Use of High Dose Rate Electron Beams to Study Cellular Repair Mechanisms

Repair of sublethal damage produced by ionizing radiation is an important factor influencing cellular survival. This is particularly so when low dose rates, as encountered in environmental exposures, are involved. Since repair processes may have characteristic times ranging from nanoseconds to hours, conventional radiation sources are not capable of giving the range of dose rates needed for a systematic investigation. A 2 MV electrostatic accelerator has been modified to generate an electron beam to satisfy this requirement. This accelerator and associated electronic controls have been used to demonstrate that the repair process responsible for the altered survival observed after split-dose irradiations is the same as that responsible for the shoulder of the survival curve for Chlamydomonas reinhardi. Furthermore, it has made possible the identification and measurement of the rates of two repair processes which function concurrently in these cells.