Fig. 1. Visualization and quantification of stress-induced displacements of integrin-bound magnetic microbeads on the surface membrane of cultured cells. (A) Differential interference contrast view of an adherent endothelial cell with an arrow indicating a single RGD-coated magnetic bead (4.5 µm diameter) bound to integrins on its apical surface. Bar, 20 µm. (B) A series of bright-field images recorded over 9 seconds showing bead position before (top), during (middle) and after (bottom) application of a 3-second force (130 pN) pulse (arrow indicates direction of force). (C) Bead displacement (µm) as a function of time before, during and after the 3-second force pulse (thick black line), as determined using computerized image analysis.