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At least 1,693 records · Page 94Linked to original sources
PubMed2003

Effects of 50 Hz electromagnetic field exposure on apoptosis and differentiation in a neuroblastoma cell line.

Experiments were carried out to assess whether a magnetic field of 50 Hz and 1 mT can influence apoptosis and proliferation in the human neuroblastoma cell line LAN-5. TUNEL assays and poly-ADP ribose polymerase (PARP) expression analysis were performed to test apoptosis induction, and the WST-1 assay was used to calculate the proliferation index in a long term exposure. No alterations were found in cellular ability to undergo programmed cell death, but a small increase in the proliferation index was evidenced after 7 days of continuous exposure. Also, a slight and transient increase of B-myb oncogene expression was detected after 5 days of exposure. Combined exposures of cells to EMF and to chemical agents which interfere with proliferation, such as the differentiative agent retinoic acid and the apoptotic inducer camptothecin, showed an antagonistic effect of magnetic fields against the differentiation of the LAN-5 cells and a protective effect towards apoptosis.

Apoptosis↗
PubMed2002

The exact electromagnetic field description of photon emission, absorption, and radiation pattern. II.

This is the second of two articles, the first of which contains a proposed explanation of quantum theory based upon electron nonlocality and classical electrodynamics. In this second article classical field theory is used to describe a unique field set for exchange of radiation between an atomic eigenstate and the far field. The radiation satisfies the thermodynamic condition of reversibility as described by Boltzmann, Planck, and Einstein. The exchanged radiation supports the kinematic properties of photons, and it can be emitted or absorbed by a vanishingly small volume.

Computer Simulation↗
PubMed2006

Low frequency electromagnetic fields and the Belousov-Zhabotinsky reaction.

Low frequency magnetic fields can influence biochemical reactions and consequently physiological rhythms and oscillations. To test this for a model reaction we used the chemical Belousov-Zhabotinsky (BZ) reaction, which is one of the simplest chemical oscillators. The oscillation frequency of the reaction was tracked optically by the absorption of blue light. Field treatment was carried out at room temperature in the middle of two Helmholtz coils. After starting the reaction, for 5 min the oscillations were monitored as control measurement, then during the next 10 min monitoring was with a magnetic field switched on, followed by a period of 5 min with the field switched off. A variety of exposure conditions have been tested: the frequency was varied between 5 and 1000 Hz, the field strength was varied up to 2.7 mT, different pulse shapes were used, the influence of the exposure temperature was tested, and the influence of the optimum exposure conditions (static magnetic field and the frequency of the dynamic field) as predicted by the ion parametric resonance (IPR) model has been measured. In conclusion, in no case any statistical significant influence of the magnetic treatment on the oscillation frequency of the BZ reaction could be detected (P > .05, t-test).

Biochemical Phenomena↗
PubMed1996

Free radical mechanism for the effects of environmental electromagnetic fields on biological systems.

The radical pair mechanism is discussed as a possible route whereby a magnetic field of environmental strength might affect a biological system. It is well established as the origin of reproducible field effects in chemistry, and these can be observed even at very low magnetic field strengths, including that of the geomagnetic field. Here it is attempted to give a description which might assist experimentalists working in biological laboratories to devize tests of its relevance to their work. The mechanism is well understood and a specific theoretical approach is taken to explore and emphasize the importance of the lifetime of the radical pair and the precise chemical natures of the radicals which comprise it in affecting the size of the low-field effects. Further subsequent processes are likely necessary to cause this primary effect to attain biological significance. Arguments are provided to suggest that the encounters of freely diffusing pairs (F-pairs) of radicals are unlikely to produce significant effects in biology.

Electromagnetic Fields↗
PubMed2005

Effect of 900 MHz electromagnetic fields on nonthermal induction of heat-shock proteins in human leukocytes.

Despite many studies, the evidence as to whether radiofrequency fields are detrimental to health remains controversial, and the debate continues. Cells respond to some abnormal physiological conditions by producing cytoprotective heat-shock (or stress) proteins. The aim of this study was to determine whether exposure to mobile phone-type radiation causes a nonthermal stress response in human leukocytes. Human peripheral blood was sham-exposed or exposed to 900 MHz fields (continuous-wave or GSM-modulated signal) at three average specific absorption rates (0.4, 2.0 and 3.6 W/kg) for different durations (20 min, 1 h and 4 h) in a calibrated TEM cell placed in an incubator to give well-controlled atmospheric conditions at 37 degrees C and 95% air/5% CO(2). Positive (heat-stressed at 42 degrees C) and negative (kept at 37 degrees C) control groups were incubated simultaneously in the same incubator. Heat caused an increase in the number of cells expressing stress proteins (HSP70, HSP27), measured using flow cytometry, and this increase was dependent on time. However, no statistically significant difference was detected in the number of cells expressing stress proteins after RF-field exposure. These results suggest that mobile phone-type radiation is not a stressor of normal human lymphocytes and monocytes, in contrast to mild heating.

