摘要:

&NA;Irreversible initial non‐function of the graft liver is a life‐threatening early complication of orthotopic liver transplantation (OLT), which needs immediate retransplantation if the patient is to survive. Since protein C (PC) is a vitamin K dependent protein synthesized in the liver and with the same half‐life as factor VII (FVII), the behaviour of PC in patients undergoing OLT was studied in comparison with prothrombin time (PT) and FVII. Twelve OLT patients were divided into two groups on the basis of clinical outcome: group A (six cases) in which OLT was successful, and group B (six cases) who developed initial non‐function of the graft liver. PT, FVII activity (FVII:act) and antigen (FVII:Ag) and PC activity (PC:act) and antigen (PC:Ag) were carried out on six blood samples collected during the operation. At baseline, coagulation disorders were in agreement with the underlying liver disease, but no differences were seen between the two groups when all tests were considered. Ten minutes, 1, 2 and 3h after liver graft reperfusion, mean PT and FVII:act were always significantly increased in good responder patients compared to non‐responders. FVII:Ag and PC:Ag were significantly higher in group A than in group B starting 2 h after the liver graft reperfusion; no difference was seen in PC:act levels between the two groups. In addition, PC:Ag mean levels were increased with respect to corresponding PC:act values in non‐responder patients, suggesting a qualitative rather than quantitative defect of protein synthesis due toliver damage. In conclusion, PT and FVII:act were more sensitive than PC activity as early prognostic indices of clinical out come in OLT.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;The basal lysis rates ofex‐vivoprepared blood clots from rats, mice, hamsters, dogs, and humans and levels of &agr;2‐antiplasmin (&agr;2‐AP) cross‐linked to fibrin have been studied in the presence and absence of factor XIII (FXIII) inhibitors using a blood clot lysis assay and an &agr;2‐AP binding assay. Clots prepared from rat or human blood lysed spontaneously within 3‐5h. Clots from hamster blood lysed completely within 30 min but clots prepared from murine or canine blood lysed only after addition of 1.0 IU human t‐PA. To study the effect of activated FXIII (FXIII) inhibition on blood clot lysis the FXIII inhibitors L722151 and mono‐dansylcadaverine (dansyl) were used. In the presence of the FXIII inhibitors human, murine, and canine blood clots showed increased lysis rates. The lysis rate of rat blood clots was not affected. Effects on hamster blood clots could not be detected because of the high basal lysis rate. In clots prepared from human, murine, or canine plasma about 20% of the plasma &agr;2‐AP concentration was cross‐linked to fibrin. FXIII inhibitors inhibited crosslinking by more than 80%. No significant cross‐linking of &agr;2‐AP could be detected in rat and hamster plasma clots. When 0.1 volume of human plasma was added to 0.9 volume of rat plasma the level of &agr;2‐AP cross‐linking was equal to that in human plasma indicating that rat &agr;2‐AP can be cross‐linked to human fibrin. The same effect was obtained with human FXIII deficient plasma but not with human fibrinogen deficient plasma. These experiments indicate that rat fibrinogen is not a substrate for the cross‐linking of rat &agr;2‐AP catalysed by rat FXIII, Addition of human plasma to hamster plasma did not result in an increased level of &agr;2‐AP cross‐linking which indicates that other factors are involved.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;One hundred consecutive patients with acute upper gastrointestinal bleeding were investigated. Blood coagulation and fibrinolytic activity were monitored by levels of plasma thrombin‐antithrombin III(TAT) complex and plasmin‐&agr;2‐antiplasmin (PAP) complex in samples obtained from patients at admission with haematemesis and/or melaena and in samples obtained from patients the first day after admission. Blood was transfused according to a restrictive policy. Median plasma TAT complex was significantly elevated both at admission and on the first day after admission compared with a reference group. Plasma PAP complex levels were normal at admission but decreased on the first day after admission. This decrease was independent of blood transfusion. The results indicate hypercoagulability at admission among patients with upper gastrointestinal haemorrhage reinforced by the development of a hypofibrinolytic state during the first day after admission. Restricted blood transfusion was not associated with any detectable change in blood coagulation or fibrinolysis in these patients.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;Fibrin forms on and binds to the extracellular matrix of endotoxin‐stimulated endothelium when exposed to flowing non‐anticoagulated blood. These processes have been investigated by employing a humanex vivoperfusion model, a synthetic peptide Arg‐Gly‐Asp‐Val and a monoclonal anti‐tissue factor antibody which inhibits tissue factor/FVIIa‐induced coagulation. Procoagulant extracellular matrix on plastic cover‐slips was prepared from cultures of endotoxin‐stimulated human endothelium following brief exposure to 0.1 M NH4OH. Non‐anticoagulated blood was drawn directly from an antecubital vein by a pump at venous (100/s) and arterial (650/s) wall shear rates over the matrix‐coated cover‐slips positioned in parallel‐plate perfusion chambers. Deposition of fibrin and platelets on the matrix was quantified by morphometry. Preincubation of the matrix with Arg‐Gly‐Asp‐Val inhibited fibrin deposition by 80‐90% at both venous (P< 0.001) and arterial shear (P< 0.05). However, the peptide had no effect on the clotting time in a modified one‐stage clotting assay where coagulation was initiated by lysed endotoxin‐stimulated endothelial cells, indicating that the peptide interfered with the binding of fibrin to the matrix in the perfusion model. Preincubation of the matrix with the anti‐tissue factor antibody, which blocked the coagulant activity (> 95%,P<0.01) in the modified coagulation assay, also inhibited fibrin deposition on the matrix by 90‐95% (P<0.01) at both shear rates. In the absence of either inhibitor, platelets adhered preferentially to the fibrin meshwork, and more so at arterial shear. Plateelet thrombus formation on the fibrin coat was in particular pronounced at arterial shear. Thus, it appears that the extracellular matrix of endotoxin‐stimulated endothelium initiates coagulation predominantly through tissue factor/FVIIa and that the resulting fibrin meshwork forming on the surface induces rapid platelet thrombus formation. The inhibitory effect of Arg‐Gly‐Asp‐Val on the binding of fibrin to the matrix may indicate the presence of specific matrix fibrinogen/fibrin binding site(s) with a recognition sequence of Arg‐Gly‐Asp.