ISSN:0953-7104    

DOI:10.3109/09537109009005474

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Platelet activation by thrombin and most other agonists appears to require two second messenger systems that are both initiated by phospholipase C-catalysed cleavage of phosphatidylinositol phosphates leading to: 1. formation of inositol phosphates with a subsequent rise in intracellular calcium from intracellular stores and from outside the cell; 2. formation of diacylglycerol with subsequent activation of protein kinase C. This review examines inositol phosphate metabolism in platelets and its involvement in calcium metabolism.

ISSN:0953-7104    

DOI:10.3109/09537109009005475

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

‘Ex vivo’testing of functional platelet properties using conventional techniques reflects the overall behaviour of the whole platelet population in the sample under investigation. Since many functional aspects depend on ultrastructural constituents which may vary from one cell to another, multiparameter single cell analysis of platelets may be advantageous in providing direct insight into deviations at the cellular level relevant to the pathophysiology of disease states such as bleeding disorders or thrombophilia.Immunolabelling with monoclonal antibodies against membrane antigens has been combined with flowcytometry to provide a standardized, highly specific and sensitive analytical tool. The assay has been optimized for simultaneous two colour fluorescence staining, and this allows the testing of whole blood to provide a quick monitoring method for the differential diagnosis of thrombasthenic diseases like Bernard Soulier's syndrome or Glanzmann's thrombasthenia in which typical staining patterns lack the specific fluorescence for glycoproteins Ib and IIb/IIIa respectively. Also changes in the antigenicity of the outer membrane of activated platelets are detectable with monoclonal antibodies against specific antigenic epitopes such as thrombospondin (a secretion marker) orα-granule and lysosomal proteins (extrusion markers). However, for detection of activated platelets in diseases associated with a prethrombotic state, the procedures for immunolabelling platelets with monoclonal antibodies and instrumental detection sensitivity remain to be optimized.After further development, flowcytometric assays of the functional status of individual platelets may be superior to the measurement of the indirect plasma markers such as platelet factor 4 orβ-thromboglobulin for routine diagnosis of the prethrombotic state.

ISSN:0953-7104    

DOI:10.3109/09537109009005476

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Dopamine is taken up by platelets by an energy and temperature dependent process that does not involve a known dopamine receptor. Whilst dopamine uptake by platelets has been shown to be altered in several disease states, little is known about factors controlling dopamine uptake by platelets which could cause such changes. As phorbol esters have been shown to affect dopamine functions in other tissues we examined the effect of phorbol esters on dopamine uptake by human platelets.Phorbol 12,13-dibutyrate increased [3H]-dopamine uptake by platelets in a dose dependent manner. Similarly, phorbol 12,13-didecanoate increased [3H-dopamine uptake by platelets but 4αphorbol 12,13-didecanoate, which does not affect protein kinase, did not. Staurosporin, a protein kinase inhibitor, reversed the effect of phorbol 12,13-dibutyrate.These data suggest protein kinases can modulate dopamine uptake by platelets.

ISSN:0953-7104    

DOI:10.3109/09537109009005477

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Platelet aggregation in response to ADP, adrenaline, collagen, arachidonic acid and ristocetin was measured in a large population of healthy Saudi males (n = 393) and females (n = 221) whose age ranged from 11–60 years. The number of observations ranged from 130 for one of the doses of ristocetin (1.0 g/l) to 554 for one of the doses of ADP (2.0 mol/l). Females exhibited more enhanced aggregation responses than males. Blood groups, smoking and body weight had no significant effect on platelet aggregability. No significant variations were noted when morning versus afternoon measurement were compared. The results are discussed and compared to previous reports based on small population studies. The data obtained represent the normal pattern of platelet aggregation in healthy Saudis.

ISSN:0953-7104    

DOI:10.3109/09537109009005478

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Studies from our laboratory have demonstrated that epinephrine via alpha2-adrenoreceptor modulation can restore the sensitivity of aspirin-treated platelets to the action of agonists independent of secretion of granule contents or synthesis of prostanoids. The present study has evaluated the effects of full strength aspirin (take on alternate days) and low dose aspirin (taken daily) and sought to determine whether agents which antagonise alpha or beta adrenergic receptors can prevent the corrective influence of epinephrine on aspirin-treated platelets. Adult volunteers were given 325 mg aspirin every other day or 80 mg aspirin daily. After confirming the inhibitory effect of aspirin, these individuals were given yohimbine (5 mg), atenolol (100 mg), verapamil (160 mg) or ethanol (white wine 8 oz). Two hours later, blood was drawn for platelet studies. Cells exposed to aspirin did not aggregate when stirred with arachidonate (0.45 mM) or epinephrine (5 M) alone. Addition of epinephrine to aspirin treated platelets restored the sensitivity to the action of arachidonate and resulted in irreversible aggregation. Ethanol and verapamil at the concentrations tested did not potentiate the action of aspirin. Ingestion of yohimbine, an alpha2-adrenergic antagonist, or atenolol, a beta blocker, prevented the corrective influence of epinephrine on aspirin-treated refractory platelets. Results suggest that alpha and beta blockers may serve a useful role in reinforcing the antithrombotic influence of aspirin in vivo.

ISSN:0953-7104    

DOI:10.3109/09537109009005479

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

In this study, we have used a platelet counting technique to measure platelet aggregation in whole blood from thrombocytopaenic patients who had platelet counts in the range 18×109/I-85×109/1. Aliquots of blood were incubated with platelet agonists in a shaking water bath at 37°C. Platelet aggregation was quantified by measuring the fall in single platelets counted in an Ultra-Flo 100 Whole Blood Platelet Counter. ADP (2 M), collagen (1 g/ml) and ristocetin (0.5–2 mg/ml) induced a fall in platelet count of 50%, 60% and 80% respectively. It is concluded that the present method can be used as part of the screening procedure to determine platelet function disorders when platelet counts are too low for aggregation studies with the more widely used photometric technique. A. R. Saniabadi, C. D. Forbes, J. Belch, Department of Medicine, Ninewells Hospital, Dundee, G. Lowe, Department of Medicine, Royal Infirmary, Glasgow, J. C. Barbenel, Bioengineering Unit, University of Strathclyde, Glasgow, UK.

ISSN:0953-7104    

DOI:10.3109/09537109009005480

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Platelet concentrates (PC) were stored for 7 days at 22°C in either CPDA-1 plasma (control) or one of three plasma-free media, namely a Tyrodes solution (BTST) fortified with citrate and with additional phosphate for buffering effect; Plasma-Lyte A solution (PCD) fortified with dextrose and citrate; and Ringers/CPD-50 (10:1) solution (RCPD) buffered with phosphate, all with a pH of 7.4. Parameters monitored included platelet count, pH, hypotonic shock response, aggregation response to single and paired agonists, and release by platelets of endogenous LDH, ATP and 5HT. BTST was shown to be a satisfactory plasma substitute over the entire storage period. PCD gave similar results over 4 days, although the decrease in pH was more marked. In all test systems RCPD was shown to be a poor plasma substitute.

ISSN:0953-7104    

DOI:10.3109/09537109009005481

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

ISSN:0953-7104    

DOI:10.3109/09537109009005482

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

ISSN:0953-7104    

DOI:10.3109/09537109009005483

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor