Transcriptional patterns in the X chromosome of Sciara coprophila following exposure to magnetic fields

Temperature and magnetic field effects on the activity of protocerebral neurosecretory neurons and corpora allata in Cerambyx cerdo L. larvae

The effects of constant temperature and an extremely low-frequency magnetic field (ELFMF, 50 Hz and average induction of 20 mT) on the activity of medial protocerebral neurosecretory neurons (A1 and A2) and corpora allata were investigated in Cerambyx cerdo L. larvae after 30 days of exposure. Both constant temperature of 23?C and the ELFMF led to decrease in activity of A1 and A2 neurosecretory neurons and increase in activity of corpora allata compared to the control group (larvae from natural conditions). The changes are more pronounced in A2 than A1 neurons.

The effect of 50 Hz magnetic field on GCSmRNA expression in lymphoma B cell by mRNA differential display

Magnetic fields (MFs) of various characteristics can lead to plethora effects in biological system. From a molecular point of view, we hypothesized that there must be a fundamental difference in gene expression between the MF exposed and the unexposed cell. To identify the classes of genes that are regulated, 0.8 mT 50 Hz MF-induced changes in gene expression were examined in a Daudi cell culture using differential display and reverse transcriptase-polymerase chain reaction. A candidate cDNA (signatured as MF-CB) that was observed in the sham-exposed but not in MF-exposed cultures was recovered and reamplified. After verification by Northern blot, the cDNA was cloned and sequenced. It was found that 254-base pair of 5'-end MF-CB cDNA clone was identical to gcs in open reading frame (ORF) range. Based on the preliminarily sequence, the prolonged length of 5'-end MF-CB cDNA was obtained by PCR amplification and its sequence analysis showed the same results as its original fragment. In order to further determine whether MF-CB cDNA is from gcs, two Northern blots were probed with gcs and MF-CB cDNA, respectively, and the data revealed signals of the same size and expression pattern on the two probe filters, which demonstrated that MF-CB is an EST (expression sequence tag) of gcs. gcs is a gene, identified recently (GenBank accession number D89866), encoding ceramide glucosyltransferase (GCS), which has been implicated as a causal element in human cell growth and differentiation. In an additional experiment, time-dependent changes in the transcription of gcs induced by 0.8 mT MF were observed by Northern blot with a sharp and reproducible inhibition effect after 20 min exposure and a reduction after 20-24 h exposure. The study demonstrates for the first time that 50 Hz MF can lead to changes in gcs transcription, which provides a new clue to elucidate the mechanism by which MF influence cell growth and differentiation.

Effects of low-intensity AC and/or DC electromagnetic fields on cell attachment and induction of apoptosis

Rat tendon fibroblast (RTF) and rat bone marrow (RBM) osteoprogenitor cells were cultured and exposed to AC and/or DC magnetic fields in a triaxial Helmholtz coil in an incubator for up to 13 days. The AC fields were at 60 and 1000 Hz and up to 0.25 mT peak to peak, and the DC fields were up to 0.25 mT. At various combinations of field strengths and frequencies, AC and/or DC fields resulted in extensive detachment of preattached cells and prevented the normal attachment of cells not previously attached to substrates. In addition, the fields resulted in altered cell morphologies. When RTF and RBM cells were removed from the fields after several days of exposure, they partially reattached and assumed more normal morphologies. An additional set of experiments described in the Appendix corroborates these findings and also shows that low-frequency EMF also initiates apoptosis, i.e., programmed cell death, at the onset of cell detachment. Taken together, these results suggest that the electromagnetic fields result in significant alterations in cell metabolism and cytoskeleton structure. Further work is required to determine the relative effect of the electric and magnetic fields on these phenomena. The research has implications for understanding the role of fields in affecting bone healing in fracture nonunions, in cell detachment in cancer metastasis, and in the effect of EMF on organisms generally.

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.

