Atypical cell death exhibited necrotic morphology by ultrastructural examination. BV173 cells were treated with DMSO (A), zVAD (B), imatinib (C, E), and zVAD + imatinib (D, F) for 12 hours (A-D) and 48 hours (E-F). Specimens were prepared for transmission electron microscopy as described in “Materials and methods.” Results are representative of 3 individual experiments. Original magnification, × 3000.