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PubMed2005

Analytical solutions of electric potential and impedance for a multilayered spherical volume conductor excited by time-harmonic electric current source: application in brain EIT.

A model of a multilayered spherical volume conductor with four electrodes is built. In this model, a time-harmonic electric current is injected into the sphere through a pair of drive electrodes, and electric potential is measured by the other pair of measurement electrodes. By solving the boundary value problem of the electromagnetic field, the analytical solutions of electric potential and impedance in the whole conduction region are derived. The theoretical values of electric potential on the surface of the sphere are in good accordance with the experimental results. The analytical solutions are then applied to the simulation of the forward problem of brain electrical impedance tomography (EIT). The results show that, for a real human head, the imaginary part of the electric potential is not small enough to be ignored at above 20 kHz, and there exists an approximate linear relationship between the real and imaginary parts of the electric potential when the electromagnetic parameters of the innermost layer keep unchanged. Increase in the conductivity of the innermost layer leads to a decrease of the magnitude of both real and imaginary parts of the electric potential on the scalp. However, the increase of permittivity makes the magnitude of the imaginary part of the electric potential increase while that of the real part decreases, and vice versa.

Algorithms↗
PubMed2002

One-shot percutaneous electrical nerve stimulation vs. transcutaneous electrical nerve stimulation for low back pain: comparison of therapeutic effects.

OBJECTIVE: To investigate the therapeutic effects of one shot of low-frequency percutaneous electrical nerve stimulation one shot of transcutaneous electrical nerve stimulation in patients with low back pain. DESIGN: In total, 133 low back pain patients were recruited for this randomized, control study. Group 1 patients received medication only. Group 2 patients received medication plus one shot of percutaneous electrical nerve stimulation. Group 3 patients received medication plus one shot of transcutaneous electrical nerve stimulation. Therapeutic effects were measured using a visual analog scale, body surface score, pain pressure threshold, and the Quebec Back Pain Disability Scale. RESULTS: Immediately after one-shot treatment, the visual analog scale improved 1.53 units and the body surface score improved 3.06 units in the percutaneous electrical nerve stimulation group. In the transcutaneous electrical nerve stimulation group, the visual analog scale improved 1.50 units and the body surface score improved 3.98 units. The improvements did not differ between the two groups. There were no differences in improvement at 3 days or 1 wk after the treatment among the three groups. CONCLUSIONS: Simple one-shot treatment with percutaneous electrical nerve stimulation or transcutaneous electrical nerve stimulation provided immediate pain relief for low back pain patients. One-shot transcutaneous electrical nerve stimulation treatment is recommended due to the rarity of side effects and its convenient application.

Adolescent↗
PubMed1984

[The relationship between electrical callus formation and the amount of electricity].

Electrical stimulation to enhance callus formation has been in use for some time now. This experiment was undertaken to find the relationship between electrical callus formation and the amount of electricity. In this experiment, the long bones of canines were stimulated by direct current and observed microscopically for callus formation. Moreover, distribution patterns of electric potential and current density were calculated theoretically by finite element method. The results are summarized as follows: Electrical callus formation was observed in the medullary canal with 8.7-20 microA direct current. Electrical callus is fibrous ossification and the peak of callus formation is from fourteen to twenty one days. There is no difference in volume and/or speed of callus formation between the simple and the constant direct current. Using platinum electrodes, the amount of callus formed around the cathode and anode is the same. To prevent electrolysis of the tissues, distance between electrodes must be kept at a minimum. On the other hand, the surface area of the electrodes must be widen to keep the electric potential at the minimum level. The area of callus formation is related to 5-10 microA/cm2 of electric current density.

Animals↗
PubMed2006

Identification and distribution of chondroitin sulfate in the three electric organs of the electric eel, Electrophorus electricus (L.).

The electrogenic tissue of the electric eel Electrophorus electricus (L.) is distributed in three well-defined electric organs, the Main electric organ, Sach's organ and Hunter's organ. Sulfated glycosaminoglycan (GAG) composition was characterized in the three electric organs of the electric eel. Sulfated GAGs were analyzed in the electric organs using metachromatic staining, biochemical analysis including electrophoresis before and after specific enzymatic or chemical degradations, and immunostaining with an antibody against chondroitin sulfate (CS). Our results showed in the three electric organs that CS was the main sulfated GAG species detected, accompanied by small and diminutive amounts of CS/dermatan sulfate hybrid chains and heparan sulfate (HS), respectively. However, HS was not detected in the Sach's organ. CS was predominantly detected in the innervated membrane face of the electroplaques in the three electric organs. Our findings extend previous observations on the GAG composition in the electric organs of E. electricus and provide new information regarding the tissue distribution and location of CS.

Animals↗
PubMed2004

[Mechanism of the role of electrical field in electrical injury].

