DNA synthesis and cell proliferation in C6 glioma and primary glial cells exposed to a 836.55 MHz modulated radiofrequency field

We have tested the hypothesis that modulated radiofrequency (RF) fields may act as a tumor-promoting agent by altering DNA synthesis, leading to increased cell proliferation. In vitro tissue cultures of transformed and normal rat glial cells were exposed to an 836.55 MHz, packet-modulated RF field at three power densities: 0.09, 0.9, and 9 mW/cm², resulting in specific absorption rates (SARs) ranging from 0.15 to 59 μW/g. TEM-mode transmission-line cells were powered by a prototype time-domain multiple-access (TDMA) transmitter that conforms to the North American digital cellular telephone standard. One sham and one energized TEM cell were placed in standard incubators maintained at 37 °C and 5% CO₂. DNA synthesis experiments at 0.59–59 μW/g SAR were performed on log-phase and serum-starved semiquiescent cultures after 24 h exposure. Cell growth at 0.15–15 μW/g SAR was determined by cell counts of log-phase cultures on days 0, 1, 5, 7, 9, 12, and 14 of a 2 week protocol. Results from the DNA synthesis assays differed for the two cell types. Sham-exposed and RF-exposed cultures of primary rat glial cells showed no significant differences for either log-phase or serum-starved condition. C₆ glioma cells exposed to RF at 5.9 μW/g SAR (0.9 mW/cm²) exhibited small (20–40%) significant increases in 38% of [³H]thymidine incorporation experiments. Growth curves of sham and RF-exposed cultures showed no differences in either normal or transformed glial cells at any of the power densities tested. Cell doubling times of C₆ glioma cells [sham (21.9 ± 1.4 h) vs. field (22.7 ± 3.2 h)] also demonstrated no significant differences that could be attributed to altered DNA synthesis rates. Under these conditions, this modulated RF field did not increase cell proliferation of normal or transformed cultures of glial origin. Bioelectromagnetics 18:230–236, 1997. © 1997 Wiley-Liss, Inc.     

Lack of effect of 2.45-GHz microwave radiation on the development of preimplantation embryos of mice

The development of preimplantation embryos after exposure to microwave radiation was studied. Female CD-1 mice were induced to superovulate, mated, and exposed to 2.45-GHz microwave or sham radiation for 3 h at power densities of 9 mW/cm² and 19 mW/cm² on either day 2 or 3 of pregnancy (plug day was considered day 1). Another group of mice was exposed to heat stress by placing the dams in an environmental room at an ambient temperature of 38 °C and relative humidity at 62% for 3 h on day 2 of pregnancy. All groups were euthanized on day 4 of pregnancy and embryos were recovered by flushing excised uterine horns. Embryos were examined for abnormalities and classified by the developmental stages. They were then treated with hypotonic solution and dissociated for counting blastomeres. Heat stress caused stunted development of embryos, but no remarkable effect of microwave radiation could be found on the development of preimplantation embryos.     

The Effect of Combined Exposure of 900 MHz Radiofrequency Fields and Doxorubicin in HL-60 Cells

Human promyelocytic leukemia HL-60 cells were pre-exposed to non-ionizing 900 MHz radiofrequency fields (RF) at 12 µW/cm² power density for 1 hour/day for 3 days and then treated with a chemotherapeutic drug, doxorubicin (DOX, 0.125 mg/L). Several end-points related to toxicity, viz., viability, apoptosis, mitochondrial membrane potential (MMP), intracellular free calcium (Ca²⁺) and Ca²⁺-Mg²⁺ -ATPase activity were measured. The results obtained in un-exposed and sham-exposed control cells were compared with those exposed to RF alone, DOX alone and RF+DOX. The results indicated no significant differences between un-exposed, sham-exposed control cells and those exposed to RF alone while treatment with DOX alone showed a significant decrease in viability, increased apoptosis, decreased MMP, increased Ca²⁺ and decreased Ca²⁺-Mg^2+-ATPase activity. When the latter results were compared with cells exposed RF+DOX, the data showed increased cell proliferation, decreased apoptosis, increased MMP, decreased Ca²⁺ and increased Ca²⁺-Mg²⁺-ATPase activity. Thus, RF pre-exposure appear to protect the HL-60 cells from the toxic effects of subsequent treatment with DOX. These observations were similar to our earlier data which suggested that pre-exposure of mice to 900 MHz RF at 120 µW/cm² power density for 1 hours/day for 14 days had a protective effect in hematopoietic tissue damage induced by subsequent gamma-irradiation.     

