title: Role of modulation on the effect of microwaves on ornithine decarboxylase activity in L929 cells.
abstract: The effect of 835 MHz microwaves on the activity of ornithine decarboxylase (ODC) in L929 murine cell was investigated at an SAR of approximately 2.5 W/kg. The results depended upon the type of modulation employed. AM frequencies of 16 Hz and 60 Hz produced a transient increase in ODC activity that reached a peak at 8 h of exposure and returned to control levels after 24 h of exposure. In this case, ODC was increased by a maximum of 90% relative to control levels. A 40% increase in ODC activity was also observed after 8 h of exposure with a typical signal from a TDMA digital cellular telephone operating in the middle of its transmission frequency range (approximately 840 MHz). This signal was burst modulated at 50 Hz, with approximately 30% duty cycle. By contrast, 8 h exposure with 835 MHz microwaves amplitude modulated with speech produced no significant change in ODC activity. Further investigations, with 8 h of exposure to AM microwaves, as a function of modulation frequency, revealed that the response is frequency dependent, decreasing sharply at 6 Hz an 600 Hz. Exposure with 835 MHz microwaves, frequency modulated with a 60 Hz sinusoid, yielded no significant enhancement in ODC activity for exposure times ranging between 2 and 24 h. Similarly, exposure with a typical signal from an AMPS analog cellular telephone, which uses a form of frequency modulation, produced no significant enhancement in ODC activity. Exposure with 835 MHz continuous wave microwaves produced no effects for exposure times between 2 and 24 h, except for a small but statistically significant enhancement in ODC activity after 6 h of exposure. Comparison of these results suggests that effects are much more robust when the modulation causes low-frequency periodic changes in the amplitude of the microwave carrier.
authors.affiliation: Department of Biology, Catholic University of America, Washington, DC, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Penafiel
authors.forename: T
authors.initials: T
authors.lastname: Litovitz
authors.forename: D
authors.initials: D
authors.lastname: Krause
authors.forename: A
authors.initials: A
authors.lastname: Desta
authors.forename: J M
authors.initials: JM
authors.lastname: Mullins
mesh_terms: D000818:Animals; D002460:Cell Line; D015194:Diffusion Chambers, Culture; D004574:Electromagnetic Fields / Q000009:adverse effects; D004781:Environmental Exposure / Q000009:adverse effects; D004789:Enzyme Activation / Q000528:radiation effects; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D051379:Mice; D008872:Microwaves / Q000009:adverse effects*; D009955:Ornithine Decarboxylase / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects*; D011846:Radio Waves / Q000009:adverse effects; D015398:Signal Transduction / Q000528:radiation effects; D013689:Telephone
chemical_list: D009955:Ornithine Decarboxylase