Table I.
Dynamic parameters of individual microtubules nucleated by centrosomes in X. laevis and X. tropicalis extracts and rates of poleward flux
| X. laevis | X. tropicalis | t test | |
|---|---|---|---|
| n = 50 | n = 79 | ||
| Growth rate (μm/min) | 18.5; SD = 8.8 | 14.7; SD = 4.4 | 0.013 |
| Shrinkage rate (μm/min) | 21.8; SD = 9.3 | 17.6; SD = 5.0 | 0.19 |
| Catastrophe frequency (events/min) | 5.8; SD = 1.1 | 5.9; SD = 4.7 | 0.96 |
| Rescue frequency (events/min) | 3.0; SD = 2.6 | 4.3; SD = 4.9 | 0.44 |
| Average length (μm) | 5.7 | 6.3 | 0.42 |
| Flux rates (μm/min) | 1.79; SD = 0.33 | 2.25; SD = 0.25 | 0.31 |
Microtubule dynamics were measured from individual centrosomes in X. laevis and X. tropicalis CSF extracts. Dynamic parameters were computed using a custom algorithm. A t test was used to compute the significance of the differences. n denotes the number of individual microtubules measured for each extract system, taken from three different extracts. Average microtubule lengths were calculated according to Verde et al. (1992). Poleward flux rates were measured using time-lapse fluorescence speckle microscopy in 3 different extracts, with 5 spindles each (15 spindles total) for X. laevis and X. tropicalis.