• 作者： 戴華; 郭宗德; 梁治子; 近藤宗平
• 作者服務機構： 中華民國中央研究院植物所; 日本大阪大學醫學院放射線基礎醫學教室
• 中文摘要： 目前檢定環境中的致變劑(mutagen)或致癌劑(carcinogen)通常對測定的生物體使用高劑量短時間的處理。此種處理與事實不符。在自然環境中生物體暴露在致變劑的機會是微量而且是長時間的。此兩種處理對生物體的影響可能有所不同，為了解此種差異在本研究中曾用N-methyl -N'-nitro-N-nitrosoguanidine (MNNG), methyl-methanesulfonate(MMS), mitomycin C (MMC)和furylfuramide (FF)等四種致變劑為測定藥劑，以大腸菌為測定生物探討短期高劑量及長期低劑量的處理對生物體所引起的影響是否有差異。在本研究中MMS和MMC在長期低劑量的處理對大腸菌所引起的影響與短時期高劑量的處理完全相同，但FF和MNNG就有很大的差別，FF和MNNG在長期低劑量下處理其突變率有降低的現象，由結果推測FF長期低劑量的處理，對大腸菌的DNA造成的傷害，有較高的除去修補作用(excisionrepair)而 MNNG之長期低劑量的處理，可能產生一種適應性反應（adaptive-response)而造成較低的突變。
• 英文摘要： Most studies on mutagenesis involve exposing the organisms to a large dose of mutagen for a shortperiod. It is not the case in natural environment; organisms are often exposed to a low concentration ofmutagens for a long period. So it is very important to study the low dose-rate effect of chemicals forevaluating the environmental mutagens. The study of low dose-rate effect of four mutagens, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG),methyl methanesulfonate (MMS), mitomycin C (MMC) and furylfuramide (FF) in wild type Escherichiacoil H/r was carried out. Diminutions in FF-and MNNG-induced mutation were observed under low dose-rate treatment compared to that under high dose-rate treatment. Higher efficiency of excision repair andadaptive-response may response for low dose-rate effect of FF-and MNNG-treatment respectively. No dif-ference in MMS-and MMC-induced mutation frequencies between high and low dose-rate exposure wasdetected. No threshold values were observed under the low dose-rate treatment of FF and MNNG even en-hanced repair ability was shown.
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