ISSN:0953-7104    

DOI:10.3109/09537109309013197

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Severe heparin-associated thrombocytopenia (SHAT) is a rare, life-threatening condition. The aim of this prospective pilot study was to determine the safety and efficacy of dipyridamole-heparin infusion (DHI) in the management of the condition. We studied 6 patients (4 males and 2 females) aged 28 to 80 years (mean 50.5±14.2) with deep venous thrombosis and/or pulmonary embolism who developed SHAT a few days following heparin therapy. Heparin-dependent platelet aggregating factor was demonstrated ex vivo in the plasma of 4 patients. 240–300 mg of dipyridamole/day (4 mg/kg/day) was mixed with heparin in the same bag and given as a continuous intravenous infusion. Anticoagulation was continued successfully along with significant platelet recovery over a few days. This regimen was without side-effects. We conclude that DHI may provide an effective therapy for patients with SHAT.

ISSN:0953-7104    

DOI:10.3109/09537109309013198

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

In recent years there has been a growing interest in measurement of platelet activation. Fluorescence-activated flow cytometry has a high sensitivity and allows the study of whole blood. Platelet-bound fibrinogen, thrombospondin, the alpha-granule protein GMP 140 (CD62) and the fibrinogen receptor have been used as markers for platelet activation utilising fluorescence-labelled antibodies. However, when a labelled antibody used in flow cytometry reacts with the antigen, an immune complex is formed. We have shown that immune complexes containing mouse or rabbit IgG, but not chicken IgG, causes platelet activation. Several monoclonal antibodies directed towards platelet glycoprotein receptors also activate platelets. Suggested potential mechanisms have been direct receptor activation, FcR mediated activation and complement activation. We demonstrate that the activation in platelet-rich plasma by the monoclonal anti-GPIb antibody AN51 could not be prevented by antibodies towards the Fc-receptor, but the antibody induced an extensive binding of C1q. The findings suggest that the complement system has an important role in platelet activation. We would suggest that monoclonal antibodies intended for use in measuring platelet activation should be screened for induction of C1q and C5 binding to the platelets. Chicken antibodies are favourable for the measurement of platelet bound plasma proteins as they do not induce platelet activation.

ISSN:0953-7104    

DOI:10.3109/09537109309013199

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

To extend our investigations on the interaction between diabetic platelets and endothelium, we tried to identify the molecular components involved in the increased adhesiveness of diabetic platelets to cultured valvular endothelial cells (VEC). Platelets from diabetic patients were radiolabeled with (3H]-adenine, incubated for 30 min at 37°C with confluent VEC grown in medium containing 4.5 g/L glucose, and the monolayer-associated radioactivity was used to calculate the adhesion index. To identify the plasmalemma proteins involved in the adhesion process, platelets were incubated for 30 min prior totheadhesion assay with one of the following monoclonal antibodies: AP-2 (anti GP IIb-IIIa), AP-5 (anti GP IIIa), TM 83 (recognizes an epitope other than the fibrinogen binding site in GP IIIa), PECAM 1.2 (anti PECAM-1) or a polyclonal anti-fibronectin receptor (anti FnR). In addition, two synthetic peptides, RGDS and GPRP, applied alone or together, were used. The effect of paraformaldehyde fixation of diabetic platelets on their adhesion was also tested. The results showed that except for TM 83, all antibodies reduced significantly (∼45%) the adhesion index of diabetic platelets to VEC. The synthetic peptides also decreased the adhesion by∼30%. Paraformaldehyde-fixed diabetic platelets fail to adhere to VEC. Taken together these observations suggest that: (1) platelet GP IIb-IIIa complex, PECAM-1 and FnR may be instrumental in the increased adhesion of diabetic platelets to VEC; (2) fibrinogen binding sites in the GP IIb-IIIa complex and fibrinogen/fibrin are important contributors to the adhesion process and (3) impairment of diabetic platelets adhesion by chemical fixation, supports the role of cytoskeletal proteins reorganization and redistribution of some plasmalemma components during adhesion.

