Table 1.

Axon volume and microtubule mass

Treatment	Axon diameter (μm) (±SEM)	Axon length (μm) (±SEM), # cells	Axon volume1_a(μm3)	Corrected axon volume1_b(μm3)	Microtubules per cross-section (±SEM), # cross-section profiles	Microtubules mass1_c	Microtubule profile density1_d
Control (24 hr)	0.51 ± 0.07  n = 14	1024 ± 208 n =  8	209	459	22 ± 1.6 n = 41	22,528	110
Control (9 hr)	0.58 ± 0.06  n = 16	4801_e	127	278	27 ± 4.4 n = 16	12,960	104
165 nmnocodazole	1.01 ± 0.16  n = 14	568 ± 124 n = 14	454	504	43 ± 3.9 n = 25	24,424	53
330 nm nocodazole	2.00 ± 0.16  n = 21	270 ± 49  n = 14	848	511	66 ± 5.9 n = 21	17,820	21

^F1_aAxon volume was calculated fromv = πr² × l, wherer = radius and l = axon length (total outgrowth from dissociated cells).

^F1_bTwo adjustments for volume were made to correct for deviations from a perfect cylinder: (1) the frequency, length, and diameter of periodic varicosities were measured and then incorporated into the calculations (see Materials and Methods); (2) increasing nocodazole concentrations resulted in axons that appeared as flattened cylinders. Calculations were also adjusted for the flattening effect by assuming that the axon cross-section in the nocodazole-treated cultures was represented by an oval.

^F1_cMicrotubule mass was calculated by multiplying axon length (total outgrowth from dissociated neurons) by the average number of microtubules per axon cross-section.

^F1_dMicrotubule profile density refers to the density of cross-sectioned microtubules profiles per axonal cross-sectional area (μm²).

^F1_eIn this case, explant outgrowth from one explant was used instead of measuring the length of neurites from individual neurons.