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PubMed2005

Differences in quadriceps femoris muscle torque when using a clinical electrical stimulator versus a portable electrical stimulator.

BACKGROUND AND PURPOSE: There have been conflicting views and evidence reported in the literature concerning differences in muscle torque-generating capacities between clinical ("plug-in") console devices whose power source is provided by an electrical outlet (60 Hz, alternating current-driven) and portable electrical muscle stimulators (smaller, battery-operated stimulators). The purpose of this study was to compare the torque-generating capacity of the quadriceps femoris muscle during neuromuscular electrical stimulation (NMES) between a clinical neuromuscular electrical stimulator (VersaStim 380) and a portable neuromuscular electrical stimulator (Empi 300PV). SUBJECTS: Forty volunteer subjects with no known knee, neurological, or cardiovascular pathology (22 male, 18 female) participated in the study. METHODS: All subjects were tested with the clinical and portable stimulators on 2 separate days. Peak isometric torque of the quadriceps femoris muscle was measured using a Biodex dynamometer. Peak isometric quadriceps femoris muscle torque achieved during NMES and the average quadriceps femoris muscle torque integral produced over 10 NMES contractions were measured for each stimulator. Subjects also rated the amount of pain they experienced during the 10 NMES contractions using a numeric pain scale. Paired t tests were used to compare mean differences in measured variables between stimulator conditions. RESULTS: There were no differences in the peak torque or numeric pain ratings during the electrically stimulated contractions between stimulator conditions. The Empi 300PV produced a greater average torque integral compared with the VersaStim 380 during 10 electrically stimulated contractions (Empi 300PV=988.6-/+330.4 N.m-s, Versastim 380=822.7-/+292.6 N.m-s). DISCUSSION AND CONCLUSION: The portable Empi 300PV stimulator produced comparable levels of average peak torque at comparable levels of discomfort to those produced by the VersaStim 380 clinical stimulator. The Empi 300PV maintained greater amounts of torque production during a 10-contraction training session compared with the VersaStim 380. Based on these data, we believe that the Empi 300PV has the potential to produce adequate levels of torque production for NMES quadriceps femoris muscle performance training. Further study is needed to determine the effectiveness of using the Empi 300PV for quadriceps femoris muscle performance training.

Adult↗
PubMed1991

Physiologic measures of electrically evoked auditory system responsiveness: effects of pathology and electrical stimulation.

During the past years we have addressed issues of implant application in children related to candidate selection and time of implantation. The studies have incorporated an assessment of the utility of the electrically evoked middle latency response (EMLR) as a measure of responsiveness of the central auditory pathways elicited by electrical stimulation. We have demonstrated that the EMLR in the guinea pig is similar in waveform characteristics to the acoustically elicited MLR, that it is equal in sensitivity to the electrically evoked auditory brainstem response (EABR) and can be used to reflect the sensitivity of different sites of stimulation. Because of its longer latency, the EMLR shows far less sensitivity to electrical artifact than the EABR. While suprathreshold characteristics of the EMLR are affected by anesthesia (ketamine and xylazine), threshold is not. In the ototoxically deafened animal we have found a decrease in the amplitude input/output function slope with decreasing density of spiral ganglion cell survival and that moderately high intensity of electrical stimulation produces a temporary threshold shift (eTTS) in the EMLR. These data suggest that this measure may be useful in assessing surviving spiral ganglion cell populations for the selecting of candidates for implantation and establishing safe, functional, upper-limits of electrical stimulation for young children. Finally, we have found that early electrical stimulation can reduce the progress of spiral ganglion cell degeneration secondary to ototoxic-induced hair cell loss.

Acoustic Stimulation↗
PubMedDate not supplied

Spontaneous modulations of the electric organ discharge in the weakly electric fish, Apteronotus leptorhynchus: a biophysical and behavioral analysis.

