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.     

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.     

Longevity and food consumption of microwave-treated (2.45 GHz Cw) honeybees in the laboratory

Adult honeybees, confined singly or in small clusters, were exposed for 0.5, 6, and 24 hours to 2.45-GHz continuous wave microwave radiation at power densities of 3, 6, 12, 25, and 50 mW/cm². Following exposure, bees were held in the incubator for 21 days to determine the consumption of sucrose syrup and to observe mortality. No significant differences were found between microwave-treated and sham-treated or control bees.     

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.     

Studies on microwave and blood-brain barrier interaction

This investigation was aimed at correlating changes of blood-brain-barrier permeability with the quantity and distribution of absorbed microwave energy inside the brain of adult Wistar rats anesthetized by sodium pentobarbital. Through use of thermographic methods and a direct-contact applicator at the animal's head, the pattern of absorbed microwave energy was determined. Indwelling catheters were placed in the femoral vein and in the left external carotid artery. Evans blue and sodium fluorescein in isotonic saline were used as visual indicators of barrier permeation. Exposure to pulsed 2,450-MHz radiation for 20 min at average power densities of 0.5, 1, 5, 20, 145 or 1,000 mW/cm², which resulted in average specific absorption rates (SARs) of 0.04, 0.08, 0.4, 1.6, 11.5 or 80.0 mW/g in the brain, did not produce staining, except in the pineal body, the pituitary gland, and the choroid plexus — regions that normally are highly permeable. Except for these regions, staining was also absent in the brains of sham-exposed animals. The rectal temperature, as monitored by a copper-constantan thermocouple, showed a maximum increase of less than 0.75°C from a mean pre-exposure temperature of 36.6°C. The highest brain temperature recorded in a similar group of animals using a thickfilm carbon thermistor was less than 41.0°C.     

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.     

In vitro study of microwave effects on calcium efflux in rat brain tissue

In this study we investigated the prospect of microwave-induced alteration of ⁴⁵Ca²⁺ efflux from rat neural tissue at low pulse repetition frequencies and low power densities under in vitro conditions. Rat cerebral tissue, preloaded with ⁴⁵Ca²⁺, was exposed to pulsed-microwave radiation (1-GHz carrier frequency) according to one of several PRF-power density exposure schemes: 16 Hz at 0.5, 1.0, 2.0, or 15 mW/cm², or 32 Hz at 1.0 or 2.0 mW/cm² average power density. Measurements of radioactivity in the efflux medium and in the tissue sample were used to calculate an efflux value for each sample. The results indicate that the radiation conditions used did not alter calcium efflux in rat brain tissue.     

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.     

Flight,orientation, and homing abilities of honeybees following exposure to 2.45-GHz CW microwaves

Foraging-experienced honeybees retained normal flight, orientation, and memory functions after 30 minutes' exposure to 2.45-GHz CW microwaves at power densities from 3 to 50 mW/cm². These experiments were conducted at power densities approximating and exceeding those that would be present above receiving antennas of the proposed solar power satellite (SPS) energy transmission system and for a duration exceeding that which honeybees living outside a rectenna might be expected to spend within the rectenna on individual foraging trips. There was no evidence that airborne invertebrates would be significantly affected during transient passage through microwaves associated with SPS ground-based microwave receiving stations.     

Myo-inositol transport through the blood-brain barrier

The unidirectional transport of [³H]myo-inositol across cerebral capillaries, the anatomical locus of the blood-brain barrier, was measured using an in situ rat brain perfusion technique. Myo-inositol was transported across the blood-brain barrier by a low capacity, saturable system with a one-half saturation concentration of 0.1 mM. The permeability surface-area product was 6.2×10^–5S^–1 with a myo-inositol concentration of 0.02 mM in the perfusate. The myo-inositol stereoisomer scyllo-inositol but not (+)-chiro-inositol (both 1 mM) inhibited myo-inositol transfer through the blood-brain barrier. These observations provide evidence that myo-inositol is transferred through the blood-brain barrier by simple diffusion and a stereospecific, saturable transport system.     

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.     

The influence of low power microwave on the properties of DPPC vesicles

The effect of microwave exposure on liposome at non-thermal level are studied. Dipalmitoyl phosphatidylcholine (DPPC) liposomes were exposed to 950 MHz at power densities of 2.5 mW/cm², which is equivalent to specific absorption rate (SAR) of 0.238 W/K. The interaction of microwave with liposomes was investigated by membrane solubilization measurements using a non-ionic detergent, octylglucoside (OG), as well as Fourier transform infrared (FTIR) spectroscopy and flow activation energy measurements. The amount of detergent needed to completely solubilize the liposomal membrane was increased after exposure of liposomes to microwave irradiation, indicating an increased membrane resistance to the detergent and hence a change in the natural membrane permeation properties. In the analysis of FTIR spectra the symmetric and antisymmetric CH₂ (at 2070 cm^?1) band and the CO (at 1640 cm^?1) stretching bands were investigated after liposomal exposure to microwave irradiation. It is clearly shown from the flow activation energy measurements, that low-power microwave induce changes in the liposomes deformability (decreases the liposome fluidity and increases the liposome rigidity). Finally it could be concluded that low-power microwave of 950 MHz induced structural and functional changes in liposomes as a membrane model system.     

Effect of chronic microwave radiation on T cell-mediated immunity in the rabbit

Experiments were conducted to elucidate the effects of chronic low power-level microwave radiation on the immunological systems of rabbits. Fourteen male Belgian white rabbits were exposed to microwave radiation at 5 mW/cm², 2.1 GHz, 3 h daily, 6 days/week for 3 months in two batches of 7 each in specially designed miniature anechoicchambers. Seven rabbits were subjected to sham exposure for identical duration. The microwave energy was provided through S band standard gain horns connected to a 4K3SJ2 Klystron power amplifier. The first batch of animals were assessed for T lymphocyte-mediated cellular immune response mechanisms and the second batch of animals for B lymphocyte-mediated humoral immune response mechanisms. The peripheral blood samples collected monthly during microwave/sham exposure and during follow-up (5/14 days after termination of exposures, in the second batch animals only) were analysed for T lymphocyte numbers and their mitogen responsiveness to ConA and PHA. Significant suppression of T lymphocyte numbers was noted in the microwave group at 2 months (P<0.01, % 21.5%) and during follow-up (P<0.01, % 30.2%). The first batch animals were initially sensitised with BCG and challenged with tuberculin (0.03 ml) at the termination of microwave irradiation/sham exposure and the increase in foot pad thickness ( mm), which is a measure of T cell-mediated immunity (delayed type hypersensitivity response, DTH) was noted in both the groups. The microwave group revealed a better response than the control group (%+12.4 vs.+7.54). The animals were sacrified and the tissue T lymphocyte counts (spleen and lymph node) were analysed. No significant variation was observed in the tissue T lymphocyte counts of microwave-irradiated rabbits. From these results it is speculated that the T lymphocytes are sequestered to various lymphoid organs under the influence of microwaves. A sub-population of T cells known as T helper cells (mediating DTH response) are probably not affected by microwave radiation. It is clear from our experiments that although chronic microwave radiation at 5 mW/cm² leads to suppression of peripheral T lymphocyte numbers, there is no concomitant functional impairment of these cells as evidenced by functional assays.     

Thermal action of 2.45 GHz microwaves on the cytoplasm of Chinese hamster cells

In order to demonstrate possible specific effects of microwaves at the cellular level V-79 Chinese hamster cells were exposed to 2.45-GHz radiation at power levels of 20–200 mW/cm² and at specific absorption rates of 10–100 mW/g. Intracellular cytoplasmic changes were observed by fluorescence polarization using a method based on the intracellular enzymatic hydrolysis of nonfluorescent fluorescein diacetate (FDA). At levels of absorbed energy below 90 J/g, modifications of microviscosity and mitochondrial state were absent, but a slight stimulation of enzymatic hydrolysis of FDA was observed which may be explained by microwave-induced alterations of cellular membranes possibly due to differences in heating pattern of microwaves compared to water-bath heating. At levels of absorbed energy above 90 J/g, the decrease of enzymatic hydrolysis of FDA, increase in degree of polarization, and increase of permeation of the fluorescent marker correlated well with the decrease in cell viability as measured by the exclusion of trypan blue. At equal absorbed energy, microwaves were found to exert effects comparable to classical heating except that permeation was slightly more affected by microwave than by classical heating. This suggests that membrane alteration produced by microwaves might differ from those induced by classical heating or that microwaves may have heated the membrane to higher temperatures than did classical heating.     

