Platelet aggregation and spreading. (A) Platelet aggregation results are presented with light transmission increasing from top to bottom along the y-axis and time along the x-axis. The agonists and concentrations used are indicated. A single agonist concentration aggregation tracing is provided for the 4 agonists that showed no difference between wild-type and caspase-12^–/– platelets. However, the lack of a difference between wild-type and caspase-12^–/– platelets was seen over a range of concentrations for convulxin (1-50 nM), collagen (0.2-20 μg/mL), U46619 (0.1-10 μM), and A23187 (1-10 μM). (B) Washed wild-type (top) and caspase-12^–/– (bottom) platelets were allowed to spread on BSA-coated (left) or fibrinogen-coated (right) glass coverslips. Images were obtained using differential interference contrast microscopy. Images are representative fields taken from 1 of 3 independent experiments that all yielded similar results.