This study sought to clarify the effects of exposure to electromagnetic waves (EMW) used in cellular phones on learning and memory processes. Sprague-Dawley rats were exposed for either 1 h daily for 4 days or for 4 weeks to a pulsed 1439 MHz time division multiple access (TDMA) field in a carousel type exposure system. At the brain, average specific absorption rate (SAR) was 7.5 W/kg, and the whole body average SAR was 1.7 W/kg. Other subjects were exposed at the brain average SAR of 25 W/kg and the whole body average SAR of 5.7 W/kg for 45 min daily for 4 days. Learning and memory were evaluated by reversal learning in a food rewarded T-maze, in which rats learned the location of food (right or left) by using environmental cues. The animals exposed to EMW with the brain average SAR of 25 W/kg for 4 days showed statistically significant decreases in the transition in number of correct choices in the reversal task, compared to sham exposed or cage control animals. However, rats exposed to the brain average SAR of 7.5 W/kg for either 4 days or for 4 weeks showed no T-maze performance impairments. Intraperitoneal temperatures, as measured by a fiber optic thermometer, increased in the rats exposed to the brain average SAR of 25 W/kg but remained the same for the brain average SAR of 7.5 W/kg. The SAR of a standard cellular phone is restricted to a maximum of 2 W/kg averaged over 10 g tissue. These results suggest that the exposure to a TDMA field at levels about four times stronger than emitted by cellular phones does not affect the learning and memory processes when there are no thermal effects.
Isolated pineal glands of Djungarian hamsters (Phodopus sungorus) were continuously perifused by Krebs-Ringer buffer, stimulated with the beta-adrenergic receptor agonist isoproterenol to induce melatonin synthesis, and exposed for 7 hr to a 1800 MHz continuous wave (CW) or pulsed GSM (Global System for Mobile Communications)-modulated electromagnetic signal at specific absorption rate (SAR) rates of 8, 80, 800, and 2700 mW/kg. Experiments were performed in a blind fashion. Perifusate samples were collected every hour, and melatonin concentrations were measured by a specific radioimmunoassay. Both types of signal significantly enhanced melatonin release at 800 mW/kg SAR, while at 2700 mW/kg SAR, melatonin levels were elevated in the CW, but suppressed in the GSM-exposed pineal glands. As a temperature rise of approximately 1.2 degrees C was measured at 2700 mW/kg SAR, effects at this level are thermal. With regard to radiofrequency electromagnetic fields, the data do not support the 'melatonin hypothesis,' according to which nonthermal exposure suppresses melatonin synthesis.
The biological effect of radiofrequency (RF) fields remains controversial. We address this issue by examining whether RF fields can cause changes in gene expression. We used the pulsed RF fields at a frequency of 2.45 GHz that is commonly used in telecommunication to expose cultured human HL-60 cells. We used the serial analysis of gene expression (SAGE) method to measure the RF effect on gene expression at the genome level. We observed that 221 genes altered their expression after a 2-h exposure. The number of affected genes increased to 759 after a 6-h exposure. Functional classification of the affected genes reveals that apoptosis-related genes were among the upregulated ones and the cell cycle genes among the downregulated ones. We observed no significant increase in the expression of heat shock genes. These results indicate that the RF fields at 2.45 GHz can alter gene expression in cultured human cells through non-thermal mechanism.
An open tomograph to image volume regions near the surface of large objects is described. The central achievement in getting such a tomograph to work is the design of a fast two-dimensional pure phase encoding imaging method to produce a cross-sectional image in the presence of highly inhomogeneous fields. The method takes advantage of the multi-echo acquisition in a Carr-Purcell-Meiboom-Gill (CPMG)-like sequence to significantly reduce the experimental time to obtain a 2D image or to spatially resolve relaxation times across the sensitive volume in a single imaging experiment. Depending on T(2) the imaging time can be reduced by a factor of up to two orders of magnitude compared to the one needed by the single-echo imaging technique. The complete echo train decay has been also used to produce T(2) contrast in the images and to spatially resolve the T(2) distribution of an inhomogeneous object, showing that variations of structural properties like the cross-link density of rubber samples can be distinguished by this method. The sequence has been implemented on a single-sided sensor equipped with an optimized magnet geometry and a suitable gradient coil system that provides two perpendicular pulsed gradient fields. The static magnetic field defines flat planes of constant frequency parallel to the surface of the scanner that can be selected by retuning the probe frequency to achieve slice selection into the object. Combining the slice selection obtained under the presence of the static gradient of the open magnet with the two perpendicular pulsed gradient fields, 3D spatial resolution is obtained.
Electromagnetic fields are an assessed cause of prolonging free radicals lifespan. This study was carried out to investigate the influence of extremely low frequency electromagnetic fields on protein oxidation and on the 20S proteasome functionality, the complex responsible for the degradation of oxidized proteins. Caco 2 cells were exposed, for 24-72 hours, to 1 mT, 50 Hz electromagnetic fields. The treatment induced a time-dependent increase both in cell growth and in protein oxidation, more evident in the presence of TPA, while no changes in cell viability were detected. Exposing the cells to 50 Hz electromagnetic fields caused a global activation of the 20S proteasome catalytic components, particularly evident at 72 hours exposure and in the presence of TPA. The finding that EGCG, a natural antioxidant compound, counteracted the field-related pro-oxidant effects demonstrates that the increased proteasome activity was due to an enhancement in intracellular free radicals.
We used exposure to microwaves from a global system for mobile communication (GSM) mobile phone (915 MHz, specific absorption rate (SAR) 37 mW/kg) and power frequency magnetic field (50 Hz, 15 muT peak value) to investigate the response of lymphocytes from healthy subjects and from persons reporting hypersensitivity to electromagnetic field (EMF). The hypersensitive and healthy donors were matched by gender and age and the data were analyzed blind to treatment condition. The changes in chromatin conformation were measured with the method of anomalous viscosity time dependencies (AVTD). 53BP1 protein, which has been shown to colocalize in foci with DNA double strand breaks (DSBs), was analyzed by immunostaining in situ. Exposure at room temperature to either 915 MHz or 50 Hz resulted in significant condensation of chromatin, shown as AVTD changes, which was similar to the effect of heat shock at 41 degrees C. No significant differences in responses between normal and hypersensitive subjects were detected. Neither 915 MHz nor 50 Hz exposure induced 53BP1 foci. On the contrary, a distinct decrease in background level of 53BP1 signaling was observed upon these exposures as well as after heat shock treatments. This decrease correlated with the AVTD data and may indicate decrease in accessibility of 53BP1 to antibodies because of stress-induced chromatin condensation. Apoptosis was determined by morphological changes and by apoptotic fragmentation of DNA as analyzed by pulsed-field gel electrophoresis (PFGE). No apoptosis was induced by exposure to 50 Hz and 915 MHz microwaves. In conclusion, 50 Hz magnetic field and 915 MHz microwaves under specified conditions of exposure induced comparable responses in lymphocytes from healthy and hypersensitive donors that were similar but not identical to stress response induced by heat shock.
An array of highly sensitive biomagnetic sensors of the superconducting quantum interference detector (SQUID) type can identify disease in vivo by detecting and imaging microscopic amounts of nanoparticles. We describe in detail procedures and parameters necessary for implementation of in vivo detection through the use of antibody-labelled magnetic nanoparticles as well as methods of determining magnetic nanoparticle properties. We discuss the weak field magnetic sensor SQUID system, the method of generating the magnetic polarization pulse to align the magnetic moments of the nanoparticles, and the measurement techniques to measure their magnetic remanence fields following this pulsed field. We compare these results to theoretical calculations and predict optimal properties of nanoparticles for in vivo detection.
Based on the electromagnetic model of the transmission line for the channel and the birdcage resonator for the meridian network, we interpret two effects, seemingly incomprehensible in terms of current Western physiology, the lasting effect and the remote effect. For the lasting effect, acupuncture enhances the amplitude of the Qi standing wave, and this increased amplitude is retained and thus is able to sustain a gradual remodeling of the extracellular matrix in interstitial connective tissues, resulting in a lasting therapeutic effect. For the remote effect (acupuncture effect far from the site of needle insertion), our model puts the mechanism of magnetic therapy on an equal footing with that of acupuncture. It may not be a coincidence that accounts of investigators in both acupuncture and magnetotherapy about the depth of the effective site--along cleavage planes between muscles, or between muscle and bone or tendon--are in accord with that of the Huang Di Nei Jing about the course of channels: "they are embedded and travel between interstitial muscles, deep and invisible." A possible magnetic field generated outside the birdcage may be manipulated to produce local areas of higher temperature or very strong fields.
An alternative coil system to the Helmoholtz coil-pair is described for the stimulation of biological tissue and cells: a relatively large box coil made of copper or aluminum sheet stock. The design is based on the principal determinant of the induced electric field, namely, the magnetic vector potential (A), in the equation, [formula: see text]. The second term in the equation is needed when boundaries of the conducting medium are in close proximity to the region of interest, such as in a culture dish. An electric surface charge builds up on the boundaries to generate an electric field which cancels [formula: see text] at the surface. The effectiveness of the new coil is demonstrated in a study of the outgrowth enhancement of axons from rat embryonic dorsal root ganglia.
OBJECTIVES--This case cohort study examines whether there is an association between exposure to electric and magnetic fields and suicide in a population of 21,744 male electrical utility workers from the Canadian Province of Quebec. METHODS--49 deaths from suicide were identified between 1970 and 1988 and a subcohort was selected comprising a 1% random sample from this cohort as a basis for risk estimation. Cumulative and current exposures to electric fields, magnetic fields, and pulsed electromagnetic fields (as recorded by the POSITRON meter) were estimated for the subcohort and cases through a job exposure matrix. Two versions of each of these six indices were calculated, one based on the arithmetic mean (AM), and one on the geometric mean (GM) of field strengths. RESULTS--For cumulative exposure, rate ratios (RR) for all three fields showed mostly small non-significant increases in the medium and high exposure groups. The most increased risk was found in the medium exposure group for the GM of the electric field (RR = 2.76, 95% CI 1.15-6.62). The results did not differ after adjustment for socioeconomic state, alcohol use, marital state, and mental disorders. There was a little evidence for an association of risk with exposure immediately before the suicide. CONCLUSION--Some evidence for an association between suicide and cumulative exposure to the GM of the electric fields was found. This specific index was not initially identified as the most relevant index, but rather emerged afterwards as showing the most positive association with suicide among the 10 indices studied. Thus the evidence from this study for a causal association between exposure to electric fields and suicide is weak. Small sample size (deaths from suicide) and inability to control for all potential confounding factors were the main limitations of this study.
