Thrombus formation defect in E2-treated mice. DiOC6-labeled platelets in whole blood were perfused over a collagen-coated surface at a wall shear rate of 1500 seconds⁻¹ for 2 minutes. (A) Thrombus formation was visualized with a 40× long working distance objective in real time and then imaged by transmitted light microscopy (scale bar: 20 μm). (B) Representative phase contrast images taken at the end of the experiment. (C) Surface area covered by thrombi and thrombus volume were measured at 2 surface locations. Results are mean values ± SEM from 4 independent experiments. ***Significant difference (P < .001).