a, Representative movie frames of a normal mitosis. Arrows, nuclear envelope break down and cytokinesis. Scale Bar, 10 µm. b, Mitotic duration of individual indicated cells (upper panel). Mean mitotic duration ± s.e.m. (lower panel) (Man-Whitney test, compared to IMR-90 E6E7 PD36). c, Growth curves of indicated IMR-90 derivatives. d, Mitotic duration of indicated derivatives as in b. Results were reproduced independently at least twice. e, f, Mitotic duration of IMR-90 E6E7 (e) or p53dd (f) cells expressing hTert as in b. Cells were infected at indicated PD. *P<0.05, **P<0.005, ***P<0.0001. Mann-Whitney test.