Manufacture of an apparatus for exposure to magnetic fields and biological effect of the magntic fields

我们制造了一种用于培养细胞暴露于低密度低频磁场的装置。本研究设计并制造了极低频磁场（ELFMF）长期低密度（0 ~ 9 mT）照射培养细胞的设备，并检测了极低频磁场对中国仓鼠卵巢（CHO）细胞生长、c-myc mRNA表达和突变频率的影响。ELFMF设备包括一个内置磁铁发生器的二氧化碳培养箱，使用内径250毫米的亥姆霍兹线圈，距离160毫米，128转，滑动调节器和温控器。5 mT ELFMF暴露、假暴露和常规培养箱孵育对CHO细胞的生长速率和c-myc表达均无显著差异。另一方面，CHO-K1细胞在60 Hz的5 mT ELFMF下，有或没有初始x射线照射长达12周，使用6-硫代鸟嘌呤抗性突变试验分析了次黄嘌呤-鸟嘌呤磷酸核糖基转移酶（HPRT）基因的突变频率。长期暴露于5mT ELFMF长达12周并没有增加CHO-K1细胞中HPRT基因的突变。然而，x射线诱导突变的增强在x射线照射后长期5mt ELFMF暴露中被观察到。来自高压电力线的环境极低频电磁场的密度应至少比本研究中使用的密度小数百倍。除非有未知的机制涉及暴露于非常高密度的ELFMF下的诱变，否则环境ELFMF引起的癌症诱导可能非常低或不太可能。然而，联合暴露于x射线和极低频电磁场的影响应进一步研究。

We had manufactured an appatus for exposure of cultured cells to low density of low frequency magnetic fields. We disigned and manufactured equipments for long-term and low-density (0 to 9 mT) exposures of cultured cells to extremely low frequency magnetic fields (ELFMF), and examined the effects of ELFMF on cell growth, c-myc mRNA expression and the mutation frequency in Chinese hamster ovary (CHO) cells. The ELFMF equipment consists of a CO2 incubator with a built-in magnet generator using Helmholtz coils being 250 mm in inner diameter, 160 mm in distance and 128 turns, a slide regulator and a thermocontroller. No significant difference in the growth rate and the c-mycexpression of CHO cells was observed with 5 mT ELFMF exposure, sham-exposure and incubation in a conventional incubator. On the other hand, CHO-K1 cells were exposed to 5 mT ELFMF at 60 Hz with or without initial X-irradiation for up to 12 weeks, and mutation frequency in the hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene was analyzed using the 6-thioguanine-resistant mutation assay. The long-term exposures for up to 12 weeks to 5mT ELFMF did not increase mutations of HPRT gene in CHO-K1 cells. However, the enhancement of X-ray-induced mutations was observed in the treatment of X-irradiation followed by long-term 5 mT ELFMF exposures. The density of environmental ELFMF from high voltage power-lines should be at least several hundred times less than the density used in this study. Unless there are unknown mechanisms that involve mutagenesis under exposure to very highdensity ELFMF,cancer induction due to environmental ELFMF may be very low or unlikely. However, the effects of the combined exposure to X-rays abd ELFMF should be further investigated.