Behavioral changes in adult rats exposed to ELF magnetic fields

In two experiments, male rats that had been exposed to an ELF (0.5 Hz), 3–50 gauss rotating magnetic field (RMF) for 21–30 days, displayed significantly (p < 0.05) greater ambulatory behavior (activity) than the control group in an open field test, when removed from the RMF. In a third experiment rats were exposed to a different RMF apparatus (3–30 gauss), and tested in a different open field for longer duration. Again the RMF-exposed group displayed greater activity (p < 0.10) than the control group.

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Zusammenfassung In zwei Untersuchungen zeigten männliche Ratten,die einem ELF (0,5 Hz) 3–50 Gauss rotierenden magnetischen Feld (RMF) für 21–30 Tage ausgesetzt wurden, in einem Open-Field Test signifikant (p < 0,05) mehr Bewegungsaktivität als die Kontrollgruppe,nachdem sie von dem RMF entfernt wurden. In einer dritten Untersuchung wurden Ratten in einem anderen RMF Gerät gehalten und in einem anderen Open-Field für längere Zeit getestet. Wieder zeigte die Gruppe, die dem RMF ausgesetzt war, mehr Bewegungsaktivität (p < 0,10) als die Kontrollgruppe.

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Resume Lors de deux essais, on a placé des rats mâles dans un champ magnétique tournant (CMT) de 3 à 50 gauss et des très basse fréquence (FTB) (0,5 Hz). Après 21 à 30 jours de ce traitement, on les a remis dans des conditions normales. Leur activité (marche) était plus élevée que celle d'un groupe de contrôle et cela de façon significative (p < 0,05). Dans un troisième essai, d'autres rats furent placés dans un autre appareil (3 à 30 gauss) et examinés ensuite dans un autre champ ouvert sur une plus longue période. Le groupe traité a déployé dans ce cas également une plus grande activité qu'un groupe de contrôle (p < 0,10).

     

Auditory response in rats exposed to 2,450 MHz electromagnetic fields in a circularly polarized waveguide

Rats were exposed to 2,450-MHz pulsed microwave fields in a circularly polarized waveguide. The threshold incident energy density per pulse was about 1.5 to 3 microJ/cm2 over the range 1-10 microseconds. The corresponding whole-body averaged specific absorption of energy was 0.9 to 1.8 mJ/kg per pulse. The same response was evoked when the incident energy density or absorbed energy density per pulse was the same, regardless of the pulse widths.     

Cardiovascular response of rats exposed to 60-Hz electric fields

Recently, it has been reported that exposure to high-strength electric fields can influence electrocardiogram (ECG) patterns, heart rates, and blood pressures in various species of animals. Our studies were designed to evaluate these reported effects and to help clarify some of the disagreement present in the literature. Various cardiovascular variables were measured in Sprague-Dawley rats exposed or sham-exposed to 60-Hz electric fields at 80 or 100 kV/m for periods up to four months. No significant differences in heart rates, ECG patterns, blood pressures, or vascular reactivity were observed between exposed and sham-exposed rats after 8 hours, 40 hours, 1 month, or 4 months of exposure. Blood pressure and heart rate measurements, made during exposure to a 100-kV/m electric field for one hour, revealed no significant differences between exposed and sham-exposed groups. In addition, physiologic reserve capacity, measured in rats subjected to low temperature after exposure to 100 kV/m for one month, showed that electric-field exposure had no significant effect on physiological response to cold stress. Our studies cannot be directly compared to the work of other investigators because of differences in animal species and electric-field characteristics. However, our failure to detect any cardiovascular changes may have been the result of 1) eliminating secondary field effects such as shocks, audible noise, corona, and ozone; 2) minimizing steady-state microcurrents between the mouth of the animal and watering devices; and 3) minimizing electric-field-induced vibration of the electrodes and animal cages.     

