TUNEL-positive cardiomyocytes and genomic DNA electrophoresis during global warm or cold I/R. (A–F) TUNEL staining of ischemia/reperfused rat hearts (original magnification ×400). TUNEL-positive cardiomyocytes were increased from 2 to 8 and 24 hr after warm I/R (A, B, and C) but not after global cold I/R (D, E, and F). (G) Time course of the percentage of TUNEL-positive cardiomyocytes. Open and solid bars indicate the cold and warm I/R groups, respectively. Mean±SE for 6 rats. *P <0.005 vs. corresponding cold I/R group. †P <0.05 vs. 0, 2, 4, 8, and 48 hr warm I/R groups. (H) Genomic DNA electrophoresis on a 1.8 agarose gel. Cold ischemia followed by 24 hr of reperfusion did not induce visible DNA ladders. However, DNA ladders were clearly detected at 8 and 24 hr after reperfusion in the warm I/R group. M indicates a 100 base pair ladder. Data are representative of three experiments.