Induction and Repair of DNA Strand Breaks in Cultured Mammalian Cells Following Fast Neutron Irradiation

Abstract
Induction and repair of DNA breaks following irradiation with NIRS cyclotron neutrons were studied in cultured mammalian cells (mouse lymphoma L5178Y) in comparison to those following .gamma.-rays. The yield of the total single-strand breaks, 3''OH terminals and sites susceptible to S1 endonuclease following fast neutrons was 50% of that following .gamma.-irradiation. The yield of double-strand breaks was slightly higher after fast neutrons than after .gamma.-rays. The percentage of the total single-strand breaks remaining unrejoined at 3 h after post-irradiation incubation was distinctly higher after the fast neutrons than after .gamma.-rays. The neutron-induced damage appears to carry a higher proportion of alkali-labile lesions compared to .gamma.-rays. The increase in the yield of double-strand breaks and of unrejoinable breaks is responsible for a high rbe [relative biological effectiveness] of the cyclotron neutrons.