摘要:

Since thrombin plays an important role in platelet-mediated arterial thrombosis, we have examined the antiplatelet activity of a synthetic thrombin inhibitor, DuP 714 (Ac-(D)Phe-Pro-boroArg), in comparison with that of the naturally occurring inhibitor hirudin. Hirudin was slightly more potent than DuP 714 in inhibiting thrombin-induced aggregation in washed human platelets (IC50s of 72 nM and 150 nM, respectively) and in inhibiting the secretion of plasminogen activator inhibitor-I from human platelets (IC50s of 300 nM and 900 nM, respectively). In contrast, DuP 714 was more potent than hirudin in inhibiting thrombin-induced [125I]fibrinogen binding to gel purified platelets, and in inhibiting thrombin-induced intracellular calcium mobilization in washed platelets. These results indicate that the tripeptide DuP 714 has comparable antiplatelet activity to the 65 amino acid hirudin. We conclude that DuP 714 may have clinical utility in the prevention of platelet-dependent, arterial thrombotic processes.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

We describe a 50-year-old man with a severe acquired haemorrhagic syndrome. He had slightly prolonged clotting times using bovine thrombin, human thrombin and reptilase. His plasma contained a polyclonal IgG which interfered with the generation of fibrin monomers without inhibiting the aggregation of preformed monomers. The inhibitor delayed thrombin-induced fibrinopeptide A release. The IgG bound to insolubilized synthetic fibrinopeptide A (one binding site per molecule) and, with higher affinity, to fibrinogen (two binding sites per molecule). It did not bind to insolubilized fibrin monomers. The IgG did not impair the catalytic activity of thrombin toward a small synthetic substrate but inhibited the binding of thrombin to fibrinogen without binding to thrombin. The binding of the anti-fibrinopeptide A autoantibody to fibrinogen might have impaired thrombin-induced fibrinogen to fibrin conversionin vivo.This may have favoured the reported haemorrhagic syndrome which was associated with severe chronic renal insufficiency.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Previous studies have shown that washed human platelets attenuate oxidant oedema in isolated perfused rabbit lungs through mechanisms dependent on platelet glutathione. We hypothesized that the platelet glutathione redox cycle scavenges hydrogen peroxide in this model and thereby protects vascular endothelial cells from oxidant injury. This hypothesis was tested by asking two questions: (1) do glutathione-supplemented platelets demonstrate augmented lung protection compared with control platelets, and (2) does conjugation of platelet glutathione with 1-chloro-2,4-dinitrobenzene or inactivation of catalase with 3-amino-1,2,4-triazole decreasein vitroplatelet metabolism of hydrogen peroxide? We incubated washed human platelets with reduced glutathione or glutathione monoester and observed platelet glutathione contents of 181% and 189%, respectively, compared with control values. Incubation of platelets withN-acetylcysteine did not alter platelet glutathione content. Infusion of glutathione-supplemented platelets into isolated lungs injured by purine and xanthine oxidase did not augment platelet protection compared with untreated platelets. We also found that conjugation of platelet glutathione and/or inactivation of platelet catalase did not decrease the rate constant for platelet metabolism of hydrogen peroxide. We conclude that platelets attenuate oxidant lung oedema through glutathione-dependent mechanisms other than direct scavenging of hydrogen peroxide.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Ocular vascular occlusive disease resulting in severe retinopathy and/or post-thrombotic glaucoma has been extensively discussed in patients with lupus anticoagulant and/or anticardiolipin antibodies (LA/aCL). Inadequate circulation plays an important role in the pathogenesis of another ophthalmic entity—the normal tension glaucoma. We studied 22 patients with normal tension glaucoma (group I) and 23 with chronic open-angle glaucoma (group II) and compared them with a control group (n= 25, group III). LA, aCL, the aCL cofactor β2-Glycoprotein I, and other haemostatic parameters including factor VIII:C, von Willebrand factor, factors II, V, VII and plasminogen activator inhibitor were measured. Five out of 22 (22.7%) in group I, five out of 23 (21.7%) in group II and three out of 25 (12.0%) in group III had positive LA and/or aCL. These prevalences were not statistically significantly different. β2-Glycoprotein I was normal in all groups. No other parameters were significantly different between groups. These findings do not support the contribution of ocular microvascular occlusive disease, due to elevated aCL, in the pathogenesis of glaucomatous damage.