The introduction includes a review of the evidence which links exposure to the ultraviolet component of sunlight with the induction of skin cancers in humans and of the use of model cellular systems to study the induction and repair of damage in cells induced by far, mid and near ultraviolet radiations. Particular emphasis is placed on the use of human cell strains cultured from individuals with rare genetic disorders involving characterised or putative DNA repair defects, associated with an increased incidence of malignant disease. The experimental work is in three parts. The first is concerned with the characterisation of the responses of normal human skin fibroblasts to inactivation by monochromatic wavelengths in the far, mid and near regions of the ultraviolet spectrum. The second part of the experimental work takes the form of a comparative study of the responses of cell strains derived from individuals with the rare genetic disorder, ataxia-telangiectasia, and normal cells to inactivation by far, mid and near ultraviolet radiations. The final part of the experimental work comprises a study of the inactivation of normal and xeroderma pigmentosum human skin fibroblasts by seven monochromatic wavelengths between 254 nm and 365 nm. From these data action spectra have been determined for the inactivation of the two cell strains. The data obtained in each section have been discussed in the context of current concepts regarding the induction and repair of damage in cells by ultraviolet radiation and their biological consequences for the cell and by extrapolation for the whole organism.
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