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PubMed1999

Orientation in the dark: brain circuits involved in the perception of electric signals in mormyrid electric fish.

Weakly electric fish produce electric signals with a specialised organ in their tail. In addition, they are electrosensitive and can perceive their self-generated signals (for electrolocation) and electric signals of other electric fishes (for electrocommunication). Mormyrids possess three types of peripheral electroreceptor organs, one used for electrocommunication and two types involved in electolocation. They are innervated by afferent fibres, which project to different zones in the electrosensory lateral line lobe (ELL) in the medulla. Brain circuits for electrolocation and electrocommunication are separated almost throughout the whole brain. Electrolocation pathways run from the ELL-cortex to the torus semicircularis of the midbrain and then via the valvula cerebelli towards the telencephalon. Pathways involved in electrocommunication run from the nucleus of the ELL to another part of the torus and from there through the isthmic granule nucleus to the valvula. In addition, a pathway via the preglomerular complex to the telencephalon might exist. In both the electrolocation and the electrocommunication circuits, prominent recurrent pathways are present.

Animals↗
PubMed1986

Time domain processing of electric organ discharge waveforms by pulse-type electric fish.

We explored coastal streams, rivers, and swamps in the Guianas of South America and found eleven species of gymnotiform fishes with pulse discharges. Each species has a characteristic electric organ discharge (EOD) waveform of 0.5-5 ms duration; at least two species appear to have a natural sex difference in their EODs which is apparent when comparing large adult males and females. Three sensory coding mechanisms are proposed to explain how electric fish might be able to determine species and sex identity from such short electrical pulses. Spectral Coding: electroreceptors tuned to different frequencies encode the spectrum of the EOD as a cross-fiber stimulation pattern. Temporal Coding: EODs are encoded as a volley of nerve spikes patterned in the time domain. Scan Sampling: a receiver detects a signaler's EOD as an amplitude modulation or 'beat' set up by the combination of its own discharge with the signaler's. The receiver uses the modulation envelope to assess the signaler's EOD waveform. To distinguish between these three coding mechanisms, we tested the ability of one pulse gymnotiform, Hypopomus beebei, to discriminate one electric waveform from another by comparing the acceleration of the discharge rate to different stimuli. Stimuli are presented under two conditions: when the stimulus pulse train is free-running compared to the fish's pulse train, and when the stimulus train is phase-locked to the fish's discharge pulse train. Under the former condition scan sampling may be used; under the latter it will be impossible. Hypopomus discriminates the polarity of a single period sinusoidal stimulus under scanning conditions but does not discriminate under clamped conditions. Hypopomus gives the strongest response to single period sine waves of 670 Hz and weaker responses to sinusoids of lower and higher frequencies. Free-running and phase-locked stimuli evoke similar responses. Under free-running conditions, Hypopomus discriminates a series of EOD-like stimuli that have been phase-shifted by varying amounts, but under phase-locked conditions does not. Scan sampling is presented as a possible waveform recognition mechanism for pulse-discharging gymnotiform fishes.

Animals↗
PubMed1986

Electrical stimulation in multiple sclerosis. Comparison of transcutaneous electrical stimulation and epidural spinal cord stimulation.

Forty-nine multiple sclerosis patients with bladder symptoms and/or walking disability were subjected to a therapeutic trial with electrical spinal cord stimulation and transcutaneous electrical stimulation, a second aim being to compare these two treatments. A clear subjective improvement in bladder symptoms was achieved in the majority of the cases, and this was substantiated by objective parameters. In a proportion of cases a more moderate improvement seems to have been achieved in a variety of symptoms. Transcutaneous electrical stimulation seems to be a useful selection procedure for later electrical spinal cord stimulation.

Adult↗
PubMed1981

Microbiological implications of electric field effects. III. Stimulation of yeast protoplast fusion by electric field pulses.

Prototrophic colonies could be selected on minimal medium after mixing of protoplasts from diauxotrophic mutants of the yeasts Saccharomycopsis lipolytica and/or Lodderomyces elongisporus and treatment with polyethylene glycol (PEG) in the presence of calcium chloride. This is the result of protoplast fusion and complementation of auxotrophic deficiencies. Under identical conditions an electric field pulse in the mus-range applied via an electric discharge to the protoplast-PEG mixture resulted in a drastic enhancement of the protoplast fusion rate. The presence of polyethylene glycol was demonstrated to be a prerequisite for fusion in this case, too. The frequency of hybrid formation detected a prototrophic colonies could be increased in the case of intraspecific fusion at initial electric field strengths between 2.5 and 5 kV . cm-1. The application of an electric field pulse of proper strength and duration to a yeast protoplast suspension turned out to be a more effective tool in production of fusion products that conventional methods. Large numbers of parasexual hybrids for different selection programmes in yeast genetics and for industrial purpose may be delivered by this technique.

Electricity↗
PubMed1995

The electric lobes of the electric ray (Torpedo marmorata) are innervated by GABAergic fibres: immunocytochemical evidence for dual innervation of electromotoneurons.

It is currently thought that the electric lobes of electric rays are innervated by a single neuronal system, the oval nucleus system. In the work reported here, the innervation of the electric lobes was studied with silver staining methods, acetylcholinesterase histochemistry and gamma-aminobutyric acid (GABA) immunocytochemistry. Two types of axon were observed in the lobes: thick GABA-immunonegative fibres, which originated from the oval nucleus, and thin GABAergic fibres of unknown origin, here reported for the first time. Electromotoneurons were strongly acetylcholinesterase-positive. Non-GABAergic and non-cholinergic neurons were observed in the oval nucleus, which is innervated by GABA-immunoreactive fibres. These results suggest that GABA may modulate electric discharge both directly, by GABAergic fibres that project to the lobes, and indirectly, by GABAergic fibres that project to the oval nucleus.

Acetylcholinesterase↗
PubMed2006

In vivo electrical stimulation of rabbit retina: effect of stimulus duration and electrical field orientation.

Information that defines the depth of activation of retinal neurons is useful in considering strategies for stimulation with a retinal prosthesis, or interpreting the results from human studies that have previously been performed. The purpose of this study was to test the assertion that electrical pulse durations >0.5 msec preferentially stimulate retinal neurons deep to the ganglion cell layer. Thirteen Dutch-belted rabbits (1.2-2.0 kg) were used in this study. A Goldmann-like dome was used to deliver photic stimuli to the retina to measure the electroretinogram (ERG) and the light-induced cortical potential (VECP). Then, a micromanipulator was used to position a 500 microm inner diameter bipolar electrode near the visual streak on the epi-retinal surface. Symmetric biphasic pulses (7-1600 microA; 0.25 msec and 2.0 msec pulses per phase; biphasic pulses delivered at 2 Hz) were delivered to the retina with a current source. Extra-dural electrodes were used to record electrical evoked cortical potentials (EECPs) over the occipital cortex by performing 50 consecutive computer-averaged stimulations. The effect on the EECP of sequential epi-retinal (i.e. return electrode on epi-retinal surface) vs. trans-retinal (i.e. return electrode behind sclera) stimulation was compared. The effect upon the ERG, VECP and EECP was then assessed after 2,3,dihydroxy-6-nitro-7-sulfamoyl-benzo-f-quinoxaline (NBQX) at 112 microM concentration, d-2-amino-7-phosphonoheptanoic acid (D-AP7) at 1200 microM concentration, and l-amino-4-phosphonobutyrate (APB) at 300 microM concentration were delivered into the vitreous cavity to selectively block neuronal input to the retinal ganglion cells. Median values were reported. The amplitudes of the light-induced ERG and VECP were markedly reduced by instillation of the intra-vitreal synaptic blocking drugs. By comparison, pharmacological blockade of input to the retinal ganglion cells did not significantly alter the threshold charge or amplitude of the electrically-induced cortical responses (P>0.05). For the electrical stimuli, there was no significant difference in threshold charge for the EECP for epi-retinal vs. trans-retinal stimulation (P>0.05). The amplitude of the EECP increased linearly with increasing charge using both 0.25 msec and 2.0 msec pulses, even after synaptic blockade of input to the ganglion cells. The lack of obvious degradation of cortical amplitudes after drug instillation indicates that neurons of the middle retina are not being preferentially driven with epi-retinal stimulation, at least not with stimulus pulses up to 2.0 msec in duration. This conclusion is in contrast to prior evidence that 2.0 msec pulses would preferentially stimulate deeper retinal neurons, specifically the bipolar cells. Based upon our own observations in other studies, we believe that preferential stimulation of the middle retina in fact can be achieved by epi-retinal stimulation, by using pulse durations at least 5 times longer than those used in this study.

2-Amino-5-phosphonovalerate↗
PubMed1990

Study of mechanisms of electric field-induced DNA transfection. II. Transfection by low-amplitude, low-frequency alternating electric fields.

Electroporation for DNA transfection generally uses short intense electric pulses (direct current of kilovolts per centimeter, microseconds to milliseconds), or intense dc shifted radio-frequency oscillating fields. These methods, while remarkably effective, often cause death of certain cell populations. Previously it was shown that a completely reversible, high ionic permeation state of membranes could be induced by a low-frequency alternating electric field (ac) with a strength one-tenth, or less, of the critical breakdown voltage of the cell membrane (Teissie, J., and T. Y. Tsong. 1981. J. Physiol. (Paris). 77:1043-1053). We report the transfection of E. coli (JM105) by plasmid PUC18 DNA, which carries an ampicillin-resistance gene, using low-amplitude, low-frequency ac fields. E. coli transformants confer the ampicillin resistance and the efficiency of the transfection can be conveniently assayed by counting colonies in a selection medium containing ampicillin. For the range of ac fields employed (peak-to-peak amplitude 50-200 V/cm, frequency 0.1 Hz-1 MHz, duration 1-100 s), 100% of the E. coli survived the electric field treatment. Transfection efficiencies varied with field strength and frequency, and as high as 1 x 10(5)/micrograms DNA was obtained with a 200 V/cm square wave, 1 Hz ac field, 30 s exposure time, when the DNA/cell ratio was 50-75. Control samples gave a background transfection of much less than 10/micrograms DNA. With a square wave ac field, the transfection efficiency showed a frequency window: the optimal frequency was 1 Hz with a 200 V/cm field, and was approximately 0.1 Hz with a 50 V/cm field. Transfection efficiency varied with the waveform: square wave > sine wave > triangle wave. If the DNA was added after the ac field was turned off, transfection efficiency was reduced to the background level within 1 min. The field intensity used in this study was low and insufficient to cause electric breakdown of cell membranes. Thus, DNA transfection was not caused by electroporation of the cell membranes. Other possible mechanisms will be considered.

Biological Transport, Active↗
PubMed1999

Effects of electrical stimulation of the tentacular digits of a slug upon the frequency of electrical oscillations in the procerebral lobe.

To find the primary mechanism for the frequency changes of electrical oscillations in the procerebral (PC) lobe of a slug, we electrically stimulated the tip, middle and basal regions of the digits of the superior and inferior tentacles and recorded the local field potentials from the PC lobe. Stimuli to the middle and basal regions of the digits of the inferior tentacle significantly decreased the frequency of electrical oscillations in the PC lobe, whereas those to the tip regions of the digits of the inferior tentacle and all regions of the digits of the superior tentacle increased it. These findings suggest that the change in the frequency of electrical oscillations in the PC lobe depends on the excited region in the digits, providing the first presentation of the physiological difference in the olfactory function between the superior and inferior tentacles.

Animals↗
PubMed1997

Molecular cloning of synaphins/complexins, cytosolic proteins involved in transmitter release, in the electric organ of an electric ray (Narke japonica).

Synaphins/complexins are cytosolic proteins associated with the docking/fusion complex crucial to transmitter release. The electric organ of the electric ray Narke japonica contained at least two kinds of synaphins as revealed by immunoblotting. cDNAs for three synaphins were cloned from a cDNA library prepared from the electric lobe where cell bodies of electromotor nerves innervating the electric organ exist. The proteins encoded by these cDNAs were named Nj-synaphins 1a, 1b and 2 on the basis of their high homologies (83-93%) to mammalian synaphins 1 and 2. Nj-Synaphins were immunoprecipitated by an anti-syntaxin monoclonal antibody, together with syntaxin, SNAP-25 and VAMP (synaptobrevin), suggesting the presence of a docking/fusion complex similar to that in the mammalian brain.

