Table 1.

Effects of maytansine, S-methyl-DM1, and S-methyl-DM4 on microtubule dynamic instability

Microtubule dynamic parametersControlMaytansine (0.1 μmol/L)Percent changeS-methyl-DM1 (0.1 μmol/L)Percent changeS-methyl-DM4 (0.1 μmol/L)Percent change
Growth rate (μm/min)1.7 ± 0.21.1 ± 0.2*35 (−)1.3 ± 0.424 (−)1.3 ± 0.324 (−)
Shortening rate (μm/min)8.9 ± 0.85.8 ± 0.5*35 (−)2.7 ± 0.970 (−)3.9 ± 0.456 (−)
Percent time growing23.2243.4 (+)7.370 (−)15.234 (−)
Percent time shortening14.81126 (−)5.464 (−)4.272 (−)
Percent time attenuated62655 (+)87.441 (+)80.630 (+)
Growing length (μm/event)1.9 ± 0.21.2 ± 0.137 (−)1 ± 0.1*47 (−)1.6 ± 0.116 (−)
Shortening length (μm/event)3 ± 0.21.8 ± 0.940 (−)1.2 ± 0.260 (−)1.2 ± 0.260 (−)
Catastrophe frequency (per minute)0.300.2130 (−)0.0390 (−)0.0390 (−)
Rescue frequency (per min)1.000.6040 (−)0.5644 (−)0.5050 (−)
Dynamicity1.30.7245 (−)0.2184 (−)0.3573 (−)

NOTE: Tubulin was polymerized to steady state with axoneme seeds in the presence of 100 nmol/L maytansinoid and the dynamic instability parameters were determined (Materials and Methods). Fifteen to 25 microtubules were measured for each drug concentration. Data are mean ± SEM.

  • *P < 0.05, versus (Students' t test).

  • P < 0.01, versus control (Students' t test).

  • P < 0.001, versus control (Students' t test).