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

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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.