Figure 1: Radiation-induced foci in tissues from repair-proficient mice (C57BL/6) exposed to fractionated low-dose radiation. Immunofluorescent staining for 53BP1 (green) in DAPI-stained nuclei of bronchiolar and alveolar cells (lung), cardiomyocytes (heart), and cortical neurons (brain) analyzed 72 h after exposure to 50×10 mGy, compared to non-irradiated control tissues. Original magnification, 600×.