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:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Low molecular weight heparins are increasingly prescribed in France. Prepared from standard heparin by depolymerisation, they show a markedly decreased anti IIa activity and a anti Xa/anti IIa ratio ranging from 2 to 4. Their mode of action in the coagulation system is still not well known and it is difficult to explain the mechanism of their antithrombotic effect, demonstrated in vivo. They seem to inhibit the first traces of thrombin and then counteract the priming and amplification of coagulation. Their fibrinolytic activity is also a disputed question, but seems to be lower than that of standard heparin. The pharmacological studies show a venous as well as arterial antithrombotic activity of a low molecular weight heparin on several animal models, a lower but not negligible bleeding risk as compared to unfractionated heparin. Furthermore heparin fragments have a weak interaction with platelets, which allow to foresee a greater efficacy of LMWH than standard heparin in arterial thrombosis. Some very rare cases of thrombocytopenia in patients treated with LMW heparins have been recently reported. The compared pharmacokinetics of heparins gave proof of a renal elimination of low molecular weight heparin and a bio availability of about 90% after subcutaneous injection. Many clinical studies allowed to define indications of heparin fragments in prophylactic treatment after surgery as well as in medical patients and in curative treatment in case of deep vein thrombosis. However, others studies must be carried out to define the real efficacy of such a treatment during pulmonary embolism, disseminated intravascular coagulation and myocardial infraction, or during thrombotic complications after vascular surgery.
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PMID:[The new heparins]. 131 47

Patients over 40 years of age who undergo elective orthopaedic surgery have a relatively high risk for developing post-surgical deep vein thrombosis (DVT). Prophylactic use of heparin or low molecular weight heparins can reduce the incidence of post-operative DVT by up to 80%. It is not known whether prophylaxis is achieved by inhibition of prothrombin activation or catalysis of thrombin inhibition in vivo. We determined the changes in concentrations of factor VII zymogen and thrombin-antithrombin III (the latter as an index of prothrombin activation) in the plasmas of 129 patients randomized to receive two daily subcutaneous injections of placebo or 30 mg of Enoxaparin after elective knee surgery. Enoxaparin reduced the frequency of post-surgical DVT by 70%. The concentration of factor VII zymogen had decreased by approximately 50% within 24 h after the knee surgery, followed by a gradual increase to near presurgical values. Additionally, post-Enoxaparin plasmas had statistically significant higher concentrations of factor VII zymogen than post-placebo plasmas. Post-Enoxaparin plasmas had significantly lower concentrations of endogenous thrombin-antithrombin III than comparable post-placebo plasmas. Finally, post-Enoxaparin plasmas inactivated exogenous factor Xa and thrombin more effectively than comparable post-placebo plasmas. As Enoxaparin moderated the generation of endogenous thrombin-antithrombin III after elective knee surgery, inhibition of prothrombin activation in vivo by Enoxaparin may be important for its prophylactic antithrombotic effect.
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PMID:The low molecular weight heparin Enoxaparin inhibits the consumption of factor VII and prothrombin activation in vivo associated with elective knee replacement surgery. 132 19

This study compared how Enoxaparin and unfractionated (UF) heparin influenced in vivo coagulation in patients randomized to receive, by twice daily subcutaneous injections, either 30 mg of Enoxaparin or 7500 I.U. of UF heparin after elective hip surgery. These two regimens were equally effective in reducing the incidence of post-operative deep vein thrombosis DVT. We compared the concentrations of endogenous thrombin-antithrombin III in pre- and post-surgical plasmas to determine how each prophylactic regimen influenced prothrombinase activity in vivo, and found the same concentrations of endogenous thrombin-antithrombin III in post-heparin and post-Enoxaparin plasmas. However, significantly higher concentrations of endogenous thrombin-antithrombin III were found in pre- and post-surgical plasmas of patients who developed post-operative DVT than the levels found in comparable plasmas of patients who remained DVT-negative, regardless of the drug received for prophylaxis. Human factor Xa was added to an equal volume of each patient's plasmas and the amount of added enzyme inactivated by antithrombin III measured using an enzyme-linked immunosorbent assay for factor Xa-antithrombin III. Post-heparin and post-Enoxaparin plasmas inactivated approximately 4 times more factor Xa than the pre-surgical plasmas, regardless of the clinical outcome. Thus, before and after surgery, a higher than normal in vivo prothrombinase activity may be a significant risk factor for developing post-operative DVT.
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PMID:Prophylactically equivalent doses of Enoxaparin and unfractionated heparin inhibit in vivo coagulation to the same extent. 132 20

