Fig. 5. Adaptive strengthening of bead-integrin-cytoskeleton linkages induced by prolonged static force. (A) Schematic of experimental design. Brief (3 second) force pulses (black bars) were applied to surface-bound RGD-beads before and after static forces that were sustained for different times (grey bar) in order to determine if prolonged forces induce stable cell strengthening. (B) Prolonged force (250 pN) of 
15 seconds duration induced strengthening of RGD-bead adhesions. Relative bead displacements represent displacements produced by the second 3-second force pulse divided by that induced by the first force pulse (white bar) (*P<0.05; grey bars indicate no significant difference compared with pre-force levels). (C) Strengthening of RGD-bead adhesions in response to application of force (130 or 350 pN) prolonged for 2 minutes in the absence (black bars) or presence (white bars) of BDM, Y27632