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PubMed1980

Electric currents, bone remodeling, and orthodontic tooth movement. I. The effect of electric currents on periodontal cyclic nucleotides.

Osteogenesis has been found to occur in response to the application of electric currents to bone. The objective of this experiment was to study the effects of D.C. electric currents on periodontal tissues in cats. Cyclic nucleotides, compounds known to be involved in cellular activation, were studied by immunohistochemistry in the involved tissues. Three groups of three young adult cats each were treated for 1, 3, and 7 days, respectively, by a device delivering 15 microamperes of direct current to bone osteoblasts and PDL cells stained intensely for cAMP and cGMP were observed adjacent to the cathode and anode, and bone apposition was found near the cathode. These results suggest that electric stimulation enhances cellular enzymatic phosphorylation activities in periodontal tissues and may be a potent tool in accelerating alveolar bone turnover.

Alveolar Process↗
PubMed2006

Circadian rhythms in electric waveform structure and rate in the electric fish Brachyhypopomus pinnicaudatus.

Weakly electric fish have long been known to express day-night oscillations in their discharge rates, and in the amplitude and duration of individual electric organ discharges (EODs). Because these oscillations are altered by social environment and neuroendocrine interactions, electric fish are excellent organisms for exploring the social and neuroendocrine regulation of circadian rhythm expression. Previous studies asserting that these oscillations are circadian rhythms have been criticized for failing to control temperature and randomize feeding regimes, or for running the fish under constant conditions for just 2-3 days. Here we show that the day-night oscillations in the EODs of the neotropical gymnotiform fish Brachyhypopomus pinnicaudatus free-run for over a week under constant photic and thermal conditions, and randomized food provisioning. Sex differences were apparent in strength and magnitude of the circadian oscillations; male oscillations were stronger and larger. All three parameters retain a common oscillation period while differing in the persistence of oscillation strength and magnitude, a difference consistent with proposals by others that declines of behavioral circadian rhythms may result from breakdowns downstream of the central oscillator.

Analysis of Variance↗
PubMed2004

Electrical therapy for post defibrillatory pulseless electrical activity.

BACKGROUND: Defibrillation may convert ventricular fibrillation (VF) only to reveal profound mechanical dysfunction. Survival following this dysfunction, known as pulseless electrical activity (PEA) and electromechanical dissociation (EMD), is uncommon. We sought to evaluate an electrical therapy for primary post shock PEA following short duration VF. METHODS AND RESULTS: Forty-eight episodes of VF, lasting 110 +/- 25 s, were induced in 16 anesthetized dogs. Following defibrillation, 35 episodes met PEA criteria (ABP < or = 36 mmHg diastolic and pulse pressure < or = 14 mmHg in the first 20 s post shock). These post defibrillation PEA episodes were either Not Treated (NT) or Treated (T) with packets of 4-20 monophasic 0.2 ms 50-100 Hz pulses of 20-60 V applied across the tip and coil of an integrated bipolar transvenous defibrillation lead positioned in the right ventricle. The therapeutic endpoint was return of spontaneous circulation (ROSC; self-sustained ABP > or = 60 mmHg diastolic and/or > or = 100 mmHg systolic) for over 2 min. In the Not Treated group, only 4 of 19 (21%) episodes spontaneously recovered to ROSC in 123 +/- 49 s while in the Treated group, 11 of 16 (69%) of the PEA episodes achieved ROSC in 102 +/- 92 s. CONCLUSIONS: Electrical therapy increased the likelihood of ROSC in primary post defibrillation PEA three-fold (P < 0.01). Recovery occurred in the absence of thoracic compression, mechanical ventilation, or adjunctive drug therapy.

Animals↗
PubMed2003

Modeling the effects of electrical conductivity of the head on the induced electric field in the brain during magnetic stimulation.

OBJECTIVE: The objective of this document is to quantify the effect of changing conductivity within the brain in transcranial magnetic stimulation. METHODS: Extreme examples of white and grey matter distributions as well as cerebral spinal fluid are analyzed with numerical boundary element methods to show that the induced E fields for these various distributions vary little from the homogeneous case. RESULTS: Models representative of the brain that demarcate regions of white matter and grey matter add an unnecessary level of complexity to the design and analysis of magnetic stimulators. The induced E field varies little between a precise model with exact placement of white and grey matter from that of its homogeneous counterpart. The E field will increase in white matter, and decrease in grey, but the variation is small. The contour integral of the E field around a closed path is dictated by the flux change through that contour. DISCUSSION: The maximum value of the variation of the electric field between a fully homogeneous medium, and one filled with different conductivity media is 1/2 the conductivity ratio of the media involved. Neuronal stimulation is more likely at the interface between dissimilar mediums, the greatest being between white matter and cerebral spinal fluid. The interface location where no normal electric field exists will witness a localized electric field 51% greater than the homogeneous E field on the white matter side of that interface. White-grey matter interfaces will have a maximum localized increase in the E field 22.9% greater than the homogeneous case. CONCLUSIONS: Variations in neural intracellular potential during a magnetic stimulation pulse will be small among patients. The most efficient modeling will follow by assuming the medium homogeneous, and noting that perturbations from this result will exist.

Brain↗
PubMed1992

Alterations in electrical pain thresholds by use of acupuncture-like transcutaneous electrical nerve stimulation in pain-free subjects.

Acupuncture-like transcutaneous electrical nerve stimulation (ALTENS) was compared with a placebo treatment in altering acute electrical pain thresholds. Ten pain-free subjects underwent, on different days, an acclimatization session, an ALTENS treatment, and a placebo treatment in a cross-over design. Electrical sensation and pain thresholds were measured from the tip of the index finger bilaterally at 15-minute intervals twice before, once during, and three times after a 30-minute treatment session. The ALTENS treatment was given at 4 Hz at an intensity just below pain threshold delivered to acupuncture points in the hand and wrist. The placebo treatment was similarly delivered, except that the intensity of stimulation was just above sensation threshold. Neither the ALTENS treatment nor the placebo treatment produced a significant change in pain threshold. There was no correlation between initial pain threshold and change in pain threshold. Implications for the modulation of pain are discussed.

Adult↗
PubMed1996

Coding of time-varying electric field amplitude modulations in a wave-type electric fish.

1. The coding of time-varying electric fields in the weakly electric fish, Eigenmannia, was investigated in a quantitative manner. The activity of single P-type electroreceptor afferents was recorded while the amplitude of an externally applied sinusoidal electric field was stochastically modulated. The amplitude modulation waveform (i.e., the stimulus) was reconstructed from the spike trains by mean square estimation. 2. From the stimulus and the reconstructions we calculated the following: 1) the signal-to-noise ratio and thus an effective temporal bandwidth of the units; 2) the coding fraction, i.e., a measure of the fraction of the time-varying stimulus encoded in single spike trains; and 3) the mutual information provided by the reconstructions about the stimulus. 3. Signal-to-noise ratios as high as 7:1 were observed and the bandwidth ranged from 0 up to 200 Hz, consistent with the limit imposed by the sampling theorem. Reducing the cutoff frequency of the stimulus increased the signal-to-noise ratio at low frequencies, indicating a nonlinearity in the receptors' response. 4. The coding fraction and the rate of mutual information transmission increased in parallel with the standard deviation (i.e., the contrast) of the stimulus as well as the mean firing rate of the units. Significant encoding occurred 20-40 Hz above the spontaneous discharge of a unit. 5. When the temporal cutoff frequency of the stimulus was increased between 80 and 400 Hz, 1) the coding fraction decreased, 2) the rate of mutual information transmission remained constant over the same frequency range, and 3) the reconstructed filter changed. This is in agreement with predictions obtained in a simplified neuronal model. 6. Our results suggest that 1) the information transmitted by single spike trains of primary electrosensory afferents to higherorder neurons in the fish brain depends on the contrast and the cutoff frequency of the stimulus as well as on the mean firing rate of the units; and 2) under optimal conditions, more than half of the information about a Gaussian stimulus that can in principle be encoded is carried in single spike trains of P-type afferents at rates up to 200 bits per second.

Action Potentials↗
PubMed1990

Magneto-electrical stimulation of central motor pathways compared with percutaneous electrical stimulation.

The central motor conduction to the relaxed muscles was studied in 30 normal volunteers using magneto-electrical stimulation (MES) of the central motor pathways. The results were compared with those obtained by the percutaneous electrical stimulation technique (PES) described previously. None of the cortical and spinal latencies (Lcor and Lsp, respectively) and the central motor conduction time were different between MES and PES in the upper limb muscles. In some lower limb muscles, however, the Lsps of MES were significantly shorter than those of PES. This was probably because the magnetic stimulation over the lumbar spinal column activated the motor roots at their exit from the spinal canal rather than the level of conus medullaris, at which activation occurs in the electrical stimulation.

