iMRS 2000 - PEMF Publications
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PEMF Publications

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1101

The compared effect of a four-coiled system in pulsed electromagnetic field stimulation

A clinical trial of 21 cases was conducted to evaluate the effects of a pulsed magnetic field on pseudoarthroses. Nineteen out of 21 cases had successful results; the remaining 2 failed to respond. Two-coiled and four-coiled systems were used in this study. It was concluded that the four coiled system is more effective in spite of its practical disadvantages and larger size.

1103

The correlation of in vivo and ex vivo tissue dielectric properties to validate electromagnetic breast imaging: initial clinical experience

Electromagnetic (EM) breast imaging provides low-cost, safe and potentially a more specific modality for cancer detection than conventional imaging systems. A primary difficulty in validating these EM imaging modalities is that the true dielectric property values of the particular breast being imaged are not readily available on an individual subject basis. Here, we describe our initial experience in seeking to correlate tomographic EM imaging studies with discrete point spectroscopy measurements of the dielectric properties of breast tissue. The protocol we have developed involves measurement of in vivo tissue properties during partial and full mastectomy procedures in the operating room (OR) followed by ex vivo tissue property recordings in the same locations in the excised tissue specimens in the pathology laboratory immediately after resection. We have successfully applied all of the elements of this validation protocol in a series of six women with cancer diagnoses. Conductivity and permittivity gauged from ex vivo samples over the frequency range 100 Hz-8.5 GHz are found to be similar to those reported in the literature. A decrease in both conductivity and permittivity is observed when these properties are gauged from ex vivo samples instead of in vivo. We present these results in addition to a case study demonstrating how discrete point spectroscopy measurements of the tissue can be correlated and used to validate EM imaging studies.

1105

The development and application of pulsed electromagnetic fields (PEMFs) for ununited fractures and arthrodeses

This article deals with the rational and practical use of surgically noninvasive pulsed electromagnetic fields (PEMFs) in treating ununited fractures, failed arthrodeses, and congenital pseudarthroses (infantile nonunions). The method is highly effective (more than 90 per cent success) in adult patients when used in conjunction with good management techniques that are founded on biomechanical principles. When union fails to occur with PEMFs alone after approximately four months, their proper use in conjunction with fresh bone grafts insures a maximum failure rate of 1 to 1.5 per cent. Union occurs because the weak electric currents induced in tissues by the time-varying fields effect calcification of the fibrocartilage in the fracture gap, thereby setting the stage for the final phases of fracture healing by endochondral ossification. The efficacy, safety, and simplicity of the method has prompted its use by the majority of orthopedic surgeons in this country. In patients with delayed union three to four months postfracture, PEMFs appear to be more successful and healing, generally, is more rapid than in patients managed by other conservative methods. For more challenging problems such as actively infected nonunions, multiple surgical failures, long-standing (for example, more than two years postfracture) atrophic lesions, failed knee arthrodeses after removal of infected prostheses, and congenital pseudarthroses, success can be expected in a large majority of patients in whom PEMFs are used. Finally, as laboratory studies have expanded knowledge of the mechanisms of PEMF action, it is clear that different pulses affect different biologic processes in different ways. Selection of the proper pulse for a given pathologic entity has begun to be governed by rational processes similar, in certain respects, to those applied to pharmacologic agents.

1106

The development and application of pulsed electromagnetic fields (PEMFs) for ununited fractures and arthrodeses

This article deals with the rational and practical use of surgically noninvasive pulsed electromagnetic fields (PEMFs) in treating ununited fractures, failed arthrodeses, and congenital pseudarthroses (infantile nonunions). The method is highly effective (more than 90 per cent success) in adult patients when used in conjunction with good management techniques that are founded on biomechanical principles. When union fails to occur with PEMFs alone after approximately four months, their proper use in conjunction with fresh bone grafts insures a maximum failure rate of 1 to 1.5 per cent. Union occurs because the weak electric currents induced in tissues by the time-varying fields effect calcification of the fibrocartilage in the fracture gap, thereby setting the stage for the final phases of fracture healing by endochondral ossification. The efficacy, safety, and simplicity of the method has prompted its use by the majority of orthopedic surgeons in this country. In patients with delayed union three to four months postfracture, PEMFs appear to be more successful and healing, generally, is more rapid than in patients managed by other conservative methods. For more challenging problems such as actively infected nonunions, multiple surgical failures, long-standing (for example, more than two years postfracture) atrophic lesions, failed knee arthrodeses after removal of infected prostheses, and congenital pseudarthroses, success can be expected in a large majority of patients in whom PEMFs are used. Finally, as laboratory studies have expanded knowledge of the mechanisms of PEMF action, it is clear that different pulses affect different biologic processes in different ways. Selection of the proper pulse for a given pathologic entity has begun to be governed by rational processes similar, in certain respects, to those applied to pharmacologic agents.

1109

The effect of diapulse therapy on the healing of decubitus ulcer

The effect of pulsed high peak power electromagnetic field (Diapulse) on treatment of pressure ulcers is under investigation. 20 elderly patients, aged from 60 to 84, hospitalized with chronic conditions and bearing long-standing pressure ulcers, are subjected to Diapulse sessions (1-2 daily), parallel to conventional treatment. 5 patients undergo conventional therapy, serving as control and 5 others follow conventional+placebo Diapulse treatment. All patients were daily monitored, concerning their clinical status and ulcers' healing. After a maximum 2-weeks treatment, bulge healing rate was, as follows: 85% excellent and 15% very good healing under Diapulse therapy; in the placebo group, 80% patients show no improvement and 20% poor improvement; in the control group, 60% patients show no improvement and 40% poor improvement of ulcers. This investigation strongly advises for Diapulse treatment as a modern, uninvasive therapy of great efficiency and low social costs in resolving a serious, widespread medical problem.

1110

The effect of electromagnetic pulsing on posterior lumbar spinal fusions in dogs

This study evaluated the effect of pulsed electromagnetic fields (PEMF) on the healing of lumbar spinal fusions. Bilateral posterior facet fusions were performed at L1-2 and L4-5 in 24 adult mongrel dogs. After surgery, eight animals were stimulated with a pulse burst type signal (PEMF) for 30 minutes a day, and eight animals were stimulated with the same PEMF for 60 minutes a day. The remaining eight animals received no active PEMF stimulation and served as controls. Four animals from each group were euthanatized at 6 and 12 weeks, and the facet fusions were evaluated using high resolution radiographs and routine histology. No statistical difference in the radiographic or histologic appearance of the fusion mass could be detected between the stimulated and control groups at either 6 or 12 weeks. The results of this study suggest that PEMF stimulation had no effect on the healing of the primary posterior spinal fusions in this controlled experimental canine model.

1112

The effect of exposure to high flux density static and pulsed magnetic fields on lymphocyte function

We investigated whether a combination of static electromagnetic field (EMF) at a flux density of 4.75 T together with pulsed EMF at a flux density of 0.7 mT generated by an NMR apparatus (NMRF), could promote movements of Ca(2+), cell proliferation, and the eventual production of proinflammatory cytokines in human lymphocytes as well as in Jurkat cells, after exposure to the field for 1 h. The same study was also performed after activation of cells with 5 micro g/ml phytohaemagglutinin (PHA) immediately before the exposure period. Our results clearly demonstrate that NMRF exposure increases the [Ca(2+)](i), without any proliferative, or activating, or proinflammatory effect on both normal and PHA stimulated lymphocytes. Accordingly, the levels of interferon gamma, tumor necrosis factor alpha, interleukin-1beta, interleukin-2, and interleukin-6 remained unvaried after exposure. Exposure of Jurkat cells statistically decreased the [Ca(2+)](i) and the proliferation. This is consistent with the low levels of IL-2 measured in supernatants of these cells after exposure. On the whole our data suggest that static and pulsed NMRF exposure contribute synergistically in the increase of the [Ca(2+)](i) without any activating or proinflammatory effect either in normal or in PHA challenged lymphocytes. In Jurkat cells, by changing the properties of cell membranes, NMRF exposure can influence Ca(2+) transport processes and hence Ca(2+) homeostasis, causing a marked decrease of proliferation.

1113

The effect of induced electric currents on bone after experimental osteotomy in sheep

We have investigated the effect of currents induced by electromagnetic fields on the healing of the tibia of sheep after osteotomy, using objective and quantifiable criteria wherever possible. A battery-powered, induction apparatus was developed and was enclosed within the cast applied to the limb, so that the treated fractures received pulsed magnetic fields for 24 hours a day while the animals were freely mobile. In all, 13 sheep were treated and 13 were used as controls. The response was assessed by radiography of the limb and of the excised bone, by histology, including measurement of the areas of callus, fibrocallus and cortical bone, and by measurement of the uptake and extraction of bone-seeking mineral. All the bones healed and no statistically significant differences between the treated animals and the controls were discovered except (at only P less than 0.05) in the uptake of bone-seeking mineral; this increased more rapidly in treated animals over the two to three weeks after osteotomy, although at six weeks the uptake in both groups was the same.

1114

The effect of low frequency magnetic fields on the healing of the osteotomized rabbit radius

The object of this experimental work was to evaluate the effect of a noninvasive method of electrical stimulation on the healing of freshly-created osteotomies of the rabbit radius. The apparatus consisted of a solid core electromagnet energized by a square wave unidirectional current. The magnetic field was pulsed transversely across the osteotomy site of the radius while the animal was confined to a restraining device 6 hours daily for 5 days per week. In one group of animals the influence of different pulse frequencies, using 0.1 Hz, 1 Hz, and 4 Hz, was evaluated, while the period of stimulation was kept constant at 2 weeks. In another group of animals, exposure was continued for 3 and 4 weeks while the pulse frequency was kept constant at 1 Hz. Histologic and radiologic comparison with control animals revealed that the initiation of the healing process can be accelerated in magnetic fields pulsed at 1 Hz, but that this effect is not maintained, and that the total period of time required for union is not significantly shortened. In view of these findings, this form of treatment is not recommended for clinical use in the treatment of recent fractures of long bones.

1115

The effect of low-frequency electrical fields on osteogenesis

An in vivo animal model of disuse osteopenia was used to determine the osteogenic potential of specific components of electrical fields. The ability of a complex pulsed electrical field to inhibit loss of bone was compared with the remodeling response generated by extremely low-power, low-frequency (fifteen, seventy-five, and 150-hertz) sinusoidal electrical fields. The left ulnae of thirty adult male turkeys were functionally isolated by creation of distal and proximal epiphyseal osteotomies and then were exposed, for one hour each day, to an electrical field that had been induced exogenously by means of magnetic induction. After a fifty-six-day protocol, the remodeling response was quantified by a comparison of the cross-sectional area of the mid-part of the diaphysis of the functionally isolated ulna with that of the intact contralateral ulna. Disuse resulted in a 13 per cent mean loss of osseous tissue, which was not significantly different than the 10 per cent loss that was caused by disuse treated with inactive coils. Exposure to the pulsed electrical fields prevented this osteopenia and stimulated a 10 per cent mean increase in the bone area. The osteogenic influence of the sinusoidal electrical fields was strongly dependent on the frequency; the 150, seventy-five, and fifteen-hertz sinusoidal fields, respectively, generated a -3 per cent, + 5 per cent, and + 20 per cent mean change in the bone area. These results suggest a tissue sensitivity that is specific to very low-frequency sinusoidal electrical fields, and they imply that the induced electrical fields need not have complex waveforms to be osteogenic. Since the frequency and intensity range of the sinusoidal fields producing the greatest osteogenic response are similar to the levels produced intrinsically by normal functional activity, these results support the hypothesis that electricity plays a role in the retention of the normal remodeling balance within mature bone.

1116

The effect of low-frequency pulsed magnetic fields on chick embryonic growth

There are many claims made for biological effects of low-frequency pulsed magnetic fields ranging from beneficial to harmful, but few have been independently verified. The ubiquitous nature of both natural and man-made magnetic fields makes the possibility of biological interaction a potentially important subject. We have investigated the claimed stimulatory action of low-frequency pulsed magnetic fields, of a type used clinically, on the growth of embryonic chicks. Four day old embryos were exposed to a magnetic field, peak field strength 2.1 mT pulsed in 5 ms bursts repeated at 15 Hz, for 100 h. Embryo weights and long-bone lengths were compared to sham-exposed controls. Particular care was taken to reduce temperature differences between the test and control groups because this model has a known sensitivity to small temperature changes. We found no increase in embryonic growth due to this low-frequency pulsed magnetic field and hence have been unable to confirm earlier findings by other workers using the same model. We conclude that rigorous design of experimental protocol and a full description of the physical parameters are essential in studies purporting to show effects of electromagnetic fields if the results are to be confirmed by other workers.

1117

The effect of magnetic resonance imagers on implanted neurostimulators

This in-vitro study was designed to investigate the safety of various implanted neurostimulators in magnetic resonance (MR) imagers. The effects of the static and changing magnetic fields and the radio frequency (RF) electromagnetic field generated by 0.35 and 1.5 T MR imagers on the voltage output of four models of implantable passive neurostimulators and two models of implantable self-powered neurostimulators was studied. The neurostimulators were mounted on a support and placed in the imagers. An oscilloscope monitored the voltages at the outputs of the neurostimulators. For an Avery single-channel stimulator, located at the isocenter, the amplitude of the output pulses induced by the 0.35 T imager was 6V; from a 1.5 T imager, it was 12 V. These amplitudes can cause discomfort and possible harm to a patient if the typical therapeutic value is 1-5 V. The amplitude of the stimulator receiver's output decreased to relatively safe values beyond 40 cm from the isocenter. By contrast, there was no significant voltage output from the Medtronic SE-4 receiver. For two models of self-powered neurostimulators, the Medtronic Itrel and the Cordis MK II, the programmed stimulus parameters were not affected by the pulsed magnetic fields of the MR imagers. However, the RF fields at the isocenter heated the metal case of the stimulators. The rotational and linear forces produced by the fixed magnet on the Cordis MK II were judged to be too strong for a patient with this implant to be scanned. The study showed that patients with certain types of implanted neurostimulators can be scanned safely under certain conditions.

1118

The effect of nitrous oxide on transcranial magnetic-induced electromyographic responses in the monkey

Transcranial magnetic stimulation (TMS) to produce motor evoked potentials (MEPs) is a newly developed intraoperative modality to monitor functional integrity of the motor pathways. The present study was designed to examine the reliability of magnetic MEP recording under nitrous oxide (N2O) inhalation. Following ketamine injection (10 mg/kg i.m.) and endotracheal intubation, 16 monkeys were exposed to N2O:O2 mixture ratios 1:3, 1:1, and 3:1. Electromyographic (EMG) responses, evoked by pulsed magnetic fields applied extracranially to the scalp zone overlying motor cortex, were recorded from the contralateral fore- and hind limb flexor muscles. The scalp topography zone for contralateral muscle excitation was markedly reduced by 75 vol% N2O. Significant stimulation threshold elevation, latency prolongation, and amplitude depression were noted after inhalation of 75 vol% N2O (p <0.05) compared with

1119

The effect of pulsating electromagnetic fields on condylar growth in guinea pigs

The purpose of this study was to determine if a simple, noninvasive method could be developed for the application of pulsed electromagnetic fields that would lend itself to future clinical applications. Specifically, the modulation and control of condylar cellular metabolism and the stimulation of cellular proliferation were attempted in order to increase the amount of mandibular condylar growth. A pulsed electromagnetic field with a frequency of 100 hertz was applied for 8 hours per day to the mandibular condylar area of rapidly growing, male, Hartley guinea pigs. Ten guinea pigs were exposed for 10 days and a second group of 10 guinea pigs was exposed for 30 days. In addition, 5 guinea pigs were used as controls for each experimental period. During the experimental period the guinea pigs were placed in specially constructed, plastic animal holders with their heads positioned in an area of uniform magnetic field. After 10 days of pulsed electromagnetic field exposure, there were increases in vascularity, secretion of cartilagenous intercellular matrix, and woven-bone formation in the guinea pig condyle. After 30 days, there were continued but attenuated vascular and calcification responses with an increase noted in marrow hemopoietic elements. An increase in the number of osteoclasts was also noted after 10 days. This effect was transient and was not present at the end of the 30-day experimental period. The application of the pulsed electromagnetic field did not result in a significant increase in the overall anteroposterior or vertical size of the guinea pig mandible compared to controls. The results of this study suggest that it is possible to affect condylar cartilagenous and bony metabolism through the application of a noninvasive, pulsed electromagnetic field.

1120

The effect of pulsed and sinusoidal magnetic fields on the morphology of developing chick embryos

Several investigators have reported robust, statistically significant results that indicate that weak (approximately 1 microT) magnetic fields (MFs) increase the rate of morphological abnormalities in chick embryos. However, other investigators have reported that weak MFs do not appear to affect embryo morphology at all. We present the results of experiments conducted over five years in five distinct campaigns spanning several months each. In four of the campaigns, exposure was to a pulsed magnetic field (PMF); and in the final campaign, exposure was to a 60 Hz sinusoidal magnetic field (MF). A total of over 2500 White Leghorn chick embryos were examined. When the results of the campaigns were analyzed separately, a range of responses was observed. Four campaigns (three PMF campaigns and one 60 Hz campaign) exhibited statistically significant increases (P > or = 0.01), ranging from 2-fold to 7-fold, in the abnormality rate in MF-exposed embryos. In the remaining PMF campaign, there was only a slight (roughly 50%), statistically insignificant (P = 0.2) increase in the abnormality rate due to MF exposure. When the morphological abnormality rate of all of the PMF-exposed embryos was compared to that of all of the corresponding control embryos, a statistically significant (P > or = .001) result was obtained, indicating that PMF exposure approximately doubled the abnormality rate. Like-wise, when the abnormality rate of the sinusoid-exposed embryos was compared to the corresponding control embryos, the abnormality rate was increased (approximately tripled). This robust result indicates that weak EMFs can induce morphological abnormalities in developing chick embryos. We have attempted to analyze some of the confounding factors that may have contributed to the lack of response in one of the campaigns. The genetic composition of the breeding stock was altered by the breeder before the start of the nonresponding campaign. We hypothesize that the genetic composition of the breeding stock determines the susceptibility of any given flock to EMF-induced abnormalities and therefore could represent a confounding factor in studies of EMF-induced bioeffects in chick embryos.

1121

The effect of pulsed electric fields on the phosphorus-31 spectra of lipid bilayers

A technique is described for measuring the effect of electric fields on the conformation of lipid bilayer membranes by solid state nuclear magnetic resonance. An apparatus was devised to obtain spectra from samples of aligned phospholipid dispersions at varying electric field strengths up to 100 MV/m. Measurements were carried out on membranes made from dioleoylphosphatidylethanolamine and dioleoylphosphatidylcholine, which resulted in electric field induced phase changes. Calibration experiments were performed using bilayers formed from dimyristoylphosphatidylcholine with glycerol and with a nematic liquid crystal. An electric field induced change, from L alpha to HII, was also seen in a dimyristoylphosphatidylcholine/alamethicin bilayer.

1122

The effect of pulsed electromagnetic field (Diapulse) on cellular systems

The effect of a 27.12 MHz pulsed electromagnetic field (Diapulse) on microbial growth is investigated. A strain of K 12 E. coli grown in complete Pennassay medium is subjected to Diapulse action for 30 min, at 8 hrs and 12 hrs of growth. In this experimental set-up, designed to be closed to the physiological conditions of open wounds, the Diapulse action does not promote any increase of cell population, indicating the safety of this type of therapy for wound healing process. The same K 12 E. coli strain grown in Pennassay medium for 2 hours is inoculated into a minimal growth medium and the lagless exponential growth thus obtained is followed by a spectrophotometric method. Diapulse field is applied to this lagless phase of cellular cultures at 30, 60, and 90 minutes after inoculation. A slight increase in the number of cells was observed at 2 and 4 hours after the Diapulse application, when the cultures were previously subjected to Diapulse action between the period of 60 and 90 minutes of their growth. A possible molecular mechanism for these effects is discussed.

1123

The effect of pulsed electromagnetic field on patients with endocrine ophthalmopathy

PURPOSE: To evaluate eye signs, proptosis and ocular movements in patients with endocrine ophthalmopathy under the influence of pulsed electromagnetic field therapy. METHODS: We examined 14 patients (9 women, 5 men) with endocrine ophthalmopathy and evaluated eye signs, proptosis and ocular movements before and after the course of pulsed electromagnetic field therapy, and 12 controls. Their age ranged from 29 to 57 years. Visual sensitivity was investigated with a static automatic perimeter (Allergan Humphrey Field Analyzer). The score was calculated by rating the severity of involvement of soft tissue, proptosis, extraocular movements, corneal state and optic nerve function on a scale from 0 to 3. The pulsed electromagnetic field procedures were carried out with the help of electromagnetic spectacles. RESULTS: Pulsed electromagnetic field therapy reduced the score for soft tissue and proptosis in patients who suffered from endocrine ophthalmopathy. There was fall in the mean score for ocular movements, corneal and optic nerve function but it did not reach significance after treatment. Electromagnetic field therapy has no useful effect on visual signs and eye movements in two patients who had had the illness more than two years. CONCLUSIONS: Localised pulsed electromagnetic field procedures can be recommended, together with other methods of conservative treatment of endocrine ophthalmopathy.

1124

The effect of pulsed electromagnetic fields in the treatment of cervical osteoarthritis: a randomized, double-blind, sham-controlled trial

Abstract The purpose of this study was to evaluate the effect of electromagnetic field therapy (PEMF) on pain, range of motion (ROM) and functional status in patients with cervical osteoarthritis (COA). Thirty-four patients with COA were included in a randomized, double-blind study. PEMF was administrated to the whole body using a mat 1.8·0.6 m in size. During the treatment, the patients lay on the mat for 30 min per session, twice a day for 3 weeks. Pain levels in the PEMF group decreased significantly after therapy (p<0.001), but no change was observed in the placebo group. The active ROM, paravertebral muscle spasm and neck pain and disability scale (NPDS) scores improved significantly after PEMF therapy (p<0.001) but no change was observed in the sham group. The results of this study are promising, in that PEMF treatment may offer a potential therapeutic adjunct to current COA therapies in the future. Keywords Cervical osteoarthritis, Pulsed electromagnetic fields

1125

The effect of pulsed electromagnetic fields in the treatment of cervical osteoarthritis: a randomized, double-blind, sham-controlled trial

The purpose of this study was to evaluate the effect of electromagnetic field therapy (PEMF) on pain, range of motion (ROM) and functional status in patients with cervical osteoarthritis (COA). Thirty-four patients with COA were included in a randomized, double-blind study. PEMF was administrated to the whole body using a mat 1.8 x 0.6 m in size. During the treatment, the patients lay on the mat for 30 min per session, twice a day for 3 weeks. Pain levels in the PEMF group decreased significantly after therapy (p<0.001), but no change was observed in the placebo group. The active ROM, paravertebral muscle spasm and neck pain and disability scale (NPDS) scores improved significantly after PEMF therapy (p<0.001) but no change was observed in the sham group. The results of this study are promising, in that PEMF treatment may offer a potential therapeutic adjunct to current COA therapies in the future.

1126

The effect of pulsed electromagnetic fields in the treatment of osteoarthritis of the knee and cervical spine. Report of randomized, double blind, placebo controlled trials

OBJECTIVE. We conducted a randomized, double blind clinical trial to determine the effectiveness of pulsed electromagnetic fields (PEMF) in the treatment of osteoarthritis (OA) of the knee and cervical spine. METHODS. A controlled trial of 18 half-hour active or placebo treatments was conducted in 86 patients with OA of the knee and 81 patients with OA of the cervical spine, in which pain was evaluated using a 10 cm visual analog scale, activities of daily living using a series of questions (answered by the patient as never, sometimes, most of the time, or always), pain on passive motion (recorded as none, slight, moderate, or severe), and joint tenderness (recorded using a modified Ritchie scale). Global evaluations of improvement were made by the patient and examining physician. Evaluations were made at baseline, midway, end of treatment, and one month after completion of treatment. RESULTS. Matched pair t tests showed extremely significant changes from baseline for the treated patients in both knee and cervical spine studies at the end of treatment and the one month followup observations, whereas the changes in the placebo patients showed lesser degrees of significance at the end of treatment, and had lost significance for most variables at the one month followup. Means of the treated group of patients with OA of the knee showed greater improvement from baseline values than the placebo group by the end of treatment and at the one month followup observation. Using the 2-tailed t test, at the end of treatment the differences in the means of the 2 groups reached statistical significance for pain, pain on motion, and both the patient overall assessment and the physician global assessment. The means of the treated patients with OA of the cervical spine showed greater improvement from baseline than the placebo group for most variables at the end of treatment and one month followup observations; these differences reached statistical significance at one or more observation points for pain, pain on motion, and tenderness. CONCLUSION. PEMF has therapeutic benefit in painful OA of the knee or cervical spine.

1127

The effect of pulsed electromagnetic fields on bone cell metabolism and calvaria resorption in vitro, and on calcium metabolism in the live rat

The effects of three pulsed electromagnetic fields were investigated on bone cells and calvaria in culture, and on calcium metabolism in the live rat. No significant effect was seen on: 1) the proliferation of calvaria cells in culture; 2) alkaline phosphatase level, lactic acid release and collagen synthesis by confluent calvaria cells, with the exception of one pulse which produced a small increase in the latter when expressed as DNA; 3) resorption of calvaria in culture; 4) intestinal absorption, urinary excretion and net balance of calcium, bone formation and bone resorption in the live rat.

