Enhanced mutagenic effect of a 60 Hz time-varying magnetic field on numbers of azide-induced TA100 revertant colonies

Forty-eight hours exposure to a two Gauss (0.2 mT) rms 60 Hz time varying sinusoidal electromagnetic field increased the number of azide induced TA100 revertant colonies of Salmonella typhimurium 14% as compared with controls in the ambient < 2 milli-Gauss 60 Hz field. In the absence of the electromagnetic field, the numbers of mutant colonies grown within and outside the non-energized coil were nearly identical. Without azide, the number of “spontaneous” mutant colonies forming in the experimental field was not statistically significant from numbers of colonies not exposed to field effects. Experimental temperature variation of 2 °C had little effect on colony formation, and the enhanced production of revertant colonies in the presence of the magnetic field was maintained during continued culture for 5 additional days. © 1994 Wiley-Liss, Inc.     

Facility for chronic exposure of rats to ELF magnetic fields

The facility consists of a 12 × 11.5 × 2.4 m high room containing six sets of exposure apparatus and the other equipment necessary to maintain a pathogen-free system. The apparatus sets produced 5 mT (rms), 0.5 mT, or a sham exposure. The apparatus was arranged in the room to minimize the fringing field of the 5 mT set at the sham position. Each set was 3.85 × 1.80 × 0.66 m in outside dimension, containing 24 cages in the magnetically homogeneous region. The apparatus was designed using Harvey's figure-eight-configuration and generated a horizontal sinusoidal alternating field. In order to save electric power, the coil of the apparatus constituted a 50 Hz LC resonance circuit with a condensor bank to which electric power was supplied to compensate losses. Magnetic flux density was kept constant by controlling the coil current. Although mild steel was used in the skeleton of the building, the fringing flux at the sham was as low as 0.1 to 1 μT. Stainless steel was used for ventilating ducts, racks for the cages, cage covers, feeder baskets, and watering nozzles. The homogeneity of the field was measured to be ± 10% in the animal residence area, and food and water consumption was found to be unaffected by the field. At 5 mT, the coil current was 370 A, and the hollow coil was cooled by a stream of 20°C water to prevent both heat and dew on the coil surface. Vibration and acoustic noise was prevented by fiber reinforced plastic framework of the coil. High harmonic distortion was not observed at the output terminal of the coil driver. The facility has operated without trouble for 2 years. © 1993 Wiley-Liss, Inc.     

Oviposition and development of Drosophila modified by magnetic fields

Drosophila flies placed in a habitat with two lateral boxes demonstrated sensitivity to magnetic fields: Oviposition decreased by exposure to pulsated extremely low frequency (ELF) (100)Hz, 1.76 miliTesla (mT) and sinusosidal fields (50 Hz, 1 mT), while there was no initial effect of exposure to a static magnetic field (4.5 mT). Drosophila eggs treated for 48 h with the above described fields showed that (1) mortality of eggs was lower in controls than in eggs exposed to all tested magnetic fields; (2) mortality of larvae increased when a permanent magnet was used; (3) mortality of pupae was highest when a permanent magnet was used; and (4) general adult viability was highest in controls (67%) and diminished progressively when eggs were exposed to pulsated (55%), sinusoidal (45%), and static (35%) magnetic fields.     

50-Hz magnetic field exposure system for small animals

The design, construction, and results of evaluation of an animal-exposure system for the study of biological effects of extremely low frequency (ELF) magnetic fields are described. The system uses a square coil arrangement based on a modification of the Helmholtz coil. Due to the cubic configuration of this exposure system, horizontal and vertical magnetic fields as high as 0.3 mT can be generated. Circularly polarized magnetic fields can also be generated by changing the current and phase difference between two sets of coils. Tests were made for uniformity of the magnetic field, stray fields, sham-exposure ratio of stray field, changes of temperature and humidity, light intensity and distribution inside the animal-housing space, and noise due to air-conditioning equipment. Variation of the magnetic field was less than 2% inside the animal housing. The stray-field level inside the sham-exposure system is less than 2% of experimental exposure levels. The system can be used for simultaneous exposure of 48 rats (2 to a cage) or 96 mice (4 to a cage). © 1993 Wiley-Liss. Inc.     

