Kinetics of neutrophil shape change on HUVECs and L cells expressing E-selectin and ICAM-1. The membrane aspect ratio was quantitated as a measure of cell shape change for individual neutrophils immediately after arrest on IL-1β-activated HUVECs in the parallel-plate flow chamber (A) or L-E/I in the microfluid flow channel device (B-C) at 2 dyne/cm² shear stress. Neutrophils were preincubated with IC487475, BIRT, TS1/22, or vehicle, as indicated, then perfused in the respective flow chamber. On L-E/I, IL-8 was perfused into the microflow channel after neutrophils reached maximum adhesion, 3 minutes after injection. (A-B) Data are presented as the fraction of all arrested neutrophils in the field of view exhibiting a membrane aspect ratio greater than 1.4, a value deemed to be a threshold in membrane skewness based on empirical observations. Data represent the mean ± SEM from 4 separate experiments. (C) Images are 20 × phase contrast and are representative of adherent neutrophils on L-E/I under the conditions described in panel B.