Effects of Sema3A on thrombin-induced increase of intracellular Ca²⁺concentrations. Fluo-3–labeled platelets were incubated with 20 μg/mL Sema3A/Fc or hIgG. After the determination for about 10 seconds of baseline fluo-3 fluorescence from the platelet population, cell aspiration into the flow cytometry was briefly paused, and 1:10 volume of 5 U/mL thrombin (Thr) was added. The acquisition was then resumed, and changes in log fluorescence versus time were recorded (top panels). For each plot, rectangular analysis regions were defined over the time axis, and mean fluorescence intensity was calculated. Mean ± SE of 3 independent experiments was plotted in bottom panel. Bold and thin lines represent Sema3A/Fc and hIgG, respectively.