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Suzuki, Michiyo; Hattori, Yuya; Sakashita, Tetsuya; Funayama, Tomoo; Yokota, Yuichiro; Ikeda, Hiroko; Kobayashi, Yasuhiko
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-raysYokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Muto, Yasuko*; Suzuki, Michiyo; Sakashita, Tetsuya; Kobayashi, Yasuhiko
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We investigate radiation-induced bystander effects. Cells irradiated with up to 2 Gy of carbon ions (108 keV/
m) and -rays (0.2 keV/m) were co-cultured with non-irradiated cells in the above and below of porous membrane. Non-irradiated bystander cells decreased their survival at 6 and 24 h in co-culture when 33% of cell population was irradiated. In addition, survival reduction of bystander cells was increased with dose and saturated at 0.5 Gy. The dose responses were similar between carbon ions and -rays, indicating that bystander effects were partly dependent on dose but independent of radiation quality. Next, 0.001% of cell population was irradiated with carbon ion (103 keV/m) and neon ion (380 keV/m) microbeams. Bystander cells decreased their survival at 24 h but not at 6 h in co-culture. From these, it was estimated that bystander effects were also dependent on the fraction of irradiated cells.
Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Ikeda, Hiroko; Sakashita, Tetsuya; Kobayashi, Yasuhiko
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In JAEA-Takasaki, there are two heavy-ion microbeam systems for biological study: the collimating and the focusing system. Both systems are installed individually on the vertical beam lines of the AVF-cyclotron. The collimating system, which was developed and installed at mid 1990's and utilized for various biological studies, generates heavy-ion microbeams using micro collimator. To explore the behaviors of the whole cell population after bystander irradiation, an integration of live-cell imaging technology into the cell targeting-and-observation system of the collimating system is under development. On the other hand, the focusing system was developed to irradiate heavy-ions to the target cells with beams finer than the collimating system. Using the system, we established a method to irradiate finer heavy-ion microbeam on individual HeLa cells. For rapid and accurate delivery of heavy-ions to the individual cells, a method for targeting cells with scanned beam is under development.
Ikeda, Hiroko; Yokota, Yuichiro; Funayama, Tomoo; Kanai, Tatsuaki*; Kobayashi, Yasuhiko
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The purpose of this study is to make clear the bystander effect between cancer cells and normal cells and to establish a new approach using microbeam for elucidating its molecular mechanism. When irradiated cells and non-irradiated cells were co-cultured without physical contact, it was found that clonogenic abilities of non-irradiated bystander cells increased between different type cells but decrease between same type cells. This suggests that bystander responses were greatly different between the same type cells and different type cells. However, we could detect only the medium-mediated bystander response in the co-culture experiment. Since there is another pathway that induces bystander response via gap junction intercellular communications, we planned to irradiate the mixed culture of different type cells using the heavy-ion microbeam system for elucidating its molecular mechanism. Now, we are constructing the new experimental approach and will report the latest findings.