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)     

Japanese encephalitis virus (JEV): potentiation of lethality in mice by microwave radiation.

The expression of Japanese Encephalitis Virus (JEV) lethality in mice requires entry of the virus into the central nervous system. This entry is presumably through the capillary endothelial cells (CEC), because entry between CECs is inhibited by bands of circumferential tight-junctions. A viremic stage occurs during the first 4 to 5 days after JEV administration in mice, and both microwave radiation (2.45-GHz, continuous wave, 10-min exposure) and hypercarbia were employed to increase CEC permeability to JEV. Exposure to microwaves at power densities of 10-50 mW/cm2 resulted in a dose-dependent increase in JEV-induced lethality. Mice did not become tolerant or sensitized to microwave potentiation of JEV-induced mortality because 4 daily exposures at 10 or 50 mW/cm2 (SARS, approximately 24-98 W/kg) did not alter the lethality pattern to subsequent microwave radiation of JEV-exposed animals. Similarly, hypercarbia (5, 10, and 20% CO2) was observed to produce a dose-dependent increase in JEV-induced lethality. Both microwave radiation and hypercarbia are thought to promote pinocytosis in CNS capillary endothelial cells. This may be one mechanism by which they enhance JEV-induced lethality in adult Swiss-Cox mice.     

Toroidal inhomogeneity of plasma density fluctuations during ECR plasma heating in the L-2M stellarator

Correlation between short-wavelength (k_⊥ ≈ 20–30 cm^–1) and long-wavelength (k_⊥ ≈ 1–2 cm^–1) plasma density fluctuations in two poloidal cross sections of the stellarator chamber separated by 1/14 or 5/14 of the torus perimeter was studied using collective scattering of radiation of two 75-GHz gyrotrons and radiation of a 37-GHz Doppler reflectometer at an ECR heating power density of 1.6–3.2 MW/m³. It is found that excitation of turbulent fluctuations is bursty in character and that fluctuations excited in different L-2M cross sections are uncorrelated. It is shown that the energy of turbulent fluctuations is modulated by a low frequency of 5–20 kHz. An idea is put forward that anomalous transport is toroidally inhomogeneous.     

Hypoxanthine transport through the blood-brain barrier

The unidirectional influx of hypoxanthine across cerebral capillaries, the anatomical locus of the blood=brain barrier, was measured with an in situ rat brain perfusion technique employing [³H]hypoxanthine. Hypoxanthine was transported across the blood-brain barrier by a saturable system with a one-half saturation concentration of approximately 0.4 mM. The permeability-surface area product was 3×10^–4 sec^–1 with a hypoxanthine concentration of 0.02 M in the perfusate. Adenine (4 mM) and uracil and theophylline (both 10 mM), but not inosine (10 mM) or leucine (1 mM), inhibited hypoxanthine transfer through the blood-brain barrier. Thus, hypoxanthine is transported through the blood-brain barrier by a high-capacity, saturable transport system with a half-saturation concentration about 100 times the plasma hypoxanthine concentration. Although involved in the transport hypoxanthine from blood into brain, this system is not powerful enough to transfer important quantities of hypoxanthine from blood into brain.     

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.     

Humoral and cell-mediated immune function in adult japanese quail following exposure to 2.45-GHz microwave radiation during embryogeny

Japanese quail, Coturnix coturnix japonica, eggs were subjected to 2.45-GHz CW microwave radiation at 5 mW/cm² (SAR = 4.03 mW/g) during the first 12 days of embryogeny. Following hatching the exposed embryos, as well as nonexposed controls, were reared to 22 weeks of age. Humoral immune potential, as indicated by comparable anti-CRBC antibody, IgM and IgG, levels at 0, 4, and 7 days postimmunization in both exposed and control quail was not affected significantly. However, cell-mediated immune potential, measured by the reaction to intradermal injection of phytohemagglutinin-P in the wing web, was reduced in the exposed females, but not in the exposed males. Additionally, total leukocyte numbers and absolute circulating numbers of lymphocytes, monocytes, and heterophils were increased significantly only in the exposed females. These data show that exposure of Japanese quail during embryogenesis reduced cell-mediated immune potential and induced a general leukocytosis in females.