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

---

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

Three species of oversulfated fucans having different sulfate contents (the ratio of sulfate/total sugar residues, 1.38-1.98) were prepared by chemical sulfation of a fucan sulfate (sulfate/sugar ratio, 1.28) isolated from the brown seaweed Ecklonia kurome. The anticoagulant activities of the oversulfated fucans were compared with that of a parent fucan with respect to activated partial thromboplastin time (APTT) and thrombin time (TT) in plasma. The respective activities (for APTT and TT) of the oversulfated fucans increased to 110-119% and 108-140% of the original values with increase in their sulfate content. The anticoagulant activity with respect to APTT (173 units/mg) of an oversulfated fucan (sulfate/sugar ratio, 1.98) was higher than that (167 units/mg) of heparin used as a standard. The heparin cofactor II-mediated antithrombin activity of the oversulfated fucans also increased significantly with increase in sulfate content. The maximum activity was higher than those of the parent fucan and heparin. However, the increment of the anticoagulant and the antithrombin effects gradually decreased with increase in the sulfate content of the fucans. These results indicate that the effects of the fucan sulfate are dependent on its sulfate content until a plateau is reached.
...
PMID:Anticoagulant and antithrombin activities of oversulfated fucans. 139 92

The decay rate of thrombin in plasma is shown to be linearly proportional to the concentration of antithrombin III (AT III), not only in the absence but also in the presence of heparin. This is a consequence of partitioning of heparin between AT III and other plasma proteins. In previous articles were calculated the prothrombin converting activity assuming a fixed concentration of AT III. Since AT III is consumed during the clotting process, prothrombinase activity is more accurately approximated using an algorithm that counts with the decrease of the AT III concentration. It is shown this leads to higher prothrombinase activities. The (absence of) inhibition of prothrombin conversion by prothrombinase in the presence of heparins found with the previous method is also found using the new algorithm. From the results presented it is evident that characteristic parameters of heparin action have to be normalised to the AT III concentration. On this basis we define a Standard Independent Unit of the antithrombin activity of heparin.
...
PMID:The consumption of antithrombin III during coagulation, its consequences for the calculation of prothrombinase activity and the standardisation of heparin activity. 141 57

Recombinant antithrombin produced by baby hamster kidney (BHK) or Chinese hamster ovary (CHO) cells was separated into two fractions, containing comparable amounts of protein, by affinity chromatography on matrix-linked heparin. Fluorescence titrations showed that the more tightly binding fraction had a heparin affinity similar to that of plasma antithrombin (Kd approximately 20 nM), whereas the affinity of the more weakly binding fraction was nearly 10-fold lower (Kd approximately 175 nM). Analyses of the heparin-catalysed rate of inhibition of thrombin further showed that the fractions differed only in their affinity for heparin and not in the intrinsic rate constant of either the uncatalysed or the heparin-catalysed inactivation of thrombin. The recombinant antithrombin fraction with lower heparin affinity migrated more slowly than both the fraction with higher affinity and plasma antithrombin in SDS/PAGE under reducing conditions, consistent with a slightly higher apparent relative molecular mass. This apparent size difference was abolished by the enzymic removal of the carbohydrate side chains from the proteins. Such removal also increased the heparin affinity of the weakly binding fraction, so that it eluted from matrix-linked heparin at a similar position to the deglycosylated tightly binding fraction or plasma antithrombin. Analyses of N-linked carbohydrate side chains showed that the weakly binding fraction from CHO cells had a higher proportion of tetra-antennary and a lower proportion of biantennary oligosaccharides than the tightly binding fraction. We conclude that the recombinant antithrombin produced by the two cell lines is heterogeneously glycosylated and that the increased carbohydrate content of a large proportion of the molecules results in a substantial decrease in the affinity of these molecules for heparin. These findings are of particular relevance for studies aimed at characterizing the heparin-binding site of recombinant antithrombin by site-directed mutagenesis.
...
PMID:Decreased affinity of recombinant antithrombin for heparin due to increased glycosylation. 141 38

