Filopodia and lamellipodia formation in platelets adhering to low- and high-density fibrinogen. Time-lapse TIR-FM imaging of platelets adhering to low- or high-density fibrinogen in the presence of Alexa 488-7H2Fab was recorded for 30 minutes after the addition of platelets into the fibrinogen-coated wells (Video S2). Individual platelets were analyzed for the appearance of new filopodia and onset of lamellipodia formation, counting the time they first appeared in the evanescent field (ie, within 200 nm of the substrate) as t = 0 seconds. The boxes in the figure represent the median and the 25th and 75th percentiles of the time to the onset and end of filopodia formation and the onset of lamellipodia formation. A total of 79 platelets were analyzed on low-density and 62 platelets on high-density fibrinogen from 2 independent experiments; *P = .03, **P = .04 low-density versus high-density fibrinogen.