Evaluation of Damage in DNA Molecules caused by Very-Low-Frequency Magnetic Fields Using Bacterial Cells

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The effect of intermediate frequency magnetic fields or, very-low-frequency magnetic fields (VLFMIF) on living biological cells was investigated using a highly sensitive mutagenesis assay method. A bacterial gene expression system for mutation repair (umu system) was used for the sensitive evaluation of damage in DNA molecules. According to Miyakoshi's investigation, mutant frequency of HPRT gene was proportional to the induced current.In our study, Salmonella typhimurium TA1535 /pHYUmuLuxAB were exposed to VLFMF (20 kHz and 1mT) in a specially designed magnetic field loading chamber.20 kHz and 1mT was almost same as 50 Hz and 400 mT in terms of f×B. However, no significant differences between exposure to 20 kHz and 1 mT magnetic fields and control were observed in the umu gene expression. This may be attributed to the radius of Schale for culture. The induced current density in culture is shown following equation.J=_<σΠ> fBrWhere σ : conductivity of culturef : magnetic field frequencyB : magnetic flux densitiesr : radius of ShaleThe induced current is proportional to not only f×B but also r of Schale for culture. The radius r of Schale used by experiment of Miyakoshi was approximately 10 times larger than that of microtube using in our study. Then current induced by 50 Hz and 400 mT magnetic field was 10 times larger than that of our experiment.