Study type: Medical/biological study (experimental study)

Effects of weak amplitude-modulated microwave fields on calcium efflux from awake cat cerebral cortex med./bio.

By: Adey WR, Bawin SM, Lawrence AF
Published in: Bioelectromagnetics 1982; 3 (3): 295-307
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Aim of study (acc. to author)

To investigate possible changes of a microwave exposure on calcium efflux in cat cerebral cortex.

Background/further details

Cats were exposed in vivo to 450 MHz, sinusoidally modulated at 16 Hz for 60 minutes.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 450 MHz
Modulation type: AM
Exposure duration: continuous for 60 min

Exposure 1

Main characteristics
Frequency 450 MHz
Type
Exposure duration continuous for 60 min
Additional info semi-far field conditions in a low standing-wave field (SWR < 1.2:1 when unperturbed)
Modulation
Modulation type AM
Modulation frequency 16 Hz
Modulation depth 85 %
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.
Setup Anesthetized cats were oriented at right angles to the incident field, with the cortex of the right cerebral hemisphere being exposed.
Sham exposure A sham exposure was conducted.
Additional info Field exposure was initiated at different times (80 to 120 min) after completion of 45Ca2+ incubation of the cortex.
Parameters
Measurand Value Type Method Mass Remarks
power density 3 mW/cm² - measured - -
electric field strength 106 V/m - measured - in air
electric field strength 33 V/m mean measured - in the brain
SAR 0.29 W/kg mean measured - in the brain
Measurement and calculation details

Depth of modulation was monitored with an oscilloscope and with an inline modulation meter/forward power meter. Field levels in the empty exposure chamber were measured using a commercial field intensity probe and an experimental triple dipole probe. Tissue field levels were measured in separate studies using an implantable BRH probe placed between the cerebral hemispheres at two sites 1 cm apart and averaged over three rotations by 120°. Dosimetry was performed with cats oriented transversely to the field but also with the body oriented longitudinally in the field, thus yielding substantially higher results.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Calcium efflux curves obtained from exposed animals were disrupted by irregular peaks of increased calcium efflux as compared with controls. Initiation of exposure was followed by an increased CO2 level in exhaled air for about 5 min in about 70% of cases. However, increased calcium efflux could not be induced by artificial hypercapnia.

Study character:

Study funded by

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