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Sato, Tatsuhiko
no journal, ,
In the ICRU report 36 entitled "microdosimetry", the specific energy, z, is defined as the quotient of the energy imparted in microscopic site by its mass. The specific energy is a stochastic quantity, and its average value is equal to the macroscopic absorbed dose D. Introducing the concept of z, the difference between micro- and broad-beam experiments can be simply expressed by the difference of the probability densities of z in sub-cellular or cellular scales. As examples, cell survival fractions obtained using micro- and broad-beams were re-analyzed based on the probability densities of z in chromatin and cell-nucleus scales. The results of the analysis together with the discussion on the influence of the divergence of the probability density of z on the cell survival fractions will be presented at the meeting.
Watanabe, Ritsuko; Shiina, Takuya*; Yokoya, Akinari
no journal, ,
We have estimated the initial DNA damage spectrum by track structure simulation method. The result shows that the increase of the complexity of initial DNA damage and cell lethality show partially similar trend in their LET dependence. The goal of our study is to elucidate and modeling the relationship between initial DNA damage and radiation-induced cellular response by using the calculated DNA damage spectrum. For this purpose, the spatial distribution of the damage in larger scale should be considered. In this presentation, in addition to the damage spectrum, the spatial distribution of each type of DNA damage around the radiation track will be shown. The simulated DNA damage spectrum and the spatial distribution such as the distance between two clustered DNA damages in chromosome domain in cell nucleus model was discussed in comparison with the yield of lethal damage estimated from the experimentally obtained survival curves.
Suzuki, Michiyo; Sakashita, Tetsuya; Hattori, Yuya; Tsuji, Toshio*; Kobayashi, Yasuhiko
no journal, ,
To better understand the effects of radiation inherent to human activities such as manned space flight, diagnostic imaging, and radiation therapy, it is important to focus on not only the risks of carcinogenesis but also the potential for effects on critical functions such as learning, memory and/or motor control. The nematode Caenorhabditis elegans is a good in vivo model for the examination of radiobiological effects. Using this model, we recently found that whole body irradiation reduced both the locomotion using body-wall muscles and pumping motion (chewing and swallowing) using pharyngeal muscles, and that both movements were restored within several hours. However, there was an obvious difference in the aspect of the reduction between the locomotion and pumping. Though it is well-known that heavy ions charging particles with a high linear energy transfer (LET) induce higher relative biological effectiveness than low-LET radiation such as 
-rays, effects of heavy ion beams on 's motility were same as those of -rays. In this presentation, we will give an outline of the radiation effects on motor functions in and discuss about further studies to understand the detailed mechanism underlying the irradiation-induced reduction and restoration of movements.
Ikeda, Hiroko; Yokota, Yuichiro; Funayama, Tomoo; Muto, Yasuko; Kanai, Tatsuaki*; Kobayashi, Yasuhiko
no journal, ,
In this study, we investigated radiation-induced bystander effects between normal fibroblasts and cancer cells to elucidate the responses between normal tissues and tumor in heavy-ion radiotherapy. In our experiments, human lung normal fibroblasts WI-38 line and human lung cancer cells H1299/wtp53 line which is genetically modified to produce normal p53 proteins in their DNA damage response were used. Cells were irradiated with carbon-ion broad beams (LET = 108 keV/
m, Dose = 0.5 Gy) or Co-60 -rays (LET = 0.2 keV/m, Dose = 0.5 Gy), then survival rates of bystander cells after 6- or 24-hours co-culture with irradiated cells were calculated using colony formation assay. It was consequently found that survival rates of non-irradiated WI-38 cells increased when the cells were co-cultured with irradiated H1299/wtp53 cells. From this result, we conclude that some signals are released from irradiated H1299/wtp53 cells to promote cell adhesion and growth of bystander cells.
