Analyses of mitotic progression. (A) Phospho-histone H3 as a marker for mitotic progression. After exposure to 8-Cl-Ado (2 µM) for an indicated time, the cells were fixed with 70% ethanol; stained with anti - Ser10-phospho-H3 primary antibody, FITC-conjugated secondary antibody, and PI; and analyzed by FACScan. PI and FITC signals were measured in linear mode FL2-A and in logarithmic mode FL1-H, respectively. No primary antibody was used in the “blank”; dual staining of unexposed cells was used as control. The mitotic cells in red square are positive for phospho-H3. (B) Apoptosis analysis. Cell exposure and staining are the same as in (A). PI and FITC signals were recorded in logarithmic mode FL3-H and FL1-H, respectively. The cells in the left quadrants are apoptotic cells with <2N DNA content; that in the left upper quadrant are phospho-H3-positive. The values (%) represent means of two independent experiments. Data represent one of two independent experiments.