Perspectives of application of anti-CD4 antibodies in the treatment of autoimmune diseases

Escherichia coli JM83 [F- ara delta(lac-proAB) rpsL [phi 80d delta (lacZ)M15]] in midlog growth phase at 30 degrees C were exposed to 60 Hz sinusoidal magnetic field of 3 mT of nonuniform diverging flux, inducing a nonuniform electric field with a maximum intensity of 32 microV/cm using an inductor coil. Exposed and unexposed control cells were maintained at 30.8 +/- 0.1 degrees C and 30.5 +/- 0.1 degrees C, respectively. Quadruplicate samples of exposed and unexposed E. coli cells were simultaneously radiolabeled with 35S-L-methionine at 10 min intervals over 2 hr. Radiochemical incorporation into proteins was analyzed via liquid scintillation counting and by denaturing 12.5% polyacrylamide gel electrophoresis. The results showed that E. coli exposed to a 60 Hz magnetic field of 3 mT exhibited no qualitative or quantitative changes in protein synthesis compared to unexposed cells. Thus small prokaryotic cells (less than 2 microns x 0.5 micron) under constant-temperature conditions do not alter their protein synthesis following exposure to 60 Hz magnetic fields at levels at 3 mT.     

Paraspinal muscle evoked cerebral potentials in patients with unilateral low back pain

Cerebral somatosensory evoked potentials (SEPs) were elicited by magnetic stimulation of paraspinal muscles unilaterally at the L2 and L5 levels in 20 healthy subjects and 16 patients with low back pain and unilateral muscle spasm. A magnetic coil with a mean diameter of 4.7 cm was placed tangentially to the skin. The stimulus strength was sufficient to induce a visible muscle twitch without producing muscle contraction in the legs. The potentials recorded over the scalp consisted of several components (P30, N40, P55, N70, and P90) and were elicited in all subjects. In both healthy and patient subjects, paraspinal muscle evoked potentials were readily elicited. Vibration applied to paraspinal muscles, as well as voluntary contraction of paraspinal muscles, was associated with attenuation of the evoked potentials. This finding suggests that muscle spindle receptors provide the afferent input responsible for the early components of the magnetically evoked cerebral potentials. In patients with unilateral muscle spasm, the amplitudes of P30-N40, N40-P50, and P50-N70 were decreased significantly on the affected side when compared with values on stimulation of the unaffected side, as well as those obtained from control subjects. The cerebral evoked potentials returned to normal amplitude when the muscle spasm subsided following a period of time and after the application of spinal manipulative therapy. The technique has potential for quantitative evaluation of muscle spasm in low back pain.     

Micturition by functional magnetic stimulation in dogs: a preliminary report

The effectiveness of functional magnetic stimulation (FMS) technology on bladder contraction and bladder emptying was evaluated in ten normal neurologically intact male dogs. In seven animals, FMS of the bladder was performed by using a commercially available magnetic coil (non-water-cooled) for stimulating the sacral nerves or over the suprapubic region. With sacral stimulation, the mean change in bladder pressure (Pves) was 68.0 +/- 12.96 cm H2O; with suprapubic stimulation, the mean change in Pves was 40.7 +/- 8.08 cm H2O. This change in Pves by sacral stimulation was higher than suprapubic stimulation (P < 0.01). In three additional animals, voiding was demonstrated by using a specialized water-cooled magnetic coil and by stimulating the sacral nerves with an intermittent stimulation sequence. Voiding occurred in all three animals and was reproducible. In summary, FMS of the bladder has the potential to be a useful non-invasive technology for bladder emptying and bladder training in patients with neurogenic bladder.     

Exposure of female rats to a 100-microT 50 Hz magnetic field does not induce consistent changes in nocturnal levels of melatonin

