Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Sato, Tatsuhiko; Hamada, Nobuyuki*; Sakashita, Tetsuya
no journal, ,
It is difficult to quantitatively compare between the results obtained from broadbeam and microbeam experiments because of the difference of physical indexes for characterizing their radiation fields. We therefore developed a new method for calculating the microdosimetric PD for any radiation fields, utilizing the microdosimetric function of the PHITS code. A new model assembly was then established for estimating the cell surviving fraction based on the calculated microdosimetric probability density (PD), considering both targeted and nontargeted effects in the same framework. The model assembly reproduced very well the experimentally determined surviving fraction measured with microbeam or broadbeam of energetic heavy ions as well as X-ray microbeam. The features of the established models together with the possible role of nontargeted effect in broadbeam fields will be discussed at the meeting.
and analyses of effects on muscular movementsSuzuki, Michiyo; Hattori, Yuya; Sakashita, Tetsuya; Funayama, Tomoo; Yokota, Yuichiro; Kobayashi, Yasuhiko
no journal, ,
Ikeda, Hiroko; Yokota, Yuichiro; Funayama, Tomoo; Kanai, Tatsuaki*; Nakano, Takashi*; Kobayashi, Yasuhiko
no journal, ,
There have been some reports on bystander effects induced by proton microbeam in contact co-cultured different type cells, but there are few reports using heavy-ion microbeam. So, we have established a new contact co-culture system between human lung normal fibroblast cell line WI-38 and human lung cancer cell line H1299/wt
in the same dish. We have also adapted patterning irradiation systems which automatically irradiated to cancer cells (or normal cells) in a certain range by making use of the target cell irradiation technique at JAEA-Takasaki. Thereby, we were able to successively irradiate to 250 sites of confluent cancer area (lengthwise: 5 mm) so as not to overlap the irradiated range, using carbon-ion microbeam collimated by aperture of 
20 
m. Now, we are analyzing DNA damage and repair of patterning irradiation samples by evaluating focus numbers of immunostained 53BP1 and 
-H2AX. The details of the method and findings will be reported in the talk.
Yokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Muto, Yasuko*; Suzuki, Michiyo; Sakashita, Tetsuya; Kobayashi, Yasuhiko
no journal, ,
We investigated the influence of irradiated dose and radiation quality on bystander effect. Human normal fibroblasts were irradiated with carbon-ion beam and -rays, and then co-cultured with non-irradiated cells. Following co-culture for 24 h with or without c-PTIO, a scavenger of nitric oxide (NO), the survival rates of non-irradiated cells and the concentrations of nitrite, an oxide of NO, in the co-culture medium were measured. Survival of the non-irradiated cells decreased with increasing dose and reached around 80% at 0.5 Gy. The dose-response curves were similar between carbon-ion beam and -rays, indicating the bystander effect depended on dose but not on radiation quality. c-PTIO suppressed reduction of survival rates of the non-irradiated cells. Furthermore, there were negative relationships between survival rates of the non-irradiated cells and nitrite concentrations. In summary, the amounts of produced NO might be a determinant of the bystander effect.
to microbeam irradiationSakashita, Tetsuya; Suzuki, Michiyo; Hattori, Yuya; Ikeda, Hiroko; Muto, Yasuko*; Yokota, Yuichiro; Funayama, Tomoo; Hamada, Nobuyuki*; Shirai, Kana*; Kobayashi, Yasuhiko
no journal, ,
We applied the microbeam irradiation of the central nervous tissue in to analyze direct radiation effects at a tissue level. Also, to investigate the mechanism of modulatory effects of irradiation on the salt chemotaxis learnign (SCL), we used two mutants (
and 
) related to the SCL. Well-fed adults of wild-type and mutant were irradiated with 12,000 carbon ion particles corresponding to 500 Gy at micro-aperture area. Immediately after microbeam irradiation, the SCL performance was examined based on the chemotaxis index (CI). CI during the SCL was decreased in the wild-type and mutant animals, but microbeam irradiation did not significantly affect CIs of mutants. The difference of the SCL between and mutants will be discussed at the meeting.
Hattori, Yuya; Yokoya, Akinari; Watanabe, Ritsuko
no journal, ,
It is widely recognized that bystander phenomena are caused by two intercellular signaling pathways, via culture medium and gap junctions. We consider that modeling the bystander effect on cell-cycle progression is the first step toward investigating the mechanism of transgenerational effects, which ultimately trigger radiation-induced carcinogenesis. Our model describes the cultured cellular population as two-dimensional grids. The simulation algorithm consists of four steps: (1) irradiation, (2) generation and diffusion of intercellular signals, (3) induction of DNA damage by direct irradiation and intercellular signals, (4) response on cell cycle for DNA damage. The cell cycle is represented as a virtual clock that includes several checkpoint pathways within a cyclic process. Using this model, we simulated how affect the intercellular signals on cellular responses in sparsely and densely cultured conditions. In this work, we adopted life-time and diffusion constant of cytokine and calcium ion for signals via culture medium and signals via gap-junction, respectively. The simulation shows that the signals increased cell-cycle modification with increase of dose. The bystander effect on cell-cycle was significant for cells in sparse condition than in dense condition, showing that the model works reasonably. However, the effect of signals via gap-junction was unexpectedly small. It was caused by the short life-time of calcium ion. It indicates that other mechanism as reemission of other substances should be considered for the model of gap-junction. Obtaining the experimental data comparable with our simulation can be of great help to understand the mechanism of bystander effect.
