Figure 1.
Response of traction forces to spontaneous tail retraction. (A–D) Phase contrast images of a migrating NIH 3T3 fibroblast, recorded at time points indicated at the upper right corner. Arrow in A indicates the direction of cell migration. (E–H) Color rendering of the corresponding magnitude of traction stress, which ranges from 9.15 × 102 dynes/cm2 (violet) to >8.50 × 105 dynes/cm2 (red). Note the increase in traction stress at the leading edge after retraction of the trailing edge. In addition, traction at the tail shifted to a region not affected by the retraction (G and H, arrowhead). (I) Average magnitude of traction stress (▪) and cell length (♦) during spontaneous tail retraction. Letters A–H mark the corresponding panels. Note that there was no loss of average traction force as the cell shortened to <50% of the original length. Bar, 20 μm.