OBJECTIVE: To explore the acting mechanism of electrical field in electrical injury. METHODS: Thirty-six New Zealand white rabbits were employed in the study and were randomly divided into 7 groups. There were 12 rabbits in group 1 and 4 in each group of other 6 groups. The animal model of nonthermal electrical injury previously replicated was employed in the study. Experiment with paralleled muscular fibers in electrical field was carried out in groups 2 approximately 4, while that of vertical muscular fibers in electrical field in groups 5-7. Anatomical examination was done to determine the index of deep burn injury (IDBI) in all groups of rabbits at 0, 2 and 24 postburn hour (PBH). Histological and ultrastructural examination, gamma picturing and isotope scanning with 99mTc were done in group 1 at 2 PBH. RESULTS: There was no obvious skin injury in the white rabbits in group 1. Deep tissue necrosis was identified under the small electrode. Constant muscular spasm was observed in the inner side of the thigh. The muscles in paralleled electrical field suffered more severe injury than those in vertical one. Tissue injury was more severe in those areas with higher current density, less soft tissue, and also in the central area of the axis of the electric field. There were obvious changes in the perfusion and blood pool phases in these areas as observed with the aid of 99mTc. Light microscopic examination revealed swelling and necrosis of muscular fibers. Under electron microscopy, it was found that there were edema and dissolution with separation of lipid molecular layers of cell membrane, Shortened nucleus with partial dissolution of nuclear membrane, increased heparin granules within nucleus, swelling of mitochondria and endoplasmic reticulum, myofilament dissolution, expanded gap between myofilament and decreased number of heparin granules. CONCLUSION: Non-thermal tissue injury in the electrical field, in terms of cell, ultrastructural and molecular levels, was induced and aggravated by all the factors constituting high voltage electrical field.

Animals↗
PubMed2000

Non-Hodgkin's lymphoma among electric utility workers in Ontario: the evaluation of alternate indices of exposure to 60 Hz electric and magnetic fields.

OBJECTIVES: To examine associations between non-Hodgkin's lymphoma (NHL) and exposures to 60 Hz magnetic and electric fields in electric utility workers with a series of indices that capture a variety of aspects of field strength. METHODS: The study population consisted of 51 cases of NHL and 203 individually matched controls identified from within a cohort of male electric utility workers in Ontario. Odds ratios were calculated for several exposure indices with conditional logistic regression models. Aspects of exposure to electric and magnetic fields that were modelled included: the percentage of time spent above selected threshold field intensities, mean transitions in field strength, SD, and the arithmetic and geometric mean field intensities. RESULTS: For the most part, there was a lack of an association between exposure indices of magnetic fields and the incidence of NHL. Subjects in the upper tertile of percentage of time spent above electric field intensities of 10 and 40 V/m had odds ratios of 3.05 (95% confidence interval (95% CI) 1. 07 to 8.80) and 3.57 (1.30 to 9.80), respectively, when compared with those in the lowest tertile. Moreover, the percentages of time spent above these electric field thresholds were significant predictors of case status over and above the association explained by duration of employment and the arithmetic or geometric mean exposure. CONCLUSIONS: These data suggest that exposures above electric field threshold intensities of 10 and 40 V/m are important predictors of NHL. Consequently, the findings support the hypothesis that electric fields may play a promoting part in the aetiology of this cancer. Further occupational studies that include assessment of exposure to electric fields and measures of field strength above similar threshold cut off points are needed to confirm these findings.

Case-Control Studies↗
PubMed2001

Electric activity of the rectosigmoid canal and its relation to rectal and sigmoid electric activity: an evidence of a sphincteric function of the rectosigmoid canal.

We have previously demonstrated that the rectosigmoid junction is more than a junction: it is a segment with a mean length of 2.8 cm which we termed the 'rectosigmoid canal' (RSC). Our data support the existence of a physiologic and anatomic sphincter at the RSC which regulates the passage of stools from the sigmoid colon (SC) to the rectum (R). In view of its sphincteric action we investigated the hypothesis that the RSC has a higher electric activity than that of the SC and R. The tests were performed during repair of huge incisional hernia in 11 subjects (age 46.7(12.5 years; 8 women). The electric activity was recorded by means of 2 monopolar electrodes applied to each of the SC, RSC and R. The RSC was then anesthetized with xylocaine and the electric activity of SC, RSC and R was recorded after 10 minutes and one hour. The test was repeated using saline instead of xylocaine. The SC, RSC and R exhibited electric activity in the form of pacesetter potentials (PPs) and action potentials (APs). The PPs were monophasic in the SC and triphasic in the RSC and R. The frequency, amplitude and conduction velocity of the waves recorded from the RSC and R had higher readings (p<0.05) than those from the SC. The RSC and R showed a similar frequency and conduction velocity, but the RSC had a higher amplitude (p<0.05). Ten minutes after RSC anesthetization, electric waves were recorded from the SC but not from the RSC or R; electric activity returned one hour after anesthetization. Saline injection of the RSC did not affect the electric activity of the RSC, SC or R. The electric wave pattern and parameters of the RSC and R differed from those of the SC, suggesting that they are evoked by 2 different pacemakers. The similarity in pattern, frequency and conduction velocity of electric waves of RSC and R supposedly denotes that the rectal waves are a continuation of those of the RSC and that both are evoked by a single pacemaker located in the RSC. The higher amplitude of the RSC waves may be due to the thicker RSC musculosa in comparison to that of the SC and R and may by itself be an evidence of the sphincteric function of the RSC.