In vitro exposure apparatus for ELF magnetic fields

For in vitro studies on the effect of extremely low frequency (ELF) magnetic field exposures in different laboratories, a programmable, high precision exposure system enabling blinded exposures has been developed and fully characterized. It is based on two shielded 4 coil systems that fit inside a commercial incubator. The volume of uniform B field exposure with 1% field tolerance is 50% larger compared to a Merrit 4 coil system with the same coil volume. The uncertainties for the applied magnetic fields have been specified to be less than 4%. The computer controlled apparatus allows signal waveforms that are composed of several harmonics, blind protocols, monitoring of exposure and environmental conditions and the application of B fields up to 3.6 mT root-mean-square amplitude. Sources of artifacts have been characterized: sham isolation >43 dB, parasitic incident E fields <1 V/m, no recognizable temperature differences in the media for exposure or sham state, and vibrations of the mechanically decoupled dish holder <0.1 m/s(2) (= 0.01 g), which is only twice the sham acceleration background level produced by the incubator and fan vibrations.     

Effect of magnetic fields on antioxidative defense and fitness-related traits of Baculum extradentatum (insecta, phasmatodea)

This study aimed to determine the effect of magnetic fields on the antioxidative defense and fitness-related traits of Baculum extradentatum. Following exposure to magnetic fields, antioxidative defense (superoxide dismutase (SOD), catalase (CAT) activities, and total glutathione (GSH) content) and fitness-related traits (egg mortality, development dynamics, and mass of nymphs) were monitored in nymphs. The experimental groups were: control (kept out of influence of the magnets), a group exposed to a constant magnetic field (CMF) of 50 mT, and a group exposed to an alternating magnetic field (AMF) of 50 Hz, 6 mT. We found increased SOD and CAT activities in animals exposed to constant and AMFs, whereas GSH activity was not influenced by experimental magnetic fields. No differences were found in egg mortality between control and experimental groups. Significant differences in the time of development between the control and the CMF group were observed, as well as between the CMF and the AMF group. No differences were found in the mass of the nymphs between the three experimental groups. In conclusion, CMF and AMF have the possibility to modulate the antioxidative defense and some of the fitness-related traits in B. extradentatum.     

Effect of heat dissipation of superparamagnetic nanoparticles in alternating magnetic field on three human cancer cell lines in magnetic fluid hyperthermia

ABSTRACT

Purpose: The purpose of this study was to propose a method for constructing the software setup required for investigating thermal effect of superparamagnetic nanoparticles on three human cell lines. This article aimed to examine the required nanoparticle dose, frequency, field intensity and the exposure time. Materials and methods: In the present study, first some general details were given about design and construction of the setup required for generating a safe magnetic field in order to examine the thermal effect of superparamagnetic nanoparticles on three human cancer cell lines, cultured under laboratory conditions. Next, a series of experimental tests were conducted to study the effect of magnetic field, on the cells. Finally, by applying three types of iron-based nanoparticles with mean diameters of 8, 15 and 20 nm, for 30 min, the temperature rise and specific absorption rate (SAR) were calculated. Results: By conducting experimental tests, the maximum temperature rise at the resonance frequency of the coil was reported to be 80 kHz, and it was observed that all the cells died when temperature of the cells reached 42°C/30 min. Based on the experiments, it was observed that magnetic field with intensity of 8 kA/m within the frequency range of 80–180 kHz did not have any effect on the cells. Conclusions: Based on the results, it can be concluded that the nanoparticle dose of 80 µg/ml with diameter of 8 nm at the resonance frequency of coil for 30 min was sufficient to destroy all the cancerous cells in the flask.     

Lack of chick embryotoxicity after 20 kHz, 1.1 mT magnetic field exposure

This investigation was undertaken because biological studies to evaluate the effects of intermediate frequency magnetic fields are insufficient. White Leghorn fertile eggs (60/group) were either exposed to a 20 kHz, 1.1 mT(rms) sinusoidal magnetic field or sham‐exposed during the first 2, 7, or 11 days of embryogenesis. Lower dose exposures at 0.011 and 0.11 mT(rms) for 2 days were also conducted to elucidate possible dose–response relationships. Additional eggs given all‐trans‐retinoic acid, a teratogen, were exposed to the 1.1 mT(rms) magnetic field for the same periods to investigate the modification of embryotoxicity. After exposure, embryos were examined for mortality and developmental abnormalities. Developmental stage, number of somite pairs, and other developmental endpoints were also evaluated. Experiments were triplicated and conducted in a blind fashion. No exposure‐related changes were found in any of the endpoints in intact embryos exposed to1.1 mT(rms) or to the lower doses of 0.11 and 0.011 mT(rms) magnetic fields. Retinoic acid administration produced embryotoxic responses, which were embryonic death and developmental abnormalities, in 40–60% of embryos in the sham‐exposed groups. The magnitude of these responses was not changed significantly by the magnetic field exposures. Under the present experimental conditions, exposure to 20 kHz magnetic field up to 1.1 mT(rms) was not embryotoxic in the chick and did not potentiate the embryotoxic action of retinoic acid. Bioelectromagnetics 30:573–582, 2009. © 2009 Wiley‐Liss, Inc.     

