DNA damage and repair in several different cell systems. HeLa S3 cells (A), Jurkat cells (B) and human PBMC (C) were damaged with 2.3 Gy of X-irradiation (P1). To allow repair, cells were incubated at 37°C for 40 min (R). T and P0 samples were controls. In all cases the fluorescence signal of the P1 samples was lower that the control value P0, and those of the R values higher than the damaged samples P1. Error bars represent SDs from 8 replicates.