Inhibition of platelet spreading by incorporation of GPIIb peptide. (A) Confocal images of washed platelets allowed to spread on Fg for 45 minutes and stained for F-actin. Platelets treated with DMSO alone (control) spread fully. Platelets loaded with GPIIb cytoplasmic domain peptide (GPIIb Pep) showed long filopodia. Original magnification, × 600. (B) Dose-dependent inhibition of the number of fully spread platelets by GPIIb cytoplasmic peptide incorporation. Error bars indicate mean ± sem of at least 3 independent experiments.