Priming of the respiratory burst in neutrophils exposed to a combination of weak constant and alternating low-frequency magnetic fields in vitro

An hour-long exposure of peritoneal neutrophils of mice to a combination of a weak constant magnetic field (42 μT) and low-frequency alternating magnetic fields collinear to the weak constant magnetic field (frequencies 1, 4.4, and 16.5 Hz, total amplitude 0.86 μT) at physiological temperatures promoted a significant increase in chemiluminescence of cells in response to subsequent exposure to low concentrations of respiratory burst activators (formylated peptide N-formyl-Met–Leu–Phe or phorbol ester phorbol-12-myristate-13-acetate) in the presence of luminol. The response of human neutrophils isolated from peripheral blood to the pretreatment with combined magnetic fields followed by exposure to the activator N-formyl-Met–Leu–Phe was similar to the response of mouse neutrophils.     

The role of hydroxyl radicals and calcium ions in the priming of a respiratory burst in neutrophils and the increase in luminol-dependent blood chemiluminescence on exposure to combined magnetic fields with a very weak low-frequency alternating component

The intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane N,N,N′,N′-tetraacetic acid acetoxymethyl ester (BAPTA AM) used at low concentrations (1.0 and 2.5 μM) was shown to block the priming effect of weak combined static (42 μT) and low-frequency collinear alternating (1.0, 4.4, and 16.5 Hz; 0.86 μT) magnetic fields. This blockage was inferred from a greater increase in chemiluminescence observed for a mouse neutrophil suspension exposed to combined magnetic fields in response to the bacterial peptide N-formyl–Met–Leu–Phe added in the presence of luminol. Similar results were obtained for the effect of BAPTA AM on luminol-dependent chemiluminescence of whole blood. The priming effect of weak combined magnetic fields on the respiratory burst in neutrophils did not depend on the presence of extracellular Ca²⁺ and was not affected by the hydroxyl radical scavenger dimethyl sulfoxide used at 0.025–1.0 mM.     

The role of lipid peroxidation and myeloperoxidase in priming a respiratory burst in neutrophils under the action of combined constant and alternating magnetic fields

The enhancement of lipid peroxidation in neutrophils (the content of malonic dialdehyde increased by 10.2%) has been shown after a 1-h exposure to a combined constant (42 μT) magnetic field and a weak low-frequency magnetic field (1.0, 4.4, and 16.5 Hz; 860 nT) collinear to it. No correlation was found between this effect and the process of functional pre-activation (priming) of neutrophils as a result of the combined action of magnetic fields detected by chemiluminescence enhancement in response to the introduction of the bacterial peptide N-formyl–Met–Leu–Phe in the presence of luminol, since ionol (10 μM), an inhibitor of lipid peroxidation, did not reduce the neutrophil priming index in this case. Preliminary addition of histidine (0.1 and 1.0 mM), a singlet oxygen scavenger, also did not decrease the priming index. A myeloperoxidase inhibitor, sodium azide (0.1 mM), exerted a significant inhibitory effect on the chemiluminescence intensity of the neutrophil suspension; priming did not develop in the presence of this inhibitor after the action of combined magnetic fields.     

Effect of weak and ultraweak combined magnetic fields and low-intensity microwaves on regeneration in the planarian <Emphasis Type="Italic">Dugesia tigrina</Emphasis>

Regeneration (blastema growth) in Dugesia tigrina was accelerated if prior to transection the planarians were exposed to a weak constant magnetic field (42 μT) combined with an ultraweak alternating magnetic field (40 nT, 3.7 Hz); lesser stimulation was obtained with weak microwaves (100 μW/cm² at 36 GHz). Field exposure after transection produced only half of the effect (magnetic field) or none at all (microwaves).     

Effects of low-level combined static and weak low-frequency alternating magnetic fields on cytokine production and tumor development in mice

We investigated the effects of weak combined magnetic fields (MFs) produced by superimposing a constant MF (in the range 30 - 150 µT) and an alternating MF (100 or 200 nT) on cytokine production in healthy Balb/C male mice exposed 2 h daily for 14 days. The alternating magnetic field was a sum of several frequencies (ranging from 2.5 - 17.5 Hz). The frequencies of the alternating magnetic field were calculated formally based on the cyclotron resonance of ions of free amino acids (glutamic and aspartic acids, arginine, lysine, histidine, and tyrosine). The selection of different intensity and frequency combinations of constant and alternating magnetic fields was performed to find the optimal characteristics for cytokine production stimulation in immune cells. MF with a constant component of 60 μT and an alternating component of 100 nT, which was a sum of six frequencies (from 5 to 7 Hz), was found to stimulate the production of tumor necrosis factor-α, interferon-gamma, interleukin-2, and interleukin-3 in healthy mouse cells and induce cytokine accumulation in blood plasma. Then, we studied the effect of this MF on tumor-bearing mice with solid tumors induced by Ehrlich ascite carcinoma cells by observing tumor development processes, including tumor size, mouse survival rate, and average lifespan. Tumor-bearing mice exposed to a combined constant magnetic field of 60 μT and an alternating magnetic field of 100 nT containing six frequencies showed a strong suppression of tumor growth with an increase in survival rate and enhancement of average lifespan.     

