Figure 4. Dose response of nuclear cyclin D1 in WI-38 cells. Detergent-insoluble fractions of cell lysates were prepared 24 h after the last radiation exposure, and western blotting was performed. Levels of nuclear cyclin D1 were determined for 31FR-WI-38 cells exposed to indicated FR. Cyclin D1 levels were normalized to actin, β, and values are expressed relative to un-irradiated controls (0 FR). Data are means and standard deviations for 4 experiments using independent samples.