摘要:

In 1987 we reported that when blood was forced through a fine filter under pressure in the filterometer the platelets aggregated and blocked the filter, von Willebrand factor (vWF) and glycoprotein (Gp) Hb/IIIa and calcium were involved. Results with anti-GpIb were equivocal. We now report that all the anti-GpIb antibodies studied, glycocalicin, as well as some concentrations of aurin tricarboxylic acid caused platelet aggregation in the pre-filter blood and therefore could not be used in the filterometer. Using two different molecules that prevent vWF binding to GpIb and two anti-GpIIb/IIIa antibodies at two pressures it has now been shown that GpIb, vWf and high shear are primarily responsible for platelet retention at 0–5 s. Progressive platelet retention studied between 20 and 40 s required high shear and GpIIb/IIIa after the calcium influx mediated by GpIb/vWF binding. When GpIb was inhibited, GpIIb/IIIa could not function normally, so GpIb inhibition resulted in decreased aggregation both at 0–5 s and at 20–40 s. Anti-GpIIb/IIIa caused a minimal decrease in retention at 0–5 s and marked inhibition at 20–40 s. These findings fit and amplify concepts derived from other high shear methodologies. A diagram is presented of the events leading up to the final 'passivation' of the 'thrombus' in the filter when the surface of the aggregated platelets becomes unattractive.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

This study evaluates the effects of time and temperature variables on routine coagulation assays [Prothrombin Time test and Activated Partial Thromboplastin Time (APTT) test]. Four different groups were studied: healthy volunteers, hospitalized patients not receiving anticoagulants, patients receiving oral anticoagulant therapy and patients receiving unfractionated heparin therapy. Samples were subjected to one of four conditions: (1) centrifuged immediately and stored at room temperature (20–22°C); (2) centrifuged immediately and stored on ice (4°C); (3) stored as whole blood without centrifugation, at room temperature and (4) stored without centrifugation, on ice. Coagulation tests were performed as soon as possible after phlebotomy and at specified times up to 24 h. Our data demonstrate that prothrombin time results are stable for up to 24 h, remaining constant regardless of storage conditions. APTT assays are stable for up to 8 h, except for patients receiving unfractionated heparin therapy. Heparinized samples, when stored uncentrifuged at room temperature, demonstrate a clinically significant shortening of the APTT and individual samples demonstrate a greater than 50% decrease in ex-vivo heparin levels at 4 h.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The action of fibrinolytic enzymes (plasmin, miniplasmin, neutrophil leukocyte elastase) on the blood-brain barrier is investigated. The binding and the effects of the fibrinolytic enzymes are studied in the first subcultivation of human brain capillary endothelial cells.125I-labeled plasmin, miniplasmin and neutrophil leukocyte elastase bind to confluent monolayers of cultured endothelial cells with dissociation constants of 1 × 10-8mol/l, 4.8 × 10-7mol/l and 1.8 × 10-8mol/l, respectively, and the number of binding sites varies between 2.3 × 105and 7.5 × 106per cell. Following treatment of the cultured cells with purified and active-site titrated proteases, the changes in morphology of individual cells are analyzed with computerized morphometry. At low concentrations (in nanomolar range) all studied fibrinolytic proteases induce reduction of the cell area; the minimal size is achieved in 20–80 min after the application of an enzyme and the effect is completely reversed in 15 min after its removal. A possible in-vivo consequence of these in-vitro findings is studied in an organ-perfusion model: rat hemisphere is perfused with a protease solution followed by a circulating phase-borne tracer (horse-radish peroxidase). In perfused rat hemisphere, the fibrinolytic enzymes open the blood-brain barrier to the circulation-borne tracer. These results support the concept that fibrinolytic enzymes interact with the brain microvascular endothelium and thus affect the integrity of the blood-brain barrier through active cell contraction.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Development of an abdominal aortic aneurysm (AAA) may be a product of generalised atherosclerosis. If that is indeed the case, we would expect similarities in various risk factors and other markers in common with occlusive peripheral arterial disease (peripheral arterial disease), and less congruity with healthy controls. To test this hypothesis, we recorded the major risk factors for atherosclerosis, two markers of endothelial dysfunction, and soluble adhesion molecules in 21 patients with an uncomplicated AAA free of symptomatic peripheral arterial disease, 42 patients with peripheral arterial disease, and 42 healthy controls who were matched, as a group, for age and sex. After adjusting for smoking, there were no significant differences in blood pressure, fibrinogen, soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1 or lipoproteins between the groups. However, markers of endothelial integrity von Willebrand factor and soluble thrombomodulin were both higher (P< 0.05) only in peripheral arterial disease patients. Relative to the controls, platelet marker soluble P-selectin was increased in AAA (P< 0.01) and in the peripheral arterial disease patients (P< 0.05). Levels were higher in AAA patients than in peripheral arterial disease patients (P< 0.05). Our laboratory data suggest that the pathophysiology AAA and peripheral arterial disease are not identical.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Clinical laboratories are at present confronted with increasing demands for thrombophilia work-up, which may seriously overwhelm their capacity. Recently, methods able to investigate the protein C anticoagulant pathway globally have been proposed. In this study we investigated the reliability of one such method for its ability to detect patients with known defects of the pathway by testing plasmas from patients with the FVQ506mutation, with congenital protein C, protein S or antithrombin deficiencies, and patients with previous history of thrombosis, but no identifiable defects. The results show that the new global test fulfils the requirements for congenital protein C deficiency and activated protein C resistance associated with the FVQ506mutation, which account for more than half of the congenital defects found in thrombophilia. However, congenital protein S deficiency very often remains undetected by this test. Improvement of sensitivity toward this component of the protein C anticoagulant pathway would enroll the global test as a suitable candidate to explore the pathway. Since antithrombin, which also remains undetected by this test, is an additional important risk factor for venous thrombosis, devoting time and effort to developing global tests able to detect defects in both the antithrombin and protein C pathways is warranted.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

