Study type: Medical/biological study (experimental study)

DNA synthesis and cell proliferation in C6 glioma and primary glial cells exposed to a 836.55 MHz modulated radiofrequency field med./bio.

By: Stagg RB, Thomas WJ, Jones RA, Adey WR
Published in: Bioelectromagnetics 1997; 18 (3): 230-236
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Aim of study (acc. to author)

To examine the effect of TDMA-modulated radiofrequency at 836.55 MHz on DNA synthesis and cell proliferation in tissues of glial origin.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 836.55 MHz
Modulation type: pulsed
Exposure duration: continuous for 4 and 24 h
  • power density: 0.09 mW/cm² cf. remarks (slot average)
  • SAR: 0.59 µW/g cf. remarks (slot average)
  • power density: 0.3 mW/cm² average over time (at 0.9 mW/cm² slot average)
  • power density: 0.9 mW/cm² cf. remarks (slot average)
  • SAR: 5.9 µW/g cf. remarks (± 2.8 µW/g slot average)
  • power density: 9 mW/cm² cf. remarks (slot average)
  • SAR: 59 µW/g cf. remarks (slot average)
Exposure 2: 836.55 MHz
Modulation type: pulsed
Exposure duration: continuous for up to 14 days, see below
  • power density: 0.09 mW/cm² cf. remarks (slot average)
  • SAR: 0.15 µW/g cf. remarks (slot average)
  • power density: 0.3 mW/cm² average over time (at 0.9 mW/cm² slot average)
  • power density: 0.9 mW/cm² cf. remarks (slot average)
  • SAR: 1.5 µW/g cf. remarks (± 1.0 µW/g slot average)
  • power density: 9 mW/cm² cf. remarks (slot average)
  • SAR: 15 µW/g cf. remarks (slot average)

General information

For a complete description of the exposure system used for this study, see Ivaschuk et al. [1997].

Exposure 1

Main characteristics
Frequency 836.55 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 4 and 24 h
Modulation
Modulation type pulsed
Pulse width 6.7 ms
Duty cycle 33 %
Repetition frequency 50 Hz
Additional info

TDMA modulation conforming to the NADC standard
Exposure setup
Exposure source
Chamber Four TEM cells were placed in two standard incubators maintained at 37 °C and 5% CO 2. TEM cells in each location were randomly used for RF and sham exposure.
Setup Cells were exposed in 48-well plates, with one stack of two plates placed on the septum of the TEM cell. The electric field vector was normal to the dishes.
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 0.09 mW/cm² cf. remarks measured - slot average
SAR 0.59 µW/g cf. remarks calculated - slot average
power density 0.3 mW/cm² average over time measured - at 0.9 mW/cm² slot average
power density 0.9 mW/cm² cf. remarks measured - slot average
SAR 5.9 µW/g cf. remarks calculated - ± 2.8 µW/g slot average
power density 9 mW/cm² cf. remarks measured - slot average
SAR 59 µW/g cf. remarks calculated - slot average
Additional parameter details

The local static field, measured with a three-axis fluxgate magnetometer, was 63 ± 10 µT at an inclination of 63° ± 20° relative to the horizontal in one incubator and 31 ± 9 µT at an inclination of 70° ± 17° in the other incubator. The ambient 60 Hz MF, measured with a gaussmeter, was 0.15 ± 0.05 µT, 0.29 ± 0.17 µT, 0.12 ± 0.02 µT, and 0.14 ± 0.09 µT rms at the location of the four TEM cells in the two incubators, respectively.

Measurement and calculation details

Modelling, calculations, and experimental assessment of SAR values of the cell monolayers in both 48-well plates and 60-mm culture dishes were performed in a collaborative study [Burkhardt et al., 1996]. The SAR values were determined in a two-step approach: First, the EMF distribution was mapped using E-field and H-field probes, and then, induced SAR values were numerically assessed for homogeneous exposure. None of the input powers (51 mW, 0.51 W, and 5.1 W slot average) produced a detectable rise in temperature.

Exposure 2

Main characteristics
Frequency 836.55 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for up to 14 days, see below
Modulation
Modulation type pulsed
Pulse width 6.7 ms
Duty cycle 33 %
Repetition frequency 50 Hz
Additional info

TDMA modulation conforming to the NADC standard
Exposure setup
Exposure source
Setup Cells were exposed in 60-mm culture dishes, with two groups of three stacks (three dishes to a stack) placed on the septum and on the bottom of the TEM cell. The electric field vector was normal to the dishes.
Sham exposure A sham exposure was conducted.
Additional info Unfortunately, cell harvesting times have been described and depicted in several inconsistent ways.
Parameters
Measurand Value Type Method Mass Remarks
power density 0.09 mW/cm² cf. remarks measured - slot average
SAR 0.15 µW/g cf. remarks calculated - slot average
power density 0.3 mW/cm² average over time measured - at 0.9 mW/cm² slot average
power density 0.9 mW/cm² cf. remarks measured - slot average
SAR 1.5 µW/g cf. remarks calculated - ± 1.0 µW/g slot average
power density 9 mW/cm² cf. remarks measured - slot average
SAR 15 µW/g cf. remarks calculated - slot average

Reference articles

  • Ivaschuk OI et al. (1997): Exposure of nerve growth factor-treated PC12 rat pheochromocytoma cells to a modulated radiofrequency field at 836.55 MHz: effects on c-jun and c-fos expression
  • Burkhardt M et al. (1996): Numerical and experimental dosimetry of Petri dish exposure setups

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

Increased 3H-thymidine incorporation during acute exposure was observed, but a significant increase in cell numbers in continuously exposed cultures was not observed. DNA synthesis: sham-exposed and radiofrequency (RF)-exposed cultures of primary rat glial cells showed no significant differences. C6 glioma cells exposed to radiofrequency at 5.9 µW/g SAR exhibited small significant (20-40%) increases in 38% of 3H-thymidine incorporation experiments. Growth curves of sham and RF-exposed cultures showed no differences in either normal or transformed glial cells. Cell doubling times of C6 cells also demonstrated no significant differences that could be attributed to altered DNA synthesis rates. Under these conditions, this radiofrequency field did not increase cell proliferation of normal or transformed cultures of glial cells.

Study character:

Study funded by

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