FIG. 4.

(A) Agarose gel electrophoresis of DNA extracted from WEHI 231 cells treated with butyric acid for 16 h. Lanes: M, molecular weight markers (HaeIII-digested φX174 DNA); 1, untreated control cells; 2 to 6, cells treated with 5, 2.5, 1.25, 0.62, and 0.31 mM butyric acid. (B) Fluorescence microscopy appearance of WEHI 231 cells untreated or treated with butyric acid for 16 h and stained with Hoechst 33258. Normal nuclear morphology is observed in untreated cells; in contrast, small and condensed nuclei with typical apoptotic morphology are observed in treated cells.