1128

The effect of pulsed electromagnetic fields on chondrocyte morphology

Osteoarthritis is a debilitating joint disease where the articular cartilage surface degrades and is unable to repair itself through natural processes. Chondrocytes reside within the cartilage matrix and maintain its structure. We conducted in vitro experiments to investigate the morphological response of cultured human chondrocytes under different pulsed electromagnetic field (PEMF) conditions. In the control experiments, cultured chondrocytes attached to the bottom of a culture dish typically displayed either a stellate or spindle morphology with extended processes. Experimental chondrocyte cultures were placed in a Helmholtz coil to which a ramp waveform was applied. Exposure to PEMFs caused the chondrocytes to retract their processes, becoming spherical in shape. This change in morphology followed a progression from stellate to spindle to spherical. These morphological changes were reflected in an average reduction of 30% in the surface contact area of the chondrocytes to the culture dish. Understanding the mechanisms by which PEMFs affect the morphology of chondrocytes will help lead to new treatments for osteoarthritis.

1129

The effect of pulsed electromagnetic fields on flexor tendon healing in chickens

This study was designed as a pilot investigation of the effect of pulsed electromagnetic fields (PEMF) stimulation on early flexor tendon healing in a chicken model using a similar stimulus to that used clinically. The PEMF used caused a decrease in tensile strength and an increase in peritendinous adhesions.

1130

The effect of pulsed electromagnetic fields on flexor tendon healing in the rabbit

A double-blind controlled trial of the effects of pulsed electromagnetic fields on flexor tendon healing in adult New Zealand White rabbits was performed. A pulse burst waveform, previously demonstrated to influence new vessel growth in the rabbit, was employed. No significant effect was observed on either the healed strength of the tendon repair or the adhesion formation between the repair and the surrounding tissues. The model used for examination of adhesion formation was reproducible and is recommended for further work on the adhesion formation of healing tendons.

1131

The effect of pulsed electromagnetic fields on hindfoot arthrodesis: a prospective study

The aim of this study was to evaluate the effect of pulsed electromagnetic fields in a consecutive series of 64 patients undergoing hindfoot arthrodesis (144 joints). All patients who underwent elective triple/subtalar arthrodesis were randomized into control and pulsed electromagnetic field study groups. Subjects in the study group had an external pulsed electromagnetic fields device applied over the cast for 12 hours a day. Radiographs were taken pre- and postoperatively until radiographic union occurred. A senior musculoskeletal radiologist, blinded to the treatment scheme, evaluated the radiographic parameters. The average time to radiographic union in the control group was 14.5 weeks in 33 primary subtalar arthrodeses. There were 4 nonunions. The study group consisted of 22 primary subtalar arthrodeses and 5 revisions. The average time to radiographic union was 12.9 weeks (P =.136). The average time to fusion of the talonavicular joint in the control group was 17.6 weeks in 19 primary procedures. In the pulsed electromagnetic fields group of 20 primary and 3 revision talonavicular arthrodeses, the average time to radiographic fusion was 12.2 weeks (P =.003). For the 21 calcaneocuboid arthrodeses in control group, the average time to radiographic fusion was 17.7 weeks; it was 13.1 weeks (P =.010) for the 19 fusions in the study group. This study suggests that, if all parameters are equal, the adjunctive use of a pulsed electromagnetic field in elective hindfoot arthrodesis may increase the rate and speed of radiographic union of these joints.

1132

The effect of pulsed electromagnetic fields on instrumented posterolateral spinal fusion and device-related stress shielding

STUDY DESIGN: This study was designed to examine stress-shielding effects on the spine caused by rigid implants and to investigate the effects of pulsed electromagnetic fields on the instrumented spine. OBJECTIVES: To investigate the effects of pulsed electromagnetic fields on posterolateral spinal fusion, and to determine if osteopenia induced by rigid instrumentation can be diminished by pulsed electromagnetic fields. SUMMARY OF BACKGROUND DATA: Although device-related osteopenia on vertebral bodies is of a great clinical importance, no method for preventing bone mineral loss in vertebrae by stiff spinal implants has been effective. METHODS: Twenty-eight adult beagles underwent L5-L6 destabilization followed by posterolateral spinal fusion. The study was divided into four groups: 1) Group CNTL: without instrumentation, without pulsed electromagnetic fields, 2) Group PEMF: without Steffee, with pulsed electromagnetic fields, 3) Group INST: with Steffee, without pulsed electromagnetic fields, 4) Group PEMF + INST: with Steffee, with pulsed electromagnetic fields. At the end of 24 weeks, the dogs were killed, and L4-L7 segments were tested biomechanically without instrumentation. Radiographs and quantitative computed tomography assessed the condition of the fusion mass. RESULTS: Stress shielding was induced in the anterior vertebral bodies of L6 with the Steffee plates; bone mineral density was increased with the addition of pulsed electromagnetic fields, regardless of the presence or absence of fixation. A decrease in flexion and bending stiffness was observed in the Group INST; pulsed electromagnetic fields did increase the flexion stiffness regardless of the presence or absence of fixation, although this was not statistically significant. CONCLUSIONS: Use of pulsed electromagnetic fields has the potential to minimize device-related vertebral-bone mineral loss.

1133

The effect of pulsed electromagnetic fields on osteoporosis at the knee in individuals with spinal cord injury

The purpose of this study was to determine the effects of pulsed electromagnetic fields on osteoporotic bone at the knee in individuals with chronic spinal injury. The study consisted of 6 males with complete spinal cord injury at a minimum of 2 years duration. Bone mineral density (BMD) was obtained at both knees at initiation, 3 months, 6 months, and 12 months using dual energy X-ray absorptiometry. In each case, 1 knee was stimulated using The Bone Growth Stimulator Model 3005 from American Medical Electronics, Incorporated and the opposite knee served as the control. Stimulation ceased at 6 months. At 3 months BMD increased in the stimulated knees 5.1% and declined in the control knees 6.6% (p < .05 and p < .02, respectively). By 6 months the BMD returned to near baseline values and at 12 months both knees had lost bone at a similar rate to 2.4% below baseline for the stimulated knee and 3.6% below baseline for the control. There were larger effects closer to the site of stimulation. While the stimulation appeared useful in retarding osteoporosis, the unexpected exaggerated decline in the control knees and reversal at 6 months suggests underlying mechanisms are more complex than originally anticipated. The authors believe a local as well as a systemic response was created.

1134

The effect of pulsed electromagnetic fields on secondary skin wound healing: an experimental study

A variety of pulsed electromagnetic fields (PEMFs) have already been experimentally used, in an effort to promote wound healing. The aim of the present study was to investigate the effects of short duration PEMF on secondary healing of full thickness skin wounds in a rat model. Full thickness skin wounds, 2 by 2 cm, were surgically inflicted in two groups of male Wistar rats, 24 animals each. In the first group (experimental group - EG), the animals were placed and immobilized in a special constructed cage. Then the animals were exposed to a short duration PEMF for 20 min daily. In the second group (control group - CG), the animals were also placed and immobilized in the same cage for the same time, but not exposed to PEMF. On days 3, 6, 9, 12, 18, and 22, following the infliction of skin wounds, the size and healing progress of each wound were recorded and evaluated by means of planimetry and histological examination. According to our findings with the planimetry, there was a statistically significant acceleration of the healing rate for the first 9 days in EG, whereas a qualitative improvement of healing progress was identified by histological examination at all time points, compared to the control group.

1135

The effect of pulsed electromagnetic fields on the corrosion of a chromium-cobalt-nickel alloy orthopaedic implant

In order to assess whether pulsed electromagnetic fields influence the rate of corrosion of orthopaedic metal implants, an alloy, called MP-35N, was exposed for 3 wk to a pulsed electromagnetic field. The results demonstrated that while there was a progressive release of the major constituents of MP-35N, i.e. cobalt (32.5%), nickel (36%), and chromium (20%), with time, corrosion was not significantly higher in the presence of the pulsed electromagnetic field when compared to that of the non-exposed pins. There was a significantly higher release of cobalt by the control pins after 5, 10, and 15 d incubation when compared with the pulsed pins. These findings were confirmed by SEM which demonstrated progressive surface corrosion with time and that the extent of corrosion was similar for both the control and pulsed pins. These results suggest that pulsed electromagnetic fields have no effect in promoting the surface corrosion of orthopaedic metallic implants.

1136

The effect of pulsed electromagnetic fields on the osteointegration of hydroxyapatite implants in cancellous bone: a morphologic and microstructural in vivo study

Effects of pulsed electromagnetic fields (PEMFs, 75 Hz. 1.6 mT) were investigated in 12 rabbits after placing hydroxyapatite (HA) implants in their femoral condyles. Six animals were stimulated with PEMFs for three consecutive weeks, 6 h/day, while the remaining animals were sham-treated (Control Group). Rabbits were sacrificed at 3 and 6 weeks (after a 3-week non-stimulation period) for histomorphometric analysis and microhardness testing (at 200, 500, 1,000, 2,000 microm from the implant) around the implants. Histomorphometric analysis did not highlight any significant changes. On the contrary, there were statistically significant differences between the effects produced by PEMFs and Control Groups (F = 149.70, p < 0.0005) on the Affinity Index results, as well as by the experimental time of 6 and 3 weeks (F = 17.12, p = 0.001) on the same results. In PEMF-stimulated animals the microhardness (HV) values measured in trabecular bone at a distance of 200 and 500 microm from the implants, were significantly higher with respect to controls. At 6 weeks, HV values at the bone-implant interface in PEMF-stimulated animals were not significantly different with respect to normal bone, while they remained significantly lower in control animals. Both morphological and structural results demonstrated a positive therapeutic effect of PEMFs in accelerating HA osteointegration in trabecular bone.

1137

The effect of pulsed electromagnetic fields on the physiologic behaviour of a human astrocytoma cell line

We evaluated the effects of 50 Hz pulsed electromagnetic fields (EMFs) with a peak magnetic field of 3 mT on human astrocytoma cells. Our results clearly demonstrate that, after the cells were exposed to EMFs for 24 h, the basal [Ca(2+)](i) levels increased significantly from 124+/-51 nM to 200+/-79 nM. Pretreatment of the cells with 1.2 microM substance P increased the [Ca(2+)](i) to 555+/-278 nM, while EMF exposure caused a significant drop in [Ca(2+)](i) to 327+/-146 nM. The overall effect of EMFs probably depends on the prevailing Ca(2+) conditions of the cells. After exposure, the proliferative responses of both normal and substance P-pretreated cells increased slightly from 1.03 to 1.07 and 1.04 to 1.06, respectively. U-373 MG cells spontaneously released about 10 pg/ml of interleukin-6 which was significantly increased after the addition of substance P. Moreover, immediately after EMF exposure and 24 h thereafter, the interleukin-6 levels were more elevated (about 40%) than in controls. On the whole, our data suggest that, by changing the properties of cell membranes, EMFs can influence Ca(2+) transport processes and hence Ca(2+) homeostasis. The increased levels of interleukin-6 after 24 h of EMF exposure may confirm the complex connection between Ca(2+) levels, substance P and the cytokine network.

1139

The effect of short, high intensity magnetic field pulses on the healing of skin wounds in rats

The object of this study was to examine the effect of high intensity, short duration pulsed electromagnetic fields (PEMF) on the healing of full thickness skin wounds in rats. Full thickness skin wounds were surgically created in two groups of Sprague-Dawley male rats. The rats were randomly divided into two groups, each containing 20 rats. Animals in the treatment group received treatments with the PEMF device on day 0, 3, 7, 9, 12, 14, 17, and 22, while the rats in the control group were subjected to the same procedure, but with the PEMF device not activated. Photographs of the surgically created wounds were obtained on day 0, 3, 7, 9, 12, 14, 17, and 22. Wound contraction (WC), wound epithelialization (WE), non-healed wound, and contraction-epithelialization (CE) ratio were calculated for each wound. No significant difference was found between the two groups for the parameters of WC, WE, non-healed wound, and CE ratio. A significant group x time interaction was found for WE and CE ratio. This type of PEMF did not have a significantly beneficial effect on wound healing. Wounds in the PEMF treated group were relatively less contracted and showed a compensatory increase in epithelialization in the early stages of wound repair.

1140

The effect of short-duration, high-intensity electromagnetic pulses on fresh ulnar fractures in rats

Pulsed electromagnetic fields (PEMFs) have been found to be beneficial to a wide variety of biological phenomena. In particular, PEMFs have been shown to be useful in the promotion of healing of ununited fractures. Conflicting information exists regarding the benefit of using PEMFs to accelerate the healing of fresh fractures. This paper reports on the evaluation of the effect of a new PEMF generator (PAP IMI) on the healing of fresh ulnar fractures in rats. This device is unique by virtue of the extremely high power output of each of the pulses it generates. Ulnar fractures were created in rats by using a bone cutter, thus producing a 2-3 mm bone defect. Rats were then randomly divided into treatment and control groups. The treatment group underwent periodic treatments with the PAP IMI, and the control group received no treatment. Radiographs of rats from both groups were taken at 1-week intervals. Histological evaluation was performed at the end of the study. Radiographic and histopathological evaluations were scored, and scores were used to assess both rate and quality of healing. The radiographic results demonstrated gradual bridging callus formation in both control and treatment groups, however, the healing process was faster in rats that were not treated by PEMF. Histological evaluation demonstrated that the fibrous content of the callus in rats belonging to the treatment group was significantly higher than that in rats belonging to the control group. The results of this study do not support the claim that PEMF generated by the PAP-IMI stimulate osteogenesis and bone healing after the creation of fresh ulnar fractures in rats.

