ISSN:0953-7104    

DOI:10.3109/09537109409006043

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

ISSN:0953-7104    

DOI:10.3109/09537109409006035

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

ISSN:0953-7104    

DOI:10.3109/09537109409006036

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The inhibitory effects of a cyclooxygenase inhibitor, indomethacin, and a thromboxane (TX) A2receptor antagonist, S-145, on thrombin-stimulated rabbit platelet responses were examined for their contribution to the TXA-mediated amplification mechanism. Although thrombin (0.01–0.3 U/ml) induced the dosedependent aggregation and release of TXB2from washed rabbit platelets, indomethacin (30μM) inhibited only the aggregation induced by a threshold dose of thrombin, even though it completely inhibited the formation of TXB2. Indomethacin inhibited both the secretion of ATP and the elevation of the intracellular concentration of Ca2+([Ca2+]i) induced by all doses of thrombin used and induced a considerable rightward shift of the dose-response curves. S-145 also significantly inhibited the elevation of [Ca2+]i. Thrombin caused rapid accumulation of [3H]-InsP3or of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. This accumulation was also inhibited by indomethacin to about 70% of the control level. STA2, a stable analogue of TXA2, and arachidonic acid caused accumulation of InsP, and that induced by the latter was completely inhibited by indomethacin (1μM). Thrombin-induced aggregation peaked at a lower level of [Ca2+]ithan that required for the secretion of ATP. The apparent contribution of TXA2to aggregation therefore appears to be restricted to that induced by lower doses of thrombin. These results suggest that in thrombin-stimulated rabbit platelets, activation of phospholipase C, which is regulated by TXA2receptors, is a primary target of the TXA2-mediated amplification mechanism. Through its effect on the accumulation of Ins(1,4,5)P3, this amplification mechanism may contribute to about 25–30% of the elevation of (Ca2+]i, in addition to the thrombin receptor-mediated mechanism.

ISSN:0953-7104    

DOI:10.3109/09537109409006037

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Fibres of textured biomaterials (BM) enable platelets to adhere with formation of focal contacts. The contact structure and the reaction of the contact associated contractile cytoskeleton were studied using fibres of different flexibility/mobility: butyl-S-Sepharose (S), Polysulfone (PS) and Polyurethane (PU). Ultrastructural and immunocytochemical investigations were carried out to obtain information on the influence of tension on (1) the structure of the focal contacts; (2) the constricting cytoskeleton known to retract adherent collagen or fibrin fibres and (3) the cable-like bundles of actomyosin as observed in the clot. Fibre network from S spheres and 0.3 mm thick frozen sections of PS or PU were incubated with citrated PRP or with washed platelets at 37 C for 6 to 30 min while stirring for contact or activation with ADP or thrombin. Flexible fibres of the BM were found in deep invaginations of the plasmalemma associated with the constricting cytoskeleton. Focal contacts (mediated by fibrinogen as shown immunocytochemically) with fibres which were fixed in the texture or inflexible (PU) induce cable-like bundles of micofilaments containing myosin. These bundles pass across the cytoplasm and connect the contacts with the fibres or with other platelets, as demonstrated by computer-assisted 3-dimensional reconstruction. The model used indicates that retraction is possible as long as fibres are mobile and that cable-like bundles occur when the locomotion of platelets is blocked by immobile fibres. The interaction of platelets with textured BM reflects the situation during collagen or fibrin condensation. The findings may contribute to an understanding of platelet reactions on textured surfaces in grafts.

ISSN:0953-7104    

DOI:10.3109/09537109409006038

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Platelet concentrates were stored at room temperature and the reactivity of platelets to aggregating agents was studied at temperatures between 23 and 39°C. Fresh platelets showed increased reactivity at higher temperatures. When stored platelets were considered, maximal aggregation was not statistically different when compared with fresh platelets in the temperature range of 23–29°C (5μM ADP). In addition, platelets stored either in Terumo or Baxter (PL 146 and PL 732) plastic bags at room temperature, showed an increased ADP-induced aggregation (10μM) when studied at room temperature compared to 37°C. This pattern was confirmed by the difference in released ATP during aggregation. Collagen, although not resulting in detectable aggregation at 25°C, caused a similar release of ATP as that observed at 37°C.Since the observed differences in platelet reactivity seem to be similar using different types of plastic bags, the increased aggregation observed at room temperature is unlikely to be due to a special effect of a storage bag. Since the recovery of ADP aggregability is better at room temperature than at 37°C, ADP-induced aggregation determined at room temperature might be a better index of the clinical results expected when using stored platelets.

ISSN:0953-7104    

DOI:10.3109/09537109409006039

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Adhesion molecules such as P-selectin (CD 62), glycoprotein (CP) 53 (CD63) and thrombospondin play a decisive role in the thrombogenic transformation of platelets. Here we present evidence obtained using flow cytometric analysis that the PGI2-mimetics iloprost and taprostene, and an NO (EDRF)donor (SIN-1) are able to inhibit the expression of P-selectin, GP 53 and thrombospondin on human platelets activated by submaximal concentrations of thrombin. Since the half-maximal concentrations for inhibition of antigen expression (0.15 nM for iloprost, 3.0–5.3 nM for taprostene) are much lower than for activation of adenylate cyclase (1.4 nM for iloprost and 29.4 nM for taprostene) our data suggest that the occupation of a small number of PGI2-receptors is sufficient to inhibit the thrombogenic transformation and that spare PGI2-receptors are present on human platelets.In diabetes, the EC50for inhibition of expression of platelet antigens is shifted to higher concentrations suggesting that platelets from type 1 diabetic patients are partly resistant to PGI2. Since the dose dependent increase in c-AMP by iloprost is not changed and intraplatelet c-AMP is elevated in platelets of diabetic patients, we assume that steps in the activation cascade subsequent to activation of adenylate cyclase are disturbed in diabetes.

ISSN:0953-7104    

DOI:10.3109/09537109409006040

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Serological and clinical data were collected in 59 cases of suspected neonatal alloimmune thrombocytopenia (NAIT) and in 24 thrombocytopenic newborn of mothers with presumed autoimmune thrombocytopenic purpura (AITP). In the NAIT group, the anti-HPA-la (anti-Zwa, anti-PlAI) and the anti-HPA-5b (anti-Bra) account for about 68% and 11% respectively of the serologically proven cases. The findings of a high frequency (45%) of maternal anti-HLA antibodies in the HPA-la positive group, suggests an association of NAIT and maternal HLA alloimmunisation. In the AITP group, 83% of the women had increased amounts of platelet-associated IgG (PAIgG) with a predominance of IgGl and IgG3. In one third of the cases, maternal circulating autoantibodies, mainly against GPIIb/IIIa and GPIb/IX, were found. The finding of circulating platelet autoantibodies in 16% of the HPA-la positive non-thrombocytopenic mothers makes it possible that these women are suffering from compensated AITP. In the AITP group, neither maternal platelet count, maternal increased amounts of PAIgG, the pattern of PAIgG subclasses, circulating autoantibodies, the specificity of the autoantibodies nor maternal splenectomy could be used to predict the severity of the neonatal thrombocytopenia. In the NAIT group, intracerebral hemorrhage occured in 10% and in the AITP group in 4%.

ISSN:0953-7104    

DOI:10.3109/09537109409006041

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Aspirin and Other Salicylates. Editors: John R. Vane and Regina M. Botting, Chapman&Hall, London 1992. 613 pages. Price£85

ISSN:0953-7104    

DOI:10.3109/09537109409006042

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor