Mild heating does not further increase the number of apoptotic cells in the intestine of mice after TBI. C57BL/6 mice were left untreated (NT) or treated with heat alone, 3 Gy TBI alone, or TBI followed 2 hours later with a 6-hour heat treatment. Intestine samples were collected 12 and 24 hours after treatment, and formalin-fixed, paraffin-embedded sections were stained for apoptosis. The number of apoptotic cells per field (when counted at 40×) was quantified at both 12 and 24 hours after treatment. Ten fields were counted per slide. Arrows indicate positive staining. n = 3 mice per group. Images are intestine samples from 12 hours after treatment (original magnification ×40).