1141

The effect of spin relaxation on ENDOR spectra recorded at high magnetic fields and low temperatures

A simple theoretical model that describes the pulsed Davies electron-nuclear double resonance (ENDOR) experiment for an electron spin S = (1/2) coupled to a nuclear spin I = (1/2) was developed to account for unusual W-band (95 GHz) ENDOR effects observed at low temperatures. This model takes into account the thermal polarization along with all internal relaxation processes in a four-level system represented by the electron- and nuclear-spin relaxation times T(1e) and T(1n), respectively, and the cross-relaxation time, T(1x). It is shown that under conditions of sufficiently high thermal spin polarization, nuclei can exhibit asymmetric ENDOR spectra in two cases: the first when t(mix) >> T(1e) and T(1n), T(1x) >> T(1e), where ENDOR signals from the alpha manifold are negative and those of the beta manifold positive, and the second when the cross- and/or nuclear-relaxation times are longer than the repetition time (t(mix) << T(1e) << t(R) and T(1n), T(1x) > t(R)). In that case the polarization of the ENDOR signals becomes opposite to the previous case, the lines in the alpha manifolds are positive, and those of the beta manifold are negative. This case is more likely to be encountered experimentally because it does not require a very long mixing time and is a consequence of the saturation of the nuclear transitions. Using this model the experimental t(mix) and t(R) dependencies of the W-band (1)H ENDOR amplitudes of [Cu(imidazole)(4)]Cl(2) were reproduced and the values of T(1e) and T(1x) >> T(1e) were determined. The presence of asymmetry in the ENDOR spectrum is useful as it directly provides the sign of the hyperfine coupling. The presented model allows the experimentalist to adjust experimental parameters, such as t(mix) and t(R), in order to optimize the desired appearance of the spectrum.

1142

The effect of the pulsatile electromagnetic field in children suffering from bronchial asthma

From the bibliography it is well known that pulsatile electromagnetic field has an anti-inflammatory and analgesic effect. It causes vasodilatation, myorelaxation, hyper-production of connective tissue and activation of the cell membrane. Therefore our aim was to study the possible therapeutic effect of pulsatile electromagnetic field in asthmatic children. Forty-two children participating in this study were divided in two groups. The 1st group consisting of 21 children (11 females, 10 males, aged 11.8 +/- 0.4 yr) was treated by pulsatile electromagnetic field and pharmacologically. The 2nd group served as control, consisting also of 21 children (11 females, 10 males, aged 11.7 +/- 0.3 yr) and was treated only pharmacologically. Therapeutic effect of the pulsatile electromagnetic field was assessed on the basis of pulmonary tests performed by means of a Spirometer 100 Handi (Germany). The indexes FVC, IVC, ERV, IRV, FEV1, FEV1/FVC%, MEF75,50,25, PEF, PIF and the changes of the flow-volume loop were also registered. The pulsatile electromagnetic field was applied by means of the device MTU 500H, Therapy System (Brno, Czech Republic) for 5 days, two times daily for 30 minutes (magnetic induction: 3 mT, frequency: 4 Hz as recommended by the manufacturer). The results in children of the 1st group showed an improvement of FVC of about 70 ml, IVC of about 110 ml, FEV1 of about 80 ml, MEF75 of about 30 ml, PEF of about 480 ml, PIF of about 550 ml. The increases of ERV, IRV and FEV1/FVC and decreases of MEF25,50 were statistically insignificant. The results in the 2nd group were less clear. The flow-volume loop showed a mild improvement in 14 children. This improvement in the 2nd group was less significant. The clinical status of children and their mood became better. We believe that the pulsatile electro-magnetotherapy in children suffering from asthma is effective. On the basis of our results we can recommend it as a complementary therapy.

1143

The effects of electromagnetic field emitted by GSM phones on working memory

The influence of pulsed radiofrequency (RF) electromagnetic fields of digital GSM mobile phones on working memory in healthy subjects were studied. Memory load was varied from 0 to 3 items in an n-back task. Each subject was tested twice within a single session, with and without the RF exposure (902MHz, 217Hz). The RF field speeded up response times when the memory load was three items but no effects of RF were observed with lower loads. The results suggest that RF fields have a measurable effect on human cognitive performance and encourage further studies on the interactions of RF fields with brain function.

1144

The effects of external picoTesla range magnetic fields on the EEG in Parkinson's disease

We report a 68 year old man with a 7 year history of Parkinson's disease (PD) who obtained little benefit from treatment by dopaminergic and anticholinergic agents. During the six months prior to presentation, he experienced more rapid deterioration in symptoms including memory functions, increasing depression, and dystonia of the foot. External application of picoTesla range magnetic fields (MF) resulted in rapid attenuation of tremor and foot dystonia with improvements in gait, postural reflexes, mood, anxiety, cognitive, and autonomic functions. Plasma prolactin and luteinizing hormone (LH) levels rose three days after initiation of treatment. In addition, distinct electroencephalographic (EEG) changes were recorded nine days after two treatments with MF and included enhancement of alpha and beta activities as well as resolution of the theta activity. These findings demonstrate, for the first time, objective EEG changes in response to picoTesla range MF in PD. Since the pineal gland is a magnetosensor and as some of the clinical effects produced by MF such as relaxation, sleepiness, mood elevation, increased dreaming, and enhancement of alpha and beta activities in the EEG have also been noted in healthy subjects administered melatonin, we propose that the clinical effects as well as the EEG changes noted after treatment with MF were mediated by the pineal gland which previously has been implicated in the pathophysiology of PD.

1146

The effects of inverter magnetic fields on early seed germination of mung beans

The biological effects of extremely low frequency magnetic fields (ELF MFs) on living organisms have been explored in many studies. Most of them demonstrate the biological effects caused by 50/60 Hz magnetic fields or pulsed magnetic fields. However, as the development of power electronics flourishes, the magnetic fields induced are usually in other different waveforms. This study aims to assess the effects of magnetic fields generated by inverter systems on the early growth of plants using mung beans as an example. In the experiment, an inverter which can produce sinusoidal pulsed width modulation (SPWM) voltages was used to drive 3 specially made circular coils and an AC motor. Six SPWM voltages with different fundamental frequencies (10, 20, 30, 40, 50, and 60 Hz) set on the inverter drive the circuit to produce the specific kinds of MFs. The results indicate that the magnetic field induced by a 20 or 60 Hz SPWM voltage has an enhancing effect on the early growth of mung beans, but the magnetic fields induced by SPWM voltages of other frequencies (30, 40, and 50 Hz) have an inhibitory effect, especially at 50 Hz. Bioelectromagnetics. 2008 Wiley-Liss, Inc.

1147

The effects of low-dosed and high-dosed low-frequency electromagnetic fields on microcirculation and skin temperature in healthy subjects

The purpose of this randomized double-blind cross-over study was to investigate whether a low-dosed pulsed low-frequency magnetic field or a high-dosed pulsed low-frequency magnetic field improves the cutaneous microcirculation and alters the temperature of the foot. Twelve healthy subjects (five women, seven men) aged on average 25.8 years participated in the trial. Based on a randomization list, one of the following three interventions was applied for 30 min through a cushion placed below the non-dominant foot: either a pulsed low-dosed magnetic field (100 uT, basic frequency 30 Hz with a frequency modulation) or a pulsed high-dosed magnetic field (8.4 mT, 10 Hz), or sham treatment. The individual treatment sessions were applied in intervals of one week, at the same time of the day. Cutaneous microcirculation (laser Doppler flowmetry) and temperature (infra-red thermovision) were measured in the dorsum of the foot and the great toe every 5 min during the intervention, and 5 and 10 min post-intervention. With both pulsed low-dosed magnetic field and pulsed high-dosed magnetic field, just as with the sham treatment, a minor drop in temperature and decrease in microcirculation took place. A two-way repeated-measures analysis of variance revealed no significant difference between the interventions for any parameter. It was concluded that a local application of a pulsed low-frequency magnetic field to the foot did not enhance temperature or cutaneous microcirculation in healthy subjects.

1148

The effects of non-thermal pulsed electromagnetic energy on wound healing of pressure ulcers in spinal cord-injured patients: a randomized, double-blind study.

the objective of this randomized, double-blind study was to determine if non-thermal pulsed electromagnetic energy treatment significantly increases the healing rate of pressure ulcers in patients with spinal cord injuries. Subjects included volunteers admitted to a Veterans Administration hospital in New York over a two-year period and consisted of 30 male spinal cord injured patients, 20 with stage II and 10 with stage III pressure ulcers. Subjects were given non-thermal pulsed high frequency electromagnetic energy treatment for 30 minutes twice daily for 12 weeks or until healed. The percentage of pressure ulcers healed was measured at one week. Of the 20 patients with stage II pressure ulcers, the active group had significantly increased rate of healing with a greater percentage of ulcer healed at one week than the control group. After controlling for the baseline status of the pressure ulcer, active treatment was independently associated with a significantly shorter median time to complete healing of the ulcer. Stage III pressure ulcers healed faster in the treatment group but the sample size was limited. For spinal cord-injured men with a stage to pressure ulcers, active non-thermal pulsed electromagnetic energy treatment significantly improved healing.

1149

The effects of picoTesla range magnetic fields on perceptual organization and visual memory in parkinsonism

Drawing tasks, both free and copied, have achieved a central position in the neuropsychological evaluation of constructional abilities in brain injured patients. The Rey-Osterrieth Complex Figure Test was devised in early 1940s as a tool to investigate perceptual organization and visual memory. The Bicycle Drawing Test is used as a measure of mechanical reasoning as well as visuographic functioning. Recent reports have demonstrated that extracranial treatment with magnetic fields (MF) in the picoTesla range improves constructional abilities including visuoperceptive functions in Parkinsonian patients. To evaluate further the effects of these extremely weak MF on cognitive functions in Parkinsonism, I investigated in a 69 year old fully medicated Parkinsonian patient the influence of a single, extracranial application of MF on the patient's performance on the Complex Figure (copy and recall) as well as the Bicycle Drawing Test. Results of the trial showed that a 30 minute application of MF produced a dramatic improvement in the patient's ability to copy and recall the Complex Figure. This treatment was also associated with a marked improvement in the performance of bicycle drawing with reversal of the Parkinsonian micrographia. Collectively, these findings demonstrate that this treatment modality may reverse some of the cognitive impairments associated with Parkinsonism which usually are not improved by treatment with dopaminergic or anticholinergic medications.

1150

The effects of pulsed electromagnetic fields on blood vessel growth in the rabbit ear chamber

A double-blind, controlled trial of the effects of pulsed electromagnetic fields on capillary growth in the rabbit ear chamber in adult New Zealand white rabbits has been performed. Three waveforms have been investigated. The first, a pulse burst waveform, produced a significant increase in the rate of growth of the vascular tissue within the chamber, but had no effect on macroscopic tissue maturation. The second and third, two different single pulse waveforms, had, in contrast, no significant effect on the rate of vascular growth and only an effect on vessel characteristics, with increased maturation of vessels using the second waveform. It is concluded that some of the observed effects of pulsed electromagnetic fields on tissue healing may be mediated through a primary effect on vascular growth.

1151

The effects of pulsed electromagnetism on fresh fracture healing: osteochondral repair in the rat femoral groove

Some clinical studies have claimed significant reductions in the healing time of fresh fractures with the use of pulsed electromagnetic fields (PEMFs). Animal models, however, have produced more equivocal results. This investigation examined the effects of PEMF treatment on an osteochondral defect placed in the patellofemoral groove of the rat. The results indicated that PEMF enhances early vascular reaction and suppresses initial pannus proliferation. Early chondrogenesis and bone formation were consistently stimulated, and the restoration of normal bone trabeculae advanced. Pulsed electromagnetic field treatment therefore may be useful in advancing repair during the early proliferative stage. Later results were variable and suggest that prolonged use may have deleterious effects, enhancing chondrogenesis beyond a point observed in normal repair and thus delaying normal subsurface trabeculation.

1152

The effects of pulsed magnetic fields of the type used in the stimulation of bone fracture healing

The main impression received by us whilst writing this review is the scarcity of technical data in the clinical studies and the total absence of controlled trials. The spatial patterns of the stimulus have not been measured, and no experiments have proved that there is an effect from the magnetic field itself. Control experiments using dummy stimulators must be done, since the orthopaedic management of the stimulated patients is different from conventional management and this may have significant and beneficial clinical effects. There is no clinical study at present which shows a direct therapeutic benefit due solely to the application of the magnetic field component of the overall treatment regime. The in vivo animal experiments suggest that there may be effects due to the magnetic fields used but results are very scarce compared with the accumulated data from direct current stimulation. In vitro studies are far removed from the clinical situation, but could nonetheless prove useful if the opportunity of controlling the stimulus can be taken. In the majority of experiments, approximately spatially uniform magnetic fields have been applied, but temporal changes in the magnetic field and both spatial and temporal variation in electric field lead to non-uniform stimulation. Little attempt has been made to assess or control the induced fields by defining the system geometry. Hence it is still unknown whether effects are due to the magnetic field, the induced extracellular electric field or to fields induced at cellular level by regions of different conductivity. In conclusion, we believe that, unlike steady current work, the pulsed magnetic field treatment of fractures has not been sufficiently well investigated and, although some of the animal experiments suggest significant effects, the benefit of using magnetic fields in the clinical management of non-union and delayed union has still to be proven. Double blind trials are essential and, if these do prove that there is a definite effect of the fields, the mechanisms must then be studied using a combination of theoretical, in vivo and in vitro techniques.

1153

The effects of pulsed magnetic fields on chick embryo cartilaginous skeletal rudiments in vitro

The biological response of cultured 7-day embryonic chick tibiae to small alternating currents induced by pulsed magnetic fields (PMFs) was investigated. It was found that continuous exposure to PMFs over 7 days did not alter the overall DNA content of rudiments nor the incorporation of 3H-thymidine when compared with control tibiae. The overall collagen content of explants was slightly reduced by PMF exposure whilst the incorporation of 3H-proline was significantly suppressed. The synthesis of sulphated glycosaminoglycans was also measured in terms of 35SO4--incorporation, but PMF treatment failed to alter the levels of isotope incorporation. These results suggest that, whereas noncollagenous, and possibly collagenous, protein synthesis is affected by PMF exposure, glycosaminoglycan synthesis is not. Histological and electron microscopical observations substantiated this interpretation and revealed selective inhibition of matrix secretion in the periphery of the proliferative epiphyseal zones in experimental explants. High-power electron microscope examination of these zones showed that PMF-exposed matrix was sparsely invested with fibrous protein while elements of the stellate reticulum had formed large aggregates which were often clumped about the cell membrane. The results are discussed in terms of the possible role of naturally occurring potentials in the development and maintenance of connective tissue systems such as cartilage and bone.

1154

The effects of samarium-cobalt magnets and pulsed electromagnetic fields on tooth movement

The purpose of this study was to determine whether the application of either samarium cobalt magnets or pulsed electromagnetic fields could increase the rate and amount of orthodontic tooth movement observed in guinea pigs. In addition, the objective was to evaluate the effect of a magnetic field on bony physiology and metabolism and to monitor for possible systemic side effects. Fifteen grams of laterally directed orthodontic force were applied to move the maxillary central incisors of a sample of 18 young male Hartley guinea pigs divided into three groups: group 1, an orthodontic coil spring was used to move the incisors; group 2, a pair of samarium-cobalt magnets provided the tooth moving force; and group 3, a coil spring was used in combination with a pulsed electromagnetic field. The results showed that both the static magnetic field produced by the samarium-cobalt magnets and the pulsed electromagnetic field used in combination with the coil spring were successful in increasing the rate of tooth movement over that produced by the coil springs alone. The mechanism producing this effect appears to have involved a reduction in the "lag" phase often seen in orthodontic tooth movement. Both magnetically stimulated groups also showed increases in both the organization and amount of new bone deposited in the area of tension between the orthodontically moved maxillary incisors.

1155

The electrical stimulation of tibial osteotomies.

40 consecutive patients needing about this to the oral osteotomy exhibited significantly more advanced stages of healing when exposed to electromagnetic field stimulation when compared to an exposed controls.

1156

The electromagnetic response of human skin in the millimetre and submillimetre wave range

Recent studies of the minute morphology of the skin by optical coherence tomography revealed that the sweat ducts in human skin are helically shaped tubes, filled with a conductive aqueous solution. This, together with the fact that the dielectric permittivity of the dermis is higher than that of the epidermis, brings forward the supposition that as electromagnetic entities, the sweat ducts could be regarded as low Q helical antennas. The implications of this statement were further investigated by electromagnetic simulation and experiment of the in vivo reflectivity of the skin of subjects under varying physiological conditions (Feldman et al 2008 Phys. Rev. Lett. 100 128102). The simulation and experimental results are in a good agreement and both demonstrate that sweat ducts in the skin could indeed behave as low Q antennas. Thus, the skin spectral response in the sub-Terahertz region is governed by the level of activity of the perspiration system and shows the minimum of reflectivity at some frequencies in the frequency band of 75-110 GHz. It is also correlated to physiological stress as manifested by the pulse rate and the systolic blood pressure. As such, it has the potential to become the underlying principle for remote sensing of the physiological parameters and the mental state of the examined subject.

1157

The electrophysiological "delayed effect" of focal interictal epileptiform discharges. A low resolution electromagnetic tomography (LORETA) study

Collating the findings regarding the role of focal interictal epileptiform discharges (IEDs) on CNS functions raises the possibility that IEDs might have negative impact that outlasts the duration of the spike-and-wave complexes. The aim of this study was the electrophysiological demonstration of the "delayed effect" of the IEDs. 19-channel, linked-ears referenced, digital waking EEG records of 11 children (aged 6-14 years, eight with idiopathic, three with cryptogenic focal epilepsy, showing a single spike focus) were retrospectively selected from our database. A minimum of 20 (preferably, 30), 2-s epochs containing a single focal spike-and-wave complex were selected (Spike epochs). Thereafter, Postspike-1 (Ps1), Postspike-2 (Ps2) and Postspike-3 (Ps3) epochs were selected, representing the first and second seconds (Ps1), the third and fourth seconds (Ps2) and the fifth and sixth seconds (Ps3) after the Spike epoch, respectively. Interspike epochs (Is) were selected at a distance at least 10s after the Spike epoch. Individual analysis: the frequency of interest (FOI=the individual frequency of the wave component of the IEDs), and the region of interest (ROI=the site of the IEDs) were identified by reading the raw EEG waveform and the instant power spectrum. Very narrow band LORETA (low resolution electromagnetic tomography) analysis at the FOI and ROI was carried out. Age-adjusted, Z-transformed LORETA "activity" (=current source density, amperes/meters squared) was compared in the Spike, Ps1, Ps2, Ps3 and Is epochs. Findings: the greatest (uppermost pathological) Z-scores and the greatest spatial extension of the LORETA-abnormality were always found in the Spike epochs, followed by the gradual decrease of activity in terms of severity and spatial extension in the Ps1, Ps2, Ps3 epochs. The lowest (baseline) level and extension of the abnormality was found in the Is epochs. Group analysis: average values of activity across the patients were computed for the temporal decrease of the abnormality. Findings: a clear tendency for the decrease of abnormality was demonstrated. Conclusion: the "delayed effect" of the IEDs was demonstrated electrophysiologically and quantified. The method may be utilized in the individual assessment of the effect of IEDs on cortical activity, the degree and temporo-spatial extension of the abnormality.

1158

The excretion of 6-hydroxymelatonin sulfate in healthy young men exposed to electromagnetic fields emitted by cellular phone -- an experimental study

OBJECTIVES: It is quite likely that non-visible electromagnetic fields (EMF) may affect melatonin production. Some studies confirmed this hypothesis and showed that extremely low EMF altered pineal function in animals and humans. Thus, it is reasonable to suppose that EMF emitted by cellular phones may also influence secretion of melatonin. The present study sought to evaluate possible effect of the exposure to EMF emitted by cellular phone on 6-hydroxymelatonin sulfate (6-OHMS) excretion, which reflects melatonin levels in blood. MATERIAL AND METHODS: The examined group consisted of 9 healthy males aged 19-29 years. The experiment was performed under controlled conditions (the light intensity-50 lx till midnight and 0 lx during night). Each person was examined twice: on a day without exposure (control day, C-day) and on a day with continuous exposure (60 min. exposure from cellular phone, frequency 900 MHz, pulsed with 217 Hz, pulse with 576 micros, SAR 1.23 W/kg, E-day). From 7 p.m. to 8 p.m. they used a cellular phone. The subjects did not know which day was E-day, and which was C-day. From 8 p.m. till midnight the subjects listened to music and than they slept till 7 a.m. next day. Urine samples were collected at 7 p.m., at midnight, and at 7 a.m. in the same way in C-day as in E-day. Sample were frozen for later ELISA analysis of 6-OHMS. The 6-OHMS ELISA kit from Immuno-Biological Laboratories (Hamburg) was used for measurement of 6-OHMS. The data were analysed using Wilcoxon matched-pairs signed-ranks test for each subject and for the whole group. We compared 6-OHMS level on the E-day and on the C-day separately for 3 time-points - 7 p.m., midnight, 7 a.m. RESULTS: Mean 6-OHMS level in both experiments did not differ significantly for any of the respective time points. Circadian variations of 6-OHMS level were detected in all subjects. CONCLUSIONS: The results of our investigation has demonstrated that EMF emitted by cellular phones has no distinct influence on the melatonin level.

1159

The generation of reactive-oxygen species associated with long-lasting pulse-induced electropermeabilisation of mammalian cells is based on a non-destructive alteration of the plasma membrane

Chinese hamster ovary (CHO) cells in suspension were subjected to pulsed electric fields suitable for electrically mediated gene transfer (pulse duration longer than 1 ms). Using the chemiluminescence probe lucigenin, we showed that a generation of reactive-oxygen species (oxidative jump) was present when the cells were electropermeabilised using millisecond pulses. The oxidative jump yield was controlled by the extent of alterations allowing permeabilisation within the electrically affected cell area, but showed a saturating dependence on the pulse duration over 1 ms. Cell electropulsation induced reversible and irreversible alterations of the membrane assembly. The oxidative stress was only present when the membrane permeabilisation was reversible. Irreversible electrical membrane disruption inhibited the oxidative jump. The oxidative jump was not a simple feedback effect of membrane electropermeabilisation. It strongly controlled long-term cell survival. This had to be associated with the cell-damaging action of reactive-oxygen species. However, for millisecond-cumulated pulse duration, an accumulation of a large number of short pulses (microsecond) was extremely lethal for cells, while no correlation with an increased oxidative jump was found. Cell responses, such as the production of free radicals, were present during electropermeabilisation of living cells and controlled partially the long-term behaviour of the pulsed cell.

1160

The influence of chronic exposure to low frequency pulsating magnetic fields on concentrations of FSH, LH, prolactin, testosterone and estradiol in men with back pain

OBJECTIVES: There is widespread public concern that electromagnetic fields might be hazardous. However, studies on the biological effects of magnetic fields (MFs) have not always been consistent. Influence of extremely-low frequency MFs used in physiotherapy on endocrine system was rarely examined. Therefore, the aim of the present study was to investigate the concentrations of some pituitary (FSH, LH, prolactin) and sex (testosterone, estradiol) hormones in men with back pain exposed to magnetic fields applied during magnetotherapy or magnetostimulation over the period of three weeks. MATERIAL AND METHODS: The study was performed on 20 men aged 28-62 years (mean+/-SEM: 46.4+/-2.0 years) suffering from chronic low back pain who underwent magnetotherapy (10 patients, mean age+/-SEM: 48.4 years, range: 28-62 years) or subjected to magnetostimulation (10 patients, mean age+/-SEM: 44.3 years, range: 34-52 years) for 15 days (daily at 10:00 h, with weekend breaks). Blood samples were collected at 08:00 before magnetic field application, one day and one month following the application. Concentrations of hormones were measured by micromethod of chemiluminescence. RESULTS: Both magnetotherapy and magnetostimulation lowered levels of prolactin.The levels of LH decreased significantly one month after magnetotherapy in comparison with the baseline whereas following magnetostimulation slight but insignificant increase was observed. Estradiol concentrations were significantly lower one day and one month following magnetosimulation in comparison to the baseline and did not change after magnetotherapy. No statistically significant changes were observed in levels of FSH and testosterone after either magnetotherapy or magnetosimulation at any time examined. CONCLUSION: Magnetic fields applied in physiotherapy exert no or very subtle effect on concentrations of FSH, LH, prolactin, testosterone, and estradiol in men.

1161

The influence of extremely low frequency magnetic fields on cytoprotection and repair

Ischemia-reperfusion injuries, such as those suffered from various types of cardiovascular disease, are major causes of death and disability. For relatively short periods of ischemia, much of the damage is potentially reversible and in fact, does not occur until the influx of oxygen during the reperfusion stage. Because of this, there is a window of opportunity to protect the ischemic tissue. Here, we review several mechanisms of protection, such as heat shock proteins, opioids, collateral blood flow, and nitric oxide induction, and the evidence indicating that magnetic fields may be used as a means of providing protection via each of these mechanisms. While there are few studies demonstrating direct protection with magnetic field therapies, there are a number of published reports indicating that electromagnetic fields may be able to influence some of the biochemical systems with protective applications. Bioelectromagnetics 28:16–30, 2007.