Funayama, Tomoo; Yokota, Yuichiro; Sakashita, Tetsuya; Suzuki, Michiyo; Kobayashi, Yasuhiko
no journal, ,
The focusing heavy-ion microbeam system of JAEA-Takasaki can focus heavy-ion beam to minimum one micrometer in vacuum. Using the system, irradiation of HeLa cells were carried out. The cells were stained with CellTracker Orange fluorescent dye and inoculated on a film of ion track detector, CR39. The positions of each target cell were extracted from the fluorescent cell image using image analysis code. To irradiate cells with scanned beam, we developed a code that calculates a set of beam scanner voltages from the extracted cell positions. After irradiation, the hit positions of the ion were visualized as the etched pits, and the cells were stained with the -H2AX antibody. We found the correspondence of the distribution pattern of the etch pits, the cell positions and the -H2AX foci. Thus we concluded that these developed equipment, codes and methods have sufficient performance to irradiate cells rapidly and accurately with the focusing heavy-ion microbeam.
Ueda, Daisuke*; Funayama, Tomoo; Yokota, Yuichiro; Suzuki, Michiyo; Sakashita, Tetsuya; Kobayashi, Yasuhiko; Shirai, Koji*
no journal, ,
The occurrence of DNA damage-induced cell cycle arrest is consider to depend on the amount and/or seriousness of DNA damage. However, the detailed mechanisms have been obscure. When whole egg of the silkworm in early embryogenesis was subjected to carbon ions, the developmental arrest was observed, however, about 2 hours after irradiation, the mitotic cleavage resumed, indicating the eggs at this stage can induce the cell cycle arrest by checkpoints after irradiation. On the other hand, the locally targeted irradiation with carbon-ion microbeam to 10% of the nuclei was not able to induce the developmental arrest. In the egg, several of abnormal cleaved nuclei were observed, which are considered to be the irradiated nuclei that stop their cleavage. Meanwhile, when 30-40% of nuclei were irradiated, the embryonic development stopped. The result indicate the checkpoint-induced arrest of the silkworm egg at intralecithal cleavage stage may depend on number or ratio of the damaged nuclei.
Autsavapromporn, N.*; Plante, I.*; Liu, C.*; Konishi, Teruaki*; Usami, Noriko*; Funayama, Tomoo; Azzam, E.*; Murakami, Takeshi*; Suzuki, Masao*
no journal, ,
Confluent human skin fibroblasts (NB1RGB) were exposed to various types of microbeam with a different linear energy transfer (LET) at mean absorbed doses 0.4 Gy, wherein 0.036-0.4% of the cells were targeted by IR. Following 20 populations post-irradiation, the cells were harvested and assayed for micronucleus formation, mutation assay and protein oxidation. The progeny of bystander cells exposed to X rays and protons showed the persistence of oxidative stress, and correlate with the increased micronucleus formation and mutant fraction. However, such effects were not observed after irradiation by carbon ions. Interestingly, inhibition of GJIC mitigated the damaging effects in the progeny of bystander cells exposed to protons and carbon ions but not X rays. These data show carbon ions can reduce cancer risk after microbeam irradiation compared with X rays or protons, and GJIC may be a critical mediator in the observed effect.
Oda, Shoji*; Yasuda, Takako*; Hibi, Yusuke*; Asaka, Tomomi*; Ikeda, Hiroko; Muto, Yasuko*; Yokota, Yuichiro; Sakashita, Tetsuya; Suzuki, Michiyo; Funayama, Tomoo; et al.
no journal, ,
We have developed a new irradiation protocol for tissue specific irradiation to living embryo and adult medaka, 
. In the study, a testis of p53 knockout fish were irradiated with multi-shots of microbeam. Less numbers of testis-ova were induced in the in p53- lacking testis 1 week after the irradiation compared to whole body irradiated testis. Specific irradiation of microbeam onto the right (or left) lobe of the optic tectum in medaka embryos of 2 days post fertilization ectopically induced apoptotic cells in the body trunk and the tail in addition to the irradiated position. The systemic effects as endocrine system, autonomic nervous system and immunity reactions occur in adult medaka and these results suggested that the systemic effects might be functional even in developing embryos.