Yoshihara, Ryohei; Hase, Yoshihiro; Nozawa, Shigeki; Narumi, Issei; Takimoto, Koichi*; Hidema, Jun*; Sakamoto, Ayako
no journal, ,
We analyzed -ray-induced mutation spectrum in Arabidopsis seedling to investigate the effect of oxidative DNA damage on mutagenesis. Moreover, to evaluate the effect of nucleotide pool sanitization system on -ray-induced mutations, we analyzed a mutant deficient in the Arabidopsis 
gene that is a homologue of 
. The -ray sensitivity of the mutant was slightly higher, but not statistically significant, than that of wild type plant. However, the mutation spectra induced by -rays were different between the wild type and plants. From these results, it was suggested that the deficiency obviously affects on the mutagenesis but not the plant growth following -irradiation.
rster resonance energy transferAkamatsu, Ken; Shikazono, Naoya
no journal, ,
It is known that DNA lesions induced by ionizing radiation and chemicals can cause mutation and carcinogenesis. In particular, "clustered damage" site, that is a DNA region with multiple lesions within a few helical turns, is believed to hardly be repaired. This type of damage is considered to be induced around high-LET radiation tracks and at track-end of secondary electron. However, details of the clustered damage sites are not known. We have developed an analytical method for measuring the degree of dispersion of distances between DNA lesions using Frster resonance energy transfer (FRET). Experimentally-obtained FRET efficiencies of random distributed AP-sites on heat-treated DNA almost correspond to theoretical ones calculated on the basis of exponential distribution. Now we have tried to apply the FRET methodology to plasmid DNA irradiated with some radiation qualities.
Yamashita, Shinichi; Hiroki, Akihiro; Nagasawa, Naotsugu; Taguchi, Mitsumasa
no journal, ,
We have developed a less toxic and environment-friendly polymer gel dosimeter by employing radiation-crosslinked hydroxypropylcellulose hydrogel. It was found that this dosimeter becomes white and cloud-like state after -irradiation of dose clinically used in cancer therapy. Quantitative evaluation of this white cloudiness, the haze and the absorbance were measured. The increases of the haze and absorbance were different for different composition of solute monomer and crosslinker which are permeated into gel matrix to detect radiation. In conclusion, it can be possible to control the sensitivity of our gel dosimeter by controlling the composition.
Fujii, Kentaro; Fujii, Shinichiro*; Akimitsu, Nobuyoshi*; Tsukimoto, Mitsutoshi*; Kojima, Shuji*
no journal, ,
We analyze the luciferase activity to assess the energy transfer activity and the genetic information transfer activity and evaluate the change in activity as an inter-cellular signaling molecules by measuring ATP receptor-mediated phosphorylation of extra cellular signal-regulated kinase 1/2 (ERK1/2). In addition to the biological effect, we have also measured the molecular alterations using X-ray absorption and electro spray mass spectrometry (ESIMS). We observed attenuation of ATP receptor-mediated phosphorylation of ERK 1/2 and luciferase activity by the soft X-ray irradiations. Moreover, we observed the reduction of nucleotide from the X-ray absorption spectra and ESIMS. These results suggest that certain alteration of ATP structure induced by soft X-ray affects the biological function of ATP.
Urushibara, Ayumi; Kodama, Seiji*; Yokoya, Akinari
no journal, ,
no abstracts in English
Nishikino, Masaharu; Sato, Katsutoshi*; Kawachi, Tetsuya; Nishimura, Hiroaki*; Numasaki, Hodaka*; Teshima, Teruki*
no journal, ,
Techniques for generating high energy bright short-pulse Ka X-rays have been rapidly developed in recent progress made in utilizing intense ultrashort laser pulses. The soft X-ray laser is also generated from the laser-produced plasma. A highly spatial coherent XRL is generated by the oscillator-amplifier configuration with two targets. Use of X-ray focusing optics has resulted in focused X-ray beams of submicron spot size being achieved in soft and hard X-ray regions. The short duration of laser produced plasma source could be used as a new source in contrast to conventional X-ray sources in investigating the mechanism of the affect of radiation on biological cells. We have started to develop a focused X-ray beam irradiation system for use in studying radiobiological effects on cells, and demonstrated a preliminary study of radiation effect on culture cells irradiated with the X-ray laser and laser produced plasma Ka X-rays.