The hypothesis whereby alternating (50 or 60 Hz) magnetic fields such as those produced by electric power reduce the nocturnal production of melatonin in the pineal gland and thereby indirectly enhance development and growth of breast cancer has attracted a great deal of interest. In view of the potential importance of this hypothesis that there is a link between electric power and breast cancer, which is also known as the "melatonin hypothesis", we undertook various experiments in female Sprague-Dawley rats to evaluate whether 100-microT 50 Hz magnetic-field exposure, i.e. a flux density shown recently to exert a tumor (co)promoting effect in the 7,12-dimethylbenz[a]anthracene (DMBA) model of breast cancer in Sprague-Dawley rats, consistently reduces melatonin levels and, if not, which factors may be involved in the inconsistent effects of magnetic-field exposure on production of melatonin. Long-term exposure of female Sprague-Dawley rats to magnetic fields for 13 weeks did not alter the nocturnal levels of melatonin in the pineal gland or serum (determined 5 h after the onset of darkness) significantly, irrespective of whether rats were treated with DMBA or not. In one experiment, when blood was sampled 3, 5 and 6 h after the onset of darkness after 2 weeks of magnetic-field or sham exposure, a significant decrease in melatonin was seen in magnetic-field-exposed rats at 6 h. However, the results could not be reproduced in two subsequent experiments in other groups of rats. Shorter (1 day, 1 week) or longer (4, 8, 13 weeks) exposure periods also did not result in any significant effects of the magnetic field on melatonin levels when blood sampling was performed either 5 or 6 h after onset of the dark phase. Various potential sources of variation in melatonin levels or in magnetic-field effects on melatonin levels were evaluated, but the reason(s) for the inconsistent effect of magnetic-field exposure remains unclear. Thus the present study failed to demonstrate a consistent effect of 100-microT 50 Hz magnetic-field exposure on melatonin levels in Sprague-Dawley rats.     

Differential roles of p300 and PCAF acetyltransferases in muscle differentiation

To determine the possibility of discriminating multi-sources in the brain by 3D vector magnetic field measurement of a magnetoencephalogram (MEG), measurements were made of magnetic fields produced by two current dipoles implanted in a spherical head model. The 3D vector magnetic field measurements were made by using a 3D second-order gradiometer connected to three rf-SQUIDs, which can detect magnetic field components perpendicular to and tangential to the scalp. The MEG distribution measuring the magnetic field perpendicular to the scalp was not helpful in estimating the location and number of sources because of the lack of a dipole pattern. By referring to the MEG distribution measuring the magnetic field distribution tangential to the scalp, however, two current sources could be clearly discriminated in a spherical head model. It was found that this MEG distribution measuring tangential to the scalp could provide information on new constraint conditions for the calculation of inverse problems with multi-sources. These results were also confirmed by measurement of the mixed somatosensory evoked fields elicited by simultaneous electric stimulation to the median nerve and the thumb.     

A new method for three-dimensional numerical simulation of electromagnetic and fluid-flow phenomena in electromagnetic separation of inclusions from liquid metal

The magnetohydrodynamic (MHD) flow around a suspended particle in a liquid metal subjected to electric and magnetic fields can affect the force exerted by the applied electromagnetic field on the particle. In this article, a novel approach to the computational simulation of three-dimensional nonlinear MHD flow in two-phase systems is proposed. The electromagnetic field in the conducting fluid, including the particle, is represented using the current-vector potential (T) and reduced magnetic scalar potential (Ψ) to avoid the discontinuity of the electric field at the fluid-particle interface. To avoid the solution of the electromagnetic field in free space and to account exactly for the electromagnetic field interactions with the fluid and the particle, the electric and magnetic fields are specified at the boundary of the fluid-flow domain using Ampere’s law. This formulation permits the numerical solution of the coupled electromagnetic and fluid-flow equations on a common mesh. The discretized equations are derived using a finite-element formulation, and an iterative procedure is described for the efficient solution of these equations. This method is used to investigate the electromagnetic and fluid-flow phenomena in electromagnetic separation of a nonconducting spherical particle in crossed uniform electric and magnetic fields at intermediate Hartmann numbers. The computed results show that the magnetic field has no effect on either the velocity field or the net force on the particle when the Hartmann number is less than 1. Beyond this threshold value of the Hartmann number, the velocity decreases almost linearly with increasing magnetic-field strength. The damping of the flow by the magnetic field manifests itself in a reduction of the separation force, even though it is relatively small for this system.     

