The thesis opens with a review of the current knowledge of the mechanisms for the repair of radiation induced damage in bacteria and mammalian cells. The experimental work is presented in Chapters 2 to 6, each chapter beginning with an introduction and concluding with a discussion pertinent to the work described. Chapter 2 is concerned with the development of the culture of the mouse lymphoma cell lines L5178Y, JL, L5178YS and AIV, together with a soft agar suspension procedure for assessment of viability. The inactivation of the four cell lines, in two stages of growth, to gamma radiation and to 254 nm, 313 nm and 365 nm ultraviolet radiation has been compared in Chapter 3. The enhanced sensitivity of L5178YS cells to gamma radiation over that of the parent, L5178Y line is shown to UV radiation of all the wavelengths, as is the increased resistance exhibited by the AIV cell line. Chapter 4 describes a preliminary investigation into the mutagenic response of L5178Y cells to 254 nm and 313 nm radiation in two mutation assay systems, ouabain resistance and 6-thioguanine resistance. The sensitisation of 313 nm radiation inactivation and mutation of L5178Y cells by the sunscreen agent, para-amino benzoic acid PABA was investigated and the results are presented in Chapter 5. The sensitisation of 313 nm radiation inactivation was found to be dependent upon PABA concentration, and 0.2% PABA was found to enhance 313 nm radiation induced resistance to both ouabain and 5-thioguanine. A method of producing mutants of L5178Y cells which are sensitive to 254 nm radiation is described in Chapter 6. The isolates were characterised in terms of their sensitivity to 254 nm radiation, with respect to the time in culture after isolation. General conclusions concerning the use of L5178Y cell line for the elucidation of mammalian cell repair mechanisms are discussed in Chapter 7.
|Date of Award||1982|