Brown ghosts, Apteronotus leptorhynchus, are weakly electric gymnotiform fish whose wave-like electric organ discharges are distinguished by their enormous degree of regularity. Despite this constancy, two major types of transient electric organ discharge modulations occur: gradual frequency rises, which are characterized by a relatively fast increase in electric organ discharge frequency and a slow return to baseline frequency; and chirps, brief and complex frequency and amplitude modulations. Although in spontaneously generated gradual frequency rises both duration and amount of the frequency increase are highly variable, no distinct subtypes appear to exist. This contrasts with spontaneously generated chirps which could be divided into four "natural" subtypes based on duration, amount of frequency increase and amplitude reduction, and time-course of the frequency change. Under non-evoked conditions, gradual frequency rises and chirps occur rather rarely. External stimulation with an electrical sine wave mimicking the electric field of a neighboring fish leads to a dramatic increase in the rate of chirping not only during the 30 s of stimulation, but also in the period immediately following the stimulation. The rate of occurrence of gradual frequency rises is, however, unaffected by such a stimulation regime.

Animals↗
PubMed1994

Contribution of mechanical activity and electrical activity to cellular electrical uncoupling in ischemic rabbit papillary muscle.

We separated mechanical and electrical activity during ischemia and we assessed the contribution of each of these variables to ischemia induced cellular electrical uncoupling. In two groups of rabbit papillary muscles, mechanical and electrical activity at the onset of ischemia was abolished. We determined how this affected the time of onset of uncoupling. Also, action potential duration (APD80), conduction velocity and extracellular pH were recorded. In the first group, the BDM group, mechanical arrest was achieved with 10 mM BDM (2,3-butanedione monoxime). This had no effect on APD80 and conduction velocity. In the second group, the quiescent group, electrical as well as mechanical arrest was obtained by not stimulating the muscles. The effect of electrical arrest was estimated as the difference between this group and the BDM group. Mechanical arrest delayed uncoupling significantly (control: 14.6 +/- 0.9 (min), mean +/- S.E.M., n = 10; BDM: 19.3 +/- 1.1, n = 10; P < 0.025). Electrical arrest caused an even greater delay (quiescent: 41.6 +/- 4.6, n = 7; P < 0.001 v control and BDM). In the BDM group, these effects were not associated with a difference of APD80 during ischemia, but with a smaller decrease of conduction velocity. Delay of uncoupling correlated with delay of extracellular acidosis. We conclude: (1) mechanical and electrical activity both are significant determinants of ischemia induced uncoupling; (2) delay of uncoupling is associated with delay of extracellular acidosis, indicating a reduced rate of metabolism.

Action Potentials↗
PubMed2000

Deconvolution can be used in electrooptic studies to correct for non-ideal electric excitation pulses only when the electric dipole moment of the studied molecules is predominantly induced.

The electric field pulses used for most measurements of transient electrooptic properties such as birefringence and dichroism, are rectangular and assumed to be ideal, but in practice do all such pulses have non-zero rise and fall times. Claims have been made that this non-ideality may be taken into account by employing standard deconvolution techniques. We find that this approach yields exact results in the zero electric field limit when the electric dipole moment of the studied macromolecules is predominantly induced. However, for finite electric field strengths and/or macromolecules with partly or fully permanent electric dipole moments, we find that the deconvolution method yields erroneous estimates of the electrooptic relaxation times. When the decay time of the electric pulse and the electrooptic decay time are equal, and the system is operated in the Kerr domain, this systematic error for macromolecules with purely permanent electric dipole moment equals 37%. In a research field where the uncertainty of the reported relaxation times normally is assumed to be only a few percent this is an error that may seriously mislead unsuspecting users. We find that this systematic error can readily be avoided by employing standard numerical integration of a set of coupled first-order differential equations instead of the standard deconvolution techniques.

Birefringence↗
PubMed2000

Exposure to electromagnetic fields from use of electric blankets and other in-home electrical appliances and breast cancer risk.

