Use of 'nuclear monolayers' to identify factors influencing DNA double-strand breakage by X-rays

Nuclear monolayers, prepared by treatment of mammalian cells with non-ionic detergents, showed increased sensitivity to X-ray-induced DNA double-strand breakage (dsb), as compared with intact cells, due to a decrease in the low-dose 'shoulder'. The DNA dsb dose-response shoulder could be restored by irradiating nuclei in the presence of sulphydryl compounds. However, the ineffectiveness of glutathione, when used at near cellular levels, in restoring the shoulder, suggested a possible role for protein sulphydryls in the radiation response of intact cells.