Resting EEG effects during exposure to a pulsed ELF magnetic field

Continuing evidence suggests that extremely low frequency magnetic fields (ELF MFs) can affect animal and human behavior. We have previously demonstrated that after a 15 min exposure to a pulsed ELF MF, with most power at frequencies between 0 and 500 Hz, human brain electrical activity is affected as measured by electroencephalography (EEG), specifically within the alpha frequency (8-13 Hz). Here, we report that a pulsed ELF MF affects the human EEG during the exposure period. Twenty subjects (10 males; 10 females) received both a magnetic field and a sham session of 15 min in a counterbalanced design. Analysis of variance (ANOVA) revealed that alpha activity was significantly lower over the occipital electrodes (O1, Oz, O2) [F(1,16) = 5.376, P < .01, eta2 = 0.418] after the first 5 min of magnetic field exposure and was found to be related to the order of exposure (MF-sham vs. sham-MF). This decrease in alpha activity was no longer significant in the 1st min post-exposure, compared to sham (P > .05). This study is among the first to assess EEG frequency changes during a weak (+/-200 microTpk), pulsed ELF MF exposure.     

Changes in human EEG alpha activity following exposure to two different pulsed magnetic field sequences

The present study investigates the effects of a weak (+/-200 microT(pk)), pulsed, extremely low frequency magnetic field (ELF MF) upon the human electroencephalogram (EEG). We have previously determined that exposure to pulsed ELF MFs can affect the EEG, notably the alpha frequency (8-13 Hz) over the occipital-parietal region of the scalp. In the present study, subjects (n = 32) were exposed to two different pulsed MF sequences (1 and 2, used previously) that differed in presentation rate, in order to examine the effects upon the alpha frequency of the human EEG. Results suggest that compared to sham exposure, alpha activity was lowered over the occipital-parietal regions of the brain during exposure to Sequence 1, while alpha activity over the same regions was higher after Sequence 2 exposure. These effects occurred after approximately 5 min of pulsed MF exposure. The results also suggest that a previous exposure to the pulsed MF sequence determined subjects' responses in the present experiment. This study supports our previous observation of EEG changes after 5 min pulsed ELF MF exposure. The results of this study are also consistent with existing EEG experiments of ELF MF and mobile phone effects upon the brain.     

Human electrophysiological and cognitive effects of exposure to ELF magnetic and ELF modulated RF and microwave fields: a review of recent studies

The investigation of weak (<500 microT), extremely low frequency (ELF, 0-300 Hz) magnetic field (MF) exposure upon human cognition and electrophysiology has yielded incomplete and contradictory evidence that MFs interact with human biology. This may be due to the small number of studies undertaken examining ELF MF effects upon the human electroencephalogram (EEG), and the associated analysis of evoked related potentials (ERPs). Relatively few studies have examined how MF exposure may affect cognitive and perceptual processing in human subjects. The introduction of this review considers some of the recent studies of ELF MF exposure upon the EEG, ERPs and cognitive and perceptual tasks. We also consider some of the confounding factors within current human MF studies and suggest some new strategies for further experimentation.     

Possible mechanisms of synaptic plasticity modulation by extremely low-frequency magnetic fields

Understanding the biological mechanisms by which extremely low-frequency (ELF, < 300 Hz) magnetic fields (MFs) interact with human brain activity is an active field of research. Such knowledge is required by international agencies providing guidelines for general public and workers exposure to ELF MFs (such as ICNIRP, the International Commission on Non-Ionizing Radiation Protection). The identification of these interaction mechanisms is extremely challenging, since the effects of ELF MF exposure need to be monitored and understood at very different spatial (from micrometers to centimeters) and temporal (from milliseconds to minutes) scales. One possibility to overcome these issues is to develop biophysical models, based on the systems of mathematical equations describing the electric or metabolic activity of the brain tissue. Biophysical models of the brain activity offer the possibility to simulate how the brain tissue interacts with ELF MFs, in order to gain new insights into experimental data, and to test novel hypotheses regarding interaction mechanisms. This paper presents novel hypotheses regarding the effects of power line (60 Hz in North America) MFs on human brain activity, with arguments from biophysical models. We suggest a hypothetic chain of events that could bridge MF exposure with detectable effects on human neurophysiology. We also suggest novel directions of research in order to reach a convergence of biophysical models of brain activity and corresponding experimental data to identify interaction mechanisms.     

