ISSN:0953-7104    

DOI:10.3109/09537109309013215

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

In this study, we have examined whether the platelet Fc-receptor, FcγRII (CD32), is associated with either of the two major platelet membrane glycoproteins, the GPIb-IX complex and the GPIIb-IIIa complex. Monoclonal and polyclonal anti-GPIb-IX complex antibodies inhibited to only a moderate degree (<40%) the binding of the anti-FcγRII monoclonal antibody, IV.3, to platelets. In contrast, 6 of 12 anti-GPIIb-IIIa monoclonal antibodies and a polyclonal, affinity-purified rabbit anti-GPIIb-IIIa antibody strongly cross-blocked the binding of IV.3 to platelets. This inhibition was dependent upon the Fab-mediated binding of these antibodies to the GPIIb-IIIa complex since they did not inhibit the binding of IV.3 to Glanzmann's thrombasthenic platelets which have normal levels of FcγRII but lack the GPIIb-IIIa complex. The anti-GPIIb-IIIa monoclonal antibodies, AP3 and VM16a, had no effect on platelet aggregation induced by ADP or thrombin but inhibited Fc-receptor-dependent platelet aggregation as induced by either acetone-aggregated human IgG or by activating monoclonal antibodies against GPIV, PTA1 or CD9. F(ab')2fragments of these two anti-GPIIb-IIIa monoclonal antibodies also inhibited Fc-receptor-dependent platelet aggregation indicating that the observed interference by intact antibody was not due to the direct interaction of the Fc-portion of the antigen-antibody complex with FcγRII. In addition, the inhibitory anti-GPIIb-IIIa antibodies cross-blocked the binding of IV.3 to platelets at 0°C as well as at 22°C suggesting that the observed inhibition was not dependent on the lateral mobility of either GP IIb-IIIa or FcγRII in the platelet membrane. The combined results therefore strongly suggest that the platelet Fc-receptor, FcγRII, is topographically associated with the GPIIb-IIIa complex in the intact platelet membrane.

ISSN:0953-7104    

DOI:10.3109/09537109309013216

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The present work investigates the effects of contamination withPseudomonas aeruginosaon some properties of platelet concentrates, i.e. the ability to transmit light, swirling and the degree of platelet activation and cell lysis. 20 pairs of platelet concentrates were studied over a 7 day period. On day 1, one of the concentrates was inoculated withPseudomonas aeruginosa, while the other served as an identical non-contaminated control. In the contaminated concentrates, swirling and release of platelet factor 4 and lactate dehydrogenase were analysed on day 1, day 2 and day 3; bacterial counts were performed on day 2 and day 3, and on day 7 all these variables were determined in both concentrates. After the 7 day storage period, bacterial growth was found in 13/16 of the contaminated platelet concentrates; all these preparations displayed transmission changes and at least one deviating biochemical parameter. On day 3 all contaminated concentrates had unimpaired swirling, 15/20 had bacterial growth and 10/20 light transmission changes. The study demonstrates that light transmission monitoring on day 3 offers significant advantage (p<0.05) compared to the visual estimation of swirling. The results also show that the optical method often fails to identify contaminated concentrates during early storage.

ISSN:0953-7104    

DOI:10.3109/09537109309013217

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Studies were performed to determine whether formation of platelet aggregates itself, could cause an increase in cytosolic [Ca2+]([Ca2+]i) which is independent of that resulting from the addition of agonists which induce aggregation. An increase in [Ca2+]idid not coincide with aggregate formation when this response was dissociated from the addition of ADP or thrombin by delay either in initiating stirring or, for ADP, in adding fibrinogen. No increase in [Ca2+]ioccurred when aggregation was induced by addition of 1,2-dioctanoylglycerol or of ristocetin, or for chymotrypsin-treated platelets by addition of fibrinogen. The results demonstrate clearly that aggregate formation does not cause an increase in [Ca2+]i, and therefore exclude this possibility as an explanation for the discrepancies observed when [Ca2+]iis measured, using aequorin and Fura2 as probes and as an underlying mechanism to account for contact-induced responses.

