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At least 865 records · Page 48Linked to original sources
PubMed1997

[Evaluation of selected functional circulation parameters of workers from various occupational groups exposed to electromagnetic fields of high frequency. III. 24-h monitoring of arterial blood pressure (ABP)].

The problem of blood pressure regulation in persons occupationally exposed to electromagnetic fields (EMF) has not as yet been elucidated, and most data come from studies carried out long time ago (1960-70) in the former Soviet Union. Our study was aimed at verifying the Soviet data by means of modern methods. Together with traditional methods, a 24-h monitoring of arterial blood pressure (ABP) using a Medilog ABP kit (Oxford) were employed. Measurements were taken automatically every 0.5 h during daily activities and every 1 h during the night rest (about 41 measurements/day). The mean systolic and diastolic blood pressure and heart rate were calculated over day (BPSDOver, BPDOver, HROver), during daily activities (HPDD, BPSD, HRD) and during the night rest (BPSN, BPDN, HRN). The subjective and objective examinations were carried out as well as resting ECG and a 24-h Holter were performed (the results have been published earlier). The study covered male workers of middlewave broadcast stations (71), radioservice (40) and radio line stations (42). The subjects were aged 21-60 years and the duration of their work with devices generating high frequency EMF ranged between 1 and 42 years. The first group of workers was exposed to EFM at the frequency of 1 Mhz, the second at about 150 Mhz and the third group, not exposed, served as the control group. The study revealed that the mean arterial blood pressure and the day/night blood pressure variability indicator showed no significant differences between the groups, whereas the daily heart rate was significantly lower in the workers of middlewave broadcast stations in comparison with the controls despite similar type of work as far as physical effort and psychic burden are concerned, and similar non-occupational activities. The day/night heart rate variability indicator was significantly lower in the groups exposed. The decreased value of this indicator may suggest the occurrence of disorders in the neurovegetative regulation. In persons employed at radioservice stations a higher incidence of the increased arterial blood pressure, in comparison with the control group, was observed.

Adult↗
PubMed1999

Reproductive and teratologic effects of low-frequency electromagnetic fields: a review of in vivo and in vitro studies using animal models.

In order to evaluate the reproductive risks of low-frequency electromagnetic fields (EMF), it is important to include epidemiological and animal studies in the evaluation, as well as the appropriate basic science information in developmental biology and teratology. This review presents a critical review of in vivo animal studies and in vitro tests, as well as the biological plausibility of the allegations of reproductive risks. In vitro or in vivo studies in nonhuman species can be used to study mechanisms and the effects that have been suggested by human investigations. Only well designed whole-animal teratology studies are appropriate when the epidemiologists and clinical teratologists are uncertain about the environmental risks. Even the inference of teratogenesis cannot be drawn from culture experiments, because the investigator is not in a position to know whether any of his observations will be manifested in living organisms at term. Other aspects of reproductive failure such as abortion, infertility, stillbirth, and prematurity, cannot be addressed by in vitro or culture experiments. In fact, they are very difficult to design and interpret in nonprimate in vivo models. The biological plausibility some of the basic mechanisms involved in reproductive pathology were evaluated, concentrating primarily on the mechanisms involved in the production of birth defects. The studies dealing with mutagenesis, cell death and cell proliferation using in vitro systems do not indicate that EMFs have the potential for deleteriously affecting proliferating and differentiating embryonic cells at the exposures to which populations are usually exposed. Of course, there is no environmental agent that has no effect, deleterious or not, at very high exposures. The animal and in vitro studies dealing with the reproductive effects of EMF exposure are extensive. There are >70 EMF research projects that deal with some aspect of reproduction and growth. Unfortunately, a large proportion of the embryology studies used the chick embryo and evaluated the presence or absence of teratogenesis after 48-52 h of development. This is not a stage of development at which an investigator could determine whether teratogenesis occurred. The presence of clinically relevant teratogenesis can only be determined at the end of the gestational period. The chick embryo studies are also of little assistance to the epidemiologist or clinician in determining whether EMF represents a hazard to the human embryo, and the results are, in any event, inconsistent. On the other hand, the studies involving nonhuman mammalian organisms dealing with fetal growth, congenital malformations, embryonic loss, and neurobehavioral development were predominantly negative and are therefore not supportive of the hypothesis that low-frequency EMF exposures result in reproductive toxicity.