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)     

Thermophysiological responses of human volunteers during controlled whole-body radio frequency exposure at 450 MHz

Thermoregulatory responses of heat production and heat loss were measured in seven adult volunteers (four women and three men, aged 21–57 yr) during 45-min dorsal exposures of the whole body to 450 MHz continuous wave radio frequency (RF) fields. Two power densities (PD) (local peak PD = 18 and 24 mW/cm²; local peak specific absorption rate = 0.320 [W/kg]/[mW/cm²]) were tested in each of three ambient temperatures (T_a = 24, 28, and 31 °C) plus T_a controls (no RF). No changes in metabolic heat production occurred under any exposure conditions. Vigorous increases in sweating rate on back and chest, directly related to both T_a and PD, cooled the skin and ensured efficient regulation of the deep body (esophageal) temperature to within 0.1 °C of the normal level. Category judgments of thermal sensation, comfort, sweating, and thermal preference usually matched the measured changes in physiological responses. Some subtle effects related to gender were noted that confirm classic physiological data. Our results indicate that dorsal exposures of humans to a supra-resonant frequency of 450 MHz at local peak specific absorption rates up to 7.68 W/kg are mildly thermogenic and are counteracted efficiently by normal thermophysiologic heat loss mechanisms, principally sweating. Bioelectromagnetics 19:232–245, 1998. Published 1998 Wiley-Liss, Inc.     

Near-field dosimetry for in vitro exposure of human cells at 60 GHz

Due to the expected mass deployment of millimeter‐wave wireless technologies, thresholds of potential millimeter‐wave‐induced biological and health effects should be carefully assessed. The main purpose of this study is to propose, optimize, and characterize a near‐field exposure configuration allowing illumination of cells in vitro at 60 GHz with power densities up to several tens of mW/cm². Positioning of a tissue culture plate containing cells has been optimized in the near‐field of a standard horn antenna operating at 60 GHz. The optimal position corresponds to the maximal mean‐to‐peak specific absorption rate (SAR) ratio over the cell monolayer, allowing the achievement of power densities up to 50 mW/cm² at least. Three complementary parameters have been determined and analyzed for the exposed cells, namely the power density, SAR, and temperature dynamics. The incident power density and SAR have been computed using the finite‐difference time‐domain (FDTD) method. The temperature dynamics at different locations inside the culture medium are measured and analyzed for various power densities. Local SAR, determined based on the initial rate of temperature rise, is in a good agreement with the computed SAR (maximal difference of 5%). For the optimized exposure setup configuration, 73% of cells are located within the ±3 dB region with respect to the average SAR. It is shown that under the considered exposure conditions, the maximal power density, local SAR, and temperature increments equal 57 mW/cm², 1.4 kW/kg, and 6 °C, respectively, for the radiated power of 425 mW. Bioelectromagnetics 33:55–64, 2012. © 2011 Wiley Periodicals, Inc.     

See the light: Electrophysiological characterization of the Bolwig organ's light response of Calliphora vicina 3rd instar larvae

The anatomy and development of the larval cyclorraphous Diptera visual system is well established. It consists of the internal Bolwig organ (BO), and the associated nerve connecting it to the brain. The BO contributes to various larval behaviors but was never electrophysiologically characterized. We recorded extracellulary from the Bolwig nerve of 3rd instar Calliphora vicina larvae to quantify the sensory response caused by BO stimulation with light stimuli of different wavelengths, intensities and directions. Consistent with previous behavioral experiments we found the BO most sensitive to white and green, followed by blue, yellow, violet and red light. The BO showed a phasic-tonic response curve. Increasing light intensity produced a sigmoid response curve with an approximate threshold of 0.0105 nW/cm² and a dynamic range from 0.105 nW/cm² to 52.5 nW/cm². No differences exist between feeding and wandering larvae which display opposed phototaxis. This excludes reduced BO sensitivity from causing the switch in behavior. Correlating to the morphology of the BO frontal light evoked the maximal reaction, while lateral light reduced the neural response asymmetrically: Light applied ipsilaterally to the recorded BO always produced a stronger response than when applied from the contralateral side. This implies that phototacic behavior is based on a tropotactic mechanism.     

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.     

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.     