Static magnetic field exposure fails to affect the viability of different bacteria strains

The viability of the microbes Saccharomyces cerevisiae, Bacillus circulans, Escherichia coli, Micrococcus luteus, Pseudomonas fluorescens, Salmonella enteritidis, Serratia marcescens, and Staphylococcus aureus was tested under static magnetic field exposure up to 24 h in either a homogeneous (159.2 ± 13.4 mT) or three types of inhomogeneous static magnetic fields: (i) peak‐to‐peak magnetic flux density 476.7 ± 0.1 mT with a lateral magnetic flux density gradient of 47.7 T/m, (ii) 12.0 ± 0.1 mT with 1.2 T/m, or (iii) 2.8 ± 0.1 mT with 0.3 T/m. Even the longest period of exposure failed to produce any effect in the growth of bacteriae that could be correlated with static magnetic field exposure. Bioelectromagnetics 31:220–225, 2010. © 2009 Wiley‐Liss, Inc.     

Extremely Low Frequency Magnetic Fields Suppress the Reduction of Germination Rate of Arabidopsis thaliana Seeds Kept in Saturated Humidity

The effects of an extremely low frequency magnetic field (ELFMF) on the germination of plant seeds were examined. The decrease in the germination activity of the seeds of Arabidopsis thaliana WS kept in saturated humidity and high temperature (37°C) was suppressed by the exposure to a 400 mT ELFMF.     

Applied AC and DC magnetic fields cause alterations in the mitotic cycle of early sea urchin embryos

This study demonstrates that exposure to 60 Hz magnetic fields (3.4–8.8 mT) and magnetic fields over the range DC-600 kHz (2.5–6.5 mT) can alter the early embryonic development of sea urchin embryos by inducing alterations in the timing of the cell cycle. Batches of fertilized eggs were exposed to the fields produced by a coil system. Samples of the continuous cultures were taken and scored for cell division. The times of both the first and second cell divisions were advanced by ELF AC fields and by static fields. The magnitude of the 60 Hz effect appears proportional to the field strength over the range tested. The relationship to field frequency was nonlinear and complex. For certain frequencies above the ELF range, the exposure resulted in a delay of the onset of mitosis. The advance of mitosis was also dependent on the duration of exposure and on the timing of exposure relative to fertilization. © 1995 Wiley-Liss, Inc.     

3D in silico study of magnetic fluid hyperthermia of breast tumor using Fe3O4 magnetic nanoparticles

Modeling and simulation of the temperature distribution, the mass concentration, and the heat transfer in the breast tissue are hot issues in magnetic fluid hyperthermia treatment of cancer. The breast tissue can be visualized as a porous matrix with saturated blood. In this paper, 3D in silico study of breast cancer hyperthermia using magnetic nanoparticles (MNPs) is conducted. The 3D FEM models are incorporated to investigate the infusion and backflow of nanofluid in the breast tumor, the diffusion of nanofluid, temperature distribution during the treatment, and prediction of the fraction of tumor necrosis while dealing with the thermal therapy. All the hyperthermia procedures are simulated and analyzed on COMSOL Multiphysics. The sensitivity of frequency and amplitude of the applied magnetic field (AMF) is investigated on the heating effect of the tumor. The mesh dependent solution of Penne's bioheat model is also analyzed. The simulated results demonstrate successful breast cancer treatment using MNPs with minimum side effects. Validation of current simulations results with experimental studies existing in literature advocates the success of our therapy. The increase in the amplitude and frequency of the AMF increases of the temperature in the tumor. The variation of mesh from coarser to finer increased the temperature through small fractions. We have also simulated the magnetic induction problem where the magnetic field is generated by current-carrying coil conductors induce heat in nearby breast tumors due to excitation of MNPs by magnetic flux. This research will aid treatment protocols and real-time clinical breast cancer treatments.     