Functional magnetic stimulation of the respiratory muscles in dogs

This study assessed the ability of functional magnetic stimulation (FMS) to activate the respiratory muscles in dogs. With the animal supine, FMS of the phrenic nerves using a high-speed magnetic stimulator was performed by placing a round magnetic coil (MC) at the carotid triangle. Following hyperventilation-induced apnea, changes in volume (deltaV) and airway pressure (deltaP) against an occluded airway were determined. FMS of the phrenic nerves produced substantial inspired function (deltaV = 373 +/- 20.5 mL and deltaP = -20 +/- 2.0 cm H2O). After bilateral phrenectomies, maximal inspired deltaV (219 +/- 12.2 mL) and deltaP (-10 +/- 1.0 cm H2O) were produced when the MC was placed near the C6-C7 spinous processes, while maximal expired deltaV (-199 +/- 22.5 mL) and deltaP (11 +/- 2.3 cm H2O) were produced following stimulation near the T9-T10 spinous processes. We conclude: (1) FMS of either the phrenic or upper intercostal nerves results in inspired volume production; (2) FMS of the lower intercostal nerves generates expired volume production; and (3) FMS of the respiratory muscles may be a useful noninvasive tool for artificial ventilation and assisted cough in patients with spinal cord injuries or other neurological disorders.     

The early component of the visual evoked magnetic field

Several EEG studies have reported an early component of the visual evoked potential. However, it is controversial whether this component is cortical or subcortical. Our study has aimed to clarify this problem using MEG and EEG in nine normal volunteers. A total of 4000 stimuli were presented to the monocular visual hemifield through a light-proof stimulating goggle and the visual evoked magnetic field and visual evoked potential was measured above the occipital lobe. The early component was observed in three of the nine subjects. The latency ranged from 40 to 45 ms in MEG and from 39 to 47 ms in EEG. The result of dipole localization analysis showed that its origin was cortical, and specifically, the striate cortex.     

Stable magnetic field gradient levitation of Xenopus laevis: toward low-gravity simulation

We have levitated, for the first time, living biological specimens, embryos of the frog Xenopus laevis, using a large inhomogeneous magnetic field. The magnetic field/field gradient product required for levitation was 1430 kG2/cm, consistent with the embryo's susceptibility being dominated by the diamagnetism of water and protein. We show that unlike any other earth-based technique, magnetic field gradient levitation of embryos reduces the body forces and gravity-induced stresses on them. We discuss the use of large inhomogeneous magnetic fields as a probe for gravitationally sensitive phenomena in biological specimens.     

Effects of electromagnetic fields on the levels of biogenic amine metabolites, quinolinic acid, and beta-endorphin in the cerebrospinal fluid of dairy cows

Eight multiparous non-lactating pregnant Holstein cows at 198 +/- 35 d of gestation, weighing 608 +/- 24 kg, were confined to wooden metabolic cages in an electric and magnetic field chamber with a 12:12 h light:dark cycle. Subarachnoidal catheters were installed 5 d before the activation of the electric and magnetic fields. The cows were exposed to electric and magnetic fields (60 Hz, 10 kV/m and 30 microT) continuously except for the feeding and cleaning time for an average of 21.44 +/- 1.4 h per day for a period of 30 d. Cerebrospinal fluid samples were collected on three consecutive days before an exposure period of 30 d, on the last 3 d of the exposure period, and for 3 d starting 5 d after the exposure period. The concentrations of beta-endorphin, tryptophan, 5-hydroxyindoleacetic acid, homovanillic acid, 3-methoxy-4-hydroxyphenylethyleneglycol and quinolinic acid in cerebrospinal fluid were determined. There was a significant increase in quinolinic acid, and a trend towards an increase in tryptophan, findings consistent with a weakening of the blood-brain barrier due to exposure to the electric and magnetic fields.     

Fifty-Hertz magnetic field exposures of premature infants in a neonatal intensive care unit

In this study the magnetic flux density in and around incubators of a neonatal intensive care unit was registered and mapped. The mean 50-Hz magnetic flux densities in an incubator were typically in the range of 0.2-1 microT, with maximum values around 1.5 microT. For 1 incubator, harmonics contributed to the field substantially. The field levels varied depending on the type of equipment, the positioning of the electronics and the position of the 240-volt main plugs. The positioning of the infant in the incubator and the precise mattress position in the incubator affected the magnetic flux density to a great extent, as did the positioning of the electronic monitoring and treatment equipment. The flux density values found were fairly low as compared to magnetic field levels present at some work places where high electric currents are used. In intensive care units, however, the duration of exposure can be very long, especially for premature infants. The fields can also be compared with the magnetic field levels of residences and are then approximately 100 times higher. Further studies are necessary -it seems important to record magnetic fields and attempt to reduce the levels. Such a reduction can be achieved by reducing the field from the incubators but also by changing the electronic equipment around the incubators or increasing the distance to the incubator. Further research should of course also study any mechanism by which magnetic fields can affect cells and organisms. Compared to the risks many of these infants are exposed to, it is difficult to say whether the magnetic field levels measured can represent a significant additional risk factor. However, this is an area where one should adopt a prudent avoidance strategy, particulary considering how easily these fields can be reduced, mainly through redesign of the various equipment.     

双辊薄带连铸电磁侧封磁场的计算与分析

电磁侧封是双辊薄带连铸工艺中新兴的侧封技术其关键是电磁装置的设计,以在适熔池侧部获得足够大而且分布合理的电磁场.本文利用2D模型计算了电磁侧封装置产生的磁场,分析了电流、线圈、铁芯、辊环、气隙对磁场的影响规律.结果表明:影响磁场的因素按影响程度从大到小排列依次为:辊环磁导率、线圈匝数、磁头间距(气隙宽度)、电流密度、磁头宽度.除磁头间距外,各因素对磁场的影响基本呈线性.因此辊环的设计、线圈匝数与电流是增大侧封磁场的主要途径.     

Intracortical inhibition of lower limb motor-evoked potentials after paired transcranial magnetic stimulation

The aim of the present study was to determine the characteristics of intracortical inhibition in the motor cortex areas representing lower limb muscles using paired transcranial magnetic (TMS) and transcranial electrical stimulation (TES) in healthy subjects. In the first paradigm (n=8), paired magnetic stimuli were delivered through a double cone coil and motor evoked potentials (MEPs) were recorded from quadriceps (Q) and tibialis anterior (TA) muscles during relaxation. The conditioning stimulus strength was 5% of the maximum stimulator output below the threshold MEP evoked during weak voluntary contraction of TA (33+/-5%). The test stimulus (67+/-2%) was 10% of the stimulator output above the MEP threshold in the relaxed TA. Interstimulus intervals (ISIs) from 1-15 ms were examined. Conditioned TA MEPs were significantly suppressed (P<0.01) at ISIs of less than 5 ms (relative amplitude from 20-50% of the control). TA MEPs tended to be only slightly facilitated at 9-ms and 10-ms ISIs. The degree of MEP suppression was not different between right and left TA muscles despite the significant difference in size of the control responses (P<0.001). Also, conditioned MEPs were not significantly different between Q and TA. The time course of TA MEP suppression, using electrical test stimuli, was similar to that found using TMS. In the second paradigm (n=2), the suppression of TA MEPs at 2, 3, and 4 ms ISIs was examined at three conditioning intensities with the test stimulation kept constant. For the pooled 2- to 4-ms ISI data, relative amplitudes were 34+/-6%, 61+/-5%, and 98+/-9% for conditioning intensities of 0.95, 0.90, and 0.85x active threshold, respectively (P<0.01). In conclusion, the suppression of lower limb MEPs following paired TMS showed similar characteristics to the intracortical inhibition previously described for the hand motor area.     

Measurement of off-axis and peripheral skin dose using radiochromic film

A radiotheraphy skin dose profile can be obtained with radiochromic film. The central axis skin dose relative to Dmax for a 10 x 10 cm2 field size was found to be 22%, 17% and 15.5% for 6 MV, 10 MV and 18 MV photon beams. Peripheral dose increased with increasing field size. At 10 MV the skin dose 2 cm outside the geometric field edge was measured as 6%, 10% and 17% for 10 x 10 cm2, 20 x 20 cm2 and 30 x 30 cm2 field sizes respectively. Off-axis skin dose decreased as distance increased from central axis for fields with Perspex block trays. For a 20 x 20 cm2 field, an approximately 5-8% drop in percentage skin dose was observed from central axis to the beam edge.     

面向风电消纳的铝电解槽电磁场特性研究

针对铝电解消纳风电过程中物理场将发生非线性变化的现状,建立针对消纳风电的铝电解槽电磁场模型,并开展了消纳电流为设计电流的25%、20%、15%、10%和5%五种情况下的电磁场计算。结果表明,槽电压随着消纳的幅度增加而增加,同时铝液层水平电流密度亦存在相应变化,但电场整体趋势未变,各部分压降均在合理水平;此外,随着消纳风电量的增加,槽内磁场极值与均值都会相应增加,但整体的磁场分布规律未发生大幅波动,电解槽依然可以维持在稳定状态,从而保证在消纳风电过程中,电解槽内磁流体的稳定性,为其平稳消纳提供先天条件。     