Effects of extremely low frequency electromagnetic field (EMF) on collagen type I mRNA expression and extracellular matrix synthesis of human osteoblastic cells

Human osteoblastic cells were grown in a three-dimensional (3-D) cell culture model and used to test the effects of a 20 Hz sinusoidal electromagnetic field (EMF; 6 mT and 113 mV/cm max) on collagen type I mRNA expression and extracellular matrix formation in comparison with the effects of growth factors. The cells were isolated from trabecular bone of a healthy individual (HO-197) and from a patient presenting with myositis ossificans (MO-192) and grown in a collagenous sponge-like substrate. Maximal enhancement of collagen type I expression after EMF treatment was 3.7-fold in HO-197 cells and 5.4-fold in MO-192 cells. Similar enhancement was found after transforming growth factor-beta (TGF-beta) and insulin-like growth factor-I (IGF-I) treatment. Combined treatment of the cells with EMF and the two growth factors TGF-beta and IGF-I did not act synergistically. MO-192 cells produced an osteoblast-characteristic extracellular matrix containing collagen type I, alkaline phosphatase, and osteocalcin, together with collagen type III, TP-1, and TP-3, two epitopes of an osteoblastic differentiation marker. The data suggest that the effects of EMFs on osteoblastic differentiation are comparable to those of TGF-beta and IGF-I. We conclude that EMF effects in the treatment of skeletal disorders and in orthopedic adjuvant therapy are mediated via enhancement of collagen type I mRNA expression, which may lead to extensive extracellular matrix synthesis.

Sources of magnetic sensory input to identified neurons active during crawling in the marine mollusc Tritonia diomedea

Although the nudibranch mollusc Tritonia diomedea orients to the geomagnetic field, the anatomical site and the mechanism of the geomagnetic transducer are not known. Previous work on semi-intact preparations of Tritonia diomedea in which the brain is intact and nerve connections to the periphery are maintained showed that identifiable pedal ganglion neurons Pd5 fired an increased number of action potentials when the horizontal component of the ambient magnetic field was rotated. This response disappeared when all nerves emerging from the brain were cut, suggesting a peripheral locus for the geomagnetic transducer. In the present work, we recorded intracellularly from Pd5 in preparations in which all peripheral nerves were cut except those containing the axons of neurons Pd5 (pedal nerves 2 and 3). These uncut, mixed, sensory-motor trunks innervate the locomotory epithelium of the foot upon which the animal crawls. In this further-reduced preparation, Pd5 again responded to magnetic field rotations with action potentials. To determine the direction of this action potential transmission in response to magnetic field rotations, we analyzed extracellular recordings from nerves containing the Pd5 axons and found that action potentials elicited in Pd5 by magnetic stimuli originate centrally and are transmitted peripherally. In addition, we have explored the behavioral function of Pd5 neurons by simultaneously recording intracellular electrical activity and crawling rate of the semi-intact animal. A significant correlation was found between crawling rate and Pd5 action potential rate. We also found that action potentials in dorsal swim interneurons depolarized both Pd5 and the established locomotion motoneuron Pd21.

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.

Exposure of Drosophila melanogaster embryonic cell cultures to 60-Hz sinusoidal magnetic fields: assessment of potential teratogenic effects

There is considerable concern about potential detrimental health effects associated with exposure to environmentally relevant magnetic fields. One specific concern relates to potential effects of magnetic field (MF) exposure on reproduction and development. Consequently, an in vitro teratogenesis (developmental toxicity) assay employing embryonic Drosophila cells has been used to determine whether exposure to a 60-Hz MF of 100 microT for 16-18 hr is itself teratogenic and whether such an exposure could potentiate the teratogenic response induced by a chemical teratogen (developmental toxicant). The results demonstrated that (1) MF exposure alone did not induce a teratogenic response, whether the MF was oriented parallel or perpendicular to the plane of the culture dishes; and (2) MF exposure did not alter the teratogenic response induced by optimal or suboptimal concentrations of three chemical teratogens (retinoic acid, hydroxyurea, and cadmium). Furthermore, in additional studies, Drosophila embryos were exposed to 60-Hz MFs of 10 and 100 microT for 24 hr or for their entire development time (i.e., until adult ecolsion, about 10 days). Results demonstrated that MF exposure did not produce an increase in developmental abnormalities over those observed in unexposed controls.