Adaptor Proteins, Vesicular Transport↗
PubMed1988

Electric shock-mediated transfection of cells. Characterization and optimization of electrical parameters.

The effect of various parameters on the electric shock-mediated permeabilization and transfection of CHO cells has been investigated. Up to 70% of the cells can be maintained transiently permeable to erythrosin B for periods of at least 1 h at 20 degrees C. Electrical conditions optimal for transient permeabilization were also optimal for efficient DNA transfection by pSV2neo. However, the DNA must be present during exposure to the electric field for efficient transformation. The same requirement existed for voltage-induced DNA toxicity. The results suggest that DNA moves into the cells by electrophoresis, not by simple diffusion. Based on these observations a simple, rapid procedure for optimizing the conditions for electric shock-mediated DNA transfer into cells has been developed.

Animals↗
PubMed1998

cDNA isolation of Alzheimer's amyloid precursor protein from cholinergic nerve terminals of the electric organ of the electric ray.

Alzheimer's amyloid precursor protein (APP) is a transmembrane protein containing three phosphorylation sites in its cytoplasmic domain. In the present study, we isolated cDNA of APP from electric ray electric lobe (elAPP). This APP (elAPP699) consists of 699 amino acids, contains the beta-amyloid domain and has 80.7% similarity with the human APP695 isoform. The cytoplasmic domain, including three phosphorylation sites, was completely conserved. In the nerve terminals of the cholinergic neuron from the electric ray electric organ, we found elAPP699 existed exclusively in the mature form. We found the phosphorylated form of mature elAPP699 in the nerve terminal as well as in cell body. Immature elAPP699 was not subject to phosphorylation. Our findings indicate that, in neurons, the phosphorylation of APP occurs after maturation.

Amino Acid Sequence↗
PubMed1999

The effects of antemortem electrical stunning and postmortem electrical stimulation on biochemical and textural properties of broiler breast meat.

Experiments were conducted to determine the combined effects of antemortem electrical stunning (STUN) and postmortem electrical stimulation (STIM) on breast muscle rigor development and meat quality attributes. Birds were either unstunned, stunned with low voltage (LV), or stunned with high current (HC) prior to conventional killing. Immediately after exsanguination, birds were either unstimulated, or were subjected to electrical stimulation with 12 1s on/1s off pulses of 440 V AC and allowed to bleed for 90 s to determine the effect of treatment on blood loss. Breast fillets (Pectoralis major) were removed from carcasses immediately after evisceration (0.25 h) or after aging in a static ice-water slush for 1 or 2 h, and analyzed for muscle pH, R-value (ratio of inosine to adenosine nucleotides), and sarcomere length. Raw breast meat color (CIELAB), cook loss, and shear values were determined on samples held at 2 C for 24 h. Results showed both STUN and STIM significantly affected blood loss, pH, R-value, sarcomere length, color, and shear, and there were significant STUN by STIM interactions. Blood loss was significantly lower for the HC STUN and all the STIM treatments. STIM at 440 V resulted in accelerated rigor development as measured by pH, R-value, and sarcomere length, similar to the unstunned or LV STUN samples, but different from the HC STUN birds. These results indicate that electrical stimulation may accelerate rigor most effectively following high current stunning, which tends to delay early rigor development.

Animals↗
PubMed2006

Impedance analysis of cultured cells: a mean-field electrical response model for electric cell-substrate impedance sensing technique.

In this paper we present a model to describe the electrical properties of a confluent cell monolayer cultured on gold microelectrodes to be used with electric cell-substrate impedance sensing technique. This model was developed from microscopic considerations (distributed effects), and by assuming that the monolayer is an element with mean electrical characteristics (specific lumped parameters). No assumptions were made about cell morphology. The model has only three adjustable parameters. This model and other models currently used for data analysis are compared with data we obtained from electrical measurements of confluent monolayers of Madin-Darby Canine Kidney cells. One important parameter is the cell-substrate height and we found that estimates of this magnitude strongly differ depending on the model used for the analysis. We analyze the origin of the discrepancies, concluding that the estimates from the different models can be considered as limits for the true value of the cell-substrate height.