Congenital pseudarthrosis of the tibia presents surgeons with one of the most challenging of all orthopedic problems. Various surgical treatments have succeeded only rarely. We report long-term follow-up of a patient with congenital pseudarthrosis of the tibia treated with pulsed electromagnetic fields (PEMF) and bone grafting. In this severe case, Bassett type III and Boyd type II, encouraging results were achieved with Boyd's dual onlay grafts and PEMF. Seven years after surgery, skeletal maturity was complete and an unacceptable degree of leg shortening had been avoided.
STUDY DESIGN: Systematic review. OBJECTIVE: To assess whether electrotherapy relieves pain or improves function/disability in adults with mechanical neck disorders (MND). SUMMARY OF BACKGROUND DATA: The effectiveness of electrotherapy as a physiotherapy option has remained unclear. METHODS: Databases were searched from root to March 2003. Independent reviewers conducted selection, data abstraction, and quality assessment. Relative risk and standard mean differences were calculated. RESULTS: Fourteen comparisons were included. For the pain outcome, we found limited evidence of benefit, ie, pulsed electromagnetic field (PEMF) therapy resulted in only immediate post-treatment pain relief for chronic MND and acute whiplash (WAD). Other findings included unclear or conflicting evidence (Galvanic current for acute or chronic occipital headache; iontophoresis for acute, subacute WAD; TENS for acute WAD, chronic MND; PEMF for medium- or long-term effects in acute WAD, chronic MND); and limited evidence of no benefit (diadynamic current for reduction of trigger point tenderness in chronic MND, cervicogenic headache; permanent magnets for chronic MND; electrical muscle stimulation (EMS) for chronic MND). CONCLUSIONS: In pain as well as other outcomes, the evidence for treatment of acute or chronic MND by different forms of electrotherapy is either lacking, limited, or conflicting.
The influence of an applied microwave field on the dynamics of methylamine-dichloromethane (DCM) mixtures bound within atactic polystyrene (a-PS) over a range of polymer densities from 30 to 94 wt % polymer was examined using atomistic molecular dynamics simulations. This study is an extension of previous studies on methylamine transport in relatively polar polystyrene solutions of methanol and dimethylformamide [M. J. Purdue et al., J. Chem. Phys. 124, 204904 (2006)]. A direct comparison is made across the three types of polystyrene solutions. Consideration is given to both solvent and reagent transport within the polymer solutions under zero-field conditions and in an external electromagnetic field in the canonical ensemble (NVT) at 298.0 K. Various frequencies up to 10(4) GHz and a rms electric field intensity of 0.1 VA were applied. The simulation studies were validated by comparison of the simulated zero-field self-diffusion coefficients of DCM in a-PS with those obtained using pulsed-gradient spin-echo NMR spectrometry. Athermal effects of microwave fields on solute transport behavior within polymer solutions are discussed.
Specific weak time varying pulsed magnetic fields (MF) have been shown to alter animal and human behaviors, including pain perception and postural sway. Here we demonstrate an objective assessment of exposure to pulsed MF's on Rheumatoid Arthritis (RA) and Fibromyalgia (FM) patients and healthy controls using standing balance. 15 RA and 15 FM patients were recruited from a university hospital outpatient Rheumatology Clinic and 15 healthy controls from university students and personnel. Each subject stood on the center of a 3-D forceplate to record postural sway within three square orthogonal coil pairs (2 m, 1.75 m, 1.5 m) which generated a spatially uniform MF centered at head level. Four 2-min exposure conditions (eyes open/eyes closed, sham/MF) were applied in a random order. With eyes open and during sham exposure, FM patients and controls appeared to have similar standing balance, with RA patients worse. With eyes closed, postural sway worsened for all three groups, but more for RA and FM patients than controls. The Romberg Quotient (eyes closed/eyes open) was highest among FM patients. Mixed design analysis of variance on the center of pressure (COP) movements showed a significant interaction of eyes open/closed and sham/MF conditions [F=8.78(1,42), P<0.006]. Romberg Quotients of COP movements improved significantly with MF exposure [F=9.5(1,42), P<0.005] and COP path length showed an interaction approaching significance with clinical diagnosis [F=3.2(1,28), P<0.09]. Therefore RA and FM patients, and healthy controls, have significantly different postural sway in response to a specific pulsed MF.
Proton-proton cross-relaxation rates have been measured for the trisaccharide beta-D-Glcp-(l --> 2)[beta-D-Glcp-(1 --> 3)]alpha-D-Glcp-OMe in D2O as well as in D2O/[D6]DMSO 7:3 solution at 30 degrees C by means of one-dimensional NMR pulsed field gradient 1H,1H NOESY and TROESY experiments. Interatomic distances for the trisaccharide in D2O were calculated from the cross-relaxation rates for two intraresidue and three interglycosidic proton pairs, using the isolated spin-pair approximation. In the solvent mixture one intraresidue and three interglycosidic distances were derived without the use of a specific molecular model. In this case the distances were calculated from the cross-relaxation rates in combination with "model-free" motional parameters previously derived from 13C relaxation measurements. The proton-proton distances for interglycosidic pairs were compared with those averaged from Metropolis Monte Carlo and Langevin Dynamics simulations with the HSEA, PARM22, and CHEAT95 force fields. The crystal structure of the trisaccharide was solved by analysis of X-ray data. Interresidue proton pairs from the crystal structure and those observed by NMR experiments were similar. However, the corresponding proton-proton distances generated by computer simulations were longer. For the (1 --> 2) linkage the glycosidic torsion angles of the crystal structure were found in a region of conformational space populated by all three force fields, whereas for the (1 --> 3) linkage they occupied a region of low population density, as seen from the simulations.
The open field test (OFT) is a widely used procedure for examining the behavioral effects of drugs and anxiety. Detailed ethological assessments of animal behavior are lacking. Here we present a detailed ethological assessment of the effects of acute treatment with the benzodiazepines, diazepam (DZ, 1.5mg/kg) and chlordiazepoxide (CDP, 5.0 and 10.0mg/kg), as well as exposure to a non-pharmacological agent, a specific pulsed extremely low frequency magnetic field (MAG) on open field behavior. We examined the duration, frequency and time course of various behaviors (i.e. exploration, walk, rear, stretch attend, return, groom, sit, spin turn, jump and sleep) exhibited by male mice in different regions of a novel open field. Both DZ and CDP consistently reduced the typical anxiety-like behaviors of stretch attend and wall-following (thigmotaxis), along with that of an additional new measure: 'returns', without producing any overall effects on total locomotion. The drugs also differed in their effects. CDP elicited a shift in the locomotor pattern from a 'high explore' to a 'high walk', while DZ mainly elicited alterations in sit and groom. The MAG treatment was repeated twice with both exposures reducing horizontal and vertical (rearing) activity and increasing grooming and spin turns. However, the anxiety-like behaviors of stretch attend and return were marginally reduced by only the first exposure. We conclude that a detailed ethological analysis of the OFT allows not only the detection of specific effects of drugs and non-pharmacological agents (i.e. pulsed magnetic field) on anxiety-like behaviors, but also permits the examination of non-specific effects, in particular those on general activity.
This paper evaluates a new, low-frequency finite-difference time-domain method applied to the problem of induced E-fields/eddy currents in the human body resulting from the pulsed magnetic field gradients in MRI. In this algorithm, a distributed equivalent magnetic current is proposed as the electromagnetic source and is obtained by quasistatic calculation of the empty coil's vector potential or measurements therein. This technique circumvents the discretization of complicated gradient coil geometries into a mesh of Yee cells, and thereby enables any type of gradient coil modelling or other complex low frequency sources. The proposed method has been verified against an example with an analytical solution. Results are presented showing the spatial distribution of gradient-induced electric fields in a multi-layered spherical phantom model and a complete body model.
The analysis and fractionation of large DNA molecules plays a key role in many genome projects. The standard method, pulsed-field gel electrophoresis (PFGE), is slow, with running times ranging from 10 hours to more than 200 hours. In this report, we describe a thumbnail-sized device that sorts large DNA fragments (61-209 kilobases (kb)) in 15 seconds, with a resolution of approximately 13%. An array of micron-scale posts serves as the sieving matrix, and integrated microfluidic channels spatially shape the electric fields over the matrix. Asymmetric pulsed fields are applied for continuous-flow operation, which sorts DNA molecules in different directions according to their molecular masses, much as a prism deflects light of different wavelengths at different angles. We demonstrate the robustness of the device by using it to separate large DNA inserts prepared from bacterial artificial chromosomes, a widely used DNA source for most genomics projects.
Electromagnetic fields significantly influence healing in tibial fractures with delayed union. A total of 45 tibial shaft fractures, all conservatively treated and with union delayed for more than 16 to less than 32 weeks were entered into this double-blind multi-center trial.
A total of 45 tibial shaft fractures, all conservatively treated and with union delayed for more than 16 but less than 32 weeks were entered in a double-blind multi-centre trial. The fractures were selected for their liability to delayed union by the presence of moderate or severe displacement, angulation or comminution or a compound lesion with moderate or severe injury to skin and soft tissues. Treatment was by plaster immobilisation in all, with active electromagnetic stimulation units in 20 patients and dummy control units in 25 patients for 12 weeks. Radiographs were assessed blindly and independently by a radiologist and an orthopaedic surgeon. Statistical analysis showed the treatment groups to be comparable except in their age distribution, but age was not found to affect the outcome and the effect of treatment was consistent for each age group. The radiologist's assessment of the active group showed radiological union in five fractures, progress to union in five but no progress to union in 10. In the control group there was union in one fracture and progress towards union in one but no progress in 23. Using Fisher's exact test, the results were very significantly in favour of the active group (p = 0.002). The orthopaedic surgeon's assessment showed union in nine fractures and absence of union in 11 fractures in the active group. There was union in three fractures and absence of union in 22 fractures in the control group. These results were also significantly in favour of the active group (p = 0.02). It was concluded that pulsed electromagnetic fields significantly influence healing in tibial fractures with delayed union.
OBJECTIVE. Further evaluation of pulsed electromagnetic fields (PEMF), which have been observed to produce numerous biological effects, and have been used to treat delayed union fractures for over a decade. METHODS. In a pilot, double-blind randomized trial, 27 patients with osteoarthritis (OA), primarily of the knee, were treated with PEMF. Treatment consisted of 18 half-hour periods of exposure over about 1 month in a specially designed noncontact, air-coil device. Observations were made on 6 clinical variables at baseline, midpoint of therapy, end of treatment and one month later; 25 patients completed treatment. RESULTS. An average improvement of 23-61% occurred in the clinical variables observed with active treatment, while 2 to 18% improvement was observed in these variables in placebo treated control patients. No toxicity was observed. CONCLUSION. The decreased pain and improved functional performance of treated patients suggests that this configuration of PEMF has potential as an effective method of improving symptoms in patients with OA. This method warrants further clinical investigation.
