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UBC Theses and Dissertations

The effect of misonidazole on cell survival at low doses of radiation Faddegon, Bruce Alan


Since Puck and Marcus first measured the effect of ionizing radiation on mammalian cell survival in 1956 the 'Puck plating' assay has been widely used as an endpoint for radiobiology experiments. The assay has contributed greatly to our knowledge of the processes involved when radiation interacts with cells, tissues, and whole animals. Generally cell survival experiments are carried out at fairly high doses of radiation (5-30 Gray) where cell survival drops below 50% of the survival of un-irradiated cells. Very little data has been accumulated at lower doses. Most of our knowledge in this region has been extrapolated from measurements made at higher doses. This is in part due to the difficulty of obtaining accurate results at higher survival levels, a problem primarily due to the difficulty in accurately determining the number of cells plated for the assay. This statistical uncertainty becomes important at survival levels greater than 50%. The uncertainty can be significantly reduced at these survival levels by accurately counting the number of cells plated, using a microscope, a procedure which is very time consuming when performed manually. A method of automating the procedure with a computer controlled motor driven microscope stage is described in this thesis. With the automated procedure the assay time is reduced by a factor of three. In this thesis the effect of the radiosensitizer misonidazole on cell survival was measured at radiation doses as low as one Gray. The results show that the drug is a poor radiosensitizer at low doses for the experimental system used. The clinical and radiobiological significance of these observations is discussed. This experiment exemplifies the value of measuring cell survival at low doses.

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