Effect of magnetic fields on rodent monooxygenase enzymes

The effects of 50 Hz, 1.2 mT magnetic fields (MFs) were tested on hepatic monooxygenase enzymes of basal and beta-naphthoflavone-phenobarbital-preinduced rats and mice. An inductive effect on cytochrome P-450 level and on some enzymatic cytochrome P-450-dependent activities was observed in basal mice after MF exposure. Enzymatic activities in preinduced mice and rats were reduced by MFs, the degree of reduction depending on the enzyme. A specific inhibitory effect was determined in some of the assayed activities and in the relative peculiar P-450 isoforms detected by Western blot analysis.

Environmental magnetic fields: influences on early embryogenesis

A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of "early" histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established.

Effects of electromagnetic field exposure on gene transcription

Exposure of whole animals, isolated tissues, and cells to electromagnetic fields of various characteristics has resulted in a substantial literature detailing a wide range of effects at the morphological, physiological, biochemical, and molecular levels. In recent years, considerable effort has been devoted to defining a mechanism by which electromagnetic fields can couple to biological systems and generate this plethora of effects. As a consequence, there has been a growing interest in electromagnetic field-induced alterations in gene expression. Key studies are discussed which indicate that exposure of several cell types to electromagnetic fields that differ in waveform, amplitude, and frequency induced general changes in gene transcription. Moreover, exposure of T-lymphoblastoid cells to a 60 Hz sinusoidal magnetic field altered the transcription of genes encoding c-fos, c-jun, c-myc, and protein kinase C. Future studies in this area should focus on independent replication of key studies and identification of which events in the signal transduction pathways leading to gene transcription are altered by electromagnetic field exposure.

Magnetic field-induced changes in specific gene transcription

Magnetic fields are physical, environmental agents that have been shown to produce a variety of responses in cellular and animal studies, including general changes in gene transcription. In this study, the nuclear run-off assay has been employed to assess alterations in specific gene transcription in CEM-CM3 T-lymphoblastoid cells exposed for 15-120 min to a 1 gauss sinusoidal magnetic field at 60 Hz. Time-dependent and cell density-dependent changes in the transcription of c-fos, c-jun, c-myc and protein kinase C (beta-form) have been observed and quantitated. Additionally, changes in transcript levels, assessed by slot-blot analysis, have been found to parallel the changes in gene transcription. These data suggest an important role for magnetic field exposure in altering cellular processes.

Transcription in Drosophila melanogaster salivary gland cells is altered following exposure to low-frequency electromagnetic fields: analysis of chromosome 3R

The use of the transcription autoradiographic method permits identification of nascent RNA chains directly on identifiable regions of Drosophila salivary gland chromosomes. Changes in transcriptional activity at 13 defined regions of the right arm of chromosome 3 (3R) were observed following 20-min exposures of salivary glands to five different extremely low frequency (ELF) electromagnetic (EM) fields. Changes in translational patterns were also induced by the ELF EM fields in exposed cells. Differences included an increase in over-all polypeptide synthesis as well as in the number of polypeptides resolved in cells exposed to EM fields.

Dose-response implications of the transient nature of electromagnetic-field-induced bioeffects: theoretical hypotheses and predictions

Data in the literature imply that the relationship between exposure and bio-effect involves more than a simple time integral of the field strength to which the living system has been subjected. Windows--ranges in which the system exhibits enhanced sensitivity--have been reported for power (or field strength), frequency, and the duration of the exposure. In this paper we show that such isolated window effects can be accounted for by recognizing the transient character of the response of the biological system. The principal assumption here is that the direct effect of the field is to increase the rates of production and degradation of mRNA or proteins. In this paper we review and extend the mathematical model that quantifies this. The model predicts that, for a given field strength, certain optimum relatively short duration exposures cause significantly larger bio-effects than exposure for much longer or much shorter times. The thinking embodied in the model should provide a framework for obtaining a meaningful working definition of "effective dose" and for predicting the response of subjects to environmental electromagnetic fields. It should help in deciding the relevant variables in the design and analysis of epidemiological studies.

