(A) Platelets were exposed repeatedly to 15 dyne/cm2 average shear stress for 80 s, followed by subsequent 10 min exposure to 0.5 dyne/cm2 in the HSD, with samples assayed for PAS at regular intervals. For the 2, 4, and 10 passage experiments, an increasing trend is observed for both (B) initial PAS and (C) subsequent post-high shear PAR. However, the 6 and 8 passage experiments showed the highest initial PAS, but negative post-high shear PAR.