Role of modulation on the effect of microwaves on ornithine decarboxylase activity in L929 cells

✍ Scribed by L. Miguel Penafiel; Theodore Litovitz; David Krause; Abiy Desta; J. Michael Mullins

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 111 KB
• Volume: 18
• Category: Article
• ISSN: 0197-8462
• DOI: 10.1002/(sici)1521-186x(1997)18:2<132::aid-bem6>3.0.co;2-3

✦ Synopsis

The effect of 835 MHz microwaves on the activity of ornithine decarboxylase (ODC) in L929 murine cells was investigated at an SAR of Ç2.5 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 (Ç840 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 and 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.