Sex-linked recessive lethal test of Drosophila melanogaster after exposure to 50-Hz magnetic fields

To determine whether a 50-Hz magnetic field will induce mutations, a sex-linked recessive lethal test of Drosophila melanogaster was performed. Adult flies were exposed at an rms flux density of 500 mu T or 5 mT to the homogeneous field of a Helmholtz coil. The ambient field to which controls were exposed was less than 1 mu T. Exposures took place continuously for 13 to 14 days, which correspond to the life cycle of Drosophila at 25 degrees C. About 10,000 X-chromosomes were tested at each flux density. Recessive lethal mutation rates of 0.13, 0.21, and 0.18 percent were observed, respectively, for control, 500-mu T, and 5-mT conditions. By the Kastenbaum-Bowman significance test, the recessive lethal mutation rates in the 500-mu T and 5-mT conditions did not differ from the mutation rate of controls.

Cancer promotion in a mouse-skin model by a 60-Hz magnetic field: II. Tumor development and immune response

This paper describes preliminary findings on the influence of 60-Hz (2-mT) magnetic fields on tumor promotion and co-promotion in the skins of mice. The effect of magnetic fields on natural killer (NK) cell activity in spleen and blood was also examined. Groups of 32 juvenile female mice were exposed to the magnetic field as described in part I. The dorsal skin of all animals was treated with a subthreshold dose of the carcinogen 7,12-dimethyl-benz(a)anthracene (DMBA). One week after the treatment, two groups were sham exposed (group A) or field exposed at 2 mT (group B) 6 h/day for 21 weeks, to test whether the field would act as a tumor promoter. No tumors developed in these two groups of mice. To test whether the magnetic field would modify tumor development by directly affecting tumor growth or by suppressing immune surveillance, two additional groups of mice were treated weekly with the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA) and then either sham exposed (group C) or field exposed (group D). The time to appearance of tumors was shorter (but not statistically so) in the group exposed to magnetic fields and TPA. Some differences in NK cell activity and spleen size were observed between the sham- and field-exposed groups.

Effect of pulsed magnetic fields on leukemia-prone AKR mice. No-effect on mortality through five generations

Leukemia-prone AKR mice were exposed twice a week to a 6 mT, 12 Hz or 460 Hz pulsed magnetic field for 30 min. If we take into account the five consecutive generations of mice, the above exposure actually took place in utero and, or during their life span. There was no difference in the incidence of leukemia or in the actuarial survival curves or in the average spleen or thymus weights.

Lack of acute effects of 20 mT, 50 Hz magnetic fields on murine haemopoiesis

Some epidemiological studies have drawn attention to a possible association between exposure to extremely low-frequency (ELF) electromagnetic fields and the development of acute myeloid leukaemia (AML) in adults. At present there is no experimental evidence for such an association. We have investigated the acute effects of power frequency magnetic fields on haemopoiesis in CBA/H mice known to be susceptible to the induction of AML after exposure to ionizing radiation. Up to 19 days after exposure to 50 Hz fields at 20 mT for 7 days no significant effects on peripheral blood characteristics were observed. Assays of the bone marrow stem cells and myelomonocytic progenitor cells also failed to reveal significant effects. Our experiments cannot, however, rule out subtle effects on cell population dynamics, and further investigations, including long-term studies, are required to establish the extent to which ELF magnetic fields might affect the haemopoietic system.

Influence of 60-Hz magnetic fields on sea urchin development

Continuous exposure of sea urchin (Strongylocentrotus purpuratus) embryos at 18 degrees C to a cyclic 60-Hz magnetic field at 0.1 mT rms beginning 4 min after insemination caused a significant developmental delay during the subsequent 23 hours. No delay in development was recorded for periods up to 18 hours after fertilization. At 18 h, most embryos were in the mesenchyme blastula stage. At 23 h, most control embryos were in mid-gastrula whereas most magnetic-field-exposed embryos were in the early gastrula stage. Thus an estimated 1-h delay occurred between these developmental stages. The results are discussed in terms of possible magnetic-field modification of transcription as well as interference with cell migration during gastrulation. The present study extends and supports the growing body of information about potential effects of exposures to extremely-low-frequency (ELF) magnetic fields on developing organisms.

