Fig. 4.

Effect of Ib on entry of propidium iodide (PI), DNA fragmentation, and ultrastructural change. (A) Nuclear DNA from untreated A431 cells (lane 0) and cells exposed to Ib (250 ng/ml) at 37°C for 1 to 4 h (lanes 1, 2, and 4) was analyzed by agarose gel electrophoresis. As a positive control, A431 cells were treated with 10 nM staurosporine (Stau.) for 24 h. (B) Cells were incubated with Ib (250 ng/ml) and PI (5 μg/ml) at 37°C for the periods indicated. Control cells (100%) were treated at 37°C for 30 min with 0.2% Triton X-100. Data are means ± standard deviations for four independent experiments. Symbols: ●, A431; ○, MDCK. (C) Ultrastructural changes caused by Ib. A431 cells were incubated without or with Ib (250 ng/ml) at 37°C for 30 min. Cells were then processed for transmission electron microscopy as described in Materials and Methods. Bar, 10 μm.