In initial in vitro studies, C3H 10T1/2 cells were exposed to an 835 MHz TDMA signal at 0.78, and 7.8 uW/g for up to 4 hours in a TEM cell with a 20 minute on / 20 minute off repeating cycle. Exposures followed induction of growth activity by a change of media (from serum free conditions). Initially, at the highest SAR level ODC activity was inhibited 50% after 3 and 4 hours (opposite the results reported by Penafiel et al., 1997, Bioelectro-magnetics 18:132-141 where murine L929 fibroblasts showed a 50% increase in ODC activity following an 8 hour exposure at a relatively high SAR - 2.5 W/kg). However, the Penafel et al studies were not looking at exposure following ODC induction by change of media. Importantly, in the present study the sham control C3H 10T1/2 cells in the high SAR study did not respond to serum induction as in the low SAR study or in reported sham-sham experiments in the paper. Also, similar studies using C6 glioma cells did not show any effect on ODC activity as compared to sham controls.