Abnormalities, Radiation-Induced↗
PubMed2004

Ray-tracing techniques to assess the electromagnetic field radiated by radio base stations: application and experimental validation in an urban environment.

This paper aims to validate a ray-tracing model for electromagnetic field calculation, which is used in urban environments to predict irradiation from radio base stations for population exposure evaluation. Validation was carried out through a measurement campaign by choosing measurement points in order to test different propagation environments and analysing broadcast control channels through narrow band measurements. Comparison of the calculated and measured fields indicates that the ray-tracing model used calculates electric field with good accuracy, in spite of the fact that the propagation environment is not described in detail, because of difficulties in modelling the geometrical and electrical characteristics of urban areas. Differences between the calculated and measured results remain below 1.5 dB, with a mean value of 1 dB.

Algorithms↗
PubMed1995

No effect of 60 Hz electromagnetic fields on MYC or beta-actin expression in human leukemic cells.

Epidemiological studies have shown weak correlations between exposure to extremely low-frequency electromagnetic fields (ELF EMFs) and the incidence of several cancers, particularly childhood leukemias, although negative studies have also been reported. These observations have prompted a broad range of in vitro cellular studies in which effects of ELF EMFs have been observed. However, no reported response has been replicated widely in independent laboratories. One potentially important response is the rapid activation of proto-oncogenes and other genes in human leukemic (HL60) cells and a wide variety of other eukaryotic cells, because of the role of these genes in cell proliferation. We describe quantitative Northern analysis of MYC and beta-actin mRNAs from HL60 cells exposed to fields under conditions very similar to those reported previously to activate these genes, namely 60 Hz sinusoidal magnetic fields of 0.57, 5.7 or 57 microT for 20 min. In addition we have used a new design of field-exposure system and introduced a number of other modifications to the protocol to optimize any response. We have also developed a novel method providing enhanced accuracy for the quantitative measurement of mRNA. No significant effect of ELF EMFs on gene expression was observed using any of these systems and analytical methods.

Actins↗
PubMed2005

Electromagnetic fields (GSM 1800) do not alter blood-brain barrier permeability to sucrose in models in vitro with high barrier tightness.

We previously reported that electromagnetic fields (EMFs) [GSM 1800 standard (Global System for Mobile Communications, 1800 MHz)] increased sucrose permeation across the blood-brain barrier (BBB) in vitro. The cell culture model used in our previous study was comprised of rat astrocytes in coculture with porcine brain microvascular endothelial cells (PBECs). In this study, after optimization of cell culture conditions, distinctly improved barrier tightness was observed, accompanied by a loss of susceptibility to EMF-related effects on BBB permeability. Cell cultures were exposed for 1-5 days at an average specific absorption rate (SAR) of 0.3 W/kg in the identical exposure system as described before. To quantify barrier tightness, sucrose permeation across exposed PBEC was measured and compared to values of sham exposed cells and to a control group. Additionally, observations in the BBB coculture system were complemented by similar experiments using two other in vitro models, composed of PBEC monocultures with or without serum. These three models display distinctly higher barrier tightness than the previously used system. In all three BBB models, sucrose permeation across the cell layers remained unaffected by exposure to a GSM 1800 field for up to 5 days. We thus could not confirm enhanced permeability of the BBB in vitro after EMF exposure as reported before since the in vitro barrier tightness in these experiments is now more like that of the in vivo situation.

Animals↗
PubMedDate not supplied

[Species specificity, age factors, and various neurochemical correlates of the animal spontaneous behavior after exposure to electromagnetic field of the ultralow intensity].

Behavioral and neurochemical reactions of small laboratory animals (mice and rats of different age) under exposure to ultralow-intensity electromagnetic fields (EMF, frequency of 4200 and 970 MHz, modulated by a quasistochastic signal in the range of 20-20,000 Hz, power density 15 microW/cm2, specific body absorption rate up to 4.5 mJ/kg) were studied. The EMF basically inhibited the locomotor and exploratory activity in the "open-field" test. The species- and age-specific features rather than radiation conditions dominated. However, decrease in the EMF frequency considerably intensified the observed effect. Change in animal behavior was accompanied by shifts in neurochemical processes, i.e., sharp activation of serotoninergic and inhibition of morepinephrinergic system.

