| Abstract |
In vitro exposure of chick forebrain tissue to 50-MHz radiofrequency (RF) radiation, amplitude modulated (AM) at 16 Hz, would enhance the efflux of calcium ions only within two power density ranges: one spanning from 1.44 to 1.67 mW/sq cm, and the other including 3.64 mW/sq cm. No-effect results occurred at 0.37, 0.72, 2.17 and 4.32 mW/sq cm. These results were replicated and extended by testing another set of power densities, which included the range of the previous study. Forebrain tissue from 1-7 day-old chickens were labeled in vitro with radioactive calcium ions (30 min, at 37 C), rinsed, placed in a physiological salt solution and exposed for 20 min to 50-MHz radiation, AM at 16 Hz, in a TEM cell maintained at 37 C. The solution was then assayed for radioactive calcium activity. A power density series was tested. Enhanced efflux of calcium ions was found at 1.75, 3.85, 5.57, 6.82, 7.65, 7.77, and 8.82 mW/sq cm; no change was observed at 0.75, 2.30, 4.50, 5.85, 7.08, 8.19, 8.66, 10.6, and 14.7 mW/sq cm. Power density is converted to specific absorption rate by 0.36 mW/kg/mW/sq cm; a value much too low for generalized heating of the sample to be the underlying cause of the response. A hypothetical mechanism is proposed involving dynamical systems that may account for the power density dependency as well as for part of the frequency dependency observed for both modulated RF radiation and for ELF fields. (Copyright (c) 1989 Alan R. Liss, Inc.) |
