Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
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.
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.
Kaburagi, Masaaki*; Watanabe, Ritsuko; Sato, Tatsuhiko; Yokoya, Akinari; Pinak, M.; Katsumura, Yosuke*; Uesaka, Mitsuru*
no journal, ,
In Boron Neutron Capture Therapy (BNCT) borate-ions selectively accumulated in tumor an following neutron capture reactions emit secondary particles, low-energy alpha particle and lithium ion. These particles deposit their energies in tumor effectively. However, there is not enough experimental data to evaluate BNCT biological effectiveness from clinical and research experiments. In our presentation, we introduce results on the research focused on evaluation of the biological effectiveness of the production of DNA strand breaks during BNCT. DNA strand breaks is evaluated based on the microdosimetric data by using Monte Carlo track simulation code. This presentation shows the results of energy deposition, OH radical yields, and DNA strand break yields in aqueous solution. The simulation results are compared with experimental data. Finally we also plan to conduct DNA strand break simulations under conditions as those in actual treatments.
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.
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.
Ouchi, Noriyuki; Pinak, M.
no journal, ,
As one of the measures of radiation effects, dose vs. frequency of DNA strand breaks (at the cellular level) or, frequency of chromosomal aberrations (at the individual level) are commonly used. As we know, dose, DNA strand breaks and chromosomal aberrations are successive events, there are no common understandings for these relations. We have investigated many types of chromosomal dynamics using mathematically modeled whole human chromosome 17. Here, we will report on the relationship between physical properties of dynamics of chromosomal broken ends and concentration speed of typical repair enzymes.
Muto, Yasuko; Funayama, Tomoo; Yokota, Yuichiro; Ikeda, Hiroko; Kobayashi, Yasuhiko
no journal, ,
no abstracts in English
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.
locusHase, Yoshihiro; Yoshihara, Ryohei; Nozawa, Shigeki; Narumi, Issei
no journal, ,
The accelerated heavy ions deposit most of their energy close to the end of their range. Little is known about the mutational effects of ion beams near the range end, especially in plants. To gain insight into the mutagenic effects of accelerated heavy ions in plants, the mutagenic effects of carbon ions near the range end (mean LET: 425 keV/m) were compared with the effects of carbon ions penetrating the seeds (mean LET: 113 keV/m). We analyzed the mutations occurred in Arabidopsis locus with the emphasis on large deletions. Arabidopsis seeds obtained by crossing wild-type Col with the 
mutant were used as a material, and the DNA markers that can distinguish Col and sequence were used to detect deletions. While the frequency of generation of glabrous mutant sectors was not different between the two types of carbon-ion irradiation, large deletions (
30 kb) were six times more frequently induced by carbon ions near the range end. The 352 keV/m neon ions also showed a 6.4 times increase in the frequency of large deletions compared with the 113 keV/m carbon ions. These results suggest that the proportion of large deletions increases with LET in plants.
Funayama, Tomoo; Yokota, Yuichiro; Sakashita, Tetsuya; Kobayashi, Yasuhiko
no journal, ,
To improve a throughput of the cell irradiation using focusing microbeam, we developed a code that calculates voltages, which will be applied to a beam scanner for moving beam spot rapidly to the target positions. Using a developed code, a set of voltages was calculated from a pre-obtained cell image, and a film of CR-39 was irradiated by scanned beam according to the calculated voltages. After irradiation, hit positions of ion were visualized as etch pits, and the spatial distribution of them was observed. The distribution pattern of source cell image and etch pits on CR-39 film were well correlated, so that it was suggested that the developed code can finely convert detected cell positions to corresponding scanner voltages. Thus we concluded that using the code we will become able to irradiate cell rapidly with scanned heavy-ion microbeam.
Yokota, Yuichiro; Funayama, Tomoo; Muto, Yasuko; Ikeda, Hiroko; Kobayashi, Yasuhiko
no journal, ,
In this study, we investigated a time dependency of bystander effect. In experiments, we irradiated normal human fibroblasts with carbon-ion microbeam (LET=103 keV/m, 10 particles/irradiated site), carbon-ion broad beam (0.13 Gy) and Co-60 -rays (0.2 keV/m, 0.5 Gy). In broad-beam and -ray irradiation, irradiated cells and non-irradiated cells were co-cultured with porous membrane. The ratio of irradiated cells and bystander cells was 1:20,000 in microbeam irradiation and 1:2 in broad-beam and -ray irradiation, respectively. In microbeam-irradiated samples, the survival rate of bystander cells did not change at 6 h but decreased to about 80% at 24 h. In broad-beam and -ray irradiated samples, the survival rate of bystander cells decreased to 80 to 90% at 6 h or later. From these results, it was found that bystander effect is dependent on time after irradiation and number of irradiated cells.
using heavy-ion microbeamSakashita, Tetsuya; Suzuki, Michiyo; Muto, Yasuko; Yokota, Yuichiro; Funayama, Tomoo; Hamada, Nobuyuki*; Fukamoto, Kana*; Kobayashi, Yasuhiko
no journal, ,
An increasing body of data indicates that ionizing radiation causes learning impairments. We recently found the modulatory effect of -rays on the salt chemotaxis learning that was manifested as a decrease in chemotaxis. However, we have no direct evidence for the interaction of ionizing radiation with the central neuronal tissue (nerve ring) of the nervous system in . Localized ionizing irradiation is useful to analyze radiation effects at a cellular or tissue level. Thus, to investigate the effects on the nerve ring, we used the heavy-ion microbeam system installed at the Takasaki Ion accelerators for Advanced Radiation Application of JAEA. To achieve during-learning irradiation, we have developed the live-targeting system for non-paralyzed using the micro-total analysis systems to restrict their motion, and this will be discussed.
Sakashita, Tetsuya
no journal, ,
Low dose or low fluences of ionizing radiation induces Poisson distribution of the exposure dose in a cell population (macro-scale). On the other hand, microbeam irradiation technique makes one-cell exposure with an exact quantity possible to do. However, there are many problems on understanding common or different points between macro and micro scale for radiation biology, because of a bystander response and an application limit of dose (J/kg). The present paper will discuss on these points.
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.
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.
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.