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)

A factor IX inhibitor was assayed by using a modification of the Bethesda assay for factor VIII inhibitors. The incubation time was shortened to 15 min. A screening method using the activated partial thromboplastin time was used after sample incubation to determine the correct dilution of the patient's plasma to assay for residual factor IX activity prior to determining the inhibitor titer, thereby significantly reducing the number of factor assays needed. This screening method was also shown to be applicable to assaying a factor VIII inhibitor.
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PMID:Modification of the Bethesda assay for factor VIII or IX inhibitors to improve efficiency. 314 12

Prothrombin time (PT), activated partial thromboplastin time (APTT) and plasma procoagulant activities were studied in 38 children with nephrotic syndrome in the presence or absence of prednisolone therapy. PT was normal but APTT was prolonged during relapse in untreated patients. Increased factors V, VII, VIII, XI and XIII in both treated and untreated and factor IX in treated patients, as well as decreased factors X and XII in untreated patients, were observed during relapse. These coagulation factor changes were unrelated either to the dose of prednisolone or underlying renal histology and normalized with clinical remission. However, plasma levels of factors II, V, VIII, IX, X and XI were still increased in treated patients. The data suggest that corticosteroids shorten APTT, raise both intrinsic and extrinsic factors, and therefore have favorable and unfavorable effects on the coagulation system in children with nephrotic syndrome.
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PMID:Effect of corticosteroids on coagulation factors in children with nephrotic syndrome. 315 90

A case of ruptured cerebral aneurysm with hemophilia B is reported, and discussion is made concerning the management of mild type hemophilia in surgical operations. A 41-year-old male came to our hospital with complaints of severe headache, vomiting, and transient consciousness disturbance. His dentist said the patient had a mild bleeding tendency when he was 30 years old, however no postoperative hemorrhage was repeated in appendectomy in his childhood. He also had had no episodes of spontaneous bleeding. CT scan on admission showed subarachnoid hemorrhage, and angiography revealed a ruptured aneurysm at the trifurcation of the left middle cerebral artery. His coagulation screening tests (bleeding time, clotting time, prothrombin time, and activated partial thromboplastin time) were normal. An aneurysmal neck clipping was carried out, and operators did not detect any bleeding tendency during the surgery. CT scan on the next day showed no remarkable finding. On the third postoperative day, right hemiparesis occurred. Left putaminal hemorrhage took place. His coagulation tests and FDP were also normal. The hematoma was partially evacuated. After the second operation his condition was good, and rehabilitation program started. On the 15th hospital day his consciousness deteriorated suddenly, and CT scan showed a massive epidural hematoma on the left. His prothrombin time elongated mildly, but other tests were normal. Coagulation factors VIII and IX were examined and the factor IX was 22.5% of control. He was thought to be a patient with mild type hemophilia B. Despite a third operation for hematoma removal he died on the 20th hospital day. Mild type hemophilia B does not bleed spontaneously.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Unusual postoperative hemorrhage in a patient with ruptured aneurysm and hemophilia B]. 321 Dec 77

Methods employing chromogenic substrates for the photometric determination of prothrombin time have several advantages over conventional coagulometric methods. We evaluated the analytical qualities of two recently introduced reagents for the photometric determination of prothrombin time. The assays were performed on a centrifugal analyser. Both reagents showed good precision, even with sample volumes of 10 microliters or 12 microliters. The stability of the reagents during storage was investigated at 4 degrees C, 25 degrees C and 37 degrees C. The chromogenic reagent, which contains thromboplastin from human placenta, was compared with a coagulometric method, which includes ox-brain thromboplastin: coagulation activities calculated from International Normalized Ratio values showed good correlation and conformity over the whole test range. The other chromogenic reagent contains thromboplastin from rabbit brain; outside the therapeutic range for oral anticoagulation the results obtained with this reagent showed poor agreement with those obtained with the coagulometric method. Both chromogenic reagents were sensitive to reduced concentrations of coagulation factors of the extrinsic pathway and nearly insensitive to low factor IX concentrations. The results of the photometric test paralleled those of the clotting method during oral anticoagulation therapy.
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PMID:Automation of the prothrombin time assay on a centrifugal analyser using two different chromogenic substrate reagents. 323 61

