Figure 6.

Bright-field microscopy images depicting the metabolic activity of HCT116p53−/− cultures: before (A); and after (B–D) 8-Gy irradiation. Metabolic activity was measured by the ability of the cells to convert the yellow MTT to its purple formazan metabolite, appearing as dark granules and crystals; As a negative control, cells in some dishes were first treated with methanol to inhibit their metabolic activity, and then incubated with MTT (C). All images were acquired at the same magnification.