Figure 2: Quantification of 53BP1 foci in tissues from repairproficient mice (C57BL/6) exposed to fractionated low-dose radiation. The numbers of 53BP1 foci per nucleus were counted 0.5, 24, and 72 h after the first dose fraction (1×) and 24 and 72 h after protracted low-dose radiation (10×, 20×, 30×, 40×, and 50× fractions over a time period of 2, 4, 6, 8, and 10 weeks) with 10 mGy. Data are presented as means from three different experiments ± standard error. (* denotes a statistically significant difference compared to non-irradiated control tissue).