Effects of static magnetic fields on the growth of various types of human cells

The effects of a static magnetic field (SMF) on the proliferation of various types of human cells were determined. All cultures were maintained at 37 °C throughout the experiment. SMF was generated by placing two magnets oppositely oriented on either side of a T25 flask. The flux density in the flask ranged from 35 to 120 mT. Growth curves were constructed by plotting cell number at 18 h and 4, 7, 11, and 14 days after seeding, with the 18‐h point being a measure of attachment efficiency. Exposure to SMF significantly decreased initial attachment of fibroblasts and decreased subsequent growth compared to sham‐exposed control. Significant effects were observed in both fetal lung (WI‐38) and adult skin fibroblasts, but they were generally larger in the fetal lung fibroblast line. SMF did not affect attachment of human melanoma cells, but inhibited their growth by 20% on day 7. SMF produced no effects in a human adult stem cell line. Oxidant production increased 37% in WI‐38 cells exposed to SMF (230–250 mT) during the first 18 h after seeding, when cell attachment occurs. Conversely, no elevation in oxidant levels was observed after a prolonged 5‐day exposure. These results indicate that exposure to SMF has significant biological effects in some, but not all types of human cells. Bioelectromagnetics 32:140–147, 2011. © 2010 Wiley‐Liss, Inc.     

Effect of nanoheat stimulation mediated by magnetic nanocomposite hydrogel on the osteogenic differentiation of mesenchymal stem cells

Hyperthermia has been considered as a promising healing treatment in bone regeneration. We designed a tissue engineering hydrogel based on magnetic nanoparticles to explore the characteristics of hyperthermia for osteogenic regeneration. This nanocomposite hydrogel was successfully fabricated by incorporating magnetic Fe₃O₄ nanoparticles into chitosan/polyethylene glycol (PEG) hydrogel, which showed excellent biocompatibility and were able to easily achieve increasing temperatures under an alternative magnetic field (AMF). With uniformly dispersed nanoparticles, the composite hydrogel resulted in high viability of mesenchymal stem cells (MSCs), and the elevated temperature contributed to the highest osteogenic differentiation ability compared with direct heat treatment applied under equal temperatures. Therefore, the nanoheat stimulation method using the magnetic nanocomposite hydrogel under an AMF may be considered as an alternative candidate in bone tissue engineering regenerative applications.     

No effect of exposure to static and sinusoidal magnetic fields on nitric oxide production by macrophages

The effects of exposure to static (1–100 mT) or sinusoidal (1 Hz, 1.6 mT) magnetic fields on the production of nitric oxide (NO) by murine BCG-activated macrophages were investigated. In these cells, the inducible isoform of NO synthase is present. No significant differences were observed in nitrite levels among exposed, sham-exposed, or control macrophages after exposure for 14 h to static fields of 1, 10, 50, and 100 mT and to sinusoidal 1.6 mT, 1 Hz magnetic fields. © 1996 Wiley-Liss, Inc.     

Evaluation of potential health effects of 10 kHz magnetic fields: A rodent reproductive study

New technology involving the use of high-frequency inductive power distribution (HID) has recently been developed for use in materials handling and personnel transfer. Sinusoidal magnetic fields at a frequency of 10 kHz with field intensities of approximately 0.2 mT are generated directly between the current-carrying coils of this equipment. Effects of 10 kHz magnetic fields on cell division, migration, and differentiation have never been previously investigated. To evaluate potential effects on these parameters, a rodent reproductive study was undertaken using Wistar rats. Exposures were at 0.095, 0.24, and 0.95 mT with a background exposure of 5–10 μT. Three sets of parental rats were exposed continuously for 20–23.5 h/day to the fields: maternal rats during gestation, paternal rats for at least 45 days prior to mating and maternal rats 1 month prior to mating. Exposure phases thus covered spermatogenesis, maturation of the ovum and ovulation, fertilization, implantation, embryogenesis, organogenesis, and maturation of the fetus immediately prior to parturition. In all experiments pregnancy outcome was assessed. These studies failed to demonstrate any reproductive toxicity resulting from maternal or fetal exposure during gestation or following paternal or maternal exposure for several weeks prior to mating. No quantitative or qualitative effects on spermatogenesis occurred after exposure, and no effects on the estrous cycle or ovulation could be demonstrably linked to the 10 kHz magnetic field exposure at 0.095, 0.25, or 0.95 mT. Where possible, parental clinical chemistry and hematology were also examined. As in mouse toxicology studies previously reported, minor differences were observed between control and treated groups. These were regarded as statistically, but not biologically, significant and could not categorically be attributed to magnetic field exposure. Bioelectromagnetics 19:162–171, 1998. © 1998 Wiley-Liss, Inc.     