Animals↗
PubMed2004

Control strategies for integration of electric motor assist and functional electrical stimulation in paraplegic cycling: utility for exercise testing and mobile cycling.

AIM: The aim of this study was to investigate feedback control strategies for integration of electric motor assist and functional electrical stimulation (FES) for paraplegic cycling, with particular focus on development of a testbed for exercise testing in FES cycling, in which both cycling cadence and workrate are simultaneously well controlled and contemporary physiological measures of exercise performance derived. A second aim was to investigate the possible benefits of the approach for mobile, recreational cycling. METHODS: A recumbent tricycle with an auxiliary electric motor is used, which is adapted for paraplegic users, and instrumented for stimulation control. We propose a novel integrated control strategy which simultaneously provides feedback control of leg power output (via automatic adjustment of stimulation intensity) and cycling cadence (via electric motor control). Both loops are designed using system identification and analytical (model-based) feedback design methods. Ventilatory and pulmonary gas exchange response profiles are derived using a portable system for real-time breath-by-breath acquisition. RESULTS: We provide indicative results from one paraplegic subject in which a series of feedback-control tests illustrate accurate control of cycling cadence, leg power control, and external disturbance rejection. We also provide physiological response profiles from a submaximal exercise step test and a maximal incremental exercise test, as facilitated by the control strategy. CONCLUSION: The integrated control strategy is effective in facilitating exercise testing under conditions of well-controlled cadence and power output. Our control approach significantly extends the achievable workrate range and enhances exercise-test sensitivity for FES cycling, thus allowing a more stringent characterization of physiological response profiles and estimation of key parameters of aerobic function. We further conclude that the control approach can significantly improve the overall performance of mobile recreational cycling.

Algorithms↗
PubMed1985

Detergent-soluble form of acetylcholinesterase in the electric organ of electric rays. Its isolation, characterization and monoclonal antibodies.

The detergent-soluble form of acetylcholinesterase was purified from the electric organ of the electric rays Narke japonica and Torpedo californica, and its properties were examined. The electric organ of N. japonica and T. californica contains three types of acetylcholinesterase: low-salt-soluble, asymmetric or tailed, and detergent-soluble forms. Results showed that in N. japonica, asymmetric forms were predominant, whereas in T. californica the detergent-soluble form was predominant. Low-salt-soluble acetylcholinesterase constituted 10% of the total acetylcholinesterase in both species. Detergent-soluble acetylcholinesterase was purified by immunoaffinity chromatography with a monoclonal antibody (Nj-601) to acetylcholinesterase. Triton X-100 extracts of these electric organs were applied to a column of Nj-601-Sepharose, and the bound acetylcholinesterase was eluted quantitatively by lowering the pH to 2.8. This simple procedure gave good yields. The purified enzymes gave single peaks at 6 S on sucrose gradients in the presence of detergent and polydisperse aggregates in the absence of detergent. Reduction of disulfide bonds gave peaks at 4.4 S. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the purified acetylcholinesterases gave bands with Mr of about 130 000 in the unreduced state and with Mr of 66 000 in addition to a very faint band of Mr 130 000 in the reduced state. The Mr-66 000 polypeptides were labeled with diisopropylfluorophosphate. Thus, the detergent-soluble acetylcholinesterases exist as dimers of the Mr-66 000 components. Two-dimensional electrophoresis of the purified enzymes indicated their homogeneity. The isoelectric points of both enzymes were 5.1 under the conditions employed. The two enzymes had very similar amino acid compositions, and contained more than 14% of neutral sugars and glucosamine. Monoclonal antibodies were raised to detergent-soluble acetylcholinesterase by the hybridoma technique; eight were obtained. All of them recognized the catalytic subunits of detergent-soluble and asymmetric acetylcholinesterase, and reacted only with detergent-soluble acetylcholinesterase in immunoblots. Four of the monoclonal antibodies inhibited the activities of both the detergent-soluble and asymmetric forms of acetylcholinesterase.