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Data in the literature on the prevalence of hereditary deficiency of the natural coagulation inhibitors are conflicting. We conducted a prospective study on 680 consecutive patients with a history of venous thrombosis to determine the prevalence of hereditary deficiency of antithrombin III (AT III), protein C (PC) and protein S (PS) and to establish selection criteria for rational patient screening. The mean age of the patients at investigation was 44.3 ± 15.4 years, while that at the first thrombotic event was 38.5 ± 14.8 years. The total prevalence of inhibitor deficiency states was 48/680 (7.1%). 19/680 patients (2.8%) had AT III-deficiency, 17 (2.5%) PC-deficiency, nine (1.3%) PS-deficiency and three (0.4%) a combined deficiency. In 37/48 deficient patients family studies were performed and the hereditary nature was established in 19 cases (2.8% of total patient population, six with AT III-deficiency, eight with PC-deficiency, four with PS-deficiency and one with a combined deficiency). Family studies in these 19 patients revealed 46 additional individual patients with a hereditary deficiency state. A positive family history was found in 15/19 (79%) with a proven hereditary deficiency state, in 153/619 (25%) of non-deficient patients and in 11/29 (38%) of deficient patients without established hereditary nature. The mean age at the first thrombotic event was significantly lower in patients with a hereditary deficiency state (26.8 years) compared with the other two groups (39.0 and 39.7 years, respectively). In all patients with a hereditary deficiency the first thrombotic event occurred before the age of 45 years. The site of thrombosis and the frequency of spontaneous and recurrent thromboembolic events was similar in patients with and without a deficiency state. We conclude that the prevalence of the hereditary deficiency of AT III, PC or PS in patients with a history of venous thrombosis or pulmonary embolism is low. A positive family history and the occurrence of the first thrombotic event at an early age are of predictive value for the presence of a hereditary deficiency state. These criteria are useful for selecting patients for determination of AT III, PC and PS.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Individuals with severe factor XII (FXII) deficiency may be prone to thromboembolic disease and this thrombophilic state may be due to insufficient contact activation dependent fibrinolysis. According to our previous study (Thromb Haemostas1991;65:117–121), however, heterozygous FXII deficiency is not a strong prethrombotic risk factor, only one out of 45 obligatory or possible heterozygotes having sustained a thrombotic event. In the present study, FXII clotting activity (FXII:C) and antigen concentration (FXILAG) were measured in 200 patients having suffered from idiopathic thromboembolism and compared with the values in 200 healthy controls. Mean FXII levels were not significantly different in thrombophilic patients and controls, and subnormal FXII values were not more frequently encountered in patients than in controls. Specific FXII activity, i.e. the ratio of FXII:C to FXII:AG, showed considerable variation in each of the two groups, but patients and controls had a similar distribution of specific FXII activity. Variations in specific FXII activity were not explained by differences in ß2-glycoprotein I levels. In conclusion, heterozygous FXII deficiency is not a strong prethrombotic risk factor and subnormal FXII values are not more common in thrombophilic patients than in healthy individuals.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Factor X, a vitamin K-dependent protein, is the plasma zymogen for the active serine protease factor Xa. Factor Xa is the proteolytic enzyme for prothrombinase, the multi-protein membrane complex that catalyses the cleavage of prothrombin to thrombin. A panel of 10 monoclonal antibodies (identified by their corresponding clone numbers: 1,2,3,5,7,26,27,54,73, and 79) to factor X were produced by immunizing mice with purified factor X. All of the antibodies bound both human factor X and factor Xa in a solid-phase ELISA and binding of the antibodies was not affected by removal of Ca2+with EDTA. In immunoblot analysis, antibody αHFX-54 bound to the light chain and antibodies αHFX-1, −5, −7, and −26 bound to the heavy chain of reduced factor X. Antibodies αBFX-2b, αHFX-27, −54, and −73 prolonged both the factor X-dependent clotting time and activated partial thromboplastin time (APTT) of normal plasma while antibody αHFX-1 only prolonged the APTT. None of the antibodies significantly inhibited factor X activation by purified Russell's viper venom factor X activator. In prothrombin activation assays using purified factor Xa, factor Va, prothrombin, Ca2+and phospholipid vesicles, seven of the antibodies (αHFX-1, −3, −26, −27, −54, −73 and αBFX2b) showed some inhibition of thrombin generation ranging from 18 to 60% of the control. The decrease in factor X plasma clotting activity was most likely due to inhibition of factor Xa activity in prothrombinase, although some antibody-dependent inhibition of factor X activation may contribute to the observed inhibition of plasma clotting. Prothrombinase activity on platelets was inhibited in an identical manner by the monoclonal antibodies. When prothrombin was activated in the absence of factor Va, only antibody αBFX-2b inhibited activation. Calcium-independent determinants on both the heavy chain (determinants 1 and 26) and light chain (determinant 54) of factor X may play a role in prothrombin activation by prothrombinase. Other epitopes (antibodies αHFX-3, −27, −73) appeared to be influenced by association of factor Xa with factor Va. Topographic regions on factor X important for factor X activation and factor Xa function may be identified by the use of these monoclonal antibodies.