A. Wojcik et al., DO DNA DOUBLE-STRAND BREAKS INDUCED BY ALU-I LEAD TO DEVELOPMENT OF NOVEL ABERRATIONS IN THE 2ND AND 3RD POSTTREATMENT MITOSES, Radiation research, 145(2), 1996, pp. 119-127
Several authors have reported that ionizing radiation can give rise to
novel aberrations several mitotic divisions after the exposure. At ou
r institute this phenomenon has been observed in mouse preimplantation
embryos. This cell system is uniquely well suited for such investigat
ions because the first three cell divisions show a high degree of sync
hrony. Thus the expression of chromosomal aberrations at the first, se
cond and third mitosis after irradiation can be scored unambiguously.
To investigate whether DNA double-strand breaks may be the lesions res
ponsible for the delayed expression of chromosomal aberrations, we hav
e studied the frequencies of aberrations in the first, second and thir
d mitosis after treatment of one-cell mouse embryos with the restricti
on enzyme Alu I. Embryos were permeabilized with Streptolysin-O. The r
esults indicate that the induction of double-strand breaks does not le
ad to novel aberrations in the third post-treatment mitosis. Several e
mbryos scored at the second mitosis showed very high numbers of aberra
tions, indicating that Alu I may remain active in the cells for a peri
od of one cell cycle. After treatment with Streptolysin-O alone, enhan
ced aberration frequencies were observed in the third post-treatment m
itosis, suggesting that membrane damage has a delayed effect on the ce
llular integrity. (C) 1996 by Radiation Research Society.