Study type: Medical/biological study (experimental study)

Ionic factors in release of 45Ca2+ from chicken cerebral tissue by electromagnetic fields med./bio.

By: Bawin SM, Adey WR, Sabbot IM
Published in: Proc Natl Acad Sci USA 1978; 75 (12): 6314-6318
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Aim of study (acc. to author)

To investigate the effects of 450 MHz AM modulated radiofrequence exposure on the calcium efflux from chicken brain tissue in combination with bathing solutions of different ionic strength.

Background/further details

The aim of the study was to find a better definition of the calcium sites responding to weak electrical stimulation.
First, changes in calcium efflux were studied in relation to calcium concentration in the medium, because calcium-calcium interactions have often been shown to play an important role in the regulation of calcium uptake and release.
Another approach to differentiating possible components of the 45Ca2+ efflux was to attempt modification of calcium release by adding lanthanum. The trivalent lanthanum ion has been found to be effective in blocking calcium flux across excitable membranes.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 450 MHz
Modulation type: AM
Exposure duration: continuous for 20 min

Exposure 1

Main characteristics
Frequency 450 MHz
Type
Exposure duration continuous for 20 min
Additional info semi-far field conditions in a low standing-wave field (SWR < 1.2:1)
Modulation
Modulation type AM
Modulation frequency 16 Hz
Modulation depth 90 %
Additional info

sinusoidal
Exposure setup
Exposure source
Chamber The horn radiator was lined and terminated with RF-absorbing material to form an anechoic chamber, seven wavelengths long.
Parameters
Measurand Value Type Method Mass Remarks
power density 0.75 mW/cm² - - - -
electric field strength 53 V/m - - - in air
electric field strength 100 mV/cm - measured - 50-100 mV/cm in the tissue
power density 0.375 mW/cm² - - - -
power density 2 mW/cm² - - - -
Additional parameter details

A few comparative studies were made with field powers of 0.375 and 2.0 mW/cm².

Measurement and calculation details

Tissue field gradients were measured using an implantable microdiode array.

Reference articles

  • Sheppard AR et al. (1979): Models of long-range order in cerebral macromolecules: Effects of sub-ELF and of modulated VHF and UHF fields

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

16 Hz AM modulated radiofrequency is capable to stimulate the calcium efflux of pre-incubated isolated chicken brain tissue. Calcium concentration (in the range of 0 - 4.16 mM) in the bathing solution had no significantly effect on calcium efflux, compared with control. Calcium efflux was inhanced by the addition of H+ (HCl (0.108 mM)) and inhibited by the absence of normal bicarbonate levels (2.4 mM HCO3-). The addition of lanthanum (0.5 mM LaCl3) to bicarbonate-free solutions leads to an decreased calcium efflux in irradiated samples.

Study character:

Study funded by

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