| Project/Area Number |
03304053
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
放射線5生物学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
SASAKI Masuo Kyoto Univ. Rad. Biol. Center, Prof., 放射線生物研究センター, 教授 (20013857)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUBARA Sho Yokohama City Univ. Faculty of Med., Prof., 医学部, 教授 (40014120)
SAWADA Shozo Hiroshima Univ. Inst. Nuclear Med., Prof., 原爆放射能医学研究所, 教授 (60034625)
SUZUKI Fumio Kanazawa Univ. Faculty of Pharmacy, Ass. Prof., 薬学部, 助教授 (10019672)
KOBAYASHI Katsumi Inst. for High Energy Physics Photon Factory, Ass. Prof., 放射光実験施設, 助教授 (20114077)
HIEDA Kotaro Rikkyo Univ. Faculty of Sci., Prof., 理学部, 教授 (20062656)
斉藤 眞弘 京都大学, 原子炉寒実験所, 助教授 (40027454)
星 正治 広島大学, 原爆放射能医学研究所, 助教授 (50099090)
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| Project Period (FY) |
1991 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥20,100,000 (Direct Cost: ¥20,100,000)
Fiscal Year 1993: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1992: ¥8,000,000 (Direct Cost: ¥8,000,000)
Fiscal Year 1991: ¥9,100,000 (Direct Cost: ¥9,100,000)
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| Keywords | Low-energy radiation / Secondry electron / Radiation Weighting factor / DNA breakage / Mutation / Choromosome aberration / Photoabsorption / Ultrasoft X-ray / 光電吸収 / 軟X線 / 中速中性子 / 生物学的効果比(RBE) / 光子活性化療法 / 特性X線 / 放射光 / 核分裂中性子 / 体細胞突然変異 / K殻吸收端 |
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| Research Abstract |
The present research has been carried out to explore the primary process of radiation action on living material by the use of currently developing radiation sources for energy regulated low-energy X-rays and neutrons. Dissociation of DNA, when it was dry, could be explained by the specific energy absorption of constituent atoms, but was due to the ionization by secondary electrons for the wet DNA.This has been confirmed in the experiments on the mutation induction by ultrasoft X-rays in yeast cells and chromosome aberration formation in cultured mouse cells, where biological effects could not be explained by a simple photoabsorption of phosphorus atoms in DNA.Moreover, the effectiveness of low-energy, but not high-energy, photons increased with the increase in the concentration of macromolecules, indicating a significant contribution of Auger elecrtons. The lymphocyte chromosome aberrations were proved to be enhanced by resonance absorption of X-ray energy by iodine atoms in X-ray contrast medium, suggesting the possible use of photoreactivation therapy for cancer treatment. Neutrons with energy around 1 MeV were highly effective in the induction of mutation, cell killing and morphological transformation. Surprisingly, low-eneregy neutrons obtained be neutron filters were found to have similar biological effectiveness. This finding may pose a re-evalution of radiation weighting factor for low-energy neutrons. Indeed, somatic mutation frequencies in Atomic-bomb survivo13EA\rs were found to be higher in Hiroshima than in Nagasaki, suggesting that the contribution of neutrons could not be ignored in Hiroshima.
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