Effects of 2.45-GHz microwave radiation on embryonic quail hearts

Although exposure to nonionizing electromagnetic radiation has been reported to cause a variety of systemic alterations during embryonic development, there are few reports of the induction of specific physiologic or morphologic changes in the myocardium. This study was designed to examine the effects of microwave radiation on cardiogenesis in Japanese quail embryos exposed during the first eight days of development to 2.45-GHz continuous-wave microwaves at power densities of 5 or 20 mW/cm². The specific absorption rates were 4.0 and 16.2 mW/g, respectively. The ambient temperature for each exposure was set to maintain the embryonated eggs at 37.5 °C. This did not preclude thermal gradients in the irradiated embryos since microwaves may not be uniformly absorbed. The test exposure levels did not induce changes in either the morphology of the embryonic heart or the ultrastructure of the myocardial cells. Analysis of the enzymatic activities of lactate dehydrogenase, glutamic oxaloacetic transaminase, and creatine phosphokinase failed to reveal any statistically significant differences between the nonexposed controls and those groups exposed to either 5 or 20 mW/cm². The data indicate that 2.45-GHz microwave radiation at 5 or 20 mW/cm² has no effect on the measured variables of the Japanese quail myocardium exposed during the first eight days of development.     

The in vivo effects of 2.45 GHz microwave radiation on rabbit serum components and sleeping times

Summary An investigation was conducted to determine the effects of relatively low power density microwave exposures on various serum components of the Dutch rabbit. Both continuous wave and pulsed mode exposures at 2.45 GHz were used at power densities of 25, 10 and 5 mW/cm². Studies of 10 serum components were performed. Additional studies were conducted on changes in sleeping times of pentobarbital-sedated rabbits at various power densities. Gross and histopathological examinations were performed on representative samples of animals.Changes in the blood chemistry of irradiated animals were consistent with a dose-dependent response to a non-specific thermal stress at all power densities used. Observed physiological response, as well as rectal temperature measurements, indicated that the thermoregulatory capability of the rabbits was sufficient to compensate for the thermal burden at 5 and 10 mW/cm², but could be overridden by a 2 h exposure at 25 mW/cm². Pathology findings included a mild, repairable nephrosis in animals exposed at a power density of 25 mW/cm².A further investigation of analeptic effects at power densities varying from 5 mW/cm² to 50 mW/cm² resulted in a statistically significant decrease in sleeping times, apparently proportional to power density below 15 mW/cm².This research was partially supported by the US Army Medical Research and Development Command, Contract No. DADA17-72-C-2144. (The views expressed are those of the authors and do not necessarily reflect those of the Department of the Army)     

Microwave effects on energy metabolism of rat brain

Rat brain was exposed to 591-MHz, continuous-wave (CW) microwaves at 13.8 or 5.0 mW/cm² to determine the effect on nicotinamide adenine dinucleotide, reduced (NADH), adenosine triphosphate (ATP) and creatine phosphate (CP) levels. On initiation of the in vivo microwave exposures, fluorimetrically determined NADH rapidly increased to a maximum of 4.0%–12.5% above pre-exposure control levels at one-half minute, then decreased slowly to 2% above control at three minutes, finally increasing slowly to 5% above control level at five minutes. ATP and CP assays were performed on sham- and microwave-exposed brain at each exposure time. At 13.8 mW/cm², brain CP level was decreased an average of 39.4%, 41.1%, 18.2%, 13.1%, and 36.4% of control at exposure points one-half, one, two three, and five minutes, respectively, and brain ATP concentration was decreased an average of 25.2%, 15.2%, 17.8%, 7.4%, and 11.2% of control at the corresponding exposure periods. ATP and CP levels of rat brain exposed to 591-MHz cw microwaves at 5 mW/cm² for one-half and one minute were decreased significantly below control levels at these exposure times, but were not significantly different from the 13.8 mW/cm² exposures. For all exposures, rectal temperature remained constant. Heat loss through the skull aperture caused brain temperature to decrease during the five-minute exposures. This decrease was the same in magnitude for experimental and control subjects. Changes in NADH, ATP, and CP levels during microwave exposure cannot be attributed to general tissue hyperthermia. The data support the hypothesis that microwave exposure inhibits mitochondrial electron transport chain function, which results in decreased ATP and CP levels in brain.     