The embryonic and post-embryonic development in two Drosophila species exposed to the static magnetic field of 60 mT

In this study, a static magnetic field influence on development and viability in two different species, Drosophila melanogaster and Drosophila hydei, was investigated. Both species completed development (egg–adult), in and out of the static magnetic field induced by double horseshoe magnet. Treated vials with eggs were placed in the gap between magnetic poles (47 mm) and exposed to the average magnetic induction of 60 mT, while control ones were kept far enough from magnetic field source. We found that exposure to the static magnetic field reduced development time in both species, but statistical significance was found only for D. hydei. Furthermore, we found that the average viability of both Drosophila species exposed to the magnetic field was significantly weaker compared to control ones. These results indicate that 60 mT static magnetic field could be considered as a potential stressor, influencing on different levels the embryonic and post-embryonic development of individuals.     

Sinusoidal 60 Hz electromagnetic fields failed to induce changes in protein synthesis in Escherichia coli

Escherichia coli JM83 {F^? ara Δ(lac-proAB) rpsL [?80dΔ(lacZ)M15]} in midlog growth phase at 30 °C were exposed to 60 Hz sinusoidal magnetic field of 3 mT of nonuniform diverging flux, inducing a nonuniform electric field with a maximum intensity of 32 μV/cm using an inductor coil. Exposed and unexposed control cells were maintained at 30.8 ± 0.1 °C and 30.5 ± 0.1 °C, respectively. Quadruplicate samples of exposed and unexposed E. coli cells were simultaneously radiolabeled with ³⁵S-L-methionine at 10 min intervals over 2 hr. Radiochemical incorporation into proteins was analyzed via liquid scintillation counting and by denaturing 12.5% polyacrylamide gel electrophoresis. The results showed that E. coli exposed to a 60 Hz magnetic field of 3 mT exhibited no qualitative or quantitative changes in protein synthesis compared to unexposed cells. Thus small prokaryotic cells (less than 2 μm × 0.5 μm) under constant-temperature conditions do not alter their protein synthesis following exposure to 60 Hz magnetic fields at levels at 3 mT. © 1994 Wiley-Liss, Inc.     

Effect of magnetic hyperthermia on the structure of biofilm and cellular viability of a food spoilage bacterium

This work evaluated the effect of magnetic hyperthermia (MH) on planktonic cells and biofilms of a major food spoilage bacterium Pseudomonas fluorescens and its performance compared to a conventional direct heating (DH) technique. The results showed that MH had a greater and faster bactericidal effect, promoting a significant reduction in cell viability (≥3 Log CFU) in planktonic and biofilm cells, and leading to a complete eradication of planktonic cells at 55 °C (after only ~8 min). Accordingly, when comparing the same final temperatures, MH was more harmful to the integrity of cell membranes than DH, as observed in confocal laser scanning microscope images. Additionally, scanning electron microscope images revealed that exposure to MH had promoted modifications of the bacterial cell surface as well as of the structure of the biofilm. These results present the possibility of using MH out of the biomedical field as a potential disinfection method in food-related environments.     

Development of a higher power intermediate‐frequency magnetic field exposure system for in vitro studies

In a previous article we developed an in vitro 23 kHz magnetic field (MF) exposure system that generated an MF of 532 µT_rms. Using this system, the biological effects of 23 kHz MFs on cell functions have been reported. To further clarify the biological effect of intermediate‐frequency (IF) MFs and investigate the dose–response relationship in cell lines, an exposure system that generates stronger MFs is required. To meet this requirement, we developed a 6.25 mT_rms MF exposure system for in vitro study. This level is 1000 times the reference level for the general public in the ICNIRP guidelines. This system provides an MF of 6.25 mT_rms at 23 kHz with a uniformity within ±5%. To verify that in vitro experimental conditions are maintained, we examined the temperature, environmental MF, and MF leakage for a sham exposure system. In addition, we examined the harmonics, coil shape, and heat generated in the medium by the high‐strength MF. As a result, it was confirmed that this system can be used to evaluate the biological effects of IF MFs. This article presents the design and successful construction of the in vitro exposure system. Bioelectromagnetics 31:156–163, 2010. © 2009 Wiley‐Liss, Inc.