Hypothesis: The risk of childhood leukemia is related to combinations of power-frequency and static magnetic fields

We present a hypothesis that the risk of childhood leukemia is related to exposure to specific combinations of static and extremely-low-frequency (ELF) magnetic fields. Laboratory data from calcium efflux and diatom mobility experiments were used with the gyromagnetic equation to predict combinations of 60 Hz and static magnetic fields hypothesized to enhance leukemia risk. The laboratory data predicted 19 bands of the static field magnitude with a bandwidth of 9.1 μT that, together with 60 Hz magnetic fields, are expected to have biological activity. We then assessed the association between this exposure metric and childhood leukemia using data from a case-control study in Los Angeles County. ELF and static magnetic fields were measured in the bedrooms of 124 cases determined from a tumor registry and 99 controls drawn from friends and random digit dialing. Among these subjects, 26 cases and 20 controls were exposed to static magnetic fields lying in the predicted bands of biological activity centered at 38.0 μT and 50.6 μT. Although no association was found for childhood leukemia in relation to measured ELF or static magnetic fields alone, an increasing trend of leukemia risk with measured ELF fields was found for subjects within these static field bands (P for trend = 0.041). The odds ratio (OR) was 3.3 [95% confidence interval (CI) = 0.4–30.5] for subjects exposed to static fields within the derived bands and to ELF magnetic field above 0.30 μT (compared to subjects exposed to static fields outside the bands and ELF magnetic fields below 0.07 μT). When the 60 Hz magnetic fields were assessed according to the Wertheimer-Leeper code for wiring configurations, leukemia risks were again greater with the hypothesized exposure conditions (OR = 9.2 for very high current configurations within the static field bands: 95% CI = 1.3–64.6). Although the risk estimates are based on limited magnetic field measurements for a small number of subjects, these findings suggest that the risk of childhood leukemia may be related to the combined effects of the static and ELF magnetic fields. Further tests of the hypothesis are proposed. © 1995 Wiley-Liss, Inc.     

Modulation of cardiac rhythm in the humans exposed to extremely weak alternating magnetic fields

The effect of extremely weak alternating magnetic fields of various types with the amplitudes δ of 2 μT on the heart rate variability in humans was studied. Volunteers were placed in a large-volume coil system (2ω2ω2 m), which provided exposure of the whole body to extremely weak alternating magnetic fields uniform in their amplitude. It was shown for the first time that the exposure to such fields could both increase and decrease the magnitude of stress in humans. In particular, the field tuned to the nuclear spins of hydrogen atoms (amplitude, 1.6 μT and frequency, 76 Hz) decreased the Baevsky stress index, whereas the field tuned to the magnetic moments formed by the orbiting electrons in some atoms (amplitude, 0.192 μT and frequency, 3000 Hz) increased this index. These results provide a possible explanation for the mechanisms of adverse effects caused by extremely weak alternating magnetic fields of certain types of both technogenic and natural origins on the human cardiovascular system.     

The Role of Oxygen in the Priming of Neutrophils on Exposure to a Weak Magnetic Field

A preliminary mild partial degassing of a neutrophil suspension at an atmospheric gas pressure of 640 mm Hg was accompanied by a decrease in oxygen to 412 ng-atom O/mL and was shown to cause a significant (fourfold) decrease in neutrophil priming index on exposure to combined weak magnetic fields (a static magnetic field of 42 μT and a low-frequency collinear alternating magnetic field of 860 nT; 1, 4.4, and 16.5 Hz) but did not affect the cell potential to generate a respiratory burst in response to an activator (the peptide N-formyl–Met–Leu–Phe) in the control. A partial replacement of the air mixture with carbogen, xenon, or sulfur hexafluoride reduced the intensity of luminol-dependent chemiluminescence of the samples.     