3,4-Dihydroxyphenylacetic Acid↗
PubMedDate not supplied

[Effects of an impulse electromagnetic field on calcium ion accumulation in the sarcoplasmic reticulum of the rat myocardium].

By means of an ion-selective electrode, the effect of an impulse electromagnetic field with a 1 ms impulse, 10 Hz frequency, and 1-10 mT magnetic induction on calcium transport was investigated in the presence of potassium oxalate by rat heart homogenates. Prolonged exposure (100 min) to the field produced 70% inhibition of Ca2+ transfer across the sarcoplasmic reticulum. This effect is associated with direct inhibition of Ca(2+)-ATPase.

Animals↗
PubMed1996

A mechanism for action of extremely low frequency electromagnetic fields on biological systems.

This report outlines a simple mechanism, based on the Hall Effect, by which static and low frequency (50-60 Hz) pulsed electromagnetic fields (PEMFs) can modify cation flow across biological membranes and alter cell metabolism. We show that magnetic fields commonly found in the environment can be expected to cause biologically significant interactions between transported cations and basic domains of cation channel proteins. We calculate that these interactions generate forces of a magnitude similar to those created by normal transmembrane voltage changes known to gate cation channels. Thus PEMFs are shown to have the potential of regulating flow through cation channels, changing the steady state concentrations of cellular cations and thus the metabolic processes dependent on cation concentrations.

Animals↗
PubMed1997

Do electromagnetic fields interact directly with DNA?

The mechanisms whereby electromagnetic (EM) fields stimulate changes in biosynthesis in cells are not known. It has has generally been assumed that EM fields first interact with cell membranes, but this pathway may not be only one. Interactions with membranes are well documented, but recent studies of EM signal transduction in the membrane Na,K-ATPase are best explained by direct interaction of electric and magnetic fields with mobile charges within the enzyme. Interaction with moving charges may be a mechanism that is operative in other biopolymers. Recent studies on DNA have shown that large electron flows are possible within the stacked base pairs of the double helix. Therefore, gene activation by magnetic fields could be due to direct interaction with moving electrons within DNA. Electric fields as well as magnetic fields stimulate transcription, and both fields could interact with DNA directly. The mechanism of EM field-stimulated transcription may be related to the process in striated muscles, where endogenous electrical activity induces the synthesis of new proteins.

Cell Membrane↗
PubMed1998

[Ethical values in the regulation of the exposure to electromagnetic fields].

The purpose of the present paper is to explore some ethical issues underlying the on-going debate on regulation of human exposure to electromagnetic fields, with special reference to the estimated number of attributable cases. The core issue is how to balance the need for electricity of modern society with the threat to the population's health, given the limited number of affected and the limited resources available. The paper compares a "commensurabilist" and an "incommensurabilist" approach to this problem, and suggests to refer to the metaphor of sacrifice rather to that of trade-off. Both approaches can be found at the core of the epidemiologic profession, they can conflict but also converge; the solution has to be sought case by case, being aware of the moral relevance of this process.

Bioethics↗
PubMed1999

Extremely low frequency electromagnetic fields (EMF) and brain cancer in adults and children: review and comment.

Epidemiologic and experimental research on the potential carcinogenic effects of extremely low frequency electromagnetic fields (EMF) has now been conducted for over two decades. Cancer epidemiology studies in relation to EMF have focused primarily on brain cancer and leukemia, both from residential sources of exposure in children and adults and from occupational exposure in adult men. Because genotoxic effects of EMF have not been shown, most recent laboratory research has attempted to show biological effects that could be related to cancer promotion. In this report, we briefly review residential and occupational EMF studies on brain cancer. We also provide a general review of experimental studies as they relate both to the biological plausibility of an EMF-brain cancer relation and to the insufficiency of such research to help guide exposure assessment in epidemiologic studies. We conclude from our review that no recent research, either epidemiologic or experimental, has emerged to provide reasonable support for a causal role of EMF on brain cancer.

