Percentage of 5 min intervals neurites engaged in | Growth rate (μm/hr) | |||
---|---|---|---|---|
Growth | Quiescence | Retraction | ||
Control | ||||
Main axons (18) | 49 | 48 | 3 | 52 ± 10 (15) |
Collaterals | ||||
15–40 μm (29) | 8 | 87 | 5 | 10 ± 2 (10) |
>40 μm (15) | 25 | 66 | 9 | 16 ± 5 (8) |
Taxol (7 nm) | ||||
Main axons (16) | 29 | 66 | 5 | 27 ± 6 (12)2-a |
Collaterals | ||||
>40 μm (16) | 20 | 73 | 7 | 21 ± 4 (8) |
NOC (83 nm) | ||||
Main axons (18) | 34 | 62 | 4 | 24 ± 3 (10)2-b |
Collaterals | ||||
>40 μm (14) | 18 | 74 | 8 | 15 ± 3 (8) |
Numbers in parentheses in the left-most column refer to the number of processes sampled. Because DMSO treatment was not found to alter any of the measurements, data were pooled and are referred to as control. The total number of 5 min intervals scored in each condition to obtain the percentage of time spent in growth, retraction, or quiescence ranged from 136 to 227. Numbers in parentheses in the right-most column refer to the number of processes within each respective group that underwent growth during the observation period and were used to obtain mean growth rates. One to two axons in control, taxol-, and nocodazole-treated cultures, respectively, underwent continued retraction that was initiated soon after the start of the observation period and were omitted from the measurements. Growth rates of axon or collaterals raised in taxol or nocodazole were compared with control rates using the Welch t test, one-tailed. No statistically significant differences were observed for growth rates of drug-treated collaterals relative to control collaterals, or between control collateral length classes. The χ2 analysis was used to compare the distributions of time collaterals spent growing, retracting, or being quiescent. Statistically significant differences were obtained when comparing control collaterals in the two length classes (p < 0.0001), and between the control and taxol- (p < 0.001) or nocodazole-treated axons (p < 0.01) but not taxol- or nocodazole-treated collaterals with length-matched controls.
↵F2-a p < 0.01.
↵F2-b p < 0.05.