Fig. 5. Tension applied via stretching of the growth substrate beyond the cell front induces microtubule growth at the cell periphery. The figure shows a B 16 melanoma cell that was transfected with GFP-tubulin and plated onto a flexible, polyacrylamide substrate impregnated with rhodamine-tagged fluorescent beads. The upper left and right panels (boxed insets enlarged) show video frames of the cell before tension application. The lower frames show the corresponding regions after tension application [at 3 minutes 30 second (3'40'')] by a needle applied to the substrate around 20 µm beyond the cell edge. The direction and magnitude of tension is indicated by the shift of fluorescent beads (middle panel, left), which corresponds to the smaller boxes regions in the lower, left panels. One example from 19 cells is shown.