Evaluation of the Potential In Vitro Antiproliferative Effects of Millimeter Waves at Some Therapeutic Frequencies on RPMI 7932 Human Skin Malignant Melanoma Cells

The potential antiproliferative effects of low power millimeter waves (MMWs) at 42.20 and 53.57 GHz on RPMI 7932 human skin melanoma cells were evaluated in vitro in order to ascertain if these two frequencies, comprised in the range of frequency used in millimeter wave therapy, would have a similar effect when applied in vivo to malignant melanoma tumours. Cells were exposed for 1 h exposure/day and to repeated exposure up to a total of four treatments. Plane wave incident power densities <1 mW/cm² were used in the MMWs-exposure experiments so that the radiations did not cause significant thermal effects. Numerical simulations of Petri dish reflectivity were made using the equations for the reflection coefficient of a multilayered system. Such analysis showed that the power densities transmitted into the aqueous samples were ≤0.3 mW/cm². Two very important and general biological endpoints were evaluated in order to study the response of melanoma cells to these radiations, i.e. cell proliferation and cell cycle. Herein, we show that neither cell doubling time nor the cell cycle of RPMI 7932 cells was affected by the frequency of the GHz radiation and duration of the exposure, in the conditions above reported.     

Modification of the repeated acquisition of response sequences in rats by low-level microwave exposure

The acute effects of microwave exposure on a repeated acquisition baseline were investigated in three rats. Each session the animals acquired a different four-member response sequence. Each of the first three correct responses advanced the sequence to the next member, and the fourth correct response produced food reinforcement. Incorrect responses produced a three-second timeout. Baseline and control sessions were characterized by a decrease in errors within each session. The animals were acutely exposed to a 2.8 GHz pulsed-microwave field prior to test sessions, with average power densities ranging from 0.25 to 10 mW/cm². In comparison to control sessions, 1/2 hour of exposure to microwave radiation at power densities of 5 and 10 mW/cm² increased errors and altered the pattern of within-session acquisition. Exposure to the 10 mW/cm² power density decreased the rate of sequence completion in all animals. The results of exposures at 0.25, 0.5, and 1 mW/cm² power densities were generally within the control range. The results are interpreted as indicating a disruption in the discriminative stimulus control of the repeated acquisition behavior.     

HIF-1α/ERK通路活化调控微波长期辐射致大鼠海马神经元线粒体损伤

本文旨在探讨微波辐射致大鼠海马神经元线粒体损伤中HIF-1α和ERK通路分子表达的改变及意义,为深入研究微波辐射损伤机制和防治提供新靶标.2.5,5和10mW/cm2的微波辐射100只雄性Wistar大鼠,辐射时间为6min/次,5次/周,连续辐射1月,于辐射后6h,7d,14d,1周和2月,采用Real-timePCR,Westernblot和免疫组织化学检测海马中hif-1αmRNA,HIF-1α,ERK1/2和p-ERK1/2表达.结果发现,大鼠海马hif-1αmRNA和HIF-1α蛋白分别在2.5和5mW/cm2组于辐射后14d和1月明显增加,10mW/cm2组辐射后14d～2月降低.但海马ERK1/2未见明显改变.假辐射组p-ERK1/2于海马神经元胞浆中呈弱阳性,2.5mW/cm2组p-ERK1/2表达无明显变化,5和10mW/cm2辐射后7d～1月,p-ERK1/2于海马神经元胞浆和胞核中呈阳性或强阳性.2.5,5和10mW/cm2微波长期辐射后大鼠海马HIF-1α和p-ERK1/2表达的改变,表明HIF-1α和ERK通路活化参与微波辐射致海马线粒体损伤的过程,并可能发挥修复线粒体损伤的作用.     

Electrokinetic and Biochemical Changes in Erythrocytes under the Action of Terahertz Range Electromagnetic Waves

The effects of electromagnetic radiation of a gyrotron with an operating frequency of 263 GHz on rat erythrocyte electrophoretic mobility, malonic dialdehyde, ATP, and 2,3-diphosphoglycerate concentration have been studied in vitro. The blood was irradiated under continuous and pulsed gyrotron emission modes with the estimated incident energy flux on an object from 0.1 to 20 mW/cm². It has been established that the studied erythrocyte characteristics changed in different directions depending on the mode and the incident energy flux: the erythrocyte electrophoretic mobility rate and ATP concentration decreased, while the malonic dialdehyde and 2,3-diphosphoglycerate concentration increased at a low incident energy flux and continuous exposure mode; all studied parameters increased under the pulsed exposure mode. An incident energy flux increase caused a reduction of these effects.     

Microwave absorption by magnetic nanoparticles in the organism

An estimate is presented for the rate of microwave absorption by magnetic nanoparticles in the organism. The absorption takes place because of energy dissipation at ferromagnetic resonance. Based on the known solution of the Landau-Lifshits equation, the imaginary part of complex susceptibility is evaluated, which gives the absorption rate. It is shown that even under thermal isolation of the particles, their heating would be insignificant upon absorption of radiation with an energy flux density on the order of 1 mW/cm², and such a mechanism is unrelated to the observable effects of low-intensity microwaves.     