Attempts to produce taste-aversion learning in rats exposed to 60-Hz electric fields

A measure of taste-aversion (TA) learning was used in three experiments to 1) determine whether exposure to intense 60-Hz electric fields can produce TA learning in male Sprague-Dawley rats, and 2) establish a dose-response function for the behavior in question. In Experiment 1, four groups of eight rats each were distributed into one of two exposures (69 ± 5 kV/m or 133 ± 10 kV/m) or into one of two sham-exposure groups. Conditioning trials paired 0.1% sodium saccharin in water with 3 h of exposure to a 60-Hz electric field. Following five conditioning trials, a 20-min, two-bottle preference test between water and saccharin-flavored water failed to reveal TA conditioning in exposed groups. In Experiment 2, four groups of eight rats each (34 ± 2 kV/m or 133 ± 10 kV/m and two sham-exposed groups) were treated as before. Electric-field exposure had no effect on TA learning. Experiment 3 tested for a possible synergy between a minimal dose (for TA learning) of cyclophosphamide (6 mg/kg) and 5 h of exposure to 133 ± 10 kV/m electric fields in a dark environment under conditions otherwise similar to those of Experiments 1 and 2. The results indicated no TA learning as reflected in the relative consumption of saccharin.     

Reproduction and development in rats chronologically exposed to 60-Hz electric fields

Previous studies have raised the possibility of reproductive and developmental changes in miniature swine chronically exposed to a strong 60-Hz electric field. Two replicate experiments on rats were performed to determine if similar changes could be detected in animals exposed under a comparable regime, which was based on average, induced-current densities and on the chronology of reproductive development, as dosimetrically and biologically scaled. Beginning at three months of age, female rats of the F0 generation and their subsequent offspring were chronically exposed to a 60-Hz electric field (100 kV/m unperturbed) for 19 h/day for the duration of experimentation. After four weeks of exposure, F0 female rats were mated to unexposed male rats during the field-off period. No significant developmental effects were detected in their litters, confirming our previous results with swine and rats. The F0 females were mated for a second time at 7.2 months of age, and the fetuses were evaluated shortly before term. In the first experiments, the incidence of intrauterine mortality was significantly less in exposed than in sham-exposed litters, and there was a tendency (P = .12) for an increased incidence of malformed fetuses in exposed litters. Neither end point was significantly affected in the second experiment. Copulatory behavior of the female F1 offspring, which were bred at three months of age, was not affected in either experiment. There was a statistically significant decrease in the fertility of F1 exposed females and a significant increase in the fraction of exposed litters with malformed fetuses in the first experiment; both end points were essentially the same in the sham and exposed groups of the second experiment. That the significant effects detected in the first experiment were not seen in the second may be attributed to random or biological variation. Alternatively, the finding may indicate that the response threshold for induction of malformations lies near 100 kV/m.     

Hepatic microsomal mixed-function oxidases in rats exposed to high ambient temperature

Exposure of rats for 3 h or 6h to 28 degrees C or 37 degrees C led to changes in mixed-function oxidases in liver microsomes as compared with 21 degrees C. The complex pattern of the behaviour of the activities of aniline hydroxylase, 4-nitroanisole-O-demethylase, aminopyrine N-demethylase and NADH: cytochrome c oxidoreductase was not related to the observed decrease of cytochrome P-450 and cytochrome b5 contents.     

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.     

Hematologic and serum chemistry studies in rats exposed to 60-Hz electric fields

Numerous hematologic and serum chemistry variables were examined in rats exposed to unperturbed 60-Hz electric fields at 100 kV/m for 15, 30, 60, or 120 days. Each study was replicated once. Rigorous statistical evaluations of these data did not detect any consistent effect of the electric field for exposures of up to 120 days. It was, however, not unusual in any individual study to detect certain variables that were significantly different between the exposed and sham-exposed animals. This emphasizes the need for replicate designs and appropriate statistical analyses when investigating chemical or physical insults that may have minimal influence on biologic function.     

