Fig. 1. Quantitative analysis of retrograde flow. (A) A sequence (13 second intervals) showing the movement of a peripherally located bead (top bead) towards the wt growth cone central zone. A second bead (bottom bead) in the central zone remains stationary. The line through the image is to aid detection of displacement. Beads are 1.5 µm in diameter. (B) A similar sequence (but at 6.5 second intervals) as in A, from a KO growth cone. Three beads are undergoing rearward movement (towards the bottom of the image) independently of a single growth cone. (C) Regression analysis of the steepest portion of a bead displacement versus time curve from a wt cone. The slope of the regression line was used as the maximum rate of bead displacement. (D) The same analysis as in C, but from a KO cone. Note that in general KO cones showed slightly more deviation from linearity (lower r² values) than wt. (E) Comparison of wt and KO maximum rates of bead displacement (n=10 for each). The difference was significant (t-test, P<0.01).