Differentiation of mouse NS cells is not associated with increased cell death. Mouse NS cells at different days of differentiation were fixed and processed for either morphological evaluation of apoptosis or TUNEL assay, or were stained with Annexin-V-APC/PI. A) Evaluation of apoptosis by Hoechst staining and TUNEL assay. Representative images from at least three independent experiments. Arrows indicate apoptotic cells. B) Representative FACS diagrams depicting the percentages of either dying (Annexin+/PI-) or dead (Annexin+/PI+) cells. C) Quantitation of the data depicted in FACS diagrams. Results are mean ± SEM. This experiment was repeated at least three times, yielding comparable results. Scale bar: 10 μm. d, days.