Vibration as a possible explanation for putative electromagnetic field effects: a case study on marine diatoms.
OBJECTIVE
We examined the conjecture that mechanical vibration, being an uncontrolled and variable factor from one trial to another, might explain the inconsistency of results from investigations of the influence of extremely low frequency electromagnetic fields on the Ca-dependent motility of marine diatoms (Amphora coffeaeformis, strain #2038).


METHODS
Owing to slight differences in culture of diatoms in previous studies, culture techniques are described in detail here. Diatoms showed maximal motility in logarithmic growth and motility was dependent on external [Ca], reducing at <.25 mM added Ca. Ninety-six different vertical vibration treatments were applied to the petri dishes containing the agar on which the diatoms were placed. The envelope of amplitudes varied from 50-500 pmicro at 10Hz to 100 nm-l1mmicro at 500 Hz.


RESULTS
No significant effect of the mechanical vibrations on the motility response of diatoms was observed. We were unable to impose deliberate vibrations in a horizontal direction though some component of horizontal movement was probably present in our tests.


CONCLUSIONS
The results imply that the variability of earlier experiments with extremely low frequency electromagnetic fields is unlikely to be ascribable to mechanical vibration.
Davies
M S
MS
Integrative Biology Group, Darwin Building, University of Sunderland, Sunderland, SR1 3SD, UK. mark.davies@sunderland.ac.uk
Norris
W T
WT
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D017377:Diatoms / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D009068:Movement / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D013997:Time Factors; D014732:Vibration
D015220:Calcium Channels; D002118:Calcium