Study type: Medical/biological study (experimental study)

The role of coherence time in the effect of microwaves on ornithine decarboxylase activity med./bio.

Published in: Bioelectromagnetics 1993; 14 (5): 395-403

Aim of study (acc. to author and editor)

To investigate the effects of extremely low frequency amplitude modulated microwaves on the activity of the ornithine decarboxylase enzyme (catalyses the reaction of ornithine into putrescine and CO2) in dependence of so-called coherence time. Coherence time here is used in the meaning of a defined time interval over which frequency, phase, and amplitude of the field can be reasonably predicted.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 915 MHz
Modulation type: AM
Exposure duration: continuous for 8 h
Exposure 2: 915 MHz
Modulation type: AM
Exposure duration: continuous for 8 h
Exposure 3: 915 MHz
Modulation type: AM
Exposure duration: continuous for 2-24 h
Exposure 4: 915 MHz
Modulation type: CW
Exposure duration: continuous for 8 h

Exposure 1

Main characteristics
Frequency 915 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 8 h
Modulation
Modulation type AM
Modulation frequency 55–65 Hz
Modulation depth 23 %
Additional info

The modulation signal was periodically switched between 55 and 65 Hz. The operating time for each frequency was selected as a fixed period τ (between 0.1 and 50 s) and a random period Δτ (between 0 and 50 ms).

Exposure setup
Exposure source
Chamber A Crawford cell was placed in an incubator chamber maintained at 37°C. The Crawford cell was mounted vertically on a rotary table and provided with an access door to facilitate sample insertion.
Setup Two tissue culture flasks (25 cm², 50 ml) were placed end to end on each side of the center conductor parallel to the EF and perpendicular to the direction of propagation. Four control flasks were placed in the same incubator at the same height as the exposed cultures.
Additional info A double stub tuner was used to match the impedance of the loaded Crawford cell. Due to the size of the flasks, the ideal uniform exposure configuration could not be achieved. From 5 to 12 separate experiments were performed for each exposure condition (frequency, and coherence time in random order).
Parameters
Measurand Value Type Method Mass Remarks
power 0.96 W - - - -
electric field strength 0.7 V/cm - calculated - -
SAR 2.5 W/kg spatial average measured - -

Exposure 2

Main characteristics
Frequency 915 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 8 h
Modulation
Modulation type AM
Modulation frequency 55–65 Hz
Modulation depth 23 %
Additional info

AM at 55, 60, or 65 Hz

Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
power 0.96 W - - - -
electric field strength 0.7 V/cm - calculated - -
SAR 2.5 W/kg spatial average measured - -

Exposure 3

Main characteristics
Frequency 915 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 2-24 h
Modulation
Modulation type AM
Modulation frequency 60 Hz
Modulation depth 23 %
Exposure setup
Exposure source
Additional info SARs of 0.5 W/kg or a modulation index of 60% were also tested.
Parameters
Measurand Value Type Method Mass Remarks
power 0.96 W - - - -
electric field strength 0.7 V/cm - calculated - -
SAR 2.5 W/kg spatial average measured - -

Exposure 4

Main characteristics
Frequency 915 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 8 h
Modulation
Modulation type CW
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
power 0.96 W - - - -
electric field strength 0.7 V/cm - calculated - -
SAR 2.5 W/kg spatial average measured - -

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The activity of ornithine decarboxylase in cells exposed to unmodulated microwaves was found not to be altered. The enzyme activity was enhanced approximately two-fold in cells exposed to modulated microwaves at all frequencies used but only for coherence times greater than 10 seconds. Up to now the way how amplitude modulated microwaves affect cells still remains unknown.

Study character:

Study funded by

Replication studies

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