Adult↗
PubMed2006

A serious and repeatable electrical hazard--compressed electrical cord and an operating table.

We describe a previously unreported hazard resulting from compression of an electrical cable by an operating theatre table. This resulted in a live wire contact to the operating table. Intermittent connection of the table to earth during a procedure resulted in triggering of a residual current device mitigating the effects of the hazard. The actual cause was not readily identified as the devices connecting the table to earth were considered most likely to be the source of the current. There was potential for significant injury to the patient and theatre staff which would have been diminished if staff had had a better understanding of the electrical safety equipment in use. We examine the underlying causes of the accident, discuss electrical safety and correct use of safety devices in the operating theatre, and propose guidelines for appropriate management.

Aged↗
PubMed2000

Calculated electric field induced in bundles of long cells in the human body when it is exposed to low-frequency electric fields.

A theoretical analysis is made of the electric field induced in the interior of long cylindrical cells arranged in bundles of parallel cells embedded in the saline fluid in the human body exposed to extremely low-frequency (ELF) and very low-frequency (VLF) electric fields parallel to the length of the cells. Such bundles characterize muscle. The analysis parallels in many respects the earlier study of isolated long cells (King and Wu, Phys. Rev. E 58, 2363-2369, 1998) but has important added complications. It leads to a similar result: The field inside the membrane of each long cell is the same as the field just outside the membrane in the saline fluid; i.e., the membrane provides no shielding. While one might expect the presence of the neighboring cells to provide a shielding effect for each cell, the results of this study show quantitatively that this is not the case. In fact, the electric field in the interior of each of a bundle of long cells is seen to increase very slightly (of the order of 0.4%) when the cells in the bundle are moved close enough to be practically in contact.

Cell Membrane↗
PubMed1990

[Physical and biophysical aspects of high energy intracardiac electrical discharges. II. Correlations between the physical and electrical effects of liminal and infraliminal shocks].

The electrical phenomena produced during the fulguration impulses are analyzed using a digital oscilloscope which enables the calculation, with precision, of the energies consumed all along the curve or between chosen times. Moreover, it enables the calculation of the corresponding impedance values and shows that the latter varies during all the discharge. The explanation for these impedance variations is obtained thanks to rapid cinematography, showing the formation of the fulguration bubble. Hence, one can observe an impedance variation which is quite distinctive from the one which would correspond to the simple passage of an electrical current in saline solution. Particularly at the end of the impulse, an important increase in the impedance corresponds to the loss of ionization of the bubble. Therefore, by simply reading these electrical parameters, it is possible to know the main stages of the fulguration phenomenon for impulses situated around the deflagration threshold.

Algorithms↗
PubMed2000

Transcutaneous electrical nerve stimulation and acupuncture-like transcutaneous electrical nerve stimulation for chronic low back pain.

BACKGROUND: Transcutaneous electrical nerve stimulation (TENS), originally based on the gate-control theory of pain, is widely used for the treatment of chronic low back pain. Despite its wide use and theoretical rationale, there appears at first glance little scientific evidence to support its use. This Cochrane review examines the available evidence on TENS for the treatment of chronic back pain through an exhaustive search of the literature. OBJECTIVES: Transcutaneous electrical nerve stimulation (TENS) and acupuncture-like transcutaneous electrical nerve stimulation (ALTENS) for chronic low back pain management have experienced a tremendous growth over the past 25 years. The objective of this review was to assess the effects of TENS and ALTENS for reducing pain and improving function in patients with chronic back pain. SEARCH STRATEGY: We searched MEDLINE up to November 1997, EMBASE from 1985 to September 1995, Amed and Ciscom to January 1995, reference lists of the retrieved articles, proceedings of conferences and contacted investigators in the field. SELECTION CRITERIA: Randomised trials comparing TENS or ALTENS therapy to placebo in patients with chronic low back pain. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted data on pain reduction, range of movement, functional and work status. MAIN RESULTS: Six trials were included. The trials included 288 participants with an average age range of 45 to 50 years and approximately equal numbers of women and men. The overall odds ratio for improvement in pain for each comparison was: TENS/ALTENS versus placebo 2.11 (95% confidence interval 1.32 to 3. 38), ALTENS versus placebo 7.22 (95% confidence interval 2.60 to 20.01) and TENS versus placebo 1.52 (95% confidence interval 0.90 to 2.58). The odds ration for improvement in range of motion on ALTENS versus placebo was 6.61 (95% confidence interval 2.36 to 18.55). REVIEWER'S CONCLUSIONS: There is evidence from the limited data available that TENS/ALTENS reduces pain and improves range of motion in chronic back pain patients, at least in the short term. A large trial of ALTENS and TENS is needed to confirm these findings.