The administration of Interleukin-2 (IL-2) causes the release or generation of other cytokines such as tumour necrosis factor (TNF) which, by disturbing the anticoagulant properties of the endothelium, may induce a procoagulant state in patients receiving this drug. We therefore evaluated the effects of IL-2 on coagulation and fibrinolysis in 14 patients receiving 12 or 18 x 10(6) IU/m2/d of IL-2 given as a 15 min infusion for 5 d. Blood samples were drawn at short intervals after the first IL-2 infusion. The parameters were analysed by way of analysis for repeated measures (F tests rather than t tests). During the first day, thrombin-antithrombin (TAT) complexes started to increase 2 h after the IL-2 infusion, reaching peak levels at 4 h (n = 14; 11.2 +/- 6.4 micrograms/l v 49.8 +/- 49.2 micrograms/l, P < 0.01). Plasma alpha 2 antiplasmin (PAP) complexes showed a similar pattern rising from a mean baseline value of 17.5 +/- 7.6 nmol/l to 66.8 +/- 47.7 nmol at 4 h (P < 0.01). In four patients the peak of PAP preceeded that of TAT. Tissue plasminogen activator (tPA) rose from a mean baseline value of 4.9 +/- 3.7 micrograms/l to 26.3 +/- 13.5 micrograms/l at 4 h (P < 0.01). Plasminogen-activator-inhibitor-1 (PAI-1) levels increased from 59 +/- 35 micrograms/l to 113 +/- 39 micrograms/l at 6 h (P < 0.01). tPA PAI-1 complexes increased from 0.15 +/- 0.07 to 0.69 +/- 0.21 nmol/l at 6 h (P < 0.01). Our study indicates that IL-2 activates the coagulation and fibrinolytic systems in vivo. The changes resemble the perturbations observed after endotoxin/TNF administration. These abnormalities may play a role in the side-effects induced by IL-2 therapy.
...
PMID:Interleukin-2 induces activation of coagulation and fibrinolysis: resemblance to the changes seen during experimental endotoxaemia. 141 10

Isolated deficiencies of factors VII and XI are both rare. Not surprisingly, therefore, combined factor VII and XI deficiency has not been reported previously. We report here a kindred with a combined heterozygous deficiency for both factors VII and XI. The proposita is a 28-year-old woman who had both a prolonged prothrombin time (PT) and a prolonged activated partial prothrombin time (APTT) associated with a mild bleeding tendency. Coagulation studies were performed on the six available members of this kindred. The PT and APTT were normal or mildly abnormal in five of these individuals. Factor VII coagulant activity (VII:C) varied from 0.33 to 0.77 units/ml in affected subjects. In contrast, the concentration of factor VII-related antigen for the six individuals ranged from 0.68 to 2.10 units/ml. Comparable factor VII:C levels were obtained when each subject's plasma was tested with either a rabbit or a human thromboplastin reagent. Factor XI coagulant activity was less than 0.5 units/ml in three of the six subjects and normal (approximately 1.0 units/ml) in the other three. The concentrations of thrombin-antithrombin-III and prothrombin fragment 1.2 were within normal limits for all individuals. In addition to being associated with heterozygous factor XI deficiency, the abnormal factor VII molecule in the plasma of affected individuals in this kindred appears to represent a newly described mutation. This is suggested by the pattern of reactivity with thromboplastin from different species, the normal tissue factor binding and the bleeding tendency in heterozygous individuals in this kindred.
...
PMID:A novel congenital haemostatic defect: combined factor VII and factor XI deficiency. 148 4

