Fig. 2. Formation of the apoptotic microtubule array in mid-to-late apoptosis. To the right, the proportion of HeLa cells possessing microtubules at various stages of apoptosis, based on the morphological characteristics shown to the left (only cells completely lacking microtubules were scored as `negative'). Anisomycin-treated HeLa cells were stained for microtubules (green), cleaved PARP (red) and DAPI (blue). Early-apoptotic cells have cleaved PARP, but no evidence of chromatin condensation. In mid-apoptotic cells, cleaved PARP-positive nuclei are still intact but display evidence of chromatin condensation. By late apoptosis, chromatin is fragmented and dispersed. Bars, 10 µm.