@misc{oai:repo.qst.go.jp:00072219,
 author = {Wang, Bing and Tanaka, Kaoru and Katsube, Takanori and Ninomiya, Yasuharu and Hirakawa, Hirokazu and Liu, Cuihua and Maruyama, Kouichi and Vares, Guillaume and Nakajima, Tetsuo and Nagamatsu, Aiko and Fujimori, Akira and Nenoi, Mitsuru and 王 冰 and 田中 薫 and 勝部 孝則 and 二宮 康晴 and 平川 博一 and 劉 翠華 and 丸山 耕一 and Ｇｕｉｌｌａｕｍｅ Ｖａｒｅｓ and 中島 徹夫 and 永松 愛子 and 藤森 亮 and 根井 充},
 month = {Oct},
 note = {Purpose: The galactic cosmic rays and solar particle events contain high atomic number and energy (HZE) particles such as iron-56 (Fe) ions. The potential relative biological effectiveness (RBE) of high linear energy transfer (LET) HZE particle-induced cytotoxicity and genotoxicity is of particular health concern on possible increased risk to systemic infection and mortality, and cancer in astronauts due to prolonged missions in outer space. To investigate the genotoxicity from exposures to high LET HZE particles, ground-based experiments were carried out at the National Institute of Radiological Sciences (NIRS) using total body irradiation (TBI) of mice with accelerated Fe particles generated by the Heavy Ion Medical Accelerator in Chiba (HIMAC).
\nMaterials and Methods: C57BL/6J Jms strain female mice of 8 weeks old (SLC, Japan) were used in the present study. Animals were maintained in a conventional animal facility under an 7:00 a.m.–7:00 p.m. light/dark cycle. They were housed in autoclaved cages with sterilized wood chips, and were allowed free access to standard laboratory chow (MB-1, Funabashi Farm, Japan) and acidified water ad libitum. Animals were treated in accordance with the Guidelines for the Care and Use of Laboratory Animals established by NIRS. All experimental protocols involving mice were reviewed and approved by the NIRS Institutional Animal Care and Use Committee. For accelerated Fe particles, the beam energy was 500 MeV/nucleon, corresponding to an average LET of 200 keV/mm. TBI was performed at a dose ranging from 0.1 to 3.0 Gy. The dose rates for delivering a dose less than 1.0 Gy (0.1, 0.3, and 0.5 Gy) and 1.0 Gy or more (2.0 and 3.0 Gy) were at about 0.1 Gy/min and 3.3 Gy/min, respectively. X-rays were generated with an X-rays machine (Pantak 320S, Shimadzu, Japan) operated at 200 kVp and 20 mA, using a 0.50 mm Al + 0.50 mm Cu filter. An exposure rate meter (AE-1321M, Applied Engineering, Japan) was used for the dosimetry. The dose rates for delivering a dose less than 1.0 Gy (0.1 and 0.5 Gy) and 1.0 Gy or more (3.0, 4.0, and 5.0 Gy) were at about 0.1 Gy/min and 0.8 Gy/min, respectively. The RBE of high LET Fe particles relative to low LET X-rays for induction of acute genotoxicity and late residual damage in the hematopoietic system was determined respectively at one and two months after TBI using the frequency of micronuclei in bone marrow erythrocytes as the biological endpoint. In addition, the health condition as measured by body weight gain and the hemogram of the peripheral blood was also investigated.
\nResults and Conclusions: The present study is still in progress. Data for body weight gain during the period of study and data for the hemogram of the peripheral blood at one and two months after TBI have been collected underlying statistical analysis. Observation of micronuclei in bone marrow erythrocytes is ongoing. At the annual meeting, preliminary results on the relative effectiveness of heavy ion irradiations from accelerated Fe particles for induction of genotoxicity in the hematopoietic system will be introduced and discussed.
\nAcknowledgments: This work was partially supported by both the Ministry of Education, Culture, Sports, and Science Culture (MEXT) Grant-in-Aid for Scientific Research on Innovative Areas, Grant Number 15H05935 “Living in Space” and two Research Project Grants (22B-258 from 2009 to 2012 and 14J-286 from 2014 to 2016) with Heavy Ions at NIRS-HIMAC. The authors thank all the staff of Experiment Support Group, Accelerator Division, and Accelerator Engineering Corporation for performing heavy-ion irradiations. The expert technical assistance and administrative support of Ms. Hiromi Arai, Mr. Sadao Hirobe, Ms. Mikiko Nakajima, and Ms. Yasuko Morimoto are gratefully acknowledged.
\nKeywords: Relative Biological Effectiveness, Heavy Iron Irradiations, Genotoxicity, Hematopoietic System, Mice=, 2016 RRS (Radiation Research Society)},
 title = {Relative Effectiveness of Heavy Ion Irradiations from Accelerated Iron-56 Particles for Induction of Genotoxicity in the Hematopoietic System in Mice},
 year = {2016}
}