Effect of concentrations of plasma fibronectin in the perfusate on platelet thrombus formation under shear conditions. (A) A suspension of platelets and red blood cells was premixed with plasma fibronectin (FN), 10 to 600 μg/mL (20-1200 nM), and perfused through a flow chamber opposed to a coverslip or culture dish coated with fibrin or fibronectin-fibrin for 5 minutes at a shear rate of 1250 s^–1. Coverslips were taken out of the chamber, and microscopy was performed as described in Figure 1. Bar = 100 μm. (B) Thrombus volumes (□, on fibrin or ▪ on fibronectin-fibrin) and platelet numbers (○, on fibrin or •, on fibronectin-fibrin) were measured as described in Table 1. Values represent the mean ± SD (n = 3-4 experiments).