Fig. 4.
Effects of SPP andN,N-dimethylsphingosine on apoptosis in PC12 cells.A, PC12 cells were prelabeled with [3H]thymidine and then treated in serum-free medium for 4 hr without or with NGF (100 ng/ml), SPP (5 μm), dimethylsphingosine (DMS, 10 μm), or the indicated combinations, and DNA fragmentation was determined. Data are expressed as percent DNA fragmentation and are the mean ± SD of triplicate cultures. Similar results were obtained in three independent experiments. PC12 cells were incubated for 24 hr in serum-free medium without (B) or with 5 μm SPP (C) or 100 ng/ml NGF (D) and then stained with the DNA-specific fluorochrome bisbenzimide.