Effect of applied magnetic fields during directional solidification of eutectic Bi-Mn

Samples of eutectic Bi/MnBi were directionally solidified in the presence of a transverse magnetic field up to 3 kG to determine if gravity-induced convection effects could be reduced or eliminated. Furnace velocity, V, was varied over the range 0.2 cm/h ≤V ≤ 50 cm per hour (1 cm per hour =2.8 μm per second) while thermal gradients at the liquid-solid interface were 100 °C/cm and 150 °C/cm. The microstructure of Bi/MnBi is characterized by a regular, aligned-rod eutectic morphology which is sensitive to growth conditions. This, combined with ferromagnetism of one of the components, MnBi, can be used to determine whether convection effects are significant enough to be affected by the presence of a static, homogeneous, magnetic field. Morphological, thermal, and magnetic analyses were carried out on samples grown with and without an applied magnetic field. Results indicated reduced MnBi mean rod diameters and interred spacings for samples grown at velocities > 3 cm per hour in a transverse magnetic field. Additionally, there was significant undercooling occurring for the applied field case as evidenced byin situ thermocouple measurements. Enhanced magnetic coercivities were also observed for samples grown aboveV = 3 cm per hour in a transverse magnetic field compared with no field conditions. The magnetic field growth was found to be similar to previous low-gravity results. This paper is based on a presentation made at the symposium “Fluid Flow at Solid-Liquid Interfaces” held at the fall meeting of the TMS-AIME in Philadelphia, PA on October 5, 1983 under the TMS-AIME Solidification Committee.     

Cloning and nucleotide sequence of a complementary DNA encoding Xenopus laevis metallothionein: mRNA accumulation in response to heavy metals

This investigation studied the effect of 50 Hz electric and magnetic fields on the human heart. The electrocardiograms of 27 transmission-line workers and 26 male volunteers were recorded with a Holter recorder both in and outside the fields. The measurements took from half an hour to a few hours. The electric field strength varied from 0.14 to 10.21 kV/m and the magnetic flux density from 1.02 to 15.43 microT. Analysis of the ECG recordings showed that extrasystoles or arrhythmias were as frequent outside the field as in the field. In some cases a small decrease in heart rate was observed after field exposure.     

Influence of human model resolution on computed currents induced in organs by 60-Hz magnetic fields

The effects of human body model resolution on computed electric fields induced by 60 Hz uniform magnetic fields are investigated. A recently-developed scalar potential finite difference code for low-frequency electromagnetic computations is used to model induction in two anatomically realistic human body models. The first model consists of 204290 cubic voxels with 7.2-mm edges, while the second comprises 1639146 cubic voxels with 3.6-mm edges. Calculations on the lower-resolution model using, for example, the finite difference time domain or impedance methods, push the capabilities of workstations. The scalar method, in contrast, can handle the higher-resolution model using comparable resources. The results are given in terms of average and maximum electric field intensities and current density magnitudes in selected tissues and organs. Although the lower-resolution model provides generally acceptable results, there are important differences that make the added computational burden of the higher-resolution calculations worthwhile. In particular, the higher-resolution modelling generally predicts peak electric fields intensities and current density magnitudes that are slightly higher than those computed using the lower-resolution modelling. The differences can be quite large for small organs such as glands.     

MCG simulations with a realistic heart-torso model

Magnetocardiograms (MCG's) simulated with a high-resolution heart-torso model of an adult subject were compared with measured MCG's acquired from the same individual. An exact match of the measured and simulated MCG's was not found due to the uncertainties in tissue conductivities and cardiac source positions. However, general features of the measured MCG's were reasonably represented by the simulated data for most, but not all of the channels. This suggests that the model accounts for the most important mechanisms underlying the genesis of MCG's and may be useful for cardiac magnetic field modeling under normal and diseased states. MCG's were simulated with a realistic finite-element heart-torso model constructed from segmented magnetic resonance images with 19 different tissue types identified. A finite-element model was developed from the segmented images. The model consists of 2.51 million brick-shaped elements and 2.58 million nodes, and has a voxel resolution of 1.56 x 1.56 x 3 mm. Current distributions inside the torso and the magnetic fields and MCG's at the gradiometer coil locations were computed. MCG's were measured with a Philips twin Dewar first-order gradiometer SQUID-system consisting of 31 channels in one tank and 19 channels in the other.