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Narita, Ayumi; Kaminaga, Kiichi; Yokoya, Akinari; Noguchi, Miho; Kobayashi, Katsumi*; Usami, Noriko*; Fujii, Kentaro
Radiation Protection Dosimetry, 166(1-4), p.192 - 196, 2015/09
Times Cited Count：3 Percentile：25.85(Environmental Sciences)For the knowledge about irradiation effects of mammalian cells depending on the cell cycle, most of them had been analyzed by statistical approches. Our purpose is to establish the method for real-time observation of irradiated cells under a microscope. Fluorescent ubiquitination-based cell cycle indicator (FUCCI) human cancer (HeLa) cells (red indicates G1; green, S/G2) were exposed to a synchrotron X-ray microbeam. Cells in either G1 or S/G2 were selectively irradiated according to cell color observed in the same microscopic field in a culture dish. Time-lapse micrographs of the irradiated cells were acquired for 24 h after irradiation. The cell cycle was strongly arrested by irradiation at S/G2 and never progressed to G1. In contrast, cells irradiated at G1 progress to S/G2 with a similar time course as non-irradiated control cells. These results show single FUCCI cell exposure and live cell imaging are powerful methods for studying radiation effects on the cell cycle.
Suzuki, Masao*; Autsavapromporn, N.*; Usami, Noriko*; Funayama, Tomoo; Plante, I.*; Yokota, Yuichiro; Muto, Yasuko*; Suzuki, Michiyo; Ikeda, Hiroko; Hattori, Yuya; et al.
Journal of Radiation Research, 55(Suppl.1), P. i54, 2014/03
Autsavapromporn, N.*; Suzuki, Masao*; Funayama, Tomoo; Usami, Noriko*; Plante, I.*; Yokota, Yuichiro; Muto, Yasuko*; Ikeda, Hiroko; Kobayashi, Katsumi*; Kobayashi, Yasuhiko; et al.
Radiation Research, 180(4), p.367 - 375, 2013/10
Times Cited Count：58 Percentile：89.88(Biology)We investigated the role of gapjunction intercellular communication (GJIC) in the propagation of stressful effects in confluent normal human fibroblast cultures wherein only 0.036-0.144% of cells in the population were traversed by primary radiation tracks. Confluent cells were exposed to graded doses from X ray, carbon ion, neon ion or argon ion microbeams in the presence or absence of an inhibitor of GJIC. After 4 h incubation, the cells were assayed for micronucleus (MN) formation. Micronuclei were induced in a greater fraction of cells than expected based on the fraction of cells targeted by primary radiation, and the effect occurred in a dose-dependent manner with any of the radiation sources. Interestingly, the inhibition of GJIC depressed the enhancement of MN formation in bystander cells from cultures exposed to high-LET radiation but not low-LET radiation. The results highlight the important role of radiation quality and dose in the observed effects.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08
Times Cited Count：51 Percentile：88.4(Physics, Fluids & Plasmas)Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m
for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 
2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.
Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Yokoya, Akinari; Cunniffe, S. M. T.*; Watanabe, Ritsuko; Kobayashi, Katsumi*; O'Neill, P.*
Radiation Research, 172(3), p.296 - 305, 2009/09
Times Cited Count：25 Percentile：60.53(Biology)To characterize the DNA damage induced by K-shell ionization of phosphorus atom in DNA backbone on the level of hydration, the yields of DNA strand breaks and base lesions arising from the interaction of ultrasoft X-rays (USX) with energies around the phosphorus K-edge were determined using dry and fully hydrated pUC18 plasmid DNA samples. Base lesions and bistranded clustered DNA damage sites were revealed by post-irradiation treatment with the base excision repair proteins, Nth and Fpg. The complex types of damage, prompt and enzymatically induced DSB are preferentially induced by phosphorus K-resonance at 2153 eV rather than simple SSB and isolated base lesions particularly in hydrated conditions. It is concluded that not only the phosphorus K-resonance and resulting emission of low energy LMM-Auger electrons (120 eV) but also the level of hydration plays an important role in the induction of complex damage in plasmid DNA.
Kobayashi, Yasuhiko; Funayama, Tomoo; Hamada, Nobuyuki*; Sakashita, Tetsuya; Konishi, Teruaki*; Imaseki, Hitoshi*; Yasuda, Keisuke*; Hatashita, Masanori*; Takagi, Keiichi*; Hatori, Satoshi*; et al.
Journal of Radiation Research, 50(Suppl.A), p.A29 - A47, 2009/03
Times Cited Count：38 Percentile：72.75(Biology)Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.
IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08
Times Cited Count：12 Percentile：41.25(Physics, Fluids & Plasmas)The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.
