Evidence for genotoxic effects of resonant ELF magnetic fields

The possibility that extremely low frequency (ELF) magnetic fields affect the genomic integrity of the cell is the objective of this study. Human peripheral lymphocytes (HPLs) were exposed to different exposure conditions combining ac and static magnetic fields. We used the micronuclei (MN) cytogenetic technique, because MN formation is considered as a marker of chromosomal damage produced by genotoxic agents.The first set of experiments were performed at 50 Hz, 150 μT rms and 32 Hz, 75 μT and 150 μT rms magnetic fields with the static geomagnetic field components nulled. No effects were detected using the MN test on HPL as an indicator for cellular genomic damage when the static magnetic field was nulled. Moreover, such exposure to an ac magnetic field does not appear to interfere with the action of a powerful genotoxic agent mytomicin-C (MMC), i.e. there was no synergistic effect.The second set of experiments were conducted exposing cells to 32 Hz, 150 μT and 75 μT rms, parallel to a 42 μT dc magnetic field. The 75 μT rms, 32 Hz exposure condition was chosen to maximize the resonance effect on Ca²⁺ according to parametric resonance theory. We found a statistically significant increase of MN for both exposure conditions. This experiment provides evidence for the genotoxic effects of resonant ELF magnetic fields in human lymphocytes.     

Anchorage-independent growth with JB6 cells exposed to 60 Hz magnetic fields at several flux densities

JB6 clone 41 cells have previously been shown to respond to a 1.1. mT magnetic field with increased growth under anchorage-independent (AI) conditions. Here we have examined the AI growth-response simultaneously at three lower flux densities and without an applied field. Fields were generated with Helmholtz coils held in water-jacketed CO₂ incubators. Colony growth (60 μm diameter) was scored at 8 and 14 days after seeding cells in soft agar. Zero-field experiments conducted simultaneously in several incubators produced uniform counts (about 1 per 10³ cells seeded). For 14-day exposures at 100 μT, 10 μT and 1μT, four of four, six of six, and two of three experiments, respectively, showed a significantly increased colony number (p < 0.02), with the ratio of field-exposed to control colonies varying from 1.2 to 3.2. Thus, an effect of magnetic fields at flux densities approaching environmental levels of exposure has been demonstrated.     

A study of magnetic field effects on fibroblast cultures Part 1. The evaluation of the effects of static and extremely low frequency (ELF) magnetic fields on vital functions of fibroblasts

Cultured fibroblasts isolated from murine livers by tissue trypsinization were exposed to a static magnetic field (0.49 T) and an extremely low frequency (ELF) magnetic field (50 Hz, 0.020 T). The cultures were exposed to magnetic fields on four consecutive days for exposure times of 2, 4, 8, 16, 32 and 64 min. After exposure the following parameters of the fibroblast cultures were determined: the dynamics of culture growth, the protein content and ¹⁴C-thymidine incorporation. The cytometric parameters of the fibroblasts were also assessed. The ELF magnetic field compromised vital functions of the fibroblasts (inhibition of culture growth, decreased cellular protein, lowered cytometric parameters) and caused a slowdown in the rate of ¹⁴C-thymidine incorporation which indicates altered DNA synthesis. Ongoing experiments with a static magnetic field have shown no effect on the vital functions of fibroblasts.     

Changes in cell proliferation due to environmental non-ionizing radiation 1. ELF electromagnetic fields

To study the effect of extremely low frequency (ELF) magnetic fields on cell growth, human cells (AMA cells) and K14 skin fibroblasts cells, growing in monolayer culture, were exposed to a sinusoidal 50 Hz, 80 μT field. Exposure times varied from 15 to 90 min. Changes in cell proliferation rates were then studied during subsequent field-free incubation, for 24 h.The results showed that a 30 min exposure resulted in a much higher increase in proliferation rates in the AMA cells compared with non-exposed cells or cells exposed to electromagnetic fields for shorter or longer times. The magnitude of the increase also depended on the initial proliferation rate and confluency. The exposure to varying field densities showed that the greatest increase in proliferation occurred at 80 μT.     

