FIG. 5.

Mitotic arrest and adaptation occur in synchronized, nocodazole-treated NIH 3T3 cells. (A) Untreated NIH 3T3 cells. Cells were synchronized in low serum for 48 h and then released into high serum and monitored for 32 h. At each time point, cells were photographed (left panels) and then prepared for FACS analysis for DNA content (right panels). Time points are measured in hours postrelease from serum starvation. Cells were initially in G₀ (0 h), entered S phase at 14 h, and completed cell division by 26 h. (B) Nocodazole-treated NIH 3T3 cells. Cells were synchronized in low serum for 48 h and then released into high serum plus nocodazole and monitored for 32 h. Progression of cells through cell cycle was monitored as above. Cells exited G₀ and entered S phase by 14 h, remained arrested at mitosis through 26 h, and adapted by 32 h with a 4N DNA content.