Apoptotic cell index percentage (a and b) and mitotic cell index percentage (c and d) in small intestinal (a and c) and midcolonic (b and d) crypts of BALB/c (♦) and DBA/2 (▪) mice after a single injection of 100 mg/kg raltitrexed. Apoptotic cell index percentage (a and b) and mitotic cell index percentage (c and d) in small intestinal (a and c) and midcolonic (b and d) crypts of BALB/c (♦) and DBA/2 (▪) mice after a single injection of 100 mg/kg raltitrexed. Error bars represent standard deviations; four animals at each time point. ∗∗, significant at P < 0.05 by Student’s t test. The zero time points represent the levels of baseline apoptosis and mitosis in untreated control animals. D. Mark Pritchard et al. Clin Cancer Res 2000;6:4389-4395 ©2000 by American Association for Cancer Research