Adult↗
PubMed2001

Cutaneous electrical oscillation in a weakly electric fish, Gymnarchus niloticus.

An African electric fish, Gymnarchus niloticus. ceases its electric organ discharge for a prolonged time in response to external electrical signals. During the cessation of electric organ discharges from the electric organ, a weak sinusoidal signal (approximately 0.1 mV cm(-1)) near the fish's previous discharge frequency was recorded near the body. The oscillatory potentials at all points on the body surface were synchronized and had a complex spatial distribution. The source of the potential was determined to be within the dermal tissue. Electroreceptive central neurons that responded to a moving target near the fish with normal electric organ discharges also responded to the same target when the electric organ discharge was interrupted and the potential from the skin existed. This result suggests that the fish may be able to electrolocate objects without the discharge from the electric organ.

Animals↗
PubMed2005

Driving gastric electrical activity with electrical stimulation.

Gastric electrical stimulation (GES) therapy is generating a lot of interest, but it is still investigational. Its efficacy in driving gastric electrical activity and improving motility, and the ideal frequency for bringing this about are still controversial. In this study, a rule-based computer model of tissue electrical response to stimulation was developed to examine the interaction between tissue electrical refractoriness and the onset of tissue activation. The results were compared to response to GES in 8 dogs implanted with electrodes and strain gauges and stimulated at frequencies ranging from 3 to 30 cycles/min. Simulated electrical control activity at an intrinsic frequency of 5/min was entrained from 2.0 cycles/min to 7.92 cycles/min. The regularity of the ECA elicited by stimulation depended on the number of pulses injected. Electrical stimulation in canine stomach entrained the native electrical control activity from a baseline average of 5.14 +/- 0.32 cycles/min up to 9.2 cycles/min. Contractile response to stimulation at 20-30 cycles/min were significantly higher (p < 0.05). Computer simulation of GES may be a useful tool to complement and reduce some of the costs associated with empirical studies of gastric electrical stimulation in establishing its possible use in treating drug refractory gastroparesis.

Animals↗
PubMed2006

Electric fields in tumors exposed to external voltage sources: implication for electric field-mediated drug and gene delivery.

The intratumoral field, which determines the efficiency of electric field-mediated drug and gene delivery, can differ significantly from the applied field. Therefore, we investigated the distribution of the electric field in mouse tumors and tissue phantoms exposed to a large range of electric stimuli, and quantified the resistances of tumor, skin, and electrode-tissue interface. The samples used in the study included 4T1 and B16.F10 tumors, mouse skin, and tissue phantoms constructed with 1% agarose gel with or without 4T1 cells. When pulsed electric fields were applied to samples using a pair of parallel-plate electrodes, we determined the electric field and resistances in each sample as well as the resistance at the electrode-tissue interface. The electric fields in the center region of tissue phantoms and tumor slices ex vivo were macroscopically uniform and unidirectional between two parallel-plate electrodes. The field strengths in tumor tissues were significantly lower than the applied field under both ex vivo and in vivo conditions. During in vivo stimulation, the ratio of intratumoral versus applied fields was approximately either 20% or 55%, depending on the applied field. Meanwhile, the total resistance of skin and electrode-tissue interface was decreased by approximately 70% and the electric resistance at the center of both tumor models was minimally changed when the applied field was increased from 50 to 400 V/cm. These results may be useful for improving electric field-mediated drug and gene delivery in solid tumors.

Animals↗
PubMed2006

Thermal burn and electrical injuries among electric utility workers, 1995-2004.

This study describes the occurrence of work-related injuries from thermal-, electrical- and chemical-burns among electric utility workers. We describe injury trends by occupation, body part injured, age, sex, and circumstances surrounding the injury. This analysis includes all thermal, electric, and chemical injuries included in the Electric Power Research Institute (EPRI) Occupational Health and Safety Database (OHSD). There were a total of 872 thermal burn and electric shock injuries representing 3.7% of all injuries, but accounting for nearly 13% of all medical claim costs, second only to the medical costs associated with sprain- and strain-related injuries (38% of all injuries). The majority of burns involved less than 1 day off of work. The head, hands, and other upper extremities were the body parts most frequently injured by burns or electric shocks. For this industry, electric-related burns accounted for the largest percentage of burn injuries, 399 injuries (45.8%), followed by thermal/heat burns, 345 injuries (39.6%), and chemical burns, 51 injuries (5.8%). These injuries also represented a disproportionate number of fatalities; of the 24 deaths recorded in the database, contact with electric current or with temperature extremes was the source of seven of the fatalities. High-risk occupations included welders, line workers, electricians, meter readers, mechanics, maintenance workers, and plant and equipment operators.