Effects of exposure to a 50 Hz sinusoidal magnetic field during the early adolescent period on spatial memory in mice

Adolescence is a critical developmental stage during which substantial remodeling occurs in brain areas involved in emotional and learning processes. Although a robust literature on the biological effects of extremely low frequency magnetic fields (ELF‐MFs) has been documented, data on the effects of ELF‐MF exposure during this period on cognitive functions remain scarce. In this study, early adolescent male mice were exposed from postnatal day (P) 23–35 to a 50 Hz MF at 2 mT for 60 min/day. On P36–45, the potential effects of the MF exposure on spatial memory performance were examined using the Y‐maze and Morris water maze tasks. The results showed that the MF exposure did not affect Y‐maze performance but improved spatial learning acquisition and memory retention in the water maze task under the present experimental conditions. Bioelectromagnetics 34:275–284, 2013. © 2012 Wiley Periodicals, Inc.     

Do cocarcinogenic effects of ELF electromagnetic fields require repeated long‐term interaction with carcinogens? Characteristics of positive studies using the DMBA breast cancer model in rats

The carcinogenic or cocarcinogenic potential of extremely low frequency (ELF; 50 or 60 Hz) magnetic fields (MFs) has been evaluated worldwide in diverse animal model systems. Though most results have been negative, weakly positive or equivocal results have been reported in several cancer models, including the rat DMBA (7,12-dimethylbenz[a]anthracene) model of mammary cancer. Based on the experimental conditions used in studies in which cocarcinogenic effects of ELF MF were found, it was recently proposed that MF exposure may potentiate the effects of known carcinogens only when the animals are exposed to both MF and carcinogen during an extended period of tumor development, i.e., when the carcinogen is given repeatedly during MF exposure. This review summarizes a series of experiments from our group, showing cocarcinogenic MF effects in the DMBA breast cancer model in rats, to test whether the above proposal is confirmed by existing data. Flux densities of 50 or 100 microT significantly increased the growth of mammary tumors, independent of whether DMBA was given in a single administration or repeatedly over a prolonged period. Thus, these data do not substantiate the hypothesis requiring repeated doses of DMBA during MF exposure. Instead, several other aspects of study design and experimental factors are identified that seem to be critical for the detection of cocarcinogenic effects of MF exposure in the rat DMBA mammary cancer model. These include the rat subline used, the dose of DMBA, the duration of MF exposure, the flux density, the background (sham control) tumor incidence, and the location of mammary tumors in the mammary gland complex. These and other experimental aspects may explain why some laboratories did not detect cocarcinogenic MF effects in the DMBA model. We hope that direct comparison of MF bioeffects in different rat sublines and further evaluation of other experimental differences between studies on MF exposure in the DMBA model will eventually determine which genetic and environmental factors are critical for potential carcinogenic or cocarcinogenic effects of ELF MF exposure.     

Survey of electromagnetic field exposure in bedrooms of residences in lower Austria

