Platelet adhesion studies. Platelet adhesion to Horm collagen was studied by flow chamber experiments. Heparinized blood from 3 unrelated Q43P carriers (carriers 1, 5, and 6) and 2 control subjects was perfused over collagen-coated slides at shear rates of 300 and 600 s^-1. (A) The figures represent images of a portion of the flow chamber for platelets derived from the indicated subjects and show that the platelet aggregates are smaller in the Q43P carriers. Original magnification, × 200. (B) Mean surface area coverage (percentage) of platelets at shear rates of 300 and 600 s^-1 after a perfusion time of 5 minutes for the indicated subjects. The statistical significance of observed differences between the 2 groups is indicated above each pair of bars. Error bars indicate mean ± standard deviation (SD).