Power frequency magnetic field exposure and gap junctional communication in Clone 9 cells

Exposure to a power-frequency magnetic field has been reported to produce a statistically significant inhibition of gap junctional communication (GJC) in Clone 9 cells that have been pre-stressed by treatment with low concentrations of chloral hydrate (CH) [C.F. Blackman, J.P. Blanchard, S.G. Benane, D.E. House, J.A. Elder, Double blind test of magnetic field effects on neurite outgrowth, Bioelectromagnetics, 19 (1998) 204-209]. This observation might provide mechanistic insight into the possible role of electromagnetic fields (EMFs) in the carcinogenic process, since cancer cells frequently show decreased or absent GJC, and tumor promoting chemicals have been observed to inhibit GJC. Magnetic field exposure conditions were 45 Hz, 23.8 microT rms + parallel DC 36.6 microT, for 30 min of exposure. The responses of Clone 9 cells to the GJC-inhibiting effects of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate and the chemical CH were evaluated and compared to reported results [S.G. Benane, C.F. Blackman, D.E. House, Effects of perchloroethylene and its metabolites on intercellular communication in Clone 9 rat liver cells, J. Toxicol. Environ. Health, 48 (1996) 427-437]. Before magnetic field exposure, cells were exposed for 24 h to either 3 (nine experiments) or 5 mM (11 experiments) CH to produce GJC of 67% or 50%, respectively, relative to unexposed controls. GJC was assessed microscopically using the scrape-loading technique and a blinded protocol. No statistically significant effect was observed due to magnetic field exposure with either CH concentration.     

Effect of high magnetic fields on intramolecular exciplex fluorescence of pyrene and dimethylaniline systems

The effect of high magnetic fields (〈13 T) on the intramolecular exciplex fluorescence generated from chain-linked pyrene and dimethylaniline systems is studied in acetonitrile. On increasing the magnetic field from 0 to ca. 1 T, the exciplex fluorescence intensity increases and then decreases gradually for fields up to ca. 8 T. The exciplex fluorescence lifetime exhibits a magnetic field dependence similar to that for the intensity (〈13 T). The reversal of the effect in the high magnetic field region is interpreted in terms of a Δg mechanism.     

Effects of low-frequency magnetic fields on bacteria Escherichia coli.

The effects of low-frequency magnetic fields (Bm=2.7-10 mT, f=50 Hz, time of exposure t=0-12 min, laboratory temperature) on the viability and oxidoreductive activity of gram-negative bacteria Escherichia coli were investigated. The growth of these bacteria was negatively affected by such fields. We compared two experimental systems--solenoid [Sb. Lek. 99 (1998) 455] and a cylindrical spool--to find differences between nonhomogeneous and "more homogeneous" magnetic fields. We observed analogous effects in both experimental conditions. The growth curve of the exposed bacteria was lower than the control one. The ability of bacteria to form colonies decreased with increasing magnetic field intensity and with increasing time of exposure. The oxidoreductive activity was measured using reduction of a tetrazolium salt. The decrease in oxidoreductive activity with increasing time of exposure was observed, but the effect was due to a lower amount of bacteria surviving the exposure to the magnetic fields. The decrease in oxidoreductive activity and ability to form colonies were compared with the assumption that the effect of magnetic field is probably bactericidal.     

A study of magnetic field effects on fibroblast cultures part 3. The evaluation of the effects of static and extremely low frequency (ELF) magnetic fields on glycosaminoglycan metabolism in fibroblasts,cell coats and culture medium

Cultures of fibroblasts isolated from murine liver by the method of tissue trypsinization were exposed to a static magnetic field (0.49 T) and an extremely low frequency (ELF) magnetic field (50 Hz, 0.020 T). The cultures were exposed to magnetic fields for exposure periods of 2, 4, 8, 16, 32 and 64 min on four consecutive days. During the experiment we investigated the glycosaminoglycans isolated from the fibroblast, their coats and the culture medium. The investigations concerned heparan sulphate (DS) and chondroitin sulphates (CS). The changes observed in the fibroblast cultures exposed to ELF magnetic field suggest an increase in sulphate ion content in the glycosaminoglycans investigated, i.e. increased synthesis of the compounds. The ELF magnetic field also affects the degree of glycosaminoglycan sulphatization. Some changes in the quantitative relations between HS, DS and CS were also noted. The static magnetic field had no effect on glycosaminoglycan metabolism, i.e. there were no alterations in incorporation of labeled sulphur into sulphate glycosaminoglycans.     

Strong static magnetic field effects on yeast proliferation and distribution

The present study focuses on the effects of gradient magnetic fields on the behavior of yeast, such as its proliferation and mass distribution, and evaluates the effects of magnetism on materials in the yeast culture system. Yeast, Saccharomyces cerevisiae, was incubated in a liquid medium under magnetic fields (flux density B = 14 T). When yeast in a tube was exposed to 9-14 T magnetic fields with a maximum flux density gradient of dB/dx = 94 T/m, where x is the space coordinate, the rate of yeast proliferation under the magnetic fields decreased after 16 h of incubation compared to that of the control group. The physical properties of the yeast culture system were investigated to discover the mechanism responsible for the observed deceleration in yeast proliferation under magnetic fields. Gas pressure inside the yeast culture flask was compared with and without exposure to a magnetic field. The results suggested that the gas pressure inside a flask with 6 T, 60 T/m slowly increased in comparison to the pressure inside a control tube. Due to the diamagnetism of water (medium solution) and yeast, the liquid surface distinctly inclined under gradient magnetic fields, and the hydrostatic force in suspension was strengthened by the diamagnetic forces. In addition, magnetophoresis of the yeast cells in the medium solution exhibited localization of the yeast sedimentation pattern. The roles of magnetically changed gas-transport processes, hydrostatic pressures acting on the yeast, and changes in the distribution of the yeast sedimentation, as well as the possible effects of magnetic fields on yeast respiratory systems in the observed disturbance of the proliferation are discussed.     

Estimation of genetic effects of a static magnetic field by a somatic cell test using mutagen-sensitive mutants of Drosophila melanogaster

In order to estimate the genetic effects of magnetic fields, a somatic cell test was performed using mutants of the fruit fly Drosophila melanogaster which lack repair functions for damage to their cellular deoxyribonucleic acid (DNA). Young larvae of mutant and normal genotypes were exposed to a homogeneuos 0.6 T magnetic field for 24 h and were then allowed to continue development under normal culture condition until they moulted and finally emerged from their pupal cases. After eclosion, the number of surviving adults was counted. The number of adults of the mutant genotype decreased by about 8% compared with unexposed controls, while that of normal siblings remained unchanged. This suggests that exposure to a static magnetic field resulted in damage to larval cellular DNA, and that somatic cells without normal DNA repair functions failed to continue cell division which resulted in developmental lethality of mutant larvae. DNA damage occurring in normal larvae should have been repaired, so that their survival rate was not altered. The effect was compared with that of UV irradiation, and the genotoxic activity of the 0.6 T static magnetic field was estimated to be the same as that of UV light with an intensity of 0.14 mJ m⁻² s⁻¹. Possible mechanisms in which DNA damage is caused by magnetic field exposure are discussed.     

Magnetocaloric effect and the heat capacity of ferrimagnetic nanosystems in magnetic fluids

The specific heat capacity of a magnetite-based magnetic fluid and changes in the magnetic part of the molar heat capacity of its magnetic phase in magnetic fields of 0–0.7 T were determined calorimetrically over the temperature range 288–353 K. The temperature dependence of changes in the magnetic part of entropy in an applied magnetic field was calculated. It was found that the field dependence of heat capacity had a maximum in fields of 0.3–0.4 T, and the temperature dependences of changes in the magnetic part of heat capacity ΔC _p (H) and entropy ΔS _m(H) had maxima at the magnetic phase transition temperature.     

Dynamic nuclear polarization at high magnetic fields

Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (microw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (gamma(e)gamma(l)), being approximately 660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (> or =5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in microw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.     

Comparison of the low-frequency magnetic field effects on bacteria Escherichia coli, Leclercia adecarboxylata and Staphylococcus aureus

This work studies biological effects of low-frequency electromagnetic fields. We have exposed three different bacterial strains-Escherichia coli, Leclercia adecarboxylata and Staphylococcus aureus to the magnetic field (t<30 min, B(m)=10 mT, f=50 Hz) in order to compare their viability (number of colony-forming units (CFU)). We have measured the dependence of CFU on time of exposure and on the value of the magnetic field induction B(m). Viability decreases with longer exposure time and/or higher induction B(m) for all strains, but the quantity of the effect is strain-dependent. The highest decrease of the viability and the biggest magnetic field effect was observed with E. coli. The smallest magnetic field effect appears for S. aureus. From the measurement of the growth dynamics we have concluded that the decrease of the CFU starts immediately after the magnetic field was switched on.     

Magnetic properties of the fullerene organic compounds in strong magnetic fields

Magnetisation study of the C₆₀·TMTSF·2CS₂ molecular complex in magnetic field up to 47 T for the temperature range 1.8–300 K and ESR spectroscopy of the molecular complex (ET)₂C₆₀ at T=1.8 K for the frequency range 60–90 GHz in magnetic field up to 32 T provide the experimental evidence that a paramagnetic centers with the reduced g-factor values g<1 control magnetic properties of these solids. Anomalous g-factor values may be caused by dynamic Jan-Teller effect on the negative C₆₀ ions, which appear as defects in crystalline structure with a weak charge transfer.     

