Figure 5.

Improvement of the sensitivity by FdU supplement, longer incubation and acid extraction. Normal 48BR cells were cultured on coverslips, UVC irradiated (20 J/m²), followed by incubation with 10 μM EdU and 1 μM FdU (Sigma) for 4 h. Cells were then fixed as indicated in Figure 2. Acid extraction was performed using Bouin's fixative (Sigma) for 30 min, followed by extensive washing with PBS. Conjugation of fluorescent dye and detection of EdU signals were identical to the experiments in Figure 2. Bars represent frequencies of the fluorescence levels in indicated classes, with (black, identical to Figure 2A; blue, + FdU + 4-h incubation + acid extraction) or without (white, identical to Figure 2A; red, + FdU + 4-h incubation + acid extraction) UVC irradiation. Asterisks indicate the mean values of nuclear fluorescent intensities. Δ represents UDS differences with or without UVC irradiation.