Exposure of human cells to low-frequency electromagnetic fields results in quantitative changes in transcripts

The exposure of human cultured cells to electromagnetic signals with extremely low repetition rates resulted in an increased level of selected RNA transcripts. RNA with homology to beta-actin, histone H2B, and v-myc DNA was monitored by dot blot hybridization following 20 min exposures of HL60 cells to five different electromagnetic signals. The experiments used three asymmetric electromagnetic signals with different repetition rates, and two symmetric sinusoidal signals, delivered at 60 and 72 Hz. The degree of increase in homologous transcripts was dependent on the signal characteristics.

Biological effects of weak electromagnetic fields from 0 Hz to 200 MHz: a survey of the literature with special emphasis on possible magnetic resonance effects

The literature on biological effects of weak electromagnetic fields of a frequency of 200 MHz or less is surveyed. The topic has been extraordinarily controversial, in part because of disputed assertions about a role for electromagnetic fields in carcinogenesis or production of abnormalities in growth and development. There is fairly widespread acceptance of certain beneficial effects, particularly the stimulation of healing. An increasing number of reports point to interactions between static magnetic fields and time-varying fields in the production of some effects. Safety implications are noted along with the hypothetical possibility of production of experimental artifacts by electromagnetic fields in MRS research.

Multiple power-density windows and their possible origin

We have previously reported that in vitro exposure of chick forebrain tissue to 50-MHz radiofrequency (RF) electromagnetic radiation, amplitude modulated (AM) at 16 Hz, would enhance the efflux of calcium ions within only two power-density ranges: one from 1.44 to 1.67 mW/cm2, and the other including 3.64 mW/cm2. No effect on efflux occurred at 0.37, 0.72, 2.17, and 4.32 mW/cm2. We confirmed and extended these results by testing at another set of power densities, which included the range of the previous study. Forebrain tissue from 1-7-day-old chickens was labeled in vitro with radioactive calcium ions (30 min, at 37 degrees C), rinsed, placed in a physiological salt solution, and then exposed for 20 min to 50-MHz radiation, AM at 16 Hz, in a transverse electric and magnetic field (TEM) cell maintained at 37 degrees C. The solution was then assayed for radioactive calcium activity. A power-density series was tested. An enhanced efflux of calcium ions was found at 1.75, 3.85, 5.57, 6.82, 7.65, 7.77, and 8.82 mW/cm2; no change was observed at 0.75, 2.30, 4.50, 5.85, 7.08, 8.19, 8.66, 10.6, and 14.7 mW/cm2. Power density is converted to specific absorption rate (SAR) by 0.36 mW/kg per mW/cm2. Even the highest SAR tested (0.005 W/kg) is much too low to result in generalized heating of the sample and thus to be the underlying cause of the enhanced response. A hypothetical mechanism is proposed involving dynamic systems that may account for the power-density dependency as well as for part of the frequency dependency observed with both modulated RF radiation and extremely-low-frequency (ELF) fields.

Exposure of salivary gland cells to low-frequency electromagnetic fields alters polypeptide synthesis

This study demonstrates that exposure of cells to extremely low-frequency electromagnetic fields can cause measurable changes in protein synthesis. Sciara coprophila salivary gland cells were exposed to five low-frequency (1.5-72 Hz) electromagnetic signals: three signals (1.5, 15, and 72 Hz) produced pulsed asymmetric electromagnetic fields and two signals (60 and 72 Hz) were sinusoidal. Subsequent analyses of two-dimensional gels showed that cell exposure to either type of low-frequency electromagnetic field resulted in both qualitative and quantitative changes in patterns of protein synthesis. Thus, signals producing diverse waveform characteristics induced previously undetectable polypeptides, some of which were signal specific and augmented or suppressed other polypeptides as compared with nonexposed cells. The pattern of polypeptide synthesis differed from that seen with heat shock: only five polypeptides in cells exposed to electromagnetic signals overlap those polypeptides exposed to heat shock, and the suppression of protein synthesis characteristic of heat shock does not occur.