In healthy volunteers, the plasma total tissue factor pathway inhibitor (TFPI) level was 68.7 ± 14.1 ng/ml; the plasma free TFPI level, 17.7 ± 5.4 ng/ml; the lipoprotein-associated TFPI (LP-TFPI), 51.1 ± 12.0 ng/ml; the free TFPI/total TFPI ratio 0.26 ± 0.07; and the plasma tissue factor levels were 149 ± 46 pg/ml.Plasma tissue factor levels in patients with disseminated intravascular coagulation (DIC) were significantly higher than those in pre-DIC patients or in non-DIC patients. Plasma total-TFPI, free-TFPI and LP-TFPI levels were significantly higher in DIC patients than those in pre-DIC patients or in non-DIC patients. Before the onset of DIC, the plasma levels of tissue factor gradually increased, and 3 days before the onset of DIC they were significantly higher than those in non-DIC patients. The plasma levels of tissue factor reached their highest level 1 day before the onset of DIC and gradually decreased after the onset of DIC. Plasma levels of total-TFPI, free-TFPI, and LP-TFPI gradually increased before the onset of DIC, and the total-TFPI and LP-TFPI reached their highest levels at the onset of DIC. Plasma free-TFPI reached highest level one day after the onset of DIC. During the clinical course of DIC, the plasma level of tissue factor was the first to increase, then that of LP-TFPI and finally the free-TFPI plasma levels. These differences in the peak plasma levels of tissue factor, free-TFPI, and LP-TFPI might be related to the clinical course of DIC.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Low-molecular-weight heparins (LMWHs) have been shown to be effective in the prevention of deep vein thrombosis (DVT) after major orthopaedic surgery, such as total hip replacement (THR). The efficacy and safety of two LMWHs, reviparin and enoxaparin, were compared in a prospective, double-blind, double-dummy study involving 498 patients undergoing total hip replacement. Drugs were given preoperatively in doses of 4200IU anti-Xa for reviparin and 40 mg (approximately 4000IU anti-Xa) for enoxaparin. The endpoint for the assessment of efficacy was venographically confirmed DVT. The endpoint for the assessment of safety was clinically important bleeding during study treatment. There were evaluable venograms for 460 patients (93%). Of these 460 patients only 416 fulfilled the study protocol. A total of 39 DVTs (9%) occurred in this per protocol group of patients, 21 (10%) in the reviparin group, and 18 (9%) in the enoxaparin group. The incidence of proximal DVT was 6% in each group. The two treatments were found to be equivalent in terms of efficacy. For the 460 patients with venograms (intent-to-treat) venous thrombosis occurred in 49 patients (11%). Of the 230 patients randomly assigned to reviparin, 27 had a DVT (12%), whereas 22 of the 230 enoxaparin patients (10%) had a DVT. The incidence of proximal DVT was 6% in both groups. Again, the two treatment groups were clinically equivalent in efficacy. Major bleeding complications occurred in two enoxaparin- and one reviparin-treated patient. Peri- and postoperative blood loss and blood transfusions were similar in both treatment groups. The reviparin-treated patients had fewer haematomas, bruisings and higher red cell counts and lower haemoglobin levels than the enoxaparin-treated patients.