1163

The influence of the pineal gland on migraine and cluster headaches and effects of treatment with picoTesla magnetic fields

For over half a century the generally accepted views on the pathogenesis of migraine were based on the theories of Harold Wolff implicating changes in cerebral vascular tone in the development of migraine. Recent studies, which are based on Leao's concept of spreading depression, favor primary neuronal injury with secondary involvement of the cerebral circulation. In contrast to migraine, the pathogenesis of cluster headache (CH) remains entirely elusive. Both migraine and CH are cyclical disorders which are characterised by spontaneous exacerbations and remissions, seasonal variability of symptoms, and a relationship to a variety of environmental trigger factors. CH in particular has a strong circadian and seasonal regularity. It is now well established that the pineal gland is an adaptive organ which maintains and regulates cerebral homeostasis by "fine tuning" biological rhythms through the mediation of melatonin. Since migraine and CH reflect abnormal adaptive responses to environmental influences resulting in heightened neurovascular reactivity, I propose that the pineal gland is a critical mediator in their pathogenesis. This novel hypothesis provides a framework for future research and development of new therapeutic modalities for these chronic headache syndromes. The successful treatment of a patient with an acute migraine attack with external magnetic fields, which acutely inhibit melatonin secretion in animals and humans, attests to the importance of the pineal gland in the pathogenesis of migraine headache.

1165

The management of craniofacial pain in a pain relief unit

This paper reports the results of 34 craniofacial pain sufferers who were treated at the Dudley Pain Relief Unit over a 1-year period. Most of the patients were referred by their general medical practitioners. They were adults representing all age groups, with a female-male ratio of 4:1. The average history of pain was 5.5 years. Neuralgic pain (as distinct from temporomandibular joint dysfunction syndrome, migrainous disorders, and pain of iatrogenic origin) was most frequently seen. Oral drug therapy, local injection of corticosteroids and analgesics, peripheral neurolysis, magnetotherapy, hypnotherapy, and acupuncture were the lines of management available. By the end of this study period, pain had been relieved or eliminated in 30 of the patients (88%).

1166

The mechanism of magnetic field-induced increase of excitability in hippocampal neurons

The influence of a pulsed magnetic field (PMF) on hippocampal evoked potentials has been investigated in vitro. The exposure to PMF (0.16 Hz, 15 mT) applied for 30 min amplified the population spike and the slope of EPSP recorded from stratum pyramidale and stratum radiatum respectively. This amplification was additive to previously induced LTP and occurred in an NMDA-independent way. The increase in the activity of electrical synapses accompanied PMF-induced amplification of evoked potentials. Since PMF exposure modified paired-pulse facilitation and paired-pulse inhibition, it was concluded that it modifies excitatory and inhibitory processes in the hippocampus. Control experiments revealed that observed effects were exclusively related to PMF exposure. The results support and extend our previous research indicating a significant influence of magnetic fields on hippocampal physiology.

1168

The protective effect of caffeic acid phenethyl ester (CAPE) on oxidative stress in rat liver exposed to the 900 MHz electromagnetic field

In this study, we aimed to investigate the possible protective effects of caffeic acid phenethyl ester (CAPE) on lipid peroxidation (LPO) and the activities of antioxidant enzymes in the liver of rats exposed to the 900 MHz electromagnetic field (EMF). EMF of cellular phones may affect biological systems by increasing free radical, which appear mainly to enhance LPO, and by changing the antioxidative activities of liver, thus leading to oxidative damage. CAPE, an active component of propolis extract, exhibits antioxidant properties and several studies suggest that supplementation with antioxidant can influence EMF exposure induced hepatotoxicity. Thirty male Sprague-Dawley rats were divided into three groups: control (n = 10), 900 MHz EMF (n = 10) and 900 MHz EMF + CAPE (n = 10). CAPE was injected intraperitoneally for 30 days before exposure to EMF. Liver tissue was removed to study the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), xanthine oxidase (XO) and the levels of LPO. The activities of XO, CAT and level of LPO increased in the 900 MHz electromagnetic field (EMF) group compared with the control group, although XO, CAT activities and LPO levels were decreased by 900 MHz EMF + CAPE administration. The activities of SOD and GSH-Px decreased in the 900 MHz EMF group compared with the control group, although their levels were increased by EMF + CAPE administration. It can be concluded that CAPE may prevent the 900 MHz EMF-induced oxidative changes in liver by strengthening the antioxidant defense system by reducing reactive oxygen species and increasing antioxidant enzyme activities.

1169

The relation between the specific absorption rate and electromagnetic field intensity for heterogeneous exposure conditions at mobile communications frequencies

The relation between the incident electromagnetic field strength and both the whole-body and the local specific absorption rate (SAR) was investigated for typical heterogeneous exposure scenarios for frequencies relevant for mobile communication. The results were compared to results from plane wave exposure. Heterogeneous exposure arises from multiple path propagation of the electromagnetic waves to the location of interest. It is shown that plane wave exposure does not represent worst-case exposure conditions. When the electric field strength arising at plane wave exposure is compared to the electric field strength averaged over the volume of the human body occurring during multipath exposure, 12% of all heterogeneous cases examined represent worse exposure conditions than plane wave exposure for whole-body exposure at 946 MHz, 15% at 1840 MHz, and 22% at 2140 MHz. The deviation between plane wave and heterogeneous whole-body SAR ranges from -54% to 54%. For partial-body SAR averaged over 10 g of tissue, a range from -93% to 209% was found when comparing multiple wave exposure to single incoming plane waves. The investigations performed using the Visible Human as phantom showed that the basic restrictions are met as long as the reference levels are not exceeded. However, this must not be necessarily the case when different phantoms are used to perform similar investigations because recent studies demonstrated that reference levels might not be conservative when phantoms of children are used. Therefore, the results of this work indicate the need to extend the investigations to numerical simulations with additional human phantoms representing parts of the human population having different anatomy and morphology compared to the phantom used within the frame of this project. This also applies to phantoms of children. Bioelectromagnetics, 2009. (c) 2009 Wiley-Liss, Inc.

1170

The results of a double-blind trial of pulsed electromagnetic frequency in the treatment of Perthes' disease

A double-blind trial of the use of pulsed electro-magnetic frequency (PEMF) in the treatment of Perthes' disease was constructed by using this therapy to supplement a long-practised non-weight-bearing orthotic treatment, the Birmingham Containment Splint. Twenty-one boys with Perthes' disease were treated with this combined regimen; they were divided into two groups. All wore the orthosis but the treatment coil was inactive in one group; the state of coil activity was unknown to clinic staff or patients. The duration of non-weight-bearing orthotic treatment needed to achieve a stated degree of femoral head reconstitution was recorded; there was no discernible difference between the two groups, treatment time being 12 months in one group and 12.5 months in the other. It was concluded that PEMF cannot be offered for the therapy of Perthes' disease.

1171

The role of charge transport in nanoporous films under electromagnetic irradiation

Recently, attention has been paid to surface plasmon waves occurring at an interface as responsible for selective absorption of light and enhancement of the photoelectron current. Interest for plasmon resonance phenomena in photovoltaics is groving, for applications in very thin film-based devices. We discuss in this paper d-c open circuit voltages of nominally undoped mesoporous films of TiO2 of the type used in dye-sensitized cells, under exposure to visible and ambient electromagnetic radiation. In non-sensitized films we interpret these as arising from absorption of electromagnetic energy at plasmon resonances determined by the morphology of the films and subsequent electronic diffusion through the nanocrystals of TiO2. Typical order of magnitude of voltages V(oc) approximately equal to 1 mV indicates an equivalent temperature T approximately equal to 3 K of the radiation involved, which suggests ambient microwave background as responsabile of the effect. The order of magnitude of short-circuit current I approximately equal to 10(-9) A is consistent with experimental data of the diffusion coefficient of the oxide. We find from these data the efficiency of the process is of typical order 1% for nanocrystals of 10 nm typical size. Confirmation of these results are obtained by a Montecarlo simulation of transport taking into account the overall mechanisms of scattering, including phonons, imperfections and doping centres, and traps. We find that TiO2 is a n-type self doped material, with typical doping concentrations N (I) approximately equal to 10(18) cm(-3). The same route is applied to dye-sensitized cells under exposure to solar light for which we find a maximum efficiency of 10% in agreement with certified results on Graetzel's cells, independent of the nanocrystal size. We conclude that the enhancement of the efficiency of these electrochemical cells may be obtained by optimizing the charge current within the mesoporous films, which can be obtained by maximizing the diffusion coefficient.

1172

The safety of digital mobile cellular telephones with minute ventilation rate adaptive pacemakers

In vitro tests suggest that rate adaptive pacemakers using changes in transthoracic impedance to vary pacing rate may be affected by digital mobile telephones. Electromagnetic fields generated by digital mobile telephones (Global System for Mobile [GSM]) represent a potential source of electromagnetic interference (EMI) for the Telectronics META rate adaptive pacemakers, which use transthoracic impedance as a sensor to determine changes in minute ventilation. Sixteen implanted Telectronics META pulse generators were exposed to 25-W simulated GSM transmissions (900-MHz carrier pulsed at 2, 8, and 217 Hz with a pulse width of 0.6 ms) and the antenna of a 2-W digital mobile telephone (900-MHz, 217-Hz pulse, 0.6-ms pulse width). The 12 dual and four single chamber devices were programmed to maximum sensitivity and assessed in unipolar and bipolar settings and rate adaptive and nonrate adaptive modes. In all cases of EMI, testing was repeated at lower, more routinely set bipolar sensitivity levels. At maximum sensitivity, 11 of 16 devices displayed no evidence of EMI. Brief ventricular triggering occurred in 2, a brief pause in 1, a combination of both in 1, and a brief episode of pacemaker-mediated tachycardia in 1. With pulse generators programmed to more routine sensitivities, only one device displayed rare single beat ventricular triggering. No changes in minute ventilation rate adaptive pacing were observed. At maximum unipolar sensitivities, the META series of rate adaptive pacemakers are resistant to clinically important EMI from digital mobile telephones. Set at routine sensitivities, these devices perform reliably in the presence of digital mobile telephones.

1173

The sensitivity of tussiphonography for assessing the effectiveness of treatment

Our previous studies have demonstrated that tussiphonogram is suitable not only for the detection of pathological condition in the respiratory tract but also for treatment effectiveness assessment. The purpose of this study was to evaluate the possibilities of tussiphonography in detection of already little pathological changes in the airways and lungs. Therefore the changes of voluntary cough sound indexes were compared with pulmonary function tests in selected group of asthmatics before and after a pulsatile electromagnetic therapy in which the effect of therapy on pulmonary function tests was minimal. After magnetotherapy in 18 patients with increased expiratory forced lung capacity by 7.3% and increased peak inspiratory flow by 31.7% in average the voluntary cough sound intensity decreased by 37.8%, the sound duration shortened by 11% and the sound pattern showed the tendency to normalization. The improvement of mentioned cough indexes was absent in 17 patients who were treated by magnetotherapy too, but at the same time suffered from respiratory viral infection and in 22 patients treated only with climatotherapy and antiasthmatics. Changes of flow-volume loops in patients were not in the close relation to other followed indices. The correlation analysis showed a functional connection in relative differences of cough sound indices and some pulmonary function tests. The results confirmed the suitability of tussiphonography to indicate even mild pathological changes in respiratory tract. (Fig. 4, Ref. 21.)

1174

The strength of EPR and ENDOR techniques in revealing structure-function relationships in metalloproteins

Recent technological and methodological advances have strongly increased the potential of electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) techniques to characterize the structure and dynamics of metalloproteins. These developments include the introduction of powerful pulsed EPR/ENDOR methodologies and the development of spectrometers operating at very high microwave frequencies and high magnetic fields. This overview focuses on how valuable information about metalloprotein structure-function relations can be obtained using a combination of EPR and ENDOR techniques. After an overview of the historical development and a limited theoretical description of some of the key EPR and ENDOR techniques, their potential will be highlighted using selected examples of applications to iron-, nickel-, cobalt-, and copper-containing proteins. We will end with an outlook of future developments.

1175

The theory of DNA separation by capillary electrophoresis

The Human Genome has been sequenced in large part owing to the invention of capillary electrophoresis. Although this technology has matured enough to allow such amazing achievements, the physical mechanisms at play during separation have yet to be completely understood and optimized. Recently, new separation regimes and new physical mechanisms have been investigated. The use of free-flow electrophoresis and new modes of pulsed-field electrophoresis have been suggested, while we have observed a shift towards single nucleotide polymorphism analysis and microchip technologies. A strong theoretical basis remains essential for the efficient development of new methods.

1176

The treatment of non-union by pulsed electromagnetic fields combined with a Denham external fixator

Fifteen cases of non-union of a long bone were treated by pulsed electromagnetic fields in combination with a Denham external fixator. Thirteen united within a few months and a controlled trial has been established to determine the contribution made by PEMF.