Oxidative DNA damage in rats exposed to extremely low frequency electro magnetic fields

Extremely low frequency (ELF) electromagnetic field (EMF) is thought to prolong the life of free radicals and can act as a promoter or co-promoter of cancer. 8-hydroxy-2'-deoxyguanosine (8OHdG) is one of the predominant forms of radical-induced lesions to DNA and is a potential tool to asses the cancer risk. We examined the effects of extremely low frequency electro magnetic field (ELF-EMF) (50 Hz, 0.97 mT) on 8OHdG levels in DNA and thiobarbituric acid reactive substances (TBARS) in plasma. To examine the possible time-dependent changes resulting from magnetic field, 8OHdG and TBARS were quantitated at 50 and 100 days. Our results showed that the exposure to ELF-EMF induced oxidative DNA damage and lipid peroxidation (LPO). The 8OHdG levels of exposed group (4.39+/-0.88 and 5.29+/-1.16 8OHdG/dG.10(5), respectively) were significantly higher than sham group at 50 and 100 days (3.02+/-0.63 and 3.46+/-0.38 8OHdG/dG.10(5)) (p<0.001, p<0.001). The higher TBARS levels were also detected in the exposure group both on 50 and 100 days (p<0.001, p<0.001). In addition, the extent of DNA damage and LPO would depend on the exposure time (p<0.05 and p<0.05). Our data may have important implications for the long-term exposure to ELF-EMF which may cause oxidative DNA damage.     

No apoptosis is induced in rat cortical neurons exposed to GSM phone fields

The aim of this study was to investigate the radiofrequency (RF) electromagnetic fields (EMF) effects on neuronal apoptosis in vitro. Primary cultured neurons from cortices of embryonic Wistar rats were exposed to a 900-MHz global system for mobile communication (GSM) RF field for 24 h in a wire-patch cell. The average-specific absorption rate (SAR) used was 0.25 W/kg. Apoptosis rate was assessed immediately or 24 h after exposure using three methods: (i) DAPI staining; (ii) flow cytometry using double staining with TdT-mediated dUTP nick-end labeling (TUNEL) and propidium iodide (PI); and (iii) measurement of caspase-3 activity by fluorimetry. No statistically significant difference in the apoptosis rate was observed between controls and 24 h GSM-exposed neurons, either 0 h or 24 h post-exposure. All three methods used to assess apoptosis were concordant. These results showed that, under the conditions of experiment used, GSM-exposure does not significantly increase the apoptosis rate in rat primary neuronal cultures. This work is in accordance with other studies performed on cell lines and, to our knowledge, is the first one performed on cultured cortical neurons.     

Neural and behavioral teratological evaluation of rats exposed to ultra-wideband electromagnetic fields

Several investigators have reported teratologic effects of electromagnetic field exposure. The majority of these studies have been performed at levels of exposure that could produce substantial heating of the animals. New and unique sources of ultra-wideband (UWB) electromagnetic fields are currently being developed and tested that are capable of generating nonthermalizing, high-peak-power, microwave (MW) pulses with nanosecond (ns) pulse widths, picosecond (ps) rise times, and an UWB of frequencies. Our study was performed to determine if teratological changes occur in rat pups as a result of (i) daily UWB exposures during gestation days 3-18, or (ii) as a result of both prenatal and postnatal (10 days) exposures. Dams were exposed either to (i) UWB irradiation from a Kentech system that emitted a 55 kV/m-peak E field, 300 ps rise time, and a 1.8 ns pulse width, average whole-body specific absorption rate 45 mW/kg; (ii) sham irradiation; or (iii) a positive control, lead (Pb) acetate solution (2000 microg/ml) continuously available in the drinking water. Offspring were examined for ontogeny (litter size, sex-ratios, weights, coat appearance, tooth-eruption, eye-opening, air-righting, and ultrasonic stress vocalizations). Male pups were tested on various performance measures (locomotor, water-maze learning, and fertilization capabilities). The pups postnatally exposed were examined for hippocampal morphology and operant behavior. Behavioral, functional, and morphological effects of UWB exposure were unremarkable with these exceptions: (i) The UWB-exposed pups emitted significantly more stress vocalizations than the sham-exposed pups; (ii) the medial-to-lateral length of the hippocampus was significantly longer in the UWB-exposed pups than in the sham-exposed animals; (iii) male offspring exposed in utero to UWB mated significantly less frequently than sham-exposed males, but when they did mate there was no difference in fertilization and offspring numbers from the sham group. There does not appear to be a unifying physiological or behavioral relationship among the significant differences observed, and our findings could be due to the expected spurious results derived when a large number of statistical comparisons are made. Significant effects found between our positive-controls and other groups on numerous measures indicates that the techniques used were sensitive enough to detect teratological effects. Bioelectromagnetics 21:524-537, 2000. Published 2000 Wiley-Liss, Inc.     