Nearly all patients with cancer manifest laboratory evidence of hypercoagulability and some develop clinical thromboembolic disease (TED). Routine laboratory studies of blood coagulation have been performed in several large, prospective trials of the use of anticoagulant drugs in cancer treatment. The results of these studies, as well as data from several smaller studies of more sensitive tests of hypercoagulability [e.g. fibrinopeptide A (FPA); thrombin-antithrombin (TAT) complexes; prothrombin fragment F1 + 2)], indicate that the levels of some clotting proteins parallel disease activity. However, no studies of sound methodologic design have yet been performed to indicate that any of these tests of blood coagulation can serve as adequate predictors of TED in patients with cancer. In addition to the important role played by tumor-related procoagulants, several other mechanisms may be involved in the pathogenesis of thromboembolic events in patients with cancer, including stasis and endothelial damage. Considerable variability in the relative importance of these mechanisms in the pathogenesis of TED may exist among patients with different types of cancer. The risk for TED associated with surgical procedures in cancer patients is substantial and prophylactic antithrombotic therapy should be considered for most of these patients. Chemotherapy and hormonal therapy of cancer probably increases the likelihood of TED, particularly in those subjects with indwelling venous catheters. This risk has been particularly well-studied in patients with breast cancer treated with tamoxifen plus cytotoxic drugs. The pathogenic mechanisms may be complex but vascular injury is likely as a proximate cause of venous access catheter thrombosis and can be prevented with low dose coumadin therapy. The utility of low dose coumadin anticoagulation in reducing the risk for TED during breast cancer treatment is unknown but is currently being tested in a large, multiinstitutional study. Since chronic coumadin anticoagulation of cancer patients, and single pulse dose heparin prior to intravenous chemotherapy, both prevent thrombin generation, these agents may be of use in reducing the risk of chemotherapy-associated thrombosis. Prophylactic anticoagulation should be considered for high risk patients.
...
PMID:Hemostatic alterations in cancer patients. 142 16

Since the expression of genes for platelet-derived growth factor (PDGF)-A and PDGF beta-receptor are reciprocally regulated in vascular wall cells after balloon injury, we have investigated the ability of specific vasoactive molecules or growth factors to reproduce the injury pattern of gene expression in cultured rat smooth muscle cells (SMCs) and assessed the effect of inactivating alpha-thrombin on injury-induced expression of PDGF-A mRNA by vascular wall cells in vivo. The molecules investigated, to which vascular SMCs may be locally exposed after mechanical injury, included vasoactive factors (alpha- and beta-adrenergic agonists, serotonin, histamine, angiotensin II, and endothelin) and growth factors (PDGF-AA, PDGF-BB, basic fibroblast growth factor, insulin-like growth factor, epidermal growth factor, and alpha-thrombin). In cultured rat SMCs, only alpha-thrombin (0.1-100 nM), among these compounds, produced the pattern of transiently increased PDGF-A and decreased PDGF beta-receptor mRNA. PDGF-B chain mRNA levels remained undetectable in these cultured SMCs. The dependence of these changes in gene expression on the proteolytic activity of alpha-thrombin was shown by the interruption of altered gene expression or DNA synthesis after incubating the cultured SMCs with covalently inactivated alpha-thrombin using D-Phe-Pro-Arg chloromethyl ketone, a synthetic direct active-site irreversible inhibitor of alpha-thrombin. Continuous intravenous infusion of this synthetic antithrombin into baboons for 6 hours (100 nmol/kg per minute maintaining constant plasma levels of 3.0 +/- 0.5 microns/ml) after inducing balloon-catheter arterial injury also prevented the threefold increase in expression of PDGF-A mRNA characteristically exhibited by untreated mechanically injured vessels.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Regulation of platelet-derived growth factor ligand and receptor gene expression by alpha-thrombin in vascular smooth muscle cells. 142 27

