Fluorochrome bis-benzimide trihydrochloride (Hoechst-33258) was used to visualize the morphologic changes of nuclear chromatin in cells undergoing apoptosis as described . Briefly, following treatment BAECs including floating cells were harvested and fixed with 4% paraformaldehyde, washed with phosphate buffered saline (PBS) and stained with 50 μl of 24 μg/ml bis-benzimide trihydrochloride solution for 10 minutes. Apoptotic cells were quantified using an Axiovert S-100 Zeiss epifluorescent wide-field microscope equipped with a DAPI filter set. A minimum of 500 cells was examined per point.