摘要:

Fibrinogen is a complex multifunctional protein comprised of three major domains (two outer D and one central E) which contains constitutive binding sites (e.g. Da, Db, γXL, D:D, γ', thrombin substrate, platelet receptor) as well as binding sites that become exposed or expressed as a result of fibrinogen proteolysis by thrombin and/or that are exposed as a consequence of the polymerization process itself (tPA binding sites). Fibrin-dependent tPA-mediated activation of plasminogen is associated with exposure of polymerization-dependent epitopes (Aα148–160, γ312–324) that are expressed in assembled fibrin and in crosslinked (polymerized) fibrinogen but not in unpolymerized fibrinogen or fibrin. Fibrin polymerization is initiated by thrombin cleavage of fibrinopeptide A from fibrinogen Aα chains, exposing two E domain EAsites. Cleavage of fibrinopeptide B from fibrinogen Bβ chains exposes other E domain polymerization sites, termed EB, that also interact with platelets, fibroblasts and endothelial cells. Fibrin generation is followed by an assembly process of intermolecular end-to-middle D to E associations to form linear and branched double-stranded fibrin fibrils, lateral fibril-fibril associations to form fibers and a branched fiber network. Binding sites in fibrinogen play their roles in fibrin assembly by self-association (γXL to γXL and D:D to D:D) or by complementary association with exposed sites in fibrin (Da to EAand Db to EB). Other binding sites in fibrinogen include thrombin substrate recognition sites in each E domain and a non-substrate high affinity thrombin binding site in the carboxy-terminal region of each γ' chain, which also binds plasma factor XIII. Fibrin possesses low affinity thrombin binding sites in each E domain and retains the γ' chain non-substrate thrombin-binding site.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

We compared the performance characteristics of a commercial dilute Russell's viper venom (DRW)-based APC resistance assay (Gradipore PC Impedance Test) to a routinely utilized commercial APTT based assay (Coatest APC Resistance Assay). The DRVV based assay offers improved sensitivity and specificity for the factor V Leiden mutation. However, the routine use of both assays provides optimum reliability for diagnosis of genetic APC resistance. Our results suggest that when both tests are either positive or negative, DNA analysis is unnecessary. Interference by lupus anticoagulants is dramatically minimized by the phospholipid rich DRW reagent used in the assay and it is insensitive to high factor VIII activity. Additionally, discrepant functional assay results allow identification of patients who may have an acquired APC resistant phenotype.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

We evaluated the antithrombotic effects of recombinant human soluble thrombomodulin (rhsTM) in plasma and in a monkey model. rhsTM dose-dependently prolonged activated partial thromboplastin time (APTT) in the following order: humans > monkeys > rats ≫ rabbits. The prolongation of APTT by rhsTM was also observed in protein C-deficient plasma. rhsTM activated protein C and inactivated factor Va in human and monkey plasma, but not in rat plasma. These findings suggest that the antithrombotic activities of rhsTM are fully expressed in human and monkey. Therefore, to evaluate the whole activity of rhsTM in a clinical model, tissue factor (TF) was intravenously infused into crab-eating monkeys to induce disseminated intravascular coagulation (DIC). Pretreatment with rhsTM reduced fall in fibrinogen with a biphasic and moderate dose-dependency curve, and reduced thrombin-antithrombin III (TAT) levels with a flat linear dose-dependency, while heparin prevented fall in fibrinogen with a steep linear dose-dependency curve without reducing TAT levels. Further evidence suggesting that rhsTM activates protein Cin vivowas also obtained. Taken together, the data indicate that rhsTM fully expresses its antithrombotic activities in human and monkey but not in rat and rabbit, and rhsTM prevents TF-induced DIC in monkeys by suppressing thrombin generation.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Recently, the HPA-1b (PlA2) polymorphism of the platelet glycoprotein IIIa has been suggested as a genetic risk factor for coronary artery disease. We conducted two case-control studies of 103 patients with ischaemic cerebrovascular disease (CVD) and 101 patients with ischaemic heart disease (IHD). The groups were matched for age, race and sex. No significant differences regarding selected risk factors (hypertension, diabetes mellitus, hypercholesterolaemia and smoking) were found between case patients and controls. Moreover, we investigated 286 normal individuals from the Mediterranean area. Genotyping of HPA-1 was performed by PCR-allelic specific restriction and single-strand conformation polymorphism analysis. The prevalence of HPA-lb was similar among case patients and controls (29.2% vs. 25.3% and 26.7% vs. 34.6% for CVD and IHD case-control studies, respectively). The HPA-1b allele was found in 36.4% of the normal population. Finally, the analysis of platelet function in nine controls with the three possible HPA-1 genotypes (three a/a, three a/b and three b/b) indicates that HPA-1b genotype does not modify either thein vitroplatelet aggregation and activation profile, nor the GP IIb/IIIa interaction with fibrinogen or von Willebrand factor. Our results do not support the role of HPA-lb polymorphism as an inherited risk factor for arterial thrombotic disease.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The blood-sucking leech,Haementeria ghilianii, has evolved a number of agents that attenuate haemostasis. Recently we have isolated a potent inhibitor of factor XIIIa, tridegin, in the salivary glands which is almost certainly involved in feeding. Addition of purified natural tridegin to plasma, prior to clotting with thrombin, results in clots that deform more readily as adjudged by the greatly reduced development of the storage modulus on application of a shear force. The increase in the storage modulus in developing plasma clots is a slow process and continues for many hours. The effect of tridegin is particularly great when the clots are permitted to age in this way, demonstrating the role of factor XIIIa in the process. The IC50for this inhibition is 138 ng/ml. Clots formed in the presence of tridegin are also lysed more rapidlyin vitroby the leech's own fibrinolytic enzyme, hementin (time for 50% lysis, 16.0 ± 0.8 h versus 22.3 ± 2.0 h,P< 0.05). The synergy with which these agents act together may provide lessons for therapy of thrombosis in man.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Eighty-seven outpatients consecutively admitted to the emergency unit of our hospital with clinically suspected first deep vein thrombosis (DVT) of a leg had D-dimer levels measured by the following recently introduced fast methods: VIDAS (bioMerieux), LPIA (Mitsubishi), Nephelotex (Biopool), Nycocard (Nycomed) and Instant I.A. (Diagnostica Stago). A latex agglutination test (Minutex, Biopool) was also performed and a classical ELISA (Gold EIA, Agen) used as reference. Venography was performed in all patients, with DVT diagnosed in 42 (37 proximal). All the new methods can be adopted in emergency situations, since they are suited for individual tests, are rapid and the reagents ready to use. All the methods proved to have a good interassay reproducibility. The new D-dimer and latex agglutination tests showed negative (88–96%) and positive (63–81%) predictive values similar to those of ELISA (92% and 71%, respectively), though the still wide confidence intervals suggest larger patient population series be investigated. As regards clinical application, the use of these tests to rule out DVT should be tested in prospective clinical follow-up trials where anticoagulation is withheld in subjects with negative non-invasive reliable vascular tests and normal D-dimer levels.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