Exposure to electromagnetic fields (EMFs) from use of electric blankets and other in-home electrical appliances has been hypothesized to increase breast cancer risk. To test the hypothesis, the authors analyzed data from a case-control study of female breast cancer conducted in Connecticut in 1994-1997. A total of 608 incident breast cancer patients and 609 age frequency-matched controls, 31-85 years old, were interviewed by trained study interviewers using a standardized, structured questionnaire to obtain information on lifetime use of various in-home electrical appliances. A total of 40% of the cases and 43% of the controls reported regular use of electric blankets in their lifetime, which gave an adjusted odds ratio of 0.9 (95% confidence interval (CI): 0.7, 1.1). For those who reported using electric blankets continuously throughout the night, the adjusted odds ratio was 0.9 (95% CI: 0.7, 1.2) when compared with never users. The risk did not vary according to age at first use, duration of use, or menopausal and estrogen receptor status. The authors also did not find an association between use of other major in-home electrical appliances and breast cancer risk. In conclusion, exposure to EMFs from in-home electrical appliance use was not found to increase breast cancer risk in this study.

Adult↗
PubMed1997

[Effect of electric field on erythrocyte sedimentation rate. VI--dependence of electric field pattern].

An automatic analyzer of RBC rheological parameters and a microscopic morphological observation technique were employed to investigate the effect of three electric field patterns on erythrocyte sedimentation and aggregation in a physiological saline solution and in autologous plasma, respectively. Experimental results indicate that in a physiological saline solution: 1) Erythrocytes present a lightly aggregation and settle faster by an alternative current electric field; 2) There exists no erythrocyte aggregation by a direct current electric field of constant current and the enhancement of erythrocyte sedimentation is caused only by the action of electric force; 3) Time courses of erythrocyte sedimentation fit well with an exponential type curve by a direct current electric field of constant voltage, and this exponential type sedimentation curve is not caused by erythrocyte aggregation but caused by the decrease of circuit current with time duration. Also shown by experimental results is that the above three electric field patterns all affect the erythrocyte sedimentation in antologous plasma in different contents, which predicts some change in erythrocyte aggregation behavior in autologous plasma by an external electric field.

Blood Sedimentation↗
PubMed1983

A new method for the simulation of electric fields, generated by electric fish, and their distorsions by objects.

Among the many species of fishes endowed with electric organs Mormyriformes and Gymnotoidei are known to emit and receive electric signals for the purposes of intraspecific communication and recognition of objects. Models which have been proposed for this electro-sensory system generally assume steady-state conditions. On the other hand, the very character of the signals itself and the idea that the cerebellum might be working as a clock point to the importance of the signal dynamics. Therefore a new approach to the simulation of electric fields is described in the paper. The basic idea is to superpose the fields of point charges in a way that the sum is in accordance with the fish's electric field. The same technique could be used to simulate the influence of objects on the electric field. Following a suggestion of Dr. E. Kasper I used a simpler but equal effective approach for object simulation consisting in the use of a dipole instead of point charges. The model described is easily applied to diverse situations and allows one to estimate the influence of various parameters (size, shape, and position) on the "electric image" of an object. Furthermore, the well-known behaviour of tailbending and its consequences in object recognition can be simulated. The results underline the importance of signal dynamics for species with pulse-type discharges.

Animals↗
PubMed1980

Electric currents, bone remodeling, and orthodontic tooth movement. II. Increase in rate of tooth movement and periodontal cyclic nucleotide levels by combined force and electric current.

Piezoelectric currents in mechanically stressed bone were implicated in the activation of bone cells. The objectives of this experiment were to determine the usefulness of exogenous electric currents in accelerating orthodontic tooth movement and to study the effect of electric-orthodontic treatment on periodontal cyclic nucleotides. Maxillary canines were tipped in five cats by 80 g force. Two groups of five cats each were treated by an electric-orthodontic procedure to one maxillary canine for 7 and 14 days, respectively. Teeth treated by force and electricity moved significantly faster than those treated by force alone. Enhanced bone resorption was observed near the anode (PDL compression site), while bone formation was pronounced near the cathode (PDL tension site). Staining for cyclic nucleotides was increased when electric stimulation was added to the mechanical force. These results suggest that orthodontic tooth movement may be accelerated by the use of locally applied electric currents.

Alveolar Process↗
PubMed1996

Childhood brain tumor occurrence in relation to residential power line configurations, electric heating sources, and electric appliance use.