Extremely-low-frequency magnetic fields disrupt rhythmic slow activity in rat hippocampal slices

Several studies have indicated that weak, extremely-low-frequency (ELF; 1–100 Hz) magnetic fields affect brain electrical activity and memory processes in man and laboratory animals. Our studies sought to determine whether ELF magnetic fields could couple directly with brain tissue and affect neuronal activity in vitro. We used rat hippocampal slices to study field effects on a specific brain activity known as rhythmic slow activity (RSA), or theta rhythm, which occurs in 7–15 s bursts in the hippocampus during memory functions. RSA, which, in vivo, is a cholinergic activity, is induced in hippocampal slices by perfusion of the tissue with carbachol, a stable analog of acetylcholine. We previously demonstrated that the free radical nitric oxide (NO), synthesized in carbachol-treated hippocampal slices, lengthened and destabilized the intervals between successive RSA episodes. Here, we investigate the possibility that sinusoidal ELF magnetic fields could trigger the NO-dependent perturbation of the rate of occurrence of the RSA episodes. Carbachol-treated slices were exposed for 10 min epochs to 1 or 60 Hz magnetic fields with field intensities of 5.6, 56, or 560 μT (rms), or they were sham exposed. All exposures took place in the presence of an ambient DC field of 45 μT, with an angle of -66° from the horizontal plane. Sinusoidal 1 Hz fields at 56 and 560 μT, but not at 5.6 μT, triggered the irreversible destabilization of RSA intervals. Fields at 60 Hz resulted in similar, but not statistically significant, trends. Fields had no effects on RSA when NO synthesis was pharmacologically inhibited. However, field effects could take place when extracellular NO, diffusing from its cell of origin to the extracellular space, was chelated by hemoglobin. These results suggest that ELF magnetic fields exert a strong influence on NO systems in the brain; therefore, they could modulate the functional state of a variety of neuronal ensembles. © 1996 Wiley-Liss, Inc.     

Environmental magnetic fields inhibit the antiproliferative action of tamoxifen and melatonin in a human breast cancer cell line

We have previously reported that environmental-level magnetic fields (1.2 μT [12 milligauss], 60 Hz) block the growth inhibition of the hormone melatonin (10⁻⁹ M) on MCF-7 human breast cancer cells in vitro. We now report that the same 1.2 μT, 60 Hz magnetic fields significantly block the growth inhibitory action of pharmacological levels of tamoxifen (10⁻⁷ M). In biophysical studies we have taken advantage of Faraday's Law of Current Induction and tested whether the 1.2 μT magnetic field or the associated induced electric field is responsible for this field effect on melatonin and tamoxifen. We observe that the magnetic field component is associated with the field blocking effect on melatonin and tamoxifen function. To our knowledge the tamoxifen studies represent the first experimental evidence for an environmental-level magnetic field modification of drug interaction with human breast cancer cells. Together, these findings provide support to the theory that environmental-level magnetic fields can act to modify the action of a drug or hormone on regulation of cell proliferation. Melatonin and tamoxifen may act through different biological pathways to down-regulate cell growth, and further studies are required to identify a specific biological site of interaction for the 1.2 μT magnetic field. Bioelectromagnetics 18:555–562, 1997. Published 1997 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

A human source for ELF magnetic perturbations

ABSTRACT

Current models that frame consciousness in terms of electromagnetic field theory carry implications that have yet to be fully explored. Endogenous weak extremely low frequency (ELF) magnetic fields are generated by ionic charge flow in axons, dendrites and synaptic transmitters. Because neural tissues are transparent to such fields, these provide the basis for the globally unifying qualities required to properly describe consciousness as a field. At the same time, however, an electromagnetic approach predicts partial transmission of this 1–100 nT field, suggesting external interactions similar to the various ELF magnetic perturbations that are linked to homeostatic and endocrine-related physiological effects. It follows that humans may represent an additional, previously unrecognized source of weak (1–10 nT) ambient ELF magnetic fields.     

Weak extremely-low-frequency magnetic field-induced regeneration anomalies in the planarian Dugesia tigrina