Acetylcholinesterase↗
PubMed2004

An anatomical study of an electric organ and its nerve supply in the electric ray (Torpedinidae Narke japonica).

Despite anatomist's great interest in the electric organ (EO) of the electric ray, its detailed morphology remains unclear. In order to understand more completely the architecture of the EO and the branchial organ, it is necessary to examine detailed relationships regarding the origin, course and distribution of nerves innervating the EO. We thus carried out a macroscopic and microscopic anatomical study, focusing on issues, using the 18 sides of nine electric rays. The following results were obtained: (i) the EO was innervated exclusively by the facial, glossopharyngeal and vagus nerves; (ii) although these three cranial nerves consistently innervated the EO, variation in the number of the nerves innervating the EO was observed; (iii) cranial nerves innervated the EO in a segmental manner, at both entry and in the area of distribution. These results suggest that the EO of the electric ray might have differentiated from a non-constant branchial muscle anlage but preserves the branchial segments in terms of the craniocaudal, dorsoventral and proximodistal axes.

Animals↗
PubMedDate not supplied

Influence of high steady magnetic fields on the electrical activity of the electric fish Apteronotus.

We have investigated the influence of strong dc. magnetic fields--ranging up to 10 Tesla--on the weak sinusoidal electric signals which the electro-fish Apteronotus is known to emit. We made the following observations: 1. The amplitude of the sinusoidal electric signals rises with the application of the dc. magnetic fields, increasing by about 8% in a field of 10 Tesla. 2. The frequency of the signals of about 570 Hz was not at all affected by the field but remained constant in fields up to 10 Tesla. Since the electric signals of Apteronotus are of neural origin our experiments indicate an influence of strong dc. magnetic fields on the nervous system of this electric fish.

Animals↗
PubMedDate not supplied

Electrically evoked compound action potential (ECAP) of the cochlear nerve in response to pulsatile electrical stimulation of the cochlea in the rat: effects of stimulation at high rates.

Some cochlear implant patients achieve better speech recognition with pulsatile electrical stimulation presented at high rates. The present study aimed to explore, in an animal model of cochlear implants, how the excitability of the cochlear nerve is affected by pulsatile electrical stimulation delivered at high rates, of up to 1,000-2,000 pulses per second (pps). Adult rats (n=23) were implanted with two or three stimulating electrodes in the left cochlea. In four of these rats, the left cochlea was deafened by local perfusion with 1 per cent or 4 per cent neomycin solutions prior to implantation. Pulsatile stimuli consisted of 20 micros electrical pulses, delivered in trains of 200 ms duration, separated by a pause of 200 ms. The pulse rates ranged from 100 to 2,000 pps (intra-train pulse rate). Electrically evoked compound action potentials (ECAPs) of the cochlear nerve were recorded either intracochlearly or from epidural electrodes (extra-cochlearly). With increasing pulse rates, the average ECAP amplitude decreased, whereas the average ECAP latency and its variability (SD) increased. For rates above 300 pps, the amplitude of the ECAP to the individual successive pulses delivered in the train progressively decreased during the initial part of the train, corresponding to a short-term adaptation of the cochlear nerve. This effect progressively increased for pulse rates ranging from 300 to 2,000 pps. In addition, there was a phenomenon of long-term adaptation, as indicated by a decrease in the amplitude of the ECAP to the first pulse of the train, indicating that the pause of 200 ms between each train was not long enough for full recovery of the cochlear nerve. This long-term adaptation was progressively more pronounced for increasing pulse rates. To characterize further the recovery in excitability of the cochlear nerve, forward masking experiments were conducted, showing a decrease of the ECAP amplitude when the interval between the first pulse (masker) and the second pulse (probe) was shorter than 2 ms. This ECAP decrease was slow for intervals between 2 and 1 ms and then abrupt for shorter intervals. The observations described above were similar for extra- and intra-cochlear recordings and were little, if at all, affected by treatment of the cochlea with neomycin.

Animals↗