Comparative Effects of60Co γ-rays and Neon and Helium Ions on Cycle Duration and Division Probability of EMT 6 Cells. A Time-lapse Cinematography Study

Abstract

Exponentially growing cultures of EMT 6 cells were irradiated in vitro with neon ions, helium ions or ⁶⁰Co γ-rays. Time-lapse cinematography allowed the determination, for individual cells, of cycle duration, success of the mitotic division and the age of the cell at the moment of irradiation. Irradiation induced a significant mitotic delay increasing proportionally with the delivered dose. Using mitotic delay as an endpoint, the r.b.e. for neon ions with respect to ⁶⁰Co γ-rays was 3·3 ± 0·2 while for helium ions it was 1·2 ± 0·1. Mitotic delay was greatest in those cells that had progressed furthest in their cycle at the time of irradiation. No significant mitotic delay was observed in the post-irradiation generation. Division probability was significantly reduced by irradiation both in the irradiated and in the post-irradiated generation. The reduction in division probability obtained with 3 Gy of neon ions was similar to that obtained after irradiation with 6 Gy of helium ions or ⁶⁰Co γ-rays.