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Ionising radiation-induced bystander effects are well recognised, but its dependence on dose or linear energy transfer (LET) is still a matter of debate. To test this, 49 sites in confluent cultures of AG01522D normal human fibroblasts were targeted with microbeams of carbon (103 keV mm21), neon (375 keV mm21) and argon ions (1260 keV mm21) and evaluated for the bystander-induced formation of micronucleus that is a kind of a chromosome aberration. Targeted exposure to neon and argon ions significantly increased the micronucleus frequency in bystander cells to the similar extent irrespective of the particle numbers per site of 1–6. In contrast, the bystander micronucleus frequency increased with increasing the number of carbon-ion particles in a range between 1 and 3 particles per site and was similar in a range between 3 and 8 particles per site. These results suggest that the bystander effect of heavy ions for micronucleus formation depends on dose.

著者人数: 20名, Accepted: 2012-02-20, 資料番号: SA1004128000

Radial energy deposition distribution, the distribution of DNA strand breaks and their yields were simulated by Monte Carlo track structure simulation for C and Ne ions with the same linear energy transfer (LET) around 450 keV/mm. The radial DNA damage distribution shows different pattern for C and Ne ions. Double strand break (DSB) are mostly formed in the central area, while the single strand break (SSB) tends to spread to the surrounding area. It is also shown that the production efficiency of the SSB and DSB depends on the radial distance. This result shows reasonable agreement with the recently obtained experimental observation, which indicates that different types of DNA damage shows different distribution patterns around C and Ne ion paths in cell nuclei.

PURPOSE: We examined biological responses of human glioma cells to irradiation with carbon ion beams (C-ions). METHODS AND MATERIALS: A human glioma-derived cell line, NP-2, was irradiated with C-ions. Apoptotic cell nuclei were stained with Hoechst 33342. Induction of autophagy was examined either by staining cells with monodansylcadaverine (MDC) or by Western blotting to detect conversion of microtuble-associated protein light chain 3 (MAP-LC3) (LC3-I) to the membrane-bound form (LC3-II). Cellular senescence markers including induction of senescence-associated beta-galactosidase (SA-beta-gal) were examined. The mean telomere length of irradiated cells was determined by Southern blot hybridization. Expression of tumor suppressor p53 and cyclin/cyclin-dependent kinase inhibitor p21(WAF1/CIP1) in the irradiated cells was analyzed by Western blotting. RESULTS: When NP-2 cells were irradiated with C-ions at 6 Gy, the major population of the cells died of apoptosis and autophagy. The residual fraction of attached cells (

We have established a single cell irradiation system, which allows selected cells to be individually hit with defined number of heavy charged particles, using a collimated heavy-ion microbeam apparatus at JAERI-Takasaki. This system has been developed to study radiobiological processes in hit cells and bystander cells exposed to low dose and low dose-rate high-LET radiations, in ways that cannot be achieved using conventional broad-field exposures. Individual cultured cells grown in special dishes were irradiated in the atmosphere with a single or defined numbers of 18.3 MeV/amu 12C, 13.0 MeV/amu 20Ne, and 11.5 MeV/amu 40Ar ions. Targeting and irradiation of the cells were performed automatically at the on-line microscope of the microbeam apparatus according to the positional data of the target cells obtained at the off-line microscope before irradiation. The actual number of particle tracks that pass through cell nuclei was detected with prompt etching of the bottom of the cell dish made of ion track detector TNF-1 (modified CR-39), with alkaline-ethanol solution at 37deg C for 15-30 minutes. Using this system, separately inoculated Chinese hamster ovary cells, confluent normal human fibroblasts, and single plant cells (tobacco protoplasts) have been irradiated. These are the first studies in which single-ion direct hit effect and the bystander effect have been investigated using a high-LET heavy particle microbeam

The possible mechanism of a radiationinduced bystander response was investigated by using a high-LET heavy particle microbeam, which allows selected cells to be individually hit with precise numbered particles. Even when only a single cell within the confluent culture was hit by one particle of 40Ar (1260 keV/um) or 20Ne (380 keV/um), a 1.4-fold increase of micronuclei (MN) was detected demonstrating a bystander response. When the number of targeted cells increased, the number of MN biphasically increased; however, the efficiency of MN induction per targeted cell markedly decreased. When 49 cells in the culture were individually hit by 1 to 4 particles, the production of MN in the irradiated cultures were 2-fold higher than control levels but independent of the number and LET of the particles. MN induction in the irradiatedculture was partly reduced by treatment with DMSO, a scavenger of reactive oxygen species (ROS), and was almost fully suppressed by the mixture of DMSO and PMA, an inhibitor of gap junctional intercellular communication (GJIC). Accordingly, both ROS and GJIC contribute to the above-mentioned bystander response and GJIC may play an essential role by mediating the release of soluble biochemical factors from targeted cells.

