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 common topic of discussion for many years has been whether stress induces hypercoagulability and/or hyperfibrinolysis. Ten healthy volunteers were subjected to strenuous physical effort on a bicycle ergometer. Blood samples were collected 10 min before and immediately after exercise. The well-known activation of blood coagulation was demonstrated by significant shortening of the activated partial thromboplastin time, thrombin and reptilase times. However, no fibrinopeptide A (FPA) was generated, nor did the ethanol gelatin test turn positive. A significant shortening of the euglobulin lysis time was indicative of fibrinolysis but no fibrin(ogen) degradation products (FDP) could be detected. These results show that the so-called hypercoagulability is not accompanied by thrombin-mediated release of fibrinopeptide A, and suggest that the activation of coagulation does not involve fibrinogen to fibrin conversion.
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PMID:[Missing thrombinemia in the so-called hypercoagulability following physical exertion (proceedings)]. 69 96

A patient is reported who sustained bilaterial iliacus haematoma with femoral nerve palsy during treatment with constant intravenous infustion of heparin for deep venous thrombosis. She was promptly treated with operative decompression and recovered completely from the palsy. Daily examinations of the blood revealed that the plasma heparin concentration, activated partial thromboplastin time, APTT, and thrombin time all were above the therapeutic range at the time when the bleeding started, and before the initial symptoms occurred. Early operative decompression is considered to be the ideal treatment in patients who develop this complication during anticoagulant therapy.
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PMID:Bilateral iliacus haematoma with femoral nerve palsy complicating anticoagulant therapy. 69 56

We studied the activation of factor X by the intrinsic pathway of blood coagulation using a new assay of factor X activation. When factor X tritiated in its sialic acid residues is activated, activation can be measured by the release of tritiated activation peptide, and the initial rate of activation can be determined under varying conditions. In the presence of phospholipid and calcium ions, factor IXa activated factor X slowly without factor VIII, and this activation was blocked by a specific factor IX inhibitor. These data provide strong evidence that factor IXa is the enzyme responsible for factor X activation by the intrinsic pathway. The role of factor VIII was also investigated. Factor VIII could be reproducibly thrombin activated and then stabilized by the addition of 2 mM benzamidine hydrochloride; this suggests that inactivation is due to proteolysis. Neither unactivated nor thrombin-activated factor VIII produced factor X activation without factor IXa. With a constant level of factor IXa, factor X activation was directly proportional to the level of activated factor VIII. With a constant level of activated factor VIII, factor X activation was proportional to the factor IXa concentration. This observation was exploited to develop a specific, sensitive assay for factor IXa.
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PMID:Activation of factor X by factors IXa and VIII; a specific assay for factor IXa in the presence of thrombin-activated factor VIII. 69 98

The clinical and laboratory data on the 12 patients with an acquired inhibitor to factor V have been reviewed. The degree of clinical bleeding in these patients varied from none to severe, and in most patients the inhibitor was transient. The combination of a markedly prolonged partial thromboplastin time and Quick prothrombin time and failure of normal plasma to correct these tests, in the presence of a normal thrombin and prothrombin and proconvertin time, seems to be pathognomonic for a factor V inhibitor. The inhibitors have physicochemical properties of immunoglobulins and a few have been characterized as polyclonal IgG antibodies or a mixture of IgM and IgG antibodies. The etiology and pathophysiologic mechanism of their development is unknown, but there seems to be a close relationship to major surgery. When tested with inhibitor plasma, the plasmas from 9 patients with hereditary factor V deficiency from 7 unrelated families did not contain factor V antibody-neutralizing material.
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PMID:Acquired inhibitors of factor V. 70 95

This is an investigation into thromboplastin time, partial thromboplastin time, plasma thrombin time, fibrinogen, and platelets in 30 patients with severe brain injury over 7--14 days. Platelets showed a very marked initial decrease and a slow return to normal around the seventh day. Fibrinogen was initially lowered in most of the cases, and raised from the second day onward. Changes in the other laboratory values were less definite. Latent signs of consumption coagulopathy were not accompanied by bleeding disorders, or by disseminated intravascular coagulation at autopsy. The severity of laboratory value changes clearly correlated with the extent of brain damage, and was significantly higher when the patient did not survive the first week after injury.
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PMID:Disturbances of the coagulatory system in patients with severe cerebral trauma. I. 70 71

The binding of highly purified bovine coagulation factor Xa to washed bovine platelets was studied. 125I-labeled factor Xa underwent binding to a platelet receptor that became accessible only after induction of the platelet release reaction by thrombin or by the calcium ionophore A 23187. The zymogen factor X did not bind to platelets. The factor Xa binding was saturable, reversible, and correlated with the rate of thrombin formation. The number of factor Xa binding sites per platelet was 290--420 and the apparent association constant was estimated to be 2.8 x 109 to 1.0 x 1010 M-1. Diisoprophyl fluorophosphate-factor Xa bound to the same platelet receptor as factor Xa indicating that limited proteolysis of a receptor protein was not required for binding. The rate of factor Xa binding was rapid (2.1 x 10(6) to 2.9 x 10(6) M-1 s-1) and similar to that preveiously found for the rate of binding of polypeptide hormones to their receptors. Displacement of factor Xa from the platelet receptor by diisopropyl fluorophosphate-factor Xa effectively blocked thrombin formation. Low concentrations of factor Xa catalyze prothrombin activation more effectively in the presence of platelets than in the presence of phospholipid and factor V.
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PMID:Binding of bovine coagulation factor Xa to platelets. 71 67