To assess the relation between childhood brain tumor occurrence and exposure to potential sources of residential magnetic fields, a population-based case-control study of incident brain tumors was conducted in the Seattle, Washington, area at the Fred Hutchinson Cancer Research Center from 1989 to 1994 among children younger than age 20 years who were diagnosed from 1984 to 1990. The specific aims were to evaluate whether proximity to high-current residential power lines, as defined by the Wertheimer-Leeper code, or use of electric appliances or electric heating sources by the mother while pregnant or by the child before diagnosis were associated with increased risks of brain tumor occurrence. The mothers of 133 cases and 270 controls (recruited by random digit dialing) participated. Risk of brain tumor occurrence did not increase with increasing exposure, as indicated by the five-level Wertheimer-Leeper code. When exposure was dichotomized as high versus low, the odds ratio was 0.9 (95% confidence interval 0.5-1.5) and did not vary significantly by sex, age, or histology. No elevations in risk were found for ever versus never use of electric blankets, water beds, or electric heating sources. Odds ratios were slightly elevated for nine appliances and were at or below 1.0 for eight others. These data do not support the hypothesis that exposure to magnetic fields from high-current power lines, electric heating sources, or electric appliances is associated with the subsequent occurrence of brain tumors in children.

Adolescent↗
PubMed2003

Quest for standardisation of electrical sensory testing in the lower urinary tract: the influence of technique related factors on bladder electrical thresholds.

AIMS: The aim of this study is to determine the influence of technique-related factors on bladder electrical thresholds in order to establish more standardisation in electrical sensory testing in the lower urinary tract (LUT). METHODS: In 51 young healthy volunteers, electrical thresholds were determined in the bladder by using different techniques described in the literature. Within an individual, thresholds were repeatedly determined in the bladder while varying the position of the stimulating electrodes and the intravesical volume. RESULTS: The height of bladder electrical thresholds is influenced by the position of the stimulating electrodes and the volume of the intravesical fluid at the time of the examination. By filling the bladder, the sensitivity of the bladder toward electrical stimulation can be increased. CONCLUSIONS: Although the techniques to test electrical sensitivity have already proven to be a valuable tool in diagnosing the presence of neuropathy in the LUT, its full scope can only be evaluated after standardisation. Therefore, it is proposed that the position of the stimulating electrodes and the bladder volume at the time of the examination should be outlined in studies and standardised.

Adolescent↗
PubMed1993

Chronic electrical stimulation reverses deafness-related depression of electrically evoked 2-deoxyglucose activity in the guinea pig inferior colliculus.

The [14C]-2-deoxyglucose (2-DG) autoradiographic technique was used to study how auditory-related metabolic activity changes with deafness, and how chronic electrical stimulation of the deafened system may modify these changes. Guinea pigs were deafened by administration of kanamycin and ethacrynic acid. After nine weeks of deafness, the basal unstimulated uptake of 2-DG in the inferior colliculus (IC) was lower than in normal hearing control animals. 100 microA of acute cochlear electrical stimulation significantly increased 2-DG uptake in normal hearing animals but did not evoke a significant increase in four or nine week deafened animals. Electrically elicited 2-DG uptake in the IC is therefore depressed by prolonged deafness. In a second series of experiments, after four weeks of deafness, animals were chronically electrically stimulated via a cochlear implant 2.5-3.5 h a day, five days a week for five weeks at 100 microA. Acute cochlear electrical stimulation following this chronic stimulation significantly increased 2-DG uptake in the contralateral IC over unstimulated levels. This suggests that some depressive effects of profound deafness on the auditory brain stem may be reduced or reversed with chronic electrical stimulation by a cochlear implant.

Animals↗
PubMed2000

Time to recover from atrial hormonal, mechanical, and electrical dysfunction after successful electrical cardioversion of persistent atrial fibrillation.

