Differential response of cells grown in light and dark to near-ultraviolet light

Abstract

WE have previously shown that near-ultraviolet and visible light (290–650 nm) kill mitotic and early S phase amoebae, whereas G₂ phase amoebae are quite resistant¹. Exposure of amoebae to near-ultraviolet light alone (290–400 nm) can have similar results (our unpublished data). We report here variations in sensitivity to near-ultraviolet irradiation of amoebae grown in 12 h light/12 h dark (hereafter referred to as light-grown cells) and those grown in complete darkness. We also show that in the dark-grown cells, as well as the S phase of the light-grown cells, the repair mechanism against the induced lethal damage might be lacking or non-functional.