Low Frequency Pulsed Magnetic Fields Research Articles

Human subjects exposed to a specific pulsed extremely low frequency magnetic field: Effects on standing balance

Extremely low frequency pulsed magnetic fields (±200 μT, ∼400 mT/s, 0–1 kHz) may produce electric currents similar to action potentials, which in turn would be expected to produce detectable physiological or behavioral effects in human subjects. This thesis reports on the effects of pulsed extremely low frequency magnetic fields (ELFMFs) on human standing balance by measurement of postural sway on a force platform utilizing a double blind protocol with four randomly assigned 2 min exposure conditions (eyes open/closed, sham/ELFMF) within each subject's session. Historically, and in current research by others, normal postural sway has been well characterized. Standing balance in humans is a largely automatic behavior and with “eyes open” is a robust behavior not easily disrupted by small perturbations. However, with “eyes closed” standing balance becomes very sensitive to perturbation by a wide variety of stimuli. Since we have shown that ELFMF perturbs human postural sway, measurements of standing balance may be an ideal method of investigating bioelectromagnetic coupling mechanisms in humans (i.e., peripheral versus central nervous system mechanisms). Ideal because, being under automatic control, standing balance is an objective measure not subject to placebo effects. The coupling mechanisms can be studied by examining the effects related to different anatomical location of ELFMF exposure, or studying patients with different pathology. This thesis has established that normal standing balance is perturbed by weak ELFMF for both eyes open/eyes closed conditions. Also, it has been established that this human assay may indeed be appropriate to study coupling mechanisms, since the ability of ELFMF to affect sway varies between patients with diseases affecting different anatomical and physiological centers.

Elf-pulsed magnetic fields modulate opioid peptide gene expression in myocardial cells.

Magnetic fields have been shown to affect cell proliferation and growth factor expression in cultured cells. Although the activation of endorphin systems is a recurring motif among the biological events elicited by magnetic fields, compelling evidence indicating that magnetic fields may modulate opioid gene expression is still lacking. We therefore investigated whether extremely low frequency (ELF) pulsed magnetic fields (PMF) may affect opioid peptide gene expression and the signaling pathways controlling opioid peptide gene transcription in the adult ventricular myocyte, a cell type behaving both as a target and as a source for opioid peptides. Prodynorphin gene expression was investigated in adult rat myocytes exposed to PMF by the aid of RNase protection and nuclear run-off transcription assays. In PMF-exposed nuclei, nuclear protein kinase C (PKC) activity was followed by measuring the phosphorylation rate of the acrylodan-labeled MARCKS peptide. The effect of PMF on the subcellular distribution of different PKC isozymes was assessed by immunoblotting. A radioimmunoassay procedure coupled to reversed-phase high performance liquid chromatography was used to monitor the expression of dynorphin B. Here, we show that PMF enhanced myocardial opioid gene expression and that a direct exposure of isolated myocyte nuclei to PMF markedly enhanced prodynorphin gene transcription, as in the intact cell. The PMF action was mediated by nuclear PKC activation but occurred independently from changes in PKC isozyme expression and enzyme translocation. PMF also led to a marked increase in the synthesis and secretion of dynorphin B. The present findings demonstrate that an opioid gene is activated by myocyte exposure to PMF and that the cell nucleus and nuclear embedded PKC are a crucial target for the PMF action. Due to the wide ranging importance of opioid peptides in myocardial cell homeostasis, the current data may suggest consideration for potential biological effects of PMF in the cardiovascular system.

Cytogenetic effects induced by extremely low frequency pulsed magnetic fields in lymphocytes from Turner's syndrome subjects

The cytokinesis-block micronucleus assay was applied to evaluate the genotoxic effect of in vitro exposure to extremely low frequency pulsed magnetic fields on peripheral blood lymphocytes from 10 subjects aged between 3 and 24 years and affected by Turner's syndrome, in comparison with 8 healthy donors aged between 3 and 22 years. We report a significant ( p < 0.01) micronucleus frequency increase in lymphocyte cultures from Turner's syndrome patients after 72 h exposure to pulsed magnetic fields with respect to unexposed cultures obtained from blood of the same subject. Such an increase of micronucleus frequency after exposure to pulsed magnetic fields was not observed in the control group, in accordance with our previous data in a large cohort of healthy subjects of different ages. The cytokinesis-block proliferation index was also evaluated both in cultures from Turner's syndrome patients and from healthy donors and resulted slightly higher in the exposed cultures, for both groups, even if the increase was not statistically significant. The relevance of these results for the studies on the biological effects of pulsed magnetic fields and for the related possible genotoxic risk in subgroups of human subjects characterised by particular genetic or pathological status is discussed.

