Ischemia-reperfusion induces apoptosis.

Following reperfusion, muscle tissue subjected to varying periods of ischemia as a result of aortic cross-clamping followed by 3 hours of reperfusion was sectioned and stained with the TUNEL technique. Methyl green was used as a nuclear counterstain. Original magnification, × 200. (A) Minimally injured tissue with 45 minutes of ischemia (DMSO treatment) shows TUNEL positivity only in vascular endothelial cells (arrow). (B) More extensive tissue injury with 90 minutes of ischemia (DMSO treatment) with TUNEL-positive nuclei in endothelial cells (arrow) and skeletal muscle fiber cells (arrow head). (C) Pretreatment with z-VAD resulted in only a few TUNEL-positive cells in capillary endothelium of the muscle tissue subjected to 90 minutes of ischemia (arrow).