Fig. 3. Nuclear changes in apoptotic cells. (A) Following exposure to 50 µM menadione for 6 hours, cells were fixed in 4% paraformaldehyde for 5 minutes and put on a coverslip with DAPI-containing mounting media and observed under epi-flurorescent microscopy. Bar, 10 µm. (B) 10 µg genomic DNA from U937 and ARPE-19 cells exposed to 50 µM menadione for 6 hours was separated either by 1.0% agarose gel electrophoresis (left) or pulse field gel electrophoresis (right) and visualized under UV illuminescence.