Although transient atrial dysfunction has been reported after electrical cardioversion of atrial fibrillation (AF), the difference in the time to recover from the atrial hormonal, mechanical, and electrical dysfunction has not been described. Thus, we evaluated the time course of recovery from atrial hormonal, mechanical, and electrical dysfunction after cardioversion in patients with nonvalvular AF. We attempted electrical cardioversion in 87 consecutive patients with nonvalvular AF that had persisted for > or =6 months, and in 24 patients (28%) with maintained sinus rhythm for > or =6 months. To evaluate atrial hormonal, mechanical, and electrical dysfunction in these 24 patients, we measured plasma concentration of atrial natriuretic peptide, the atrial peak velocity in transmitral flow, and the ratio of peak systolic-to-diastolic pulmonary venous flow (S/D ratio) using echocardiography, and the duration and the root mean voltage for the terminal 20 ms (LP20) of the filtered P wave using P-wave signal-averaged electrocardiography. Atrial natriuretic peptide rapidly returned to baseline within 1 day after cardioversion, and maintained these levels for 6 months. Atrial peak velocity in transmitral flow and S/D ratio were significantly increased at 2 weeks, and continued to increase until 1 month, and then reached a plateau. The duration and LP20 began to recover only 6 months after cardioversion. One to 3 years after conversion, the duration and LP20 had nearly reached a plateau, but the latter value remained below normal. In patients with nonvalvular AF of prolonged duration, recovery from atrial electrical dysfunction after sinus conversion took much longer than that from either atrial hormonal or mechanical dysfunction.

Aged↗
PubMed1996

The major vault protein (MVP100) is contained in cholinergic nerve terminals of electric ray electric organ.

A protein of Mr 100,000 (MVP100) is highly enriched in the electromotor system of electric rays. Biochemical analysis indicates that MVP100 is contained in the cholinergic nerve terminals of Torpedo electric organ as part of a large cytosolic complex. On sucrose density gradient centrifugation MVP100 comigrates with synaptic vesicles or synaptosomes. It can be partially separated from synaptic vesicles by gel filtration or glycerol velocity gradient centrifugation. Within the complex MVP100 behaves like a hydrophobic protein and is protected against proteolytic attack. MVP100 can be immunodetected by an antibody against phosphotyrosine, and it becomes phosphorylated on incubation with [gamma-32P]ATP. By screening an electric ray electric lobe cDNA library the primary structure of MVP100 was analyzed. MVP100 is highly homologous to the major vault proteins of slime mold and rat and to the human lung resistance-related protein. Compared with non-neural tissues the expression of MVP100 is highest in brain and enriched in the electric lobe that contains the somata of the electromotor neurons. Immunoelectron microscopic analysis reveals a close association of MVP100 and synaptic vesicles in the nerve terminals of the electric organ.

Amino Acid Sequence↗
PubMed2005

Reduction of excessive electrical stimulus during electric pulp testing.

AIM: To measure excessive electrical stimulus time during pulp testing via electromyography (EMG) in the anterior belly of the digastric muscle, voice and finger movement, and to determine whether excessive stimulus time could be attenuated by a specially designed automatic circuit breaker on the basis of the EMG signal. METHODOLOGY: The signals from three human responses (EMG, finger and voice), induced by the Digitest (Parkell Inc., Farmingdale, NY, USA) electric pulp tester, were captured using a MP100 (Biopac System Inc., Goleta, CA, USA) and recorded into a personal computer. The excessive stimulus time from activation to the end of electrical stimulation was calculated for each of these three responses. The automatic circuit breaker was designed to disconnect the electrical output of the electric pulp testing (EPT) unit immediately after detecting the preset EMG level (100 mV). Each of the right central incisors and first premolars of 23 healthy individuals (16 males and seven females) was tested to see whether there was a difference in tooth type or gender. This was analysed by Wilcoxon signed rank test (nonparametric paired t-test) and Mann-Whitney test (nonparametric independent t-test), respectively. RESULTS: Amongst three human responses, the electrical onset occurred in the order of EMG, finger and voice. Excessive stimulus time was 347.8 +/- 78.3 ms when observed by the EMG, 264.9 +/- 63.9 ms when observed by finger span and 229.4 +/- 41.8 ms when observed by the voice, which were all found to be significantly different (P < 0.05). When the automatic circuit breaker was used, the excessive stimulus time was 61.0 ms, which was 286.8 ms shorter than that measured from EMG onset when using the conventional EPT. CONCLUSIONS: When the automatic circuit breaker was used, excessive stimulus time on the basis of EMG was attenuated on average by 286.8 ms.

Adult↗
PubMed1976

Electric signals and schooling behavior in a weakly electric fish, Marcusenius cyprinoides L. (Mormyriformes).