1177

The use of nonlinear dielectric spectroscopy to monitor the bioelectromagnetic effects of a weak pulsed magnetic field in real time

Nonlinear dielectric spectroscopy (NLDS) was used to detect interaction of a pulsed magnetic field (PMF) with membrane protein dynamics in aggregating Dictyostelium discoideum amoebae. In the experiments reported here, a strong nonlinear dielectric response of Dictyostelium discoideum cells is shown, and a distinctive nonlinear dielectric response of cells previously exposed to PMF is shown. The method of NLDS is shown to be capable of monitoring and charting the dynamic frequency response of the cell to an electromagnetic field.

1179

The use of pulsed electromagnetic fields with complex modulation in the treatment of patients with diabetic polyneuropathy

Clinical and electroneuromyographic studies were performed in 121 patients with diabetic polyneuropathy (DPN) before and after courses of treatment with pulsed electromagnetic fields with complex modulation (PEMF-CM) at different frequencies (100 and 10 Hz). Testing of patients using the TSS and NIS LL scales demonstrated a correlation between the severity and frequency of the main subjective and objective effects of disease and the stage of DPN. The severity of changes in the segmental-peripheral neuromotor apparatus--decreases in muscle bioelectrical activity, the impulse conduction rate along efferent fibers of peripheral nerves, and the amplitude of the maximum M response--depended on the stage of DPN and the duration of diabetes mellitus. The earliest and most significant electroneuromyographic signs of DPN were found to be decreases in the amplitude of the H reflex and the Hmax/Mmax ratio in the muscles of the lower leg. Application of PEMF-CM facilitated regression of the main clinical symptoms of DPN, improved the conductive function of peripheral nerves, improved the state of la afferents, and improved the reflex excitability of functionally diverse motoneurons in the spinal cord. PEMF-CM at 10 Hz was found to have therapeutic efficacy, especially in the initial stages of DPN and in patients with diabetes mellitus for up to 10 years.

1181

Therapeutic effect of pulsed electromagnetic field in conservative treatment of subacromial impingement syndrome

Subacromial impingement syndrome (SIS) is a frequent cause of shoulder pain. Our purpose in this double-blinded, randomized, and controlled study was to demonstrate whether the pulsed electromagnetic field (PEMF) provides additional benefit when used with other conservative treatment modalities in acute phase rehabilitation program of SIS. Forty-six patients with unilateral shoulder pain who had been diagnosed as having SIS were included in this trial. The cases were randomly separated into two groups. All cases received a treatment program for 3 weeks consisting of Codman's pendulum exercises and subsequent cold pack gel application on shoulders with pain 5 times a day, restriction of daily activities that require the hands to be used over the head, and meloxicam tablet 15 mg daily. One group was given PEMF; the other group was given sham PEMF daily, 25 min per session, 5 days per week for 3 weeks. Shoulder pain during rest and activity and which causes disturbance of sleep was evaluated using a visual analogue scale, and total Constant score investigated shoulder function. Daily living activities were evaluated by shoulder disability questionnaire. Results were assessed before and after treatment. When compared with the baseline values, significant improvements in all these variables were observed at the end of the treatment in both groups (p<0.05). No significant difference between treatments was observed for any of these variables (p>0.05). There is no convincing evidence that electromagnetic therapy is of additional benefit in acute phase rehabilitation program of SIS.

1182

Therapeutic effects of alternating current pulsed electromagnetic fields in multiple sclerosis

Multiple sclerosis is the third most common cause of severe disability in patients between the ages of 15 and 50 years. The cause of the disease and its pathogenesis remain unknown. The last 20 years have seen only meager advances in the development of effective treatments for the disease. No specific treatment modality can cure the disease or alter its long-term course and eventual outcome. Moreover, there are no agents or treatments that will restore premorbid neuronal function. A host of biological phenomena associated with the disease involving interactions among genetic, environmental, immunologic, and hormonal factors, cannot be explained on the basis of demyelination alone and therefore require refocusing attention on alternative explanations, one of which implicates the pineal gland as pivotal. The pineal gland functions as a magnetoreceptor organ. This biological property of the gland provided the impetus for the development of a novel and highly effective therapeutic modality, which involves transcranial applications of alternating current (AC) pulsed electromagnetic fields in the picotesla flux density. This review summarizes recent clinical work on the effects of transcranially applied pulsed electromagnetic fields for the symptomatic treatment of the disease.

1183

Therapeutic effects of electromagnetic fields in the stimulation of connective tissue repair.

The therapeutic effects of electric and magnetic fields have been studied largely for their promotion of connective tissue repair. The most widely studied application concerns bone repair and deals with acceleration of the healing of fresh fractures, delayed and non-unions, incorporation of bone grafts, osteoporosis, and osteonecrosis. More recently the effects of these fields upon the repair of cartilage and soft fibrous tissues have been described. In all these experimental systems and clinical applications an acceleration of extracellular matrix synthesis and tissue healing has been observed. A degree of specificity, in terms of the parameters of applied energy and biological response, is hypothesized.

1184

Therapeutic effects of pulsed magnetic fields on joint diseases

The present paper describes the effects of pulsed magnetic fields (MF) on diseases of different joints, in chronic as well as acute conditions where the presence of a phlogistic process is the rule. Optimal parameters for MF applications were sought at the beginning of the study and then applied for 11 years; a technical modification in the MF generator was introduced 5 years ago to satisfy the requirement of a hypothesis advanced to understand the mechanism of MF treatment. 3,014 patients were treated by means of MF at extremely low frequencies and intensities. Patient follow-up was pursued as constantly as possible. Pain removal, recovery of joint mobility and maintenance of the improved conditions represented the parameters for judging the results as good or poor. The chi-square test was applied in order to evaluate the probability that the results are not casual. A general average value of 78.8% of good results and 21.2% of poor results was obtained. Higher (82%) percentages of good results were observed when single joint diseases were considered with respect to multiple joint diseases (polyarthrosis); in the latter, the percentage of good results was definitely lower (66%). The high percentage of good results obtained and the absolute absence of both negative results and undesired side-effects, together with the therapeutic advantage due to a technical modification in the MF generator, led to the conclusion that magnetic field treatment is an excellent physical therapy in cases of joint diseases. A hypothesis is advanced that external magnetic fields influence transmembrane ionic activity.

1185

Therapeutic electromagnetic field effects on angiogenesis and tumor growth

BACKGROUND: A new approach to cancer therapy based on the application of therapeutic electromagnetic fields (TEMF) has been developed by EMF Therapeutics, Inc., Chattanooga, TN, USA. This study was designed to assess the effect of TEMF on tumor vascularization and growth of murine 16/C mammary adenocarcinoma cells in C3H/HeJ mice. MATERIALS AND METHODS: Implanted tumors were allowed to grow for seven days until the tumor volume reached 100 mm3 before treatment was started. Mice (20 per control, 10 per EMF exposed group) received treatment (10 minutes per day with 0, 10 mT, 15 mT or 20 mT) with a 120 pulses per second pulsating magnetic field. Tumor growth was assessed throughout the treatment period. The extent of tumor vascularization was evaluated by immunohistochemical staining for CD31. RESULTS: Exposure to TEMF significantly reduced tumor growth, significantly reduced the percentage of area stained for CD31 indicating a reduction in the extent of vascularization and there was a concomitant increase in the extent of tumor necrosis. CONCLUSION: A novel TEMF treatment safely reduced growth and vascularization of implanted breast cancers in mice. IMPLICATION: TEMF may prove a useful adjuvant to increase the therapeutic index of conventional cancer therapy.

1186

Therapy with pulsed electromagnetic fields in aseptic loosening of total hip protheses: a prospective study

Aseptic loosening is the most common problem of hip arthroplasties, limiting its long term success. We report a study of pulsed electromagnetic field (PEMF) treatment in 24 patients with this complication. At the end of treatment, six months and one year later, pain and hip movements improved significantly with the exception of flexion and extension. There was significant improvement in both isotope scans and ultrasonography, but not in plain X-ray. The decreased pain and improved function suggest that PEMF is effective in improving symptoms of patients with loose hip replacement. No improvement, however, can be expected in patients with severe pain due to gross loosening.

1187

Thirty minutes mobile phone use has no short-term adverse effects on central auditory pathways

OBJECTIVE: To investigate whether pulsed high-frequency electromagnetic field (pulsed EM field) emitted by a mobile phone for 30 min has short-term adverse effects on the human central auditory system. METHODS: We studied the auditory brainstem response (ABR), the ABR recovery function and middle latency response (MLR) before and after using a mobile phone for 30 min in 15 normal hearing volunteers. RESULTS: None of the 3 measures were affected by exposure to pulsed EM field emitted by a mobile phone for 30 min. CONCLUSIONS: Based on the ABR and MLR methods utilized in the study, we conclude that 30 min mobile phone use has no short-term adverse effects on the human auditory system.

1188

Three-dimensional prepolarized magnetic resonance imaging using rapid acquisition with relaxation enhancement

Prepolarized MRI (PMRI) with pulsed electromagnets has the potential to produce diagnostic quality 0.5- to 1.0-T images with significantly reduced cost, susceptibility artifacts, specific absorption rate, and gradient noise. In PMRI, the main magnetic field cycles between a high field (B(p)) to polarize the sample and a homogeneous, low field (B(0)) for data acquisition. This architecture combines the higher SNR of the polarizing field with the imaging benefits of the lower field. However, PMRI can only achieve high SNR efficiency for volumetric imaging with 3D rapid imaging techniques, such as rapid acquisition with relaxation enhancement (RARE) (FSE, TSE), because slice-interleaved acquisition and longitudinal magnetization storage are both inefficient in PMRI. This paper demonstrates the use of three techniques necessary to achieve efficient, artifact-free RARE in PMRI: quadratic nulling of concomitant gradient fields, electromotive force cancelation during field ramping, and phase compensation of CPMG echo trains. This paper also demonstrates the use of 3D RARE in PMRI to achieve standard T(1) and fat-suppressed T(2) contrast in phantoms and in vivo wrists. These images show strong potential for future clinical application of PMRI to extremity musculoskeletal imaging and peripheral angiography.

1189

Thresholds for 60 Hz magnetic field stimulation of peripheral nerves in human subjects

The goal of the research reported here is to narrow the range of uncertainty about peripheral nerve stimulation (PNS) thresholds associated with whole body magnetic field exposures at 50/60 Hz. This involved combining PNS thresholds measured in human subjects exposed to pulsed magnetic gradient fields with calculations of electric fields induced in detailed anatomical models of the body by that same exposure system. PNS thresholds at power frequencies (50/60 Hz) can be predicted from these data due to the wide range of pulse durations (70 mus to 1 ms), the length of the pulse trains (several tens of ms), and the exposure of a large part of the body to the magnetic field. These data together with the calculations of the rheobase electric field exceeded in 1% (E(1%)) of two anatomical body models, lead to a median PNS detection threshold of 47.9 +/- 4.4 mT for a uniform 60 Hz magnetic field exposure coronal to the body. The threshold for the most sensitive 1% of the population is about 27.8 mT. These values are lower than PNS thresholds produced by magnetic fields with sagittal and vertical orientations or nonuniform exposures.

1190

Time course reconstruction of fetal cardiac signals from fMCG: independent component analysis versus adaptive maternal beat subtraction

M-mode and pulsed Doppler echocardiography, cardiotocography and transabdominal fetal ECG are available in clinical practice to monitor fetal cardiac activity during advancing gestation, but none of these methods allows the direct measurement of morphological and temporal parameters for fetal rhythm assessment. Fetal magnetocardiograms (fMCGs) are noninvasive recordings of magnetic field variations associated with electrical activity of the fetal heart obtained with superconducting sensors positioned over the maternal abdomen inside a shielded room. Because of maternal cardiac activity, fMCGs are contaminated by maternal components that need to be eliminated to reconstruct fetal cardiac traces. The aim of the present work was to use two methods working in the time domain, an independent component analysis algorithm (FastICA) and an adaptive maternal beat subtraction technique (AMBS), for the retrieval of fetal cardiac signals from fMCGs. Detection rates of both methods were calculated, and FastICA and AMBS performances were compared in the context of clinical applications by estimating several temporal and morphological characteristics of the retrieved fetal traces, such as the shape and duration P-QRS-T waves, arrhythmic beat detection and classification, and noise reduction. Quantitative and qualitative comparison produced figures that always suggested that FastICA was superior to AMBS from the perspective of clinical use of the recovered fetal signals.