Brief cerebral application of picotesla (pT) electromagnetic fields (EMF) has been demonstrated an efficacious, revolutionary treatment modality for the therapy of Parkinson's disease (PD) with clinical benefits being evident in all motor aspects of the disease as well as in nonmotor symptoms such as mood, sleep, pain, sexual dysfunction, autonomic regulation and cognitive functions. Since treatment with pT EMF has involved PD patients who were treated with dopaminergic agents at the time they received EMF there may have been a synergistic interaction between dopaminergic drugs and EMF. The present communication concerns a 49-year-old male Parkinsonian patient with stage 3 disability on the Hoehn and Yahr scale (1967) who, in response to brief extracranial applications of pT EMF, demonstrated a marked improvement in motor, depressive symptomatology and cognitive functions and was classified as stage 1 several weeks later. This case is remarkable in that the patient did not receive treatment with dopaminergic drugs prior to or during the course of EMF therapy. It suggests that (a) pT range EMF may be efficacious as a monotherapy for PD and should be considered also as a treatment modality for de novo diagnosed patients, and (b) application of these EMF improves Parkinsonism by a mechanism which involves, among others, augmentation of dopaminergic and serotonergic neurotransmission.
Low strength magnetic fields, 6.36 and 32.25 gauss, were found to have no effect, with one questionable exception, on the circadian rhythm and growth rate of Neurospora crassa. This was true whether the fields were continuous, pulsed 20 minutes daily, or on a 12: 12, on-off cycle.
Transcranial Magnetic Stimulation (TMS) is the process in which electrical activity in the brain is influenced by a pulsed magnetic field. Common practice is to align an electromagnetic coil with points of interest identified on the surface of the brain, from an MRI scan of the subject. The coil can be tracked using optical sensors, enabling the targeting information to be calculated and displayed on a local workstation. In this paper we explore the hypothesis that using an Augmented Reality (AR) interface for TMS will improve the efficiency of carrying out the procedure. We also aim to provide a flexible infrastructure that if required, can seamlessly deploy processing power from a remote high performance computing resource.
The hydration behavior of two model disaccharides, methyl-alpha-D-maltoside (1) and methyl-alpha-D-isomaltoside (2), has been investigated by a comparative 10 ns molecular dynamics study. The detailed hydration of the two disaccharides was described using three force fields especially developed for modeling of carbohydrates in explicit solvent. To validate the theoretical results the two compounds were synthesized and subjected to 500 MHz NMR spectroscopy, including pulsed field gradient diffusion measurements (1: 4.0. 10(-6) cm(2). s(-1); 2: 4.2. 10(-6) cm(2). s(-1)). In short, the older CHARMM-based force field exhibited a more structured carbohydrate-water interaction leading to better agreement with the diffusional properties of the two compounds, whereas especially the alpha-(1-->6) linkage and the primary hydroxyl groups were inaccurately modeled. In contrast, the new generation of the CHARMM-based force field (CSFF) and the most recent version of the AMBER-based force field (GLYCAM-2000a) exhibited less structured carbohydrate-water interactions with the result that the diffusional properties of the two disaccharides were underestimated, whereas the simulations of the alpha-(1-->6) linkage and the primary hydroxyl groups were significantly improved and in excellent agreement with homo- and heteronuclear coupling constants. The difference between the two classes of force field (more structured and less structured carbohydrate-water interaction) was underlined by calculation of the isotropic hydration as calculated by radial pair distributions. At one extreme, the radial O em leader O pair distribution function yielded a peak density of 2.3 times the bulk density in the first hydration shell when using the older CHARMM force field, whereas the maximum density observed in the GLYCAM force field was calculated to be 1.0, at the other extreme.
A review of the literature involving the effects of MFs on microcirculation and microvasculature indicates that nearly half of the cited experiments (10 of 27 studies) report either a vasodilatory effect due to MF exposure, increased blood flow, or increased blood pressure. Conversely, three of the 27 studies report a decrease in blood perfusion/pressure. Four studies report no effect. The remaining ten studies found that MF exposure could trigger either vasodilation or vasoconstriction depending on the initial tone of the vessel. For a summary, please refer to Table 3. In terms of cellular effects of MFs related to perfusion, four of a total of 19 studies report an increase in NO activity as a result of MF exposure (one of these studies used a model with an altered vessel state prior to exposure); one found a biphasic effect; five found no effect. Nine studies report vascular development effects (seven report increased angiogenesis, two report decreased angiogenesis). Other cellular effects are reported in three studies. For a summary, please refer to Table 4. Clearly, this is an area of research that would benefit from increased investigation. There are many therapeutic applications of locally increased blood flow. It is suggestive that MFs do have the potential to modify microcirculatory perfusion, however, this statement is far from proven.
This report outlines a simple mechanism, based on the Hall Effect, by which static and low frequency (50-60 Hz) pulsed electromagnetic fields (PEMFs) can modify cation flow across biological membranes and alter cell metabolism. We show that magnetic fields commonly found in the environment can be expected to cause biologically significant interactions between transported cations and basic domains of cation channel proteins. We calculate that these interactions generate forces of a magnitude similar to those created by normal transmembrane voltage changes known to gate cation channels. Thus PEMFs are shown to have the potential of regulating flow through cation channels, changing the steady state concentrations of cellular cations and thus the metabolic processes dependent on cation concentrations.
OBJECTIVES--The objective of this study was to investigate the mortality of electrical utility workers exposed to electric and magnetic fields. METHODS--A historical cohort mortality study was carried out on 21,744 workers who were employed in an electrical company in the province of Quebec between 1970 and 1988. The last job held by each study subject was coded. A job exposure matrix (JEM) was used to estimate the exposure to 60 Hz electric and magnetic fields, and pulsed electromagnetic fields (as recorded by the PEMF (POSITRON) meter) in this job. Standardised mortality ratios (SMRs) were calculated relative to Quebec men. Because the exposure was exclusively among blue collar workers, the remainder of the analyses by exposure were restricted to them. Rate ratios (RRs) in the exposed groups relative to the background groups were estimated with Poisson regression. There were 1582 deaths by the end of follow up. RESULTS--SMRs were almost all below one and never substantially increased, although there were a few increased rate ratios (RRs). There was a significant RR of 2.00 (95% confidence interval (95% CI) 1.37-2.93) for deaths caused by accidents and violence in workers exposed to magnetic fields, RR of 1.82 (95% CI 1.25-2.65) for electric fields, and RR of 1.62 (95% CI 1.13-2.32) for pulsed electromagnetic fields. Occupational accidents related to power lines explain some of the excess of deaths from accidents and violence. Some association was found between magnetic fields and leukaemia, brain cancer, and suicide, between electric fields and brain cancer and suicide, and between pulsed electromagnetic fields and lung cancer, but these were not significant. CONCLUSION--These results are broadly reassuring that major causes of death are not strongly associated with exposure to electric and magnetic fields, but small numbers and approximate exposure assessments preclude the denial of any risk, in particular if it were to affect a rare cause of death.
STATEMENT OF THE PROBLEM: Pulsed electromagnetic fields have shown therapeutic benefit in the treatment of numerous forms of osteoarthritis but have not been evaluated for their effects on the temporomandibular joint (TMJ). PURPOSE: The aim of this study was to examine the effects of pulsed electromagnetic fields in the treatment of patients with temporomandibular disorders (TMD). MATERIALS AND METHODS: A multicenter clinical trial compared active treatment of 36 patients using pulsed electromagnetic fields to placebo treatment of 42 patients with TMD with pain in 1 or both TMJs and/or limited opening of less than 40 mm. Subjective parameters including pain intensity, pain frequency, degree of limitation, restriction of daily life, and intensity and frequency of joint noises were evaluated using a visual analog scale. Trained, blinded examiners assessed the clinical parameters according to Research Diagnostic Criteria for temporomandibular disorders before treatment (baseline), directly after nine 1-hour treatments on consecutive working days, 6 weeks after treatment, and 4 months after treatment. Statistical evaluation was done using the Friedman test, and by paired comparison between baseline and follow-up examinations using the U test (P < .05). RESULTS: Seventy-six patients completed the study. For both the active and placebo treatment, significant improvements were seen in the subjective data (P < .01). Patients with anterior disk displacement without reduction also showed significant improvements in active mouth opening (P = .015), patients with ostheoarthritis only showed improvements in some of the subjective parameters (P < .03), and patients with anterior disk displacement with reduction showed no improvement at all. CONCLUSIONS: Pulsed electromagnetic fields had no specific treatment effects in patients with temporomandibular disorders.
Bursts of highly synchronized discharges of 4-7Hz sinusoidal wave activity can be recorded from the hippocampus during rapid eye movement (REM) sleep. These rhythmic discharges, the hippocampal theta activity, are generated in the dentate granule cells and the pyramidal cell layers of the CA1 field of the hippocampus. The physiological function of the hippocampal theta activity is elusive. The occurrence of this rhythm throughout the REM sleep stage suggests that it is related to some fundamental neurophysiological phenomena associated with REM sleep, particularly consolidation of memory processes. Synchronous oscillations among a population of neurons are expected to yield stronger, more coherent associated magnetic fields which, through their influence back on the electrical fields via induction, would exert an independent effect on the electrical activity of hippocampal neurons and additionally, could foster and reinforce these oscillations through self-induction. The snail-shaped structure of the hippocampal formation, which resembles a solenoid embedded in the temporal lobe, would be expected to amplify these magnetic fields. Additionally, the discovery of large ferromagnetic particles in the human hippocampus suggests that it may function as a large iron-core electromagnet. It is proposed that memory traces may be encoded or decoded magnetically and analogous to a videotape, each encoding unit (i.e., synapse, set of synapses or glial cell) could be magnetized in one direction, or the other through the flow of a strong, AC magnetic field along the hippocampal formation. The encoding of memory traces in the hippocampal formation may ultimately reflect an electromagnetic phenomenon.
In order to determine the mechanical properties of the vitreous which are characteristic for the extraction of foreign bodies, an oscillatory method was devised. The mechanical properties are described by a spring constant--relevant for the rubber elastic behaviour--and a friction constant characterizing the dissipative interaction inside the vitreous. The appropriateness of the data is demonstrated by the capability to predict the distance-time behaviour in strong, pulsed magnetic fields of ferromagnetic foreign bodies implanted into the vitreous of pig eyes.
The question whether pulsed electromagnetic field (PEMF) can affect the heart rhythm is still controversial. This study investigates the effects on the cardiocirculatory system of ELF-PEMFs. It is a follow-up to an investigation made of the possible therapeutic effect ELF-PEMFs, using a commercially available magneto therapeutic unit, had on soft tissue injury repair in humans. Modulation of heart rate (HR) or heart rate variability (HRV) can be detected from changes in periodicity of the R-R interval and/or from changes in the numbers of heart-beat/min (bpm), however, R-R interval analysis gives only a quantitative insight into HRV. A qualitative understanding of HRV can be obtained considering the power spectral density (PSD) of the R-R intervals Fourier transform. In this study PSD is the investigative tool used, more specifically the low frequency (LF) PSD and high frequency (HF) PSD ratio (LF/HF) which is an indicator of sympatho-vagal balance. To obtain the PSD value, variations of the R-R time intervals were evaluated from a continuously recorded ECG. The results show a HR variation in all the subjects when they are exposed to the same ELF-PEMF. This variation can be detected by observing the change in the sympatho-vagal equilibrium, which is an indicator of modulation of heart activity. Variation of the LF/HF PSD ratio mainly occurs at transition times from exposure to nonexposure, or vice versa. Also of interest are the results obtained during the exposure of one subject to a range of different ELF-PEMFs. This pilot study suggests that a full investigation into the effect of ELF-PEMFs on the cardiovascular system is justified.
A prospective, randomized, double-blind, placebo-controlled multicentre study assessed the clinical efficacy and safety of pulsed electromagnetic limb ulcer therapy (PELUT) in the healing of recalcitrant, predominantly venous leg ulcers. The portable device was used at home for 3 h daily during this 8-week clinical trial as an adjunct to a wound dressing. Wound surface area, ulcer depth and pain intensity were assessed at weeks 0, 4 and 8. At week 8 the active group had a 47.7% decrease in wound surface area vs. a 42.3% increase for placebo (P < 0.0002). Investigators' global evaluations indicated that 50% of the ulcers in the active group healed or markedly improved vs. 0% in the placebo group, and 0% of the active group worsened vs. 54% of the placebo group (P < 0.001). Significant decreases in wound depth (P < 0.04) and pain intensity (P < 0.04) favouring the active group were seen. Patients whose ulcers improved significantly after 8 weeks were permitted to continue double-blind therapy for an additional 4 weeks. Eleven active and one placebo patient continued therapy until week 12, with the active treatment group continuing to show improvement. There were no reports of adverse events attributable to this device. We conclude that the PELUT device is a safe and effective adjunct to non-surgical therapy for recalcitrant venous leg ulcers.
This study exposed rats to a 55.6 Hz, 8.1 mill-Tesla magnetic field for four days, six hours each day. This produced measurable analgesic effects, and decreased sensitivity to pain. Concentrations of beta Endorphin in the hypothalamus, substance P., and brainstem serotonin were increased significantly on day four. However, no differences were found in these substances when rats were exposed for another 10 days. The study concludes that the analgesic effect of magnetic fields at the studied intensities was observed on days 3 and 4 only, and not beyond this from day 5 to 10.
Chinese hamster ovary cells have been exposed to high-voltage electric fields causing electroporation (EP) and the interaction between EP and radiation-induced cell lethality investigated. There was a voltage-dependent decrease in plating efficiency, assessed immediately following EP, and cell viability, assessed at 24 h. A linear decrease was seen for both. These decreases were accompanied by a voltage-dependent increase in cell volume, assessed immediately following EP. A good correlation between increases in cell volume and decreases in plating efficiency was seen (r = -0.91). The application of electric fields immediately prior to, or following, irradiation led to a radiosensitization of the cells. This radiosensitization still occurred when a 6 h interval was left between radiation and EP but was lost when cells were irradiated 24 h prior to EP. When cells were irradiated following EP, the radiosensitization was lost with a 1 h interval between the two treatments. These results suggest that, when studying the combined cellular effects of EP of macromolecules and radiation, care should be taken that sufficient time has elapsed between the two modalities to prevent the radiosensitization of cells.
Marine-life scientists around the world are already carrying out investigative trials to obtain higher yields under in-captive breeding conditions, on both edible varieties and ornamental fishes with optimal inputs. However, for such trials to succeed there is a need for genetic improvement. The idea that fish production can be enhanced by genetic manipulation is gaining acceptance, as there is a strong possibility that qualitative improvement of economically important traits can be achieved by identifying and utilizing more effective genotypes. In the present communication a tentative plan for genetic manipulation of fresh water fish using controlled, pulsed magnetic fields, is being discussed. Chromosome preparations of Labeo rohita were made using Colchicine-Methanol-Acetic acid air drying technique, using tissue from gills. The fish were exposed to Pulsed Magnetic Field (PMF)with intensity 0.2 Gauss, pulsing at 50 Hz frequency (sine wave) for 6 hours / day for a total period of 30 days inside specially designed magnetic field enclosures. The karyological investigations revealed no distinct difference between "test" and "control" groups.
Time-varying magnetic fields induce currents in conductive media, and when the induced current is large enough in excitable tissue, stimulation occurs. This phenomenon has been applied to the human brain and peripheral nerves for diagnostic evaluation of the neural system. One important aspect that is presently unknown is the current level necessary in tissue for stimulation induced by magnetic fields. This study presents a method of measuring the induced current density from pulsed magnetic fields in vitro and in vivo. The current-density probe was inserted into three concentrations of saline and into the brains of ten anesthetized cats. Two stimulation systems with coils 9 cm and 5 cm in diameter were used. The two systems provided sinusoidal and pulsatile coil currents. Measurements made in saline were compared with those calculated theoretically for a semi-infinite medium. The measured values were within 5% of the calculated values. Measurements made in the cat brain showed a 67% decrease compared with the theoretic model. This variance is attributed to the finite bounds of the skull. The results indicate that direct measurement of current density is possible. Subsequent measurements will aid in the design of improved magnetic stimulation systems.
Osteoarthritis is a debilitating joint disease where the surface of articular cartilage degrades and is unable to repair itself through natural processes. Controlling the migration of transplanted chondrocytes to the defective cartilage non-invasively could be a novel treatment for osteoarthritis. Our research group has performed an in-vitro investigation into the response of cultured human chondrocytes to pulsed electromagnetic fields (PEMF). Development of a treatment for osteoarthritis patients will require the use of a programmable waveform generator to generate the PEMF. This paper discusses the design and testing of a programmable ramp waveform generator for such purpose. When this ramp waveform generator is connected to the PEMF coil driver circuitry, it will be able to produce linearly ramping magnetic fields ranging in strength from 0.5 mT to 4.5 mT. It also has an attainable pulse width ranging from 6 ms to 100 ms, with a selectable duty cycle from 1% to 99%
The ability to cool and manipulate atoms with light has yielded atom interferometry, precision spectroscopy, Bose-Einstein condensates and atom lasers. The extension of controlled manipulation to molecules is expected to be similarly rewarding, but molecules are not as amenable to manipulation by light owing to a far more complex energy-level spectrum. However, time-varying electric and magnetic fields have been successfully used to control the position and velocity of ions, suggesting that these schemes can also be used to manipulate neutral particles having an electric or magnetic dipole moment. Although the forces exerted on neutral species are many orders of magnitude smaller than those exerted on ions, beams of neutral dipolar molecules have been successfully slowed down in a series of pulsed electric fields and subsequently loaded into an electrostatic trap. Here we extend the scheme to include a prototype electrostatic storage ring made of a hexapole torus with a circumference of 80 cm. After injection, decelerated bunches of deuterated ammonia molecules, each containing about 106 molecules in a single quantum state and with a translational temperature of 10 mK, travel up to six times around the ring. Stochastic cooling might provide a means to increase the phase-space density of the stored molecules in the storage ring, and we expect this to open up new opportunities for molecular spectroscopy and studies of cold molecular collisions.
We used electric pulses to permeabilize porcine stratum corneum and demonstrate enhanced epidermal transport of methylene blue, a water-soluble cationic dye. Electrodes were placed on the outer surface of excised full-thickness porcine skin, and methylene blue was applied to the skin beneath the positive electrode; 1 ms pulses of up to 240 V were delivered at frequencies of 20-100 Hz for up to 30 min. The amount of dye in a skin sample was determined from absorbance spectra of dissolved punch biopsy sections. Penetration depth and concentration of the dye were measured with light and fluorescence microscopy of cryosections. At an electric exposure dose VT (applied voltage x frequency x pulse width x treatment duration) of about 4700 Vs, there is a threshold for efficient drug delivery. Increasing the applied voltage or field application time resulted in increased dye penetration. Transport induced by electric pulses was more than an order of magnitude greater than that seen following iontophoresis. We believe that the enhanced cutaneous delivery of methylene blue is due to a combination of de novo permeabilization of the stratum corneum by electric pulses, passive diffusion through the permeabilization sites, and electrophoretic and electroosmotic transport by the electric pulses. Pulsed electric fields may have important applications for drug delivery in a variety of fields where topical drug delivery is a goal.
A variable-pulse electromagnetic pulse generator has been developed to study the effect of the magnetic field on bone growth. The unit's repetition frequency can be varied from 2 to 200 Hz, and the peak current that it can drive is 10 A. The duty cycle of the pulse can be varied in steps of 10, 12.5, 17, 25, 50, 75, 83, 87.5, and 90% and is independent of the repetition frequency. The trailing edge of the output pulse can be controlled to produce any desired voltage-time pulse characteristic. This decay adjustment makes it possible to generate a variable-pulse frequency spectrum.
A potential treatment modality for joint pain due to cartilage degradation is electromagnetic fields (EMF) that can be delivered, noninvasively, to chondrocytes buried within cartilage. A pulsed EMF in clinical use for recalcitrant bone fracture healing has been modified to be delivered as a pulsed electric field (PEF) through capacitive coupling. It was the objective of this study to determine whether the PEF signal could have a direct effect on chondrocytes in vitro. This study shows that a 30-min PEF treatment can increase DNA content of chondrocyte monolayer by approximately 150% at 72 h poststimulus. Studies intended to explore the biological mechanism showed this PEF signal increased nitric oxide measured in culture medium and cGMP measured in cell extract within the 30-min exposure period. Increasing calcium in the culture media or adding the calcium ionophore A23187, without PEF treatment, also significantly increased short-term nitric oxide production. The inhibitor W7, which blocks calcium/calmodulin, prevented the PEF-stimulated increase in both nitric oxide and cGMP. The inhibitor L-NAME, which blocks nitric oxide synthase, prevented the PEF-stimulated increase in nitric oxide, cGMP, and DNA content. An inhibitor of guanylate cyclase (LY83583) blocked the PEF-stimulated increase in cGMP and DNA content. A nitric oxide donor, when present for only 30 min, increased DNA content 72 h later. Taken together, these results suggest the transduction pathway for PEF-stimulated chondrocyte proliferation involves nitric oxide and the production of nitric oxide may be the result of a cascade that involves calcium, calmodulin, and cGMP production.
A randomized double-blind prospective study of pulsed electromagnetic fields for lumbar interbody fusions was performed on 195 subjects. There were 98 subjects in the active group and 97 subjects in the placebo group. A brace containing equipment to induce an electromagnetic field was applied to patients undergoing interbody fusion in the active group, and a sham brace was used in the control group. In the active group there was a 92% success rate, while the control group had a 65% success rate (P greater than 0.005). The effectiveness of bone graft stimulation with the device is thus established.
Exposure to a specific pulsed electromagnetic field (PEMF) has been shown to produce analgesic (antinociceptive) effects in many organisms. In a randomized, double-blind, sham-controlled clinical trial, patients with either chronic generalized pain from fibromyalgia (FM) or chronic localized musculoskeletal or inflammatory pain were exposed to a PEMF (400 microT) through a portable device fitted to their head during twice-daily 40 min treatments over seven days. The effect of this PEMF on pain reduction was recorded using a visual analogue scale. A differential effect of PEMF over sham treatment was noticed in patients with FM, which approached statistical significance (P=0.06) despite low numbers (n=17); this effect was not evident in those without FM (P=0.93; n=15). PEMF may be a novel, safe and effective therapeutic tool for use in at least certain subsets of patients with chronic, nonmalignant pain. Clearly, however, a larger randomized, double-blind clinical trial with just FM patients is warranted.
This paper presents an overview of the application of and risks of exposure to Magnetic Resonance Imaging (MRI) in pregnancy. It reviews the risks to the fetus by considering the hazards in terms of the three main components of an MRI system. These are the static magnetic field, the time-varying magnetic gradient fields and the pulsed radio frequency fields. The hazards discussed are biological effects, miscarriage, heating effects and acoustic noise exposure. This paper also presents a survey of MRI sites within the United Kingdom to ascertain the extent of MRI usage in pregnancy. To validate the situation of MRI in pregnancy a survey was sent to 352 MR units throughout the United Kingdom. The questions were grouped to assess (a) maternal MRI diagnosis (b) fetal MRI and (c) work practices for pregnant MRI staff. The results showed that 91% of sites were imaging pregnant women in need of diagnosis in the second and third trimester. This paper highlights that MRI can add information for fetal central nervous system abnormalities identified by ultrasound screening, however within the UK direct fetal imaging was only performed in 8% of sites. This paper indicates the need for research to be undertaken for specific MRI clinical conditions. It also advises that risk assessment for pregnant staff working in MRI is performed, and that there is a clear need for further research into the effects of MRI in pregnancy as there is a need for clear authoritive advice.
Complex permittivity values have a dominant role in the overall consideration of interaction between radiofrequency electromagnetic fields and living matter, and in related applications such as electromagnetic dosimetry. There are still some concerns about the accuracy of published data and about their variability due to the heterogeneous nature of biological tissues. The aim of this study is to provide an alternative semi-automatic method by which numerical dielectric human models for dosimetric studies can be obtained. Magnetic resonance imaging (MRI) tomography was used to acquire images. A new technique was employed to correct nonuniformities in the images and frequency-dependent transfer functions to correlate image intensity with complex permittivity were used. The proposed method provides frequency-dependent models in which permittivity and conductivity vary with continuity--even in the same tissue--reflecting the intrinsic realistic spatial dispersion of such parameters. The human model is tested with an FDTD (finite difference time domain) algorithm at different frequencies; the results of layer-averaged and whole-body-averaged SAR (specific absorption rate) are compared with published work, and reasonable agreement has been found. Due to the short time needed to obtain a whole body model, this semi-automatic method may be suitable for efficient study of various conditions that can determine large differences in the SAR distribution, such as body shape, posture, fat-to-muscle ratio, height and weight.
DNA fragmentation of 50 kb is observed in apoptotic human lymphocytes as measured with pulsed field gel electrophoresis (PFGE). Standard PFGE assay involves embedding of cells into agarose blocks followed by lysis in the presence of proteinase K. In this study, we modified the PFGE protocol by omitting the proteinase K. In this study, we modified the PFGE assay by omitting the proteinase K and changing lysis solution according to the method of anomalous viscosity time dependence (AVTD). The conditions of PFGE were adjusted aiming to compress apoptotic fragments, increasing sensitivity and the number of samples that could be loaded on the same gel. Lymphocytes were irradiated with gamma-rays and apoptotic fragmentation of DNA was determined by PFGE using standard lysis with proteinase K and lysis protocol from AVTD method. Both protocols of lysis resulted in the same pattern of DNA fragments. The yield of radiation-induced apoptotic fragmentation was higher with the AVTD protocol of lysis. The novel PFGE protocol is simple and relatively non-expensive, requires only 7 h running time and gives a possibility to analyse simultaneously up to 69 samples in the same gel. The sensitivity of our protocol provides reproducible detection of 50 kb fragmentation after irradiation of human lymphocytes with 5 cGy of gamma-rays. In 2 of 6 donors tested, this DNA fragmentation was detected at dose on 2 cGy. The novel protocol can be used for quantification of 50 kb apoptotic fragments induced by different agents including low dose ionising radiations, chemicals and electromagnetic fields.
BACKGROUND: We evaluate a simple, bedside test that measures 1-minute heart rate variability in deep breathing as a predictor of death after myocardial infarction. METHODS: Bedside heart rate variability was assessed in 185 consecutive patients 5.1 +/- 2.5 days after a first myocardial infarction. Patients were instructed to take 6 deep respirations in 1 minute while changes in heart rate were measured and calculated by an electrocardiographic recorder. An abnormal test result was defined as a difference of less than 10 beats/min between the shortest and longest heart rate interval. RESULTS: Heart rate variability <10 beats/min was found in 65 patients (35%) and was significantly lower (P <.05) in women, patients >60 years of age, patients with diabetes, patients with congestive heart failure, and patients taking angiotensin-converting enzyme inhibitors. Mean follow-up period was 16 months. Ten patients died during follow-up: 9 of cardiac causes and 1 of stroke. Nine of these 10 patients had heart rate variability <10 beats/min (P =.004). The sensitivity and specificity of this test for cardiovascular mortality is 90.0% and 68.0%, respectively. The negative predictive value is 99.2% and the relative risk is 16.6. Heart rate variability <10 beats/min remained a significant predictor of death after adjusting for clinical, demographic, and left ventricular function with an odds ratio of 1.38 (95% confidence interval, 1.13-1.63). CONCLUSIONS: This simple, brief bedside deep breathing test of heart rate variability in patients after myocardial infarction appears to be a good predictor for all-cause mortality and sudden death. It may be used as a clinical test for risk stratification after myocardial infarction.
BACKGROUND: Heart rate variability is a sensitive marker of cardiac sympathetic activity. OBJECTIVES: To determine whether long-term hyperthyroidism induced by thyroxine suppressive therapy affects HRV. METHODS: Nineteen patients treated with suppressive doses of thyroxin for thyroid cancer and 19 age-matched controls were enrolled. Thyroid function tests and 1 minute HRV were performed on all subjects and the results were compared between the groups. The 1 minute HRV was analyzed during deep breathing and defined as the difference in beats/minute between the shortest and the longest heart rate interval measured by eletrocardiographic recording during six cycles of deep breathing. RESULTS: One minute HRV during deep breathing was significantly lower among thyroxine-treated patients compared to healthy controls (25.6 +/- 10.5 vs. 34.3 +/- 12.6 beats/min, P < 0.05). There were no significant differences in mean, maximal and minimal heart rate between the groups. CONCLUSIONS: Thyroxine therapy administered for epithelial thyroid cancer resulted in subclinical hyperthyroidism and significantly decreased HRV due to autonomic dysfunction rather than basic elevated heart rate.
The interstitial space is a rate limiting physiological barrier to non-viral gene delivery. External pulsed electric fields have been proposed to increase DNA transport in the interstitium, thereby improving non-viral gene delivery. In order to characterize and improve the interstitial transport, we developed a reproducible single molecule detection method to observe the electromobility of DNA in a range of pulsed, high field strength electric fields typically used during electric field-mediated gene delivery. Using agarose gel as an interstitium phantom, we investigated the dependence of DNA electromobility on field magnitude, pulse duration, pulse interval, and pore size in the interstitial space. We observed that the characteristic electromobility behavior, exhibited under most pulsing conditions, consisted of three distinct phases: stretching, reptation, and relaxation. Electromobility depended strongly on the field magnitude, pulse duration, and pulse interval of the applied pulse sequences, as well as the pore size of the fibrous matrix through which the DNA migrated. Our data also suggest the existence of a minimum pulse amplitude required to initiate electrophoretic transport. These results are useful for understanding the mechanisms of DNA electromobility and improving interstitial transport of genes during electric field-mediated gene delivery.
The positive role of pulsed electromagnetic field (PEMF) therapy in rheumatoid arthritis (RA) is known. The differential role of serological status of patients in RA is also well known. This paper presents a study of the differential effects of PEMF therapy on the two serological groups of patients. The responses of the seropositive patients are found to be more subdued. Varying effects of the therapy in alleviating the different symptomatologies indicate that the rheumatoid factor (RF) is more resistant to PEMF.
An analysis of 13 studies of the teratological effects of pulsed magnetic fields on chick embryos from ten independent laboratories permits no clear conclusions. Comparatively little has been done to follow up on the reports by Juutilainen and coworkers on the effects of extremely low-frequency, sinusoidal magnetic fields on the malformation rate in chick embryos. Our attempt to follow up on their results using similar but not identical exposures of 10 microT, 50 Hz magnetic fields produced negative results.
E mu-Pim1 transgenic mice expressing a dysregulated Pim1 oncogene in their lymphoid cells were used to test whether exposure to 50 Hz magnetic fields can increase the frequency of malignant lymphoma in mice of a strain predisposed to develop such tumors spontaneously at low incidence. Specific-pathogen-free female mice were allocated randomly into groups of approximately 100 at 6-8 weeks of age and then exposed for 20 h/day for up to 18 months to sinusoidal magnetic fields of 0, 1, 100 or 1000 microT, or 1000 microT pulsed 15 min on and 15 min off. Additional E mu-Pim1 mice were injected with ethylnitrosourea (50 mg/kg body weight) as positive controls for enhanced lymphomagenesis; these yielded a cumulative incidence of lymphoma of 60% in 9 months. A lethal, transgene-dependent renal glomerular disease occurred at a frequency that varied from 9% to 19% among the groups, but the increase was statistically significant only at the 1000-microT exposure. Lymphoblastic and non-lymphoblastic (predominantly follicular) lymphomas were seen in 26 to 35% of the exposed mice, but at no significantly higher incidence than the 29% found in the sham-exposed mice. Hence we conclude that the lymphoma-prone mice did not reveal any tumorigenic effect of long-term exposure to 50 Hz magnetic fields.
Physiologic magnetic fields of the order 10(-8) gauss have been unified with their propitiators: quantum genetic particles, the gravitational potential of which is about an erg. As these fields are applied to the equation for solenoidal models, B = micro NI/L, currents of about a microampere are derived; in perfect accord with recent clinical data indicating the therapeutic efficacy of weak currents in repair and growth of soft tissue, bone and nerve. The mechanism of reorientation of spin angular momentum of leptons and baryons influencing molecular magnetic domains to bring about 'particle jumps' is presented so that a clinical picture results. The clinical picture is that of an organism placed at right angles to flux lines in the midst of a solenoid immersed in water exposed then to exogenously applied resonant physiologic magnetic fields which convert malalligned atomic lattices of oncogenes and associated particles to homologous normal structures.
A model eukaryotic cell system was used to explore the effect of a weak pulsed magnetic field (PMF) on time-varying physiological parameters. Dictyostelium discoideum cells (V12 strain) were exposed to a pulsed magnetic field (PMF) of flux density 0.4 mT, generated via air-cored coils in trains of 2 ms pulses gated at 20 ms. This signal is similar to those used to treat non-uniting fractures. Samples were taken over periods of 20 min from harvested suspensions of amoebae during early aggregation phase, extracted and derivatised for HPLC fluorescent assay of adenine nucleotides. Analysis of variance showed a significant athermal damping effect (P < 0.002, n = 22) of the PMF on natural adenine nucleotide oscillations and some consistent changes in phase relationships. The technique of nonlinear dielectric spectroscopy (NLDS) revealed a distinctive effect of PMF, caffeine and EGTA in modulating the cellular harmonic response to an applied weak signal. Light scattering studies also showed altered frequency response of cells to PMF, EGTA and caffeine. PMF caused a significant reduction of caffeine induced cell contraction (P < 0.0006, n = 19 by paired t-test) as shown by Malvern particle size analyser, suggesting that intracellular calcium may be involved in mediating the effect of the PMF.
This investigation examined two questions: 1) whether or not forelimb regeneration results in a faithful replacement of the distal skeletal pattern and 2) what effect exposure to a pulsed electromagnetic field (PEMF), the type reported to facilitate healing of human non-united bone fractures, would have on the process of limb regeneration. Of the native forelimbs, 98% (132 out 134) had a skeletal pattern that showed little difference with the only variation being the range of carpal bones (5-8). Following a 4-5 month postamputation period, the skeletal pattern of the normal regenerates was examined. While 72% (135 out of 188) of these forelimbs resembled the native group, 28% (53 out of 188) were abnormal. These abnormalities consisted of the loss of a digit, fused carpals, and long bone defects which occurred singly or in combination with one another. Exposure to a PEMF for the first 30 days postamputation, followed by a 3-4 month postamputation period, produced in addition to the normal (60%, 144 out of 240) and abnormal forelimbs (28%, 67 out of 240), a group of forelimbs with unique gross defects (12%, 28 out of 240). These defects, occurring singly or in combination, included the loss of two or more digits with associated loss of carpals, absence of the entire hand pattern, and abnormalities associated with the radius and ulna. We can offer no explanation for these observations.
Sexual dysfunction is common in patients with Parkinson's disease (PD) since brain dopaminergic mechanisms are involved in the regulation of sexual behavior. Activation of dopamine D2 receptor sites, with resultant release of oxytocin from the paraventricular nucleus (PVN) of the hypothalamus, induces sexual arousal and erectile responses in experimental animals and humans. In Parkinsonian patients subcutaneous administration of apomorphine, a dopamine D2 receptor agonist, induces sexual arousal and penile erections. It has been suggested that the therapeutic efficacy of transcranial administration of AC pulsed electromagnetic fields (EMFs) in the picotesla flux density in PD involves the activation of dopamine D2 receptor sites which are the principal site of action of dopaminergic pharmacotherapy in PD. Here, 1 report 2 elderly male PD patients who experienced sexual dysfunction which was recalcitrant to treatment with anti Parkinsonian agents including selegiline, levodopa and tolcapone. However, brief transcranial administrations of AC pulsed EMFs in the picotesla flux density induced in these patients sexual arousal and spontaneous nocturnal erections. These findings support the notion that central activation of dopamine D2 receptor sites is associated with the therapeutic efficacy of AC pulsed EMFs in PD. In addition, since the right hemisphere is dominant for sexual activity, partly because of a dopaminergic bias of this hemisphere, these findings suggest that right hemispheric activation in response to administration of AC pulsed EMFs was associated in these patient with improved sexual functions.
Biological sensitivity and variability are key issues for risk assessment and standard setting. Variability encompasses general inter-individual variations in population responses, while sensitivity relates to unusual or extreme responses based on genetic, congenital, medical, or environmental conditions. For risk assessment and standard setting, these factors affect estimates of thresholds for effects and dose-response relationships and inform efforts to protect the more sensitive members of the population, not just the typical or average person. While issues of variability and sensitivity can be addressed by experimental and clinical studies of electromagnetic fields, investigators have paid little attention to these important issues. This paper provides examples that illustrate how default assumptions regarding variability can be incorporated into estimates of 60-Hz magnetic field exposures with no risk of cardiac stimulation and how population thresholds and variability of peripheral nerve stimulation responses at 60-Hz can be estimated from studies of pulsed gradient magnetic fields in magnetic resonance imaging studies. In the setting of standards for radiofrequency exposures, the International Commission for Non-Ionizing Radiation Protection uses inter-individual differences in thermal sensitivity as one of the considerations in the development of "safety factors." However, neither the range of sensitivity nor the sufficiency or excess of the 10-fold and the additional 5-fold safety factors have been assessed quantitatively. Data on the range of responses between median and sensitive individuals regarding heat stress and cognitive function should be evaluated to inform a reassessment of these safety factors and to identify data gaps.
BACKGROUND: Recent studies have described the promising method of electromagnetic navigated bronchoscopy (ENB) for diagnosis of peripheral solitary nodules. However, they require general anaesthesia or intravenous sedation. We wanted to know if ENB could be applied more easily in outpatients. OBJECTIVES: We prospectively evaluated the accuracy and the feasibility of ENB under local anaesthesia and nitrous oxide/oxygen inhalation as unique sedation in outpatients. METHODS: After mapping time, the bronchoscopic procedure was carried out under local anaesthesia and nitrous oxide/oxygen inhalation with the unique help of the ENB to confirm the right position of the extended working channel before sampling. The primary end point was the accuracy of ENB and the secondary end point was the feasibility in outpatients. RESULTS: Among 54 screened patients, 53 completed the study protocol. The overall diagnostic success rate to diagnose malignancy was 71.4% in tumours of 28 mm in median size. ENB classified correctly peripheral lesions according to malignity in 41 cases (30 cases of cancer, 11 benign diagnosis) and failed in 12 cases (1 probable lung metastasis, 11 lung cancers). All patients but 1 were dismissed 1 h after the procedure and the tolerance of the procedure was excellent in all cases except 2 (agitation and anxiety). In two cases (4%) a pneumothorax was recorded, 1 requiring drainage with a chest tube during a short hospitalisation. CONCLUSIONS: ENB under nitrous oxide/oxygen sedation seems to be an accurate and safe procedure. In our series, it allowed us to obtain the diagnosis in 71.4% of the tumours, with a good tolerance and an outpatient strategy.
In dental medicine, the study of mandibular movement has an important role in oral rehabilitation as it allows diagnosis of pathologies in the temporomandibular joint and the definition of adequate treatment plans. In this paper, a new device specially developed for the acquisition and analysis of 3D mandibular movement is presented. A facial arc is adopted as its main support structure and electromagnetic sensors are employed to acquire the mandibular movement. A neural network is used to transform the electrical signals output by the sensors into 3D Cartesian coordinates. A custom-made computer application is developed to display and analyse the movement acquired. The device is shown to be easy to use, comfortable for patients and capable of being produced at an affordable price.
Serpersu and Tsong (Sepersu, E. H., and Tsong, T. Y. (1983) J. Membr. Biol. 74, 191-201; (1984) J. Biol. Chem. 259, 7155-7162) reported activation of a K+ pumping mode of (Na,K)-ATPase by an oscillating electric field (20 V/cm, 1.0 kHz). Their attempts to activate Na+ pumping at the same frequency were unsuccessful. We report here activation of a Na+ pumping mode with an oscillating electric field of the same strength as used previously (20 V/cm) but at a much higher frequency (1.0 MHz). At 3.5 degrees C and the optimal amplitude and frequency, the field-induced, ouabain-sensitive (0.2 mM ouabain incubated for 30 min) Rb+ influx ranged between 10 and 20 amol/red blood cell/h, and the corresponding Na+ efflux ranged between 15 and 30 amol/red blood cell/h, varying with the source of the erythrocytes. No Rb+ efflux nor Na+ influx was stimulated by the applied field in the frequency range 1 Hz to 10 MHz. These results indicate that only those transport modes that require ATP splitting under the physiological condition were affected by the applied electric fields, although the field-stimulated Rb+ influx and Na+ efflux did not depend on the cellular ATP concentration in the range 5 to 800 microM. Computer simulation of a four-state enzyme electroconformationally coupled to an alternating electric field (Tsong, T. Y., and Astumian, R. D. (1986) Bioelectrochem. Bioenerg. 15, 457-476; Tsong, T. Y. (1990) Annu. Rev. Biophys. Biophys. Chem. 19, 83-106) reproduced the main features of the above results.
The worldwide proliferation of mobile phones raises the question of the effects of 900-MHz electromagnetic fields (EMF) on the brain. Using a head-only exposure device in the rat, we showed that a 15-min exposure to 900-MHz pulsed microwaves at a high brain-averaged power of 6 W/kg induced a strong glial reaction in the brain. This effect, which suggests neuronal damage, was particularly pronounced in the striatum. Moreover, we observed significant and immediate effects on the Kd and Bmax values of N-methyl-D-aspartate (NMDA) and GABA(A) receptors as well as on dopamine transporters. Decrease of the amount of NMDA receptors at the postsynaptic membrane is also reported. Although we showed that the rat general locomotor behavior was not significantly altered on the short term, our results provide the first evidence for rapid cellular and molecular alterations in the rat brain after an acute exposure to high power GSM (Global System for Mobile communication) 900-MHz microwaves.
The mechanism whereby low-frequency electromagnetic fields accelerate axonal regrowth and regeneration of peripheral nerve after crush lesion is not known. One candidate is an alteration in axonal transport. In this study we exposed unoperated rats for 15 min/day, and rats that had undergone a crush lesion of the sciatic nerve, for 1 hr/day for 2 days, to 2-Hz pulsed electromagnetic fields. To label fast transported proteins, [3H]-proline was microinjected into the spinal cord, and the sciatic nerves were removed 2, 3.5, and 5 hr later. The rates of fast axonal transport were obtained for animals in all groups by counting sequential 2-mm segments of nerves. The following transport rates were found: in unoperated normal sciatic nerve not exposed to PEMF, 373 +/- 14 mm/day; in unoperated normal nerve exposed to PEMF, 383 +/- 14 mm/day; in sham crush nerves not exposed to PEMF, 379 +/- 19 mm/day; in sham crush nerve exposed to PEMF, 385 +/- 17 mm/day; in crushed nerves not exposed to PEMF, 393 +/- 16 mm/day. and in crushed nerves exposed to PEMF, 392 +/- 15 mm/day. The results of these experiments indicate that 1) a crush injury to the sciatic nerve does not alter the rate of fast axonal transport, and 2) low-frequency pulsed electromagnetic fields do not alter fast axonal transport rates in operated (crush) or unoperated sciatic nerves.
The daily rhythm, the so-called biological clock or circadian rhythm, seems to be causally related to memory loss in the elderly and possibly also to Alzheimer's disease. This article argues that magnetic fields may improve memory performance in elderly patients by resetting the biological clock.
Disorganization of circadian rhythms, a hallmark of aging, may be related causally to the progressive deterioration of memory functions in senescence and possibly Alzheimer's disease (AD). In experimental animals, disruption of circadian rhythms produces retrograde amnesia by interfering with the circadian organization of memory processes. The circadian system is known to be synchronized to external 24 h periodicities of ambient light by a neural pathway extending from the retina to the suprachiasmatic nucleus (SCN) of the anterior hypothalamus. There is also evidence that the earth's magnetic field is a time cue ("Zeitgeber") of circadian organization and that shielding of the ambient magnetic field leads to disorganization of the circadian rhythms in humans. Since aging is associated with a delay of the circadian rhythm phase, and since light, which phase advances circadian rhythms, mimics the effects of magnetic fields on melatonin secretion, we postulate that application of magnetic fields might improve memory functions in the elderly as a result of resynchronization of the circadian rhythms. Moreover, since the circadian rhythm organization is more severely disrupted in patients with AD, it is possible that magnetic treatment might prove useful also in improving memory functions in these patients. If successful, application of magnetic fields might open new avenues in the management of memory disturbances in the elderly and possibly in AD.
Chronic alcoholics were selected from hospitals and A.A. Centres and subjected to different methods of treatment namely, psycho therapy, stereotaxic surgery, nonvolitional biofeedback, Yoga and meditation and extremely low frequency Pulsed Magnetic Field. Each group comprised a minimum of 20 subjects. All were males between the ages of 20 and 45 years. Investigations done were clinical, psychological, biochemical, neurochemical and electrophysiological. Improvement was noticed in all the patients, the degree varying with the different methods of treatment. The patients were followed up at least for a period of one year.
It is well known that electromagnetic fields cause mechanical forces. If one applies an electrical field to a suspension of microscopic particles, these particles realign themselves along the direction of the field and form pearl-chain-like aggregates. These chains are mostly single stranded but they are frequently multistranded. This phenomenon has been investigated by a number of groups. Here we discuss the dependence of threshold field strength on particle size and frequency. Also, pulsed fields have been thought to be more effective than continuous fields of the same average power in evoking biological effects. Our measurement of the threshold power requirement for the pearl-chain formation indicates that pulsed fields require as much power as continuous fields. The biological significance of pearl-chain formation is briefly discussed.
An experimental study was carried out in rabbits to investigate the effects of exposing rabbits to low-intensity pulsed magnetic fields (PMFs) on alimentary hyperlipemia. Thirty female white big ear rabbits were randomly divided into three groups. The normal group was fed with a standard chow diet and the other two groups (hyperlipid and magnetic) were fed with the chow diet supplemented with cholesterol, yolk powder and lard. The magnetic group was exposed to 15 Hz pulsed magnetic fields. After 8 weeks, levels of blood lipid and indices of hemorheology were examined. In addition, histomorphologic changes of hepatic and myocardial tissues were compared across the groups respectively. Compared with the hyperlipid group, hemorheology indices of the magnetic group reduced significantly from 12.80% to 38.05% (P < 0.01) indicating lower blood viscosity. Similarly, compared with the hyperlipid group, the levels of total cholesterol and triglycerides in the magnetic group decreased 40.52% and 52.42% (P < 0.01). On the contrary, high density lipoprotein (HDL) value obviously increased 66.67% (P < 0.01). Furthermore, compared with the control group, the values of triglycerides and HDL of the magnetic group did not show statistical differences (P > 0.05). The deposit of fatty material on the inner lining of thoracic aorta wall of the magnetic group was significantly lighter than that of the hyperlipid group. Numerous aggregation of lipoids emerged among myocardial myofibrils in the hyperlipid group, while no notable change was found in both the magnetic and control group. The results indicate that low-intensity PMFs could be helpful for the treatment of alimentary hyperlipemia.
This study investigated the effects of electromagnetic fields on enzymes involved in purine metabolism in human peripheral blood mononuclear cells in vitro. Cells were obtained from 20 volunteers. We tested both low-energy, extremely low frequency (ELF; 100-Hz) electromagnetic fields and the Therapeutic Application of Musically Modulated Electromagnetic Fields (TAMMEFs); the latter is characterized by variable frequencies, intensities, and wave shapes. Adenylate kinase activity was increased after ELF field exposure but decreased slightly after TAMMEF exposure. Neither of the two electromagnetic field affected the activities of the purine metabolism enzymes ecto-5'-nucleotidase, adenosine deaminase, and adenosine kinase. We concluded that ELF fields may influence cellular electrical charge stability; stimulation of adenylate kinase activity could restore the cell to a state of equilibrium. In contrast, TAMMEF fields may be useful for maintaining and regulating the cellular electrical charge.
By using a FURA2 ratio imaging method, the intracellular free calcium concentration was investigated in cultured mice neuroblastoma cells under the influence of an amplitude-modulated (AM) field (5 kHz sine wave AM 16 Hz sinusoidal 800 V/m and 80 V/m), as well as of electric field pulses (300-ms unipolar pulses of 1000 V/m and 800 V/m, 5 pulses during 10 s and 50 pulses during 100 s). An increase in free intracellular calcium was found in about 50% of cells after field application, whereas in control experiments only about 20% of the cells showed similar increases. However, this effect depended on the amount of UV irradiation used for excitation of FURA2 fluorescence. Experiments with 1/30 to former total illumination no longer demonstrated an increase in control cells or in cells treated with AM fields. The number of cells showing calcium increase after the application of pulsed fields was reduced significantly. Therefore, the UV light itself, applied as double flashes for the fluorescence measurement, activates the cellular calcium regulation. These findings offer a possible explanation for the low reproducibility of field effects found in different laboratories, in which investigations were performed with different equipment using different intensities of UV excitation.
Impairments in visual memory and visuoconstructive functions commonly occur in patients with Alzheimer's disease (AD). Recently, I reported that external application of electromagnetic fields (EMF) of extremely low intensity (in the picotesla range) and of low frequency (in the range of 5Hz-8Hz) improved visual memory and visuoperceptive functions in patients with Parkinson's disease. Since a subgroup of Parkinsonian patients, specifically those with dementia, have coexisting pathological and clinical features of AD, I investigated in two AD patients the effects of these extremely weak EMF on visual memory and visuoconstructive performance. The Rey-Osterrieth Complex Figure Test as well as sequential drawings from memory of a house, a bicycle, and a man were employed to evaluate the effects of EMF on visual memory and visuoconstructive functions, respectively. In both patients treatment with EMF resulted in a dramatic improvement in visual memory and enhancement of visuoconstructive performance which was associated clinically with improvement in other cognitive functions such as short term memory, calculations, spatial orientation, judgement and reasoning as well as level of energy, social interactions, and mood. The report demonstrates, for the first time, that specific cognitive symptoms of AD are improved by treatment with EMF of a specific intensity and frequency. The rapid improvement in cognitive functions in response to EMF suggests that some of the mental deficits of AD are reversible being caused by a functional (i.e., synaptic transmission) rather than a structural (i.e., neuritic plaques) disruption of neuronal communication in the central nervous system.
The author describes two Alzheimer's patients who show a definite improvement after treatment with magnetic field therapy, especially in the area of visual memory, but also in their drawing abilities. There were also improvements in other cognitive functions, including the ability of these patients to orient themselves in space, their mental/emotional condition, ability to make social contact, and short-term memory.
The influence of low repetition rate pulsed magnetic fields (LRMF) on the evoked potential (population spike) recorded from mouse hippocampal slices was investigated. LRMF were applied according to two protocols. In protocol A, LRMF applied with a constant strength (15 mT) and frequency ranging from 0.03 to 0.5 Hz resulted in an amplification of the potential. Although the frequency of 0.16 Hz was the most effective, enhancing the population spike by over 280%, it also caused an increase in spontaneous activity, seizures, and cessation of neuronal activity in 50% of the slices. In protocol B, LRMF were applied with a variable intensity (9-15 mT) and in cycles of different duration ranging from 5 to 20 min. While an increase in the amplitude of the population spike was observed in all slices exposed to LRMF applied according to protocol B, the longest exposure was the most effective. Neither seizures nor an increase in the spontaneous activity were observed in this group of the slices. These results support and extend our previous data and characterize further the relation between the pattern of applied magnetic fields and their influence on the nervous system.
The exposure of cells to relatively low-intensity, pulsed, low-frequency electromagnetic fields can result in a transient augmentation of mRNA synthesis. Under certain conditions of irradiation, the augmentation is a function of the strength of the electromagnetic field. A linear, multi-step, chemical-reaction model accounts for many of the principal features that are observed in both the time- and intensity-dependent variations of transcriptional effects. The crucial assumption in the model is that the direct effect of electromagnetic fields on exposed cells is an increase in the rate constant that characterizes one of the intermediate sequential reactions in the synthesis of mRNA.
Eddy currents, which are induced in the magnet cryostat by pulsed magnetic field gradients in MRI, generate undesired eddy fields within the imaging volume. In this work, an automated and computerized algorithm to compensate these eddy currents is presented. The compensation is done in two steps: (i) Eddy fields are symmetrized electronically with an R-C filter. (ii) The symmetric eddy fields are compensated by another R-C filter. The compensation algorithm is iterative; therefore, errors that remain from one iteration are eliminated in the next iteration. Hence, the compensation process is very robust and accurate. It is shown that all the even harmonics of the eddy fields are eliminated by the symmetrization process, but the odd field harmonics remain. The amplitude of these odd harmonics can be significantly reduced if the gradient coils are designed so that the field they generate is spatially similar to the eddy fields.
The effects of rapidly changing magnetic fields on the cardiac and respiratory functions of anaesthetised rabbits have been investigated. No changes were observed using pulsed fields with peak rates of change of 60 T/sec. The implications of these experiments for the safety of NMR imaging are discussed.
This paper evaluates a low-frequency FDTD method applied to the problem of induced E-fields/eddy currents in the human body resulting from the pulsed magnetic field gradients in MRI. In this algorithm, a distributed equivalent magnetic current (DEMC) is proposed as the electromagnetic source and is obtained by quasistatic calculation of the empty coil's vector potential or measurements therein. This technique circumvents the discretizing of complicated gradient coil geometries into a mesh of Yee cells, and thereby enables any type of gradient coil modeling or other complex low frequency sources. The proposed method has been verified against an example with an analytical solution. Results are presented showing the spatial distribution of gradient-induced electric fields in a multilayered spherical phantom model and a complete body model.
Shortwave and microwave diathermy equipment use by physiotherapy departments in Grampian Region has been studied. Stray electric and magnetic fields close to equipment have been measured and compared with exposure levels recommended by the INIRC and the NRPB. Fields above the recommended whole body levels extend to 0.5-1.0 m from the electrodes and cables for continuous wave (cw) shortwave equipment, and up to 0.5 m for microwave units and pulsed shortwave models. Operators were exposed to local fields above these values for 2 - 3 min during cw shortwave treatments, but rarely exceeded the recommended exposure. However, short localised exposures to high fields, which can occur if the operator moves close to the electrodes or cables, could exceed these limits. Physiotherapists are advised to remain at a distance of at least 1 m during cw treatments, and not to approach within 0.5 m of the electrodes and cables even for a short period.
Stray electric and magnetic fields have been measured near to therapeutic and surgical diathermy equipment for many different treatments. The highest field strengths are associated with continuous wave (cw) 27 MHz therapeutic diathermy equipment for which fields above national reference levels extend for 1 m from the electrodes and cables. The extent of the fields does not vary substantially with the type of treatment being performed. Recommendations that operators remain 1.0 m from cw therapeutic diathermy equipment, 0.5-0.8 m from pulsed treatments with capacitive electrodes and 0.2 m from pulsed inductive applicators can be applied to restrict exposure for any treatment with each type of unit. In a proposed European Community (EC) directive, action levels similar in magnitude to the reference levels are used to trigger requirements for assessments of hazard, measures to reduce exposure and personnel training. Assessments and appropriate recommendations of measures to reduce exposure can be linked to the type of equipment. Fields associated with electrosurgical units operating at frequencies of 0.3-0.5 MHz only approached reference levels within 20-30 cm of the cables, and because of the relatively short durations of the emissions, precautions were considered unnecessary with the units tested.
Short-wave diathermy (SWD), a form of radiofrequency radiation used therapeutically by physiotherapists, may be applied in continuous (CSWD) or pulsed (PSWD) mode using either capacitive or inductive methods. Stray radiation emitted by these units may exceed exposure guidelines close to the equipment. Discrepant guidelines exist on a safe distance from an operating unit for operators and other personnel. Stray electric (E-field) and magnetic (H-field) field strengths from 10 SWD units in six departments were examined using a PMM 8053 meter and two isotropic probes (EP-330, HP-032). A 5 l saline phantom completed the patient circuit. Measurements were recorded in eight directions between 0.5 m and 2 m at hip and eye levels while the units operated at maximum output and data compared to current guidelines. Results found stray fields from capacitive CSWD fell below operator limits at 2 m (E-field 4.8-39.8 V/m; H-field 0.015-0.072 A/m) and at 1 m for inductive CSWD (E-field 0-36 V/m; H-field 0.01-0.065 A/m). Capacitive PSWD fields fell below the limits at 1.5 m (E-field 1.2-19.9 V/m; H-field 0.002-0.045 A/m) and at 1m for inductive PSWD (E-field 0.74.0 V/m; H-field 0.009-0.03 A/m). An extra 0.5 m was required before fields fell below the guidelines for other personnel. These results demonstrate, under a worst case scenario, emissions from SWD exceed the guidelines for operators at distances currently recommended as safe. Future guidelines should include recommendations for personnel other than physiotherapists.
This study investigates the effects of a pulsed electromagnetic field (PEMF) (Diapulse) on experimentally divided and sutured common peroneal nerves in rats. Evidence is presented to show that PEMF accelerates recovery of use of the injured limb and enhances regeneration of damaged nerves.
The use of mobile phones is increasing, which also increases the population's exposure to global system of mobile communications (GSM) signals. Questions of safety and possible biological effects are of concern and to date, remain largely unanswered. In order to examine possible biological effects of a GSM-like signal at a cellular level, we exposed two human cell lines (one of neuronal (SK-N-SH) and the other of monocytoid (U937) origin) to a 900 MHz RF signal, pulsed at 217 Hz, producing a specific absorption rate (SAR) of 0.2 W/kg. Putative effects were assessed by comparing radiofrequency-exposed cells to sham-exposed cells using a variety of assay techniques. For the cell line SK-N-SH, effects were specifically assessed by gene microarray, followed by real-time PCR of the genes of interest, Western blot analysis was used to measure heat shock protein levels, and flow cytometry to measure cell cycle distributions and apoptosis. Effects of radiofrequency on the cell line U937 were assessed by cell viability and cell cycle analysis. From our study of these two cell lines, we found no significant difference between sham-exposed versus radiofrequency-exposed cells in any of the assays or conditions examined.
Our previous studies revealed that magnetic fields amplified evoked potentials recorded from mouse hippocampal slices. In search for the mechanism of this effect, we evaluated the concentration of cAMP in slices exposed to low-frequency and pulsed magnetic fields. Low-frequency magnetic fields of 15 mT applied at 0.16 Hz for 30 min enhanced the concentration of cAMP almost three-fold. The concentration of cAMP continued to rise through the first hour after turning magnetic fields off, reaching almost a four-fold increase, and then returned to control levels at the end of the second hour. Neither static magnetic fields nor magnetic fields applied with the frequency of 0.5 Hz had any effect on cAMP concentration. The increase in cAMP levels was dependent on the strength of the magnetic field and required the presence of extracellular calcium. A pulsed magnetic field applied with variable intensity (9-15 mT) and in cycles lasting from 5 to 20 min doubled the cAMP concentration. These results support our previous electrophysiological observations and provide biochemical correlates for their interpretation.
Pulsed magnetic fields have been used to enhance healing of bone fractures and purportedly of lesions in soft tissue. However, their mechanism of action is poorly understood. We report changes in the plasma membrane of a nonadherent mammalian cell line, U937, which was exposed to a 25-pps magnetic field for 48 hours. Aqueous polymer two-phase partition studies showed that magnetic-field-exposed cells exhibited an increased negative surface charge but membrane hydrophobicity was not significantly altered. The observed increase in membrane electronegativity of exposed cells did not reflect a significant change in growth rate.
We present an open volume, high isolation, RF system suitable for pulsed NMR and EPR spectrometers with reduced dead time. It comprises a set of three RF surface coils disposed with mutually parallel RF fields and a double-channel receiver (RX). Theoretical and experimental results obtained with a prototype operating at about 100 MHz are reported. Each surface RF coil (diameter 5.5 cm) was tuned to f0=100.00+/-0.01 MHz when isolated. Because of the mutual coupling and the geometry of the RF coils, only two resonances at f1=97.94 MHz and f2=101.85 MHz were observed. We show they are associated with two different RF field spatial distributions. In continuous mode (CW) operation the isolation between the TX coil and one of the RX coils (single-channel) was about -10 dB. By setting the double-channel RF assembly in subtraction mode the isolation values at f1 or f2 could be optimised to about -75 dB. Following a TX RF pulse (5 micros duration) an exponential decay with time constant of about 600 ns was observed. The isolation with single-channel RX coil was about -11 dB and it increased to about -47 dB with the double-channel RX in subtraction mode. Similar results were obtained with the RF pulse frequency selected to f2 and also with shorter (500 ns) RF pulses. The above geometrical parameters and operating frequency of the RF assembly were selected as a model for potential applications in solid state NMR and in free radical EPR spectroscopy and imaging.
Diverse studies have shown that magnetic fields can affect behavioral and physiological functions. Previously, we have shown that sinusoidal extremely low frequency magnetic fields and specific pulsed magnetic fields (Cnps) can produce alterations in the analgesia-related behavior of the land snail. Here, we have extended these studies to show an induction of analgesia in mice equivalent to a moderate dose of morphine (5 mg/kg), and the effect of both Cnp exposure and morphine injection on some open-field activity. Cnp exposure was found to prolong the response latency to a nociceptive thermal stimulus (hot plate). Cnp+morphine offset the increased movement activity found with morphine alone. These results suggest that pulsed magnetic fields can induce analgesic behavior in mice without the side effects often associated with opiates like morphine.
There are concerns about workers repeatedly exposed to magnetic fields exceeding regulatory limits with respect to modern magnetic resonance imaging (MRI). As a result, there is need for an ambulatory magnetic field dosimeter capable of measuring these fields in and around an MRI scanner in order to evaluate the regulatory guidelines and determine any underlying exposure risks. This study presents results of tri-axial measurements using an ambulatory magnetic field dosimeter worn by workers during normal working shifts. We recorded and analyzed magnetic field exposures in and around 1.5 T, 2 T, and 4 T magnets during routine patient procedures. The data was integrated and averaged over time and evaluated against the latest exposure standards. Time-varying magnetic fields occur when individuals move through spatially non-uniform static magnetic fields or during gradient-pulsed magnetic fields or a combination of both. Our previous numerical analysis shows that at certain positions surrounding the MRI scanner ends, such fields may induce current densities and electric fields that may exceed the relevant EU, ICNIRP, and IEEE standards. A high-speed acquisition version of the dosimeter measured gradient- pulsed fields at positions accessible by MRI workers near the scanner ends, and the results were evaluated and compared against the numerical simulations and the standards. Our measurements confirm that workers can be exposed to magnetic fields exceeding the guidelines at positions near the gradient coil ends during clinical imaging and a high degree of correlation exists with the numerical results. While the time-weighted average magnetic field exposures in 1.5 T, 2 T, and 4 T were all within the regulatory limits during static magnetic field measurements, the peak limits for the head can be exceeded in some circumstances. This study presents a small number of routine shifts of data that provide indicative results of magnetic field exposure in real situations.
Transcranial magnetic stimulation (TMS) is a non-invasive technique that uses the principle of electromagnetic induction to generate currents in the brain via pulsed magnetic fields. Although there are some researches about electric field and current density distribution induced by TMS on human brain, similar analyses on other species are rarely known. TMS is often used on rat models before used on human being, then how TMS affects the rat brain is critical information for researchers. In this paper, a real rat head model during transcranial magnetic stimulation is presented. 3D-reconstruction method and finite element method are carried out to calculate the spatial distribution of the electric field. This model is quite useful to design TMS experiments on rats and interpret these results.
We report on a numerical analysis method for diffractive optical elements that consist of features ranging from subwavelength to more than 10lambda. The essence of the method is treating local structures of the optical elements as diffraction gratings. It is shown that the method can provide accuracy of results comparable with fully electromagnetic treatments in much shorter time. The theory and results are explained assuming micro-Fresnel lenses with one-dimensional structures for investigating polarization properties.
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