Effects of 50 Hz magnetic fields on C-myc transcript levels in nonsynchronized and synchronized human cells

Magnetic field platform for experiments on well-mixed and spatially structured microbial populations

Magnetic fields have been shown to affect sensing, migration, and navigation in living organisms. However, the effects of magnetic fields on microorganisms largely remain to be elucidated. We develop an open-source, 3D-printed magnetic field exposure device to perform experiments on well-mixed and spatially structured microbial populations. This device is designed in AutoCAD, modeled in COMSOL, and validated using a Gaussmeter and experiments on the budding yeast Saccharomyces cerevisiae. We find that static magnetic field exposure slows the spatially structured expansion of yeast mats that expand in two dimensions, but not yeast mats that expand in three dimensions, across the surface of semi-solid yeast extract-peptone-dextrose agar media. We also find that magnetic fields do not affect the growth of planktonic yeast cells in well-mixed liquid yeast extract-peptone-dextrose media. This study provides an adaptable device for performing controlled magnetic field experiments on microbes and advances our understanding of the effects of magnetic fields on fungi.

EVALUATION OF BCL2 AND ITS REGULATORY MIRS, MIR-15-B AND MIR-16 EXPRESSION CHANGES UNDER THE EXPOSURE OF EXTREMELY LOW-FREQUENCY ELECTROMAGNETIC FIELDS ON HUMAN GASTRIC CANCER CELL LINE

In this research, changes in the expression of B-cell lymphoma 2 (BCL2), miR-15-b and miR-16 in human adenocarcinoma gastric cancer cell line (AGS) following the exposure to magnetic flux densities (MFDs) of 0.2 and 2 mT continuously and discontinuously (1.5 h on/1.5 h off) for 18 h were investigated. Changes in the cell viability were evaluated by the MTT assay. Real-time PCR was used to evaluate the expression changes of BCL2, miR-15-b and miR-16. The results showed that extremely low frequency electromagnetic field (ELF-EMF) could significantly reduce the viability of AGS cells in the continuous MFD of 2 mT. The BCL2 expression was significantly decreased following the exposure to continuous MFDs of 0.2 and 2 mT and discontinuous MFD of 2 mT. The expressions of miR-15-b and miR-16 were significantly increased in continuous and discontinuous MFD of 2 mT. According to the results, weak and moderate extremely low-frequency electromagnetic fields can change the expressions of BCL2, miR-15-b and miR-16.

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).

The risk of lymphoma in AKR/J mice does not rise with chronic exposure to 50 Hz magnetic fields (1 microT and 100 microT)

Some epidemiological studies suggest that exposure to 50 or 60 Hz magnetic fields might increase the risk of leukemia, especially in children with a comparable high residential exposure. To investigate this possibility experimentally, the influence of 50 Hz magnetic-field exposure on lymphoma induction was determined in a mouse strain that is genetically predisposed to this disease. The AKR/J mouse genome carries the AK virus, which leads within 1 year to spontaneous development of thymic lymphoblastic lymphoma. Beginning at an age of 4-5 weeks, groups of 160 female mice were sham-exposed or exposed to 50 Hz magnetic fields at 1 or 100 microT for 24 h per day, 7 days per week, for 38 weeks. Animals were checked visually daily and were weighed and palpated weekly. There was no effect of magnetic-field exposure on body weight gain or survival rate, and lymphoma incidence did not differ between exposed and sham-exposed animals. Therefore, these data do not support the hypothesis that chronic exposure to 50 Hz magnetic fields is a significant risk factor for developing hematopoietic malignancy.

Influence of extremely low frequency magnetic fields on chromosomes and the mitotic cycle in Vicia faba L., the broad bean

Vicia faba seedlings were subjected to one of the following magnetic fields continuously for 3 days: 0 Hz (DC) at 5 mT, 50 Hz at 1.5 mT, 60 Hz at 1.5 mT, and 75 Hz at 1.5 mT. The lengths of all the phases of mitosis differed from the controls in all treatments using alternating magnetic fields and for prophase and metaphase in the DC condition. In particular, all treatments increased the length of prophase significantly in meristematic root-tip cells compared with the controls. The implications of these results for chromosome coiling are discussed. The length of prophase, however, did not vary significantly between any of the treatments. Furthermore, none of the exposed seedlings had a greater frequency of chromosome breakages above that of the control plants.

Bioelectric potential gradients may initiate cell cycling: ELF and zeta potential gradients may mimic this effect

When a number of experimental studies in bioelectromagnetics were reviewed, those in which weak, exogenous extremely low frequency (ELF) fields were applied in fixed juxtaposition to their target tissues, were found to initiate mitogenesis or mitogenesis-related signals more successfully than when the target tissue moved freely during the irradiation. It is suggested that ELF fields in fixed juxtaposition to their target tissue and implanted foreign bodies or endogenous tissues with a significant zeta potential, mimic bioelectric fields generated at wounds. When the potential is high enough, they assist healing by moving cells into the wound and stimulating quiescent cells at the wound margin to cycle. Electrophoresis may help the initial migration of cells into the wound to form a clot, and migration of fibroblasts and epithelial cells from the wound margin. When exposed for a long time in a fixed juxtaposition to a potential gradient too weak to show in situ microelectrophoresis along the cell membrane surface, surface particles may coalesce to form microclusters, where like-charged surface particles are in close proximity, and growth factor receptor oligomerization and other cycle-initiating reactions are facilitated.