1192

Time-varying magnetic fields: effects of orientation on chondrocyte proliferation

The purpose of this study was to determine the effect of orientation of pulsed electromagnetic fields (PEMFs) on cellular proliferation and extracellular matrix synthesis. Bovine articular chondrocytes were cultured in PEMFs (repetitive pulse at 72 Hz) generated using Helmholtz coils oriented either parallel (horizontal) or perpendicular (vertical) to the plane of cell adhesion. Dissipation of signal energy in the form of heat increased the temperature of the PEMF coils by 2 degrees C and the tissue culture medium by 1 degree C. Therefore, control coils, which emitted no PEMFs, were heated to the temperature of PEMF coils by circulating water. Chondrocytes were cultured in 16-mm-well culture plates, and the data for individual wells were pooled as triplicates. Although not observed by microscopic examination of individual wells, positionally dependent electric field effects may be minimized by this approach. PEMFs generated by coils oriented vertically significantly decreased chondrocyte proliferation. The effect was dependent on the concentration of serum in the culture media. At 3% serum concentration, the total cell number attained after 10 days of culture was reduced by 50% in stimulated cultures when compared with controls. At 5% serum concentration, there was no effect. PEMFs applied by coils oriented horizontally did not alter proliferation of articular chondrocytes. PEMFs had no effect on synthesis of extracellular matrix by chondrocytes plated at high density, irrespective of orientation.

1193

Timing of pulsed electromagnetic field stimulation does not affect the promotion of bone cell development

Pulsed electromagnetic field (PEMF) devices have been used clinically to promote the healing of surgically resistant fractures in vivo. However, there is a sparsity of data on how the timing of an applied PEMF effects the osteogenic cells that would be present within the fracture gap. The purpose of this study was to examine the response of osteoblast-like cells to a PEMF stimulus, mimicking that of a clinically available device, using four protocols for the timing of the stimulus. The PEMF signal consisted of a 5 ms pulse burst (containing 20 pulses) repeated at 15 Hz. Cultures of a human osteosarcoma cell line, SaOS-2, were exposed to the four timing protocols, each conducted over 3 days. Protocol one stimulated the cells for 8 h each day, protocol two stimulated the cells for 24 h on the first day, protocol three stimulated the cells for 24 h on the second day, and protocol four stimulated the cells for 24 h on the third day. Cells were seeded with either 25,000 or 50,000 cells/well (24-well cell culture plates). All assays showed reduced proliferation and increased differentiation (alkaline phosphatase activity) in the PEMF stimulated cultures compared with the control cultures, except for protocol four alkaline phosphatase measurements. No clear trend was observed between the four protocols; however this may be due to cell density. The results indicated that an osteoblast-like cell line is responsive to a 15 Hz PEMF stimulus, which will stimulate the cell line to into an increasing state of maturity.

1194

Toward a self-generating magnetic dynamo: the role of turbulence

Turbulent flow of liquid sodium is driven toward the transition to self-generating magnetic fields. The approach toward the transition is monitored with decay measurements of pulsed magnetic fields. These measurements show significant fluctuations due to the underlying turbulent fluid flow field. This paper presents experimental characterizations of the fluctuations in the decay rates and induced magnetic fields. These fluctuations imply that the transition to self-generation, which should occur at larger magnetic Reynolds number, will exhibit intermittent bursts of magnetic fields.

1195

Transcranial AC pulsed applications of weak electromagnetic fields reduces freezing and falling in progressive supranuclear palsy: a case report

Freezing is a common and disabling symptom in patients with Parkinsonism. It affects most commonly the gait in the form of start hesitation and sudden immobility often resulting in falling. A higher incidence of freezing occurs in patients with progressive supranuclear palsy (PSP) which is characterized clinically by a constellation of symptoms including supranuclear ophthalmoplegia, postural instability, axial rigidity, dysarthria, Parkinsonism, and pseudobulbar palsy. Pharmacologic therapy of PSP is currently disappointing and the disease progresses relentlessly to a fatal outcome within the first decade after onset. This report concerns a 67 year old woman with a diagnosis of PSP in whom freezing and frequent falling were the most disabling symptoms of the disease at the time of presentation. Both symptoms, which were rated 4 on the Unified Parkinson Rating Scale (UPRS) which grades Parkinsonian symptoms and signs from 0 to 4, with 0 being normal and 4 being severe symptoms, were resistant to treatment with dopaminergic drugs such as levodopa, amantadine, selegiline and pergolide mesylate as well as with the potent and highly selective noradrenergic reuptake inhibitor nortriptyline. Weekly transcranial applications of AC pulsed electromagnetic fields (EMFs) of picotesla flux density was associated with approximately 50% reduction in the frequency of freezing and about 80-90% reduction in frequency of falling after a 6 months follow-up period. At this point freezing was rated 2 while falling received a score of 1 on the UPRS. In addition, this treatment was associated with an improvement in Parkinsonian and pseudobulbar symptoms with the difference between the pre-and post EMF treatment across 13 measures being highly significant (p < .005; Sign test). These results suggest that transcranial administration AC pulsed EMFs in the picotesla flux density is efficacious in the treatment of PSP.

1196

Transcranial stimulation of the human frontal eye field by magnetic pulses

Single transcranial magnetic pulsed stimuli were applied over the cortical area of the putative right frontal eye field (FEF) in 11 healthy subjects. An especially designed figure of eight shaped twin coil was used, to focus the stimulus, the strength of which was adjusted to the individual motor threshold of the left hand muscles. Eye positions and movements were recorded by an infrared reflection technique. Three different experiments were performed: 1. Stimulation during different primary gaze position did not evoke any discernible eye movement. 2. Stimulation just prior to visually elicited horizontal saccades did not cause a significant alteration of the latency, velocity, or amplitude of the saccades. 3. Only stimulation during an antisaccade task induced a significant latency prolongation, when the stimulus was applied between 50 to 90 ms after the target flashed up. This latency prolongation was found in all subjects for the antisaccades to the right, with a statistically significant average latency difference of +66 +/- 55.5 ms. In contrast, the antisaccades to the left were prolonged in the female subjects only by an average of +98 +/- 41.8 ms (p = 0.0064), whereas in the male subjects they did not alter with stimulation (average difference: -3 +/- 41.9 ms, p = 0.753). Significant latency prolongations were only obtained when the magnetic FEF stimuli were applied within a vulnerable period, which varied from subject to subject.

1197

Transcriptional patterns in the X chromosome of Sciara coprophila following exposure to magnetic fields

We previously demonstrated that exposure of salivary gland cells of the dipteran, Sciara coprophila, to either asymmetrical or symmetrical changing magnetic fields results in an increase in the incorporation of radioactive uridine into RNA. The present report is an analysis of the grain count distribution over the X chromosome of Sciara in transcription autoradiograms following exposure of the salivary gland cells to two pulsed magnetic signals and a 72-Hz sine wave signal. The results show augmented uptake of 3H-uridine into nascent RNA chains following short exposures of the cells to magnetic fields. Transcription is augmented in previously active loci, as well as at chromosome regions that are not detectable as active in control cells. The quantitative pattern of RNA synthesis in transcription autoradiograms is hypothesized to be signal specific on the basis of differences in grain counts over significantly labelled chromosome sites.

1198

Transient effect of weak electromagnetic fields on calcium ion concentration in Arabidopsis thaliana

BACKGROUND: Weak magnetic and electromagnetic fields can influence physiological processes in animals, plants and microorganisms, but the underlying way of perception is poorly understood. The ion cyclotron resonance is one of the discussed mechanisms, predicting biological effects for definite frequencies and intensities of electromagnetic fields possibly by affecting the physiological availability of small ions. Above all an influence on Calcium, which is crucial for many life processes, is in the focus of interest. We show that in Arabidopsis thaliana, changes in Ca2+-concentrations can be induced by combinations of magnetic and electromagnetic fields that match Ca2+-ion cyclotron resonance conditions. RESULTS: An aequorin expressing Arabidopsis thaliana mutant (Col0-1 Aeq Cy+) was subjected to a magnetic field around 65 microtesla (0.65 Gauss) and an electromagnetic field with the corresponding Ca2+ cyclotron frequency of 50 Hz. The resulting changes in free Ca2+ were monitored by aequorin bioluminescence, using a high sensitive photomultiplier unit. The experiments were referenced by the additional use of wild type plants. Transient increases of cytosolic Ca2+ were observed both after switching the electromagnetic field on and off, with the latter effect decreasing with increasing duration of the electromagnetic impact. Compared with this the uninfluenced long-term loss of bioluminescence activity without any exogenic impact was negligible. The magnetic field effect rapidly decreased if ion cyclotron resonance conditions were mismatched by varying the magnetic fieldstrength, also a dependence on the amplitude of the electromagnetic component was seen. CONCLUSION: Considering the various functions of Ca2+ as a second messenger in plants, this mechanism may be relevant for perception of these combined fields. The applicability of recently hypothesized mechanisms for the ion cyclotron resonance effect in biological systems is discussed considering it's operating at magnetic field strengths weak enough, to occur occasionally in our all day environment.

1199

Transient electric birefringence of agarose gels. I. Unidirectional electric fields

The orientation of agarose gels in pulsed electric fields has been studied by the technique of transient electric birefringence. The unidirectional electric fields ranged from 2 to 20 V/cm in amplitude and 1 to 100 s in duration, values within the range typically used for pulsed field gel electrophoresis (PFGE). Agarose gels varying in concentration from 0.3 to 2.0% agarose were studied. The sign of the birefringence varied randomly from one gel to another, as described previously [J. Stellwagen & N.C. Stellwagen (1989), Nucleic Acids Research, Vol. 17, 1537-1548]. The sign and amplitude of the birefringence also varied randomly at different locations within each gel, indicating that agarose gels contain multiple subdomains that orient independently in the electric field. Three or four relaxation times of alternating sign were observed during the decay of the birefringence. The various relaxation times, which range from 1 to approximately 120 s, can be attributed to hierarchies of aggregates that orient in different directions in the applied electric field. The orienting domains range up to approximately 22 microns in size, depending on the pulsing conditions. The absolute amplitude of the birefringence of the agarose gels increased approximately as the square of the electric field strength. The measured Kerr constants are approximately 5 orders of magnitude larger than those observed when short, high-voltage pulses are applied to agarose gels. The increase in the Kerr constants in the low-voltage regime parallels the increase in the relaxation times in low-voltage electric fields. Birefringence saturation curves in both the low- and high-voltage regimes can be fitted by theoretical curves for permanent dipole orientation. The apparent permanent dipole moment increases approximately as the 1.6 power of fiber length, consistent with the presence of overlapping agarose helices in the large fiber bundles orienting in low-voltage electric fields. The optical factor is approximately independent of fiber length. Therefore, the marked increase in the Kerr constants observed in the low-voltage regime is due to the large increase in the electrical orientation factor, which is due in turn to the increased length of the fiber bundles and domains orienting in low-voltage electric fields. Since the size of the fiber bundles and domains approximates the size of the DNA molecules being separated by PFGE, the orientation of the agarose matrix in the applied electric field may facilitate the migration of large DNA molecules during PFGE.

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Transient electric birefringence of agarose gels. II. Reversing electric fields and comparison with other polymer gels

The transient electric birefringence of low electroendosmosis (LE) agarose gels oriented by pulsed unidirectional electric fields was described in detail in Part I [J. Stellwagen and N. C. Stellwagen (1994), Biopolymers, Vol. 34, p. 187]. Here, the birefringence of LE agarose gels in rapidly reversing electric fields, similar in amplitude and duration to those used for field inversion gel electrophoresis, is reported. Symmetric reversing electric fields cause the sign of the birefringence of LE agarose gels, and hence the direction of orientation of the agarose fibers, to oscillate in phase with the applied electric field. Because of long-lasting memory effects, the alternating sign of the birefringence appears to be due to metastable changes in gel structure induced by the electric field. If the reversing field pulses are equal in amplitude but different in duration, the orientation behavior depends critically on the applied voltage. If E < 7 V/cm, the amplitude of the birefringence gradually decreases with increasing pulse number and becomes unmeasurably small. However, if E > 7 V/cm, the amplitude of the birefringence increases more than 10-fold after approximately 20 pulses have been applied to the gel, suggesting that a cooperative change in gel structure has occurred. Because there is no concomitant change in the relaxation times of the orienting particles, the large increase in the amplitude of the birefringence must be due to an increase in the number of agarose fibers and/or fiber bundles orienting in the electric field, which in turn indicates a cooperative breakdown of the noncovalent "junction zones" that cross-link the fibers into the gel matrix. The sign of the birefringence of LE agarose gels is always positive after extensive junction zone breakdown, indicating that the agarose fibers and fiber bundles preferentially orient parallel to the electric field when they are freed from the constraints of the gel matrix. Three other gel-forming polymers, high electroendosmosis (HEEO) agarose (a more highly charged agarose), beta-carrageenan (a stereoisomer of agarose), and polyacrylamide (a chemically cross-linked polymer) were also studied in unidirectional and rapidly reversing electric fields. The birefringence of HEEO agarose gels in reversing fields is very similar to that of LE agarose gels, suggesting that the orientation anomalies are not due to the occasional charged residues on the agarose backbone chain. The beta-carrageenan gels exhibit variable orientation behavior in reversing electric fields, suggesting that its internal gel structure is not as tightly interconnected as that of agarose gels.(ABSTRACT TRUNCATED AT 400 WORDS)

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