Chronic Disease↗
PubMed1986

Species differences in electric organs of mormyrids: substrates for species-typical electric organ discharge waveforms.

The organization of electric organs is described for the mormyrid fishes from Africa. The electric organ's spike-generating cells or electrocytes are wafer-shaped cells with a special geometry that relates to the number of phases and polarity of their pulsatile electric organ discharge (EOD) waveform. Six "families" of electrocytes are recognized on the basis of cell geometry. Each family includes species with EODs of similar polarity and phase number. Despite such similarities, there are still dramatic species differences in EOD waveforms for a given family that may further depend on specialized features of the electrocyte's excitable membranes. It is each species' particular electrocyte "profile" that must underlie the development of species-specific and hormone-dependent sex differences in the EOD waveforms.

Animals↗
PubMed1994

Electric birefringence imaging of DNA in agarose electrophoresis gels: noise limits and prolonged electric field effects.

Electric birefringence imaging (EBI) maps stresses in agarose electrophoresis gels. Both DNA and gel alignment can be monitored using this technique. Previously, we have reported birefringence images associated with resolved small (< 48 kbp) and partially resolved large 48 kb-(2 Mbp) DNA fragments oriented with relatively short electric field pulses. In this paper, differences between images acquired using short and long (DC) voltage pulses are presented. It is shown that stress signals distribute over long distances when exposed to prolonged electric fields. Resolution also affects band shapes. Refinements in instrumental design and evaluation of limiting noise sources of the technique are also described.

Birefringence↗
PubMed1985

Electrical and ionic controls of tissue cell locomotion in DC electric fields.

The motility of fish epidermal cells (keratocytes) was examined in the presence and absence of DC electric fields. In fields of 0.5-15 V/cm, single epidermal cells, cell clusters, and cell sheets migrate toward the cathode. Cell clusters and sheets break apart into single migratory cells in the upper range of these field strengths. During locomotion, keratocytes extend broad lamellipodia, which contain a pervasive actomyosin network. The lamellipodial extension and locomotion of keratocytes are reversibly inhibited by a variety of calcium channel antagonists, whereas their motility is unaffected by hyperpolarizing and depolarizing (low and high K+) media. Microtubule disassembly has no effect on cell morphology, motility or the ability of the cells to be guided by a DC electric field. Using these results, the role that membrane-regulated Ca2+ influx may play in generating cytoskeletal and protrusive activity in keratocytes and other cells is discussed in some detail. Mechanisms by which an external electric field may bias transmembrane ion fluxes and thereby control cell locomotion are also examined.

Animals↗
PubMed1998

Electrical transport in a disordered medium: NMR measurement of diffusivity and electrical mobility of ionic charge carriers.

Electrical transport in porous media plays an important role in many fields of pure and applied science. The basic microscopic processes of the charge transport have attracted considerable theoretical interest for a long time. However, on a microscopic level there was up to now no experimental access to this problem. In the present paper we demonstrate, by using a suited porous system, that two combined NMR methods can offer such a first experimental access. We apply common PFG NMR methods and the special electrophoretic NMR (ENMR) technique for the measurement of self-diffusion coefficient D+ and electric mobility u+ of a cation ((C4H9)+4) in a disordered gel-like medium (Sephadex LH-20) filled with electrolyte solution. We find a, qualitatively expected, observation time-dependence of D+, but for the first time such a time-dependence is also observed for u+, which means the detection of the phenomenon of "anomalous field assisted diffusion" or "anomalous mobility." For the measurement of the short-time behavior of the mobility a new pulse sequence is presented. The time-dependent mobilities were measured at three different external electrical fields E. From the long-time behavior of D+, u+, and DH2O three independent values for the tortuosity T of the porous system could be derived. We find equality of the tortuosities T(D+) and T(u+), which represents a first experimental proof of the validity of the Einstein relation (D+ approximately u+) in a disordered medium. Finally, we discuss advantages of the possible use of "anomalous field assisted diffusion" over the commonly used "anomalous diffusion" in morphology studies by dynamic imaging in porous media.