Cell Phone↗
PubMed1999

Induction of stress proteins by electromagnetic fields in cultured HL-60 cells.

HL-60 cells in culture were exposed for 2 h to a sinusoidal 0.1 or 1 mT (1 or 10 Gauss) magnetic field at 60 Hz and pulse labeled after exposure with radioactive isotopes by incubation by using either [(35)S]methionine, [(3)H]leucine, or [(33)P]phosphate. The radioactive labels were incorporated into cellular proteins through synthesis or phosphorylation. Proteins were extracted from electrostatically sorted nuclei, and the heat shock/stress proteins (sp) were analyzed for synthesis and phosphorylation by two-dimensional polyacrylamide gel electrophoresis. In the control cultures (no exposure to the magnetic field), sp 72c (cognate form) was faintly observed. A 0.1 mT exposure did not show sp metabolism to be different from that of the controls; however, after a 1 mT exposure of the HL-60 cells, sp 70i (inducible form) was synthesized ([(35)S]methionine incorporation). Sp 90 was not synthesized at either field level, but was phosphorylated ([(33)P]phosphate incorporation) in the 1 mT exposure. Sp 27 (isoforms a and b) was induced after a 1 mT exposure as reflected by labeling with [(3)H]leucine. These sps were not detected after a 0.1 mT exposure. After a 1 mT exposure and labeling with [(33)P], sp 27 isoforms b and c were phosphorylated whereas isoform 'a' was not observed. Sps 70i, 72c, and 90 were identified by commercial sp antibodies. Likewise, polypeptides a, b, and c were verified as sp 27 isoforms by Western blotting. Statistical evaluation of sp areas and densities, determined from fluorographs by Western-blot analysis, revealed a significant increase in sps 90 and 27a after a 1 mT magnetic field exposure. The 1 mT magnetic field interacts at the cellular level to induce a variety of sp species. Bioelectromagnetics 20:347-357, 1999. Published 1999 Wiley-Liss, Inc.

Electromagnetic Fields↗
PubMed1993

Plasmid DNA and low-frequency electromagnetic fields.

Physico-chemical and biological properties were studied in recombinant plasmids exposed to electric and magnetic fields (EMFs). The absence of slow-migrating DNA species and failure to identify induced DNA conformers, suggests that EMFs do not have any obvious genotoxic effect in any of the experimentally tested conditions.

DNA Damage↗
PubMed1993

Biologic effects of prolonged exposure to ELF electromagnetic fields in rats. I. 50 Hz electric fields.

A three-year investigation was conducted on the biological effects of high-intensity electric field exposures of rats for up to 18% of their life span. Two hundred and forty adult male rats, divided into groups of 20 animals each, were exposed at ground potential for 8 h/day at 25-kV/m and 100-kV/m 50-Hz electric fields or were sham exposed for 280, 440, and 1240 h. The corresponding ages at sacrifice were 140, 164, and 315 days. An additional group of 40 rats was investigated under similar experimental conditions after 440 h of exposure at floating potential. Independent of exposure duration, mode of grounding, and field strength, no statistical differences in body weight, morphology, and histology of the liver, heart, mesenteric lymph nodes, and blood variables (hematology and serum chemistry) were found in comparison with sham-exposed animals. Plasma levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone (TS) at sacrifice varied widely among experimental animals in the same group but did not differ in exposed compared with sham-exposed rats. A nonsignificant tendency toward a decrease in the testes/body weight ratio was found after 1240 h of exposure. Microscopic examination of a large number of specimens showed no quantitative or qualitative statistical differences in testes alterations either among exposed animals or between exposed and their corresponding sham-exposed groups. We conclude that 50-Hz electric field exposure, even of long duration at very high field strengths, does not induce harmful effects on tissues with high cellular turnover rates and does not impair the reproductive function of rats. Moreover, after exposure, all variables investigated were well within the normal physiological range.

Animals↗
PubMed1992

Treatment of chronic wounds by means of electric and electromagnetic fields. Part 1. Literature review.

The healing of a cutaneous wound is accompanied by endogeneous electrical phenomena. Not knowing whether they represent merely a side-effect of the physiological processes which take course during healing or whether they play a much more important role as mediators of healing, externally applied electricity was examined as a therapeutic tool for the enhancement of natural regenerative processes. In the present review a historical literature survey dealing with human applications of electric current for wound healing acceleration is given. It presents a complete palette of heterogeneous studies, differing in the parameters of applied electric current, in delivery modes as well as in the types of wounds being stimulated. Because of all these differences, comparing the efficacy of the described methods is difficult and could hardly be objective. Therefore greater stress was laid upon the discussion concerning the problems in designing clinical studies (size of the sample observed, control group, ethics of the procedures), rationales for the employment and possible underlying mechanisms of particular methods, and problems of evaluating their efficacy. In spite of the extensive work performed in the field of electrical wound healing we remain only part way towards explaining the mechanisms by which electricity reinforces the regenerative capabilities of injured tissue as well as only part way towards the selection of the optimal stimulation method from among the published reports.