Previous investigations of exposure to electric, magnetic, or electromagnetic fields (EMF) in households were either about electricity supply EMFs or radio frequency EMFs (RF‐EMFs). We report results from spot measurements at the bedside that comprise electrostatic fields, extremely low‐frequency electric fields (ELF‐EFs), extremely low‐frequency magnetic fields (ELF‐MFs), and RF‐EMFs. Measurements were taken in 226 households throughout Lower Austria. In addition, effects of simple reduction measures (e.g., removal of clock radios or increasing their distance from the bed, turning off Digital Enhanced Cordless Telecommunication (DECT) telephone base stations) were assessed. All measurements were well below International Commission on Non‐Ionizing Radiation Protection (ICNIRP) guideline levels. Average night‐time ELF‐MFs (long‐term measurement from 10 pm to 6 am, geometric mean over households) above 100 nT were obtained in 2.3%, and RF‐EMFs above 1000 µW/m² in 7.1% of households. Highest ELF‐EFs were primarily due to lamps beside the bed (max = 166 V/m), and highest ELF‐MFs because of transformers of devices (max = 1030 nT) or high current of power lines (max = 380 nT). The highest values of RF‐EMFs were caused by DECT telephone base stations (max = 28979 µW/m²) and mobile phone base stations (max = 4872 µW/m²). Simple reduction measures resulted in an average decrease of 23 nT for ELF‐MFs, 23 V/m for ELF‐EFs, and 246 µW/m² for RF‐EMFs. A small but statistically significant correlation between ELF‐MF exposure and overall RF‐EMF levels of R = 0.16 (P = 0.008) was computed that was independent of type (flat, single family) and location (urban, rural) of houses. Bioelectromagnetics 31:200–208, 2010. © 2009 Wiley‐Liss, Inc.     

EEG Spectral Analysis on Muslim Prayers

This study investigated the proposition of relaxation offered by performing the Muslim prayers by measuring the alpha brain activity in the frontal (F3–F4), central (C3–C4), parietal (P3–P4), and occipital (O1–O2) electrode placements using the International 10–20 System. Nine Muslim subjects were asked to perform the four required cycles of movements of Dhuha prayer, and the EEG were subsequently recorded with open eyes under three conditions, namely, resting, performing four cycles of prayer while reciting the specific verses and supplications, and performing four cycles of acted salat condition (prayer movements without any recitations). Analysis of variance (ANOVA) tests revealed that there were no significant difference in the mean alpha relative power (RP_α) between the alpha amplitude in the Dhuha prayer and the acted conditions in all eight electrode positions. However, the mean RP_α showed higher alpha amplitude during the prostration position of the Dhuha prayer and acted condition at the parietal and occipital regions in comparison to the resting condition. Findings were similar to other studies documenting increased alpha amplitude in parietal and occipital regions during meditation and mental concentration. The incidence of increased alpha amplitude suggested parasympathetic activation, thus indicating a state of relaxation. Subsequent studies are needed to delineate the role of mental concentration, and eye focus, on alpha wave amplitude while performing worshipping acts.     

No effects of extremely low frequency magnetic fields found on cytotoxic activities and cytokine production of human peripheral blood mononuclear cells in vitro

Several epidemiologic studies have suggested an association between exposure to extremely low frequency (ELF) magnetic fields (MFs) and cancer in adults and children. A possible target of MFs is the immune system. The effects of the exposure to ELF MFs on the immunological functions of human peripheral blood mononuclear cells (PBMCs) obtained from healthy male volunteers were assessed by measuring the natural killer (NK) and lymphokine activated killer (LAK) activities and the production of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), and interleukin-10 (IL-10). The PBMCs were exposed to three different MF: linearly polarized (vertical), circularly polarized, and elliptically polarized, at 50 and 60 Hz. Magnetic flux densities were set at 500, 100, 20, and 2 microT (rms) for vertical field and at 500 microT (rms) for the rotating fields. Using cytotoxicity assay and enzyme-linked immunosorbent assay (ELISA) for cytokine production, we could not find any effects of ELF MFs on the cytotoxic activities and the cytokines production of human PBMCs.     

Static magnetic fields affect calcium fluxes and inhibit stress-induced apoptosis in human glioblastoma cells