ISSN:0953-7104    

DOI:10.3109/09537109309013218

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

We have studied in a homologous system the effect on different platelet functions of cells isolated from 26 human tumor tissues (11 breast carcinomas, 11 colon carcinomas, 2 pancreatic carcinomas, 1 gastric carcinoma and 1 esophageal carcinoma). Tumor cells (105/ml) significantly increased platelet adhesion to glass beads; they were also found to possess a potent platelet aggregating activity and aggregation was accompanied by significant release of ATP and platelet derived growth factor (PDGF) and by production of TXB2. Preincubation of platelets with a low concentration (1µM) of indobufen, a cyclooxygenase inhibitor, significantly reduced tumor cell induced TXB2production and ATP release, while the other platelet functions were not modified. Higher concentrations of the drug (10 or 100µM) were also able to inhibit tumor cell-induced platelet aggregation and PDGF release, while platelet adhesion to glass beads was unchanged even at these doses. Finally, preincubation of neoplastic cells with indobufen (400µM) had no effect on their ability to induce platelet aggregation, TXB2production and ATP release.These data demonstrate that cyclooxygenase blockade in platelets has different effects on several platelet functions activated by the tumor cells that were investigated.

ISSN:0953-7104    

DOI:10.3109/09537109309013219

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

A method for the preparation of a suspension of thrombin-degranulated human platelets is described. Two peptides (RGDS and GPRP) are used to prevent fibrinogen binding and consequent aggregation, and to prevent fibrin polymerization during thrombin activation. A mixture of creatine phosphokinase and creatine phosphate is used to remove ADP. Hirudin and TAMe are used to neutralize thrombin after the platelets have been activated. [14C] Serotonin and PF4 release and electron microscopy demonstrate that the preparation is completely degranulated. After all inhibitors are removed and fibrinogen added, the preparation aggregates rapidly to a mixture of agonists composed of ADP, epinephrine and the synthetic analog of prostaglandin H2/thromboxane A2, U46619. ADP and epinephrine when added individually are both able to induce a clearly detectable aggregation, while U46619 induces only a shape change. The preparation is also suitable for intracellular Ca2+studies and we find that the mixture of agonists produces an increase in the intracellular calcium concentration to about 1µM.

ISSN:0953-7104    

DOI:10.3109/09537109309013220

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Several possibilities have been raised to explain the beneficial effect of l-deamino-8-D-arginine vasopressin (DDAVP) in several hemostatic disorders but, so far, its exact mechanism(s) of action is still unknown. Aiming to throw new light on the problem, we have investigated: (a) whether DDAVP induces platelet activation or quantitative/qualitative modifications of GPs Ib/IX and IIb/IIIa, and (b) the binding to these glycoprotein receptors of von Willebrand factor (vWF) purified from blood obtained before and after administration of DDAVP.Analysis of the expression of GMP 140 and thrombospondin demonstrated no platelet activation following administration of DDAVP. Binding assays and flow cytometry with antibodies against GPs Ib/IX and IIb/IIIa, the study of the ristocetin-dependent vWF binding, and immunoblotting with an anti-GPIb/IX antibody, demonstrated no quantitative or functional changes of these complexes after the infusion of DDAVP. Finally, native vWF purified from cryoprecipitate, and vWF purified from plasma of one DDAVP-infused volunteer, showed similar binding properties to GPIb/IX and GPIIb/IIIa.These results suggest that DDAVP is quite inert on platelet glycoproteins, and the drug-induced appearance of 'supranormal' high molecular weight vWF multimers seems not to modify the interaction of vWF with its main platelet receptors.

ISSN:0953-7104    

DOI:10.3109/09537109309013221

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The effect of vitronectin on platelet aggregation has been investigated. Vitronectin inhibited both thrombin- and ADP-induced platelet aggregation in a dose-dependent manner. A monoclonal antibody (MoAb) to vitronectin increased thrombin-induced platelet aggregation. This effect of the MoAb was not mediated via the platelet Fc-receptor, suggesting that the antibody directly counteracted the inhibitory effect of vitronectin on platelet aggregation. Like some other adhesive proteins such as fibrinogen, fibronectin, and von Willebrand factor, vitronectin contains the amino-acid sequence Arg-Gly-Asp (RGD) which enables binding to the platelet membrane glycoprotein complex IIb/IIIa (GPIIb/IIIa). The results of this study indicate that vitronectin can modulate the function of fibrinogen on platelet aggregation by interfering with the binding of fibrinogen to GPIIb/IIIa in activated platelets.

ISSN:0953-7104    

DOI:10.3109/09537109309013222

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor