Figure 8.
Focus counting analysis in human blood lymphocytes. Panel A shows correlation of manual and automatic focus counting. Each data point represents an average for a group of images for either one particular radiation dose for a given donor, or one particular fixation time. Images were obtained from irradiated blood from 4 donors: 0650550 - circles, 0650565 - squares, 0650595 - triangles, 0650711 - inverted triangles. Blood from donors 0650550, 0650565, 0650595 was irradiated with doses 0.02, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, and 1.5 Gy, and lymphocytes were fixed 30 min after irradiation. Blood from donor 0650711 was irradiated with 0.6 Gy, and lymphocytes were fixed 0.5, 1, 2, 4 and 8 hrs after irradiation. Two-parameter linear regression analysis resulted in the following values: slope = 1.02 ± 0.03, intercept = 0.14 ± 0.21. Intercept is not different significantly from 0. The correlation coefficient R2 = 0.973 (P<0.0001 for the slope). Panel B shows radiation dose response of γ-H2AX focus induction in human blood lymphocytes 30 min after irradiation for 3 donors 06500550 (circles, solid line), 0650565 (triangles, dash line) and 0650595 (squares, dot line). Symbols represent results of automatic counting; lines are generated by the linear regression analysis. Values for intercept are 0.71 ± 20, 0.84 ± 39 and 0.88 ± 32 for 0650550, 0650565 and 0650595 donors respectively, indicating statistically significant level of background γ-H2AX foci based on the linear model. Values for γ-H2AX focus yield are 11.0 ± 0.3, 9.5 ± 0.6 and 12.0 ± 0.5 Gy−1 for donors as indicated above. Panel C shows kinetics of γ-H2AX after irradiation with 0.6 Gy (donor 0650711).