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;Fibrinogen (Fg), plasminogen (Plg), alph &agr;2‐antiplasmin (&agr;2‐AP), plasminogen activator (PA), tissue plasminogen activator (tPA), plasminogen activator inhibitor (PAI), D‐dimer (DD) and fibrin(ogen) degradation products (FDP) were studied in 60 subjects: 40 patients with endemic hepatosplenomegaly (20 during acute haematemesis from ruptured oesophageal varices, 20 with endemic hepatosplenomegaly assigned to the same grade of oesophageal varices but with no history of haematemesis) and 20 normal controls. All parameters were markedly altered in the disease groups. Reduced levels of Fg, Plg, &agr;2‐AP and PAI were associated with increasing levels of PA, t‐PA, DD and FDP. Alterations were most marked in the group complicated by acute bleeding. It was concluded that these patients have an enhanced fibrinolytic state. This was probably aggravated in the haematemesis group by an acute haemostatic imbalance that superimposed the low grade chronic DIC reported in cases of hepatosplenic schistosomiasis.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;The activated partial thromboplastin time (aPTT) is the most popular test for monitoring of heparin therapy. The purpose of the present study was to show that an aPTT reagent with good response to heparin can be prepared from synthetic phosphoglycerides. Mixed liposomes were prepared from synthetic dioleoylphosphatidylserine (DOPS), dioleoylphosphatidylcholine (DOPC), and dioleoylphosphatidylethanolamine (DOPE). These liposomes were used in an aPTT test system with kaolin as activator, to evaluate their procoagulant activity in the absence and presence of heparin. For comparison, mixtures of purified non‐synthetic phospholipids were prepared and tested with the same systems. The aPTT and its response to heparin were influenced by the phospholipid class composition and concentration. The presence of phosphatidylserine (PS) was required to reduce the aPTT of normal plasma to values between 30 and 40 s. The presence of phosphatidylethanolamine (PE) in mixed liposomes could modulate the response to heparin. At low PE/PS liposome concentrations (˜ 40 μM), a relatively low response was observed. At high liposome concentrations (˜ 1 mM), the response to heparin increased with the mole fraction of phosphatidylethanolamine. The results obtained with non‐synthetic phospholipid mixtures were similar to those obtained with the synthetic phosphoglycerides. Optimal concentrations of DOPS, DOPE and DOPC were found with which an almost linear response to heparin and to low molecular weight heparin (FragminTM) was observed. Using a mixed liposome consisting of 12 μM DOPS/12 μM DOPC/16 μM DOPE, a doubling of the base‐line aPTT was achieved at approximately 0.2 IU/ml of heparin, and at approximately 1.0 IU/ml of Fragmin. As the chemical composition of the synthetic phospholipid reagent is well defined, it may constitute a step forward in the standardization of monitoring heparin therapy.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;Platelets take up plasma proteins into their alpha granules. Platelet activation releases the alpha granule contents. The goal of this study was to test the hypothesis that human platelets also contain some coagulation factor IX in their alpha granules. Platelets were examined by immunofluorescence microscopy. Activated and unactivated platelets were quick frozen on to slides and dehydratedin situto preserve optimal morphology. The slides were stained by indirect immunofluorescence for factors V and IX. Unactivated platelets showed coarsely granular staining for factor V and finely granular staining for factor IX. Staining for factor V was diffuse after activation, while staining for factor IX disappeared. Thus, the results support the conclusion that platelets contain factor IX which can be released upon activation. Immunoelectron microscopic studies were conducted to more precisely localize the site of the platelet factor IX. As expected, factor V was primarily localized in the alpha granules of unactivated platelets. By contrast, factor IX was observed both in alpha granules and diffusely in the platelet cytoplasm and membrane‐bounded vesicles. After activation, staining for both factors V and IX was primarily in the open canalicular system. The physiological importance of this small amount of factor IX is unknown. However, it may be significant since only a few percent of normal IX levels are required to support haemostasis in the absence of trauma, and platelet factor IX could be released at sites of active coagulation.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;U87MG cells (human glioblastoma) express tissue factor and shed membrane‐derived vesicles enriched in procoagulant activity. Tissue factor antigen has been studied by flow cytometry, immunofluorescent microscopy and Western blotting. Flow cytometric analysis utilized monoclonal antibodies recognizing the tissue factor extracellular domain and the carboxyl‐terminal nine amino acids. Studies with intact and permeabilized cells support the location of the carboxyl‐terminal domain in the cytoplasm, as previously predicted from the protein sequence. Immunofluorescent microscopy revealed a heterogeneous staining pattern, indicating that tissue factor antigen may be clustered on the cell surface. Intense staining was occasionally observed in cytoplasmic extensions and membrane regions that appeared to be extruding from the cells. Western blot analysis of vesicles shed into the culture medium revealed a principal tissue factor band with mobility marginally slower than that of placental tissue factor. Both extracellular and cytoplasmic epitopes were present in this vesicular tissue factor.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;The urinary protein C inhibitor (PCI) binding region in the B&bgr;‐chain of human fibrinogen was examined by ligand blotting, reversephase HPLC and amino acid sequencing. The B&bgr;‐chain, isolated from reduced and pyridylethylated fibrinogen, was digested with staphylococcal V8 protease to yield eight peptides consisting of 10, 12, 13, 13.5, 14, 16, 17 and 18 kDa bands and the cleaved peptides were ligand‐blotted. The 12 kDa band bound to urinary PCI. Moreover, the digested B&bgr;‐chain was isolated by reverse‐HPLC and the elution peak showing positive binding to urinary PCI was sequenced. The N‐terminal amino acid sequence was A V S Q T, which corresponds to Ala106‐ Thr110 in the B&bgr;‐chain. Judging from theM,of this peptide (12 kDa), it comprises the region from Ala106 to Glu192‐Glu210 which are partly located in the D‐region. It is concluded that the urinary PCI‐binding region to the B&bgr;‐chain resides in the sequence of Ala110 to Glu192‐Glu210.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

