Research Article

Increase in Growth Cone Size Correlates with Decrease in Neurite Growth Rate

Figure 4

Large and small growth cones show different motile behavior. (a) DIC time-lapse imaging of a large, fan-shaped growth cone on the left revealed minimal net advancement during 3 h, whereas the small growth cone on the right translocated over a distance of 9 μm during the same time period. The C domain boundary is marked with a black dotted line. Note the splitting of C domain at the 50 h time point. (b) DIC time series of a small growth cone that showed significant translocation within 3 h. P domain protrusion is followed by advancement of the C domain (boundary marked with red dotted line). (c) Angle α between the direction of the C domain and the direction of growth cone advancement, measured at 10 min intervals. A diagram of C domain with −45 degrees relative to the direction of growth cone advance is shown as an inset. The small growth cone shown in (b) exhibited little fluctuation of the angle, whereas the large growth cone shown in (a) showed swaying of the C domain manifested by larger fluctuations of the angle (crossed circles) or splitting of the C domain (crossed and dotted circles). (d) Images of the same cultured bag cell neuron taken 40 h apart. Outline of growth cones at 30 h is overlaid to the image taken at 70 h. Note the formation of new neurites by branching from edges of P domain. Scale bars in (a) and (b): 10 μm; scale bar in (d): 60 μm.
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