本研究目的旨在利用細胞群落分析、基因微陣列系統與流式細胞儀研究細胞生存率、基因表現、細胞週期與細胞凋亡的改變，以了解極低頻電磁場對生物體的影響。基因微陣列晶片上共點印7334個經確定序列的人類基因，其中的每一個基因在每片晶片上皆點印四次重複。人類表皮細胞為人類面對環境壓力的第一道防線，所以選用此細胞研究極低頻電磁場的生物效應。一組實驗組的細胞先經過2 Gy伽傌射線照射後，再接受3小時極低頻電磁場(60 Hz，5 gauss)照射﹔另一組實驗組的細胞則是只接受極低頻電磁場的照射。細胞群落分析顯示不論細胞是否先經過伽傌射線的照射，極低頻電磁場照射皆並未對細胞的存活率造成明顯改變。基因分析的結果發現，細胞只接受極低頻電磁場的照射時，相關於DNA解螺旋與DNA複製的基因有下調的現象，其他與細胞週期、細胞凋亡相關的基因亦有受到調控。細胞先接受伽傌射線照射再加以極低頻電磁場干擾時，相關於DNA解螺旋及DNA複製的基因下調有累加的現象，然其他細胞週期與細胞凋亡的基因則沒有觀察到此現象。細胞週期分析中，依不同的細胞密度下進行實驗之結果不同，無法做出肯定之結論。細胞凋亡分析發現極低頻電磁場的照射並未能造成細胞凋亡的顯著改變。總結而言，利用基因微陣列系統研究極低頻電磁場的生物效應，本研究為第一個發現極低頻電磁場可影響細胞部分功能基因群的調控，這些基因包括細胞生存、細胞週期調控、細胞凋亡調控與DNA解螺旋相關之基因。雖然在細胞群落分析與流式細胞儀分析結果中，並沒有發現極低頻電磁場對細胞生存率、細胞週期與細胞凋亡造成明顯影響，然而這樣的結果可能意味著研究極低頻電磁場所造成的微弱生物效應，使用基因微陣列系統為敏感度較高的檢測工具。

The aim of this study was to investigate the possible biological effects of extremely low frequency field (ELF-EMF) by implementing three approaches - colony assay, cDNA microarray, and flow cytometry to evaluate the variation of cell survival rates, gene expression profiles, and cell cycle as well as apoptosis, respectively. Each in-house gene chip consisted of four replicated spots of each of 7334 sequence-verified human genes. We chose keratinocytes to analyze the biological effects of ELF-EMF because keratinocytes were the first line of self-defense of human body against to the environmental stress. Cells were exposed to ELF-EMF for 3 hours with or without pre-irradiation of 2 Gyγ-ray. The result of colony assay demonstrated that ELF-EMF exposure did not alter cell survival with or without priorγ-ray irradiation. However, the microarray data illustrated that ELF-EMF treatment repressed the expression of DNA helicase-related and DNA replication genes, as well as regulated the expression of several cell cycle-related and apoptotic genes. Moreover, data showed that when γ-ray irradiated keratinocytes were treated with additional ELF-EMF exposure, the DNA helicase-related and DNA replication genes were further down-regulated. However, the cell cycle- and apoptosis-related genes did not display similar regulatory characteristics. In flow cytometry approach, our results demonstrated that the cell cycle distributions affected by ELF-EMF were dependent on the cell density. Therefore, no firm conclusion can be drawn from the available data. Apoptotic analysis revealed that ELF-EMF exposure had not induce significant levels of apoptotic death in keratinocytes. In conclusion, our microarray data has shown for the first time that the expression of several group of genes were affected by ELF-EMF exposure, including cell survival-, cell cycle- and apoptosis-related genes as well as DNA helicase-related genes. Although colony assay and flow cytometry analysis had not detect any notable biological effects, this may imply that microarray analysis is a more sensitive screening tool to investigate minor biological effects caused by ELF-EMF exposure.

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