Effects of pulsed magnetic stimulation on isolated crayfish heart

ABSTRACT

Cardiac muscular contraction of the neurogenic heart that could be excited by pulsed magnetic stimulation (PMS) was investigated using preparation of the isolated crayfish heart. When a figure-eight magnetic coil was set over the isolated heart, cardiac contraction induced by a single PMS was not observed. Cardiac arrest occurred immediately after repetitive PMS and persisted for dozens of seconds depending on the number of stimuli. We concluded that PMS caused neuronal modulation in the neuronal network in the cardiac ganglion.     

Effects of low-amplitude pulsed magnetic fields on cellular ion transport

Pulsed magnetic fields (PMFs) are widely used to treat difficult fractures of bone and other disorders of connective tissue. It is not clear how they interact with tissue metabolism, although it has been proposed that induced currents or electric fields impinging on cell membranes may modify their ion transport function. This hypothesis was tested by treating in vitro models for ion transport processes with short-term exposure to PMFs. No change occurred in active transport of potassium or calcium in human red cells or in calcium transport through an epithelial membrane. We considered less direct action on red cell membranes, that their permeability might be modified after PMF treatment, and also that PMFs might alter the extracellular ionic activity within connective tissue by interacting with its Donnan potential. Each of these studies proved negative, and we conclude that the PMF waveforms used here do not exert a general short-term effect on cellular ion transport.     

Effects of pulsed magnetic fields on the developing mouse embryo

The influence of a pulsed magnetic field (PMF; sawtooth with 45-μs linear rise time and 5-μs decay time, peak strength of 15 μT, and frequency 20 pps) on the embryogenesis of CBA/S mice was investigated in five experiments based on a total of 707 exposed and 543 unexposed primigravidas. Sham and PMF exposures began on day 1 of gestation (experiments 1 and 2), on day 2 (experiment 3), on day 5 (experiment 4). and on day 7 (experiment 5): all exposures continued until day 19 post conception (p.c.) when they were terminated, at which time the following variables were measured: number of implants; number of placental resorptions; number of living fetuses; number of dead fetuses; number of malformations in living and dead fetuses; and length and body mass of living fetuses. Control dams were sham-exposed concurrently with corresponding. PMF-exposed dams. With the exception of experiment 5, in which exposure to PMF started on day 7 p.c., all groups of exposed mice had significantly more placental resorptions when compared with concurrent controls. The increased resorption rate was not reflected in a reduction in litter size or in the number of litters. A significant increase in malformed fetuses was not seen in any of the exposed groups, or when groups were pooled. Only in experiment 1 was the number of dead fetuses affected by exposure to PMF. The effect of PMF on the implantation rate was not significant. Body mass and length of exposed fetuses were significantly reduced only when the PMF treatment began on day 7 p.c. That PMF-treated mice had significantly more placental resorptions when exposure began on day 5 p.c. or earlier (before implantation), but not when exposure began on day 7 (after implantation), may indicate a causative pre-implantation effect. Because a PMF-induced increase in the number of resorptions has not been observed in other strains of mice, the effect might be strain-related. © 1993 Wiley-Liss, Inc.     

Effects of pulsed extremely-low-frequency magnetic fields on skin wounds in the rat

Rats with skin-wounds surgically created on their backs were exposed immediately after surgery and every 12 h thereafter to pulsed, extremely-low-frequency magnetic fields. The shape of the pulse was a positive triangle (50 Hz, 8 mT peak). The rate of healing of skin wounds was evaluated macroscopically and by light and electron microscopy at 6, 12, 21, and 42 days after the operation. A significant increase in the rate of wound contraction was found in rats treated with magnetic fields. Forty-two days after surgery all treated animals show fully closed wounds, while control rats at the same time intervals still lacked a final 6% of the wound surface to be covered. Treated rats showed earlier cellular organization, collagen formation and maturation, and a very early appearance of newly formed vascular network.     

