Fig. 5.
The filopodial retraction rate after cytochalasin D or elastase application accurately reflects in vivosubstrate adhesion. Average filopodial retraction during 60 min afterCD application was determined for four growth cones migrating along the low-affinity (less adhesive) femur epithelium (n = 60 filopodia) and for five growth cones within the high-affinity (more adhesive) trochanter epithelium (n = 87 filopodia). Similarly, average filopodial retraction during 60 min after elastase application was determined for three growth cones migrating along the femur epithelium (n = 66 filopodia) and for four growth cones within the trochanter epithelium (n = 69 filopodia). The average retraction rate was determined using both on- and off-axis filopodia. After either CD or elastase application, the average filopodial retraction rate for growth cones migrating along the less adhesive femur epithelium was significantly greater than the retraction rate for filopodia of growth cones interacting with the more adhesive trochanter segment epithelium (*p < 0.001; **p < 10−5). Error bars indicate SEM.