Venom sac extract of the Oriental hornet significantly prolongs the prothrombin time and the activated partial thromboplastin time both in vitro in human plasma and in vivo in cats. Activity of factors VIII and IX in plasma is reduced to less than 1% within 5 min even with 1 microgram of venom sac extract per ml. The activity of purified factor VIII, as well as semipurified factors IX and X, in factor IX complex was also significantly reduced after incubation with the venom. The decrease of factors II, V, VII, X, XI and XII activity to 9%, 11%, 11%, 29%, 1.7% and 0.7% of normal, respectively, is dose- and time-dependent. Thrombin time, plasma fibrinogen and fibrin degradation products are not affected. The anticoagulant activity is not reversed by dialysis and is abolished completely by heating; it resides mainly in fractions with mol.wts above 5000. The venom has a proteolytic activity on 14C-globin which is partially inhibited by trasylol and ethylenediaminetetraacetic acid. Thus, the venom sac extract exhibits both serine and metaloprotease activities which may affect the activity of the plasma coagulation factors.
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PMID:Effect of venom sac extract of the Oriental hornet (Vespa orientalis) on coagulation factors. 323 1

Whether the factor VII/tissue factor complex that forms in tissue factor-dependent blood coagulation must be activated to factor VIIa/tissue factor before it can activate its substrates, factor X and factor IX, has been a difficult question to answer because the substrates, once activated, back-activate factor VII. Our earlier studies suggested that human factor VII/tissue factor cannot activate factor IX. Studies have now been extended to the activation of factor X. Reaction mixtures were made with purified factor VII, X, and tissue factor; in some experiments antithrombin III and heparin were added to prevent back-activation of factor VII. Factor X was activated at similar rates in reaction mixtures containing either factor VII or factor VIIa after an initial 30-sec lag with factor VII. In reaction mixtures with factor VII a linear activation of factor X was established several minutes before cleavage of 125I-labeled factor VII to the two-chain activated molecule was demonstrable on gel profiles. Adding antithrombin III and heparin blocked activation of factor X by factor VII/tissue factor but not by factor VIIa/tissue factor. When the antithrombin III and heparin were added 1 min after the other reagents, factor VII/tissue factor activation of factor X was not blocked. These data suggest that factor VII/tissue factor cannot activate measurable amounts of factor X over several minutes. Overall, our results support the hypothesis that a rapid preferential activation of factor VII bound to tissue factor by trace amounts of factor Xa is a key early step in tissue factor-dependent blood coagulation.
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PMID:Activation of factor VII bound to tissue factor: a key early step in the tissue factor pathway of blood coagulation. 326 69

A human solvent-detergent (SD)-treated factor IX concentrate has been produced from cryoprecipitate-poor plasma using DEAE-Sepharose CL-6B and heparin-Sepharose CL-6B chromatography. The DEAE eluate was incubated with an SD mixture [0.3% tri(n-butyl) phosphate-1% Tween 80, 6-h at 24 degrees C] which was found to inactivate, in less than 1 h, more than 3.8 log10 of vesicular stomatitis virus and more than 4.8 log10 of Sindbis virus; the SD was removed by a subsequent heparin adsorption step. The specific activity of the concentrate was 10.9 +/- 1.3 IU factor IX: c/mg protein (n = 15). The factor IX coagulant to antigen ratio was 0.7 +/- 0.1. The concentrate was essentially free of factors II, VII and X, and protein C. The usual major contaminants of prothrombin complex concentrate (PCC) were absent: the concentrate contained about 94% alpha-1 proteins, and only 4 major proteins were resolved by SDS-PAGE (respective apparent molecular weight: 130, 86, 76 and 69 kilodaltons), and by crossed immunoelectrophoresis against an anti-PCC serum. The nonactivated partial thromboplastin time was equivalent to that of PCC; the product was devoid of factor IXa, of other activated procoagulant factors and of coagulant-active phospholipids (removed with SD in the heparin breakthrough fraction). Animal studies using the Wessler test and acute-toxicity test in rabbits revealed no adverse side effects. SD treatment could thus be used to inactivate viruses in factor IX concentrate and improve the safety of replacement therapy in hemophilia B.
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PMID:Large-scale production and properties of a solvent-detergent-treated factor IX concentrate from human plasma. 326 37