Failure to produce taste-aversion learning in rats exposed to static electric fields and air ions

Taste-aversion (TA) learning was measured to determine whether exposure to high-voltage direct current (HVdc) static electric fields can produce TA learning in male Long Evans rats. Fifty-six rats were randomly distributed into four groups of 14 rats each. All rats were placed on a 20 min/day drinking schedule for 12 consecutive days prior to receiving five conditioning trials. During the conditioning trials, access to 0.1 % sodium saccharin-flavored water was given for 20 min, followed 30 min later by one of four treatments. Two groups of 14 rats each were individually exposed to static electric fields and air ions, one group to +75 kV/m (+2 × 10⁵ air ions/cm³) and the other group to ?75 kV/m (-2 × 10⁵ air ions/cm³). Two other groups of 14 rats each served as sham-exposed controls, with the following variation in one of the sham-exposed groups: This group was subdivided into two subsets of seven rats each, so that a positive control group could be included to validate the experimental design. The positive control group (n = 7) was injected with cyclophosphamide 25 mg/kg, i.p., 30 min after access to saccharin-flavored water on conditioning days, whereas the other subset of seven rats was similarly injected with an equivalent volume of saline. Access to saccharin-flavored water on conditioning days was followed by the treatments described above and was alternated daily with water “recovery” sessions in which the rats received access to water for 20 min in the home cage without further treatment. Following the last water-recovery session, a 20 min, two-bottle preference test (between water and saccharin-flavored water) was administered to each group. The positive control group did show TA learning, thus validating the experimental protocol. No saccharin-flavored water was consumed in the two-bottle preference test by the cyclophosphamide-injected, sham-exposed group compared to 74% consumed by the saline-injected sham-exposed controls (P <.0001). Saccharin-preference data for the static field-exposed groups showed no TA learning compared to data for sham-exposed controls. In summary, exposure to intense static electric fields and air ions did not produce TA learning as assessed by this particular design. © 1995 Wiley-Liss, Inc.     

Conditioned-reflex food selection in mongrel white rats exposed to high temperature]

Under condition of normal temperature the conditioned reflectory runnings of rats on the audible irritants were developed more quickly during dry food than damp one. Daily influence of high temperature during two hours and partially water deprivation resulted in reduction of the conditioned reflex which had been developed before during dry food. The reproduction of the conditioned reflexes during dry food failed. The essential changings in the conditioned reflexes during damp and dry food were not found when animals had become overheating without restriction of water consumption. During daily heat affecting at the end of the second week animals adapted to high temperature. This statement is confirmed by lowering the rectal temperature, decrease of the breath rate, daily water consumption and restoration of the activity of conditioned reflexes.     