Adult↗
PubMedDate not supplied

Effects of electromagnetic fields on the reproductive success of American kestrels.

Reduced reproductive success of birds nesting near power lines has been documented but never directly attributed to electromagnetic fields (EMFs). Laboratory studies have identified EMF effects on embryonic development, but reproductive success of wild birds is dependent on additional factors, including fertility, egg size, hatching, and fledging success. We tested whether EMFs affect reproductive success of birds. Captive American kestrels (Falco sparverius) were bred for one season per year for 2 yr under either controlled or EMF conditions. EMF exposure was equivalent to that experienced by wild reproducing kestrels and was weakly associated with reduced egg laying in 1 yr only. In both years fertility was higher, but hatching success was lower in EMF pairs than control pairs. Fledging success was higher in EMF pairs than control pairs in 1995 only. Egg composition and embryonic development were examined in 1 yr only, but hatchlings were measured in both years. EMF eggs were larger, with more yolk, albumen, and water, but had thinner egg shells than control eggs. Late-term EMF embryos were larger and longer than control embryos, although hatchlings were similar in body mass and size. EMF exposure affected reproductive success of kestrels, increasing fertility, egg size, embryonic development, and fledging success but reducing hatching success.

Animals↗
PubMed1998

Effects of an ELF (50 Hz, 1 mT) electromagnetic field (EMF) on concentration in visual attention, perception and memory including effects of EMF sensitivity.

To investigate psychological effects of an extremely low frequency (ELF)-electromagnetic field (EMF), an experiment with three conditions was designed. EMF field of 50 Hz and 1 mT accompanied by 45 dB SPL noise (EMF + noise), noise, and control. A group of 66 subjects (Ss) participated in the control and in one of the experimental conditions. The sequence of conditions (expositions) was balanced. Expositions were double-blind (except for the obvious control), lasted 1 h and were separated by a 1 h pause. During exposition Ss (three by three) performed tests on attention, perception, memory and filled out a psychological questionnaire. Statistical analysis (one-tailed probability) showed less attention (P < 0.05), perception (P < 0.05) and memory performance (P < 0.1) in Ss exposed to EMF + noise compared with control, whereas for noise versus control no difference was found. Comparing EMF + noise versus noise related to control, reduced perception, less memory performance and more discomfort was observed (P < 0.1). Dividing Ss according to their self-rated sensitivity to EMF, all differences disappeared in the low sensitivity group (N = 30) and were pronounced in sensitive Ss (N = 36). Results indicate an immediate reduction of cognitive performance in attention, perception and memory performance by a 50 Hz EMF of 1 mT. These effects seem to be modulated by the self-perception of sensitivity to EMF.

Adult↗
PubMed2005

Effects of 2450 MHz electromagnetic fields with a wide range of SARs on methylcholanthrene-induced transformation in C3H10T1/2 cells.

This study examined whether 2450 MHz continuous wave high frequency electromagnetic fields (HFEMF) could induce cancer-like changes in mouse C3H10T1/2 cells, and whether HFEMF could initiate malignant or synergistic transformation. Transformed foci, Type II and Type III, were independently counted as the experiment endpoint. The cells were exposed to HFEMF alone at a wide range of specific absorption rates (SARs) of 5 to 200 W/kg for 2 h and/or were treated with a known initiating chemical, methylcholanthrene (MC) (2.5 microg/ml). No significant differences were observed in the malignant transformation (Type II + Type III) frequency between the controls and HFEMF with or without 12-O-tetradecanoylphorbol-13-acetate (TPA) (0.5 ng/ml), a tumor promoter that could enhance transformation frequency initiated by MC in multistage carcinogenesis. However, the transformation frequency for HFEMF at SAR of more than 100 W/kg with MC or MC plus TPA was increased compared with MC alone or MC plus TPA. On the other hand, the corresponding heat groups (heat alone, heat + MC, and heat + MC + TPA) did not increase transformation compared with each control level in C3H10T1/2 cells. This result suggests that 2450 MHz HFEMF could not contribute to the initiation stage of tumor formation, but it may contribute to the promotion stage at the extremely high SAR (100 W/kg).

