Study type: Medical/biological study (experimental study)

Combined exposure of ELF magnetic fields and x-rays increased mutant yields compared with x-rays alone in pTN89 plasmids med./bio.

By: Koyama S, Nakahara T, Sakurai T, Komatsubara Y, Isozumi Y, Miyakoshi J
Published in: J Radiat Res 2005; 46 (2): 257-264
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Aim of study (acc. to author)

The authors have studied mutations in the supF gene carried by pTN89 plasmids in Escherichia coli to examine the effects of extremely low frequency magnetic fields and/or X-rays (10 Gy) to the plasmids.

Background/further details

For the combined treatments, exposure to the extremely low frequency magnetic fields was immediately before or after X-radiation. The plasmid DNAs were exposed and then tranformed into Escherichia coli (by electroporation).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 60 Hz
Exposure duration: continuous for 16 h

General information

The samples were subjected to the following treatments: Exposure to magnetic field, irradiated to X-rays at 10 Gy (8 Gy/min), exposure to magnetic field either before or after being irradiated with X-rays and control treatment in which neither exposure nor irradiation took place.

Exposure 1

Main characteristics
Frequency 60 Hz
Type
Waveform
  • unspecified
Exposure duration continuous for 16 h
Exposure setup
Exposure source
Chamber CO2 incubator with a built-in coil system. The incubator was maintained at 37°C
Additional info Control was performed in a conventional incubator shielded internally and externally by silicon steel and Permally C, respectively and kept in a separate room.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 5 mT unspecified unspecified - -

Reference articles

  • Miyakoshi J et al. (1994): A newly designed experimental system for exposure of mammalian cells to extremely low frequency magnetic fields

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The mutant fractions were 0.94 x 105 for X-rays alone, 1.58 x 105 for an extremely low frequency magnetic fields followed by X-rays, and 3.64 x 105 for X-rays followed by an extremely low frequency magnetic fields. Increased mutant fraction was not revealed following exposure to a magnetic field alone, or after sham exposure. The mutant fraction for X-rays followed by an extremely low frequency magnetic fields was significantly higher than those of other treatments.
Sequence analysis of the supF mutant plasmids revealed that base substitutions were dominant on exposure to X-rays alone and X-rays + an extremely low frequency magnetic field. Several types of deletions were found only in the combined treatments, but not with X-rays alone.
The authors could not find any mutant colonies in sham-exposed and in extremely low frequency magnetic fields alone treatment, but exposure to extremely low frequency magnetic fields immediately before or after X-radiation may enhance the mutations. The data indicate that an extremely low frequency magnetic field increases mutation and alters the spectrum of mutations.

Study character:

Study funded by

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