Effects of microwave and radio frequency electromagnetic fields on lichens

The effects of electromagnetic fields on lichens were investigated. Field experiments of long duration (1–3 years) were combined with laboratory experiments and theoretical considerations. Samples of the lichen species Parmelia tiliacea and Hypogymnia physodes were exposed to microwaves (2.45 GHz; 0.2, 5, and 50 m W/cm²; and control). Both species showed a substantially reduced growth rate at 50 m W/cm². A differentiation between thermal and nonthermal effects was not possible. Temperature measurements on lichens exposed to microwaves (2.45 GHz, 50 m W/cm²) showed a substantial increase in the surface temperature and an accelerated drying process. The thermal effect of microwave on lichens was verified. The exposure of lichens of both species was repeated near a short-wave broadcast transmitter (9.5 MHz, amplitude modulated; maximum field strength 235 V/m, 332 mA/m). No visible effects on the exposed lichens were detected. At this frequency, no thermal effects were expected, and the experimental results support this hypothesis. Theoretical estimates based on climatic data and literature showed that the growth reductions in the initial experiments could very likely have been caused by drying of the lichens from the heating with microwaves. The results of the other experiments support the hypothesis that the response of the lichens exposed to microwaves was mainly due to thermal effects and that there is a low probability of nonthermal effects. © 1996 Wiley-Liss, Inc.     

Effects of Microwave Exposure at Various Power Densities on Mitochondrial Marker Enzymes in Mouse Brains

Four groups of C₅₇BL mice were irradiated with 3 GHz pulse (PW) microwaves for 3 hours at incident power densities of 0.1, 0.5, 1 and 5 mW/cm² respectively. The amount of mitochondria1 marker enzymes succinate dehydrogenase (SDH) and monoamine oxidase (MAO) in the hypothalamus and hippocampus were determined by microspectrophotometry. SDH and MA0 in the irradiated groups (except 0.1 mW/cm²) were significantly lower compared to the control group (p < 0.01). The lowest level occurred in the 5 mW/cm² group. The threshold level was 0.5 mW/cm². To compare the effects of PW with continuous wave (CW) exposure, two experimental groups were exosed to 2.45 GHz, using CW; the enzymes were decreased only in the 5 mW/cm² group. The results show that PW radiation is more effective then CW radiation in decreasing SDH and MA0 levels.     

Immunologic and hematopoietic alterations by 2,450-MHz electromagnetic radiation

A biphasic modulation of responsiveness of spleen lymphocytes to mitogens was observed in mice exposed to 2,450-MHz radiation at power densities of 5–15 mW/cm² over various periods ranging between one and 17 days. This modulated phenomenon may be explained on the basis of 1) suppression of lymphocyte response by microwave-activated macrophages which persists throughout the entire course of radiation, and 2) concurrent progressive direct stimulation of lymphocytes which culminates around day 9 of exposure. Tumor cytotoxicity of killer lymphocytes from mice exposed to five or nine days of radiation did not appear different from sham controls. The highly proliferative hematopoietic marrow cells were sensitive to microwave radiation. Nine days of exposure to radiation (15 mW/cm²) reduced the colonyforming units of myeloid and erythroid series by 50%. This observation may offer a new and more sensitive assay for studying biological effects of electromagnetic radiation.     

Millimeter wave effects on electrical responses of the sural nerve in vivo

Millimeter wave (MMW, 42.25 GHz)‐induced changes in electrical activity of the murine sural nerve were studied in vivo using external electrode recordings. MMW were applied to the receptive field of the sural nerve in the hind paw. We found two types of responses of the sural nerve to MMW exposure. First, MMW exposure at the incident power density ≥45 mW/cm² inhibited the spontaneous electrical activity. Exposure with lower intensities (10–30 mW/cm²) produced no detectable changes in the firing rate. Second, the nerve responded to the cessation of MMW exposure with a transient increase in the firing rate. The effect lasted 20–40 s. The threshold intensity for this effect was 160 mW/cm². Radiant heat exposure reproduced only the inhibitory effect of MMW but not the transient excitatory response. Depletion of mast cells by compound 48/80 eliminated the transient response of the nerve. It was suggested that the cold sensitive fibers were responsible for the inhibitory effect of MMW and radiant heat exposures. However, the receptors and mechanisms involved in inducing the transient response to MMW exposure are not clear. The hypothesis of mast cell involvement was discussed. Bioelectromagnetics 31:180–190, 2010. © 2009 Wiley‐Liss, Inc.     

