ISSN:0953-7104    

DOI:10.3109/09537109409005523

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Protein phosphatase (PP) activities have long been known in platelets, but their physiological roles in platelet reactions are not well understood. Since the discovery of the okadaic acid (OA) class of compounds, potent and cell-permeable PP 1/2A inhibitors, evidence for the active involvement of PP1/2A in platelet reactions has rapidly accumulated. This article reviews the possible involvement of PP1/2A in platelet function by focusing on the effects of OA class compounds on agonist-induced platelet reactions.

ISSN:0953-7104    

DOI:10.3109/09537109409005524

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Platelets are involved in atherogenesis, partly through the release of smooth muscle cell mitogens and chemoattractants such as platelet-derived growth factor (PDGF). The St Thomas' Atherosclerosis Regression Study (STARS) demonstrated that a cholesterol-lowering diet induced angiographic regression of coronary artery disease in 74 men. Serum PDGF concentrations were not different at the end of the study between patients randomised to receive diet, with or without cholestyramine: usual care (UC) median 53.6 pM (interquartile range 15.3), diet (D) 60.0 pM (29.7), diet and cholestyramine (DC) 51.5 pM (13.0), 2p = 0.23. Similarly, mean platelet volume (MPV), a marker of platelet function, did not differ between the three groups: UC 8.0 fl (1.1), D 8.6 fl (0.8), DC 9.0 fl (1.4), 2p = 0.16. PDGF concentrations and MPV did not correlate with lipid concentrations or angiographic indices of regression. These findings suggest that platelet function, as measured by PDGF and MPV, does not change during, or contribute to, dietary-induced regression of coronary artery disease.

ISSN:0953-7104    

DOI:10.3109/09537109409005525

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Platelets have been shown to be hyperresponsive during pregnancy. Studies in whole blood have revealed increased‘spontaneous’platelet aggregation (SPA) and increased aggregation and14C-5HT release in response to adrenaline. Here we have extended previous studies. We have explored the possibility that the nature of the agent used to anticoagulate the blood may have influenced the results obtained, and, for the first time, have investigated the effects of streptokinase (SK) on platelets in whole blood during pregnancy.We found that increased SPA is present during pregnancy irrespective of the anticoagulant used. Also, platelets in blood taken during pregnancy aggregate more extensively in response to adrenaline, even though the type of anticoagulant influences the extent of14C-5HT release that accompanies the aggregation response. SK was found to induce platelet aggregation in whole blood and this was also independent of the anticoagulant used. Further, SK induced aggregation at a lower concentration than in blood from non-pregnant female volunteers (NFV). Increased platelet responses had always returned to values similar to those for NFV by 12 weeks post-natal.These studies confirm the existance of a generalized increase in platelet reactivity during pregnancy, indicate that this is not an artefact consequent to the use of a particular anticoagulant, and provide new information on the effects of SK on platelets during pregnancy.

ISSN:0953-7104    

DOI:10.3109/09537109409005526

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Changes in membrane polarity of human platelets during the interaction with PAF were investigated by measuring the steady-state fluorescence emission spectra of 2-dimethylamino(6-lauroyl)naphthalene (Laurdan), which is known to be incorporated at the hydrophobic-hydrophilic interface of the bilayer, displaying spectral sensitivity to the polarity of its surroundings. Laurdan shows a marked steady-state emission red-shift in polar solvents, with respect to non-polar solvents. Our results demonstrate that platelet activation factor (PAF) (10-7M) induces a red-shift of the fluorescence emission spectra of Laurdan. These changes were not observed in the presence of the PAF antagonist, L-659,989. These data suggest that the interaction of PAF with its specific receptor and the signalling pathways involved in platelet activation are accompanied by an increase in polarity at the hydrophobic-hydrophilic interface of human platelet membranes.

ISSN:0953-7104    

DOI:10.3109/09537109409005527

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Clinical disorders such as malignant diseases, infectious diseases or autoimmune diseases are associated with circulating immune complexes. These immune complexes can activate the complement system in the blood or interact with complement or Fc receptors on the surface of cells. Complement activation may cause cytolysis and the immune complex interaction with receptors may cause activation of cells. We have used flow cytometry and labelled chicken antibodies to study the in vitro effects of model immune complexes on platelets and show that such immune complexes activate platelets and deposit Clq, C4 and C5 on them. Either low levels or no C3 could be detected on the platelets by flow cytometry. The immune complexes also induced formation of microparticles from purified platelets. Flow cytometry might become a useful tool in estimation of risk of thrombosis or thrombocytopenia in patients with autoimmune disease. Chicken antibodies are superior to mammalian antibodies for the measurement of platelet bound plasma proteins as they do not induce complement activation or platelet activation.