BACKGROUND: Epidemiologic data revealed increased brain tumor incidence in workers exposed to magnetic fields (MFs), raising concerns about the possible link between MF exposure and cancer. However, MFs seem to be neither mutagenic nor tumorigenic. The mechanism of their tumorigenic effect has not been elucidated. METHODS: To evaluate the interference of MFs with physical (heat shock, HS) and chemical (etoposide, VP16) induced apoptoses, respectively, we exposed a human glioblastoma primary culture to 6 mT static MF. We investigated cytosolic Ca(2+) ([Ca(2+)](i)) fluxes and extent of apoptosis as key endpoints. The effect of MFs on HS- and VP16-induced apoptoses in primary glioblastoma cultures from four patients was also tested. RESULTS: Static MFs increased the [Ca(2+)](i) from a basal value of 124 +/- 4 nM to 233 +/- 43 nM (P < 0.05). MF exposure dramatically reduced the extent of HS- and VP16-induced apoptoses in all four glioblastoma primary cultures analyzed by 56% (range, 28-87%) and 44% (range, 38-48%), respectively. However, MF alone did not exert any apoptogenic activity. Differences were observed across the four cultures with regard to apoptotic induction by HS and VP16 and to MF apoptotic reduction, with an individual variability with regard to apoptotic sensitivity. CONCLUSION: The ability of static MFs to reduce the extent of damage-induced apoptosis in glioblastoma cells might allow the survival of damaged and possibly mutated cells.     

Possible cocarcinogenic effects of ELF electromagnetic fields may require repeated long-term interaction with known carcinogenic factors

Literature on cancer-related biological effects of extremely low frequency (ELF) magnetic fields (MF) is discussed in the light of the current understanding of carcinogenesis as a multistep process of accumulating mutations. Different animal models and study designs have been used to address possible cocarcinogenic effects of MFs. Based on a comparison of the results, we propose a hypothesis that MF exposure may potentiate the effects of known carcinogens only when both exposures are chronic. We also discuss possible mechanisms of MF effects on carcinogenesis and the adequacy of the classical two-step initiation/promotion animal experiments for simulating human exposure to the complex mixture of environmental carcinogens. We conclude that experiments designed according to the two-step concept may not be sufficient for studying the possible role of MF in carcinogenesis. Possible further animal studies are more likely to be productive if they include models that combine chronic exposure to MFs with long-term exposures to known carcinogens.     

基于聚类分析方法的酒后人脑状态研究

目的:本文对酒精引起的人脑状态变化进行讨论。通过对客观记录的受试者摄入酒精事件的脑电图数据进行系统聚类分析,从而分析摄入酒精事件与21导联电极分类的关系,进而为有关人脑的其它研究提供实验和理论根据。方法:选取4名习惯用右手、健康的人进行实验,采用标准21个脑电极的10-20导联系统,获取受试者在安静闭眼和摄入一定量啤酒的2个事件的脑电图数据。然后进行数据分析。数据分析的方法是系统聚类分析方法。程序实现采用独立设计的脑电图分析工具箱和聚类分析程序。结果:对脑电图数据聚类分析后发现,未喝酒时脑电活动大致按前额部和中央、后头部、两侧得到3个聚类簇;摄入200毫升啤酒后,受试者P1和P2的大部分额部电极、中央部电极以及后头部电极聚类为一个簇,个别颞部、后头部电极聚类为一个簇,或单个电极独立为一簇,形成孤立点;摄入400毫升啤酒后,受试者P3和P4的大部分额极电极、额部电极、中央部电极以及后头部电极聚类为一个簇,个别额部、中央部、颞部单个电极独立为一簇,形成孤立点。结论:脑电活动对摄入酒精有显著反应。由于人在安静闭眼状态下,后头部记录到的α波较为显著,所以未喝酒时前后头部脑电信号相关性较弱,受试者前后头部的电极基本不在一个聚类簇中;摄入酒精后,受试者大部分额部、中央部和后头部电极聚类为一簇,即前后头部脑电信号的相关性增强,这说明在酒精的作用下,前头部α波增加,α波呈现扩大和增强的趋势。     

Real-time measurement of cytosolic free calcium concentration in Jurkat cells during ELF magnetic field exposure and evaluation of the role of cell cycle