Studies on prenatal and postnatal development in rats exposed to 60-Hz electric fields

A series of three experiments was performed to determine the effects of 30-day exposures to uniform 60-Hz electric fields (100 kV/m) on reproduction and on growth and development in the fetuses and offspring of rats. In the first experiment, exposure of females for 6 days prior to and during the mating period did not affect their reproductive performance, and continued exposure through 20 days of gestation (dg) did not affect the viability, size, or morphology of their fetuses. In the second experiment, exposure of the pregnant rat was begun on 0 dg and continued until the resulting offspring reached 8 days of age. In the third experiment, exposure began at 17 dg and continued through 25 days of postnatal life. In the second and third experiments, no statistically significant differences suggesting impairment of the growth or survival of exposed offspring were detected. In the second experiment, a significantly greater percentage of the exposed offspring showed movement, standing, and grooming at 14 days of age than among-sham-exposed offspring. There was a significant decrease at 14 days in the percentage of exposed offspring displaying the righting reflex in the second experiment and negative geotropism in the third experiment. These differences were all transient and were not found when the animals were tested again at 21 days of age. Evaluation of the reproductive integrity of the offspring of the second experiment did not disclose any deficits.     

Diurnal patterns in brain biogenic amines of rats exposed to 60-Hz electric fields

Levels of brain neurotransmitters and their metabolites, as well as concentrations of enzymes associated with their synthesis and metabolism, fluctuate during the day in patterns defined as circadian. The present study examined these rhythms in albino rats exposed to 60-Hz electric fields. Thirty-six animals were exposed to a 39 kV/m field for 4 weeks, 20 h/day, in a parallel-plate electrode system. A group of 36 sham animals was similarly handled and housed in a nonenergized exposure system. On the sampling day, animals were sacrificed at 4-h intervals throughout the 24-h day. Brains were removed, dissected, and kept frozen until chemically analyzed. The levels of biogenic amines and their acidic metabolites in the striatum, hypothalamus, and hippocampus were determined by high-performance liquid chromatography with electrochemical detection (HPLC-ECD) methods. Repeated exposure to 60-Hz electric fields produced significant alterations in the diurnal rhythms of several biogenic amines: dihydroxyphenylacetic acid (DOPAC, the primary metabolite of dopamine in the rat) in the striatum, and norepinephrine, dopamine, and 5-hydroxyindoleacetic acid (5-HIAA; serotonin metabolite) in the hypothalamus. Levels of serotonin in the striatum and hypothalamus showed clear circadian patterns that was not affected by the field. No diurnal or field-related changes were observed in the hippocampal amines.     

Core histone acetylation is regulated by linker histone stoichiometry in vivo

We investigated the relationship between linker histone stoichiometry and the acetylation of core histones in vivo. Exponentially growing cell lines induced to overproduce either of two H1 variants, H1(0) or H1c, displayed significantly reduced rates of incorporation of [(3)H]acetate into all four core histones. Pulse-chase experiments indicated that the rates of histone deacetylation were similar in all cell lines. These effects were also observed in nuclei isolated from these cells upon labeling with [(3)H]acetyl-CoA. Nuclear extracts prepared from control and H1-overexpressing cell lines displayed similar levels of histone acetylation activity on chromatin templates prepared from control cells. In contrast, extracts prepared from control cells were significantly less active on chromatin templates prepared from H1-overexpressing cells than on templates prepared from control cells. Reduced levels of acetylation in H1-overproducing cell lines do not appear to depend on higher order chromatin structure, because it persists even after digestion of the chromatin with micrococcal nuclease. The results suggest that alterations in chromatin structure, resulting from changes in linker histone stoichiometry may modulate the levels or rates of core histone acetylation in vivo.     

Antifungal compound, feruloylagmatine, induced in winter wheat exposed to a low temperature

An antifungal compound, feruloylagmatine [1-(trans -4'-hydroxy-3'- methoxycinnamoylamino)-4-guanidinobutanel, was isolated from crowns of winter wheat (Triticum aestivum L. cv Chihokukomugi). Its structure was identified by NMR, MS and UV spectral analyses. It was also confirmed by an HPLC analysis that the compound was induced in wheat by a low temperature.