Spontaneous and mitomycin-C-induced micronuclei in human lymphocytes exposed to extremely low frequency pulsed magnetic fields

The cytokinesis block micronucleus method, a very sensitive cytogenetic assay, was used to ascertain the possible genotoxic effects of extremely low frequency pulsed magnetic fields in phytohemagglutinin-stimulated human lymphocytes cultures from 16 healthy donors. Four conditions were studied: i) lymphocytes not exposed to the field (control cultures); ii) lymphocytes exposed to the field; iii) lymphocytes treated with mitomycin-C and not exposed to the field; iv) lymphocytes treated with mitomycin-C and exposed to the field. Mitomycin-C-treated cultures were used as control for the micronucleus method, because it is known that mitomycin-C is a potent genotoxic agent, capable of inducing micronuclei. The frequency of micronuclei in field-exposed cultures was similar to the spontaneous frequency observed in control unexposed-cultures. Moreover, the exposure to pulsed magnetic fields did not affect the frequency of micronuclei induced by mitomycin-C, suggesting that, in the experimental conditions used, this kind of field neither affected the integrity of chromosomes nor interfered with the genotoxic activity of mitomycin-C.

The effect of low-frequency pulsed magnetic fields on chick embryonic growth

There are many claims made for biological effects of low-frequency pulsed magnetic fields ranging from beneficial to harmful, but few have been independently verified. The ubiquitous nature of both natural and man-made magnetic fields makes the possibility of biological interaction a potentially important subject. The authors have investigated the claimed stimulatory action of low-frequency pulsed magnetic fields, of a type used clinically, on the growth of embryonic chicks. Four day old embryos were exposed to a magnetic field, peak field strength 2.1 mT pulsed in 5 ms bursts repeated at 15 Hz for 100 h. Embryo weights and long-bone lengths were compared to sham-exposed controls. Particular care was taken to reduce temperature differences between the test and control groups because this model has a known sensitivity to small temperature changes. The authors found no increase in embryonic growth due to this low-frequency pulsed magnetic field.

The Canadian Experience with Pulsed Magnetic Fields in the Treatment of Ununited Tibial Fractures

A clinical survey of 56 patients was conducted at four different centers in Canada to evaluate the effect of extremely low frequency pulsed magnetic fields (PMF) on ununited fractures of the tibia. All ten patients with delayed union and 84% of the 44 patients with nonunion healed. One case with a traumatic pseudarthrosis and one with a congenital pseudarthrosis failed to respond to treatment. These results compare favorably to those reported by others using a system with different pulse characteristics. Prolonged immobilization is necessary and poses problems of rehabilitation. Nonunions with a gap between the tibial fragments and pseudarthroses are better treated with bone grafting and internal fixation prior to electrical stimulation.

Low frequency pulsed magnetic fields do not modify several aspects of ion transport in biological materials

Pulsed magnetic fields (P.M.F.s) are widely used to promote fracture repair in delayed unions of bone, yet it is not clear how they interact with biological materials. It has been proposed that induced currents impinging on cell membranes may contribute to their ion transport function, leading to ion-dependent changes in metabolism. This hypothesis was tested by treating in vitro models for ion transport processes with short-term exposure to P.M.F.s. No change occurred in active transport of potassium or calcium in human red cells, or calcium transport through an epithelial membrane, nor were passive movements of ions altered by P.M.F.s. An indirect mechanism was considered: connective tissue matrices sequester ions according to their Donnan potential. The electric fields associated with spatial variation in Donnan potential are small, so that pulsed magnetic fields might interact with them and displace ions from the matrix, hence modifying ion transport in connective tissue cells. Results showed, however, that calcium accumulation in cartilage matrices was insensitive to P.M.F.s. From these studies it seems unlikely, therefore, that modification of cellular ion transport is the initial interaction between pulsed magnetic fields and biological materials.

A system for investigating the in vitro effects of low-frequency pulsed magnetic fields.

Describes an experimental system used to demonstrate changes in nor-adrenaline release from cells in culture caused by a pulsed magnetic field. The equipment was designed to facilitate a study of the mechanisms of the interaction between the field and the cells by subjecting the cells to a well defined stimulus.