Effects of Pulsed Microwave Radiation Pre -and Post-Natally on the Developing Brain in Mice

Pregnant mice were irradiated for 5 hours daily throughout the pregnancy with pulsed microwaves at an incident average power density of 8 mW/cm², or were sham irradiated. After birth, from day 3 to day 20, half the offspring delivered by irradiated mice were irradiated (RR group) and half were sham-irradiated (RC group). The same procedure was used for offspring delivered by sham-irradiated mice (CR and CC). All offspring were sacrificed at 22 days of age. Histochemical analyses of the hypothalamus and liver were performed with a microspectrophotometer. The data suggested that succinate dehydrogenase in the hypothalamus was reduced by either pre-or post-natal microwave exposure. Similar changes occurred in the liver. The same pattern appeared with hypothalamic catechol-amine and monoamine oxidase. The data indicate that low-intensity microwave exposure can induce subtle alterations in offspring not detected with previously used techniques.     

Comparative effects of pulsed and continuous-wave 2.8-GHz microwaves on temporally defined behavior

The effects of pulsed-(PW) and continuous-wave (CW) 2.8-GHz microwaves were compared on the performance of rodents maintained by a temporally defined schedule of positive reinforcement. The schedule involved food-pellet reinforcement of behavior according to a differential-reinforcement-of-low-rate (DRL) contingency. The rats were independently exposed to PW and to CW fields at power densities ranging from 1 to 15 mW/cm². Alterations of normal performance were more pronounced after a 30-minute exposure to the PW field than to the CW field. The rate of emission of appropriately timed responses declined after exposure to PW at 10 and 15 mW/cm², whereas exposure at the same power levels to the CW field did not consistently affect the rate of responding. Change in performance associated with microwave exposure was not necessarily related to a general decline in responding: in some instances, increases in overall rates of responding were observed.     

Millimeter Wave Radiation Activates Leech Nociceptors via TRPV1-Like Receptor Sensitization

There is evidence that millimeter waves (MMWs) can have an impact on cellular function, including neurons. Earlier in vitro studies have shown that exposure levels well below the recommended safe limit of 1 mW/cm² cause changes in the action potential (AP) firing rate, resting potential, and AP pulse shape of sensory neurons in leech preparations as well as alter neuronal properties in rat cortical brain slices; these effects differ from changes induced by direct heating. In this article, we compare the responses of thermosensitive primary nociceptors of the medicinal leech under thermal heating and MMW irradiation (80–170 mW/cm² at 60 GHz). The results show that MMW exposure causes an almost twofold decrease in the threshold for activation of the AP compared with thermal heating (3.9 ± 0.4 vs. 8.3 ± 0.4 mV, respectively). Our analysis suggests that MMWs-mediated threshold alterations are not caused by the enhancement of voltage-gated sodium and potassium conductance. We propose that the reduction in AP threshold can be attributed to the sensitization of the transient receptor potential vanilloid 1-like receptor in the leech nociceptor. In silico modeling supported our experimental findings. Our results provide evidence that MMW exposure stimulates specific receptor responses that differ from direct thermal heating, fostering the need for additional studies.     

Chronic exposure of rabbits to 0.5 and 5 mW/cm2 2450-MHz CW Microwave Radiation

Two groups of 16 male New Zealand rabbits were exposed to 2450-MHz continuous wave microwave fields in two experiments of 90 days each. The incident power densities of the first and second experiment were 0.5 and 5 mW/cm², respectively. During each study, 16 animals were adapted to a miniature anechoic chamber exposure system for at least 2 weeks, then 8 of them were exposed for 7 h daily, 5 days a week for 13 weeks, and the other 8 animals were sham exposed. The rabbits were placed in acrylic cages, and each was exposed from the top in an individual miniature anechoic chamber. Thermography showed a maximum specific absorption rate of 5.5 W/kg in the head and 7 W/kg in the back at 5-mW/cm² incident power density. After each 7-h exposure session, the animals were returned to their home cages. Food consumption in the exposure chamber and body mass were measured daily. Blood samples were taken before exposure and monthly thereafter for hematological, morphological, chemical, protein electrophoresis, and lymphocyte blast transformation studies. Eyes were examined for cataract formation. Finally, pathological examinations of 28 specimens of organs and tissues of each rabbit were performed. Statistically, there was a significant (P < .01) decrease only of food consumption during the 5-mW/cm² exposure; other variables were not significantly different between exposed and control groups.     