Extremely low frequency magnetic fields (ELF MF) have been reported to alter a number of cell signaling pathways, including those involved in proliferation, differentiation and apoptosis where cytosolic free calcium ([Ca(2+)](c)) plays an important role. To better understand the biological conditions under which ELF MF exposure might alter [Ca(2+)](c), we measured [Ca(2+)](c) by ratiometric fluorescence spectrophotometry during exposure to ELF MF in Jurkat E6.1 cells synchronized to different phases of the cell cycle. Suspensions of cells were exposed either to a near zero MF (Null) or a 60 Hz, 100 microT sinusoidal MF superimposed upon a collinear 78.1 microT static MF (AC + DC). An initial series of experiments indicated that the maximum increase in [Ca(2+)](c) above baseline after stimulation with anti-CD3 was significantly higher in samples exposed to AC + DC (n = 30) compared to Null (n = 30) with the largest difference in G2-M enriched samples. However, in a second study with G2-M enriched cells, samples treated with AC + DC (n = 17) were not statistically different from Null-treated samples (n = 27). Detailed analysis revealed that the dynamics in [Ca(2+)](c) before and after stimulation with anti-CD3 were dissimilar between Null samples from each study. From the results, we concluded (i) that the ELF MF increased [Ca(2+)](c) during an antibody-induced signaling event, (ii) that the ELF MF effect did not depend to a large degree on cell cycle, and (iii) that a field-related change in [Ca(2+)](c) signaling appeared to correlate with features in the [Ca(2+)](c) dynamics. Future work could evaluate [Ca(2+)](c) dynamics in relation to the phase of the cell cycle and inter-study variation, which may reveal factors important for the observation of real-time effects of ELF MF on [Ca(2+)](c).     

Increased vascular permeability in the circumventricular organs of adult rat brain due to stimulation by extremely low frequency magnetic fields

It has been demonstrated that the exposure of biological systems to magnetic fields (MFs) can produce several beneficial effects: tissue recovery in chronic wounds, re‐establishment of blood circulation after tissue ischemia or in necrotic tissues, improvement after epileptic episodes, angiogenesis, etc. In the current study, the effects of extremely low frequency (ELF) MF on the capillaries of some circumventricular organs (CVOs) are demonstrated; a vasodilator effect is reported as well as an increase in their permeability to non‐liposoluble substances. For this study, 96 Wistar male rats (250 g body mass) were used and divided into three groups of 32 rats each: a control group (no treatment); a sham ELF‐MF group; and an experimental group subjected to ELF‐MF (120 Hz harmonic waves and 0.66 mT, root mean square) by the use of Helmholtz coils. All animals were administered colloidal carbon (CC) intravenously to study, through optical and transmission electron microscopy, the capillary permeability in CVOs and the blood–brain barrier (BBB) in brain areas. An increase in capillary permeability to CC was detected in the ELF‐MF‐exposed group as well as a significant increase in vascular area (capillary vasodilation); none of these effects were observed in individuals of the control and sham ELF‐MF groups. It is important to investigate the mechanisms involved in the phenomena reported here in order to explain the effects of ELF‐MF on brain vasculature. Bioelectromagnetics 34:145–155, 2013. © 2012 Wiley Periodicals, Inc.     

Behavioral Differences of the Insect Morimus funereus (Coleoptera,Cerambycidae) Exposed to an Extremely Low Frequency Magnetic Field

Changes in the behavior of Morimus funereus individuals were investigated as early manifestations of the contact of a living system with a changed environment primarily established via the nervous system. These experiments were aimed at revealing possible behavioral differences of a laboratory population of cerambycid beetle M. funereus in an “open field” before and after exposure to an extremely low frequency magnetic field (ELF‐MF, 50 Hz, 2 mT). The experimental groups were divided into several activity categories and exposed to ELF‐MF. The results showed that the activity increased in the groups with medium and low motor activity, but decreased in highly active individuals. High individual variability was found in the experimental groups, as well as differences in motor activities between the sexes, both before and after exposure to ELF‐MF. According to preliminary results, we assume the changes of activity in both sexes after exposure to ELF‐MF. The results showed a tendency toward locomotor activity decrease, the affect being more pronounced in females. As opposed to this type of activity, stereotypic activity of males was increased after the exposure, whereas females maintained the expected tendency of decrease. However, we did not obtain statistically significant differences because of a high individual variability and a low total number of individuals in the experiment (N = 28). Only a detailed analysis of the locomotor activity at 1‐min intervals showed some statistically significant differences in behavior between the sexes.     