Three groups of patients receiving oral anticoagulation treatment were evaluated. The groups consisted of patients with mechanical heart valve prosthesis (n = 60), patients after coronary bypass graft surgery (n = 60) and patients using oral anticoagulation after deep venous thrombosis or pulmonary embolism (n = 60). The patient groups were subdivided into three groups of 20 patients, each group receiving different levels of oral anticoagulation as indicated by the international normalized ratio (INR). Prothrombin fragment 1 + 2, thrombin-antithrombin III complexes and fibrin monomers were determined as coagulation activation makers. The prothrombin fragments 1 + 2 were INR dependent in all groups whereas the thrombin-antithrombin III values were only INR dependent in the group of patients with mechanical heart valve prosthesis. For fibrin monomers no correlation with the INR levels could be found. These results indicate that prothrombin fragment 1 + 2 is the only laboratory quantity of the three, which provides a suitable index of low thrombin activity during anticoagulation therapy.
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PMID:Comparison of markers of coagulation activation in patients under oral anticoagulation at different levels. 144 59

Lower rates of deep vein thrombosis have been noted following total hip replacement under epidural anesthesia in patients receiving exogenous epinephrine throughout surgery. To determine whether this is due to enhanced fibrinolysis or to circulatory effects of epinephrine, 30 patients scheduled for primary total hip replacement under epidural anesthesia were randomly assigned to receive intravenous infusions of either low dose epinephrine or phenylephrine intraoperatively. All patients received lumbar epidural anesthesia with induced hypotension and were monitored with radial artery and pulmonary artery catheters. Patients receiving low dose epinephrine infusion had maintenance of heart rate and cardiac index whereas both heart rate and cardiac index declined significantly throughout surgery in patients receiving phenylephrine (p = 0.0001 and p = 0.0001, respectively). Tissue plasminogen activator (t-PA) activity increased significantly during surgery (p < 0.005) and declined below baseline postoperatively (p < 0.005) in both groups. Low dose epinephrine was not associated with any additional augmentation of fibrinolytic activity perioperatively. There were no significant differences in changes in D-Dimer, t-PA antigen, alpha 2-plasmin inhibitor-plasmin complexes or thrombin-antithrombin III complexes perioperatively between groups receiving low dose epinephrine or phenylephrine. The reduction in deep vein thrombosis rate with low dose epinephrine is more likely mediated by a circulatory mechanism than by augmentation of fibrinolysis.
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PMID:The hemodynamic and fibrinolytic response to low dose epinephrine and phenylephrine infusions during total hip replacement under epidural anesthesia. 144 77

Plasma thrombin-antithrombin III (T-AT) complexes are reputed to be an indirect manifestation of thrombin generation, and a role for their determination in the diagnosis of deep vein thrombosis (DVT) has been advocated. In order to evaluate the accuracy of T-AT complexes assay for DVT diagnosis, in 166 consecutive outpatients with clinical suspicion of the disease, plasma concentration of T-AT complexes was measured immediately before venography by means of an enzyme-linked immunosorbent assay kit. The result of the T-AT complexes assay was elevated in 29 of the 48 patients with DVT (sensitivity, 60%). The T-AT complexes levels were within the normal range in 104 of the 118 patients with normal venograms (specificity, 88%). The positive and the negative predictive value were 67% and 85%, respectively. The authors conclude that the T-AT complexes assay is of little value for the diagnosis of DVT in outpatients.
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PMID:Failure of thrombin-antithrombin III complexes in the diagnosis of deep vein thrombosis. 146 85

Dermatan sulphate (MF 701) is a natural glycosaminoglycan that catalyses thrombin inhibition by heparin cofactor II. The aim of the study was to evaluate the efficacy and safety of MF 701 for prevention of deep vein thrombosis (DVT) in patients with hip fracture. A randomised, double-blind, placebo-controlled design was used to assess two dose regimens of MF 701 in two consecutive study phases. Treatment was started within 48 h from the trauma and continued for 14 days for non-operated patients or until the 10th postoperative day. Bilateral mandatory venography was used to assess the end-point. Eighty patients were included in the first phase (40 MF 701, 40 placebo). MF 701, 100 mg IM b.i.d., did not reduce incidence of DVT from that on placebo and did not induce any bleeding. In the second phase 126 patients were included, with a randomisation ratio of 2:1 (84 MF 701, 300 mg IM b.i.d., 42 placebo). Bilateral venography was obtained for 110 patients. The incidence of DVT was 64% (23/36) in the placebo group and 38% (28/74) in the MF 701 group (p = 0.01; odds ratio [OR] = 0.34, 95% confidence limits [CL] = 0.15-0.80p; proximal DVTs were 42% (15/36) and 20% (15/74), respectively (p = 0.02; OR = 0.36, CL = 0.15-0.89). No significant differences were found in haemorrhagic complications (2.4% in each group), blood loss from drains, blood transfusions, haemoglobin and haematocrit values. This study is the first demonstration that dermatan sulphate is a clinically effective antithrombotic agent without bleeding effects. It also provides evidence of the biological role of heparin cofactor II.
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PMID:A randomised, double-blind, placebo-controlled trial of dermatan sulphate for prevention of deep vein thrombosis in hip fracture. 162 Dec 39