Synthetic procedures have been developed for the preparation of peptides of arginine chloromethyl ketone and applied in the preparation of affinity labels which correspond to the -Pro-Phe-Arg- C terminus of bradykinin, a physiological cleavage site of kallikrein in kininogen. Two such reagents, Ala-Phe-ArgCH2C1 and Pro-Phe-ArgCH2C1, proved to be highly effective as well as selective affinity labels for human plasma kallikrein. For example, Pro-Phe-ArgCH2C1 inactivates plasma kallikrein 50% in 24 min at a concentration of 2 x 10(-8)M, while other trypsin-like proteases are less susceptible in inactivation than kallikrein, differing by a factor of 48 for plasmin and factors of 10(2)-10(5) for factor Xa, thrombin, and urokinase. The affinity of human plasma kallikrein for Ala-Phe-ArgCH2C1 (Ki = 0.078 micron) is about 60 times that for Ala-Phe-LysCH2C1(Ki = 4.9 micron), whereas human plasmin exhibits about the same affinity for the former affinity label (Ki = 1.3 micron) as for the latter (Ki = 0.83 micron). The rate constants for the irreversible step of the affinity labeling reaction, k2, are similar for affinity labels tested with the individual proteases: 0.35 min-1 for plasma kallikrein and 0.18 min-1 for plasmin.
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PMID:Synthesis of peptides of arginine chloromethyl ketone. Selective inactivation of human plasma kallikrein. 72 86

A lupus-type anticoagulant which causes strong inhibition of the partial thromboplastin time with kaolin (PTTK), the stypven time, and the thrombin generation tests has been investigated. All tests for platelet function were normal, as were all specific coagulation factor assays with the exception of a slightly reduced factor XI in this patient. A diethylaminoethyl-cellulose-immunoglobulin (DEAE-cellulose-IgG) fractionation of the patient's plasma produced two peaks containing inhibitory activity in the PTTK test. The first of these peaks had a cloudy appearance, suggesting the presence of immunoglobulin aggregates. Studies with IgG aggregates prepared from normal IgG and from the patient's IgG demonstrated that such aggregates were not the cause of inhibition. It was possible to neutralize the inhibitory activity of the purified IgG but not platelet-poor plasma (PPP) with a rabbit anti-IgG. The inhibition of the patient's PPP in the thrombin generation, the contact product, and the stypven time tests were corrected by the inclusion in the test system of platelets activated either by aggregation due to adenosine diphosphate (ADP) or formalin fixation and washing. These studies lend support to earlier findings that platelets interact at several sites in the coagulation cascade.
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PMID:Demonstration of a platelet bypass mechanism in the clotting system using an acquired anticoagulant. 73 36

The review of different mechanisms of non-physiological non-specific prothrombin activation is given as compared with the specific activation by the factor Xa. The use of snake venom enzymes or staphylocoagulase makes possible the thrombin generation from pathological forms of prothrombin lacking of gamma-carboxyglutamic acid and incapable of complete activation into thrombin by the specific activator, factor Xa. This fact stimulated the use of non-specific activators in medicine. Investigation of non-specific prothrombin activators made possible to reveal and to trace pathways of the formation of thrombin active site. It is demonstrated that prothrombin, like other serine proenzymes (trypsinogen, chymotrypsinogen), has already formed active site. This site can be revealed under changes of the conformation of the prothrombin molecule due to the chemical modification or the complex formation with staphylocoagulase.
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PMID:[Mechanisms of non-specific prothrombin activation]. 73 9

Seven blood coagulation tests which may indicate a state of hypercoagulability or of chronic intravascular coagulation were assayed in 106 blood samples from 50 patients with chronic renal insufficiency or after renal transplantation. The following abnormal results were obtained: increased titer of fibrin(ogen) degradation products in 60%, abnormal fibrinogen immunoelectrophoresis in 49%, shortened partial thromboplastin time and whole blood clotting time in 45 and 37% respectively, prolonged thrombin time in 34%, increased cryofibrinogen level in 21% and positive protamine sulfate gelation test in 11%. The greatest number of abnormalities was found during the first week after transplantation and during transplant rejection, and the smallest in patients with stable transplant who were anticoagulated with warfarin. Partial thromboplastin times of less than 19 sec were associated in 3/4 patients with thrombosis of the renal artery or vein or with rejection. Rejections could be identified with high probability (p less than 0.001).
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PMID:[Proceedings: Hypercoagulability and compensated intravascular coagulation in chronic kidney insufficiency and after kidney transplantation]. 76 78


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