Effect of LFM-A13 on the latency and time course of thrombin-evoked actin reorganization. Human platelets were preincubated for 10 minutes in the presence of 10 μM LFM-A13 (○) or the vehicle (▪) and then rapidly mixed with 0.1 U/mL thrombin and incubated at 37°C for various time periods before mixing with formaldehyde (3% in PBS). Actin filament content was determined as described in “Material and methods.” Results are presented as the percentage of the F-actin content of nonstimulated cells (indicated by the dashed line) and expressed as mean ± SE of 6 runs made on cell preparations from 6 donors.