We are reporting a young lady with protracted deep vein thrombosis of her left leg which turned out to be antiphospholipid (anticardiolipin) antibody syndrome of ANA positive systemic lupus erythematosus. Lupus anticoagulant was demonstrated by prolongation of activated partial thromboplastin time and Russell's viper venom time. She had no anti-thrombin III deficiency.
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PMID:Antiphospholipid antibody syndrome of systemic lupus erythematosus presenting as deep vein thrombosis. 829 83

The depolymerisation of the various chains of unfractionated heparin (UFH) by chemical or enzymatic reactions provides so-called low molecular weight heparin (LMWH), with an average molecular weight of approximately 5000 daltons. The specific biological and pharmacokinetic properties of LMWH with greater inhibition of factor Xa than of thrombin activity, less interaction with platelets, better bioavailability and a longer half life of anti-Xa activity, suggest possible new therapeutic applications. The hypothesis of reducing the risk of haemorrhage related to the antithrombin activity and the incidence of heparin-induced thrombocytopenia whilst preserving effective antithrombotic action has stimulated clinical and biological research. Clinical trials of prophylaxis of venous thrombo-embolism have been undertaken mainly in surgical patients. The results have shown identical if not better efficacy of LMWH compared to UFH in general surgical and above all orthopedic patients in whom subcutaneous heparin is only effective with a strict protocol which is difficult to adhere to in routine practice (adaptation of dosage to activated partial thromboplastin time). The risk of bleeding was not significantly lower using LMWH at the specified dosage, which in the latter indication, is twice that used in general surgery. There are many indications of prophylaxis of thromboembolism in the medical specialties but, paradoxically, LMWH has not been widely studied because of the difficulties in performing the therapeutic trials. Except in rare cases (extreme body weights, renal failure, haemorrhagic disease, thrombotic or haemorrhagic complications) the evaluation of amidolytic anti-Xa activity does not seem to be necessary. More recently, LMWH has been studied in a small number of trials for the treatment of deep venous thrombosis (DVT). The therapeutic efficacy is identical if not better than that of UFH without increasing the risk of bleeding. Biological monitoring seems to be necessary in this indication for evaluating amidolytic anti-Xa activity, which, though not a true marker of antithrombotic activity is a relatively sensitive investigation. The therapeutic values are 0.5 IU/ml to 1.0 IU/ml, 3 to 4 hours after subcutaneous injection. The conclusions of all these trials are: LMWH is relatively simple to use and, compared with UFH, has a more stable anticoagulant effect due to its pharmacokinetic properties; the therapeutic efficacy is as good as, if not better, than that of UFH; the risk of bleeding remains, therefore, the specified dosages should be respected and treatment should be monitored by anti-Xa activity when indicated; the decreased interaction with platelet function should not mask the risk of thrombocytopoenia.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Therapeutic indications of low molecular weight heparins]. 166 41

The haemostatic parameters were studied within 14 days of acute myocardial infarction (AMI) in 103 patients randomly allocated into a group receiving low-dose heparin or into a group treated without anticoagulants. Patients with isotopic evidence of deep vein thrombosis were excluded from the analysis. An important formation of thrombin-antithrombin III complex (TAT) in the plasma was detected in the early stage of the disease. It was accompanied by an activation of plasma intrinsic fibrinolysis (IF), an elevation of fibrinogen and its degradation products (FDP) and a reduction of extrinsic plasma fibrinolytic activity (EF) together with normal levels of factor X, antithrombin III (AT III), protein C and alpha-2-antiplasmin. Sequentially studies periods of the disease revealed a diminution of TAT complex concentration in the plasma on the seventh day of AMI together with a rise of the both plasma fibrinolytic activities (IF, EF) as well as an elevation of fibrinogen and its degradation products, returning to the initial values on the 14 day of AMI. In the patients treated with heparin the augmentation of TAT complex in the plasma was prolonged until the fifth day of AMI. Moreover, heparin administration was connected with significantly higher levels of AT III and protein C along with a lower concentration of factor X and FDP on the seventh day of the disease. The fluctuation of fibrinolytic activities (IF, EF) in the plasma was heparin-independent. The present results indicate that low-dose heparin treatment modulates the plasmatic fluctuation of TAT complex as well as factor X, AT III and protein C levels in patients with acute myocardial infarction.
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PMID:Fluctuation of thrombin-antithrombin III complex in patients with acute myocardial infarction: influence of low-dose heparin administration. 169 24


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