Figure 3

Apoptosis in irradiated cells growing as monolayer was negligible. NP18 cells growing on glass coverslip were irradiated with 45 Gy and incubated for 4 hours. Shown are five microscopic pictures (original magnification, ×1000): TO-PRO-3 stained nuclei (red), fluorescence from caspase-3-activated cells (green), and merged pictures. In sharp contrast with Figure 2B, apoptosis was negligible. Despite irradiation, the typical nuclear fragmentation and chromatin condensation associated with apoptosis was minimal, but consistent with the specific activation of caspase-3.