Recombinant hirudin variants have been designed which inhibit alpha-thrombin by the hirudin mechanism and which in addition exhibit disintegrin activity. These proteins, called "hirudisins," have been engineered by replacing the Ser-Asp-Gly-Glu sequence at the tip of hirudin's finger-like structure (residues 32-35) by Arg-Gly-Asp-Ser (RGDS) to yield hirudisin and Lys-Gly-Asp-Ser (KGDS) to obtain hirudisin-1. Comparison of thrombin inhibition activities showed that hirudisin is 2-fold more potent (K(i) = 160 +/- 70 fM) than hirudisin-1 (K(i) = 370 +/- 44 fM) and recombinant (r)-hirudin (K(i) = 270 +/- 50 fM). alpha-Thrombin-stimulated platelet aggregation was effectively inhibited by r-hirudin, hirudisin, and hirudisin-1 with IC50 of 5.7 to 6.8 nM. Unlike r-hirudin, hirudisin inhibits ADP-induced platelet aggregation (IC50 = 65 microM) 3- to 5-fold stronger than the linear GRGDS- and RGDS-peptide. Direct interaction of hirudisin with purified glycoprotein IIb-IIIa demonstrated that antiplatelet aggregation activity is due to the integrin-directed RGD motif. Disintegrin activity of hirudisin relative to that of reduced and carboxymethylated hirudisin suggests that the conformational strain favors binding to integrins. On the basis of these results, hirudisins appear to be interesting molecules for the design of potential antithrombotic agents with antithrombin as well as antiplatelet aggregation activities.
...
PMID:Hirudisins. Hirudin-derived thrombin inhibitors with disintegrin activity. 144 73

The objective of the study was to investigate the acute effect of a single very high dose of n-3 PUFA on coagulation and fibrinolysis. Forty healthy volunteers were randomized into two groups to receive either 20 grams of n-3 PUFA or 20 grams of n-6 PUFA as a single dose at 6 p.m. with their evening meal. Coagulation and fibrinolysis were evaluated in the fasting state at 8 a.m. the next morning and compared to values obtained at 8 a.m. the day before, when the participants were on their habitual diets. PAI-1 activity in plasma increased by a mean of 62% in subjects randomized to receive n-3 PUFA despite that no changes could be demonstrated in t-PA antigen levels. PAI-1 activity was unaltered in the 20 controls receiving n-6 PUFA. Plasma fibrinogen, coagulation factor VII, thrombin-antithrombin complexes and D-dimer did not significantly change after either supplement. The substantial increase in levels of PAI-1 activity in plasma after a single very high dose of n-3 PUFA may limit the usefulness of single very high doses of n-3 PUFA in acute clinical conditions.
...
PMID:The acute effect of a single very high dose of N-3 fatty acids on coagulation and fibrinolysis. 144 89

Patients suffering from atherosclerosis may have a hypercoagulable state which is further aggravated by surgery. Thrombin, a central enzyme in the coagulation process, cleaves fibrinogen to fibrin. Therefore, inhibition of thrombin is an important anticoagulant mechanism. This is accomplished by heparin in concert with antithrombin III (AT), but vessel wall glycosaminoglycans may act as substitutes for heparin and catalyse thrombin inhibition. The present study examines whether administration of AT or heparin is effective as an anticoagulant during infrainguinal bypass surgery. Preoperatively and during surgery the patients had elevated levels of fibrinogen, fibrinopeptide A (FPA) and thrombin-antithrombin (T-AT) complexes. There were higher levels of FPA in the venous outflow from the ischemic leg than in the arterial inflow. Taken together these measurements indicate ongoing coagulation in the operated leg. Administration of heparin decreased FPA levels and prevented intraoperative graft thrombosis, whereas in patients receiving AT, T-AT levels increased but FPA levels were unchanged. In the latter group, intraoperative graft thrombosis occurred in a high proportion. Based on additional case histories in these patients with hypercoagulability, it is suggested that fibrinogen is a risk factor for thromboembolic complications and that a combination of low dose of heparin and AT might be an effective regimen to prevent intraoperative thrombosis with a low risk of haemorrhage.
...
PMID:Peroperative anticoagulation with antithrombin or heparin in infrainguinal bypass surgery. 145 16


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---