Muto, Yasuko; Funayama, Tomoo; Yokota, Yuichiro; Ikeda, Hiroko; Kobayashi, Yasuhiko
no journal, ,
no abstracts in English
Hirayama, Ryoichi*; Matsumoto, Yoshitaka*; Noguchi, Miho; Uzawa, Akiko*; Koda, Kana*; Furusawa, Yoshiya*
no journal, ,
The presence or absence of molecular oxygen dramatically influences the biological effect of low LET radiations. To produce oxygen effect, molecular oxygen must be present during the radiation exposure or at least during the lifetime of the free radicals generated by the radiation. Little study has been done to actually investigate the influence of oxygen after the radiation exposure. The present study was undertaken in order to explore the rejoining activity of DNA-DSB induced by anaerobic X-ray or carbon ion (
80 keV/m) irradiations under oxic and hypoxic holdings (37 
C). DNA-DSB in CHO cells were analyzed by a static-field gel electrophoresis. The kinetics of the rejoining could be described by a sum of fast and slow components. The slow component of DNA-DSB induced by X-ray under oxic incubation was faster than that under hypoxic incubation. Furthermore, the percentages of non-reparable DNA damage were 5% and 20% under oxic and hypoxic incubation conditions, respectively. However, no difference between oxic and hypoxic incubation conditions was found for carbon ion irradiation. There results indicate that molecular oxygen influences the rejoining of DNA-DSB after low LET radiation exposure.
Yokoya, Akinari; Ukai, Masatoshi; Oka, Toshitaka; Fujii, Kentaro
no journal, ,
The ionized DNA molecule produced through innershell electron excitation and successive Auger relaxation is thought to be a precursor of DNA damage. When the energy of soft X-rays is close to the threshold of the innershell ionization, a produced photoelectron might be recaptured by the atom because the slow photoelectron could be overtaken by an Auger electron during the relaxation. This event causes a sharp decline of the Coulomb potential of the atom, and accordingly the photoelectron could be trapped by the atom again. In this study we semiclassically analyze the probability of the photoelectron recapture by DNA constituent atoms. Obtained results are discussed by comparison with our previous data of the unpaired electron showing significant change of the yield in energy regions of particular K-shell ionizations.
Shiina, Takuya; Sugaya, Yuki; Shiraishi, Iyo; Watanabe, Ritsuko; Yokoya, Akinari; Tsuruoka, Chizuru*; Suzuki, Masao*
no journal, ,
There has been very little knowledge of AP sites and AP clusters induced by heavy ion beam irradiation. In order to clarify the relation between track structure of C ions (290MeV/nucleon, LET 13, 60keV/m) or X-rays and the induction processes of an AP or AP clusters, we measure the yield of AP sites visualized by the treatment of irradiated pUC18 plasmid DNA with the AP endoclease (Nfo), which converts an AP site to detectable single strand break. Several scavenging capacities of the samples are tested to estimate the effect of indirect action of diffusible OH radicals in the induction of AP site. These experimental data will be discussed with theoretical radiation track structure in the respect of repair susceptibility of the AP cluster.
Shiraishi, Iyo; Shiina, Takuya; Sugaya, Yuki; Shikazono, Naoya; Yokoya, Akinari
no journal, ,
Cellular response to cluster DNA damage might depend on the order of repair processes because the configuration of the lesions will be modified by the reaction of the initial repair protein, affecting the DNA-binding or lesion-excision activities of the latter repair protein. In the present study, we investigate how the initial enzymatic repair affects the activity of the latter repair enzyme. Plasmid DNA (pUC18) irradiated with C6+ ion is treated with two base excision repair enzymes, Nth and Fpg, which convert pyrimidine and purine lesions to a SSB. The enzymatic activities are quantified by measuring the conformational changes of the plasmid using agarose gel electrophoresis. Obtained results show that the amount of enzymatically induced SSB is slightly (about 5%) less in DNA sample treated with Nth first and then Fpg than that in the sample treated with Fpg first and then Nth. The repairability of clustered damage induced by high-LET ions will be discussed.
