Growth retardation of Paramecium and mouse cells by shielding them from background radiation.
In the 1970s and 1980s, Planel et al. reported that the growth of paramecia was decreased by shielding them from background radiation. In the 1990s, Takizawa et al. found that mouse cells displayed a decreased growth rate under shielded conditions. The purpose of the present study was to confirm that growth is impaired in organisms that have been shielded from background radiation. Radioprotection was produced with a shielding chamber surrounded by a 15 cm thick iron wall and a 10 cm thick paraffin wall that reduced the γ ray and neutron levels in the chamber to 2% and 25% of the background levels, respectively. Although the growth of Paramecium tetraurelia was not impaired by short-term radioprotection (around 10 days), which disagreed with the findings of Planel et al., decreased growth was observed after long-term (40-50 days) radiation shielding. When mouse lymphoma L5178Y cells were incubated inside or outside of the shielding chamber for 7 days, the number of cells present on the 6th and 7th days under the shielding conditions was significantly lower than that present under the non-shielding conditions. These inhibitory effects on cell growth were abrogated by the addition of a ¹³⁷Cs γ-ray source disk to the chamber. Furthermore, no growth retardation was observed in XRCC4-deficient mouse M10 cells, which display impaired DNA double strand break repair.
Radiation Research Center and Graduate School of Science, Osaka Prefecture University, Osaka, Japan.
Masanobu
M
Kawanishi
Katsuyuki
K
Okuyama
Kazunori
K
Shiraishi
Yatsuka
Y
Matsuda
Ryoichi
R
Taniguchi
Nobuyuki
N
Shiomi
Morio
M
Yonezawa
Takashi
T
Yagi
D000818:Animals; D001417:Background Radiation / Q000009:adverse effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects*; D004260:DNA Repair; D007940:Leukemia L5178; D051379:Mice; D016805:Paramecium tetraurelia / Q000254:growth & development* / Q000528:radiation effects*; D011835:Radiation Protection; D013997:Time Factors