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At least 289 records · Page 16Linked to original sources
PubMed1991

[Informative value of programmed electric stimulation of the ventricles, 24-hour ECG monitoring and bicycle ergometry in the diagnosis of electric instability of the myocardium in various clinical variants of stenocardia].

The informative value of programmed ventricular pacing (PVP), Holter monitoring (HM), and bicycle ergometry (BEM) in the diagnosis of myocardial electric instability was assessed in various clinical types of angina pectoris. An examination was made of 20 patients with first exercise-induced angina (FEIA), 33 with progressive exercise-induced angina (PEIA), 17 with spontaneous angina (SA), 30 with stable exercise-induced angina (SEIA), and postinfarction angina. Myocardial electric instability was estimated from HM and BEM findings in patients with FEIA, SA, as well as in PEIA, SEIA in the presence of preserved myocardial contractility as evidenced by ventriculography. A clear-cut correlation was found between transient myocardial ischemia and the occurrence of high-grade ventricular arrhythmias for the patients from the above-mentioned groups. Lower myocardial contractility despite the nature of angina is an indication for PVP.

Adult↗
PubMedDate not supplied

[Spatial organization of the electrical potentials of the brain in the rabbit during low-frequency electric stimulation of subcortical structures].

The influence of low-frequency (2-9 Hz) electric stimulation of some limbic system structures (mammillary bodies (MB), field CA1 of the dorsal hippocampus, subiculum), thalamus midline nuclei on spectral-correlative characteristics of potentials of the neocortex and some subcortical formations and elaboration of the defensive conditioned reflex (CR) was studied in 19 rabbits. Electric stimulation of all studied formations with the current of 0.1 mA and 2-4 Hz frequency contributed to the appearance of delta-rhythm in the neocortex, especially highly expressed when MB was stimulated at the beginning of CR elaboration. The appearance of delta-rhythm in the neocortex and other examined structures impeded CR elaboration; during MB stimulation with a frequency of 2-4 Hz, CR could not be elaborated. The most favourable conditions for maintaining the theta-rhythm and CR elaboration were established when each of the examined structures was stimulated with frequency of 7 Hz, but CR elaboration was not accelerated.

Animals↗
PubMedDate not supplied

[Dependence of the shape of variable electric potential on plant constant electric field].

It is known that tissues, organs and organisms are characterized by electric polarity. There are many hypotheses as to their origin and the role of polarity in vital activity. However the final solution of these problems was not found. We have shown that the potential difference (DEP) measured along the plant surface (extracellular potentials) is directly related to the membrane potential difference across the cells of symplast. The mechanism of the propagation of variable potential similar to the mechanism of the propagated action potential in the excitable tissue was considered earlier. The data concerning the influence of the constant electric field of the plant on the shape and amplitude of the variable potential are presented.

Membrane Potentials↗
PubMed1989

Laboratory investigations of the electrical characteristics of honey bees and their exposure to intense electric fields.

Bees exposed to 60-Hz electric (E) fields greater than 150 kV/m show field-induced vibrations of wings, antennae, and body hairs. They also show altered behavior if exposed while in contact with a conductive substrate. Measurements indicate that approximately 240 nA is coupled to a bee standing on a conductive substrate in a 100-kV/m E field. In lab experiments, bee disturbance and sting result from exposure to E field greater than 200 kV/m (bee current greater than 480 nA) and reduced voluntary movements at greater than 300 kV/m (greater than 720 nA bee current) only if the bee is on a conductive substrate. It is hypothesized that in the latter situation coupled bee current drains through the lower thorax and legs to the conductive substrate, and that the resulting enhanced current density in these regions is the cause of observed responses. The observation that bees exposed to intense E fields on an insulator show vibration of body parts but no behavioral response suggests that vibration contributes little to the disturbance of bees in intense E fields. Lab measurements of bee impedance from front-to-rear leg pairs were made on wet and dry conductors. Measurements validate the selection of 1 M omega as a middle value for bee impedance used in the design of devices used to generate step-potential-induced currents in bees.

Animals↗
PubMed1994

Temperature changes associated with excitation of the electric organ in the African electric catfish.

By using heat-sensors made from synthetic pyroelectric film, it was shown that excitation of the Malapterurus electric organ brings about first a rapid rise, then a slow fall and finally a very slow rise in the temperature of the organ. Difficulties encountered in determining these rapid temperature changes by the method of employing thermistor probes are pointed out.