Sugaya, Yuki; Shiina, Takuya; Shiraishi, Iyo; Fujii, Kentaro; Yokoya, Akinari
no journal, ,
In this study, we aim to reveal the role of direct ionization at the energy region of oxygen K-edge in the selective DNA damage. We measure the yields of single strand breaks (SSBs), base lesions, and AP sites produced in thin film of pUC18 plasmid DNA by irradiation of several soft X-rays which excite a1s electron to anti-bonding energy states or a vacuum level. The yields of base lesions and AP sites are determined by post-irradiation-treatment of the DNA with enzymatic probes, which excise (Nth and Fpg for pyrimidine and purine base lesion, respectively, and Nfo for AP site) and convert the lesions into detectable SSBs. The obtained data will be compared with our previous data obtained by soft X-ray irradiation around carbon and nitrogen K-edge region.
Hata, Kuniki; Urushibara, Ayumi; Yamashita, Shinichi; Shikazono, Naoya; Yokoya, Akinari; Muroya, Yusa*; Katsumura, Yosuke*
no journal, ,
In the present study we verify the chemical repair property of an antioxidant, edaravone. At first, edaravone radical was measured by pulse radiolysis method to confirm that edaravone reacts efficiently with dGMP radical. In order to verify the chemical repair of radicals in DNA macromolecules by edaravone we irradiated -ray to aqueous solutions of plasmid DNA. In addition to strand breaks we quantified the chemical yields of AP sites and base lesions using base excision repair enzymes. Production of AP sites and base lesions were more significantly inhibited than that of strand breaks by addition of edaravone. This result indicates that edaravone can chemically repair DNA radicals resulting in AP sites or base lesions on DNA.
Igarashi, Shosuke*; Onuki, Toshihiko; Sakamoto, Fuminori; Tachibana, Akira*
no journal, ,
Effects of radiation on the cisplatin associated DNA have been studied in base level by using Sanger method. The results indicated that presence of cisplatin enhanced strand break by X-ray irradiation, and positions of the strand break bases are related to the association of cisplatin with bases.
Kobayashi, Yasuhiko; Funayama, Tomoo; Taguchi, Mitsumasa; Tanaka, Atsushi; Wada, Seiichi*; Watanabe, Hiroshi*; Furusawa, Yoshiya*; Kiguchi, Kenji*; Fukamoto, Kana*; Sakashita, Tetsuya; et al.
no journal, ,
The application of localized radiation using heavy-ion microbeams eliminates the effect of non-uniform ion hits on cell population, since individual cells can be irradiated one by one with a defined number of energetic heavy ions. Another advantage associated with the use of heavy-ion microbeam irradiation concerns the precise detection of ion-hit position on micron-scale targets to obtain the information on the position of ion traversal and on cellular responses induced by ion hit simultaneously. Therefore microbeam is an operative means to elucidate initial cellular responses together with the relationship with ion track structure. The use of heavy-ion microbeams has not been restricted to the area of radiation biology. Targeted irradiation using heavy-ion microbeams has been applied to various biological studies, such as plant physiology or developmental biology, as a radio-microsurgical tool to inactivate specific tissue or cell populations in multicellular organisms and to investigate their function. The outlines of these studies, which were carried out using our collimated heavy-ion microbeam at JAEA-Takasaki, will be introduced.
Oka, Toshitaka; Yokoya, Akinari; Fujii, Kentaro
no journal, ,
no abstracts in English