Demonstration of MLO-Y4 cell apoptosis. (a) MLO-Y4 cells were incubated for 1 hour in vehicle or 50 nM DEVD-CHO. Subsequently, etoposide, TNF-α, or dexamethasone (Dex) were added at final concentrations of 50 μM, 1 nM, or 10^–6 M, respectively, and cells were incubated for an additional 6 hours. Dead cells were enumerated by trypan blue uptake, as described in Methods. Bars represent the mean ± SD of 3 independent measurements. Data were analyzed by 1-way ANOVA. *P < 0.05 versus control (Student Newman-Keuls method). (b) MLO-Y4 cells stably transduced with GFP were maintained for 6 hours in the presence of vehicle, 50 μM etoposide, 1 nM TNF-α, or 10^–6 M dexamethasone. Numbers indicate the percentage of cells undergoing apoptosis, as determined by evaluating the nuclear morphology of more than 500 cells in fields selected by systematic random sampling. Results are means ± SD of 3 independent experiments. Original magnification: ×400. Data were analyzed by 1-way ANOVA. *P < 0.05 versus control (Student Newman-Keuls method).