&NA;The proposal that thrombin binds to dermatan sulphate chains of extracellular proteoglycans has been examined directly using the subendothelium of the rabbit aorta. Freshly excised aortas were de‐endothelialized by balloon catheterin vitroand then incubated with125I‐thrombin to allow adsorption of 20‐30 fmol of thrombin/cm2. Pretreatment of the subendothelium with FPR‐thrombin or chondroitinase ABC partially inhibited thrombin binding, each by approximately 40‐45%. The addition of dermatan sulphate inhibited, competitively, up to 50% of thrombin from binding to the subendothelium whereas chondroitin‐4 or ‐6 sulphates had little or no effect. By contrast, protamine inhibited 90% of FPR‐thrombin binding. Of subendothelium‐bound thrombin, chondroitinase ABC released only a small proportion (3‐12%) of bound thrombin but up to 44% of bound FPR‐thrombin. It is concluded that, when125I‐thrombin is boundin vitroat a concentration of <30 fmol/cm2of aorta intima‐media, approximately 50% of subendothelial125I‐thrombin is bound to dermatan sulphate chains of proteoglycan in the extracellular matrix. The possibility is discussed that dermatan sulphate chains may function as thrombin‐binding loci to control or augment thrombin activity in the ECM of the injured vascular wallin vivo.

ISSN:0957-5235    

出版商:OVID    

年代:1993

数据来源: OVID