Nagoshi, Masayasu*; Kawano, Takashi*; Makiishi, Noriko*; Baba, Yuji; Kobayashi, Katsumi*
Surface and Interface Analysis, 40(3-4), p.738 - 740, 2008/04
Times Cited Count：4 Percentile：7.02(Chemistry, Physical)Grazing incidence X-ray photoelectron spectroscopy (XPS) has been applied to mirror-polished stainless steel sheets and Si-wafer using incident X-ray with high energy from synchrotron radiation. Monochromatized X-ray with the energy of 1.8 keV to 3.6 keV was irradiated to the sample surfaces with various incident angles. Total reflection condition with the high-energy incident X-ray provides us X-ray photoelectron spectra having remarkably low background intensity. The results will be compared with background calculations in previous researches and discussed in terms of the penetration depth of X-ray and inelastic mean free path of photoelectrons. We also discuss the depth information of the obtained spectra.
Usami, Noriko*; Yokoya, Akinari; Ishizaka, Shozo*; Kobayashi, Katsumi*
Journal of Radiation Research, 42(3), p.317 - 331, 2001/09
Times Cited Count：8 Percentile：28.36(Biology)The characteristics of DNA lesions produced by the phosphorus K-shell absorption in yeast cells were studied using monochromatized soft X-rays tuned to the phosphorus K-edge peak (2153 eV) and below the peak energy (2147 eV). The repaired fractions of DNA double-strand breaks (dsb) were measured relatively by using both a mutant, (
), which shows the temperature-sensitive dsb repair-deficient, and a wild-type strain. The repaired fraction of lesion in , which corresponds to the relative yield of dsb reparable by the 
pathway, was not affected by the phosphorus photoabsorption. Repair of the produced lesions in the wild-type cells was also measured by comparing the surviving fraction of the immediately plated cells to that of those cells plated after holding in a non-nutrient medium for 80 hrs. The recovery of the surviving fraction after the holding treatment was dependent upon the soft X-ray energy. These results suggest that irrepairable lesions are produced by the inner-shell photoabsorption of phosphorus in DNA, although its yield is small.
Maezawa, Hiroshi*; Furusawa, Yoshiya*; Kobayashi, Katsumi*; Hieda, Kotaro*; Suzuki, Masao*; Usami, Noriko*; Yokoya, Akinari; Mori, Tomoyuki*
Acta Oncologica, 35(7), p.889 - 894, 1997/01
Times Cited Count：7 Percentile：22.9(Oncology)no abstracts in English
Yaita, Tsuyoshi; Narita, Hirokazu*; Suzuki, Shinichi; Shiwaku, Hideaki; Motohashi, Haruhiko; Ono, Hideo; Usami, Noriko*; Kobayashi, Katsumi*
Photon Factory Activity Report 1997, P. 81, 1997/00
no abstracts in English
Hieda, Kotaro*; Hirono, Taisuki*; Azami, Akira*; Suzuki, Masao*; *; Maesawa, Hiroshi*; Usami, Noriko*; Yokoya, Akinari; Kobayashi, Katsumi*
International Journal of Radiation Biology, 70(4), p.437 - 445, 1996/10
Times Cited Count：48 Percentile：95.41(Biology)no abstracts in English
Konishi, Hiroyuki; Yokoya, Akinari; Shiwaku, Hideaki; Motohashi, Haruhiko; *; Kashihara, Yasuharu*; *; Harami, Taikan; Sasaki, Teikichi; Maeta, Hiroshi; et al.
Nuclear Instruments and Methods in Physics Research A, 372, p.322 - 332, 1996/00
Times Cited Count：69 Percentile：97.59(Instruments & Instrumentation)no abstracts in English
Kobayashi, Katsumi*; Usami, Noriko*; Yokoya, Akinari
Journal of Radiation Research, 34(1), 110 Pages, 1993/03
no abstracts in English
*; Hieda, Kotaro*; Usami, Noriko*; Yokoya, Akinari; Kobayashi, Katsumi*
Radiat. Res., 131(1), p.72 - 80, 1992/07
Times Cited Count：16 Percentile：57.92(Biology)no abstracts in English
Yokoya, Akinari; Usami, Noriko*; Kobayashi, Katsumi*
Photon Factory News, 10(1), p.13 - 14, 1992/05
no abstracts in English
Yokoya, Akinari; Kobayashi, Katsumi*; Usami, Noriko*; *; Hieda, Kotaro*; *
Shinku Shigaisen (50nm Ijo) Niyoru Kakusan Sonsho Yuhatsu Kiko No Sogoteki Kenkyu, p.56 - 59, 1992/03
no abstracts in English
Yokoya, Akinari; Kobayashi, Katsumi*; Usami, Noriko*
Photon Factory Activity Report, P. 299, 1992/00
no abstracts in English