Action Potentials↗
PubMed1991

Electric organ discharge frequency and plasma sex steroid levels during gonadal recrudescence in a natural population of the weakly electric fish Sternopygus macrurus.

1. Sternopygus macrurus were collected in Venezuela during the period of gonadal recrudescence in early or late dry season. Electric organ discharge (EOD) frequencies were recorded, blood samples were taken for analysis of steroid titers, and gonads were taken for determination of reproductive condition. 2. Mean EOD frequencies were significantly lower in males than in females in all samples. EOD frequency was inversely correlated with body length in males in late, but not early, dry season, and these parameters were never correlated in females. 3. Plasma levels of testosterone (T) and 11-ketotestosterone (11-KT), but not estradiol-17 beta (E2), were inversely correlated with EOD frequency in males. No 11-KT was observed in plasma of females, and plasma levels of T and E2 in females were comparable to those of males. Neither T nor E2 were correlated with EOD frequency in females. 4. Testes collected in late dry season were more mature than those from early dry season; androgen levels and EOD frequency were correlated with testicular maturity. Ovaries collected in early dry season were immature, while those from late dry season were more mature. There was no relationship between EOD frequency and stage of ovarian development. 5. These results suggest that plasma androgens modulate EOD frequency in males during the reproductive season and that plasma E2 has little relationship to EOD frequency in either sex.

Animals↗
PubMed1975

[Functional features of the electroreceptors of several electric and non-electric fish].

The effect of the electric, magnetic, and mechanical stimulation of the electroreceptors was studied in marine skates (Trigon pastinaca, Raja clavata, and Torpedo marmorata) by recording single nerve fiber responses. The following two types of backbround dischanges were found with regular activity and bursting. In some fibres the bursts of impulses appeared simultaneously with respiration while in the others the activity was suppressed. The current threshold of the clear-cut responses were equal to 10- minus 9--10- minus 11 A/mm-2. The activity of the electroredeptors was modified by introducing a conductive or nonconductive object into the water. High sensistivity of the electroreceptors to weak magnetic field was shown. The biological role of the electroreceptors is discussed.

Animals↗
PubMed1989

Patterns of electric organ discharge activity in the weakly electric fish Brienomyrus niger L. (Mormyridae).

In this study we investigated the electric organ discharge (EOD) activity of the mormyrid fish Brienomyrus niger when they were not affected by conspecific EODs. The fish emitted two types of EOD patterns: phasic and tonic sequences of pulse intervals (SPIs). The phasic SPI occurred in the form of stereotyped, individual-specific bursts in EOD activity which we called scallop. Tonic SPIs varied in mean EOD repetition rate and pulse interval stability, and consisted of either regular activity with mean frequencies exceeding 10 Hz and a coefficient of variation (cv) below 15%, or variable activity with mean rates below 10 Hz and cv's of 15% and above. Individual fish predominantly generated one of the three patterns: "variable", "regular", or "scallop". Most fish emitted "variable" activity, but "regular" activity was typical of females and "scallop" of males. We suggest that these SPIs may facilitate individual recognition. The dynamics of the electromotor command system, as reflected by the fish's EOD activity, is compared with that of the well-studied mammalian inferior olive, and mechanisms for a possible self-regulatory central pattern generator are discussed.

Animals↗
PubMed1988

Transcutaneous electrical nerve stimulation after thoracotomy. Pain relief and peak expiratory flow rate--a trial of transcutaneous electrical nerve stimulation.

Forty patients scheduled to undergo thoracotomy were randomly allocated to receive either transcutaneous electrical nerve stimulation with intramuscular papaveretum (20 patients) or intramuscular papaveretum alone (20 patients) for postoperative pain relief. Total intramuscular analgesic requirements in the first 24 hours, time to satisfactory transfer to oral analgesia, antiemetic requirements and length of stay in hospital postoperatively were noted. Peak expiratory flow rate was compared pre- and postoperatively in the two groups. Use of nerve stimulation did not significantly alter the requirements for analgesia although there was a reduction in postoperative nausea and vomiting in the nerve stimulation group. There was no difference between the two groups with respect to changes in peak expiratory flow rate.

Clinical Trials as Topic↗
PubMed1987

Electric organ discharge rhythms and social interactions in a weakly electric fish, Rhamphichthys rostratus, (Rhamphichthyidae, Gymnotiformes) in an aquarium.

