Effect of matched increases in the concentration of plasma fibronectin present during formation of fibrin matrices and in the perfusate on platelet thrombus formation under shear conditions. (A) Fibronectin (FN), 0 to 600 μg/mL, was present during formation of fibronectin-fibrin clots. The same concentration of plasma fibronectin was included in the perfusate. After 5 minutes, perfusion at a wall shear rate of 1250 s^–1 coverslips were taken out of the chamber and washed. Microscopy was performed as described in Figure 1. Bar = 100 μm. (B) Thrombus volumes (□) and platelet numbers (○) were measured as described in Table 1. Values represent the mean ± SD (n = 4 experiments). The values at fibronectin concentrations of 400 and 600 μg/mL were significantly different from values at 100 μg/mL (P < .001 in the Dunnett test after ANOVA).