Factor VIIa participates in blood clotting by activating factor X and/or factor IX by limited proteolysis. The proteolytic activity of factor VIIa is absolutely dependent on a lipoprotein cofactor designated tissue factor. We have examined the ability of purified preparations of human plasma high density, low density and very low density lipoproteins, as well as apolipoproteins A-I and A-II, to inhibit the factor VIIa-tissue factor mediated activation of either factor X or factor IX before and after treatment of the lipoprotein preparation with polyclonal antibody directed against partially-purified human plasma extrinsic pathway inhibitor (EPI). In the absence of anti-EPI IgG, HDL, LDL, VLDL, and apolipoprotein A-II noncompetitively inhibited factor X activation by factor VIIa-tissue factor with apparent Ki values of 3.39 mumol/L, 124 nmol/L, 33 nmol/L, and 10.5 mumol/L, respectively. Apolipoprotein A-I had no effect on this reaction. The inhibitory activity of HDL, LDL, VLDL, and apolipoprotein A-II in this reaction was unaffected by the presence of high levels of anti-EPI IgG. In the absence of exogenous factor Xa, none of the lipoproteins studied inhibited the activation of factor IX using the tritiated peptide release assay. In the presence of added factor Xa (1 nmol/L), LDL and VLDL, but not HDL and apolipoprotein A-II, inhibited the activation of factor IX by factor VIIa-tissue factor. This inhibition was completely blocked by prior incubation of the lipoprotein with anti-EPI IgG indicating association of EPI with these particles. Taken collectively, our data indicate that HDL, LDL, and VLDL, at or below their plasma concentration, each selectively inhibits the factor VIIa-tissue factor mediated activation of factor X by a mechanism that appears to be distinct from extrinsic pathway inhibitor. These lipoproteins may not only play a role in the regulation of extrinsic blood coagulation, but may also selectively promote the activation of factor IX by factor VIIa-tissue factor in vivo at low tissue factor concentrations.
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PMID:Evidence that plasma lipoproteins inhibit the factor VIIa-tissue factor complex by a different mechanism that extrinsic pathway inhibitor. 331 45

Three hydrolases from the crude venom of the Malayan pit viper (Akistrodon rhodostoma) can be differentiated. The first, which we designate ARH alpha, is the well-known fibrinogenolytic enzyme ancrod. The second, ARH beta, which has not been described previously, is identified by its electrophoretic mobility after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), by its ability to hydrolyze H-D-phenylalanyl-L-piperyl-L-arginyl-rho-nitroanilide, and by inhibition of its activity by diisopropyl phosphorofluoridate. The third, ARH gamma, also previously not described, has been purified by using gel permeation and ion-exchange chromatography and preparative PAGE. Chemical, electrophoretic, and hydrodynamic data indicate that it is a single-chain, nonglobular glycoprotein with a molecular weight of 25,600. ARH gamma catalyzes the degradation of several plasma vitamin K dependent coagulation factors, including factor IX, factor X, prothrombin, and protein C. The products are electrophoretically similar to factor IXa beta, factor Xa, thrombin, and activated protein C, respectively. However, these products contain little or no enzymatic activity. ARH gamma-degraded factor IX, factor X, prothrombin, and protein C can be subsequently activated by factor XIa, Russell's viper venom X coagulant protein, crude taipan snake venom, and thrombin, respectively. The N-terminal sequence of the peptides resulting from the ARH gamma digest of porcine factor IX shows that at least three bonds are hydrolyzed: (1) at position 152, seven residues from the Arg145-Ala146 factor XIa cleavage site; (2) at position 167 within the factor IX activation peptide; and (3) at position 177, three residues from the Arg180-Val181 factor XIa cleavage site. The degradation of factor IX by ARH gamma is not affected by several serine protease inhibitors. ARH gamma catalyzes the degradation of both the heavy and light chains of porcine factor VIII which results in the inability of thrombin to activate factor VIII. ARH gamma also catalyzes the degradation of porcine antithrombin III which abolishes its ability to inhibit thrombin. These findings may have relevance to studies of hemostatic derangements following envenomation by this snake. Additionally, several novel coagulation factor derivatives have been generated for structure-function studies.
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PMID:Degradation of coagulation proteins by an enzyme from Malayan pit viper (Akistrodon rhodostoma) venom. 332 4

In the present study, human factor X and factor IX were each digested with chymotrypsin, and the Gla-peptide from each protein was purified by QAE-Sephadex chromatography. The effect of each Gla-peptide on the activation of human prothrombin by a complex of factor Xa, phospholipid, and calcium was studied using an amidolytic assay for generated thrombin. Prothrombin activation was half-maximally inhibited by factor X Gla-peptide at a concentration of 0.7 microM. Factor IX Gla-peptide was markedly less inhibitory and inhibited this reaction half-maximally at a concentration of 3.7 microM. Kinetic analyses revealed that the factor X Gla-peptide inhibited this reaction in an apparent competitive manner, whereas the factor IX Gla-peptide yielded an exponential Dixon plot. Heat decarboxylation experiments revealed that 3-4 gamma-carboxyglutamic acid residues are critical for the expression of inhibitory activity in each peptide. These studies indicate that, in spite of their structural homology, the ability of each of these Gla-peptides to act as a prothrombinase inhibitor is markedly different.
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PMID:Inhibition of prothrombin activation by factor X and factor IX Gla-peptides. 337 73


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