Pairs of fish of the South American "pulse" species (of 40-100 Hz frequency), Rhamphichthys rostratus, were studied for position and motor behaviour in tanks fitted with hollow tiles on the bottom. Each pair consisted of a larger and a smaller fish. The larger fish in each pair seemed to be territorially dominant and tended to stay inside the tiles more than the smaller one; the smaller fish moved around more than the larger one. All animals stayed more frequently inside the tiles during the daytime period. During rainy weather, or when each fish was studied separately rather than in pairs, the animals stayed more frequently inside the tiles, usually resting for long periods of time. The larger fish in each pair spent more time on its side than the smaller one, showing a diurnal rhythm in the amount of time spent in this position, whereas no such rhythm was observed for the smaller fish. The acceleration of the frequency of electric organ discharges (EOD), called "jump", and social interaction were also recorded. Smaller fish showed more jump activity than larger ones. The occurrence of jumps was related to the anti-parallel and tandem position of the two fish, seemed to increase with time of settled position and favourable temperature, was more likely to occur when the individuals were quite close to each other and to decrease during rainy weather.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Urinary bladder control by electrical stimulation: review of electrical stimulation techniques in spinal cord injury.

Evacuation of urine in paraplegics without the need for catheters would be possible when voiding could be induced by eliciting a bladder contraction. A challenging option to obtain detrusor contraction is electrical stimulation of the detrusor muscle or its motor nerves. This article reviews the 4 possible stimulation sites where stimulation would result in a detrusor contraction: the bladder wall, the pelvic nerves, the sacral roots, and the spinal cord. With respect to electrode application, sacral root stimulation is most attractive. However, in general, sacral root stimulation results in simultaneous activation of both the detrusor muscle and the urethral sphincter, leading to little or no voiding. Several methods are available to overcome the stimulation-induced detrusor-sphincter dyssynergia and allow urine evacuation. These methods, including poststimulus voiding, fatiguing of the sphincter, blocking pudendal nerve transmission, and selective stimulation techniques that allow selective detrusor activation by sacral root stimulation, are reviewed in this paper.

Electric Stimulation↗
PubMed1988

Exposure scheme separates effects of electric shock and electric field for honey bees, Apis mellifera L.

Mechanisms to explain disturbance of honey bee colonies under a 765-kV, 60-Hz transmission line [electric (E) field = 7 kV/m] fall into two categories: direct bee perception of enhanced in-hive E fields, and perception of shock from induced currents. The same adverse biological effects previously observed in honey bee colonies exposed under a 765-kV transmission line can be reproduced by exposing worker bees to shock or E field within elongated hive entranceways (= tunnels). Exposure to intense E field caused disturbance only if bees were in contact with a conductive substrate. E-field and shock exposure can be separated and precisely defined within tunnels, eliminating dosimetric vagaries that occur when entire hives are exposed to E field.

Animals↗
PubMed1976

Electric organ discharges of the weakly electric fish Gymnarchus niloticus (Mormyriformes) in its natural habitat.

Electric organ discharges (EODs) of Gymnarchus niloticus in its natural habitat (Chari River, Chad Basin) and accompanying ecological data (pH, conductivity, temperature, turbidity, O2 dissolved) were recorded. The EOD frequencies ranged from 204 to 313 Hz (day) and 196-326 Hz (night). In social swimming the range of interfish EOD frequency differences was from 4 to 82 Hz. The EOD frequency seems to decrease with the age of the fish.

Age Factors↗
PubMedDate not supplied

Is the electrical activity of the brain always electrical? (The factors forming the potential of the metallic electrode during its direct contact with the brain).

This article is devoted to an analysis of the factors forming slow changes in the potential of a metallic electrode coming into direct contact with living tissue. Data are presented in this paper according to which, the electrochemical activity of the tissue also participates, in addition to electrical activity, in the formation of the electrode potential. The article is in the nature of a discussion.

Amplifiers, Electronic↗
PubMed1993

Action and binding of omega-conotoxin on the putative calcium channel of synaptosomal plasma membrane from electric organ of Japanese electric ray, Narke japonica.

