| Project/Area Number |
13450217
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Civil and environmental engineering
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| Research Institution | Azabu University |
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Principal Investigator |
HIRATA Tsuyoshi Azabu University, Health and Environmental Sciences, Professor, 環境保健学部・水環境学研究室, 教授 (50005493)
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| Co-Investigator(Kenkyū-buntansha) |
MORITA Shigemitsu Azabu University, Health and Environmental Sciences, Assistant, 環境保健学部, 講師 (50318888)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥14,900,000 (Direct Cost: ¥14,900,000)
Fiscal Year 2003: ¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 2002: ¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 2001: ¥5,300,000 (Direct Cost: ¥5,300,000)
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| Keywords | Cryptosporidium / Inactivation / Ultraviolet / Gamma ray / Electron beam / Infectivity / Reactivation / Coexisting substances / Cryptosporidium parvum / 脱嚢 / 汚泥 / マウス感染症 / 細胞感染症 / HCT-8 / 温度依存性 / 線量率依存性 |
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| Research Abstract |
Experimental studies on radioactive rays irradiation were conducted to determine the efficacy of inactivating C. parvum oocysts at various temperatures and intensities. The infectivity decreased exponentially as radiation doses increased. The gamma ray and beta ray doses resulting in a 2 log_<10> reduction in infectivity were 94 Gy and 92 Gy, respectively. Temperature and intensity did not significantly affect the efficacy of radioactive rays irradiation in reducing the infectivity of oocysts. Gamma ray and beta ray doses required for 2 log_<10> reduction in viability as evaluated using in vitro excystation were 13,000 Gy and 12,000 Gy, respectively. Thus, radioactive ray treatment resulted in oocysts that were able to excyst but not infect.
The potential of irradiated oocysts to recover infectivity by photoreactivation and dark repair was investigated. There was no recovery in infectivity following treatment by fluorescent-light irradiation or storage in darkness.
The effectiveness of U
… More
V irradiation per unit dose towards an oocyst suspension where humin was mixed homogeneously with the oocysts, was nearly as high as that towards an oocyst suspension in pure water. This indicates that even though the UV beam passed through a turbid fluid, the effectiveness of UV irradiation per unit dose remained unaltered. Our results also suggest that the adhesion of humin to the oocyst wall has no marked shielding effect. As to kaoline which does not adhere to the oocyst wall, UV irradiation was slightly more potent towards C. parvum oocyst suspensions in water containing kaoline than towards oocyst suspensions in pure water. Because the increase in potency was negligible, however we did not study whether the increase resulted from scattering of the UV beam by kaoline particles. A trend was noted that adhesion of kaoline to the oocyst wall resulted in a decrease in inactivation as did adhesion of humin. However, the magnitude of log_<10> inactivation during adhesion of kaoline was only about 10% less than that in pure water irrespective of whether assessment was made by excystation assay or by mouse infectivity assay. Less
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