Microwave Facilitation of Methylnaltrexone Antagonism of Morphine-Induced Analgesia in Mice

Exposure to low dose microwave irradiation has been postulated to influence effects of centrally active pharmacological agents. In this investigation, the analgesic dose, 50% (ADSO) for morphine in the mouse tail flick test was significantly increased by pretreatment with the centrally active opiate receptor blocker naltrexone, and the dose-response curve ms shifted significantly to the right. On the other hand, the AD50 and dose-response curve for morphine were not influenced by either the peripherally active opiate receptor blocker methylnaltrexone alone or microwave irradiation (2.45 GHz, 20 mW/cm², CW, 10 min) alone. However, following both methylnaltrexone pretreatment and microwave exposure, there was both a significant increase in the AD50 as well as a significant rightward shift of the dose-response curve, indicating a competitive antagonism of morphine by methylnaltrexone. One possible explanation for this microwave-drug interaction is that microwave energy might facilitate entry of methylnaltrexone into the central nervous system.     

Microwaves modify thermoregulatory behavior in squirrel monkey

Squirrel monkeys (Saimiri sciureus) trained to regulate environmental temperature (T_a) behaviorally were exposed in the far field of a horn antenna to ten-minute periods of 2,450 MH_z CW microwaves. Incident power density ranged from 1 to 22 mW/cm². The corresponding specific absorption rate (SAR), derived from temperature increments in saline-filled styrofoam models, ranged from 0.15 to 3.25 W/kg. Controls included exposure to infrared radiation of equivalent incident energy and no radiation exposure. Normal thermoregulatory behavior produces tight control over environmental and body temperatures; most monkeys select a T_a of 34–36°C. Ten-minute exposures to 2,450 MH_z CW microwaves at an incident power density of 6–8 mW/cm² stimulated all animals to select a lower T_a. This threshold energy represents a whole-body SAR of 1.1 W/kg, about 20% of the resting metabolic rate of the monkey. Thermoregulatory behavior was highly efficient, and skin and rectal temperatures remained stable, even at 22 mW/cm² where the preferred T_a was lowered by as much as 4°C. No comparable reduction in selected T_a below control levels occurred during exposure to infrared radiation of equal incident power density.     

In vitro microwave effects on human neutrophil precursor cells (CFU-C)

Human marrow cells were irradiated with 2450-MHz CW microwaves in a fluid-filled waveguide irradiation system. Cell exposure was conducted by placing a marrow cell suspension in 20-μl glass microcapillary tubes that were positioned in the exposure chamber, and irradiated at power densities from 31 to 1,000 mW/cm² (with corresponding specific absorption rates of 62 to 2,000 mW/g) for 15 minutes. The temperature of the sample was maintained at a fixed point. Sham-irradiated (SI) and microwave-irradiated (MWI) cells were cultured in a methylcellulose culture system for neutrophil colony proliferation. There was no reduction in neutrophil colony number on days 6–7 or 12–14 in cells exposed at 31 or 62 mW/cm², but as the power density was increased to 1,000 mW/cm², there was a reduction in colony number of MWI cells compared with SI cells. The microwave interaction with the human neutrophil colony-forming cells was apparently not related to temperature rise, or to the state of cell cycle, and was irreversible.     

Effects of millimeter-wave radiation on monolayer cell cultures. III. A search for frequency-specific athermal biological effects on protein synthesis

A method recently developed in this laboratory has been used to directly expose BHK-21/C13 cells to high levels of microwave radiation without significant microwave-induced heating (? 0.1 °C). Monolayer cultures were grown on microwave-transparent polystyrene coverslips, placed on the open end of a wave guide, and maintained at 37.2 °C during irradiation at frequencies in both the E- and U-bands (average power densities 292 and 177 mW/cm², respectively). Effects of microwave radiation were assessed at 0.1 GHz increments in the ranges of 38–48 GHz and 65–75 GHz. Protein synthesis was measured in quadruplicate cultures that were allowed to incorporate labeled methionine during the 15-minute period of microwave irradiation. Autoradiographs of each monolayer culture were scanned along the region corresponding to the longer axis of the wave guide aperture using a microdensitometer to quantify incorporation. Since microwave power incident on the cells was previously shown to vary along this axis according to a cosine² relationship from zero at each edge of the wave guide to twice the average power density at the center of the wave guide, this technique should reveal biological effects that might only be manifested in narrow amplitude domains or “power windows.” Observations of protein synthesis in monolayer cultures irradiated at 202 closely spaced frequencies in the E- and U-bands failed to reveal changes associated with microwave exposure. Thus no evidence was obtained in support of the existence of frequency-specific athermal biological effects of microwaves. In addition, no support was found for the existence of amplitude-specific “power windows”.