When cells were irradiated with ionizing radiation, non-irradiated cells around irradiated cells showed same biological effect, for example apoptosis, DNA damage, chromosomal aberration, and this phenomenon is called bystander effect. Bystander effect is caused by two major pathways. One is a gap junction signalling and the other is a medium-mediated signalling. The correlation of these pathways with bystander effect, and some transmission agents of this effect were reported in many papers. But the existence of the particle number-, dose or LET-dependency of this effect is still a matter of debate. In this experiment, we demonstrated that the dependency of bystander effect was observed in AG01522 cells exposed to photon or heavy-ion (carbon (120 keV/µm), neon (430 keV/µm) or argon (1260 keV/µm)) micro-beam, respectively. The bystander effect was estimated by the micronucleus (MN) formation which is a kind of a chromosome aberration. As the results, Ne- and Ar-ion beam with high-LET beams showed the bystander effects by only one particle irradiation, however the dose-dependency was not observed. C-ion beam with middle-LET showed the significant dose-dependency of bystander effect. On the other hand, X-ray micro-beam did not show the bystander effect as well as the dose-dependency. In summary, the bystander effect must have dose and LET dependency, however it is considered to be greatly dependent on some conditions, such as dose range, biological end point, radiation quality, and a kind of cells., Micros 2013 16th International Symposium of Microdosimetry

(1) 10kGyの放射線量で粉末食用色素の完全な殺菌が可能であった.(2) 極めて短時間で連続処理も可能であった.(3) 電子線照射により色素成分が分解退色するものの可視部吸収スペクトル, HPLC,色調変化等は通常の加熱,光分解等と同様であり,むしろ変化は少なかった.以上, FAO/IAEA/WHO合同専門家委員会の提案している10kGy以下の放射線量で大きな成分変化を来すことなく粉末食用色素の完全な殺菌が可能であった.この電子線照射におる粉末食用色素の殺菌は全く新しい処理技術であり,色素成分の変退色や新たな分解物質の生成が危惧される所であったが,今回の検討で,むしろ通常の加熱殺菌などよりも色素倍対する影響は少なく完全な殺菌が可能であることが判った.

第25回宇宙利用シンポジウム(2009年1月14日-15日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス), The Twenty-fifth Space Utilization Symposium (January 14-15, 2009: ISAS/JAXA Sagamihara, Japan), We have planned CERISE (C. elegans RNAi space experiment) on STS-129 spaceflight (2009 Nov. 12+) using a model organism Caenorhabditis elegans. In this experiment, our purposes are (1) evaluation of whether RNA interference (RNAi) occurs under space environment as the same manner as on the earth, and (2) to investigate the effects of microgravity on entire gene and protein expressions, protein phosphorylation, and muscle alterations in C. elegans beyond generations. We have also performed to construct biodosimeter to monitor the cosmic radiation on ISS and spacecrafts. Here we introduce the progress of CERISE experiment and the performance of the biodosimeter., 資料番号: AA0064297055

The chemical factor involved in bystander effect and its transfer pathway were investigated in a confluent human fibroblast cell (AG1522) population. Micronuclei (MN) and G1-phase arrest were detected in cells irradiated by carbon (~100 keV/um) ions at HIMAC. A very low dose irradiation showed a high effectiveness in producing MN, suggesting a bystander effect. This effectiveness was enhanced by 8-Br-cAMP treatment that increases gap junctional intercellular communication (GJIC). On the other hand, the effect was reduced by 5% DMSO treatment, which reduce the reactive oxygen species (ROS), and suppressed by 100 mM lindane treatment, an inhibitor of GJIC. In addition, the radiation-induced G1-phase arrest was also enhanced by cAMP, and reduced or suppressed by DMSO or lindane. A microbeam device (JAERI) was also used for these studies. It was found that exposing one single cell in a confluent cell population to exactly one argon (~1260 keV/um) or neon (~430 keV/um) ion, additional MN could be detected in many other unirradiated cells. The yield of MN increased with the number of irradiated cells. However, there was no significant difference in the MN induction when the cells were irradiated by increasing number of particles. MN induction by bystander effect was partly reduced by DMSO, and effectively suppressed by lindane. Our results obtained from both random irradiation and precise numbered irradiation indicate that both GJIC and ROS contributed to the radiation-induced bystander effect, but the cell gap junction channels likely play an essential role in the release and transfer of radiation-induced chemical factors., 12th International Congress of Radiation Research

Our previous study showed that nitric oxide was involved in the irradiation-induced multiplies bystander effects of increasing cell proliferation and enhancing cell plating efficiency but inducing micronucleus production. In the present work, with a confluent human fibroblast cell population, the chemical factor and its transfer pathway involved in irradiation-induced bystander effect were investigated. Micronucleus (MN) and G1-phase arrest could be detected in the cells irradiated by carbon ion beam. It was found that a low dose irradiation had a high effectiveness in producing MN, which indicated an existence of bystander effect. This low dose sensitive was enhanced by the treatment of 8-Br-cAMP that increased gap junctional intercellular communication (GJIC), and it was effectively reduced by the treatment of 5% DMSO. No low dose sensitive was observed when the cells were treated by 100 mM lindane, an inhibitor of GJIC. In addition, the irradiation-induced G1-phase arrest was also enhanced by cAMP but was obviously reduced by DMSO or lindane. Again, the role in alleviating irradiation-induced G1-phase arrest of lindane was greater than that of DMSO. A microbeam device was also used for this study. It was found that even 1 cell in a confluence AG1522 cell population was irradiated by exact one Ar13+ (~1200 keV/mm) or Ne7+ (~430 keV/mm) particle, additional MN could be detected in hundreds of other unirradiated cells. In addition, the yield of MN increased with the number of irradiated cells. But there was no significant difference in the MN induction when the cells were irradiated by the particles with different numbers. The MN induction was partly reduced by the treatment of cells with DMSO, and was much effectively eliminated by the treatment of lindane. Our results obtained from both random irradiation and precise numbered irradiation indicate that both GJIC and reactive oxygen species (ROS) contributed to the irradiation-induced bystander effect, but the cell gap junction channels likely play an essential role in the release and transfer of irradiation-induced chemical factors and than mediate the bystander effect in dominative., The First International Symposium on Ion Beams: Biological Effects and Molecular Mechanisms