Dextrans↗
PubMed1983

A monoclonal antibody against catalytic subunits of acetylcholinesterase in the electric organ of an electric ray, Narke japonica.

A hybridoma cell line secreting a monoclonal antibody against catalytic subunits of acetylcholinesterase in the electric organ of Narke japonica has been obtained by using a mouse immunized with the nerve terminal membranes prepared from the electric organ of Narke japonica. This monoclonal antibody (Nj-501) reacted with asymmetric, low salt-soluble and detergent-soluble forms of acetylcholinesterase of the electric organ of Narke japonica. Immunoblot analysis showed that the catalytic subunits of the asymmetric, low salt-soluble and detergent-soluble forms of acetylcholinesterase were polypeptides of molecular weight (Mr) 70K, 70K / 66K and 66K, respectively. Nj-501 markedly inhibited the activity of all these forms of acetylcholinesterase.

Acetylcholinesterase↗
PubMed2004

Effect of electric field vectoriality on electrically mediated gene delivery in mammalian cells.

Electropermeabilization is a nonviral method used to transfer genes into living cells. Up to now, the mechanism is still to be elucidated. Since cell permeabilization, a prerequired for gene transfection, is triggerred by electric field, its characteristics should depend on its vectorial properties. The present investigation addresses the effect of pulse polarity and orientation on membrane permeabilization and gene delivery by electric pulses applied to cultured mammalian cells. This has been directly observed at the single-cell level by using digitized fluorescence microscopy. While cell permeabilization is only slightly affected by reversing the polarity of the electric pulses or by changing the orientation of pulses, transfection level increases are observed. These last effects are due to an increase in the cell membrane area where DNA interacts. Fluorescently labelled plasmids only interact with the electropermeabilized side of the cell facing the cathode. The plasmid interaction with the electropermeabilized cell surface is stable and is not affected by pulses of reversed polarities. Under such conditions, DNA interacts with the two sites of the cell facing the two electrodes. When changing both the pulse polarity and their direction, DNA interacts with the whole membrane cell surface. This is associated with a huge increase in gene expression. This present study demonstrates the relationship between the DNA/membrane surface interaction and the gene transfer efficiency, and it allows to define the experimental conditions to optimize the yield of transfection of mammalian cells.

Animals↗
PubMed1992

Study of mechanisms of electric field-induced DNA transfection. III. Electric parameters and other conditions for effective transfection.

Electric parameters, osmolality, temperature, and pH of the suspending medium and the growth phase of cells, etc., are known to influence the efficiency of the pulsed electric field (PEF)-induced DNA transfection of cells. PEF-induced transfection of Escherichia coli JM105 by plasmid DNA PUC18, PUC19, PBR322, and PMSG has been used as a model system to establish quantitative relationships between these parameters and transfection efficiency. The main findings are summarized for experiments using unipolar square wave PEF. (a) For a given field strength (up to 6 kV/cm), the transfection efficiency (TE) was linearly dependent on the pulse width (up to 1 ms). (b) When field strength is fixed, Log [TE] correlated with the number of pulses applied. Similarly, when field duration was fixed, Log [TE] correlated with the number of pulses. (c) In the absence of MgCl2, TE showed a maximal value at 50 mM sucrose and was reduced by several fold at lower and higher sucrose concentrations. Cell survival was nearly constant in the range 1-300 mM sucrose. (d) E. coli in the early and mid-exponential growth phases was more susceptible to PEF for DNA transfection than it was in the stationary phase. (e) For a given set of electric parameters, TE was the highest at neutral pH and was greatly reduced at acidic and alkaline pH. (f) Increasing the temperature from 0 to 37 degrees C resulted in the reduction of TE by three orders of magnitude. This could reflect a rapid shrinking of pores at higher temperatures. (g) TE was inversely proportional to the square of the size of the plasmid DNA. By adjusting the above parameters to optimize transfection, a TE of 1010 1microg-1 DNA (PUC18) has been recorded. Further improvement in percent cell transfection may be expected by a more exhaustive search of conditions than the present study has done.

Biophysical Phenomena↗