Figure 4. The impact of dose on stem cells numbers. Eleven HMEC strains derived from individuals of various ages were exposed to a LD and HD of Cs and Ti ion. Roughly equitoxic doses of Cs and Ti were used for exposures (LD-CS = 0.12 Gy; HD-CS = 0.8 Gy; LD-Ti = 0.05 Gy; HD-Ti = 0.5 Gy). Cells were passaged and processed 9 days after radiation exposure. S/P cells were assessed based on ALDH+ signal using flow cytometry. DAPI negative cells defined the live population. Doublets were eliminated and the ALDH+ signal was assessed with reference to the DEAB control sample. The proportion of ALDH+ cells were plotted relative to the unexposed sham radiated control. Data are based on two independent experiments for high and low dose. Blue and red symbols represent strains exposed to Cs and Ti ion respectively. Empty symbols represent low dose and solid symbols high dose exposures.