Effects of low-frequency magnetic fields on the viability of yeast Saccharomyces cerevisiae

A 50 Hz magnetic field effect on the growth of yeasts Saccharomyces cerevisae was studied. The cylindrical coil induced magnetic fields with inductions up to 10 mT. Duration of exposure varied up to 24 min. Exposure took place at laboratory temperature (24-26 degrees C) and the air ventilator maintained the temperature at the place of the sample. We measured the growth curves of yeasts in broth and we calculated the number of CFU (colony forming units) on solid soil. We found that magnetic field decreases the number of yeasts, and slowed down their growth. The result is similar to the experiments with bacteria E. coli, S. aureus and L. adecarboxylata. It seems that the magnetic fields kill a part of yeasts and the bigger part of them survives and continues in their growth.     

Effects of 50 Hz sinusoidal magnetic fields and spark discharges on human lymphocytes in vitro

Human peripheral blood lymphocytes were exposed in vitro to 50 Hz sinusoidal magnetic fields of 30 μT, 300 μT, and 1 mT, and were monitored for genotoxic effects. No effects on chromosomal aberrations, micronuclei or proliferation indices were noticed. A weak effect on sister chromatid exchanges, noted in one series of experiments, could not be verified when the series was repeated. Exposure of whole blood to spark discharges of up to 3.65 kVcm⁻¹ and 2.6 μs duration (10 pulses) did not result In chromosomal aberrations. Cell destruction from spark discharges was extensive. The conductivity of blood during a spark discharge pulse was examined and was shown to decrease by a factor of 2–3 at the beginning of the pulse owing to the β-relaxation of cells. After 0.5 μs the conductivity approached a constant level.     

Influence of magnetic forces on electrochemical mass transport

Enhancements of the order of 100% in the mass transport limited current for electrodeposition have been observed in magnetic fields of order 1 T. The effect of the field is to induce convection in the solution and it is equivalent to rotating the electrode or stirring the solution. In this communication, a quantitative comparison is made of the magnitude of various body forces which have been proposed to account for the experimentally observed effects, with a view to identifying the likely source of the field enhancement. When the magnetic field is uniform, the Lorentz force and the electrokinetic force both contribute significantly to the field enhancement.     

Catecholamine release from cultured bovine adrenal medullary chromaffin cells in the presence of 60-Hz magnetic fields

Effects of powerline frequency (50/60 Hz) electric and magnetic fields on the central nervous system may involve altered neurotransmitter release. This possibility was addressed by determining whether 60-Hz linearly polarized sinusoidal magnetic fields (MFs) alter the release of catecholamines from cultured bovine adrenal chromaffin cells, a well-characterized model of neural-type cells. Dishes of cells were placed in the center of each of two four-coil Merritt exposure systems that were enclosed within mu-metal chambers in matched incubators for simultaneous sham and MF exposure. Following 15-min MF exposure of the cells to flux densities of 0.01, 0.1, 1.0 or 2 mT, norepinephrine and epinephrine release were quantified by high-performance liquid chromatography (HPLC) coupled with electrochemical detection. No significant differences in the release of either norepinephrine or epinephrine were detected between sham-exposed cells and cells exposed to MFs in either the absence or presence of Bay K-8644 (2 microM) or dimethylphenylpiperazinium (DMPP, 10 microM). Consistent with these null findings is the lack of effect of MF exposure on calcium influx. We conclude that catecholamine release from chromaffin cells is not sensitive to 60-Hz MFs at magnetic flux densities in the 0.01-2 mT range.     

Magnetic quenching of positronium in organic solutions

The magnetic quenching of ortho-positronium (o-Ps) in some pure nonpolar liquids (n-hexane, cyclohexane and benzene) and solutions (nitrobenzene in n-hexane, cyclohexane and benzene; and carbon tetrachloride and biphenyl in n-hexane) is examined for steady magnetic fields up to 14 kG by the positron annihilation lifetime technique. The long lifetime of o-Ps is very sensitive to the strength of the external magnetic field, decreasing as the field strength increases. This effect follows from a well-known principle of atomic physics, the quadratic Zeeman effect. With one exception, all the liquids studied here appear to be normal in this regard. The exception is nitrobenzene in n-hexane, which shows a very marked enhancement of quenching beyond the Zeeman effect at low fields.