Accelerated development of spontaneous and benzopyrene-induced skin cancer in mice exposed to 2450-MHz microwave radiation

C₃H/HeA mice with high incidence of spontaneous breast cancer and Balb/c mice treated with 3,4-benzopyrene (BP) (by painting of the skin resulting in the development of skin cancer) were irradiated with 2,450-MHz microwaves (MW) in an anechoic chamber at 5 or 15 mW/cm² (2 h daily, 6 sessions per week). C₃H/HeA mice were irradiated from the 6th week of life, up to the 12th month of life. Balb/c mice treated with BP were irradiated either prior to (over 1 or 3 months) or simultaneously with BP treatment (over 5 months). The appearance of palpable tumors in C₃H/HeA mice and of skin cancer in BP-treated Balb/c mice was checked every 2 weeks for 12 months. Two additional groups of mice were exposed to chronic stress caused by confinement or to sham-irradiation in an anechoic chamber; these served as controls. Irradiation with MWs at either 5 or 15 mW/cm² for 3 months resulted in a significant lowering of natural antineoplastic resistance (mean number of lung neoplastic colonies was 2.8 ± 1.6 (SD) in controls, 6.1 ± 1.8 in mice exposed at 5 mW/cm² and 10.8 ± 2.1 in those irradiated at 15 mW/cm²) and acceleration of development of BP-induced skin cancer (285 days in controls, 230 days for 5 mW/cm² and 160 days for 15 mW/cm²). Microwave-exposed C₃H/HeA mice developed breast tumors earlier than controls (322 days in controls, 261 days for 5 mW/cm² and 219 days for 15 mW/cm²). A similar acceleration was observed in the development of BP-induced skin cancer in mice exposed simultaneously to BP and MWs (285 days in controls, 220 day for 5 mW/cm² and 121 days for 15 mW/cm²). The acceleration of cancer development in all tested systems and lowering of natural antineoplastic resistance was similar in mice exposed to MW at 5 mW/cm² or to chronic stress caused by confinement but differed significantly from the data obtained on animals exposed at 15 mW/cm², where local thermal effects (“hot” spots) were possible.     

Calcium-ion efflux from brain tissue: Power-density versus internal field-intensity dependencies at 50-MHz RF radiation

In previous experiments changes were found in calcium-ion efflux from chickbrain tissue that had been exposed in vitro to 147-MHz radiation across a specific range of power densities when the field was amplitude modulated at 16 Hz. In the present study, 50-MHz radiation, similarly modulated as a sinusoid, was found to produce changes in calcium-ion efflux from chick brains exposed in vitro in a Crawford cell. Exposure conditions were optimized to broaden any power-density window and to enhance the opportunity to detect changes in the calcium-ion efflux. The results of a power-density series demonstrated two effective ranges: One spanning a range from 1.44 to 1.67 mW/cm², and the other including 3.64 mW/cm², which were bracketed by no-effect results at 0.72, 2.17, and 4.32 mW/cm². Peaks of positive findings are associated with near-identical rates of energy absorption: 1.4 μW/g at 147 MHz, and 1.3 μW/g at 50 MHz, which indicates that the enhanced-efflux phenomenon is more dependent on the intensity of fields in the brain than on the power density of incident radiation. In addition, the phenomenon appears to occur at multiples of some, as yet unknown, rate of radiofrequency (RF) energy absorption. Because of the extremely small increments of temperature associated with positive findings (< 4 × 10^?4°C), and the existence of more than one productive absorption rate, a solely thermal explanation appears extremely unlikely.     

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.     

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.     

Operant behavior and colonic temperature of Macaca mulatta exposed to radio frequency fields at and above resonant frequencies

Five food-deprived rhesus monkeys were exposed to 225-MHz continuous-wave, and 1.3-GHz, and 5.8-GHz pulsed radiation to determine the minimal power densities affecting performance. The monkeys were trained to press a lever (observing-response) thereby producing signals that indicated availability of food. In the presence of the aperiodically appearing food signals, a detection response on a different lever was reinforced by a food pellet. Continuous, stable responding during 60-min sessions developed and was followed by repeated exposures to radiofrequency radiation. The subjects, restrained in a Styrofoam chair, were exposed to free-field radiation while performing the task. Colonic temperature was simultaneously obtained. Observing-response performance was impaired at increasingly higher power densities as frequency increased from the near-resonance 225 MHz to the above-resonance 5.8 GHz. The threshold power density of disrupted response rate at 225 MHz was 8.1 mW/cm²; at 1.3 GHz it was 57 mW/cm², and at 5.8 GHz it was 140 mW/cm². These power densities were associated with reliable increases in colonic temperatures above sham-exposure levels. The mean increase was typically in the range of 1°C, and response-rate changes were not observed in the absence of concomitant temperature increases. In these experiments increase of colonic temperature was a much better predictor of behavioral disruption than was either the power density of the incident field or estimates of whole-body-averaged rates of energy absorption.     

