Comparative effects of extremely high power microwave pulses and a brief CW irradiation on pacemaker function in isolated frog heart slices

Abstract

The existence of specific bioeffects due to high peak power microwaves and their potential health hazards are among the most debated but least explored problems in microwave biology. The present study attempted to reveal such effects by comparing the bioeffects of short trains of extremely high power microwave pulses (EHPP, 1 μs width, 250–350 kW/g, 9.2 GHz) with those of relatively low power pulses (LPP, 0.5–10 s width, 3–30 W/g, 9.2 GHz). EHPP train duration and average power were made equal to those of an LPP; therefore both exposure modalities produced the same temperature rise. Bioeffects were studied in isolated, spontaneously beating slices of the frog heart. In most cases, a single EHPP train or LPP immediately decreased the inter‐beat interval (IBI). The effect was proportional to microwave heating, fully reversible, and easily reproducible. The magnitude and time course of EHPP‐ and LPP‐induced changes always were the same. No delayed or irreversible effects of irradiation were observed. The same effect could be repeated in a single preparation numerous times with no signs of adaptation, sensitization, lasting functional alteration, or damage. A qualitatively different effect, namely, a temporary arrest of preparation beats, could be observed when microwave heating exceeded physiologically tolerable limits. This effect also did not depend on whether the critical temperature rise was produced by LPP or EHPP exposure. Within the studied limits, we found no indications of EHPP‐specific bioeffects. EHPP‐ and LPP‐induced changes in the pacemaker rhythm of isolated frog heart preparation were identical and could be entirely attributed to microwave heating. Bioelectromagnetics 21:245–254, 2000. © 2000 Wiley‐Liss, Inc.

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“…For brain slicing procedure only, NaCl was substituted with an equimolar amount of sucrose and ACSF was chilled to about 0 '"C. One slice at a time was transferred into an exposure chamber and set at its bottom. The exposure chamber design was principally the same as described before Pakhomov et al, 2000b], with modifications that enabled adequate life support for brain slices and stable electrophysiological recording. The chamber was mounted atop a waveguide flange; the waveguide opening was sealed with a sapphire matching plate, flush with the flange.…”

“…The few studies that have explored peak SAR levels of 0.1-60 NfW/kg in animals and in vitro, have produced isolated, sometimes contradictory, and generally inconclusive data [see for review Lu and DeLorge, 2000;Pakhomov et al, 2000b]. The data on EHPP bioeffects at still higher peak SAR (100 MW/kg and higher) are even more scarce: aside from our …”

“…While the proliferation rate has no specific link to human disease or health haziirds, it is a convenient integrative index that has been widely used in microwave studies [Anderstam et al, 1983; Grundler and Kaiser, 1992; Gos et al, 1997]. Published data regarding EHPP bioeffects were recently summarized and discussed [Pakhomov et al, 2000b; see also .In short, current knowledge about EHPP bioeffects and potential health hazards is very limited. The few studies that have explored EHPP bioeffects at peak SAR levels over 1 MW/kg have produced isolated, sometimes contradictory, and generally inconclusive data.…”

“…These studies claimed profound EHPP-specific (nonthermal) effects, including changes in the growth rate and metabolism of alga cultures [Tambiev et al, 1989]; stimulation of the immune system, suppression of tumor growth in vivo and in vitro ; and inhibition of a fungus Fusarium growth, induction of developmental aberrations, imago death, and infertility in Drosophila flies [Bolsbakov et al, 2000a,b]. These studies, however, could have suffered various flaws, both in biological experiment protocols and dosimetiy , thus requiring confirmation for the findings.Our previous studies explored EHPP effects in isolated, spontaneously beating frog heart slices [Pakhomov et al, 1999[Pakhomov et al, , 2000b and in gel suspended yeast cells . All observed effects were consistent with the thermal paradigm and provided no proof of EHPP-specific effects.…”

“…While the proliferation rate has no specific link to human disease or health haziirds, it is a convenient integrative index that has been widely used in microwave studies [Anderstam et al, 1983; Grundler and Kaiser, 1992; Gos et al, 1997]. Published data regarding EHPP bioeffects were recently summarized and discussed [Pakhomov et al, 2000b; see also .…”