Initial Changes in Cell Cycle Progression of Chinese Hamster V-79 Cells Induced by High-LET Charged Particles

Abstract

Asynchronous Chinese hamster V-79 cells were pulse-labeled with tritiated thymidine; then mitotic cells were sequentially colcemid-accumulated after helium ion irradiation. Similar fluences of charged particles depositing intracellularly 63, 90, 128, and 138 ke V/μm were delivered at the Radiological Research Accelerator Facility at the Brookhaven National Laboratory. Nuclear cross-sectional areas were log-normally distributed with a mean value of $110 \mu {\rm m}^{2}$. An initial decline and subsequent recovery in frequencies of mitotic cells was dose, and to a lesser extent, LET dependent. Cells in S phase at the time of irradiation were dose dependently delayed and then proceeded into mitosis at the same rate as control cells. This was not found for G2 phase cells, which were delayed and progressively bypassed by S phase cells and probably G1 cells as both dose and LET increased. The passage of one high LET particle anywhere through a nucleus probably induces some delay response, while particles depos...