K. Hieda
Rikkyo University
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Featured researches published by K. Hieda.
International Journal of Radiation Biology | 1989
M.S. Sasaki; Katsumi Kobayashi; K. Hieda; Takeshi Yamada; Y. Ejima; Hiroshi Maezawa; Y. Furusawa; T. Ito; Shigefumi Okada
The induction of chromosome aberrations was studied in human peripheral blood lymphocytes irradiated in vitro with synchrotron-produced monochromatic soft X-rays of quantum energy in a range between 4.8 and 14.6 keV. These X-rays were more effective in producing chromosome aberrations (dicentrics and rings) than 60Co gamma-rays. The efficiency increased with increasing LET of the photoelectrons and their associated Auger electrons, reaching a maximum at a track average LET (L delta = 100, T) of around 4 keV/microns, and tended to decrease or become rather refractory with further increase of LET. This unique LET dependency was consistent with the dual nature of chromosome aberration formation, and interpreted as a reflection of a limited range of photoelectrons as compared with the size and intranuclear geometry of the elemental chromatin fibres as vehicles of damage interaction.
International Journal of Radiation Biology | 1991
Katsumi Kobayashi; K. Hieda; Hiroshi Maezawa; Yoshiya Furusawa; M. Suzuki; Takashi Ito
The effects of K-shell absorption of phosphorus atoms on yeast cells were investigated using synchrotron X-rays that were tuned to the resonance absorption peak (2153 eV). Three types of cellular effect (cell inactivation, induction of gene conversion at the trp-5 locus, and cell membrane impairment (changes in the permeability] were measured. It was demonstrated that the enhancement factor was 1.4 at the resonance peak regarding both lethality and the induction of gene conversion in reference of off-peak irradiation (2146 and 2160 eV). No difference was found between the two off-peak irradiation energies. No cell membrane impairment was detected, irrespective of the X-ray photon energies employed within the fluence range tested. These results strongly suggest that K-shell X-ray absorption in the resonance mode by cellular phosphorus atoms causes significantly more cellular effects than the off-resonance mode of absorption, probably via some specific changes induced in the phosphates of the DNA strand. Calculations using the number of phosphorus atoms in a defined size of the trp locus (2127 base pairs) on the DNA and the absorption cross-section of the resonance mode of phosphorus showed that gene conversion is inducible at a rate of 0.13 per X-ray photon absorption per locus. These results are discussed regarding the modes of K-shell photoabsorption.
International Journal of Radiation Biology | 1994
K. Hieda
The recent development of irradiation systems using synchrotron radiation (SR) as a source is enabling researchers to obtain intense monochromatic photons having a narrow bandwidth in the vacuum-UV (VUV) and soft X-ray regions. We can thus systematically study the photon energy dependence of DNA damage formation in these energy regions. The photon energy dependence provides useful information about how energy-absorbing modes--excitations, so-called superexcitations, outer- and inner-shell ionizations--affect the type and amount of DNA damage. Furthermore, low energy electrons produced by low energy photons through photoelectric interactions are useful for studying how the electron energy affects the induction of DNA damage. A report is given on the present status of the SR irradiation systems in Japan as well as some results concerning the formation of DNA damage, in vitro and in vivo, by monochromatic photons in the VUV and soft X-ray regions.
International Journal of Radiation Biology | 1988
Hiroshi Maezawa; K. Hieda; Katsumi Kobayashi; Yoshiya Furusawa; T. Mori; Keiji Suzuki; T. Ito
In order to examine enhanced killing that might be induced by Auger cascades in the incorporated atoms in cells, bromouracil(BrU)-labelled E. coli cells were irradiated with monoenergetic X-rays at 13.49 and 12.40keV, just above and below the K-absorption edge of bromine. In both cases BrU-labelled cells were more sensitive for killing than were normal cells. However, when the degree of BrU-sensitization was compared between the two energies of X-rays, the enhanced killing at 13.49 keV was only small, 2 +/- 8 per cent based on the D0 value in saline. By the addition of DMSO, which is believed to suppress radical-mediated effects, killing of BrU-labelled cells was enhanced at 13.49 keV by 8 +/- 4 per cent as compared with 12.40 keV, based on D0. These results have been examined in terms of absorbed energy in BrU-labelled cells and in terms of the number of induced Auger events.
