Effects of heavy ions on rabbit tissues: analysis of low levels of DNA damage in retinal photoreceptor cells.

When suitable precautions are taken, sedimentation of DNA through reoriented alkaline sucrose gradients in zonal rotors can be used to determine small amounts of DNA damage in mammalian cells without resorting to radioactive precursors. Hence, the method is especially useful for studying the efficacies of DNA repair mechanisms in the neurons of the central nervous system (CNS) and the accumulation of DNA damage in the ageing CNS. Here we describe the technique as it has been used to examine the DNA damage occurring in the photoreceptor cells of the retina of the New Zealand white rabbit during the course of natural ageing or after exposure to heavy ions. This article is an integral part of a series of reports of the latter studies (Lett et al. 1980, Keng and Lett 1981, Cox et al. 1981, 1982, Keng et al. 1982). With the same analytical technique, very low levels of radioactive DNA precursors can be used to advantage in investigations of proliferating cells.