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Pharmacological modulation of thein vivoinduction of plasminogen activator inhibitor type-1 (PAI-1) synthesis was studied in rats using the induction of PAI-1 by endotoxin as a model system. Both the cyclooxygenase inhibitors acetylsalicylic acid and indomethacin enhanced PAI-1 induction. The combined cyclooxygenase-lipoxygenase inhibitor, BW755C, dose-dependently inhibited induction. Since five other lipoxygenase inhibitors, a phospholipase inhibitor, an inhibitor of leukotriene formation and dexamethasone had no effect on the endotoxin-induced increase in PAI-1 synthesis, the effect of BW755C could not be ascribed to its known pharmacological properties. In addition, induction of PAI was enhanced by isobutyl-methylxanthine, a phosphodiesterase inhibitor, but not, however, by other phosphodiesterase inhibitors, or by forskolin or NG-nitro-L-arginine, suggesting an effect of isobutyl-methylxanthine other than through cyclic nucleotides. Heparin and hirudin had no effect either. Overall, the data showed that the induction of PAI-1 synthesis by endotoxinin vivocan be up- and down-regulated pharmacologically, but the mechanisms involved remain elusive.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Plasma levels of von Willebrand factor (vWf) are frequently elevated in patients with disseminated intravascular coagulation (DIC). To investigate the qualitative abnormalities of vWf and the possibility of itsex vivomodification in DIC, we analysed the multimeric composition of vWf in citrated plasma from 15 patients with DIC in the presence or absence of serine protease inhibitors (aprotinin and soybean trypsin inhibitor) and/or cysteine protease inhibitors (leupeptin,N-ethylmaleimide and EDTA). The proportion of large v wf multimers in plasma prepared in the presence of cysteine protease inhibitors was higher than those without such inhibitors. The addition of serine protease inhibitors during the preparation of plasma had no effect on the relative amounts of large multimers. The relative proportion of large multimers in plasma prepared without inhibitors and the difference between plasmas prepared with and without cysteine protease inhibitors correlated with plasma plasmin-α2-plasmin inhibitor complex values, but not with other plasma or serum markers of DIC (platelet count, nbrinogen, FDP, D-dimer or thrombin-antithrombin III complex). We conclude thatex vivoproteolysis of plasma v wf occurs frequently in patients with DIC and cysteine protease inhibitors can protect this degradation.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Plasma from women taking combined oral contraceptives and cold-activated plasma contain proteases which cleave chromogenic substrates in protein C assays in the absence of protein C activators such as ProtacTM. This spontaneous activity makes a background subtraction necessary and makes protein C (PC) assays less accurate. We investigated two commonly used substrates < Glu-Pro-Arg-pNA (S-2366) and 2AcOH.H-D-Lys(Cbo)-Pro-Arg-pNA (PC substrate) and found that cold-activated normal and protein C-deficient plasmas gave absorbance values up to 300 times higher than buffer blanks. FXIa cleaves these substrates but activity was not blocked by corn or lima bean trypsin inhibitors, soy bean trypsin inhibitor (SBTI), hirudin or ±-amino-n-caproic acid (EACA). Kaolin activation of normal, FXI, FIX, FVIII, FVII and protein C-deficient, but not of FXII or prekallikrein (PKK)-deficient plasmas led to cleavage of chromogenic substrate for protein C. The protein C substrates were cleaved by purified kallikrein and α- and ß-FXIIa. Immunoabsorption with α2-macroglobulin (α2M) antibodies removed 60% of the α2M and 70% of the activity on PC Substrate. Gel filtration of normal plasma on Sephadex G-150 gave a single peak of protein C activity and antigen in the included volume. After cold activation of the fractions, a second protein C-like peak appeared in the void volume, but with no detectable protein C antigen. This peak coincided with α2M (chromogenic and ELISA) and plasma kallikrein (S-2302), but FXII (measured with a substrate insensitive to kallikrein) eluted separately. Gel filtration of a cold activated plasma gave a similar peak of spontaneous activity on PC Substrate, which was not inhibited by SBTI. We suggest that the protein C substrates may be cleaved by kallikrein and other enzymes complexed to α2M, which retain activity on small substrates. Samples exceptionally susceptible to cold activation should be collected into anticoagulant containing kallikrein inhibitors and methylamine.

ISSN:0957-5235    

出版商:OVID    

年代:1992

数据来源: OVID