Effects of pulsed magnetic stimulation on tumor development and immune functions in mice

We investigated the effects of pulsed magnetic stimulation on tumor development processes and immune functions in mice. A circular coil (inner diameter = 15 mm, outer diameter = 75 mm) was used in the experiments. Stimulus conditions were pulse width = 238 micros, peak magnetic field = 0.25 T (at the center of the coil), frequency = 25 pulses/s, 1,000 pulses/sample/day and magnetically induced eddy currents in mice = 0.79-1.54 A/m(2). In an animal study, B16-BL6 melanoma model mice were exposed to the pulsed magnetic stimulation for 16 days from the day of injection of cancer cells. A tumor growth study revealed a significant tumor weight decrease in the stimulated group (54% of the sham group). In a cellular study, B16-BL6 cells were also exposed to the magnetic field (1,000 pulses/sample, and eddy currents at the bottom of the dish = 2.36-2.90 A/m(2)); however, the magnetically induced eddy currents had no effect on cell viabilities. Cytokine production in mouse spleens was measured to analyze the immunomodulatory effect after the pulsed magnetic stimulation. tumor necrosis factor (TNF-alpha) production in mouse spleens was significantly activated after the exposure of the stimulus condition described above. These results showed the first evidence of the anti-tumor effect and immunomodulatory effects brought about by the application of repetitive magnetic stimulation and also suggested the possible relationship between anti-tumor effects and the increase of TNF-alpha levels caused by pulsed magnetic stimulation.     

Effects of continuous-wave, pulsed, and sinusoidal-amplitude-modulated microwaves on brain energy metabolism

A comparison of the effects of continuous-wave, sinusoidal-amplitude-modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague-Dawley rats (175-225 g). Brain NADH fluorescence, adenosine triphosphate (ATP) concentration, and creatine phosphate (CP) concentration were determined as a function of modulation frequency. Brain temperatures of animals were maintained between -0.1 and -0.4 degrees C from the preexposure temperature when subjected to as much as 20 mW/cm2 (average power) CW, pulsed, or sinusoidal-amplitude modulated 591-MHz radiation for 5 min. Sinusoidal-amplitude-modulated exposures at 16-24 Hz showed a trend toward preferential modulation frequency response in inducing an increase in brain NADH fluorescence. The pulse-modulated and sinusoidal-amplitude-modulated (16 Hz) microwaves were not significantly different from CW exposures in inducing increased brain NADH fluorescence and decreased ATP and CP concentrations. When the pulse-modulation frequency was decreased from 500 to 250 pulses per second the average incident power density threshold for inducing an increase in brain NADH fluorescence increased by a factor of 4--ie, from about 0.45 to about 1.85 mW/cm2. Since brain temperature did not increase, the microwave-induced increase in brain NADH and decrease in ATP and CP concentrations was not due to hyperthermia. This suggests a direct interaction mechanism and is consistent with the hypothesis of microwave inhibition of mitochondrial electron transport chain function of ATP production.     

Effects of pulsed magnetic fields on neurite outgrowth from chick embryo dorsal root ganglia

We have previously shown that neurite outgrowth from 6-day chick embryo dorsal root ganglia (DRG) in vitro was stimulated when nerve growth factor (NGF) and pulsed magnetic fields (PMF) are used in combination. 392 DRGs were studied in a field excited by a commercial PMF generator. We have now analyzed an additional 416 DRGs exposed to very similar PMF's produced by an arbitrary wave from generator and power amplifier. We reproduced our previous findings that combination of NGF and bursts of asymmetric, 220 μs-wide, 4.0 mT-peak pulses induced significantly (p<0.05) greater outgrowth than NGF alone, that fields without NGF do not significantly alter outgrowth, and that, unlike NGF alone, 4.0 mT fields and NGF can induce asymmetric outgrowth. The asymmetry does not seem to have a preferred orientation with respect to the induced electric field. Analysis of the data for the entire 808 DRGs confirms these findings. Importantly, we find similar results for pulse bursts repeated at 15 or 25 Hz. © 1996 Wiley-Liss, Inc.     

Development of chicken embryos in a pulsed magnetic field

Six independent experiments of common design were performed in laboratories in Canada, Spain, Sweden, and the United States of America. Fertilized eggs of domestic chickens were incubated as controls or in a pulsed magnetic field (PMF); embryos were then examined for developmental anomalies. Identical equipment in each laboratory consisted of two incubators, each containing a Helmholtz coil and electronic devices to develop, control, and monitor the pulsed field and to monitor temperature, relative humidity, and vibrations. A unipolar, pulsed, magnetic field (500-microseconds pulse duration, 100 pulses per s, 1-microT peak density, and 2-microseconds rise and fall time) was applied to experimental eggs during 48 h of incubation. In each laboratory, ten eggs were simultaneously sham exposed in a control incubator (pulse generator not activated) while the PMF was applied to ten eggs in the other incubator. The procedure was repeated ten times in each laboratory, and incubators were alternately used as a control device or as an active source of the PMF. After a 48-h exposure, the eggs were evaluated for fertility. All embryos were then assayed in the blind for development, morphology, and stage of maturity. In five of six laboratories, more exposed embryos exhibited structural anomalies than did controls, although putatively significant differences were observed in only two laboratories (two-tailed Ps of .03 and less than .001), and the significance of the difference in a third laboratory was only marginal (two-tailed P = .08). When the data from all six laboratories are pooled, the difference in incidence of abnormalities in PMF-exposed embryos (approximately 25 percent) and that of controls (approximately 19 percent), although small, is highly significant, as is the interaction between incidence of abnormalities and laboratory site (both Ps less than .001). The factor or factors responsible for the marked variability of inter-laboratory differences are unknown.     

Effects of static magnetic field and pulsed electromagnetic field on viability of human chondrocytes in vitro

Effects of electromagnetic fields (EMFs) on human cell lines were described in numerous studies, but still many questions remain unanswered. Our experiment was designed with the aim of studying the effects of EMFs on the metabolic activity of chondrocytes in vitro. Human chondrocyte in vitro cultures, cultured in medium supplemented with 20 % fetal calf serum, were exposed to static magnetic field (SMF) (intensity of 0.6 T) and pulsed electromagnetic fields (PEMF) (21.2 MHz period of 15 ms, burst duration of 2 ms, amplification 3 dBm (0.1 V) and maximum output of 250 W) continually for 72 h. After the exposure, viability was determined using the MTT test and compared with a non-exposed control culture. As compared to the control sample the exposure to SMF resulted in a statistically significant increase (p 0.001) in viability. However, the increase of viability after PEMF exposure was not significant. This could be due to the frequency dependent effect on human cells. The experiments demonstrated that magnetic fields, using the above parameters, have a positive effect on the viability of human chondrocytes cultured in vitro.     

Effect of a pulsed magnetic field and of first cold-pressure sunflower oil on mice

In previous studies it has been shown that exposure of mice to a 12-Hz 6 mT unipolar square pulsed magnetic field (PMF) suppressed the excess of weight due to application of 1st cold-pressure sunflower oil. This time we considered the effect of oil and/or PMF on the growing curves lifespans of mice. The exposure took place for 30 min 5 days a week, from the 7th week of life to death. The results are 1) a broken slope in the growing curves from the 125th day of aging: the exposed mice were lighter than the controls, keeping the differences between the growing curves needed a repeated exposure all life long; 2) a significant increase in the lifespan of the controls which received oil versus the controls which received water; 3) an increase in the lifespan of the exposed mice versus the non-exposed control batches. On one hand it has been reported that essential polyunsaturated fatty acids found in first cold-pressure sunflower oil played a prominent role in membrane structures and in immune equilibrium. On the other hand, it was shown that oscillating electric fields could activate Na+K+-ATPase.     

Effect of magnetic field on excitation propagation in a nerve fiber innervating a blood vessel]

It was shown that external magnetic field indirectly affects the blood flow due to the increments of local currents in the surroundings of action potentials that propagate along nerve fibres innervating the smooth muscle cells of the vessel wall. This reduces their tension due to nonconcurrent propagation of excitation in space and to changes in the frequency of action potentials. The dependence of this effect on the electrophysiological parameters is estimated.     

Influence of pulsed electromagnetic and pulsed vector magnetic potential field on the growth of tumor cells

Aims and Background: Tumor diseases cause 20% of deaths in Europe and they are the second most common cause of death and morbidity after cardiovascular diseases. Thus, tumor cells are target of many therapeutic strategies and tumor research is focused on searching more efficient and specific drugs as well as new therapeutic approaches. One of the areas of tumor research is an issue of external fields. In our work, we tested influence of a pulsed electromagnetic field (PEMF) and a hypothetic field of the pulsed vector magnetic potential (PVMP) on the growth of tumor cells; and further the possible growth inhibition effect of the PVMP. Methods: Both unipolar and bipolar PEMF fields of 5?mT and PVMP fields of 0?mT at frequencies of 15?Hz, 125?Hz and 625?Hz were tested on cancer cell lines derived from various types of tumors: CEM/C2 (acute lymphoblastic leukemia), SU-DHL-4 (B-cell lymphoma), COLO-320DM (colorectal adenocarcinoma), MDA-BM-468 (breast adenocarcinoma), and ZR-75-1 (ductal carcinoma). Cell morphology was observed, proliferation activity using WST assay was measured and simultaneous proportion of live, early apoptotic and dead cells was detected using flow cytometry. Results: A PEMF of 125?Hz and 625?Hz for 24?h–48?h increased proliferation activity in the 2 types of cancer cell lines used, i.e. COLO-320DM and ZR-75-1. In contrast, any of employed methods did not confirm a significant inhibitory effect of hypothetic PVMP field on tumor cells.     

Distribution of erythrocyte in a model vessel exposed to inhomogeneous magnetic fields

In order to investigate magnetic field effects on blood flow, changes in the flow of erythrocytes in a model branched vessel were observed in an inhomogeneous magnetic field. The magnetic field was applied perpendicular to the straight vessel before branching. When the suspension containing paramagnetic erythrocytes with high spin methemoglobin or deoxygenated hemoglobin flowed in the model vessel, the erythrocytes were attracted towards the stronger magnetic field (i.e. to the side branch) and an excess flow of erythrocytes to the side branch was detected. This excess flow of erythrocytes to the side branch was the highest at a hematocrit of about 5% for the suspension containing erythrocytes with high spin methemoglobin. In the case of mixed suspensions containing erythrocytes with high spin methemoglobin and oxygenated erythrocytes, the excess flow of erythrocytes to the side branch reached its maximum at the "partial hematocrit" for the paramagnetic erythrocyte of around 5% and remained nearly constant with a further increase of the "partial hematocrit." The effect of magnetic field decreased as the flow velocity increased. These results are explained with the paramagnetism of erythrocytes and with the assumption of a hydrodynamic interaction among erythrocytes which are pulled in the direction of the magnetic field. It is suggested that a strong inhomogeneous magnetic field is not totally negligible to the blood circulation.     

低频脉冲磁场对大鼠心肌微血管内皮细胞迁移和NO分泌能力的影响

目的:研究在固定时间和频率下,矩形波形低频脉冲磁场(LF-PMF)对大鼠心肌微血管内皮细胞(CMECs)迁移和NO分泌能力的影响。方法:实验分为4组(对照组,1.0MT组,1.4MT组,1.8MT组)。对照组不加磁场干预,其余各组分别在频率为15Hz,磁场强度分别为1.0MT、1.4MT和1.8MT,时间为4h/d,连续照射3d的条件下,用三角波形作用离体培养的大鼠CMECs。利用transwell检测细胞迁移能力,硝酸还原酶法检测CMECs培养液中NO含量的变化。结果:1.0MT组,1.4MT组和1.8MT组LF-PMF迁移能力与对照组相比均有不同程度提高[(24.40±5.12)(个/视野)vs(22.00±3.87)(个/视野),P<0.05;(31.40±3.81)(个/视野)vs(22.00±3.87)(个/视野),P<0.05;(37.40±4.01)(个/视野)vs(22.00±3.87)(个/视野),P<0.01]。1.0MT组,1.4MT组和1.8MT组LF-PMF的NO分泌能力与对照组相比均有提高[(25.26±1.06)(μmol/L)vs(19.18±2.88)(μmol/L),P<0...     

Resting EEG effects during exposure to a pulsed ELF magnetic field

Continuing evidence suggests that extremely low frequency magnetic fields (ELF MFs) can affect animal and human behavior. We have previously demonstrated that after a 15 min exposure to a pulsed ELF MF, with most power at frequencies between 0 and 500 Hz, human brain electrical activity is affected as measured by electroencephalography (EEG), specifically within the alpha frequency (8-13 Hz). Here, we report that a pulsed ELF MF affects the human EEG during the exposure period. Twenty subjects (10 males; 10 females) received both a magnetic field and a sham session of 15 min in a counterbalanced design. Analysis of variance (ANOVA) revealed that alpha activity was significantly lower over the occipital electrodes (O1, Oz, O2) [F(1,16) = 5.376, P < .01, eta2 = 0.418] after the first 5 min of magnetic field exposure and was found to be related to the order of exposure (MF-sham vs. sham-MF). This decrease in alpha activity was no longer significant in the 1st min post-exposure, compared to sham (P > .05). This study is among the first to assess EEG frequency changes during a weak (+/-200 microTpk), pulsed ELF MF exposure.     

Investigation of pulsed X-ray radiation of a plasma focus in a broad energy range

The results of the experimental investigations of the spectral composition of plasma focus X-ray radiation in the photon energy range of 1.5 keV-400 keV are presented. Three regions in the radiation spectrum where the latter is of a quasi-thermal nature with a corresponding effective temperature are distinguished.     

Pulsed magnetic fields applied to a transferred arterial loop support the rat groin composite flap

Pulsed magnetic fields have been shown to stimulate neovascularization in the authors' laboratory. The rat groin composite flap was used to create a prospective randomized trial to test the effectiveness of these pulsed magnetic fields. The skin paddle to this flap is highly consistent, and the authors proposed using the flap to study how pulsed magnetic fields affect composite flap survival when the dominant vessel to the flap is divided and flap survival becomes dependent on a transferred vessel loop. Forty-three rats had the tail artery microsurgically anastomosed to the femoral artery and placed between the groin musculature and the abdominal skin. Pulsed magnetic energy of 1 gauss was applied for 8 (n = 14) or 12 (n = 8) weeks to the experimental groups. Control groups were treated in a comparable manner for 8 (n = 16) or 12 (n = 5) weeks. After the 8 or 12 weeks, all groups had an 8 x 4-cm skin flap raised, and the superficial epigastric artery, the main feeding vessel, was ligated. After 5 days, the total area of the flap and the area of necrosis were traced onto velum paper for each rat. The percent survival was calculated per rat, and a mean survival percentage was calculated per group. The experimental animals treated with pulsed magnetic fields for 8 weeks had statistically significant improved flap survival over the control animals. The study provides evidence that pulsed magnetic energy stimulates angiogenesis and suggests a possible use of this modality to create island vascular flaps in otherwise random vascular territories.     

Effect of a pulsed magnetic field on tumoral C3H/Bi female mice

Female C3H/Bi mice develop spontaneous viral mammary carcinoma which can metastasize to the lungs. Two hundred and forty tumoral mice were either exposed to a toro?dal pulsed magnetic field, 12 Hz, 100 Hz or 460 Hz in frequency or used as controls. The exposure was mainly done 10 min. a day, 3 days a week, or 30 minutes once a week from about 2 to 3 weeks after the appearance of the tumors until death. In comparison with the controls, the exposed mice showed lighter spleens and lungs; this last observation could mean fewer pulmonary metastases. The weight of the tumors has been found lighter for 460 Hz MF, not changed for 100 Hz MF, heavier for 12 Hz MF, but lifespans were not altered by the exposure.