60 Hz magnetic fields do not enhance cell killing by genotoxic chemicals in Ataxia telangiectasia and normal lymphoblastoid cells

Ataxia telangiectasia (AT) is an inherited autosomal recessive disease characterized by increased risk of cancer, immune deficiency, and neurodegeneration. Cells cultured from AT patients are highly sensitive to genotoxic agents and are deficient in cell cycle arrest after exposure to ionizing radiation. In consideration of their sensitivity to both ionizing and nonionizing radiation, AT cells may provide a sensitive model system to study the biological activity of other components of the electromagnetic spectrum. To characterize the effects of power-frequency (60 Hz) magnetic fields (MFs) in AT cells, we compared responses of AT and normal lymphoblast cells to sinusoidal MFs at 1.0 mT, either alone or in combination with the genotoxic agents mitomycin C or streptonigrin. The MF alone had no effect on cell growth or survival in a clonogenic assay in either AT or normal cells. The MF also had no effect on induction of cell death by mitomycin C or streptonigrin in either cell type. AT cells do not demonstrate differential sensitivity to MF exposure. These results do not support the hypothesis that MFs interact with genotoxic agents to induce adverse biological effects in either normal or genetically susceptible human cells.

Expression of cancer-related genes in human cells exposed to 60 Hz magnetic fields

Exposure to 60 Hz magnetic fields (MFs) may be a risk factor for human cancer. One mechanism through which MFs could influence neoplastic development is through alterations in the expression of cancer-related genes. Previous molecular studies of the action of MFs have measured effects on a limited number of genes. In the present studies, arrays containing cDNAs for 588 cancer-related genes were used to approach the hypothesis that the biological activity of MFs is mediated by alterations in gene expression. Cultures of normal (HME) and transformed (HBL-100) human mammary epithelial cells and human promyelocytic leukemia (HL60) cells were exposed to MFs at field strengths of 0, 0.01 or 1.0 mT for 24 h. Several genes were identified in MF-exposed cells whose expression was increased by at least twofold or decreased by 50% or more. However, no gene was found to be differentially expressed in each of three independent exposures for any cell type, and no relationship between exposure intensity and differential gene expression was found. These studies failed to identify a plausible genetic target for the action of MFs in human cells, and they provide no support for the hypothesis that MF exposure alters the expression of genes that are involved in cancer development.

Luciferase activity and synthesis of Hsp70 and Hsp90 are insensitive to 50Hz electromagnetic fields

The activity of luciferase expressed in transfected 34i cells has been monitored under 50Hz EMF and heat shock. While heat shock decreased the luciferase activity, short exposure to EMFs did not, the luciferase expressed in cells exposed to EMFs at 300-3000 microT showing the same activity as that of control cells. To further analyse whether EMF and thermal stress display similar effects, the relative rate of Hsp90 and Hsp70 synthesis was investigated. Hsp90 and Hsp70 synthesis, while induced by a short thermal stress, was not increased by EMF exposure. These results, contrary to previously proposed similarities between thermal stress and EMF effects at a cellular level, indicate that protein denaturation and misfolding caused by thermal stress and responsible both for a loss of luciferase activity and for an induction of Hsp, are not necessarily induced by exposure to EMFs.

Investigation of the effects of 50 Hz magnetic fields on purified human hematopoietic progenitors

Epidemiological reports suggest a possible association between exposure to extremely low frequency electromagnetic fields (ELF-EMFs) and the frequency of leukemia in men working in the field of electricity or in children living near power lines. At present, there is no experimental evidence for such an association. In this study we investigated the effects of 50 Hz EMFs (sinusoidal EMF of 10 microT or 1 mT) on human purified hematopoietic progenitor cells which are the first targets of a leukemogenic process. The results failed to reveal any significant changes in cell proliferation, cell kinetics, ultrastructure or clonogenic potential of these progenitors which could be related to a leukemogenic effect.

Teratogen update: electromagnetic fields

Public concern is increasing about the potential health effects of extremely low frequency (ELF) electromagnetic fields (EMFs) naturally present or generated by electrical appliances and those of very low frequency (VLF) fields, like those generated by video display terminals (VDTs). There are arguments in favour of EMFs being biologically active but no mechanism has been identified that explains the link between EMFs and bioeffects. More than 50 studies on exposures of animals to EMFs have been performed within the last few years. Although there were a few statistically significant effects in the studies reviewed, no replicable results were found among laboratories. The extent of effects observed, if any, was always low, and deserves further investigation before relevance to humans can be considered. Human data reviewed concern the potential reproductive effects (mainly) spontaneous abortions, low birthweight, and congenital malformations) of exposure to various sources of EMFs: maternal residence, heated waterbeds, electric blankets, and ceiling heating coils, occupational exposure (mainly video display terminals), and magnetic resonance imaging. The totality of the evidence that is thus far available provides no convincing evidence to indicate that low frequency EMFs of the sort that might be met in occupational or daily life exposures does any harm to the human reproductive process. It is suggested that those counseling pregnant women follow the guidelines established by WHO in agreement with the International Non-ionizing Radiation Committee. This group does not consider that the results of published studies provide a basis for restricting human exposure to electromagnetic fields and radiation.