Continuous confocal live-cell imaging of Fluo-4–loaded Jurkat cells. Cells were exposed to 5 Gy x rays, and image acquisition (one every 5 s) started 5 min after irradiation. The first responsive cell shows blinking 5 min after start of the recording. Over time, ∼65% of the cells in the optical field showed characteristic Ca2+cyt oscillations. Time in h:min.