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 survival of amphibian embryos after continuous ultrasonic treatment

The effect of continuous ultrasonic treatment on the development of early embryos of common frog Rana temporaria was studied. Intact embryos at the blastula stage were exposed to ultrasound of various frequencies (0.88 and 2.64 MHz) and intensities (0.05 to 1.0 W/cm²) for various periods (1 to 15 min). The increase in ultrasound intensity to 0.7–1.0 W/cm² and exposure time to 5–15 min resulted in nearly complete mortality. Development of the embryos exposed to ultrasound of medium intensity (0.2–0.7 W/cm²) for 1–5 min was virtually similar to the control. Treatment at a frequency of 2.64 MHz and intensity of 0.05–0.7 W/cm² for 1–5 min had no effect on the development of amphibian embryos and their survival rate. The increase in intensity of the ultrasound of this frequency to 1 W/cm² and the exposure time to 5 min decreased the number of normally developing embryos by 35%.     

Emission spectra of a cherenkov plasma relativistic maser

The spectra of a plasma relativistic maser are measured. It is shown that the microwave frequency can be varied from 4 to 28 GHz by varying the plasma density from 4×10¹² to 7×10¹³ cm^?3 at a power of 30–50 MW. The relative width of the emission spectrum is within 50–80% for low plasma densities and 15–30% for high densities. Experimental results are compared with calculations.     

Extremely high frequency electromagnetic fields at low power density do not affect the division of exponential phase Saccharomyces cerevisiae cells

Exponentially growing cells of the yeast Saccharomyces cerevisiae were exposed to electromagnetic fields in the frequency range from 41.682 GHz to 41.710 GHz in 2 MHz increments at low power densities (0.5 μW/cm² and 50 μW/cm²) to observe possible nonthermal effects on the division of this microorganism. The electronic setup was carefully designed and tested to allow precise determination and stability of the electromagnetic field parameters as well as to minimize possible effects of external sources. Two identical test chambers were constructed in one exposure system to perform concurrent control and test experiments at every frequency step under well-controlled exposure conditions. Division of cells was assessed via time-lapse photography. Control experiments showed that the cells were dividing at submaximal rates, ensuring the possibility of observing either an increase or a decrease of the division rate. The data from several independent series of exposure experiments and from control experiments show no consistently significant differences between exposed and unexposed cells. This is in contrast to previous studies claiming nonthermal effects of electromagnetic fields in this frequency range on the division of S. cerevisiae cells. Possible reasons for this difference are discussed. Bioelectromagnetics 18:142–155, 1997. © 1997 Wiley-Liss, Inc.     

Thresholds of microwave-evoked warmth sensations in human skin

We measured thresholds for microwave-evoked skin sensations of warmth at frequencies of 2.45, 7.5, 10, 35, and 94 GHz. In the same subjects, thresholds of warmth evoked by infrared radiation (IR) were also measured for comparison. Detection thresholds were measured on the skin in the middle of the back in 15 adult male human subjects at all microwave (MW) frequencies and with IR. Long duration (10-s), large area (327-cm²) stimuli were used to minimize any differential effects of temporal or spatial summation. Sensitivity increased monotonically with frequency throughout the range of microwave frequencies tested. The threshold at 94 GHz (4.5 ± 0.6 mW/cm²) was more than an order of magnitude less than at 2.45 GHz (63.1 ± 6.7 mW/cm²), and it was comparable to the threshold for IR (5.34 ± 1.07 mW/cm²). Bioelectromagnetics 18:403–409, 1997. © 1997 Wiley-Liss, Inc.     

Mechanical resistance by an ectorganic soil layer on root development of seedling Pinus sylvestris

We investigated early root development of Pinus sylvestris seedlings in relation to bulk density and natural particle layering in an ectorganic soil layer from a bracken (Pteridium aquilinum) stand. Responses in root development to two levels of bulk density (0.07 and 0.15 g/cm³) in mixed bracken substrate were compared with effects in peat of similar bulk densities, and in sand of three different bulk densities (0.37, 0.52, and 0.67 g/cm³). The effect on root growth of the natural horizontal layering of the organic particles was examined by comparing intact with mixed ectorganic bracken soil profiles of similar bulk densities (resp. 0.09 and 0.07 g/cm³).Root length growth was significantly reduced in the organic and sandy substrates of high bulk density. Root diameter was not affected by bulk density in the organic substrate, but increased with higher bulk density in sand. Preservation of horizontal layering in the intact ectorganic profile significantly reduced root length compared with mixed substrate of similar bulk density.Roots growing in high bulk density, and intact, organic substrate showed increased twisting, which resulted in a smaller depth reached by the root relative to total root length produced. In sand, root twisting did not change with increased bulk density. It is suggested that roots growing through organic substrate follow a path of least resistance. This implies that organic particle size and orientation are more important in determining root development than bulk density.This study points out that the natural layering of organic particles presents another constraint on the establishment of plant species in sites with a well-developed ectorganic soil layer. Disturbance of this layer may therefore enhance establishment of seedlings by reducing the mechanical resistance of the ectorganic soil profile to developing seedling roots.