ISSN:0953-7104    

DOI:10.3109/09537109409005528

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The aim of this study was to determine the contribution of increased PGD2formation to the anti-aggregatory action of a thromboxane A2(TXA2) synthase inhibitor and TP receptor antagonist (ZD1542) against collagen-induced human platelet aggregation in citrated whole blood using the prostaglandin (PG) DP receptor antagonists AH6809 and 868C84.ZD1542 (1μM) was markedly more effective than aspirin (1 mM) against collagen-induced aggregation (73 vs 52% inhibition respectively), and formation of both PGI2and PGD2was evident in the presence of ZD1542. Added PGD2(30 nM) inhibited aggregation to a similar extent as did ZD1542 (68% inhibition) and the antiaggregatory action of PGD2was abolished, both by AH6809 (50μM) and by 868C84 (0.5μM). AH6809 significantly reduced the antiaggregatory efficacy of ZD1542, but did not modify the efficacy of aspirin. In contrast, 868C84 had little effect on the antiaggregatory efficacy of ZD1542 whereas 868C84 in combination with aspirin inhibited platelet aggregation more markedly than did aspirin alone.These findings indicate that formation of PGD2contributes to the antiaggregatory action of ZD1542 against collagen-induced human platelet aggregation. However, results obtained with the DP receptor antagonist 868C84 were inconclusive since 868C84 has a limited inhibitory effect against collagen-induced human platelet aggregation which is independent of eicosanoid formation.

ISSN:0953-7104    

DOI:10.3109/09537109409005529

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Disturbances of platelet morphology, coagulation and fibrinolysis were studied 3, 6, and 24 h following administration ofBothrops jararacasnake venom to rabbits (80μg/kg, i.v.). The activation of coagulation and fibrinolytic systems was demonstrated by a significant decrease in fibrinogen concentration, and an increase in fibrin(ogen) degradation product concentration, respectively. However, the prothrombin activity remained within normal limits throughout. Significant thrombocytopenia was observed 3 h following venom administration. A decrease in platelet dense body numbers was observed until 24 h.‘Exhausted’platelets and evidence of granular secretion were frequently observed in envenomed rabbits. The open canalicular system was only dilated in extensively degranulated platelets. The mean platelet area and boundary values were not significantly different from control group. Therefore,B. jararacavenom can stimulate platelets in vivo, inducing release of platelet granular content. The etiology of thrombocytopenia inB. jararacaenvenoming seems to be a multifactorial process, causing platelet sequestration.

ISSN:0953-7104    

DOI:10.3109/09537109409005530

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The risk factors for haemorrhage in chronic idiopathic thrombocytopenic purpura (ITP) remain poorly understood. We classified 49 patients with chronic ITP into two groups on the basis of the presence (n= 11) or absence (n= 38) of hypertension and/or diabetes mellitus, and then analyzed their clinical and immunological characteristics. The patients with hypertension and/or diabetes were older than those without these complications. There were no significant differences between the two groups with regard to platelet count or the levels of platelet-associated immunoglobulin G, platelet-associated immunoglobulin M, and platelet-associated C3. Positivity for anti-glycoprotein IIb/IIIa and anti-glycoprotein Ib autoantibodies was also similar. However, severe purpura and a poor response to prednisolone were far more common in the patients with hypertension and/or diabetes. We conclude that ITP complicated by hypertension and/or diabetes may be resistant to prednisolone and thus require more careful treatment.

ISSN:0953-7104    

DOI:10.3109/09537109409005531

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Platelet lipid composition was determined in subjects with hypercholesterolemia (HC) (9.17±2.15 mmol/L), hypocholesterolemia (HYPOC) (3.29±1.01 mmol/L), and normocholesterolemic controls (NC) (5.29±0.82 mmol/L). Lipid composition was quantitated in washed platelets by measuring platelet cholesterol (C) and phospholipid (PL) content, C/PL molar ratio and platelet PL phosphatidylcholine (PC) to sphingmyelin (SM) ratio. There was a significant increase and a significant decrease in C/PL molar ratio in subjects with HC and HYPOC compared to normals (0.74±0.06 and 0.53±0.06 vs 0.59±0.04, p<0.01, respectively). These alterations were due to a significant change in platelet C content, whereas, platelet PL content was stable. PC/SM ratio was markedly decreased in HYPOC compared to NC (0.80±0.18 vs 2.03±0.18, p<0.01, respectively). These results indicate that blood cholesterol is a major determinant of platelet membrane lipid composition. This effect may be of concern in relation to a possible excess morbidity in patients not only with HC, but also with a low blood cholesterol.

ISSN:0953-7104    

DOI:10.3109/09537109409005532

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor