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In previous work, we examined factors which influence magnetic-field induced enhancement of ornithine decarboxylase (ODC) activity in L929 fibroblasts. Results from that work indicated that enhancement of ODC activity by a 60-Hz magnetic field is influenced by two, distinct, temporal time constants. These time constants were identified through experiments in which cells were exposed to fields which were periodically turned on and off (gapped) at set intervals throughout exposure. The data obtained were consistent with a system of temporal sensing by which the cells obtain some average of field parameters over intervals of approximately 0.1 s, and then compare current and `remembered' average values. In this hypothesis, cells would initiate a response to the field (i.e., increase ODC activity) if field parameters were determined to be constant over intervals of at least 10 s. In the work reported here, cells were exposed to a constant 60-Hz magnetic field onto which an EM noise field was superimposed with the same periodicity used for introducing gaps in the previous work. The intent of these studies was: (1) To determine whether intermittently superimposed EM noise fields would produce a situation, in terms of cellular response, equivalent to turning off the 60-Hz stimulating field, and; (2) If this were so, to use this system to confirm the time constants of 0.1 and 10 s which were identified in the gapped-field experiments. Cellular response to the intermittently superimposed fields was found to be the same as that for cells exposed to fields which were gapped for the same intervals. ODC enhancement induced by the 60-Hz field was observed when the noise fields were superimposed every other 10 s during exposure, but no enhancement was obtained when noise fields were superimposed every other 1 s. When the noise field was pulsed for brief intervals (50–200 ms), each second during exposure, noise pulses ≥100 ms eliminated an ODC response to the 60-Hz field, but when 50 ms pulses were used some ODC enhancement was observed. Superimposition of the noise field was, thus, shown to be the functional equivalent of turning of the 60-Hz stimulating field, and the time constants revealed by the gapped-field studies were confirmed through the use of superimposed noise pulses. |
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