Effects of Sema3A on platelet adhesion and spreading. (A) Washed platelets were incubated with 20 μg/mL Sema3A/Fc (bold line) or hIgG (thin solid line), or PBS (dashed line), and then placed on the various concentrations of immobilized fibrinogen for one hour. After washing with PBS to remove nonadherent platelets, adhered platelets were quantified by acid phosphatase method. Mean and SE of percent adhesion of 3 independent experiments was plotted. *P < .05. (B) Sema3A-treated platelets (ii,iv) or hIgG-treated platelets (i,iii) were placed on fibrinogen-coated (i-ii) or nontreated (iii-iv) glass coverslips. Adhered platelets were stained with TRICT (tetramethylrhodamine-5(and 6)-isothiocyanate)–phalloidin. Images were captured with a CCD camera (DP-70; Olympus) mounted on an Olympus AX-80 fluorescence microscope equipped with a 100 ×/1.30 oil immersion objective lens. Images were acquired with Olympus DP Controller software and processed with Adobe Photoshop Elements 2.0 (Adobe Systems, San Jose, CA). Original magnification × 1000, and bar in panel Bi represents 10 μM.