Dose and time kinetics of γH2AX foci detection in EA.hy926 EC following low-dose X-irradiation. EA.hy926 EC were plated onto coverslips and grown to confluence. At 4 h before irradiation with the doses indicated, ECs were stimulated with TNF-α (20 ng/ml), while mock-treated cells served as a control. At 1 h (B), 4 h (C) and 24 h (D) post irradiation, cells were fixed, stained for γH2AX, DAPI and CENP-F (A) and data of a total of 80 nuclei (40 G1 and 40 S/G2) were combined for a single data point. Data represent means ± SD from at least three independent experiments. Asterisks indicate significant differences (p < 0.05) vs. 0.3 Gy and 0.7 Gy irradiated ECs.