Chronic Disease↗
PubMed1999

Pulsed electromagnetic fields for the treatment of bone fractures.

The effectiveness of electrical stimulation and Pulsed Electro Magnetic Field (PEMF) stimulation for enhancement of bone healing has been reported by many workers. The mechanism of osteogenesis is not clear, therefore, studies look for empirical evidence. The present study involved a clinical trial using low amplitude PEMF on 19 patients with non-union or delayed union of the long bones. The pulse system used was similar in shape to Bassett's single pulse system where the electric voltage pulse was 0.3 mSec wide repeating every 12 mSec making a frequency of about 80 Hz. The peak magnetic fields were of the order of 0.01 to 0.1 m Tesla, hundred to thousand times smaller than that of Bassett. Among the 13 who completed this treatment schedule the history of non-union was an average of 41.3 weeks. Within an average treatment period of 14 weeks, 11 of the 13 patients had successful bone healing. The two unsuccessful cases had bone gaps greater than 1 cm following removal of dead bone after infection. However, use of such a low field negates Bassett's claim for a narrow window for shape and amplitude of wave form, and justifies further experimental study and an attempt to understand the underlying mechanism.

Adolescent↗
PubMed1992

3H-uridine uptake in human leukemia HL-60 cells exposed to extremely low frequency electromagnetic fields.

Human leukemia HL-60 cells in vitro were exposed or sham-exposed to a 60 Hz electric (3.40 mV/m) or magnetic 10 G (1 muT) field for 5 hr in an attempt to replicate the results of a previously published report (1) of increased uptake of [3H] uridine in response to similar exposure conditions. The results of the present experiments indicated no treatment effect of the fields on uridine incorporation. The ability to detect differences in [3H] uridine uptake were confirmed in a negative control experiment. A 'negative control' experiment demonstrated a statistically significant increase in 3H-uridine uptake for cells at 37 degrees C relative to those at 4 degrees C.

Biological Transport↗
PubMed1999

Animal study on electromagnetic field biological potency.

This recent basic research study used an animal model protocol to assess specific biomarkers of the effect of non-ionising, non-thermal radiation (2450 MHz microwave radiation at 5-15 mW/cm2) on bone marrow, peripheral blood, and bronchoalveolar free cell populations. Of 40 male Wistar rats taken in the study, 20 animals of the experimental group were irradiated for 2 hours a day, 5 days a week, and subsequently killed on days 1, 8, 16, and 30 of the experiment. The remaining 20 rats served as control. All animals were previously intratracheally instilled with biologically inert microspheres to see the influence of irradiation on lung retention kinetics. The cell response to chosen electromagnetic irradiation was followed quantitatively and qualitatively using the standard laboratory methods. The results of peripheral blood cell response suggested a decreasing tendency in total leukocyte count and in relative lymphocyte count in the treated group. A slight increase was also observed in granulocyte count and in the absolute count of peripheral blood erythrocytes over control animals.

Animals↗
PubMedDate not supplied

Electromagnetic field exposure and cancer: a review of epidemiologic evidence.

The idea that exposure to power-frequency electric and magnetic fields might contribute to cancer causation has been under investigation for nearly two decades. A number of epidemiologic studies have been undertaken, but findings have been weak, inconsistent, and inconclusive. This article provides an updated survey of epidemiologic information and considers those data in relation to the many scientific uncertainties that still persist.

Adult↗
PubMed2005

Exposure to low-intensive superhigh frequency electromagnetic field as a factor of carcinogenesis in experimental animals.

Inbred albino mice and C57Bl/6 mice were exposed to nonthermal radiation of 37 GHz frequency in order to detect delayed effects caused by repeated irradiation. The detected pathomorphological changes and the dynamics of their formation suggest that these factors are responsible for delayed formation of immunodeficiency provoking mutagenic and carcinogenic effects.

Animals↗
PubMed2002

[Basic science to evaluate efficiency of means protecting from electromagnetic fields].

Theory of EMF's informational influence, besides the heat effect, on biologic objects is generally accepted nowadays. Also, EMF sources are widely used both for industrial and household purposes, and become an increasing hazard for public health. All that necessitates individual protective means including "VITA" device, the leading one, efficiency and safety of which are supported by research in some scientific institutions.

Adaptation, Physiological↗