Absenteeism↗
PubMed2004

Model development and numerical simulation of electric-stimulus-responsive hydrogels subject to an externally applied electric field.

Based on a multi-phasic mixture theory with consideration of ionic diffusion and convection, a multi-physic model, called the multi-effect-coupling electric-stimulus (MECe) model, is developed for simulation of responsive behavior of the electric-sensitive hydrogels when they are immersed into a bathing solution subject to an externally applied electric field. In the developed model, with chemo-electro-mechanical coupling effects, the convection-diffusion equations for concentration distribution of diffusive ions incorporate the influence of electric potential. The electroneutrality condition is replaced by the Poisson equation for distribution of electric potential. The steady and transient analyses of hydrogel deformation are easily carried out by the continuity and momentum equations of the mixture phase. Further, the computational domain of the present model covers both the hydrogel and the surrounding solution. In order to solve the present mathematical model consisting of multi-field coupled nonlinear partial differential governing equations, a hierarchical iteration technique is proposed and a meshless Hermite-Cloud method (HCM) is employed. The steady-state simulation of the electric-stimulus responsive hydrogel is numerically conducted when it is subjected to an externally applied electric field. The hydrogel deformation and the ionic concentrations as well as electric potentials of both the hydrogel and external solution are investigated. The parameter influences on the swelling behaviors of the hydrogel are also discussed in detail. The simulating results are in good agreement with the experimental data and they validate the presently developed model.

Biosensing Techniques↗
PubMed2004

Gender differences in electrical pain threshold responses to transcutaneous electrical nerve stimulation (TENS).

Gender differences in pain perception have been frequently discussed, but the documented gender-related pain-alleviating effects of non-pharmacological methods are sparse. In this study we aimed to investigate changes in electrical sensory thresholds and electrical pain thresholds, in response to high frequency transcutaneous electrical nerve stimulation, TENS, for 20 min in healthy women (n=29) and men (n=29). The thresholds were assessed pre-, during-, and post-TENS. The pattern of change in thresholds was evaluated with a rank-based statistical method regarding the level of systematic change, expressed as relative position (RP) and additional individual changes, expressed as relative rank variance (RV), with its 95% confidence intervals. Equal levels of systematic changes towards increased electrical sensory thresholds were seen in women and men post-TENS (RP, 0.35; 95% CI, 0.07, 0.63, and RP, 0.36; 95% CI, 0.17, 0.53, respectively). At the same point of time, systematic changes towards increased electrical pain thresholds were only seen in women (RP, 0.43; 95% CI, 0.27, 0.60), while they were unchanged in men (RP, -0.01; 95% CI, -0.13, 0.10). Significant additional individual variations were found in the women's responses of assessed electrical sensory and pain thresholds but not in the men's. It is concluded that both women and men responded with a significant increase of the electrical sensory threshold to high frequency TENS, but only women responded with increase of the electrical pain thresholds. The individual variation of the responses was greater in the women than in the men.

Adult↗
PubMed1987

Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 2: Comparative analysis of electrical stimulation and exercises to increase trunk muscle strength and endurance.

Several studies have shown positive correlations between muscle strength, flexibility, and the frequency of low-back pain. Weak trunk musculature and decreased endurance have thereby come to be identified as significant risk factors in the development of occupational back problems. Because it is widely accepted that exercise plays an important role in the conservative treatment and prevention of low-back pain, the goals of most rehabilitative programs involves improving the strength and endurance of the low-back pain patient. Whereas electrical stimulation has been shown to increase the muscle strength of the lower extremities, this effect has not been demonstrated for the trunk muscles. Part 2 is a prospective controlled study designed to document and to compare objectively the effects of electrical stimulation and exercise on trunk muscle strength. A total of 117 healthy women were divided randomly into four groups. Two groups received electrical stimulation with different electrical parameters, one group received exercises, and one group acted as a control group. The results showed that low-frequency electrical stimulation and exercises significantly (P less than .05) increased isokinetic back-muscle strength compared to the control and medium-high-frequency electrical stimulation groups. Both types of electrical stimulation, however, significantly increased (P less than .05) the endurance in the back muscles compared with the control and the exercise groups. This study showed that electrical stimulation may be a valuable treatment in the early care of low-back pain patients in maintaining and increasing strength and endurance of back muscles when a more active exercise program is too painful to perform.

Adolescent↗