International Journal of Radiation Biology | 1991
Noriko Usami; Katsumi Kobayashi; Hiroshi Maezawa; K. Hieda; Shozo Ishizaka
The biological effects of inner-shell ionization in bromine atoms incorporated into DNA in the form of bromodeoxyuridine monophosphate (BrdUMP), induced by monochromatized synchrotron X-rays, were studied using a deoxythymidine monophosphate (dTMP)-permeable mutant of yeast, Saccharomyces cerevisiae. The BrdUMP-incorporated yeast cells were irradiated with monochromatic X-rays of 13.51 or 13.45 keV, between which the bromine K-absorption edge (13.47 keV) is located. The cells were 1.07 times more sensitive to irradiation by 13.51 keV X-rays than at 13.45 keV, while dTMP-incorporated cells did not show any difference in sensitivity. In the presence of a radioprotector during irradiation, BrdUMP-incorporated cells showed a larger enhancement (1.20). These enhancements observed in the bromine-incorporated cells cannot be explained only by an increase of the absorbed dose due to a substitution of CH3 group of thymine by bromine. It may be concluded that a major part of the enhancement was caused by inner-shell photoionization, followed by an Auger cascade of the bromine in the DNA. The quantum yield of lethality caused by the photoabsorption of bromine K-shell is not affected by the presence of cysteamine, suggesting the biological enhancement by the Auger processes may not be influenced by chemical protection.
Review of Scientific Instruments | 1989
K. Kobayashi; K. Hieda; Hiroshi Maezawa; Takashi Ito; T. Naito
Irradiation experiments on biological samples with monochromatic ultrasoft x‐rays are inevitable in elucidating the initial process in radiobiological phenomena. However, intense light sources with continuous spectra in this wavelength region have not been available until recently. Synchrotron radiation is the best light source for the study because of its intense, continuous emission spectrum. The purpose of the project is to develop a grazing incidence ultrasoft x‐ray monochromator for radiation biology studies using synchrotron radiation as a light source. The following characteristics are required in the monochromator, namely, (1) high throughput with moderate resolution; (2) wide beam area with uniform intensity; (3) little contamination of higher order lights; and (4) easy operation and maintenance. Considering the above requirements, a plane‐grating type monochromator (PGM) is adopted. The monochromator consists of two premirrors (M1 and M2), a plane grating (1200 l/mm), a concave focusing mirror (...
Radiation Measurements | 2005
Nakahiro Yasuda; Teruaki Konishi; Kenichi Matsumoto; Tomoya Yamauchi; Taku Asuka; Yoshiya Furusawa; Y. Sato; Keiji Oda; H. Tawara; K. Hieda
Radiation Measurements | 2005
Kuniaki Amemiya; Hiromitsu Takahashi; Y. Kajimoto; Masaharu Nakazawa; Hironobu Yanagie; T. Hisa; Masazumi Eriguchi; Yoshinobu Nakagawa; Toshikazu Majima; Teruyoshi Kageji; Yoshinori Sakurai; Tooru Kobayashi; Teruaki Konishi; K. Hieda; N. Yasuda; K. Ogura
The Japan Radiation Research Society Annual Meeting Abstracts The 47th Annual Meeting of The Japan Radiation Research Society | 2004
Toshiyuki Natsume; Nobuo Munakata; Teruaki Konishi; Nakahiro Yasuda; Y. Sato; Yoshiya Furusawa; Atsushi Kamata; Kyohei Nishida; K. Hieda
Journal of Radiation Research | 2003
Toshiyuki Natsume; Nobuo Munakata; Teruaki Konishi; Akihiro Takeyasu; Izumi Koyama; Kenichi Matsumoto; Nakahiro Yasuda; Yukio Satou; Yoshiya Furusawa; K. Hieda