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The effects of SR121566, a new inhibitor of the glycoprotein (GP) IIb/IIIa complex on platelet activation and platelet-leukocyte interactions, as well as on thrombin generation were investigated. SR121566 dose-dependently inhibited adenosine diphosphate (ADP)-induced platelet fibrinogen binding determined either by flow cytometry analysis (IC50= 50 nmol/l) or by measuring the binding of125I-fibrinogen to activated human gel-filtered platelets (IC50= 20 nmol/l). Consistent with its inhibitory effects on platelet fibrinogen binding, SR121566 demonstrated a dose-dependent inhibition of collagen-, ADP- or thrombin-induced platelet aggregation with IC50 values ranging between 20 and 60 nmol/l. SR121566, even tested at high concentrations, did not significantly affect ADP-induced platelet-leukocyte aggregate formation. The GPIIb/IIIa antagonist strongly inhibited thrombin generation in both native clotting blood and recalcified whole blood, suggesting that SR121566, by interfering with the platelet-activation events involved in facilitating thrombin generation, may also function as an anticoagulant, an effect which may contribute to its antithrombotic properties in humans.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Unfractionated as well as low-molecular-weight heparins (LMWH) are known to cause an increase in blood levels of tissue factor pathway inhibitor (TFPI). To study the effect of a newly developed supersulfated LMWH (IK-SSH, Iketon Farmaceutici) on TFPI concentrations in human plasma, the compound was injected into volunteers at doses of 0.14, 0.33 and 0.66 mg/kg intravenously or 0.33, 0.66 and 1.0 mg/kg subcutaneously. At certain known times blood was drawn and plasma levels of both total and free TFPI were measured using enzyme-linked immunosorbent assay methodology. Baseline plasma concentrations of TFPI were 72.2 ± 3.1 ng/ml for total and 10.8 ± 0.8 ng/ml for free TFPI. Intravenous or subcutaneous injection of IK-SSH led to a strong and long-lasting rise in TFPI levels which were increased more than 5-fold for total TFPI and more than 30-fold for free TFPI. Maximum TFPI levels were reached 5–10 min after intraveous and 60 min after subcutaneous administration. IK-SSH caused prolongation of ex-vivo clotting times in the APTT and Heptest® assay, whereas thrombin time was not affected. Anticoagulant actions of IK-SSH showed a significant correlation to plasma concentrations of TFPI and they are thought to be based at least partially on the release of TFPI from vascular sites.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Recent evidence suggests a major role for prothrombin as a risk factor for thrombosis. However, estimating prothrombin levels from a deficient plasma-based clotting assay (factor lie) is expensive and technically difficult in the setting of population-based research. We report the development of an enzyme-linked immunosorbent assay (ELISA) for prothrombin using purified antigen and polyclonal anti-prethrombin-1 IgG. Three different quality control plasmas had coefficients of variation (CV) of 6.5%, 4.9%, and 4.8%. Analytical recovery averaged 103.8%. Results from the ELISA correlated well with factor lie results (r= 0.75). The 5th-95th percentile range for healthy men (n= 10) and women (n= 16) was 97.7 μg/mI to 161.8 μg/ml. The assay exhibited no significant cross-reactivity with other vitamin-K-dependent proteins. Prothrombin showed no diurnal variation. In a study of biovariability the analytical variability, CVA, was 3.1%; the within-subject variability, CVI, was 7.3%; the between-subject variability, CVG, was 14.5%. The critical difference for sequential values (i.e. the smallest percentage change unlikely to be due to CVAor CVI) significant atP= 0.05 was 21.9%. The index of individuality, CVI/CVG, was 0.50. On the basis of the overall biovariability data, primarily the index of individuality, prothrombin as measured in our ELISA is well suited for applications in population-based research.

ISSN:0957-5235    

出版商:OVID    

年代:1998

数据来源: OVID