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. 2002 Jul 15;22(14):5982–5991. doi: 10.1523/JNEUROSCI.22-14-05982.2002

Fig. 7.

Fig. 7.

Axonal retraction induced by NOC-7 in the presence of taxol. A, Phase-contrast images of an axon before any treatment, after 30 min in taxol alone, and after 30 min of treatment with NOC-7 in the continued presence of taxol. Note that the taxol treatment did not prohibit axonal growth when applied without the NOC-7, nor did it prohibit axonal retraction after the NOC-7 was added.B, Microtubule immunofluorescence studies of three different axons: (1) a control axon, (2) an axon treated for 30 min with taxol alone, and (3) an axon treated with taxol for 30 min and then treated with both taxol and NOC-7 for an additional 30 min. Axons are shown in a quantitative pseudocolor scale in whichwhite is the most intense and black is the least intense. Note that the taxol-treated axon is brighter than the control axon. The taxol/NOC-7-treated axon is even brighter yet (per micrometer). C, Quantitative studies on fluorescence intensity, in arbitrary fluorescence units. Taxol treatment alone increased microtubule levels by ∼30% above control levels. Axons retracting in response to NOC-7 (in the continued presence of taxol) displayed a much higher yet fluorescence intensity per micrometer when calculated for length after retraction (Lr). However, when calculated for original length (Lo), the intensity per micrometer was indistinguishable from that of the axons treated with taxol alone. Thus, taxol treatment elevated total microtubule levels above controls, but this stimulation of microtubule assembly did not prohibit axonal retraction in response to NOC-7. The two-tailed Student'st test (∗p < 0.05) shows a significant difference between control axons and axons treated with taxol and a significant difference between control axons and axons treated with taxol followed by NOC-7. There was also a significant difference between axons exposed only to taxol and axons exposed to taxol followed by NOC-7, if calculations were performed using Lr. However, there was no significant difference between axons exposed only to taxol and axons exposed to taxol followed by NOC-7 if calculations were performed using Lo. Scale bars, 20 μm.