ISSN:0953-7104    

DOI:10.3109/09537109309013200

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

We have previously demonstrated that cathepsin G is a strong platelet agonist. However, the ability of cathepsin G to function in this capacity in vivo has remained speculative because the enzyme might be expected to be rapidly neutralized by the high concentration of circulating plasma antiproteases. To examine the physiological significance of cathepsin G as a paracrine mediator, indo-1 and14C-5-hydroxytryptamine-loaded platelets were incubated with autologous unloaded neutrophils specifically activated by addition of fMet-Leu-Phe. FMet-Leu-Phe induced substantial increases in cytosolic calcium and 5-hydroxytryptamine release even in the presence of increasing amounts of citrated plasma, indicating that cathepsin G can stimulate platelets under conditions similar to those that may be encountered in vivo. Platelet stimulation was abolished by addition ofα1-antichymotrypsin, demonstrating that cathepsin G was the neutrophil mediator responsible for cell activation. Having obtained evidence that cathepsin G can function in the presence of plasma, we measured its ability to hydrolyze phosphatidylinositol 4,5-bisphosphate (PtdIns4,5-P2) and generate phosphatidic acid (PtdA) in aspirin-treated platelets. Our previous observations suggested that cathepsin G stimulates phospholipase C since the protease induces an elevation in [Ca2+]i in the presence of exogenous EGTA. Within 10 s of stimulation cathepsin G induced a transient loss in [32P]-PtdIns4,5-P2 and a concurrent increase in [32P]-PtdA. [32P]-PtdA formation was increased over 15-fold in a concentration-dependent manner by cathepsin G. We also determined that cathepsin G induces the release of the lysosomal enzymeβ-N-acetyl-glucosaminidase. Both the increase in PtdA and the release ofβ-hexoseaminidase were comparable to responses elicited by thrombin. These results provide additional evidence that cathepsin G is a strong platelet agonist, support the conclusion that cathepsin G stimulates phospholipase C, and clearly suggest that cathepsin G can function as an agonist in vivo.

ISSN:0953-7104    

DOI:10.3109/09537109309013201

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

[Ca2+]iand pHiwere measured in unstimulated and thrombin-stimulated platelets from young (3 months) and aged (24 months) rats in the presence and absence of external Ca2+. There was no difference in the basal level of [Ca2+]ibetween young and aged rat platelets in the presence of external Ca2+. On the other hand, thrombin-induced Ca2+mobilization was markedly increased in aged rat platelets compared to young rat platelets in the presence of external Ca2+. This difference in Ca2+mobilization was more pronounced in the absence of external Ca2+, suggesting that Ca2+release from intracellular storages was enhanced in aged rat platelets. In contrast to what was observed for Ca2+, the basal level of pHiin aged rat platelets was higher than that in young rat platelets whereas thrombin-induced pHiincreases (ΔpH) were similar in both groups in the presence and absence of external Ca2+. These results indicate that age-associated changes occur in thrombin-induced Ca2+release from intracellular storages in rat platelets. These changes seem to be related to those in basal pHilevels.

ISSN:0953-7104    

DOI:10.3109/09537109309013202

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Diabetic patients are at higher risk of development of cardiovascular complications than the general population. The role of platelets in the pathogenesis of these complications is still controversial, it being difficult to ascertain whether altered platelet function is acauseorconsequenceof vascular complications of diabetes. Measurement of urinary 11-dehydro-thromboxane has been proposed as a reliable index of in vivo platelet activation and has been reported to be significantly higher in non insulin-dependent diabetic patients with micro- or macrovascular complications. We therefore studied the effect of ticlopidine, an antiplatelet drug acting through mechanisms different from cyclo-oxygenase inhibition, on urinary 11-dehydro-TXB2excretion in diabetic patients with macrovascular complications. The results indicate that urinary excretion of 11-dehydro-TXB2after ticlopidine treatment is not different from pre-treatment values, suggesting that the chosen parameter might not be reliable for monitoring the antiplatelet activity of ticlopidine and possibly of other drugs which do not directly affect arachidonic acid metabolism.

ISSN:0953-7104    

DOI:10.3109/09537109309013203

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

ISSN:0953-7104    

DOI:10.3109/09537109309013204

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

ISSN:0953-7104    

DOI:10.3109/09537109309013205

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor