iMRS 2000 - PEMF Publications
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PEMF Publications

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401

Electrokinetic lithotripsy: safety, efficacy and limitations of a new form of ballistic lithotripsy

OBJECTIVE: To investigate the safety and efficacy of electrokinetic lithotripsy (EKL), a ballistic lithotripter which uses high-energy magnetic fields to propel an impactor to fragment calculi. PATIENTS AND METHODS: The records and radiographs of 121 patients who underwent ureteroscopy using the EKL for stones in the upper (26), mid (28) or lower (67) ureter were reviewed retrospectively. Ureteroscopy was performed with an 8.5 F semi-rigid ureteroscope, through which a 3 F EKL probe was passed. RESULTS: A total of 148 stones (mean stone size 11.5 mm, range 6-40) in 121 patients were treated using the EKL. One patient was lost to follow-up. Of 148 stones, 147 (99.3%) were fragmented, including five that had resisted fragmentation with either pulsed-dye laser or electrohydraulic lithotripsy. Despite this, only 45 of 56 patients (80%) with a single stone in the lower ureter were rendered stone-free after a single ureteroscopic procedure. Seven patients in this group (12%) required shock-wave lithotripsy for fragments that had been propelled into the kidney, while four patients (7%) required repeat ureteroscopy for retained ureteric fragments. Complications were limited to minor ureteric perforations in two patients, both of which were treated with a stent. CONCLUSION: EKL is an inexpensive and reliable endoscopic method which fragments nearly all urinary calculi. Its limitations include the propulsion of fragments and the need to use an offset, semi-rigid ureteroscope. We recommend the use of a basket or graspers to remove fragments of >/=4 mm after EKL.

402

Electromagnetic and thermal analysis for lipid bilayer membranes exposed to RF fields

Experiments with pulsed radio frequency fields have shown influence on the low-frequency behavior of lipid bilayer membranes. In this paper, we present an electromagnetic and thermal analysis of the used exposure device to clarify whether the observed effects have a thermal cause and to determine the fields at the lipid bilayer. In order to model the very thin lipid bilayer (about 5 nm) accurately, the electromagnetic analysis is broken into several steps employing the finite difference time domain technique and a finite element/boundary element hybrid approach. Based on the obtained power loss due to the electromagnetic fields, the temperature change is calculated using the finite element method for the solution of the heat conduction equation. Both, the electromagnetic and the thermal analysis are performed for a variety of material parameters of the exposure device. The electromagnetic analysis shows that the exposure device is capable of producing voltages on the order of 1 mV across the lipid bilayer. The combined electromagnetic and thermal calculations reveal that the temperature oscillations due to the pulsed radio frequency fields are too small to directly influence the low-frequency behavior of the lipid bilayer.

403

Electromagnetic and thermal evaluation of an applicator specialized to permit high-resolution non-perturbing optical evaluation of cells being irradiated in the W-band

To permit epi-illuminated, high-resolution optical microscopy of cells in monolayer culture during unperturbed W-band (75-110 GHz) irradiation, a new class of applicator has been developed based upon WR10 rectangular waveguide components: the cells are normally plated onto the underside of a coverslip which is then placed against the under side of a waveguide flange and receives a roughly circular exposure pattern, with the +/-1 dB central spot roughly 1 mm in diameter. Constructed and tested with 94 GHz millimeter waves, water-immersion optics, and free-convection cooling, the applicator works robustly and permits SARs at the cell layer as high as 4500 W/kg before the steady-state temperature rise at the cell layer exceeds 0.5 K. Bioelectromagnetics, 2009 (c) 2009 Wiley-Liss, Inc.

404

Electromagnetic augmentation of antibiotic efficacy in infection of orthopaedic implants

Infection of orthopaedic implants is a significant problem, with increased antibiotic resistance of adherent 'biofilm' bacteria causing difficulties in treatment. We have investigated the in vitro effect of a pulsed electromagnetic field (PEMF) on the efficacy of antibiotics in the treatment of infection of implants. Five-day biofilms of Staphylococcus epidermidis were grown on the tips of stainless-steel pegs.They were exposed for 12 hours to varying concentrations of gentamicin or vancomycin in microtitre trays at 37 degrees C and 5% CO2. The test group were exposed to a PEMF. The control tray was not exposed to a PEMF. After exposure to antibiotic the pegs were incubated overnight, before standard plating onto blood agar for colony counting. Exposure to a PEMF increased the effectiveness of gentamicin against the five-day biofilms of Staphylococcus epidermidis. In three of five experiments there was reduction of at least 50% in the minimum biofilm inhibitory concentration. In a fourth experiment there was a two-log difference in colony count at 160 mg/l of gentamicin. Analysis of variance (ANOVA) confirmed an effect by a PEMF on the efficacy of gentamicin which was significant at p < 0.05. There was no significant effect with vancomycin.

405

Electromagnetic field (EMF) effects on channel activity of nanopore OmpF protein

In this study, the effects of nonionizing electromagnetic fields (EMF; 925 MHz) on the OmpF porin channel have been characterized at the single-channel level. Channel activity was recorded in real time by the voltage clamp method. Our results showed an increase in the frequency of channel gating and voltage sensitivity. The effects of EMF lasted for several milliseconds after the field source was terminated. However, the conductance levels of channels did not change significantly. Thermal effects of EMF on single-channel properties are a possible cause, based on theoretical evaluation of results that were comparable to those seen in conventional experiments at different temperatures. We conclude that EMF affects both the dynamics and conformation of the channel, either directly by affecting critical amino acid side-chain arrangement, or indirectly, via the electrolyte or the lipid membrane.

406

Electromagnetic field at 15.95-16 Hz is cardio protective following acute myocardial infarction

Previous studies have shown that pre-exposure of the heart to weak magnetic field reduces infarct size shortly after induction of myocardial ischemia. To investigate the role of AC magnetic field with a frequency of 15.95-16 Hz and 80 mT on left ventricular (LV) remodeling following chronic coronary occlusion and a short episode of ischemia followed by reperfusion (I/R). LV dimension and function were measured using echocardiography. Femur bone marrow was isolated and cells were phenotyped for endothelial linage and immuno stained for endothelial cells. The area at risk was measured using triphenyltetrazolium chloride staining. A significant reduction of 27% in shortening fraction (SF) was measured following acute myocardial infarction (AMI) compared with a 7% decrease in animals exposed to magnetic field (p < 0.04). A significantly higher number of colony forming units and endothelial progenitor cells were counted within the treated groups subjected to magnetic field (p < 0.02). Exposing the heart to magnetic field prior to reperfusion did not show any preservation either on SF or on infarct size. Magnetic field was protective in the AMI but not in the I/R model. The mechanisms underlying cardiac protection induced by AC magnetic field following chronic injury deserves further investigation.

407

Electromagnetic field effect on separation of nucleotide sequences and unwinding of a double helix during DNA replication

Our previous pre-clinic experimental results have showed that the bacterium infection can be suppressed and the epithelialization can be enhanced by the externally applied rectangular pulsed electrical current stimulation (RPECS). The results are clinically significant for patients, especially for those difficult patients whose skin wounds need long periods to heal. However, the results also raise questions: How does the RPECS accelerate the epithelium cell proliferation? What is the relationship among the bacterium infection, the epithelialization and the RPECS? To answer these questions, we have previously modeled mitosis and cytokinesis mechanisms for animal cells and amitosis for bacteria at a cellular level and in a view of physics. In this paper, we model the separation of nucleotide sequences and the unwinding of a double helix during DNA replication at a molecular level and also in wild types of cells. Firstly, we define a new concept of nucleotide (NT) electromagnetic field (EMF) box (sequence) which carries genetic information: The continuous NT EMF boxes compose a nucleotide strand. Then, we hypothesize the symmetry, repulsion and attraction of NT EMF boxes: If a pair of NT EMF boxes are (quasi) mirror or complementary symmetric about a plane (curve) or point, they repulse or attract from each other because there is a repulsive or attractive EMF force between them. Our models suggest, the repulsive EMF force from children DNA strands simultaneously separates the children DNA strands, splits the hydrogen bonds of parental base pairs, and unwinds the parental double helix while DNA polymerases are synchronously synthesizing the new children DNA strands. To understand the mechanism of epithelialization enhanced with the externally applied RPECS at a molecular level, we hypothesize that the normal separation of nucleotide sequences and unwinding of a double helix during DNA replication could be suppressed in the bacteria but not in the epithelium cells because: (a) the spontaneous EMF in the epithelium could be 1000 times stronger than that in bacteria; (b) the epithelium cells have one more non-conducting envelope (nuclear membrane) to protect the normal separation and unwinding; (c) based on our previous experimental data, the RPECS amount received by the bacteria are three times as much as the amount the epithelium cells receive. Therefore, the epithelium cellular proliferation may be directly, as well as indirectly (e.g., somatic reflex) accelerated by the RPECS.

408

Electromagnetic field induced changes in lipid second messengers

Initial studies with a human hematopoietic cell line, TF-1, suggest multifarious effects of electromagnetic fields on lipid signal transduction. We have examined the effects of pulsed magnetic fields (2 T, 84 microseconds zero-to-peak haversine, 91 V/m induced electric field) on the cell cycle by flow cytometry. A 31% increase of cells in the G1 phase occurred concurrently with a 35% decrease of cells in S-phase, which suggests that doses of 30 or 40 pulses have an anti-proliferative effect. Changes in the lipid second messengers, diacylglycerol (DAG) and phosphatidic acid (PA) with stimuli of 2 T intensity were also dependent on the number of pulses. DAG production doubled with 30 pulses and tripled with 40 pulses, and PA levels were reduced to one third and one tenth of the original levels. Phospholipase D (PLD) up-regulation was assessed directly by the capacity of PLD to catalyze transphosphatidylation in the presence of alcohol. [3H]Phosphatidylethanol formed rapidly and continued to increase with concomitant decreases in [3H]PA and parallel generation of [3H]DAG. Propranolol, an inhibitor of PA phosphohydrolase, inhibited the formation of DAG in a dose-dependent manner with a marked increase in PA production. Examination of the kinetics of formation of [3H]choline and [3H]phosphocholine at different times after stimulation showed a rapid and consistent increase in [3H]choline, whereas [3H]phosphocholine increase was evident only 60 min after stimulation. Magnetic exposure also caused a shift in some molecular species patterns of DAG and PA which could be correlated with phosphatidylinositol, phosphatidylethanolamine and phosphatidylcholine molecular species decreases. Therefore, we propose that the PC-PLC pathway may be temporarily inactivated for a short period of time by exposure to pulsed stimuli, and the PC-PLD pathway is up-regulated based on: (1) cellular release of [3H]choline; (2) rapid intracellular formation of [3H]PA followed by [3H]DAG; (3)active transphosphatidylation; and (4) blockade of DAG formation by propranolol.

409

Electromagnetic field interacting with a semi-infinite plasma

Plasmon and polariton modes are derived for an ideal semi-infinite (half-space) plasma by using a general, unifying procedure based on the equation of motion of the polarization and the electromagnetic potentials. Known results are reproduced in a much more direct manner, and new ones are derived. The approach consists of representing the charge disturbances by a displacement field in the positions of the moving particles (electrons). The propagation of an electromagnetic wave in this plasma is treated by using the retarded electromagnetic potentials. The resulting integral equations are solved, and the reflected and refracted fields are computed, as well as the reflection coefficient. Generalized Fresnel relations are thereby obtained for any incidence angle and polarization. Bulk and surface plasmon-polariton modes are identified. As is well known, the field inside the plasma is either damped (evanescent) or propagating (transparency regime), and the reflection coefficient exhibits an abrupt enhancement on passing from the propagating regime to the damped one (total reflection).

410

Electromagnetic field quantization in time-dependent linear media

We present a quantization scheme for the electromagnetic field in time-dependent homogeneous nondispersive conducting and nonconducting linear media without sources. Using the Coulomb gauge, we demonstrate this quantization can be mapped into a damped (attenuated) time-dependent quantum harmonic oscillator. Remarkably, we find that the time dependence of the permittivity, for epsilon>0, gives rise to an attenuation of the radiation field. Afterwards, we obtain the exact wave functions for this problem and consider an exponential time accretion of the permittivity as a particular case.

411

Electromagnetic field strength levels surrounding electronic article surveillance (EAS) systems

Electronic article surveillance (EAS) is used in many applications throughout the world to prevent theft. EAS systems produce electromagnetic (EM) energy around exits to create an EM interrogation zone through which protected items must pass before leaving the establishment. Specially designed EAS tags are attached to these items and must either be deactivated or removed prior to passing through the EAS EM interrogation zone to prevent the alarm from sounding. Recent reports in the scientific literature have noted the possibility that EM energy transmitted by EAS systems may interfere with the proper operation of sensitive electronic medical devices. The Food and Drug Administration has the regulatory responsibility to ensure the safety and effectiveness of medical devices. Because of the possibility of electromagnetic interference (EMI) between EAS systems and electronic medical devices, in situ measurements of the electric and magnetic fields were made around various types of EAS systems. Field strength levels were measured around four types of EAS systems: audio frequency magnetic, pulsed magnetic resonant, radio frequency, and microwave. Field strengths from these EAS systems varied with magnetic fields as high as 1073.6 Am(-1) (in close proximity to the audio frequency magnetic EAS system towers), and electric fields up to 23.8 Vm(-1) (in close proximity to the microwave EAS system towers). Medical devices are only required to withstand 3 Vm(-1) by the International Electrotechnical Commission's current medical device standards. The modulation scheme of the signal transmitted by some types of EAS systems (especially the pulsed magnetic resonant) has been shown to be more likely to cause EMI with electronic medical devices. This study complements other work in the field by attaching specific characteristics to EAS transmitted EM energy. The quantitative data could be used to relate medical device EMI with specific field strength levels and signal waveforms. This is one of several efforts being made by the FDA, the electronic medical device industry and the EAS industry to mitigate the potential for EMI between EAS and medical devices.

412

Electromagnetic Field Treatment Protects Against and Reverses Cognitive Impairment in Alzheimer's Disease Mice

Despite numerous studies, there is no definitive evidence that high-frequency electromagnetic field (EMF) exposure is a risk to human health. To the contrary, this report presents the first evidence that long-term EMF exposure directly associated with cell phone use (918 MHz; 250 mW/kg) provides cognitive benefits. Both cognitive-protective and cognitive-enhancing effects of EMF exposure were discovered for both normal mice and transgenic mice destined to develop Alzheimer's-like cognitive impairment. The cognitive interference task utilized in this study was designed from, and measure-for-measure analogous to, a human cognitive interference task. In Alzheimer's disease mice, long-term EMF exposure reduced brain amyloid-beta (Abeta) deposition through Abeta anti-aggregation actions and increased brain temperature during exposure periods. Several inter-related mechanisms of EMF action are proposed, including increased Abeta clearance from the brains of Alzheimer's disease mice, increased neuronal activity, and increased cerebral blood flow. Although caution should be taken in extrapolating these mouse studies to humans, we conclude that EMF exposure may represent a non-invasive, non-pharmacologic therapeutic against Alzheimer's disease and an effective memory-enhancing approach in general.

413

Electromagnetic fields and epidemiology: an overview inspired by the fourth course at the International School of Bioelectromagnetics

The fourth course at the International School of Bioelectromagnetics addressed various aspects of the epidemiology of exposure to electromagnetic fields (EMF). In this overview, inspired by the lectures and the discussions among participants, we summarize current knowledge on exposure to EMF and disease risk, with emphasis on studies of use of mobile phones and brain tumours and exposure to power lines and childhood leukaemia. Sources of bias and error hamper straightforward conclusions in some areas and, in order to move forward, improvements in study design and exposure assessment are necessary. The scientific evidence available to date on possible long-term effects from exposure to ELF and RF fields is not strong enough to revise current protection limits based on the known acute effects of such exposures. Precautionary measures may be considered to reduce ELF exposure of children or exposure to RF during mobile phone use, keeping in mind that it is unclear whether they involve any preventive benefit. Possible health effects from mobile phone use in adults and in children should be investigated further by prospective epidemiological studies with improved exposure assessment and brain tumour incidence rates should be monitored. Further studies on the relation between childhood leukaemia and ELF magnetic fields would be worthwhile if they focus on heavily exposed groups and attempt to minimize possible selection bias. In conclusion, epidemiological studies conducted with appropriate diligence can play a key role in finding the answers.

414

Electromagnetic fields and magnets. Investigational treatment for musculoskeletal disorders

Certain pulsed electromagnetic fields (PEMF) affect the growth of bone and cartilage in vitro, with potential application as an arthritis treatment. PEMF stimulation is already a proven remedy for delayed fractures, with potential clinical application for osteoarthritis, osteonecrosis of bone, osteoporosis, and wound healing. Static magnets may provide temporary pain relief under certain circumstances. In both cases, the available data is limited. The mechanisms underlying the use of PEMF and magnets are discussed.

415

Electromagnetic fields and melatonin production

The pineal gland, which in humans is located near the anatomical center of the brain, is normally responsive to visible electromagnetic fields (ie light) since the eyes are functionally connected to the pineal gland by a series of neurons. Normally, the pineal gland produces low amounts of melatonin during the day and high amounts at night; this rhythm is reflected in the blood melatonin concentrations which are higher at night than during the day. In both man and lower mammals, their exposure to light at night is followed by a drop in pineal melatonin production and blood melatonin levels. Likewise, exposure of non-human mammals to sinusoidal electric and/or magnetic fields as well as pulsed static magnetic fields often reduces pineal melatonin production. Melatonin has many functions in the organism and any perturbation (not only electromagnetic fields) which causes levels of melatonin to be lower than normal may have significant physiological consequences. Melatonin, because it is a potent antioxidant, may provide significant protection against cancer initiation as well as promotion. However, it is premature to conclude that the alleged increased cancer risk reported in individuals living in higher than normal electromagnetic environments relate to reduced melatonin levels caused by such field exposures.

416

Electromagnetic fields for bone healing

Electrical stimulation has been applied in a number of different ways to influence tissue healing. Most of the early work was carried out by orthopedic surgeons looking for new ways of enhancing fracture healing, particularly those fractures that had developed into nonunions. Electrical energy can be supplied to a fracture by direct application of electrodes or inducing current by use of pulsed electromagnetic field or capacitive coupling. Many of these techniques have not been standardized, so interpretation of the literature can be difficult and misleading. Despite this, there have been a few good laboratory and clinical studies to investigate the effect of electrical stimulation on fracture healing, which are reviewed. These do not permit recommendation or rejection of the technique per se; however, there is some room for optimism. The authors present some of the guidelines for using this treatment modality but suggest that all treatment should be carried out as part of a clinical trial in order to generate reliable data.

417

Electromagnetic fields for the treatment of osteoarthritis

BACKGROUND: As the focus for osteoarthritis (OA) treatment shifts away from drug therapy, we consider the effectiveness of pulsed electric stimulation which is proven to stimulate cartilage growth on the cellular level. OBJECTIVES: 1)To assess the effectiveness of pulsed electric stimulation for the treatment of osteoarthritis (OA). 2) To assess the most effective and efficient method of applying an electromagnetic field, through pulsed electromagnetic fields (PEMF) or electric stimulation, as well as the consideration of length of treatment, dosage, and the frequency of the applications. SEARCH STRATEGY: We searched PREMEDLINE, MEDLINE, HealthSTAR, CINAHL, PEDro, and the Cochrane Controlled Trials Register (CCTR) up to and including 2001. This included searches through the coordinating offices of the trials registries of the Cochrane Field of Physical and Related Therapies and the Cochrane Musculoskeletal Group for further published and unpublished articles. The electronic search was complemented by hand searches and experts in the area. SELECTION CRITERIA: Randomized controlled trials and controlled clinical trials that compared PEMF or direct electric stimulation against placebo in patients with OA. DATA COLLECTION AND ANALYSIS: Two reviewers determined the studies to be included in the review based on inclusion and exclusion criteria (JH,VR) and extracted the data using pre-developed extraction forms for the Cochrane Musculoskeletal Group. The methodological quality of the trials was assessed by the same reviewers using a validated scale (Jadad 1996). Osteoarthritis outcome measures were extracted from the publications according to OMERACT guidelines (Bellamy 1997) and additional secondary outcomes considered. MAIN RESULTS: Only three studies with a total of 259 OA patients were included in the review. Electrical stimulation therapy had a small to moderate effect on outcomes for knee OA, all statistically significant with clinical benefit ranging from 13-23% greater with active treatment than with placebo. Only 2 outcomes for cervical OA were significantly different with PEMF treatment and no clinical benefit can be reported with changes of 12% or less. REVIEWER'S CONCLUSIONS: Current evidence suggests that electrical stimulation therapy may provide significant improvements for knee OA, but further studies are required to confirm whether the statistically significant results shown in these trials confer to important benefits.

418

Electromagnetic fields for the treatment of osteoarthritis.

A B S T R A C T Background As the focus for osteoarthritis (OA) treatment shifts away from drug therapy, we consider the effectiveness of pulsed electric stimulation which is proven to stimulate cartilage growth on the cellular level. Objectives 1)To assess the effectiveness of pulsed electric stimulation for the treatment of osteoarthritis (OA). 2) To assess the most effective and efficient method of applying an electromagnetic field, through pulsed electromagnetic fields (PEMF) or electric stimulation, as well as the consideration of length of treatment, dosage, and the frequency of the applications. Search strategy We searched PREMEDLINE, MEDLINE, HealthSTAR, CINAHL, PEDro, and the Cochrane Controlled Trials Register (CCTR) up to and including 2001. This included searches through the coordinating offices of the trials registries of the Cochrane Field of Physical and Related Therapies and the Cochrane Musculoskeletal Group for further published and unpublished articles. The electronic search was complemented by hand searches and experts in the area. Selection criteria Randomized controlled trials and controlled clinical trials that compared PEMF or direct electric stimulation against placebo in patients with OA. Data collection and analysis Two reviewers determined the studies to be included in the review based on inclusion and exclusion criteria (JH,VR) and extracted the data using pre-developed extraction forms for the Cochrane Musculoskeletal Group. The methodological quality of the trials was assessed by the same reviewers using a validated scale (Jadad 1996). Osteoarthritis outcome measures were extracted from the publications according to OMERACT guidelines (Bellamy 1997) and additional secondary outcomes considered. Main results Only three studies with a total of 259 OA patients were included in the review. Electrical stimulation therapy had a small to moderate effect on outcomes for knee OA, all statistically significant with clinical benefit ranging from 13-23% greater with active treatment than with placebo. Only 2 outcomes for cervical OA were significantly different with PEMF treatment and no clinical benefit can be reported with changes of 12% or less. Authors’ conclusions Current evidence suggests that electrical stimulation therapy may provide significant improvements for knee OA, but further studies are required to confirm whether the statistically significant results shown in these trials confer to important benefits.

420

Electromagnetic fields in the treatment of postmenopausal osteoporosis: an experimental study conducted by densitometric, dry ash weight and metabolic analysis of bone tissue

The authors conducted an experimental study on 32 female rats which had been castrated at 10 months of age in order to verify the ability of pulsating electromagnetic fields to prevent osteoporosis induced by surgical menopause. Two different values of intensity of PEMFs were used: 30 G and 70 G. After 4 months of treatment the following testing was done: monophotonic bone densitometry of the lumbar spine, quantitative measurement of the dry ash weight of the femurs, and hematochemical tests to evaluate bone metabolism. The experimental study showed that the PEMFs supplied at 30 Gauss were capable of slowing down the loss of bone mass, while the PEMFs supplied at 70 Gauss obstructed bone decay, providing values for Bone Mineral Density and dry ash weight which were very similar to those observed in the non-castrated control group. Hematochemical tests did not reveal significant variations between the two groups.

421

Electromagnetic fields increase in vitro and in vivo angiogenesis through endothelial release of FGF-2

Pulsed electromagnetic fields (PEMF) have been shown to be clinically beneficial, but their mechanism of action remains unclear. The present study examined the impact of PEMF on angiogenesis, a process critical for successful healing of various tissues. PEMF increased the degree of endothelial cell tubulization (sevenfold) and proliferation (threefold) in vitro. Media from PEMF cultures had a similar stimulatory effect, but heat denaturation ablated this activity. In addition, conditioned media was able to induce proliferative and chemotactic changes in both human umbilical vein endothelial cells and fibroblasts, but had no effect on osteoblasts. Angiogenic protein screening demonstrated a fivefold increase in fibroblast growth factor beta-2 (FGF-2), as well as smaller increases in other angiogenic growth factors (angiopoietin-2, thrombopoietin, and epidermal growth factor). Northern blot analysis demonstrated an increase in FGF-2 transcription, and FGF-2 neutralizing antibody inhibited the effects of PEMF. In vivo, PEMF exposure increased angiogenesis more than twofold. We conclude that PEMF augments angiogenesis primarily by stimulating endothelial release of FGF-2, inducing paracrine and autocrine changes in the surrounding tissue. These findings suggest a potential role for PEMF in therapeutic angiogenesis.

422

Electromagnetic fields influence NGF activity and levels following sciatic nerve transection

Pulsed electromagnetic fields (PEMF) have been shown to increase the rate of nerve regeneration. Transient post-transection loss of target-derived nerve growth factor (NGF) is one mechanism proposed to signal induction of early nerve regenerative events. We tested the hypothesis that PEMF alter levels of NGF activity and protein in injured nerve and/or dorsal root ganglia (DRG) during the first stages of regeneration (6-72 hr). Rats with a transection injury to the midthigh portion of the sciatic nerve on one side were exposed to PEMF or sham control PEMF for 4 hr/day for different time periods. NGF-like activity was determined in DRG, in 5-mm nerve segments proximal and distal to the transection site and in a corresponding 5-mm segment of the contralateral nonoperated nerve. NGF-like activity of coded tissue samples was measured in a blinded fashion using the chick DRG sensory neuron bioassay. Overall, PEMF caused a significant decrease in NGF-like activity in nerve tissue (P < 0.02, repeated measures analysis of variance, ANOVA) with decreases evident in proximal, distal, and contralateral nonoperated nerve. Unexpectedly, transection was also found to cause a significant (P=0.001) 2-fold increase in DRG NGF-like activity between 6 and 24 hr postinjury in contralateral but not ipsilateral DRG. PEMF also reduced NGF-like activity in DRG, although this decrease did not reach statistical significance. Assessment of the same nerve and DRG samples using ELISA and NGF-specific antibodies confirmed an overall significant (P < 0.001) decrease in NGF levels in PEMF-treated nerve tissue, while no decrease was detected in DRG or in nerve samples harvested from PEMF-treated uninjured rats. These findings demonstrate that PEMF can affect growth factor activity and levels, and raise the possibility that PEMF might promote nerve regeneration by amplifying the early postinjury decline in NGF activity.

423

Electromagnetic fields used clinically to improve bone healing also impact lymphocyte proliferation in vitro

An important aspect of medical device development is the need to understand how a device produces a specific biological effect. The focus can then be on optimizing that effect by device modification and repeated testing. Several reports from this lab have targeted programmed cell death, or apoptosis, as a cellular pathway that is induced by exposure of transformed leukemic T-cells in culture to specific frequency and intensity electromagnetic fields (EMFs). An EMF delivery device capable of selectively inducing T-cell apoptosis in human tissues could be used to enhance healing by limiting the production of molecules that promote inflammatory disorders such as psoriasis and tendonitis. In the present study, we examined the normal T-cell response to EMF exposure in vitro. In the peripheral blood, 70-80% of the lymphocytes are T-cells, and thus is a rich source of normal cells that match the transformed T-cells used in other experiments (Jurkat cells). We isolated lymphocytes from the peripheral blood of humans and rats, cultured them in nutritive medium and exposed them to either a complex 1.8 mT pulsed EMF (Electrobiology, Inc.), a 0.1 mT, 60 Hz power frequency EMF or a 0.2 mT, 100 Hz sinusoidal EMF. Control lymphocytes were cultured similarly, without field exposure. Lymphocytes were then treated with T-cell mitogens and evaluated for proliferative capacity after an additional 72 hours culture. Results indicate that T-cell proliferation is modulated by in vitro exposure to defined EMFs. The potential use of an EMF delivery device capable of selectively inducing such T-cell effects is discussed.

424

Electromagnetic fields: a novel prophylaxis for steroid-induced osteonecrosis

Establishing a means to prevent osteonecrosis after corticosteroid administration is an important theme. We asked whether pulsed electromagnetic field stimulation, a noninvasive treatment, could prevent osteonecrosis. Ninety rabbits were divided into four treatment groups: (1) exposure of 10 hours per day to electromagnetic stimulation for 1 week, followed by injection of methylprednisolone (20 mg/kg), and exposure of 10 hours per day to electromagnetism for a further 4 weeks (n = 40); (2) methylprednisolone injection only (n = 40); (3) no treatment (n = 5); and (4) exposure of 10 hours per day to electromagnetism for 5 weeks (n = 5). After 5 weeks, we harvested and histologically examined femurs bilaterally. The frequency of osteonecrosis was lower in the steroid-electromagnetism group (15/40) than in the steroid-only group (26/40). No necrotic lesions were found in the two control groups. We observed no clear effects of electromagnetism on the number, location, extent, and repair of necrotic lesions and intramedullary fat cell size in affected rabbits. Pulsed electromagnetic field stimulation reportedly augments angiogenesis factors and dilates blood vessels; these effects may lower the frequency of osteonecrosis. Exposure to pulsed electromagnetic field stimulation before corticosteroid administration could be an effective means to reduce the risk of osteonecrosis.

425

Electromagnetic interaction of arbitrary radial-dependent anisotropic spheres and improved invisibility for nonlinear-transformation-based cloaks

An analytical method of electromagnetic wave interactions with a general radially anisotropic cloak is established. It is able to deal with arbitrary parameters [ epsilon r (r) , mu r (r) , epsilon t (r) , and mu t (r) ] of a radially anisotropic inhomogeneous shell. The general cloaking condition is proposed from the wave relations, in contrast to the method of transformation optics. Spherical metamaterial cloaks with improved invisibility performance are achieved with optimal nonlinearity in transformation and core-shell ratio.

426

Electromagnetic interference in cardiac rhythm management devices

Clinicians caring for cardiac device patients with implanted pacemakers or cardioverter defibrillators (ICDs) are frequently asked questions by their patients concerning electromagnetic interference (EMI) sources and the devices. EMI may be radiated or conducted and may be present in many different forms including (but not limited to) radiofrequency waves, microwaves, ionizing radiation, acoustic radiation, static and pulsed magnetic fields, and electric currents. Manufacturers have done an exemplary job of interference protection with device features such as titanium casing, signal filtering, interference rejection circuits, feedthrough capacitors, noise reversion function, and programmable parameters. Nevertheless, EMI remains a real concern and a potential danger. Many factors influence EMI including those which the patient can regulate (eg, distance from and duration of exposure) and some the patient cannot control (eg, intensity of the EMI field, signal frequency). Potential device responses are many and range from simple temporary oversensing to permanent device damage Several of the more common EMI-generating devices and their likely effects on cardiac devices are considered in the medical, home, and daily living and work environments.

427

Electromagnetic interference in implantable pacemakers

The inhibited pacemaker (VVI or AAI) has become the most popular in recent years because of its ability to combine a physiological advantage with economical current consumption in cases with spontaneous activity. One of its disadvantages is its sensitivity to external electromagnetic interference. Though today's pacemakers possess effective protection against most interference signals there may be instances in which patients are subjected to uncomfortable or even life-threatening situations. This is the case of "amplitude modulated" or "pulsed" fields with modulation frequencies in the physiological range. Fields of that sort have been found in the vicinity of a welder, an electric steel plant, and in medical practice where therapeutic currents were applied. Even touch-actuated switches may influence a demand pacemaker. However, these situations may be overcome by a device within the pacemaker for simple time analysis which can be carried out with few components. If electromagnetic fields of diathermy equipment are applied, today's pacemakers may react with intolerably high or low rates. They should, therefore, be avoided.

428

Electromagnetic interference of pacemakers by mobile phones

The topic of interference of pacemakers by mobile phones has evoked a surprisingly strong interest, not only in pacemaker patients, but also in the public opinion. The latter is the more surprising, as in the past, the problem of interference has scarcely found the attention that it deserves in the interest of the patient. It was the intention of our investigation to test as many pacemaker models as possible to determine whether incompatibility with mobile phones of different modes may exist, using an in vitro measuring setup. We had access to 231 different models of 20 manufacturers. During the measurements, a pulse generator together with a suitable lead was situated in a 0.9 g/L saline solution, and the antenna of a mobile phone was positioned as close as possible. If the pulse generator was disturbed, the antenna was elevated until interference ceased. The gap in which interference occurred was defined as "maximum interference distance." All three nets existing in Germany, the C-net (450 MHz, analogue), the D-net (900 MHz, digital pulsed), and the E-net (1,800 MHz, digital pulsed) were tested in succession. Out of 231 pulse generator models, 103 pieces corresponding to 44.6% were influenced either by C- or D-net, if both results were totaled. However, this view is misleading as no patient will use C- and D-net phones simultaneously. Separated into C- or D-net interference, the result is 30.7% for C or 34.2% for D, respectively, of all models tested. The susceptible models represent 18.6% or 27% of today's living patients, respectively. All models were resistant to the E-net. With respect to D-net phones, all pacemakers of six manufacturers proved to be unaffected. Eleven other manufacturers possessed affected and unaffected models as well. A C-net phone only prolonged up to five pacemaker periods within 10 seconds during dialing without substantial impairment to the patient. Bipolar pacemakers are as susceptible as unipolar ones. The following advice for patients and physicians can be derived from our investigations: though 27% of all patients may have problems with D-net phones (not C- or E-net), the application should generally not be questioned. On the contrary, patients with susceptible devices should be advised that a distance of 20 cm is sufficient to guarantee integrity of the pacemaker with respect to hand held phones. Portables, on the other hand, should have a distance of about 0.5 m. Pacemaker patients really suffering from mobile phones are very rare unless the phone is just positioned in the pocket over the pulse generator. The contralateral pocket or the belt position guarantees, in 99% of all patients, undisturbed operation of the pacemaker. A risk analysis reveals that the portion of patients really suffering from mobile phones is about 1 out of 100,000. Nevertheless, it would be desirable in the future if implanting physicians would use only pacemakers with immunity against mobile phones as guaranteed by the manufacturers.

429

Electromagnetic interference shielding properties of carbon nanotube buckypaper composites

Preformed carbon nanotube thin films (10-20 microm), or buckypapers (BPs), consist of dense and entangled nanotube networks, which demonstrate high electrical conductivity and provide potential lightweight electromagnetic interference (EMI) solutions for composite structures. Nanocomposite laminates consisting of various proportions of single-walled and multi-walled carbon nanotubes, having different conductivity, and with different stacking structures, were studied. Single-layer BP composites showed shielding effectiveness (SE) of 20-60 dB, depending on the BP conductivity within a 2-18 GHz frequency range. The effects on EMI SE performance of composite laminate structures made with BPs of different conductivity values and epoxy or polyethylene insulating layer stacking sequences were studied. The results were also compared against the predictions from a modified EMI SE model. The predicted trends of SE value and frequency dependence were consistent with the experimental results, revealing that adjusting the number of BP layers and appropriate arrangement of the BP conducting layers and insulators can increase the EMI SE from 45 dB to close to 100 dB owing to the utilization of the double-shielding effect.

430

Electromagnetic interventions in musculoskeletal disorders

Electromagnetic interventions in general and those considering the musculoskeletal system in particular hold many obscurities. Several studies revealing positive effects of electromagnetic fields oppose those showing no beneficial effects. After a historical review and a discussion of basic details on electromagnetic signals, this article provides information on the effects of electromagnetic fields on a cellular level and gives an account of preclinical and clinical studies focused on electromagnetic interventions by means of weak pulsed electromagnetic fields on musculoskeletal disorders.

431

Electromagnetic modulation of biological processes: influence of culture media and significance of methodology in the Ca-uptake by embryonal chick tibia in vitro

The present studies are aimed at establishing molecular correlations in the interaction of very low frequency electromagnetic fields with biological systems. Ca-uptake by chick embryo tibia rudiment in short-term culture was a useful model. Tibiae of 8- to 10-day-old chick embryos were incubated 60 min in simplified culture media in the presence of 45Ca at 37.5 +/- 0.5 degrees C either inside or outside pulsating electromagnetic fields. Radioactivity count in the medium was the most accurate method for determining Ca-uptake by the rudiment. The effect of the fields on the Ca-uptake depended markedly on the chemical composition of the culture medium: bicarbonate was indispensable; glucose or sucrose was important; phosphate was potentiating; ethanol, Mg2+, and NaF were stimulating. The field had no effect in (a) blank medium without tibia, (b) tibiae that had been altered by fixation with aqueous glutaraldehyde, (c) nonliving artificial systems endowed with great or small ion sorption capacity. The unique bicarbonate effect with living systems and the passive behavior of nonliving ion sorbing systems prompt the suggestion that the electromagnetic field probably couples with specific processes, such as a bicarbonate-dependent Ca2+ ATPase and the active ion transport, at the cell membrane level. The molecular mechanisms remain to be established.

432

Electromagnetic navigation for percutaneous guide-wire insertion: accuracy and efficiency compared to conventional fluoroscopic guidance

The combination of electromagnetic (EM) navigation with intraoperative fluoroscopic images has the potential to create the ideal environment for spinal surgical applications. This technology enhances standard intraoperative fluoroscopic information for localization of the pedicle entry point and trajectory and may be an effective alternative to other image-guided surgery (IGS) systems. This study was performed to assess the accuracy and time efficiency (placement and fluoroscopy) using EM navigation versus conventional fluoroscopy in the placement of pedicle guide-wires. Kirschner wire (K-wire) placement was performed in cadavers from T8 to S1 using EM navigation versus conventional fluoroscopy. Time for set-up, placement, and fluoroscopy was recorded. After insertion, the accuracy for each level was assessed for the presence and location of facet joint, pedicle, or vertebral cortical perforation using computed tomography imaging with multiplanar reconstructions. K-wire placements were 100% successful for both methods. Comparing EM-based IGS-assisted placement with the conventional fluoroscopy method showed a longer set-up time of 9.6 min versus 3.6 min, respectively. However, mean placement times of 6.3 min versus 9.7 min (P=0.005) and mean fluoroscopy times of 11 s versus 48 s (P<0.0001) were both shorter for the EM group. There were no significant differences in the proportion of pedicle, vertebral body, or facet joint breaches. A higher proportion of ideal trajectories was achieved in the EM group. Therefore, we have shown that an EM IGS system can assist the spine surgeon in minimally invasive pedicle screw insertion by providing high-accuracy K-wire placement with a significant reduction in fluoroscopy time.

433

Electromagnetic probing for target detection: rejection of surface clutter based on the Wigner distribution

The Wigner distribution function is investigated as a signal processing tool to detect subsurface targets closely located beneath a randomly rough surface. Information provided by a bistatic arrangement of sources and detectors can be used to discriminate target and surface response based on their scattering behavior. It is shown that the bilinearity of the Wigner distribution function can be exploited for nonlinear amplification of the target response. This is achieved by averaging the Wigner distribution of the detected signal for different source locations. Target detection is further improved by numerically backpropagating the detected signal to the surface. A statistical evaluation based on simulated data sets is used to evaluate the performance of the detection method.

434

Electromagnetic pulse distortion in living tissue

Insight into the distortion of electromagnetic (EM) signals in living tissue is important for optimising medical applications. To obtain this insight, field calculations have been carried out for a plane-stratified configuration of air, skin, fat, muscle and bone tissue. In this configuration, an EM field is generated by a prescribed pulsed current in a circular loop. Debye dispersion models have been developed for the description of the permittivity of the tissues. The field problem is solved analytically with the aid of a temporal Fourier transformation and a spatial Hankel transformation. The corresponding inverse transformations have been carried out numerically. To demonstrate the influences of stratification and dispersion separately, the EM fields in the stratified configuration, in a completely muscle-filled space and in vacuum are compared. Two different pulses have been considered; narrow and wide. It emerges that dispersion results in a retardation and an attenuation of the field. Stratification causes additional fluctuations of the time-dependent field. Furthermore, the conductivity of tissue at high frequencies is mainly determined by its water content. Tissues with high water content, like muscle and skin, exhibit higher conductivity at high frequencies than fat and bone. Muscle and skin tissue therefore behave as low-pass filters to EM signals.

435

Electromagnetic pulse propagation in dispersive planar dielectrics

The responses of a plane-wave pulse train irradiating a lossy dispersive dielectric half-space are investigated. The incident pulse train is expressed as a Fourier series with summing done by the inverse fast Fourier transform. The Fourier series technique is adopted to avoid the many difficulties often encountered in finding the inverse Fourier transform when transform analyses are used. Calculations are made for propagation in pure water, and typical waveforms inside the dielectric half-space are presented. Higher harmonics are strongly attenuated, resulting in a single continuous sinusoidal waveform at the frequency of the fundamental depth in the material. The time-averaged specific absorption rate (SAR) for pulse-train propagation is shown to be the sum of the time-averaged SARs of the individual harmonic components of the pulse train. For the same average power, calculated SARs reveal that pulse trains generally penetrate deeper than carrier-frequency continuous waves but not deeper than continuous waves at frequencies approaching the fundamental of the pulse train. The effects of rise time on the propagating pulse train in the dielectrics are shown and explained. Since most practical pulsed systems are very limited in bandwidth, no pronounced differences between their response and continuous wave (CW) response would be expected. Typical results for pulse-train propagation in arrays of dispersive planar dielectric slabs are presented. Expressing the pulse train as a Fourier series provides a practical way of interpreting the dispersion characteristics from the spectral point of view.

436

Electromagnetic pulsed-wave radiation in spherical models of dispersive biological substances

In analytical studies, we investigated induced-field patterns and SAR distributions in a lossy, dispersive, homogeneous, dielectric sphere typical of muscle tissue as irradiated by a plane-wave pulse train consisting of a pulse-modulated sinusoidal carrier wave. Calculations were made for carrier frequencies of 1, 3, and 15 GHz, pulse widths of 0.333, 2.0 and 4 ns, and pulse repetition rates of 1.11 x 10(6), 100 x 10(6), and 181.18 x 10(6) pps. The classical Mie solution was modified for a train of incident pulses that was represented by a Fourier series, and the fast-Fourier transform was used to sum the series. Computationally, the technique proved to be feasible and less expensive than we expected. The calculated field patterns show that the sphere's physical dimensions and the internal wavelength of the carrier greatly influence the nature of pulse-train propagation in the sphere. Harmonics having internal wavelengths nearly equal to the radius of the sphere produce most of the absorption; other harmonics produce little absorption. An intense hot spot is observed in spheres with radii that match the carriers' wavelengths.

437

Electromagnetic scattering by densely packed particulate ice at radar wavelengths: exact theoretical results and remote-sensing implications

We use the numerically exact superposition T-matrix method to compute electromagnetic scattering characteristics of a macroscopic volume of a discrete random medium filled with wavelength-sized spherical particles with a refractive index typical of water ice at centimeter wavelengths. Our analysis demonstrates relative strengths of various optical observables in terms of their potential remote-sensing content. In particular, it illustrates the importance of accounting for the forward-scattering interference effect in the interpretation of occultation measurements of planetary rings. We show that among the most robust indicators of the amount of multiple scattering inside a particulate medium are the cross-polarized scattered intensity, the same-helicity scattered intensity, and the circular polarization ratio. We also demonstrate that many predictions of the low-packing-density theories of radiative transfer and coherent backscattering are applicable, both qualitatively and semi-quantitatively, to densely packed media.

438

Electromagnetic stimulation as a treatment of tinnitus: a pilot study

This paper reports the results of a study to determine whether pulsed electromagnetic stimulation, applied over the mastoid bone, caused an improvement in the level of tinnitus in long-standing tinnitus sufferers. Fifty-eight patients from the Liverpool Tinnitus Association volunteered to take part in a double-blind placebo controlled trial. Active and placebo devices were randomly allocated to these patients on their first visit. At the end of one week of treatment, each patient noted whether their tinnitus had completely disappeared, was improved, unchanged or made worse by the treatment Forty-five per cent of the patients who completed the trial were improved by the active device, but only 9% by placebo (P = 0.0013, Mann-Whitney test). We suggest that electromagnetic stimulation may be an effective treatment in some tinnitus sufferers.

439

Electromagnetic stimulation of canine bone grafts

We evaluated the use of pulsed electromagnetic-field stimulation to affect the rate of healing or incorporation of segmental autogenous cortical bone grafts in the dog in vivo. This non-invasive method of electrical stimulation has been implicated in increasing bone osteogenesis or augmentation of the repair process in the canine fibular osteotomy. We utilized two-month and six-month stimulation protocols. At six months, all of the animals were evaluated biomechanically using rapid-loading torsional testing. Histological evaluation using tetracycline labeling was used to evaluate cumulative new-bone formation and porosity, while graft-host time to union was evaluated roentgenographically every two weeks. Recent reports have implied that particular pulse configurations might be effective in improving graft revascularization and incorporation. The results of our investigation indicated that there was no significant effect on the biomechanical strength, histological presentation, or time to union with either two months or six months of pulsed electromagnetic-field stimulation using the particular waveform described.

440

Electromagnetic therapy for treating pressure ulcers

A B S T R A C T Background Pressure ulcers are defined as areas “of localized damage to the skin and underlying tissue caused by pressure, shear, friction and/or the combination of these”. In the UK, pressure ulcers occur in 5 to 32% of District General Hospitals people and in 4 to 7% of people in community settings. Electromagnetic therapy, in which electrodes produce an electromagnetic field across the wound, may improve healing of chronic wounds such as pressure ulcers. Objectives To assess the effects of electromagnetic therapy on the healing of pressure ulcers. Search strategy For this first update, we searched the Cochrane Wounds Group Specialised Register (last searched October 2005); CENTRAL (The Cochrane Library 2005, Issue 4); MEDLINE (1966 to October 2005); EMBASE (1980 to October 2005); and CINAHL (1982 to October 2005). Selection criteria Randomised controlled trials comparing electromagnetic therapy with sham electromagnetic therapy, or other (standard) treatment. Data collection and analysis For this first update, two authors independently scrutinized the results of the search to identify relevant RCTs and obtained full reports of potentially eligible studies. For the original review, details of eligible studies were extracted and summarised using a data extraction sheet. Attempts weremade to obtain missing data by contacting authors. Data extraction was checked by a second author.Meta-analysis was applied to combine the results of trials when the interventions and outcome measures were sufficiently similar. Main results This update identified no new trials. Two RCTs were identified for inclusion in the original review (total of 60 participants). One was a three-armed study comparing electromagnetic therapy with electromagnetic therapy in combination with standard therapy, and with standard therapy alone, on 17 female and 13 male with grade II and III pressure ulcers. The other study compared electromagnetic therapy with sham therapy in 30 male participants with a spinal cord injury and a grade II or grade III pressure ulcer. Neither study found a statistically significant difference between the healing rates of pressure ulcers in people treatedwith electromagnetic therapy compared with those in the control group. Authors’ conclusions The results provide no evidence of benefit in using electromagnetic therapy to treat pressure ulcers. However, the possibility of a beneficial or harmful effect cannot be ruled out, due to the fact that there were only two included trials both with methodological limitations and small numbers of participants. Further research is recommended.

441

Electromagnetic therapy for treating venous leg ulcers.

A B S T R A C T Background Leg ulceration is a common, chronic, recurring condition. The estimated prevalence of leg ulcers in the UK population is 1.5 to 3 per 1000. Venous ulcers (also called stasis, or varicose ulcers) comprise 80 to 85% of all leg ulcers. Electromagnetic therapy is sometimes used as a treatment to assist the healing of chronic wounds such as venous leg ulcers. Objectives To assess the effects of electromagnetic therapy on the healing of venous leg ulcers. Search strategy For this first review update, we searched the Cochrane Wounds Group Specialised Register (last searched October 2005); CENTRAL (The Cochrane Library 2005, Issue 4); MEDLINE (1966 to October 2005); EMBASE (1980 to October 2005); and CINAHL (1982 to October 2005). Selection criteria Randomised controlled trials comparing electromagnetic therapy with sham electromagnetic therapy or other treatments. Data collection and analysis For the original review, details of eligible studies were extracted and summarised using a data extraction sheet. Attempts were made to obtain missing data by contacting authors. A second reviewer checked data extraction. Meta-analysis was applied to combine the results of trials where the interventions and outcome measures were adequately similar. For this first update, two reviewers independently scrutinized the results of the search to identify relevant RCTs and obtained full reports of potentially eligible studies. In the case of disagreements, a final decision was made either after discussion between two reviewers or consultation with a third party (a member of the Cochrane Wounds Group). Main results This update identified no new trials. A total of three eligible RCTs were identified by the original review. Two trials compared the use of electromagnetic therapy with sham therapy and one trial compared it with standard topical treatments. One trial found a difference in healing rates of borderline statistical significance between electromagnetic therapy and sham therapy, although the direction of treatment effect was consistently in favour of electromagnetic therapy, the difference was not statistically significant. Authors’ conclusions There is currently no reliable evidence of benefit of electromagnetic therapy in the healing of venous leg ulcers. Further research is needed.

442

Electromagnetic Tracking of Intrafraction Prostate Displacement in Patients Externally Immobilized in the Prone Position

PURPOSE: To evaluate intrafraction prostate displacement among patients immobilized in the prone position using real-time monitoring of implanted radiofrequency transponders. METHODS AND MATERIALS: The Calypso localization system was used to track prostate motion in patients receiving external beam radiation therapy (XRT) for prostate cancer. All patients were treated in the prone position and immobilized with a thermoplastic immobilization device. Real-time measurement of prostate displacement was recorded for each treatment fraction. These measurements were used to determine the duration and magnitude of displacement along the three directional axes. RESULTS: The calculated centroid of the implanted transponders was offset from the treatment isocenter by >/=2 mm, >/=3 mm, and >/=4 mm for 38.0%, 13.9%, and 4.5% of the time. In the lateral dimension, the centroid was offset from the treatment isocenter by >/=2 mm, >/=3 mm, and >/=4 mm for 2.7%, 0.4%, and 0.06% of the time. In the superior-inferior dimension, the centroid was offset from the treatment isocenter by >/=2 mm, >/=3 mm, and >/=4 mm for 16.1%, 4.7%, and 1.5% of the time, respectively. In the anterior-posterior dimension, the centroid was offset from the treatment isocenter by >/=2 mm, >/=3 mm, and >/=4 mm for 13.4%, 3.0%, and 0.5% of the time. CONCLUSIONS: Intrafraction prostate displacement in the prone position is comparable to that in the supine position. For patients with large girth, in whom the supine position may preclude accurate detection of implanted radiofrequency transponders, treatment in the prone position is a suitable alternative.

443

Electromagnetic treatment of shoulder periarthritis: a randomized controlled trial of the efficiency and tolerance of magnetotherapy

The potential benefit of magnetotherapy was investigated in 47 consecutive outpatients with periarthritis of the shoulder. Using a controlled triple-blind study design, one group of patients received hot pack applications and passive manual stretching and pulley exercises; the other group received the same therapy plus magnetotherapy. Treatment was administered three times a week. For a maximum of three months, a standardized treatment protocol was used. There was no significant improvement in pain reduction or in range of motion with electromagnetic field therapy. After 12 weeks of therapy, the patients who received magnetotherapy showed mean pain scores of 1.5 (+/- .61 SD) at rest, 2.2 (+/- .76 SD) on movement, and 1.9 (+/- .94 SD), on lying, compared to scores for the control group of 1.4 (+/- .65 SD), 2.2 (+/- .7 SD), and 1.9 (+/- .95 SD), respectively. Linear pain scale scores improved from 71 to 21 for both groups. At 12 weeks the gain in range of motion was mean 109 degrees +/- 46.8 in patients receiving electromagnetic field therapy, compared to 122 degrees +/- 33.4 for the controls (not significant). At entry, the functional handicap score was 53.5 for both groups. At 12 weeks, it was 24 for the magnetotherapy group and 17 for the control group (difference not significant). In conclusion, this study showed no benefit from magnetotherapy in the pain score, range of motion, or improvement of functional status in patients with periarthritis of the shoulder.

444

Electromagnetic wave scattering by Schwarzschild black holes

We analyze the scattering of a planar monochromatic electromagnetic wave incident upon a Schwarzschild black hole. We obtain accurate numerical results from the partial wave method for the electromagnetic scattering cross section and show that they are in excellent agreement with analytical approximations. The scattering of electromagnetic waves is compared with the scattering of scalar, spinor, and gravitational waves. We present a unified picture of the scattering of all massless fields for the first time.

445

Electronic article surveillance: a possible danger for pacemaker patients

In order to evaluate if antitheft devices commonly designed as electronic article surveillance (EAS) systems can be dangerous for pacemaker patients, in vitro and in vivo studies were made in close cooperation between a pacemaker center and an EAS designer. Three types of EAS radiation including radiofrequency, magnetic, and pulsed electromagnetic fields were applied to various pacemakers. The in vitro study consisted of exposing to the EAS fields 28 pacemakers connected to unipolar leads. Radiofrequency fields and pulsed electromagnetic fields evoked minor effects and no prolonged inhibitions. When exposed to magnetic fields, most of the pacemakers switched to "fixed rate" pacing, but inhibitions were observed in 13 pacemakers exposed to 300 Hz, and in 14 pacemakers exposed to a 10-kHz magnetic field when they were moved at cardiac frequencies within the fields. The in vivo study was made on 32 volunteers treated by 26 different pacemakers: 22 single chamber and ten dual chamber. All patients had been monitored in the pacemaker clinic and pacemakers were working well. Radiofrequency and pulsed electromagnetic fields did not affect the pacemaker function. Magnetic interference evoked prolonged inhibition of seven out of the ten dual chamber pacemakers, causing brief asystole in patients being continually paced. None of the dual chamber pacemakers incorporated "safety stimulation intervals" after ventricular blanking. The EAS artifact was sensed after the ventricular blanking causing a cross-talk ECG pattern. No reprogramming was induced by the electromagnetic fields. This experience demonstrates that certain EAS may be dangerous for pacemaker patients. Following this cooperative study a pacemaker safe EAS circuit delivering short bursts of magnetic fields has been designed.

446

Electrophysiological considerations relevant to the limiting of pulsed electric and magnetic fields

The objective of the study was to theoretically examine the stimulation threshold of large myelinated axons and to use the results to formulate criteria for exposure limits of pulsed magnetic fields. The induced electric fields were calculated with a homogeneous tissue equivalent prolate spheroid. The stimulation level of the field was computed with the SENN model by using a folded axon with 2 mm separation for the Ranvier nodes. In the case of rectangular induced electric field pulses, the asymptotic stimulation level for electric field strength was 10 Vm(-1) with pulse durations greater than 100 micro(s) and for integrated electric field strength 1 x 10(-3) V m(-1)s with pulse durations less than 100 micro(s). The latter threshold level was exceeded in the surface of the prolate spheroid when the magnetic flux density changed by more than 7.4 mT within 100 micro(s). For sinusoidal bursts, the threshold amplitude of the magnetic field decreased asymptotically to a minimum value 2.5 mT when the carrier frequency and burst duration exceeded 5 kHz and 100 micro(s), respectively. If the same safety criteria are applied for pulsed and continuous exposure, the peak limits for induced current densities and magnetic field can exceed the amplitude values of the limits for continuous exposure only by a factor varying from 3 to 10.

447

Electroporation therapy: a new approach for the treatment of head and neck cancer

Electroporation can deliver exogenous molecules like drugs and genes into cells by pulsed electric fields through a temporary increase in cell membrane permeability. This effect is being used for the treatment of cancer by intratumoral injection of low dosage of an otherwise marginally effective chemotherapeutic drug, bleomycin. Application of a pulsed electric field results in substantially higher uptake of the drug and enhanced killing of the cancer cells than is possible by conventional methods. The MedPulser, a new treatment system for local electroporation therapy (EPT) of head and neck tumors was developed and is described in this paper. EPT with bleomycin has been found to be very effective in killing cancer cells in vitro, in mouse tumor xenografts in vivo, and in tumors in humans. Ten head and neck cancer patients with recurring or unresponsive tumors were enrolled in a Phase I/II clinical trial. Treatment of the entire tumor mass in each of eight patients resulted in five complete responses confirmed by biopsy and MRI, and three partial responses (> or = 50% shrinkage). Two additional patients who received partial treatment of their tumor mass had local response where treated, but no overall lesion remission. Duration of the complete responses ranges from 2-10 months to date. All patients tolerated the treatment well with no significant local or systemic adverse effects.

448

Electrotherapy for neck disorders

PEMF Four trials met our selection criteria. Trock 1994 studied the efficacy of extremely low frequency PEMF therapy (eighteen 30- minute sessions in six weeks) for participants with chronic osteoarthritis of the cervical spine, compared to placebo treatment (N/n = 42/39). The magnetic field was applied by a coil, generating extreme low frequency rectangular pulses (5 to 25 Hz; 10 to 25 Gauss). Out of 17 measurement variables and times, only four were significantly different in favour of PEMF treatment. Compared to placebo, patient global assessment and activities of daily living were not improved. We rated the methodological quality as high (5/5). There is limited evidence that extremely low frequency PEMF reduces pain in people with chronic cervical spine osteoarthritis. Foley-Nolan 1990 studied the efficacy of a high frequency PEMF therapy versus placebo on 20 people with chronic MND. The device consisted of a battery-driven short wave diathermy power source (27 MHz, 100 g weight) with very small, athermic impulses (1.5 mW/cm2), applied by a cervical collar. In a second publication (Foley-Nolan 1992) the authors studied the efficacy of high frequency PEMF therapy (same system as described by Foley-Nolan 1990) on 20 patients with acute WAD, compared to placebo PEMF. We rated the methodological quality of both studies to be high (5/5). The reported results were conflicting. In both trials, pain intensity (measured with VAS) was reduced for those receiving PEMF therapy after three weeks. In the second trial only, this was sustained for six weeks, but did not last for 12 weeks. There is limited evidence that high frequency PEMF only reduces pain for participants with acute and chronic MND immediately post treatment. Provinciali 1996 compared the efficacy of two multimodal rehabilitation models on 60 patients with acute WAD of less than two months duration. Group A received relaxation training, neck school for lumbar lordosis reduction, psychological and manual treatment. Group B received high frequency PEMF (same systemas described by Foley-Nolan 1990), iontophoresis, TENS and ultrasound. The authors reported that Group A had significant improvement in pain, return to work and self assessment of outcome. Neither treatment characteristics nor specific data concerning high frequency PEMF outcomes were reported. The contribution of high frequency PEMF to this multimodal treatment of WAD could not be determined. Side effects No adverse side effectswere reported in any of the included studies.

449

Electrotherapy for neck disorders

BACKGROUND: Neck disorders are common, disabling and costly. The effectiveness of electrotherapy as a physiotherapy option has remained unclear. OBJECTIVES: To assess whether electrotherapy, either alone or in combination with other treatments, relieves pain, or improves function/disability, patient satisfaction, and global perceived effect in adults with mechanical neck disorders (MND). SEARCH STRATEGY: Computer-assisted searches of bibliographic databases: CENTRAL, MEDLINE, EMBASE, MANTIS, CINAHL, and ICL, without language restrictions, from their beginning to March 2003. SELECTION CRITERIA: Randomised or controlled clinical trials with quasi-randomisation (alternate allocation, case record numbers, dates of birth, etc.), in any language, investigating the effects of electrotherapy as a treatment for MND. DATA COLLECTION AND ANALYSIS: At least two authors independently conducted citation identification, study selection, data abstraction, and methodological quality assessment. Using a random-effects model, relative risk, and standardized mean differences were calculated. The reasonableness of combining studies was assessed on clinical and statistical grounds. Due to heterogeneity, pooled effect measures were not calculated. MAIN RESULTS: Fourteen comparisons (525 people with MND), in 11 publications, were included in this review. The analysis was limited by underpowered low quality trials, paucity of literature, and heterogeneity of treatment subtypes. The results for the electrotherapy subtypes are: Limited evidence of benefit: low or high frequency pulsed electromagnetic field (PEMF) compared to placebo, provides immediate post treatment pain relief only for chronic MND, acute whiplash (WAD) Unclear or conflicting evidence: direct and modulated Galvanic current compared to other treatments for pain in acute, subacute, chronic occipital headache iontophoresis compared to other treatments for pain, RTW, and self-assessment of overall outcome in acute, subacute WAD TENS compared to placebo for pain in acute WAD, chronic MND PEMF compared to placebo for medium or long term effect on pain, patient assessment of improvement, ADL in acute WAD, chronic MND Limited evidence of no benefit: diadynamic current compared to placebo for reduction of trigger point tenderness in chronic MND with radicular findings, cervicogenic headache permanent magnets compared to a placebo for pain in chronic MND electric muscle stimulation compared to a sham control for pain in chronic MND. AUTHORS' CONCLUSIONS: We can not make any definitive statements on electrotherapy for MND. The current evidence on Galvanic current (direct or pulsed), iontophoresis, TENS, EMS, PEMF and permanent magnets is either lacking, limited, or conflicting. Possible new trials on these interventions should have larger patient samples and include more precise standardization and description of all treatment characteristics.

450

Elevated sister chromatid exchange frequencies in dividing human peripheral blood lymphocytes exposed to 50 Hz magnetic fields

The in vitro cytomolecular technique, sister chromatid exchange (SCE), was applied to test the clastogenic potentiality of extremely low frequency (ELF) electromagnetic fields (EMFs) on human peripheral blood lymphocytes (HPBLs). SCE frequencies were scored in dividing peripheral blood lymphocytes (PBLs) from six healthy male blood donors in two rounds of experiments, R1 and R2, to determine reproducibility. Lymphocyte cultures in the eight experiments conducted in each round were exposed to 50 Hz sinusoidal (continuous or pulsed) or square (continuous or pulsed) MFs at field strengths of 1 microT or 1 mT for 72 h. A significant increase in the number of SCEs/cell in the grouped experimental conditions compared to the controls was observed in both rounds. The highest SCE frequency in R1 was 10.03 for a square continuous field, and 10.39 for a square continuous field was the second highest frequency in R2. DNA crosslinking at the replication fork is proposed as a model which could explain the mechanistic link between ELF EMF exposure and increased SCE frequency.

451

ELF fields and photooxidation yielding lethal effects on cancer cells

The lethal effect on human cancer cells was studied under three types of treatment: A) an ELF pulsed sinusoidal of 50 Hz electromagnetic field (PEMF) with amplitudes between 10 and 55 mT; B) the field and a cytostatic agent (actinomycin-C); and C) the field, the cytostatic agent, which has a photodynamic effect, and exposure to a halogen lamp. The results show a decreasing vitality of human K-562 and U-937 cancer cells in suspension with each additional treatment. Combination with other parameters as hyperthermia and/or hyperacidity could yield high killing rates by this noninvasive method.

452

ELF magnetic field affects proliferation of SPD8/V79 Chinese hamster cells but does not interact with intrachromosomal recombination

Extremely low-frequency (ELF) magnetic fields have previously been shown to affect conformation of chromatin, cell proliferation, and calcium metabolism. Possible mutagenic and carcinogenic effects of ELF have also been discussed and tested. In this study, intrachromosomal recombination in the hprt gene after exposure to ELF magnetic field was investigated using the SPD8 recombination assay. SPD8 cells, derived from V79 Chinese hamster cells were exposed to ELF at a specific combination of static and ELF magnetic fields, that has been proven to have effects on chromatin conformation in several cell types. The genotoxic agent camptothecin (CPT) was used either as a positive control or simultaneously with ELF. We also analysed the effect of ELF and CPT on chromatin conformation with the anomalous viscosity time dependence (AVTD) technique, cell growth kinetics, and cell survival with clonogenic assay. DNA fragmentation was analysed by pulsed field gel electrophoresis (PFGE). ELF did not induce recombination alone, neither did ELF modify the recombinogenic effect of CPT. Although, there was no effect on cell survival in response to ELF exposure, inhibition of cell growth was observed. On the other hand, ELF exposure partly counteracted the growth inhibition seen with CPT. The data suggest that ELF exposure may stimulate or inhibit cell growth depending on the state of the cells. Although, ELF did not induce recombination, a weak but statistically significant DNA fragmentation comparable with CPT-induced fragmentation was observed with PFGE 48h after exposure to ELF.

453

ELF magnetic therapy and oxidative balance.

Knowledge about the relationship between exposure to extremely low-frequency (ELF) EMF and formation (or neutralization) of free radicals in the living cells is limited. Studies performed on animals and plants have shown conflicting effects on the relation between EMF and oxidative stress. Very few experiments have been performed on humans. The present study reports on the effects of an ELF magnetic therapy device (Seqex) on oxidative scale in humans. This device supplies complex magnetic signals with specific choices of frequency, intensity, and shape that are based on Liboff's ion cyclotron resonance hypothesis. Thirty-two healthy volunteers were treated using the Seqex cycle. A quantitative determination of oxidative stress was obtained at three time points by measuring Malondialdehyde (MDA) concentrations in peripheral blood before and after the cycle and one month following completion of the cycle. A highly significant reduction in mean MDA (53.8%, p = 0.0002) was found at the end of the treatment. One month later the mean MDA had again risen, but there was still a significant overall reduction of 15.6% (p = 0.010) compared to original values.

454

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

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

455

Elicitation of "childhood memories" in hypnosis-like settings is associated with complex partial epileptic-like signs for women but not for men: implications for the false memory syndrome

20 male and 20 female undergraduate students were exposed singly for 20 min. to an exotic setting (partial sensory deprivation and weak, bilateral transtemporal pulsed magnetic fields) that enhances relaxation and exotic experiences. The numerical incidence of subjective experiences described as old memories, dreams, emotions, or vestibular sensations did not differ significantly between the sexes; however, women who reported a greater prevalence of preexperimental complex partial epileptic-like signs were more likely to report experiences of "old memories" (r = 0.61) while men who exhibited these signs were more likely to report dream-like (r = 0.49) experiences. Because complex partial epileptic-like signs are positively associated with suggestibility, the potential contribution of this differential gender effect to the etiology of the False Memory Syndrome requires further investigation.

456

Emergent fluctuation hot spots on the fermi surface of CeIn(3) in strong magnetic fields

de Haas-van Alphen measurements on CeIn3 in pulsed magnetic fields of up to 65 T reveal an increase in the quasiparticle effective mass with the field concentrated at "hot spots" on the Fermi surface as the Neel phase is suppressed. As well as revealing the existence of fluctuations deep within the antiferromagnetic phase, these data suggest that a possible new type of quantum critical point may exist in strong magnetic fields that involves only parts of the Fermi surface.

457

EMF effects on microcirculatory system

Abstract Authors review the importance of studying the effects of electromagnetic fields (EMF) on microcirculatory system, especially in respect of possibility that vasculature may have direct and indirect role in interaction of static magnetic fields (SMF). We outline the physiological importance of microcirculation and relatively new methods of evaluation technique in vivo and explain in details the local and/or whole body exposure effects of SMF with range of 0.3–180 mT, power frequency EMF with range of 0.1–30 mT and microwaves at 1.5 GHz with range 0.08–8 W/kg brain average specific absorption rate (SAR) on microcirculatory systems in different tissues in experimental animals.

458

EMF signals and ion/ligand binding kinetics: prediction of bioeffective waveform parameters

The kinetics of an electromagnetic field (EMF) target pathway are used to estimate frequency windows for EMF bioeffects. Ion/ligand binding is characterized via first order kinetics from which a specific electrical impedance can be derived. The resistance/capacitance properties of the binding pathway impedance, determined by the kinetics of the rate-determining step, define the frequency range over which the target pathway is most sensitive to external EMF. Applied signals may thus be configured such that their spectral content closely matches that of the target, using evaluation of the signal to thermal noise ratio to optimize waveform parameters. Using the approach proposed in this study, a pulsed radio frequency (PRF) waveform, currently employed clinically for soft tissue repair, was returned by modulation of burst duration, producing significant bioeffects at substantially reduced signal amplitude. Application is made to Ca2+/Calmodulin-dependent myosin phosphorylation, for which the binding time constants may be estimated from reported kinetics, neurite outgrowth from embryonic chick dorsal root explants and bone repair in a fracture model. The results showed that the retuned signal produced increased phosphorylation rates, neurite outgrowth and biomechanical strength that were indistinguishable from those produced by the clinical signal, but with a tenfold reduction in peak signal amplitude, approximately 800-fold reduction in average amplitude and approximately 10(6)-fold reduction in average power.

459

Endothelial cell response to pulsed electromagnetic fields: stimulation of growth rate and angiogenesis in vitro

The effects of pulsed electromagnetic fields on the repopulation rate of denuded regions of endothelial cell monolayers and on endothelial cell reorganization into complex vessellike structures was monitored in vitro by using human umbilical vein and bovine aortic endothelial cells. A small (20-40%) but statistically significant enhancement in growth rate of partially denuded endothelial cell monolayers as determined by tritiated thymidine incorporation was observed in the presence of pulsed electromagnetic fields. Morphologically, endothelial cells entering the denuded regions were observed to be elongated, often connecting end to end to form a mycelial or "sprouting" pattern when exposed to pulsed electromagnetic fields. This was in contrast to cells outside of the field which had a more cuboidal morphology. Complete disruption of the endothelial cell monolayer by passaging the cells with EDTA-trypsin resulted in reorganization of some of the cells into three-dimensional vessellike structures after as little as 5-8 hours in the presence of the pulsed electromagnetic field. This reorganization occurred in the presence of heparin, endothelial cell growth factor, and a competent fibronectin matrix. Vascularization for comparable cultures outside of the field did not occur during the time-course of the experiments. Discrete stages of neovascularization were observed in the presence of the field that were qualitatively similar to stages of angiogenesis observed in vivo.

460

Energetic constraints on the creation of cell membrane pores by magnetic particles

Naturally occurring and contaminant ferromagnetic and ferrimagnetic particles have been found within or near cells, and might allow pulsed magnetic fields to create transient cell membrane opening ("pores"). We show that this possibility is significantly constrained by the maximum rotational energy that can be transferred to the cell membrane. For single biologically synthesized magnetosomes (radius rmag approximately 10(-7) m, magnetic moment mu approximately 2 x 10(-15) A m2) and typical cell membranes, the estimated pulse magnitude must exceed Bo approximately 6 x 10(-3) to 7 x 10(-2) T, and the optimal pulse durations are in the range 10(-5) s < tpulse < 10(-1) s. For larger contaminant particles with larger net magnetic moments, the pulse magnitudes could be only somewhat smaller, and the optimal durations are about the same. Very large pulses that exceed the coercive force of a particle are predicted to have a smaller effective magnitude and shorter effective duration.

461

Enhanced expression of neuronal nitric oxide synthase and phospholipase C-gamma1 in regenerating murine neuronal cells by pulsed electromagnetic field

Pulsed electromagnetic field (PEMF) has been shown to improve the rate of peripheral nerve regeneration. In the present study we investigated the expression of neuronal nitric oxide synthase (nNOS) and phospholipase C-gamma1 (PLC-gamma1) in regenerating rat laryngeal nerves during the exposure to PEMF after surgical transection and reanastomosis. Axons were found to regenerate into the distal stump nearly twice faster in PEMF-exposed animals than in the control. Consistently, motor function was better recovered in PEMF-treated rats. The expression of nNOS and PLC-gamma1 was highly enhanced in the regenerated nerves.

462

Enhanced hypnotizability by cerebrally applied magnetic fields depends upon the order of hemispheric presentation: an anistropic effect

A significant alteration in the hypnotizability of normal subjects after brief (15 min) exposures to weak (1 microT) pulsed magnetic fields over the temporal lobes was determined by the serial order of hemispheric stimulation. Only subjects who received the right hemispheric stimulation first displayed significantly elevated hypnosis induction profile scores (effect size equivalent to a correlation of 0.41). Implications for a technology that can: a) modify hypnotizability, b) encourage the consolidation of quasiexperiences that are reconstructed as autobiographical memory, and c) change the sense of self, are discussed.

463

Enhanced potency of daunorubicin against multidrug resistant subline KB-ChR-8-5-11 by a pulsed magnetic field

Tumor cell resistance to many unrelated anticancer drugs is a major obstacle during cancer chemotherapy. One mechanism of drug resistance is thought to be due to the efflux of anticancer drugs caused by P-glycoprotein. In recent years, magnetic fields have been found to enhance the potency of anticancer drugs, with favorable modulation of cancer therapy. In this study, KB-ChR-8-5-11, a multidrug resistant (MDR) human carcinoma subline, was used as a model to evaluate the ability of pulsed magnetic fields (PMF) to modulate the potency of daunorubicin (DNR) in vivo and to determine the appropriate order of exposure to drugs and PMF using an in vitro cytotoxicity assay. Solenoid coils with a ramped pulse current source were used at 250 pulses per second for both in vivo and in vitro experiments. For the in vivo study, KB-ChR-8-5-11 cells were inoculated into thymic Balbc-nu/nu female mice. Treatment was begun when the average tumor volume reached 250-450 mm3. Treatment consisted of whole body exposure to PMF for one hour, followed immediately by intravenous (i.v.) injection of 8 mg/kg DNR designated as day 0, and repeated on days 7 and 14. Among the various groups, significant differences in the tumor volume were found between PMF + saline and PMF + DNR groups (p = 0.0107) at 39 days and 42 days (p = 0.0101). No mice died in the PMF alone group, and no toxicity attributable to PMF was found during the experimental period. For the in vitro studies, the sulforhodamine blue (SRB) cytotoxicity assay was used to determine the effect of the sequence which cells are exposed to PMF and/or DNR. Cells were exposed to PMF either before (pre-PMF) or after (post-PMF) drug was added. Results showed that the IC50 was significantly different between controls and pre-PMF + DNR groups (P = 0.0096, P = 0.0088). The IC50 of the post-PMF + DNR group was not found to be significantly different from control groups. Thus, the data in this report demonstrates that PMF enhanced the potency of DNR against KB-ChR-8-5-11 xenograft in vivo, while the efficacy of DNR was potentiated in vitro by PMF exposure only when PMF exposure occurred in the presence of drug. The data in vitro suggest that the mechanism by which PMFs modulate DNR's potency may be by inhibition of the efflux pump, P-glycoprotein. Further work to determine conditions for maximum modulation of drug potency by PMFs is warranted.

464

Enhanced power within a specific band of theta activity in one person while another receives circumcerebral pulsed magnetic fields: a mechanism for cognitive influence at a distance?

Four pairs of adult siblings served once as either the stimulus or the response person in two sessions separated by one week. While the brain of the stimulus person, who was seated in a closed chamber, was exposed successively to six different complex magnetic fields for 5 min. each quantitative monopolar electroencephalographic measurements over the frontal, temporal, parietal, and occipital lobes were collected by computer for the response person who was seated in another room. The six configurations of fields served as different stimulus patterns and had been designed to affect consciousness. As predicted theoretically, a significant increase in electroencephalographic power within the 5.0-Hz to 6.0-Hz band over the frontal and occipital lobes was noted for the response persons when the stimulus persons received one of the six specific patterns of weak (1 microTesla range) magnetic fields. This magnetic stimulus was presented for 100 msec. with changes in rate of 20 msec. to each of the eight solenoids that were equally spaced in the horizontal plane around the head of the stimulus person. Derivatives within this narrow frequency band had been hypothesized to be a source of the "binding factor" for the cohesive cerebrogenic electromagnetic fields producing consciousness. The results suggest that an appropriate altered state of one brain can effect specific predictable frequencies of the electroncephalographic activity of another distant brain which is genetically related.

465

Enhanced responsiveness to parathyroid hormone and induction of functional differentiation of cultured rabbit costal chondrocytes by a pulsed electromagnetic field

Pulsed electromagnetic fields promote healing of delayed united and ununited fractures by triggering a series of events in fibrocartilage. We examined the effects of a pulsed electromagnetic field (recurrent bursts, 15.4 Hz, of shorter pulses of an average of 2 gauss) on rabbit costal chondrocytes in culture. A pulsed electromagnetic field slightly reduced the intracellular cyclic adenosine 3',5'-monophosphate (cAMP) level in the culture. However, it significantly enhanced cAMP accumulation in response to parathyroid hormone (PTH) to 140% of that induced by PTH in its absence, while it did not affect cAMP accumulation in response to prostaglandin E1 or prostaglandin I2. The effect on cAMP accumulation in response to PTH became evident after exposure of the cultures to the pulsed electromagnetic field for 48 h, and was dependent upon the field strength. cAMP accumulation in response to PTH is followed by induction of ornithine decarboxylase, a good marker of differentiated chondrocytes, after PTH treatment for 4 h. Consistent with the enhanced cAMP accumulation, ornithine decarboxylase activity induced by PTH was also increased by the pulsed electromagnetic field to 170% of that in cells not exposed to a pulsed electromagnetic field. Furthermore, stimulation of glycosaminoglycan synthesis, a differentiated phenotype, in response to PTH was significantly enhanced by a pulsed electromagnetic field. Thus, a pulsed electromagnetic field enhanced a series of events in rabbit costal chondrocytes in response to PTH. These findings show that exposure of chondrocytes to a pulsed electromagnetic field resulted in functional differentiation of the cells.

466

Enhancement of functional recovery following a crush lesion to the rat sciatic nerve by exposure to pulsed electromagnetic fields

Previous studies showed that exposure to pulsed electromagnetic fields (PEMF) produced a 22% increase in the axonal regeneration rate during the first 6 days after crush injury in the rat sciatic nerve. We used the same injury model to assess the effect on functional recovery. The animals were treated with whole body exposure to PEMF (0.3 mT, repetition rate 2 Hz) for 4 h/day during Days 1-5 while held in plastic restrainers. Functional recovery was serially assessed up to Postinjury Day 43 using recently described video imaging of the 1-5 toe spread and the gait-stance duration. Footprint analysis was also used with calculation of a sciatic function index. Those animals treated with PEMF had improved functional recovery, as compared to sham controls, using the tests for video 1-5 toe spread and gait-stance duration (P = 0.001 and P = 0.081, respectively). This effect was found throughout the 43-day recovery period. No effect was found using the sciatic function index. This study confirms that functional recovery after nerve crush lesion is accelerated by PEMF and has broad implications for the clinical use of these fields in the management of nerve injuries.

467

Enhancement of the cell-killing effect of ultraviolet-C radiation by short-term exposure to a pulsed magnetic field

PURPOSE: To investigate whether low frequency pulsed magnetic field (PMF) exposures produce alterations in the cell killing induced by ultraviolet C (UVC) radiation. MATERIALS AND METHODS: MCF-7 breast cancer cells of exponentially growing cultures were exposed to PMF (25 Hz, 0.75 mT) and UVC (from 6.6 J/m2 to 59.4 J/m2) in two different protocols: (a) cells were exposed to PMF for 30 min and then exposed to UVC at different doses; (b) cells were exposed to PMF for 30 min. After 15 min of the PMF exposure they were exposed simultaneously to PMF+different doses of UVC. After an additional time of 72 h of incubation, viability was measured by the neutral red stain cytotoxicity test. RESULTS: Both exposure protocols produced a significant decrease in the post UVC survival at 13.2 J/m2 and 19.8 J/m2, as compared to controls. The simultaneous exposition of PMF and UVC produced an additional increment in cell killing at 26.4 J/m2, being the greater effects obtained for this second exposure protocol. CONCLUSIONS: Results of the present study show that PMF in combination with UVC have the ability to augment the cell killing effects of UVC radiation. In addition, the effects appear to be greater when PMF and UVC are applied at the same time.

468

Enhancement of the efficiency of non-viral gene delivery by application of pulsed magnetic field

New approaches to increase the efficiency of non-viral gene delivery are still required. Here we report a simple approach that enhances gene delivery using permanent and pulsating magnetic fields. DNA plasmids and novel DNA fragments (PCR products) containing sequence encoding for green fluorescent protein were coupled to polyethylenimine coated superparamagnetic nanoparticles (SPIONs). The complexes were added to cells that were subsequently exposed to permanent and pulsating magnetic fields. Presence of these magnetic fields significantly increased the transfection efficiency 40 times more than in cells not exposed to the magnetic field. The transfection efficiency was highest when the nanoparticles were sedimented on the permanent magnet before the application of the pulsating field, both for small (50 nm) and large (200-250 nm) nanoparticles. The highly efficient gene transfer already within 5 min shows that this technique is a powerful tool for future in vivo studies, where rapid gene delivery is required before systemic clearance or filtration of the gene vectors occurs.

469

Entanglement and dynamics of spin chains in periodically pulsed magnetic fields: accelerator modes

We study the dynamics of a single excitation in a Heisenberg spin-chain subjected to a sequence of periodic pulses from an external, parabolic, magnetic field. We show that, for experimentally reasonable parameters, a pair of counterpropagating coherent states is ejected from the center of the chain. We find an illuminating correspondence with the quantum time evolution of the well-known paradigm of quantum chaos, the quantum kicked rotor. From this we can analyze the entanglement production and interpret the ejected coherent states as a manifestation of the so-called "accelerator modes" of a classically chaotic system.

471

Epidemiology of fibromyalgia

Chronic widespread pain, the cardinal symptom of fibromyalgia (FM), is common in the general population, with comparable prevalence rates of 7.3% to 12.9% across different countries. The prevalence of FM in the general population was reported to range from 0.5% to 5% and up to 15.7% in the clinic. The common association of FM with other rheumatic disorders, chronic viral infections, and systemic illnesses has been well documented in several studies. Up to 65% of patients with systemic lupus erythematosus meet the criteria for FM. FM is considered a member of the family of functional somatic syndromes. These syndromes are very common and share a similar phenomenology, epidemiologic characteristics, high rates of occurrence, a common pathogenesis, and similar management strategies. A high prevalence of FM was demonstrated among relatives of patients with FM and it may be attributed to genetic and environmental factors.

472

Essential oils and low-intensity electromagnetic pulses in the treatment of androgen-dependent alopecia

This double-blind randomized study vs placebo in healthy male and female volunteers demonstrates the positive biologic effect on hair loss and hair regrowth of a pulsed electromagnetic field in combination with essential oils administered according to a regular treatment schedule of 26 weeks. Mean hair count comparisons within the groups significantly favor the treatment group, which exhibited a decrease in hair loss in 83% of the volunteers and a more than 20% hair count increase over baseline in 53% of patients. The process exhibited no side effects or untoward reactions. The histologic examination correlated with the clinical study. A parallel immunohistochemical examination showed an increase in the proliferation index, and when the expression of Ki67 (a cell proliferation marker) is increased, the mitoses are barely visible in the histologic examination. The rationale of this phenomenon is considered to be due to an electrophysiologic effect on the quiescent hair follicle.

473

Evaluation of electromagnetic enhancement of surface enhanced hyper Raman scattering using plasmonic properties of binary active sites in single Ag nanoaggregates

We found a binary active site of surface enhanced Raman scattering (SERS) and surface enhanced hyper Raman scattering (SEHRS) in single Ag nanoaggregates by single particle spectroscopy. The intensity fluctuation of SEHRS was canceled by dividing SEHRS intensity by SERS intensity on the basis of the binary active site analysis. Thanks to the identification of the plasmons common to both SERS and SEHRS we revealed that an enormous enhancement in SEHRS is ascribed to the electromagnetic (EM) enhancement entirely coupled with longitudinal plasmon modes excluding other kinds of enhancement factors. Our results indicate that EM enhancement factors of metal nanostructures are estimated from spectral information on the longitudinal plasmon resonance band obtained by the scattering or absorption spectra of the nanostructures.

474

Evaluation of hormonal change, biochemical parameters, and histopathological status of uterus in rats exposed to 50-Hz electromagnetic field

This study investigates the effects of the electromagnetic field (EMF) resulting from the 170 kV high-voltage power lines on hormonal status, on progesterone and 17-beta estradiol levels, and on morphology of the uterus and ovaries associated with biochemical parameters of adult Wistar female rats. The rats were assigned to experimental (21) and control groups (7). The rats in the experimental group were housed in a wooden barn with 7.5 m vertical distance to the power line. Groups 1, 2, and 3 were exposed continuously (24 h) to electric-electromagnetic fields (ELF-EMFs) (48.21 +/- 1.58 mG) for 1, 2, and 3 months, respectively. The rats of group 4 served as the control and were placed in laboratory conditions (The average value of the ELF was 0.75 +/- 0.05 V/m. The value of the EMF was calculated to be 0.48 +/- 0.05 mG.). Significant (P < 0.05) decreases were determined among the groups in terms of reproductive organ weights (uterus and ovaries) and progesterone and estrogen levels in relation to the varying periods of the estrous cycle. Although marked reductions (P < 0.05) were observed among the groups in relation to plasma catalase activity, depending on exposure time, no significant differences were found in terms of glutathione and malondialdehyde levels. It is concluded that exposure to the ELF-EMFs for different time periods produced significant decreases in plasma catalase activities in the 3-month exposure groups but no effects on progesterone level, on 17-beta estradiol level, or on the morphology and weight of uterus and ovaries.

475

Evaluation of potential genotoxicity of pulsed electric and electromagnetic fields used for bone growth stimulation

Medical devices emitting pulsed electric and electromagnetic fields have been found to be effective for a number of clinical applications including stimulation of bone and tissue growth. To determine whether pulsed fields of the type used in these clinical applications present a mutagenic hazard, electric and electromagnetic fields at two exposure levels were tested in the Ames test, CHO cell chromosomal aberration assay, BALB/3T3 cell transformation assay and unscheduled DNA synthesis assay in primary rat hepatocytes. For both field types, initial and independent repeat studies were performed for each assay at both clinical and supra clinical doses. In all assays, the results show a lack of cytotoxic, transforming and mutagenic activity. The data suggest that pulsed electric and electromagnetic fields of the type and dose levels used in bone growth stimulation lack mutagenic and transforming activity.

476

Evaluation of stray radiofrequency radiation emitted by electrosurgical devices

Electrosurgery refers to the passage of a high-frequency, high-voltage electrical current through the body to achieve the desired surgical effects. At the same time, these procedures are accompanied by a general increase of the electromagnetic field in an operating room that may expose both patients and personnel to relatively high levels of radiofrequency radiation. In the first part of this study, we have taken into account the radiation emitted by different monopolar electrosurgical devices, evaluating the electromagnetic field strength delivered by an electrosurgical handle and straying from units and other electrosurgical accessories. As a summary, in the worst case a surgeon's hands are exposed to a continuous and pulsed RF wave whose magnetic field strength is 0.75 A m(-1) (E-field 400 V m(-1)). Occasionally stray radiation may exceed ICNIRP's occupational exposure guidelines, especially close to the patient return plate. In the second part of this paper, we have analysed areas of particular concern to prevent electromagnetic interference with some life-support devices (ventilators and electrocardiographic devices), which have failed to operate correctly. Most clinically relevant interference occurred when an electrosurgery device was used within 0.3 m of medical equipment. In the appendix, we suggest some practical recommendations intended to minimize the potential for electromagnetic hazards due to therapeutic application of RF energy.

477

Evaluation of the effects of extremely low frequency electromagnetic fields on mammalian follicle development

The aim of this study was to evaluate the effects of pulsed, extremely low-frequency electromagnetic fields (ELF-EMF) on in-vitro mouse pre-antral follicle development. Pre-antral follicles were cultured for 5 days and exposed to ELF-EMF at the frequencies of 33 or 50 Hz. ELF-EMF application did not affect follicular growth over a 3 day culture period, but on day 5 the growth of 33 Hz-exposed follicles was significantly reduced when compared with controls, while the 50 Hz-exposed follicles were not significantly affected. However, ELF-EMF severely impaired antrum formation at both frequencies, as 79 +/- 3% of control follicles developed antral cavities compared with 30 +/- 6% and 51.6 +/- 4% of 33 or 50 Hz-exposed follicles respectively. The follicles with failed antrum formation showed lower oestradiol release and granulosa cell DNA synthesis, but these effects were not related to granulosa cell apoptosis. Furthermore, a high percentage of the in-vitro grown oocytes obtained from exposed follicles had a reduced ability to resume meiotic maturation when compared with controls. These results suggest that ELF-EMF exposure might impair mammalian female reproductive potentiality by reducing the capacity of the follicles to reach a developmental stage that is an essential pre-requisite for reproductive success.

478

Evaluation of the maximum permissible level of low-intensity electromagnetic radiation at mobile connection frequency (1 GHz) by changes in motor activity of Spirostomum Ambiguum

Electromagnetic radiation at the mobile connection frequency (1 GHz) at maximum energy flow density (10 microW/cm(2)) permitted in Russia causes serious functional disorders in the studied unicellular hydrobionts infusoria Spirostomum ambiguum: reduction of their spontaneous motor activity. The form of biological reaction is uncommon: the effect is threshold, overall, and does not depend on the duration of microwave exposure.

479

Evaluation of treatment by pulsed electromagnetic fields in a rabbit hyphema model

PURPOSE: Previous clinical studies have suggested a positive effect of low-frequency pulsed electromagnetic fields (PEMF) on wound healing and inflammation in the eye. We tried to test the value of PEMF treatment in a hyphema animal model with well-defined conditions. METHODS: After injection of citrated autologous blood for the production of hyphema, 16 rabbit eyes were treated with 10 or 20 mT for 60 min on 4 days within the postoperative week. Two control groups with hyphema alone (n = 8) and PEMF irradiation without hyphema (n = 4) were also included. The rate of resorption was recorded daily. Histopathologic evaluation was performed. RESULTS: The incidence of endothelial cell damage and fibrotic clots was markedly reduced in the 10-mT group while the resorption time of 8 days was identical with the control group. In the 20-mT group, the complication rate and the resorption time was increased versus the control group. CONCLUSIONS: The use of PEMF treatment is of some, however, limited value as it did not reduce the resorption time of hyphema but displayed a dose-dependent, beneficial influence on some serious side effects. Future clinical studies with low-dose PEMF irradiation are justified and should determine the optimal dosage and suitable indications of PEMFs as an adjunctive treatment in ocular inflammation or trauma.

480

Evaluation of treatment with a pulsed electromagnetic field on wound healing, clinicopathologic variables, and central nervous system activity of dogs

OBJECTIVE: To evaluate effects of treatment with a pulsed electromagnetic field (PEMF) on healing of open and sutured wounds, clinicopathologic variables, and CNS activity of dogs. ANIMALS: 12 adult female Beagles. PROCEDURE: Open and sutured wounds were created in the skin of the trunk of the dogs. Dogs were divided into 2 groups. One group received PEMF treatment and 1 group served as untreated (control) dogs. The PEMF-treated dogs received treatment twice a day starting the day before surgery and lasting through day 21 after surgery. Wounds were evaluated by use of tensiometry, planimetry, laser Doppler perfusion imaging, and histologic examination. Clinicopathologic variables and electroencephalographic tracings were also evaluated. RESULTS: Use of PEMF treatment resulted in significantly enhanced epithelialization of open wounds 10 and 15 days after surgery. Five days after surgery, wounds of control dogs had a negative value for wound contraction, whereas PEMF-treated wounds had a positive value. The PEMF treatment did not cause significant changes in short-term planimetric, perfusion, tensiometric, histologic, clinicopathologic, or electroencephalographic results. CONCLUSIONS: The PEMF treatment enhanced wound epithelialization in open cutaneous wounds and provided indications of early contraction without significant short-term changes in other variables.

481

Evidence for an effect of ELF electromagnetic fields on human pineal gland function

A study was carried out to determine possible effects of 60-Hz electromagnetic-field exposure on pineal gland function in humans. Overnight excretion of urinary 6-hydroxymelatonin sulfate (6-OHMS), a stable urinary metabolite of the pineal hormone melatonin, was used to assess pineal gland function in 42 volunteers who used standard (conventional) or modified continuous polymer wire (CPW) electric blankets for approximately 8 weeks. Volunteers using conventional electric blankets showed no variations in 6-OHMS excretion as either a group or individuals during the study period. Serving as their own controls, 7 of 28 volunteers using the CPW blankets showed statistically significant changes in their mean nighttime 6-OHMS excretion. The CPW blankets switched on and off approximately twice as often when in service and produced magnetic fields that were 50% stronger than those from the conventional electric blankets. On the basis of these findings, we hypothesize that periodic exposure to pulsed DC or extremely low frequency electric or magnetic fields of sufficient intensity and duration can affect pineal gland function in certain individuals.

482

Evidence of electroconformational changes in membrane proteins: field-induced reductions in intra membrane nonlinear charge movement currents

Experimental results are presented to show that a pulsed, intensive membrane potential can reduce intra membrane, nonlinear charge movement currents, which are the voltage-sensors in the voltage-dependent membrane proteins and in the excitation-contraction coupling of skeletal muscle fibers. The results indicate a possible mechanism involved in electrical injury: dysfunctions of the voltage-dependent membrane proteins caused by electroconformational damages in their voltage-sensors.

483

Evidence of red cell alignment in the magnetic field of an NMR spectrometer based on the diffusion tensor of water

The alignment of human erythrocytes in aqueous suspensions in the magnetic field B(0) (called the z-direction) of an NMR spectrometer was shown by calculating the diffusion tensor for water in the sample. The diffusion was measured using a pulsed-field-gradient spin-echo NMR method. The extent of diffusion anisotropy for water was exemplified by the values of the apparent diffusion coefficients with erythrocytes of normal shape and volume: for a typical experiment the values for the x-, y-, and z-directions were (6.88 +/- 0.17) x 10(-10), (7.07 +/- 0.17) x 10(-10), and (10.20 +/- 0.17) x 10(-10) m(2) s(-1), respectively. Cells in hypo- and hyperosmotic media were also studied and they too showed the anisotropy of the apparent diffusion coefficients but the extents were different. A new method of data analysis was developed using the Standard Add-On Packages in a Mathematica program. The experimental findings support evidence of erythrocyte alignment that was previously obtained with a high-field-gradient q-space method.

484

Evidence that pulsed electromagnetic fields inhibit coupling of adenylate cyclase by parathyroid hormone in bone cells

To investigate the biochemical effects of pulsed electromagnetic fields (PEMF) on bone in particular and on cell membrane-associated activity in general, we have studied the modification by PEMF of cAMP metabolism in primary calvarial bone cells. We report that PEMF inhibited cAMP accumulation stimulated by bovine PTH(1-34) peptide. After a 1-hr PEMF exposure, the cAMP response to PTH (2-7 min) was decreased in exposed cells to 48-70% (p less than 0.05) of the response of unexposed cells; furthermore, this inhibition disappeared after 10-20 min with PTH. This inhibition occurred at submaximal PTH doses (2.4-7.3 nM) and no effect was observed at maximal PTH doses (24 nM). Thus with PEMF, the dose response curve for PTH became 0.5 log unit less sensitive. PEMF did not affect the cAMP response to cholera toxin and forskolin. However, when submaximal doses of both forskolin (0.5-1.0 microM) and PTH (0.24-2.4 nM) were used, forskolin prevented inhibition of cAMP production by PEMF in the range of fields and stimulus epochs which normally inhibit cAMP production. It is proposed that PEMF inhibits PTH-stimulated coupling of the adenylate cyclase system and that this inhibition does not affect the intrinsic activity of the G-protein and the catalytic subunit.

485

Evidence-based use of pulsed electromagnetic field therapy in clinical plastic surgery

Background: The initial development of pulsed electromagnetic field (PEMF) therapy and its evolution over the last century for use in clinical surgery has been slow, primarily because of lack of scientifically-derived, evidence- based knowledge of the mechanism of action. Objective: Our objective was to review the major scientific breakthroughs and current understanding of the mechanism of action of PEMF therapy, providing clinicians with a sound basis for optimal use. Methods: A literature review was conducted, including mechanism of action and biologic and clinical studies of PEMF. Using case illustrations, a holistic exposition on the clinical use of PEMF in plastic surgery was performed. Results: PEMF therapy has been used successfully in the management of postsurgical pain and edema, the treatment of chronic wounds, and in facilitating vasodilatation and angiogenesis. Using scientific support, the authors present the currently accepted mechanism of action of PEMF therapy. Conclusions: This review shows that plastic surgeons have at hand a powerful tool with no known side effects for the adjunctive, noninvasive, nonpharmacologic management of postoperative pain and edema. Given the recent rapid advances in development of portable and economical PEMF devices, what has been of most significance to the plastic surgeon is the laboratory and clinical confirmation of decreased pain and swelling following injury or surgery. (Aesthetic Surg J 2009;29:135–143.)

486

Exact and approximative imaging methods for photoacoustic tomography using an arbitrary detection surface

Two universal reconstruction methods for photoacoustic (also called optoacoustic or thermoacoustic) computed tomography are derived, applicable to an arbitrarily shaped detection surface. In photoacoustic tomography acoustic pressure waves are induced by illuminating a semitransparent sample with pulsed electromagnetic radiation and are measured on a detection surface outside the sample. The imaging problem consists in reconstructing the initial pressure sources from those measurements. The first solution to this problem is based on the time reversal of the acoustic pressure field with a second order embedded boundary method. The pressure on the arbitrarily shaped detection surface is set to coincide with the measured data in reversed temporal order. In the second approach the reconstruction problem is solved by calculating the far-field approximation, a concept well known in physics, where the generated acoustic wave is approximated by an outgoing spherical wave with the reconstruction point as center. Numerical simulations are used to compare the proposed universal reconstruction methods with existing algorithms.

487

Exact temporal eddy current compensation in magnetic resonance imaging systems

A step-response method has been developed to extract the properties (amplitudes and decay time constants) of intrinsic-eddy-current-sourced magnetic fields generated in whole-body magnetic resonance imaging systems when pulsed field gradients are applied. Exact compensation for the eddy-current effect is achieved through a polynomial rooting procedure and matrix inversion once the 2 N properties of the N-term decay process are known. The output of the inversion procedure yields the required characteristics of the filter for spectrum magnitude and phase equalization. The method is described for the general case along with experimental results for one-, two-, and three-term inversions. The method's usefulness is demonstrated for the usually difficult case of long-term (200-1000-ms) eddy-current compensation. Field-gradient spectral flatness measurements over 30 mHz-100 Hz are given to validate the method.

488

Excitation of ion-wave wakefield by the resonant absorption of a short pulsed microwave with plasma

Unmagnetized, inhomogeneous laboratory plasma irradiated by a high power (eta=E(2)(0)/4pin(e)kT(e) approximately 5.0x10(-2)) short pulsed microwave with pulse length of the order of ion-plasma period (tau(pi) less, similar 2pi/omega(pi)) is studied. Large density perturbation traveling through the underdense plasma with a velocity much greater than the ion sound speed produced by the resonant absorption of the microwave pulse has been observed. In the beginning the density perturbation has large amplitude (deltan/n(0) approximately 40%) and propagates with a velocity of the order of 10(6) cm/s. But later its amplitude as well as the velocity decrease rapidly, and finally the velocity arrives with twice the ion sound speed. The oscillating incident electromagnetic waves enhance highly localized electric field by the resonant absorption process and develop time-averaged force field which pushes plasma electrons from the resonant layer. As the electrons are accelerated to be ejected, they pull plasma ions as a bunch with them by means of self-consistent Coulomb force. This suprathermal ion bunch can excite an ion-wave wakefield.

489

Expanding use of pulsed electromagnetic field therapies

Various types of magnetic and electromagnetic fields are now in successful use in modern medicine. Electromagnetic therapy carries the promise to heal numerous health problems, even where conventional medicine has failed. Today, magnetotherapy provides a non invasive, safe, and easy method to directly treat the site of injury, the source of pain and inflammation, and a variety of diseases and pathologies. Millions of people worldwide have received help in treatment of the musculoskeletal system, as well as for pain relief. Pulsed electromagnetic fields are one important modality in magnetotherapy. Recent technological innovations, implementing advancements in computer technologies, offer excellent state-of-the-art therapy.

490

Experimental and numeric investigation about electromagnetic interference between implantable cardiac pacemaker and magnetic fields at power line frequency

The present contribute describes the investigation about the implantable pacemaker (PM) immunity against high level magnetic interfering fields at 50 Hz that a pacemaker wearer could find in his working environment. To this purpose, a test bench has been set up based on a Helmholtz coil for producing extremely low frequency (ELF) magnetic fields and a heart simulator rightly fed by electric signals that simulate atrium and ventricle signals. A widely diffused PM has been tested, under different operation modes and configurations, for both continuous interfering waves (CW) and variously pulsed interfering waves (PW). Pertaining the obtained results, high levels of CW field, only in unipolar mode, produce a behaviour called 'asynchronous mode' (not dangerous). For PW fields, under particular and rare conditions, the complete inhibition occurred (the most dangerous effect for PM wearer). In order to validate experimental results, a numerical 3-D model has been developed to simulate the whole bench system formed by Helmholtz coil, human trunk, pacemaker case and its electric leads. In this model the electromagnetic problem is solved by reconstructing the inhomogeneous bench system associating the relative values of conductivity to each cubic cell in which the whole system is discretized. Application of Maxwell's equations in their integral form has allowed to obtain a 3-D electrical network, whose solution gives the current density distribution inside the heart simulator.

492

Experimental facilitation of the sensed presence: possible intercalation between the hemispheres induced by complex magnetic fields

This experiment was designed to test the hypothesis that the sensed presence, the feeling of a proximal sentient being, can be evoked within the laboratory. Under double-blind conditions, 48 university men and women were exposed to weak (100 nT to 1 muT), complex, pulsed magnetic fields that were applied primarily over the right temporoparietal region, primarily over the left temporoparietal region, or equally across both hemispheres (one treatment per group) for 20 minutes while wearing opaque goggles in a very quiet room. A fourth group was exposed to a sham-field condition. Subjects who received greater stimulation over the right hemisphere or equal stimulation across both hemispheres reported more frequent incidences of presences, fears, and odd smells than did the subjects who received greater stimulation over the left hemisphere or who were exposed to the sham-field condition. The results suggest that the sensed presence is subject to experimental manipulation. This experimental procedure could be employed to explore the idea that the experience of a sensed presence is a resident property of the human brain and may be the fundamental source for phenomena attributed to visitations by gods, spirits, and other ephemeral phenomena.

493

Experimental investigation of stochastic pulsation and formation of light bullets with megagauss magnetic fields by an intense laser pulse propagating in a preionized plasma

The generation of extremely stable light bullets in a preformed plasma near critical density has been observed experimentally during the interaction of intense picosecond laser beam with a metallic target in air. Optical probing measurements indicate the formation of pulsating channels, typically of about 5 microm in diameter, directed towards a heating laser beam, as well as of disconnected massive plasma blocks moving also towards the laser beam. The velocities of the dense plasma blocks reach the values of 4.5x10(8) cm/s. The blocks are stable during their acceleration and propagation in air. Self-generated magnetic fields up to 4-7 MG were observed by means of the Faraday rotation of a probe laser beam.

494

Experimental regeneration in peripheral nerves and the spinal cord in laboratory animals exposed to a pulsed electromagnetic field

Peripheral nerve section and suture was performed in 132 rats. Postoperatively half the animals were exposed to a pulsed electromagnetic field each day and half were kept as controls. Nerve conduction studies, histology and nerve fibre counts all indicated an increased rate of regeneration in the treated animals. A similar controlled study of spinal cord regeneration following hemicordotomy in cats has been started, and preliminary results indicate that when the animals are sacrificed three months after the hemicordotomy, the pulsed electromagnetic therapy has induced nerve fibre regeneration across the region of the scar.

495

Exploring the use of natural antimicrobial agents and pulsed electric fields to control spoilage bacteria during a beer production process

Different natural antimicrobials affected viability of bacterial contaminants isolated at critical steps during a beer production process. In the presence of 1 mg/ml chitosan and 0.3 mg/ml hops, the viability of Escherichia coli in an all malt barley extract wort could be reduced to 0.7 and 0.1% respectively after 2 hour- incubation at 4 degrees C. The addition of 0.0002 mg/ml nisin, 0.1 mg/ml chitosan or 0.3 mg/ml hops, selectively inhibited growth of Pediococcus sp. in more than 10,000 times with respect to brewing yeast in a mixed culture. In the presence of 0.1 mg ml chitosan in beer, no viable cells of the thermoresistant strain Bacillus megaterium were detected. Nisin, chitosan and hops increased microbiological stability during storage of a local commercial beer inoculated with Lactobacillus plantarum or Pediococcus sp. isolated from wort. Pulsed Electric Field (PEF) (8 kV/cm, 3 pulses) application enhanced antibacterial activity of nisin and hops but not that of chitosan. The results herein obtained suggest that the use of these antimicrobial compounds in isolation or in combination with PEF would be effective to control bacterial contamination during beer production and storage.

496

Exposure of C3H/Bi female mice with mammary carcinoma to pulsed magnetic fields

Pulsed magnetic fields (PMF) have already proved to have a certain influence not only on leucocytes in vitro but also on thymocytes in vivo. C3H/Bi tumoral female mice were either exposed to 12 Hz or 460 Hz, and to 6, 9 or 20 mT PMF just two weeks after the tumors had appeared and this until the moment they died. Actually, all the survival times as well as the average weights of spleens lungs, and tumors were then taken into account at the very death of the mice. In a general way there happened to be no difference in spite of the different frequencies used and the rates of lungs with metastases were not at all influenced by the exposure itself. However a 3-hour-exposure once a week could increase the mean survival times whereas a 15-minute-exposure to a 6 mT PMF twice a week gave lighter spleens than those of the controls and an exposure either to 9 mT or to 20 mT gave heavier tumors in general.

497

Exposure of mcf-7 breast cancer cells to electromagnetic fields up-regulates the plasminogen activator system

Effects of electromagnetic fields (EMFs) on the incidence of breast cancer (BC) have been proposed by a number of epidemiological studies. The molecular mechanism of the impact of EMFs on cells is not yet clear, although changes in gene expression have been reported in various cellular systems. In this investigation, the interference of low-frequency EMFs with the plasminogen activator system was examined in BC cells.MCF-7 BC cells from 2 different sources were exposed to highly homogeneous 50-Hz EMFs. Changes in gene expression were analyzed by reverse transcriptase-polymerase chain reaction.In MCF-7 cells exposed to 1.2 microT EMF expression of the urokinase plasminogen activator gene and of plasminogen-activator inhibitor-1 was markedly increased. The expression of the receptor for urokinase plasminogen activator was only marginally increased in 1 of the 2 tested cell lines and expression of the tissue plasminogen activator was at least slightly down-regulated in BC cells exposed to EMFs.EMFs may be able to increase the metastatic potential of breast tumors. The use of our newly established exposure system for EMFs may allow us to study the signaling processes involved in the induction of a metastatic phenotype of breast cancer cells.

498

Exposure of mice to pulsed magnetic fields: long-term observations

This work was undertaken to check the effects of 460 Hz pulsed magnetic fields (PMF) on the growth curves of mice, and to observe any possible long term effect. Effects on the growth curves have already been shown in young female AKR mice. Eight-week-old Swiss female mice underwent, until death, a twice weekly a one-hour-exposure to a 460 Hz 6 mT PMF. They initially showed slower than that of the controls, but it later became faster, 460 Hz 9 mT PMF always kept the growth curves of the exposed mice under those of the controls. However, no difference with controls was noticed when the mice were exposed after the thirtieth week. Moreover, there was no difference in the survival or in pathological aspects between the exposed mice and controls.

499

Exposure of mouse preosteoblasts to pulsed electromagnetic fields reduces the amount of mature, type I collagen in the extracellular matrix

We tested the hypothesis that exposure of a mouse preosteoblast cell line to pulsed electromagnetic fields (PEMF) would affect components of the extracellular matrix. We report that exposure of MC3T3-E1 cells to a single PEMF waveform significantly reduced the amount of mature, alpha1(I) collagen in the extracellular matrix (ECM) and the conditioned medium, without affecting the amount of total ECM protein. This decrease was not due to changes in the steady-state level of Col1A1 mRNA or to degradation of mature collagen. We then tested the effect of three distinct PEMF waveforms, two orthogonal coil orientations, and two waveform amplitude levels on the amount of alpha1(I) collagen in the conditioned medium. A sequence of factorial ANOVAs and stepwise regression modeling revealed that the period (duration) of the individual pulses accounted for a significant proportion of the variance associated with the amount of alpha1(I) collagen in the conditioned medium. The total variance accounted for, however, was small (R(2)=0.155, p<0.001 and R(2)=0.172, p<0.001, in the horizontal and vertical orientations, respectively). The positive and negative regression coefficients for the coil orientations revealed that the influence of pulse period was significantly different for the orthogonal coil orientations (p<0.001). The findings imply that the dominant influence of PEMF on the amount of mature, alpha1(I) collagen in the ECM is related to variables other than those expressed in the time-amplitude domain. The results provide objective direction toward identifying waveform characteristics that contribute to the observed between-waveform differences with regard to collagen. Advances in this area may lead toward improving waveforms and waveform delivery protocols.

500

Exposure of murine cells to pulsed electromagnetic fields rapidly activates the mTOR signaling pathway

Murine pre-osteoblasts and fibroblast cell lines were used to determine the effect of pulsed electromagnetic field (PEMF) exposure on the production of autocrine growth factors and the activation of early signal transduction pathways. Exposure of pre-osteoblast cells to PEMF minimally increased the amount of secreted TGF-beta after 1 day, but had no significant effects thereafter. PEMF exposure of pre-osteoblast cells also had no effect on the amount of prostaglandin E(2) in the conditioned medium. Exposure of both pre-osteoblasts and fibroblasts to PEMF rapidly activated the mTOR signaling pathway, as evidenced by increased phosphorylation of mTOR, p70 S6 kinase, and the ribosomal protein S6. Inhibition of PI3-kinase activity with the chemical inhibitor LY294002 blocked PEMF-dependent activation of mTOR in both the pre-osteoblast and fibroblast cell lines. These findings suggest that PEMF exposure might function in a manner analogous to soluble growth factors by activating a unique set of signaling pathways, inclusive of the PI-3 kinase/mTOR pathway.

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