The effects of fluid shear stress on talin1 mutant platelet thrombus formation ex vivo. Platelets in heparinized whole blood were labeled with anti–GPIX-Alexa488 and perfused over fibrillar collagen type I at low (100^–s) or high (1200^–s) shear rates. Adhesion of platelets was monitored continuously with a Nikon Eclipse TE300 inverted microscope (Nikon Instruments Inc., Melville, NY). (A-B) Representative images of platelet adhesion after 10 minutes of perfusion. (C-D) Image analysis. Platelet adhesion over collagen was quantified by measuring surface area coverage (percentage of total area) with Slidebook 5.0 software. Graphs show mean ± SEM (6 independent experiments). *P < .05, **P < .01, ***P < .001.