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CsWatanabe, Ritsuko; Hattori, Yuya; Kai, Takeshi
International Journal of Radiation Biology, 92(11), p.660 - 664, 2016/11
Times Cited Count：2 Percentile：19.46(Biology)To understand the effect of internal exposure of Cs, we focus on estimation of microscopic energy deposition pattern and DNA damage induced by directly emitted electrons (beta-rays, internal conversion electrons, Auger electrons) from Cs. Monte Carlo track simulation method was used to calculate the microscopic energy deposition pattern. To simulate the energy deposition by directly emitted electrons, we considered the multiple ejections of electrons after internal conversion. Induction process of DNA strand breaks and base lesions was modeled and simulated using Monte Carlo methods for cell mimetic condition. The yield and spatial distribution of simple and complex DNA damage were calculated for the cases of 
-rays and electrons from Cs. The simulation showed that significant difference of DNA damage spectrum was not caused by the difference between secondary electron spectrum by -rays and directly ejected electron spectrum. The result support that the existing evaluation that internal exposure and external exposure are almost equivalent.
Fujii, Kentaro; Izumi, Yudai; Narita, Ayumi*; Krishna, G.*; Alain, T.*; Rodolphe, V.*; Marie-Pierre, G.*; Marie-Francoise, P.*; Marie-Anne, H.*; Yokoya, Akinari
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In order to reveal the role of hydration water on the process in terms of Auger effect of DNA constituent atoms, we measured a mass spectrum of ions desorbing from hydrated deoxyribose (dR) films exposed to monochromatic soft X-rays (560 eV). Desorbing positive ions were detected by a quadrupole mass spectrometer to examine the effect of Coulomb explosion of valence holes produced as a result of Auger decay after the ionization. The yield of desorbing ions which were produced by the destruction of the furanose ring structure of dR, obviously supressed when one layer of water molecules was deposited onto the film. This result suggests that the hydration water layer on the film inhibits the intense destruction of the furanose induced by the ionization of K-shell electrons of oxygen, or the desorption of the resulting fragment ions from the sample film.
Kai, Takeshi; Yokoya, Akinari; Ukai, Masatoshi*; Fujii, Kentaro; Watanabe, Ritsuko
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Sugaya, Yuki*; Fujii, Kentaro; Yokoya, Akinari
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Noguchi, Miho; Yokoya, Akinari; Kaminaga, Kiichi; Fujii, Kentaro; Suzuki, Keiji*; Usami, Noriko*
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Kado, Masataka; Kishimoto, Maki; Tamotsu, Satoshi*; Yasuda, Keiko*; Aoyama, Masato*; Tone, Shigenobu*; Shinohara, Kunio*
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We have developed a laser-plasma soft X-ray microscope composed of an intense short pulsed soft X-ray source and a contact microscopy system in which soft X-rays are irradiating onto biological cells directly cultivated on a recording media, an X-ray photo resist, and succeeded in observing inner structures of living biological cells. Using a fluorescence microscope with the soft X-ray microscope to observe the same biological cells at the same time, accurate identification and high resolved observation of cellular organelles have been achieved such as inner structure of Leydig cells from mouse testis, structural deformation of apoptotic HeLa S3 nuclei and mouse immune cells. In the case of the immune cells we have found structural changes possibly attributed to the activation of immune function.
