, the coagulation time was prolonged only slightly by the APC-heparin or ATIII-heparin mixture. However, the coagulation time was prolonged markedly by simultaneous addition of APC, ATIII and heparin to the solution. Inhibition of thrombin activity by the ATIII-APC-heparin mixture was weak as compared with that by the ATIII-heparin mixture after a 1-min incubation, but after a 2-min incubation the inhibitory activities were equal. Suppression of thrombin activity by the ATIII-APC-heparin mixture was supposed to be due to the inhibition of the interaction between ATIII and heparin on thrombin by APC because the APC-ATIII-heparin complex was detected by crossed immuno-electrophoresis but not by sodium dodecyl sulfate (SDS)-polyacrylamide electrophoresis. When the inhibitory effect of APC alone or the APC-heparin mixture on the platelet prothrombin converting activity (PPCA) was examined, heparin accelerated the PPCA inhibition by APC.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Synergistic effect of antithrombin III, activated protein C and heparin on the inhibition of the tissue thromboplastin-mediated coagulation. 275 79

In 19 patients with chronic subdural hematoma, coagulation and fibrinolysis in venous blood taken at the time of surgery and in the hematoma contents aspirated from chronic subdural hematoma were studied. Compared with coagulation results for venous blood, the hematoma contents demonstrated marked prolongation of the recalcification time, prothrombin time, and activated partial thromboplastin time, and marked reduction of clotting factor V, the hepaplastin test, prothrombin, and fibrinogen. Antithrombin III was also decreased, and fibrinopeptide A was increased in the hematomas. Fibrinolytic results demonstrated that both plasminogen and alpha 2-plasmin inhibitor were decreased, and both fibrinopeptide B beta 15-42 and fibrin and fibrinogen degradation products were increased in the hematomas. These findings indicate excessive activation of the clotting system, thrombin generation, and increased fibrinolytic activity occurring in the hematomas. From these results, excessive activation of both the clotting and fibrinolytic systems is emphasized to be the possible etiological factor for the origin and development of chronic subdural hematoma.
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PMID:Coagulation and fibrinolysis in chronic subdural hematoma. 275 76

Twenty patients with confirmed bilharzial hepatic fibrosis and similar number of matched normal controls were investigated for their plasma protein C activity, prothrombin time and partial thromboplastin time. The results showed marked decrease in plasma protein C activity together with the expected prolongation in prothrombin and partial thromboplastin times. Since protein C exhibits a controlling mechanism on haemostasis by inhibition of activated factor V, changes in plasma protein C activity will necessarily impart an effect on blood coagulation.
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PMID:Coagulation equilibrium in bilharzial hepatic fibrosis. 276 73

The procoagulant from Notechis ater niger was purified by gel filtration and anion exchange chromatography. It is a protein with an approximate mol.wt of 58,000 and in the presence of B mercaptoethanol is reduced to two chains with mol.wts of 37,000 and 23,000. The procoagulant has a pI of 7.3. The whole venom requires factor V to be present to bring about coagulation while Ca2+ and phospholipid are not essential, but when present stimulate this process. Normal prothrombin, but not decarboxyprothrombin, is converted by the venom. The activity of the procoagulant from Notechis species has been equated with factor Xa and in this study the similarity is noted, while ecarin-like characteristics in not requiring Ca2+ and phospholipid and an ability to clot heparinised plasma were also noted.
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PMID:Purification and properties of a procoagulant from peninsula tiger snake (Notechis ater niger) venom. 278 77


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