Animals↗
PubMed2005

Effect of extremely low frequency of electromagnetic fields on cell proliferation, antioxidative enzyme activities and lipid peroxidation in 3T3-L1 preadipocytes--an in vitro study.

The exposure to extremely low frequency electromagnetic field (ELF-MF, frequencies less than 200-300 Hz) can alter the transcription and translation of genes, influence the cell proliferation rate and affect enzyme activities. Moreover, the hypothesis that ELF-MF increases free oxygen metabolites generation has been proposed. Since recent in vivo studies suggest that electric and magnetic fields are able to affect adipose cells metabolism. The aim of the study was to examine the effects of ELF-MF (frequency of basic impulse 180-195 Hz, induction 120 microT) on cell proliferation, antioxidative enzyme activities and malondialdehyde (MDA) concentration in 3T3-L1 preadipocyte cell culture. We found that ELF-MF application lasting 36 minutes daily failed to influence cell count after 24h and 48 h of incubation. After 24 h, in the ELF-MF treated group, manganese- and copper-zinc-containing superoxide dismutase (MnSOD and Cu/ZnSOD) isoenzymes media activities were decreased, catalase activity was increased, whereas there were no significant differences in glutathione peroxidase (GSH-Px) and glutathione reductase (GSSG-Rd) activities in comparison to the control. After 48 h of incubation, all enzyme activities were reduced, except for GSSG-Rd, in which no changes were noticed. MDA concentration at 24 h after incubation with the exposure to ELF-MF was significantly higher in comparison to the control, without ELF-MF. After 48 h of incubation, MDA levels were significantly lower in both groups with no differences between the groups without and with ELF-MF. We conclude that ELF-MF influences antioxidative enzyme activities and increases lipid peroxidation in 3T3-L1 preadipocyte cultures.

3T3-L1 Cells↗
PubMed2003

Radio frequency electromagnetic field exposure in humans: Estimation of SAR distribution in the brain, effects on sleep and heart rate.

In two previous studies we demonstrated that radiofrequency electromagnetic fields (RF EMF) similar to those emitted by digital radiotelephone handsets affect brain physiology of healthy young subjects exposed to RF EMF (900 MHz; spatial peak specific absorption rate [SAR] 1 W/kg) either during sleep or during the waking period preceding sleep. In the first experiment, subjects were exposed intermittently during an 8 h nighttime sleep episode and in the second experiment, unilaterally for 30 min prior to a 3 h daytime sleep episode. Here we report an extended analysis of the two studies as well as the detailed dosimetry of the brain areas, including the assessment of the exposure variability and uncertainties. The latter enabled a more in depth analysis and discussion of the findings. Compared to the control condition with sham exposure, spectral power of the non-rapid eye movement sleep electroencephalogram (EEG) was initially increased in the 9-14 Hz range in both experiments. No topographical differences with respect to the effect of RF EMF exposure were observed in the two experiments. Even unilateral exposure during waking induced a similar effect in both hemispheres. Exposure during sleep reduced waking after sleep onset and affected heart rate variability. Exposure prior to sleep reduced heart rate during waking and stage 1 sleep. The lack of asymmetries in the effects on sleep EEG, independent of bi- or unilateral exposure of the cortex, may indicate involvement of subcortical bilateral projections to the cortex in the generation of brain function changes, especially since the exposure of the thalamus was similar in both experiments (approx. 0.1 W/kg).

Adult↗
PubMed1993

Exposure to low frequency pulsed electromagnetic fields increases interleukin-1 and interleukin-6 production by human peripheral blood mononuclear cells.

The exposure of human peripheral blood mononuclear cells to extremely low frequency pulsed electromagnetic fields (PEMFs) increased both the spontaneous and the PHA- and TPA-induced production of interleukin-1 (IL-1) and IL-6. Our results suggest that cells of the monocytic lineage, which are good producers of both IL-1 and IL-6, can be important cellular targets for PEMFs. Taking into account that these cytokines are among the most pleiotropic ones, these data can help us understand the previous reported effects of PEMFs on the proliferation of human lymphocytes and the effects exerted by such fields on cartilage and bone cells, whose physiological activity is highly dependent on IL-1 and IL-6.

Adult↗