We recently reported that cephalic regeneration in the planarian Dugesia tigrina was significantly delayed in populations exposed continuously to combined parallel DC and AC magnetic fields. This effect was consistent with hypotheses suggesting an underlying resonance phenomenon. We report here, in a parallel series of investigations on the same model system, that the incidence of regeneration anomalies presenting as tumor-like protuberances also increases significantly (P < .001) in association with exposure to weak 60 Hz magnetic fields, with peak intensities ranging between 1.0 and 80.0 μT. These anomalies often culminate in the complete disaggregation of the organism. Similar to regeneration rate effects, the incidence of regeneration anomalies is specifically dependent upon the planaria possessing a fixed orientation with respect to the applied magnetic field vectors. However, unlike the regeneration rate effects, the AC magnetic field alone, in the absence of any measurable DC field, is capable of producing these anomalies. Moreover, the incidence of regeneration anomalies follows a clear dose-response relationship as a function of AC magnetic field intensity, with the threshold for induced electric field intensity estimated at 5 μV/m. The addition of either 51.1 or 78.4 μT DC magnetic fields, applied in parallel combination with the AC field, enhances the appearance of anomalies relative to the 60 Hz AC field alone, but only at certain AC field intensities. Thus, whereas our previous study of regeneration rate effects appeared to involve exclusively resonance interactions, the regeneration anomalies reported here appear to result primarily from Faraday induction coupling. These results together with those reported previously point to two distinct physiological effects produced in regenerating planaria by exposure to weak extremely-low-frequency (ELF) magnetic fields. They further suggest that the planarian, which has recently been identified elsewhere as an excellent system for use in teratogenic investigations involving chemical teratogens, might be used similarly in teratogenic investigations involving ELF magnetic fields. © 1996 Wiley-Liss, Inc.     

Increased dexamethasone-induced apoptosis of thymocytes from mice exposed to long-term extremely low frequency magnetic fields

To address the effect of extremely low frequency electromagnetic fields on programmed cell death we assessed both the spontaneous and dexamethasone (Dex)-induced apoptosis of thymocytes and spleen cells from mice submitted to a long-term continuous exposure of a 0.4–1.0 μT 60 Hz magnetic field or an 8–20 μT direct current (DC) magnetic field. Dex-induced apoptosis but not spontaneous apoptosis was substantially increased in thymocytes from 0.4 to 1.0 μT 60 Hz field-exposed animals. Spontaneous apoptosis and Dex-induced apoptosis of spleen cells were not affected by the 0.4–1.0 μT 60 Hz field exposure. In addition, spontaneous apoptosis and Dex-induced apoptosis of thymocytes and spleen cells from mice exposed to an 8–20 μT DC field were similar to the controls. These findings represent the first demonstration that thymocytes from mice exposed to a long-term 0.4–1.0 μT 60 Hz field may show abnormal response to Dex apoptotic stimuli. Bioelectromagnetics 19:131–135, 1998. © 1998 Wiley-Liss, Inc.     

Influence of 50-Hz magnetic fields and ionizing radiation on c-jun and c-fos oncoproteins

The effect of magnetic fields (50 Hz, 100 μT_rms sinusoidal magnetic field combined with a 55 μT geomagnetic-like field) and/or gamma rays of 60 Cobalt on the expression of the c-jun and c-fos proteins was investigated in primary rat tracheal epithelial cells and two related immortalized cell lines. Quite similar patterns and amplitudes of induction of these proteins were evidenced after either ionizing radiation or magnetic field exposure. No synergism after both treatments was observed. These findings suggest that magnetic fields explored in the present study may be considered as an insult at the cellular level. Bioelectromagnetics 19: 112–116, 1998. © 1998 Wiley-Liss, Inc.     

Behavioural evidence that magnetic field effects in the land snail,Cepaea nemoralis,might not depend on magnetite or induced electric currents

Although extremely low frequency (ELF) magnetic fields (<300 Hz) appear to exert a variety of biological effects, the magnetic field sensing/transduction mechanism(s) remains to be established. Here, using the inhibitory effects of magnetic fields on endogenous opioid peptide-mediated “analgaesic” response of the land snail. Cepaea nemoralis, we addressed the mechanism(s) of action of ELF magnetic fields. Indirect mechanisms involving both induced electric fields and direct magnetic field detection mechanisms (e.g., magnetite, parametric resonance) were evaluated. Snails were exposed to a static magnetic field (B_DC=78±1 μT) and to a 60 Hz magnetic field (B_AC=299±1 μT peak) with the angle between the static and 60 Hz magnetic fields varied in eight steps between 0° and 90°. At 0° and 90°, the magnetic field reduced opioid-induced analgaesia by approximately 20%, and this inhibition was increased to a maximum of 50% when the angle was between 50° and 70°. Because B_AC was fixed in amplitude, direction, and frequency, any induced electric currents would be constant independent of the B_AC/B_DC angle. Also, an energy transduction mechanism involving magnetite should show greatest sensitivity at 90°. Therefore, the energy transduction mechanism probably does not involve induced electric currents or magnetite. Rather, our results suggest a direct magnetic field detection mechanism consistent with the parametric resonance model proposed by Lednev. © 1996 Wiley-Liss, Inc.     

