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Ushigome, Takeshi*; Shikazono, Naoya; Fujii, Kentaro; Watanabe, Ritsuko; Suzuki, Masao*; Tsuruoka, Chizuru*; Tauchi, Hiroshi*; Yokoya, Akinari
Radiation Research, 177(5), p.614 - 627, 2012/05
Times Cited Count：23 Percentile：68.76(Biology)The yield of DNA damage produced in fully hydrated plasmid DNA films has been investigated to determine the linear energy transfer (LET) dependence of damage induction. The yield of single strand breaks (SSBs) with increasing LET levels of He, C and Ne ions. On the other hand, the yields of prompt double strand breaks (DSBs) increased with increasing LET. SSBs were additionally induced by treatment with base excision repair proteins, glycosylases, indicating that base lesions are produced in the hydrated DNA. This result shows that nucleobase lesions are produced via both chemical reactions with diffusible water radicals and direct energy deposition onto DNA or the hydrated layer. The yield of SSBs or DSBs observed by enzymatic treatment notably decreased with increasing LET. These results indicated that higher LET ions preferentially produce a complex type of damage that might compromise the activities of the proteins used in this study.
Ichimasa, Michiko*; Awagakubo, Sayuri*; Takahashi, Miho*; Tauchi, Hiroshi*; Hayashi, Takumi; Kobayashi, Kazuhiro; Nishi, Masataka; Ichimasa, Yusuke*
Fusion Science and Technology, 48(1), p.759 - 762, 2005/07
Times Cited Count：7 Percentile：44.9(Nuclear Science & Technology)There exists various kinds of HT oxidizing soil bacteria in the world, and we have conducted the investigation of HT oxidation activity of such bacteria. In the fusion facility where deuterium and tritium will be used as its fuel, the system is necessary to eliminate tritium from atmospheric air. General tritium elimination method is oxidation and dehumidification, and high temperature catalyst is used in the present system for oxidation. Application of the HT oxidation bioreactor, which can oxidize in room temperature, to this oxidation process has possibility to get higher tritium elimination efficiency, so we started to study the bioreactor. In the recent study, we can get high oxidation ratio of 85% in the processing conditions of 200 Bq/cm
as tritium concentration in air, 100 cm/min as flow rate and once-through processing using the Caisson Assembly for Tritium Safety Study (CATS) in JAERI. This result encourages this development study.
Urushibara, Ayumi; Ushigome, Takeshi; Shikazono, Naoya; Fujii, Kentaro; Tauchi, Hiroshi*; Yokoya, Akinari
no journal, ,
no abstracts in English
Yokoya, Akinari; Ushigome, Takeshi; Shikazono, Naoya; Fujii, Kentaro; Urushibara, Ayumi; Suzuki, Masao*; Tauchi, Hiroshi*; Watanabe, Ritsuko
no journal, ,
The yields of single- and double-strand breaks (SSB and DSB), base lesions and clustered damage induced in DNA were measured after exposing to various kinds of radiation. To focus on the effect of direct energy deposition from radiation track, we prepared hydrated DNA as well as solution sample with various scavenging capacities. Base excision repair enzymes, EndoIII and Fpg, were used to detect oxidative base lesions. The obtained results show that (1) the yield of directly induced SSB by the soft X-irradiation is about 30 percent of total SSBs in a cell mimetic condition and (2) the SSB yield does not significantly depend on the quality of radiation. On the other hand, (3) the yields of base lesions show a maximum by soft X-irradiation and drastically decreases with increasing of LET. (4) Soft X-rays are more effective in inducing base lesions than ions with similar LET, and (5) EndoIII treatment gives significantly higher SSB yield than those by Fpg treatment.
Suzaka, Takeshi; Shikazono, Naoya; Fujii, Kentaro; Yokoya, Akinari; Tauchi, Hiroshi*
no journal, ,
Soft X-rays have been widely used for the diagnostic of breast cancer (mammography). It has been generally thought that the relative biological effectiveness (RBE) of soft X-ray irradiation to living cells is similar to those of higher energy X-ray or 
-ray irradiation. On the other hand, Hill indicates that the risk of the soft X-ray exposure to organs may be higher than that of the -ray exposure because the interaction of soft X-ray photons with matter generates low energy secondary electrons. These electrons deposit their energy within a small volume of the scale of micrometers, thus induce dense ionization or excitation in genome DNA, whereas much less is known about the detail of the biological effect of soft X-rays. Recently we have shown that the yields of DNA strand breaks and oxidative base lesions induced in plasmid DNA by the direct effects of soft X-rays (150 kVp) is significantly higher than those by -ray irradiation. Present study investigates the effect of soft X-ray (150 kVp, W-target) irradiation to E. coli cells to highlight cellular responses. For this purpose, we have developed a novel experimental method to examine cell lethality and mutation frequency. A thin layer (
100
m) of cell-sample was prepared on a membrane so that all cells are uniformly irradiated with soft X-ray photons which have a short range in biological materials. We chose two genes, namely rpsL and mutant lac gene, as indexes of mutagenesis. Since experimental conditions strongly affected the survival of the cells, we have established optimal conditions for the experiment, such as temperature of solutions and cell density during culture. Using this method, we obtained the dose responses of survival fraction and mutation frequency of E. coli cells irradiated with soft X-rays. The correlation between DNA damage and the cellular effect of soft X-rays will be discussed.
Yokoya, Akinari; Ushigome, Takeshi*; Tauchi, Hiroshi*; Suzuki, Masao*; Tsuruoka, Chizuru*; Noguchi, Miho; Fujii, Kentaro; Shikazono, Naoya; Watanabe, Ritsuko
no journal, ,
In order to clarify the characteristics of DNA damage induced by high LET radiation, the yields of strand breaks and base lesions induced in closed-circular plasmid DNA (pUC18) were measured after exposing to various kinds of radiation (He, Ne and C ions; 2 to 900 keV/m). Base excision repair enzymes were used to detect oxidative base lesions. The obtained results show that (1) the yield of prompt SSBs does not depend significantly on the LET, (2) whereas the yield of DSBs increases with increasing LET, (3) The yields of isolated nucleobase lesions detected by enzymes decrease drastically with increasing LET and (4) C and Ne ions induce less base lesions than He ions when compared in the same LET region. These results indicate that the yield of cluster of nucleobase lesions, which are less readily processed by the base excision repair proteins, depends not only LET but also ion species irradiated.
Yamanishi, Toshihiko*; Kakiuchi, Hideki*; Tauchi, Hiroshi*; Yamamoto, Tokuhiro; Yamamoto, Ichiro*
no journal, ,