Field recordings of electric organ discharges and catches of Marcusenius cyprinoides showed that these electric fish form groups and move about in schools. The role electric organ discharges in group cohesion was investigated by comparing interactions in groups of intact and operated, electrically silent fish. The absence of electric organ dischares reduced locomotor activity and resulted in the disappearance of two behaviors: parallel lineup and single file swimming. Electric signals are considered part of a schooling mechanism that aids the fish in maintaining group cohesion in their turbid enviornment and during migration at night.

Animals↗
PubMed1996

A case cohort study of suicide in relation to exposure to electric and magnetic fields among electrical utility workers.

OBJECTIVES: This case cohort study examines whether there is an association between exposure to electric and magnetic fields and suicide in a population of 21,744 male electrical utility workers from the Canadian Province of Québec. METHODS: 49 deaths from suicide were identified between 1970 and 1988 and a subcohort was selected comprising a 1% random sample from this cohort as a basis for risk estimation. Cumulative and current exposures to electric fields, magnetic fields, and pulsed electromagnetic fields (as recorded by the POSITRON meter) were estimated for the subcohort and cases through a job exposure matrix. Two versions of each of these six indices were calculated, one based on the arithmetic mean (AM), and one on the geometric mean (GM) of field strengths. RESULTS: For cumulative exposure, rate ratios (RR) for all three fields showed mostly small non-significant increases in the medium and high exposure groups. The most increased risk was found in the medium exposure group for the GM of the electric field (RR = 2.76, 95% CI 1.15-6.62). The results did not differ after adjustment for socioeconomic state, alcohol use, marital state, and mental disorders. There was a little evidence for an association of risk with exposure immediately before the suicide. CONCLUSION: Some evidence for an association between suicide and cumulative exposure to the GM of the electric fields was found. This specific index was not initially identified as the most relevant index, but rather emerged afterwards as showing the most positive association with suicide among the 10 indices studied. Thus the evidence from this study for a causal association between exposure to electric fields and suicide is weak. Small sample size (deaths from suicide) and inability to control for all potential confounding factors were the main limitations of this study.

Cohort Studies↗
PubMed1984

The electric sense of weakly electric fish.

Recent studies of electroreception have been particularly successful in three different areas: Electroreceptors are tuned to the dominant frequency of the animal's EOD, and their tuning follows natural and experimentally induced shifts in EOD frequency. Steroid hormones influence the electric organ pacemaker frequency in the genus Sternopygus, and the tuning of electroreceptors will follow hormone-induced frequency shifts only if the receptors experience the animal's EOD. The frequency tuning of electroreceptors reveals properties similar to those of cochlear hair cells, and electroreceptors may be suitable model systems for in vitro studies of cellular and molecular aspects of electrical filter mechanisms in hair cells. In contrast to the South American or gymnotoid electric fish, the African or mormyrid electric fish evaluate electroreceptive information with the help of corollary discharges of their electric-organ pacemaker. The corollary discharge inhibits input from knollenorgan receptors so that, in the context of social communication, the animal only perceives EODs of neighbors but not its own. The corollary discharge at the same time enhances input from most mormyromasts so that the animal, in the context of electrolocation, selectively receives feedback from its own EODs. Finally, responses of ampullary electroreceptors to the animal's own EODs are centrally nulled by an elaborate and modifiable efference copy so that the animal is only informed about "nontrivial", low-frequency events in its environment. Laminated and topographically organized structures in the hindbrain and midbrain of gymnotoid fish are being studied with regard to neuroanatomical fine structure and functional organization. Different laminae and cell types in the hindbrain are specialized for the extraction of specific stimulus features, such as modulations of phase or amplitude in a sinusoidal stimulus regime. This information is passed on to the midbrain for the computation of more complex stimulus variables, such as the difference in phase modulations reported from different parts of the body surface. The torus semicircularis of the midbrain is designed for parallel processing of information from different parts of the body surface and for parallel computation of different stimulus variables for the control of behavioral responses. Electrical and visual information converge in the tectum opticum, which harbors a multimodal representation of sensory space.

Afferent Pathways↗