Spectral EEG characteristics in students with different anxiety profile during tests

EEG spectral power was calculated in 39 students at the age of 19-21 years in two experimental conditions: during the common educational process and immediately before an examination (stress condition). During the education process, in subjects with high anxiety (tested by Spielberger) the relative spectral power of the delta activity was higher than in the other group in the occipital, parietal, central, and right frontal brain areas, whereas the power of the EEG alpha in these areas was lower. Before examination tests, in subjects with high activity the delta power bilaterally increased in the temporal areas, whereas in subjects with low anxiety there was a decrease in the alpha rhythm power, especially in the right frontal area. In stress condition, the relative power of the delta activity in both occipital and temporal, right parietal and central areas was higher in subjects with low anxiety, whereas their alpha power was lower in both frontal and in occipital, parietal, and temporal areas of the left hemisphere.     

Effect of ELF magnetic fields on protein synthesis in Escherichia coli K12

Escherichia coli K12 was used as a model system to determine whether ELF magnetic fields (MFs) are a general stress factor. The cells were exposed to ELF MFs (5-100 Hz) at a maximum intensity of 14 mT r. m.s. for circularly polarized MFs and 10 mT r.m.s. for vertically polarized MFs. The response of the cells to the MFs was estimated from the change in protein synthesis by using 2D PAGE. Approximately 1,000 proteins were separated on the 2D gels. The stress-responsive proteins such as CH10, DNAK, CH60, RECA, USPA, K6P1 and SODM were identified from the SWISS-2DPAGE database on the 2D gels. These proteins respond to most stress factors, including temperature change, chemical compounds, heavy metals, and nutrients. When the bacterial cells were exposed to each MF at 5-100 Hz under aerobic conditions (6.5 h) or at 50 Hz under anaerobic conditions (16 h) at the maximum intensity (7.8 to 14 mT r.m.s.), no reproducible changes were observed in the 2D gels. Changes in protein synthesis were detected by 2D PAGE with exposure to heat shock (50 degrees C for 30 min) or under anaerobic conditions (no bubbling for 16 h). Increases in the levels of synthesis of the stress proteins were observed in heat-shocked cells (CH60, CH10, HTPG, DNAK, HSLV, IBPA and some unidentified proteins) and in cells grown under anaerobic conditions (DNAK, PFLB, RECA, USPA and many unidentified proteins). These results suggest that 2D PAGE is sufficient to detect cell responses to environmental stress. The high-intensity ELF MFs (14 mT at power frequency) did not act as a general stress factor.     

Pre-exposure to 50 Hz magnetic fields modifies menadione-induced genotoxic effects in human SH-SY5Y neuroblastoma cells

Background

Extremely low frequency (ELF) magnetic fields (MF) are generated by power lines and various electric appliances. They have been classified as possibly carcinogenic by the International Agency for Research on Cancer, but a mechanistic explanation for carcinogenic effects is lacking. A previous study in our laboratory showed that pre-exposure to ELF MF altered cancer-relevant cellular responses (cell cycle arrest, apoptosis) to menadione-induced DNA damage, but it did not include endpoints measuring actual genetic damage. In the present study, we examined whether pre-exposure to ELF MF affects chemically induced DNA damage level, DNA repair rate, or micronucleus frequency in human SH-SY5Y neuroblastoma cells.

Methodology/Principal Findings

Exposure to 50 Hz MF was conducted at 100 µT for 24 hours, followed by chemical exposure for 3 hours. The chemicals used for inducing DNA damage and subsequent micronucleus formation were menadione and methyl methanesulphonate (MMS). Pre-treatment with MF enhanced menadione-induced DNA damage, DNA repair rate, and micronucleus formation in human SH-SY5Y neuroblastoma cells. Although the results with MMS indicated similar effects, the differences were not statistically significant. No effects were observed after MF exposure alone.

Conclusions

The results confirm our previous findings showing that pre-exposure to MFs as low as 100 µT alters cellular responses to menadione, and show that increased genotoxicity results from such interaction. The present findings also indicate that complementary data at several chronological points may be critical for understanding the MF effects on DNA damage, repair, and post-repair integrity of the genome.