Design and characterization of a system for exposure of cultured cells to extremely low frequency electric and magnetic fields over a wide range of field strengths

A system is described that is capable of producing extremely low frequency (ELF) magnetic fields for relatively short-term exposure of cultured mammalian cells. The system utilizes a ferromagnetic core to contain and direct the magnetic field of a 1,000 turn solenoidal coil and can produce a range of flux densities and induced electric fields much higher than those produced by Helmholtz coils. The system can generate magnetic fields from the microtesla (μT) range up to 0.14 T with induced electric field strengths on the order of 1.0 V/m. The induced electric field can be accurately varied by changing the sample chamber configuration without changing the exposure magnetic field. This gives the system the ability to separate the bioeffects of magnetic and induced electric fields. In the frequency range of 4–100 Hz and magnetic flux density range of 0.005–0.14 T, the maximum total harmonic distortion of the induced electric field is typically less than 1.0%. The temperature of the samples is held constant to within 0.4°C by constant perfusion of warmed culture medium through the sample chamber. © 1993 Wiley-Liss, Inc.     

Effects of Applied Electric Fields on Bile Salt Secretion by in Situ Rat Liver

The effects of weak external electric fields (1.5–3 V, 30–60 μA) on bile salt secretion by jji situ rat liver were studied after interruption (experiment A) and restoration (experiment B) of the enterohepatic bile salt cycle. In experiment A, bile salt tracer was injected in bolus 3 hr after application of the electric field (¹⁴C-TC, ¹⁴C-CA, or ¹⁴C-DCA). In experiment B, 36 μmoles/h of TC or CA were infused 150 min after application of the electric field until the end of the experiment. A bolus (¹⁴C-TC and ¹⁴C-CA) was injected 170 min after application of the electric field. The hepatic taurine pool was prelabeled in both experiments.

Application of electric fields delayed secretion of ¹⁴C-TC into the bile. This delay was longer at 60 μA than at 30 μA Neither field had any effect on ³H-tauroconjugation. Electric fields also led to the formation of osmiophilic globules in hepatocytes and, especially in experiment B, collagen fibers in intracellular spaces. Thus electric fields may provoke changes in plasmic membranes probably in connection with those in the extracellular matrix.     

Impact of weak permanent magnetic field on antioxidant enzyme activities in radish seedlings

The impact of weak permanent magnetic field (PMF) with magnetic flux density of 185–650 μT on activities of antioxidant enzymes in 5-day-old radish (Raphanus sativus L. var. radicula D.C.) seedlings, cv, Rosovo-krasnyi s belym konchikom was demonstrated. In the range of 185–325 μT PMF suppressed superoxide dismutase (SOD) activity in seedling grown in darkness and catalase (CAT) grown in both darkness and light. At the same values of magnetic flux density, all fractions of guaiacol peroxidase were activated and MDA accumulation was enhanced. At the higher values of magnetic flux density, SOD was activated in seedlings grown in darkness and CAT was activated in seedlings grown in both darkness and light. Other indices decreased or remained unchanged. It was concluded that PMF action depends on its intensity: at its low values, antioxidant enzymes are inhibited and at high values — activated.     

Effect of sinusoidal 50 Hz magnetic field on the testosterone production of mouse primary Leydig cell culture

This study evaluated the effect of sinusoidal 50 Hz magnetic field on the basal and human chorionic gonadotropin (hCG)-stimulated testosterone (T) production of 48-h mouse Leydig cell culture. The luteinizing hormone (LH) analog hCG was used to check the T response of the controls and to evaluate the possible effect of the applied magnetic field on the steroidogenic capacity of the exposed cells. Leydig cells were obtained from the testes of 35- to 45-g CFLP mice and isolated by mechanical dissociation without enzyme treatment. The cell cultures were exposed to sinusoidal 50 Hz 100 μT (root mean square) AC magnetic field during the entire time of a 48-h incubation. Testosterone content of the culture media was measured by radioimmunoassay. In cultures exposed to the magnetic field, a marked increase of basal T production was found (P < .05), compared with the unexposed controls, whereas no significant difference was seen between the exposed or unexposed cultures in the presence of maximally stimulating concentration of hCG. These findings demonstrate that sinusoidal 50 Hz 100 μT magnetic fields are able to stimulate the basal T production of primary mouse Leydig cell culture, leaving the steroidogenic responsiveness to hCG unaltered. Bioelectromagnetics 19:429–431, 1998. © 1998 Wiley-Liss, Inc.