Absence of a Fractionation Effect in Irradiated HeLa Cells

SummaryAerated and hypoxic HeLa cells have been exposed to single and split doses of radiation using pulses of fast electrons and conventional X-radiation. With aerated cells the single dose survival curves exhibited a shoulder with both types of radiation, before becoming exponential, but no fractionation effect was observed in the experiments with fast electrons, although one was found with X-rays. For cells under conditions of extreme hypoxia the single-dose survival curves were exponential both with electron pulses and with X-rays, and split-dose experiments showed no fractionation effect.