We measured the plasma levels of fibrinogen, D-dimer, thrombin-antithrombin complex (TAT), plasmin-plasmin inhibitor complex (PPIC), soluble fibrin monomer (SFM), tissue-type plasminogen activator (t-PA) and thrombomodulin (TM) in patients with non-insulin-dependent diabetes mellitus (NIDDM). There were no significant differences in the hemostatic parameters between the 77 patients with NIDDM and healthy control subjects, although the plasma levels of fibrinogen, D-dimer, TAT, and PPIC in the NIDDM patients were slightly higher than those in the healthy controls. Among the NIDDM patients divided into three groups by the urinary albumin excretion (UAE) level, there was no significant difference in age or sex among the normo-, micro-, and macroalbuminuria groups, and the HbAlC level in the micro-and macroalbuminuria groups were slightly higher than those in the normoalbuminuria group. There was no significant difference in activated partial thromboplastin time, prothrombin time, fibrinogen, TAT, PPIC, D-dimer, or t-PA among these three groups. The plasma SFM and TM levels in the macroalbuminuria group were significantly higher than those in the normo-and microalbuminuria groups. The relationships between HbAlC and the hemostatic parameters were poor, but the plasma TM and SFM levels were significantly correlated with the urine albumin index.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

We report a novel mutation within the coagulation factor VII gene associated with a dysfunctional procoagulant factor VII (12% of normal plasma factor VII activity; 50% of normal plasma factor VII antigen level). Using heteroduplex analysis and subsequent sequencing, we identified a thymine-10,902 to cytosine mutation within exon eight of the factor VII gene, encoding for a substitution of arginine for cysteine-329 (factor VII C329R) within the heavy chain of factor VII. This substitution disrupts a disulfide bond within the factor VII catalytic domain and might cause altered conformation of the active site triad.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Pseudo (or platelet-type)-von Willebrand disease (vWD) is a very rare autosomal dominant bleeding disorder caused by an abnormal hyper-responsiveness of the platelet membrane glycoprotein (GP) Ib/IX complex, the receptor for von Willebrand factor. We found a heterozygous missense mutation in the GPIbα gene in a sporadic case with pseudo-vWD: Met (ATG) to Val (GTG) at residue 239. The mutation was not detected in either parent. Investigation of three variable number of tandem repeat loci, D1S80 (MCT118), vWA and D17S5 (YNZ22), confirmed paternity and thede novoorigin of the mutation. Furthermore, we have shown by theTaqI polymorphism analysis, which is located downstream of the GPIbα gene, that the mutation occurred in the maternal allele. This is the first description ofde novomutation occurred in pseudo-vWD and/or platelet GPIbα gene.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

We describe the first reported case of a thrombophilia patient genetically homozygous for a recently described polymorphism in the 3'-UTR (untranslated region) of the prothrombin gene. It has previously been demonstrated that this genetic variant due to a G to A transition at nucleotide 20210 is common and associated with an almost threefold increased risk of venous thrombosis. This polymorphism was also shown to be associated with elevated plasma prothrombin (factor II) levels, which in itself was found to be a risk factor for venous thrombosis. The patient was a healthy young Mexican male who presented with a myocardial infarction and subsequent ileofemoral venous thrombosis and massive saddle pulmonary embolus. Testing done during his initial hospitalization suggested a congenital protein C deficiency. The patient was found to be homozygous for the prothrombin gene polymorphism as well as a carrier for factor V Leiden. This case strongly implies a clinically significant role for the factor II gene mutation in both arterial and venous thrombosis and demonstrates the need to perform diagnostic clotting based assays after resolution of acute thrombotic events. These findings further support the 'double hit' theory for thrombophilia in young patients.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID