Exposure to time varying magnetic fields associated with magnetic resonance imaging reduces fentanyl-induced analgesia in mice

The effects of exposure to clinical magnetic resonance imaging (MRI) on analgesia induced by the mu opiate agonist, fentanyl, was examined in mice. During the dark period, adult male mice were exposed for 23.2 min to the time-varying (0.6 T/sec) magnetic field (TVMF) component of the MRI procedure. Following this exposure, the analgesic potency of fentanyl citrate (0.1 mg/kg) was determined at 5, 10, 15, and 30 min post-injection, using a thermal test stimulus (hot-plate 50 degrees C). Exposure to the magnetic-field gradients attenuated the fentanyl-induced analgesia in a manner comparable to that previously observed with morphine. These results indicate that the time-varying magnetic fields associated with MRI have significant inhibitory effects on the analgesic effects of specific mu-opiate-directed ligands.     

Effects of 180 mT static magnetic fields on diabetic wound healing in rats

Diabetic wound (DW) problems are becoming a formidable clinical challenge due to the sharp increase in the diabetic population and the high incidence of DW. Static magnetic field (SMF) therapy, an inexpensive and accessible noninvasive method, has been proven to be effective on various tissue repairs. However, the issue of the therapeutic effect of SMF on DW healing has never been investigated. The objective of this study was to systematically evaluate the effect of a 180 mT moderate‐intensity gradient SMF on DW healing in streptozotocin‐induced diabetic rats. Forty‐eight 3‐month‐old male Sprague–Dawley rats (32 diabetic and 16 non‐diabetic rats) were assigned to three equal groups: normal wound, DW, and DW + SMF groups. An open circular wound with 1.5 cm diameter was created in the dorsum. The wound was covered with a dressing and the magnet was fixed on top of the dressing. On days 5, 12, and 19, four rats of each group were euthanized and gross wound area, histology and tensile strength were evaluated. The wound area determination suggested that SMF significantly increased the healing rate and reduced the gross healing time. This result was further confirmed by histological observations. The wound tensile strength, reflecting the amount and quality of collagen deposition, increased to a larger extent in the DW + SMF group on days 12 and 19 compared with the DW group. The results indicated that 180 mT SMF presented a beneficial effect on DW healing, and implied the clinical potential of SMF therapy in accelerating DW repair and releasing the psychological and physical burdens of diabetic patients. Bioelectromagnetics 31:640–648, 2010. © 2010 Wiley‐Liss, Inc.     

50 Hz magnetic fields of 1 mT do not promote lymphoma development in AKR/J mice

Some epidemiological studies suggest that exposure to power-frequency magnetic fields increases the risk of leukemia, especially in children with high residential exposures. In contrast, most animal studies did not find a correlation between magnetic-field exposure and hematopoietic diseases. The present study was performed to investigate whether chronic, high-level (1 mT) magnetic-field exposure had an influence on lymphoma development in a mouse strain that is genetically predisposed to thymic lymphoblastic lymphoma. Three groups of 160 unrestrained female AKR/J mice were sham-exposed or exposed to sinusoidal 50 Hz magnetic fields beginning at the age of 12 weeks for 32 weeks, 7 days per week, either for 24 h per day or only during nighttime (12 h). Exposure was carried out in a blind design. Exposure did not affect survival time, body weight, lymphoma development or hematological parameters. The resulting data do not support the hypothesis that exposure to sinusoidal 50 Hz magnetic fields is a significant risk factor for hematopoietic diseases, even at this relatively high exposure level.     

Effects of static magnetic fields on growth of Paramecium caudatum

Little is known about the influence of magnetic fields on growth of primitive eukaryotes such as the ciliate Paramecium. The latter are known to exhibit interesting characteristics such as electrotaxis, gravitaxis, and membrane excitability not commonly encountered in higher organisms. This preliminary study reports the effects of static magnetic fields on growth of Paramecium caudatum. The microorganisms were either permanently or 24 h on-and-off exposed to North and South polarity magnetic fields of average field gradient 4.3 T/m, for a period of 96 h. The growth rate and lag phase of all exposed populations were not significantly different from control ones exposed to normal geomagnetic field (P > .05). However, a significant negative shift in t(max) (time taken for maximum growth) of 10.5%-12.2% and a significant decrease (P < .05) in population size of 10.2%-15.1% during the 96 h of experimental conditions were recorded for exposed populations compared to control. Our results suggest that magnetic fields, irrespective of polarity and exposure period reduce Paramecium growth by triggering early senescence of the population. The mechanisms underlying the small changes in population growth are unknown at this level, but various hypotheses have been suggested, including disorganization of swimming patterns resulting from (i) changes in cell membrane electric potential due to high speed movement through a gradient magnetic field and (ii) thermodynamic effect of anisotropic magnetic energies on cell membrane components affecting functioning of calcium channels. Altered swimming movements could in turn affect highly orchestrated processes such as conjugation, essential for survival of the organisms during development of adverse environmental conditions as thought to occur in the closed culture system used in this study.     

Effects of 100-Hz magnetic fields with various waveforms on the development of chick embryos

Summary Chick embroys were exposed during their 52 first hours of development to 100-Hz magnetic fields. Sinusoidal, square and pulsed waveforms were used at average field strengths from 0.1 A/m to 80 A/m. After exposure, the embryos were examined for abnormalities and classified by the developmental stages. When bipolar oscillations (oscillating at both sides of the zero-level) were used, the percentage of abnormal embryos was significantly increased above 1 A/m. In exposure to unipolar square waves, no significant effect on the percentage of abnormalities could be demonstrated. The developmental stage was possibly affected by unipolar square waves at 0.1 A/m, all other field strengths and wave-forms being apparently ineffective.     

Effects of low-frequency magnetic fields on fetal development in CBA/Ca mice

Effects of alternating magnetic fields (MFs) on the embryonic and fetal development in CBA/Ca mice were studied. Mated females were exposed continuously to a sinusoidal 50 Hz (13 μT or 0.13 mT root mean square) or a sawtooth 20 kHz (15 μT peak-to-peak) MF from day 0 to day 18 of pregnancy for 24 h/day until necropsied on day 18. Control animals were kept under the same conditions without the MF. MFs did not cause maternal toxicity. No adverse effects were seen in maternal hematology and the frequency of micronuclei in maternal bone marrow erythrocytes did not change. The MFs did not increase the number of resorptions or fetuses with major or minor malformations in any exposure group. The mean number of implantations and living fetuses per litter were similar in all groups. The corrected weight gain (weight gain without uterine content) of dams, pregnancy rates, incidences of resorptions and late fetal deaths, and fetal body weights were similar in all groups. There was, however, a statistically significant increase in the incidence of fetuses with at least three skeletal variations in all groups exposed to MFs. In conclusion, the 50 Hz or 20 kHz MFs did not increase incidences of malformations or resorptions in CBA/Ca mice, but increased skeletal variations consistently in all exposure groups. Bioelectromagnetics 19:477–485, 1998. © 1998 Wiley-Liss, Inc.     

Effects of static magnetic fields on bone microstructure and mechanical properties in mice

All the living organisms originate, evolve and live under geomagnetic field (GMF, 20–70 µT). With rapid development in science and technology, exposure to various static magnetic fields (SMFs) from natural and man-made sources remains a public environmental topic in consideration of its probable health risk for humans. Many animal studies related to health effect have demonstrated that SMF could improve bone formation and enhance bone healing. Moreover, most of the studies focused on local SMF generated by rod-type magnet. It was difficult to come to a conclusion that how SMF affected bone metabolism in mice. The present study employed hypomagnetic field (HyMF, 500 nT), and moderate SMF (MMF, 0.2 T) to systematically investigate the effects of SMF with continuous exposure on microstructure and mechanical properties of bone. Our results clearly indicated that 4-week MMF exposure did not affect bone biomechanical properties or bone microarchitecture, while HyMF significantly inhibited the growth of mice and elasticity of bone. Furthermore, mineral elements might mediate the biological effect of SMF.     

Effects of static magnetic fields on the growth of various types of human cells

The effects of a static magnetic field (SMF) on the proliferation of various types of human cells were determined. All cultures were maintained at 37 °C throughout the experiment. SMF was generated by placing two magnets oppositely oriented on either side of a T25 flask. The flux density in the flask ranged from 35 to 120 mT. Growth curves were constructed by plotting cell number at 18 h and 4, 7, 11, and 14 days after seeding, with the 18‐h point being a measure of attachment efficiency. Exposure to SMF significantly decreased initial attachment of fibroblasts and decreased subsequent growth compared to sham‐exposed control. Significant effects were observed in both fetal lung (WI‐38) and adult skin fibroblasts, but they were generally larger in the fetal lung fibroblast line. SMF did not affect attachment of human melanoma cells, but inhibited their growth by 20% on day 7. SMF produced no effects in a human adult stem cell line. Oxidant production increased 37% in WI‐38 cells exposed to SMF (230–250 mT) during the first 18 h after seeding, when cell attachment occurs. Conversely, no elevation in oxidant levels was observed after a prolonged 5‐day exposure. These results indicate that exposure to SMF has significant biological effects in some, but not all types of human cells. Bioelectromagnetics 32:140–147, 2011. © 2010 Wiley‐Liss, Inc.     

Effects of 12 mT static magnetic field on sympathetic agonist-induced hypertension in Wistar rats

We investigated the combined effects of a moderate-intensity static magnetic field (SMF) and two different sympathetic agonists, an alpha(1)-adrenoceptor agonist, phenylephrine and a beta(1)-adrenoceptor agonist, dobutamine, which induced hypertension and different hemodynamics in Wistar rats. Five-week-old male rats were continuously exposed to the SMF intensity of 12 mT (B(max)) with the peak spatial gradient of 3 mT/mm for 10 weeks. A loop-shaped flexible rubber magnet was adjusted to fit snugly around the neck region of a rat (diameter-adjustable to an animal size). Sham exposure was performed using a dummy magnet. Six experimental groups of six animals each were examined: (1) sham exposure with intraperitoneal (ip) saline injection (control); (2) SMF exposure with ip saline injection (SMF); (3) sham exposure with ip phenylephrine (1.0 microg/g) injection (PE); (4) SMF exposure with ip phenylephrine injection (SMF + PE); (5) sham exposure with ip dobutamine (4.0 microg/g) injection (DOB); (6) SMF exposure with ip dobutamine injection (SMF + DOB). Fifteen minutes after the injection of each agent, the first set of parameters, arterial blood pressure (BP) and heart rate (HR), the second set of parameters, skin blood flow (SBF) and skin blood velocity (SBV), or the third set of parameters, the number of rearing (exploratory behavior) responses and body weight was monitored. Each agent was administered three times a week for 10 weeks, and each set of parameters was monitored on different days, once a week. The dose of phenylephrine significantly increased BP and decreased HR, SBF, SBV, and the number of rearing responses in the PE group compared with those in the respective age-matched control group. The dose of dobutamine significantly increased BP and HR, increased SBF, SBV, and the number of rearing responses in the DOB group compared with those in the control group. Continuous neck exposure to the SMF alone for up to 10 weeks induced no significant changes in any of the measured cardiovascular and behavioral parameters. The SMF exposure for at least 2 weeks (1) significantly depressed phenylephrine effects on BP, SBF, SBV, and rearing activity (SMF + PE group vs. PE group); (2) significantly depressed dobutamine effects on BP, SBF, and SBV, and suppressed dobutamine-induced increase in the rearing activity (SMF + DOB group vs. DOB group). These results suggest that continuous neck exposure to 12 mT SMF for at least 2 weeks may depress or suppress sympathetic agonists-induced hypertension, hemodynamics, and behavioral changes by modulating sympathetic nerve activity.     

Effects of permanent magnetic fields on in vitro growth of Cymbidium and Spathiphyllum shoots

Magnetic fields affect biological systems. However, this is the first study on the effects of permanent magnetic fields (MFs) on the micropropagation of two ornamental plants, Spathiphyllum cv. i.e ‘Merry’ and Cymbidium Music Hour ‘Maria’. Cymbidium and Spathiphyllum shoots cultured in the ‘Miracle Pack’? culture system were exposed to MFs of different intensities, polarities, and duration of exposure. The results show that by increasing intensity from 5 × 10⁻⁶ Tesla (T) as the geo-magnetic field to 0.1, 0.15, and 0.2 T negatively influenced height and fresh mass of roots of Cymbidium plants (except for 0.1 T–S and 0.2 T–N treatments), but had no significant effect on other plantlet parameters. Long-term exposure (1, 2, or 3 mo) of Cymbidium shoots to 0.15 T–MFs negatively influenced plant height, positively affected the number of leaves (with the exception of 0.15 T–S—1 mo), and had no clear effect on other parameters compared to the control. MFs (0.1, 0.15, and 0.2 T), regardless of their polarity, increased chlorophyll content (SPAD value) and the number of leaves, but slightly decreased the dry mass of Spathiphyllum shoots. Different exposure duration to 0.15 T (i.e., 2, 4, or 8 wk) had no significant influence on Spathiphyllum plantlet development other than increasing the SPAD value. These two ornamentals could serve as model systems to study plant development, space production, yield maximization, and the development of new morphotypes essential for the floricultural market.     

Effects of weak magnetic fields on the production of reactive oxygen species in peritoneal neutrophils in mice

The influence of weak magnetic fields of different types on the rate of the formation of reactive oxygen species in mouse peritoneal neutrophils has been studied. It was found that the exposure of neutrophils activated by phorbol 12-myristate 13-acetate to the magnetic field tuned to the parametric resonance for Ca2+ ions leads to a decrease in the rate of the reactive oxygen species (ROS) generation by 23%. Conversely, the generation of ROS in neutrophils exposed to the same field but stimulated by the bacterial peptide FMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine) increased by about 21%. Pulsed magnetic fields also changed the rate of ROS generation in phorbol-stimulated neutrophils by about 20%, but the sign of the effects observed in this case was opposite to those induced by the magnetic field tuned to the parametric resonance for Ca2+ ions.     

Biological effects of 6 mT static magnetic fields: a comparative study in different cell types

The present work was a comparative study of the bio-effects induced by exposure to 6 mT static magnetic field (MF) on several primary cultures and cell lines. Particular attention was dedicated to apoptosis. Cell viability, proliferation, intracellular Ca(2+) concentration and morphology were also examined. Primary cultures of human lymphocytes, mice thymocytes and cultures of 3DO, U937, HeLa, HepG2 and FRTL-5 cells were grown in the presence of 6 mT static MF and different apoptosis-inducing agents (cycloheximide, H(2)O(2), puromycin, heat shock, etoposide). Biological effects of static MF exposure were found in all the different cells examined. They were cell type-dependent but apoptotic inducer-independent. A common effect of the exposure to static MF was the promotion of apoptosis and mitosis, but not of necrosis or modifications of the cell shape. Increase of the intracellular levels of Ca(2+) ions were also observed. When pro-apoptotic drugs were combined with static MF, the majority of cell types rescued from apoptosis. To the contrary, apoptosis of 3DO cells was significantly increased under simultaneous exposure to static MF and incubation with pro-apoptotic drugs. From these data we conclude that 6 mT static MF exposure interfered with apoptosis in a cell type- and exposure time-dependent manner, while the effects of static MF exposure on the apoptotic program were independent of the drugs used.     

Effects of 25 mT static magnetic field on blood pressure in reserpine-induced hypotensive Wistar-Kyoto rats

We investigated the interrelated antihypotensive effects of static magnetic fields (SMF) and plasma catecholamine levels in reserpine-induced hypotensive Wistar-Kyoto rats. Seven-week-old male rats were exposed to two different ranges of SMF intensities, 3.0-10 mT (Bmax) or 7.5-25 mT (Bmax) for 12 weeks. Six experimental groups of 10 animals each were examined: (1) no exposure with intraperitoneal (ip) saline injection (sham exposed control); (2) 10 mT SMF exposure with ip saline injection (10 mT); (3) 25 mT SMF exposure with ip saline injection (25 mT); (4) no exposure with ip reserpine injection (RES); (5) 10 mT SMF exposure with ip reserpine injection (10 mT + RES); (6) 25 mT SMF exposure with ip reserpine injection (25 mT + RES). Reserpine (5 mg/kg) was administered three times a week for 12 weeks, and 18 h after each injection, arterial blood pressure (BP), heart rate, skin blood flow, plasma nitric oxide metabolites, plasma catecholamine levels, and behavioral parameters of a functional observational battery (FOB) were monitored. The action of reserpine significantly decreased BP, reduced plasma norepinephrine (NE), increased the FOB hunched posture score and decreased the number of rearing events in the RES group, compared with the respective age-matched control group. Exposure to 25 mT, but not 10 mT, for 2-12 weeks significantly prevented the reserpine-induced decrease of BP in the 25 mT + RES group compared with the respective RES group. Moreover, exposure to 25 mT for 5 weeks partially suppressed the reserpine-induced NE reduction, but did not bring about a complete reversal of reserpine effects. NE levels for the 25 mT + RES group for 5 weeks were significantly higher compared with the RES group, but still lower compared with the control group. In addition, the FOB hunched posture score for the 25 mT + RES group was significantly lower and the number of rearing events was higher compared with the RES group, but these behavioral parameters did not revert to control levels. There were no significant differences in any of the physiological or behavioral parameters measured between the 10 mT + RES and RES groups, nor between the two different SMF groups and the control group. These results indicate that 25 mT SMF with spatial gradients significantly suppressed the reserpine-induced hypotension and bradykinesia. The antihypotensive effects of SMF on the reserpine-treated group might be at least partially related to the inhibition of NE depletion.     

Effect of 50 Hz, 0.2 mT magnetic fields on RBC properties and heart functions of albino rats

In this work the effect of sinusoidal 50 Hz, 0.2 mT magnetic fields on the red blood cells (RBCs) and heart functions of Albino rats were investigated. Twenty-four male Albino rats were equally divided into four groups, A, B, C, and D. Animals from groups B were continuously exposed to the magnetic field for 15 days; and groups C and D, for 30 days. Group A was used as control. Animals from group D were kept after exposure to the magnetic field for a period of 45 days for delayed effect studies. The osmotic fragility and shape of RBCs' membrane and hemoglobin (Hb) structure tests were carried out for all groups. The dielectric relaxation of Hb molecules was measured in the frequency range of 0.1-10 MHz and the dielectric increment (Deltaepsilon), relaxation time (tau), molecular radius (r), and Cole-Cole parameter (alpha) were calculated for all groups. The ECG was measured for all animals before and after exposure to the magnetic field. The results indicated that exposure of the animals to 50 Hz, 0.2 mT magnetic fields resulted in the decrease of RBCs membrane elasticity and permeability and changes in the molecular structure of Hb. The ECG of the exposed animals was considerably altered. The data also indicated that there was no sign of repair in the newly generated RBCs structure and the ECG after removing the animals from the magnetic field, which indicates that the blood generating system was severely injured. The injuries in the heart of the animals were attributed to the loss of some physiological functions of the RBCs as a result of exposures of the rats to the magnetic field.     

Effects of 120 mT static magnetic field on TGF-beta1-inhibited endothelial tubular formation in vitro

We designed this study to examine the effects of static magnetic fields (SMF; 120 mT [B(max)] and a maximum spatial magnetic flux gradient of 21 mT/mm) on inhibited tubular formation when treated with human transforming growth factor (TGF)-beta1 at a relatively high concentration (5 ng/ml). Three experimental groups of 25 samples each were examined: (1) sham exposure alone (control); (2) sham-exposure with TGF-beta1; (3) SMF exposure with TGF-beta1. The SMF or sham exposure was carried out for 10 days. Photomicrographs of tubular cells, immunostained with an anti-platelet-endothelial cell adhesion molecule-1 (PECAM-1 [CD31]) antibody as a pan-endothelial marker, were analyzed after the 10-day culture. SMF was found to significantly reverse the inhibition of TGF-beta1 on tubular formation in terms of the area density and length of tubules (arteriogenesis) in the peripheral part of the wells, compared with the TGF-beta1 treatment alone. These findings suggest that one of the possible exogenous factors for arteriogenesis might involve 'magnetic force' (the product of the magnetic flux density, the magnetic gradient, and the volume susceptibility of the cells) because values are much larger in the peripheral part than in the central part.     

Transmission of time varying magnetic field through body tissue

Based on the principles of interaction of electromagnetic waves with semi-infinite media, a simplified model is developed for the study of biological tissue — EM wave interaction problems. The four common types of biological tissues viz, bone, blood, alveolar and muscle tissue, each in turn has been considered. Expression for the transmission loss of the incident EM waves have been derived and numerically evaluated. The results indicate that there is a frequency dependence of the transmission loss and variations with tissue type exist and that losses become significant above 30 MHz. Attenuation for muscular tissue is maximum at frequencies of about 200 MHz whereas the corresponding frequency for lung tissue is nearly the double. Suitable experiments have been designed and performed to verify the salient results of the model and a fair degree of agreement has been found between the experimental results and theoretical predictions. Possibilities for the improvement of the model and future applications of the model have been outlined.     

Micronuclei in the blood and bone marrow cells of mice exposed to specific complex time‐varying pulsed magnetic fields

For 8 weeks, adult CD‐1 male mice were continuously exposed to complex time‐varying pulsed magnetic fields (PMF) generated in the horizontal direction by a set of square Helmholtz coils. The PMF were <1000 Hz and delivered at a peak flux density of 1 mT. Sham‐exposed mice were kept in a similar exposure system without a PMF. Positive control animals exposed to 1 Gy gamma radiation were also included in the study. Blood samples were collected before (time 0) and at 2, 4, 6, and 8 weeks. All mice were euthanized at the end of 8 weeks and their bone marrow was collected. From each blood and bone marrow sample, smears were prepared on microscope slides, fixed in absolute methanol, air‐dried, and stained with acridine orange. All slides were coded and examined using a fluorescence microscope. The extent of genotoxicity and cytotoxicity was assessed from the incidence of micronuclei (MN) and percent polychromatic erythrocytes (PCE) in the blood and bone marrow, respectively. The data indicated that both indices in PMF‐exposed mice were not significantly different from those observed in sham‐exposed animals. In contrast, positive control mice exhibited significantly increased MN, and decreased percentages of PCE in both tissues. Thus, the overall data suggested that 8 weeks of continuous exposure to PMF did not induce significantly increased genotoxicity and cytotoxicity in experimental mice. Further investigations are underway using other genotoxicity assays (comet assay, γ‐H2AX foci, and chromosomal aberrations) to assess genotoxicity following PMF exposure. Bioelectromagnetics 31:445–453, 2010. © 2010 Wiley‐Liss, Inc.     

Effects of time-varying uniform magnetic fields on Natural Killer cell activity and antibody response in mice

Natural Killer cell activity and antibody response were studied in Balb/c mice which were exposed in vivo to uniform pulsed magnetic fields (square-wave, 0.8 Hz, 120 mT maximum field strength, 0.1 s rise-time) for 5 days, 10 h/day. No effects were found in antibody response to sheep red blood cell (SRBC) immunization as assayed by counting the plaque-forming cells (PFC) in the spleens of animals on the sixth day. Following 5-day exposures, the activity of Natural Killer (NK) cells was measured in vitro by challenge with YAC-1 cells, in experiments in which mice were not immunized. An increase of NK cytotoxic activity due to exposure was found which depended on the age of the mice (effect observed above 12 weeks) and on the strength of the applied field (effect observed above 30 mT). © 1993 Wiley-Liss. Inc.     

Effects of static magnetic fields on diffusion in solutions

Static magnetic fields affect the diffusion of biological particles in solutions through the Lorentz force and Maxwell stress. These effects were analyzed theoretically to estimate the threshold field strength for these effects. Our results show that the Lorentz force suppresses the diffusion of charged particles such as Na+, K+, Ca2+, Cl-, and plasma proteins. However, the threshold is so high, i.e., more than 10(4) T, that the Lorentz force does not affect the ion diffusion at typical field strengths (a few Tesla at most). Since the threshold of gradient fields for producing a change in ion diffusion through the Maxwell stress is more than 10(5) T2/m for paramagnetic molecules (FeCl3, O2) and plasma proteins, their diffusion would be unaffected by typical gradient fields (100 T2/m at most) and even by high gradient fields (less than 10(5) T2/m) used in magnetic separation techniques. In contrast, movement of deoxygenated erythrocytes and FeCl3 colloids (more than 10(3) molecules) is influenced by the usual gradient fields due to a volume effect.