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To investigate the existence of intracellular pools of membrane glycoproteins involved in platelet adhesive reactions, the authors have studied the distribution of glycoprotein (GP) Ib and IIb/IIIa by immunofluorescence and immunoelectron microscopy. Studies on whole cells and frozen thick sections revealed a rim pattern of fluorescence for GPIb and(More)
We have investigated the localization of thrombospondin (TSP), fibrinogen, fibronectin, and von Willebrand factor in human platelets by transmission electron microscopy of antibody-stained ultrathin frozen sections. In negatively stained thin sections, alpha granules were identified on the basis of their smooth, roughly spherical shape, size, single(More)
The transmembrane potential of human blood platelets suspended in plasma was investigated by studying the distribution of a radiolabeled permeant ion [14C] thiocyanate. The membrane potential of resting platelets was found to be -54.50 mV +/- 9.23 S.D. with a range of -39 to -76 mV (n = 27). The possibility that platelet activation alters membrane potential(More)
The author used immunofluorescence and digital image processing to investigate the dynamic distribution of GPIIb/IIIa in living platelets. Resting cells were incubated with AP-2, a complex-specific, monoclonal, anti-GPIIb/IIIa antibody. Examination of intact cells demonstrated a rim pattern for GPIIb/IIIa consistent with a surface localization.(More)
We have identified and purified a platelet integral membrane protein (140,000 mol wt), using the KC4 monoclonal antibody specific for activated platelets, that is internal in resting platelets but exposed on activated platelets (Hsu-Lin S.-C., C.L. Berman, B.C. Furie, D. August, and B. Furie, 1984, J. Biol. Chem. 259: 9121-9126.). The expression of the(More)
The distribution and transport in platelets of human coagulation Factor V was investigated by immunofluorescent and immunoelectron microscopy. In resting intact platelets, little surface staining was observed by immunofluorescence. In permeable resting cells, punctate staining similar to that reported for fibrinogen (Fbg), thrombospondin (TSP), fibronectin(More)
The distribution and transport of thrombospondin (TSP), fibrinogen (Fbg), fibronectin (Fn), and Factor VIII-related antigen (VIII:RAg) in resting and thrombin-stimulated platelets was investigated by immunofluorescence microscopy. In resting intact cells, little surface staining was seen for these proteins. In permeable resting cells, punctate staining(More)
Gel filtered human platelets contaminated with less than 0.02% of plasma protein S contained 490 ng of protein S antigen per 3 X 10(8) platelets, equivalent to 2.5% of protein S in whole blood. Three patients with heterozygous plasma protein S deficiency, a congenital disorder associated with venous thrombotic disease, had platelet protein S antigen levels(More)
Following platelet aggregation, integrin alpha(IIb)beta(3) becomes associated with the platelet cytoskeleton. The conserved NPLY sequence represents a potential beta-turn motif in the beta(3) cytoplasmic tail and has been suggested to mediate the interaction of beta(3) integrins with talin. In the present study, we performed a double mutation (N744Q/P745A)(More)
Several reports have indicated that the small G-protein Ras is not present immunologically in platelets. However, here we report the identification of Ras in platelets by immunoprecipitation with the Ras-specific monoclonal antibodies Y13-259 or Y13-238, followed by Western blotting. The presence of Ras was not due to contamination of samples with(More)