Actions of omega-conotoxin GVIA on synaptosomes isolated from a Japanese electric ray, Narke japonica, were investigated. omega-Conotoxin inhibited, in a dose-dependent manner, both increases in free calcium concentration in, and acetylcholine release from synaptosomes depolarized with a high concentration of potassium ions. The concentrations of omega-conotoxin required for half-maximal inhibition (IC50) of increase in intrasynaptosomal Ca and acetylcholine release were 8 and 7 microM, respectively. Assay using radioiodinated toxin derivative revealed a specific binding site with a dissociation constant (KD) of 2.8 microM and a density (Bmax) of 45 pmol/mg protein of synaptosome. Binding assay with synaptosomal plasma membrane showed a KD = 7 microM and a Bmax = 200 pmol/mg protein. Autoradiography with sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis after covalent cross-linking of the toxin, using disuccinimidyl suberate, revealed the 170,000 mol. wt peptide to be an omega-conotoxin receptor. The present study has directly and clearly shown that omega-conotoxin inhibits acetylcholine release by blocking Ca influx into nerve terminals. The 170,000 mol. wt peptide identified as a receptor of the toxin exists in high density in the plasma membrane of the presynaptic nerve terminal and is likely to be a component of a voltage-dependent Ca channel responsible for the neurotransmitter release.

Acetylcholine↗
PubMed1988

Electrical stimulation of cochlear efferents at the round window reduces auditory desensitization in guinea pigs. I. Dependence on electrical stimulation parameters.

Electrical stimulation at the round window with pulsed short trains has been shown to elicit classical efferent effects on N1 amplitudes at the cochlea. This report demonstrates that round window stimulation as a continuous burst can reduce temporary threshold shifts (TTS) caused by a simultaneous monaural loud sound exposure. This result is similar to recent reports that stimulation of the crossed olivocochlear bundle (COCB) at the floor of the fourth ventricle can reduce TTS. Like COCB stimulation at the brainstem, the effect of round window stimulation could be abolished by strychnine, with a time course paralleling the blocking action of strychnine on the traditional COCB effects of pulsed short trains on N1 amplitudes. This report also established parameters for optimal effects of the round window stimulus and found them to be similar to the optimal parameters for the effects of brainstem stimulation on TTS. Tonic effects on TTS were also observed, with reductions in TTS being obtained as much as 7 min after a 1 min-long round window stimulus. Such tonic effects did not appear to be due to persistent effects at the cochlea but were suggested to be due to a long term resetting of some central site activated by antidromic stimulation from the round window.

Animals↗
PubMed1994

Effects of electrical biasing on electrically-evoked otoacoustic emissions.

Electrically-evoked otoacoustic emissions were produced using a 10 microA, 750 Hz AC current plus a biasing DC current in the range of +/- 10 microA. Concurrently, a 1643 Hz tonal stimulation was delivered to the eardrum. At low sound levels, negative DC current increased the emission while positive DC current reduced the emission. Such findings are reasonably explained by a negative-feedback model of cochlear function. At high sound levels, negative DC current reduces the emission, while positive current has little effect. These data can be accounted for by voltage-dependent length changes shown to occur in isolated outer hair cells, with the additional requirement that voltage-dependent K+ channels in outer hair cells reduce the effectiveness of positive DC current in changing membrane potential.

Acoustic Stimulation↗
PubMed2006

Behavioral effects of high frequency electrical stimulation of the hippocampus on electrical kindling in rats.

Experiments were designed to evaluate the effects of high frequency electrical stimulation (HFS) applied in ventral hippocampus during the hippocampal kindling process, as well as on the expression of fully kindled seizures and the refractoriness for subsequent convulsions during their postictal period. Male Wistar rats, stereotactically implanted in both ventral hippocampus, received daily bilateral HFS (pulses of 60 micros width at 130 Hz at subthreshold current intensity) during 1h immediately after each kindling stimulation (1s train of 60 Hz biphasic square waves, each 1 ms) during 40 days or until the kindled state was achieved. Rats were classified as follows: (a) Responder animals, who required low current intensity for HFS (208+/-38.2 microA), did not show progress of the kindling process and remained in stages II and III seizures. (b) Nonresponders rats, in which the current intensity for HFS was higher (434.5+/-51.7 microA), developed the kindling process as the kindling control group. When HFS was applied before the kindling stimulation in fully kindled rats, animals presented a reduced expression of the fully kindled seizures (nonresponders animals) and an enhanced refractoriness for subsequent seizures during the postictal period (kindling control and nonresponder animals). There was no correlation between the area where the HFS was applied and the effects induced. It was concluded that HFS at 130 Hz in ventral hippocampus is able to modify the epileptogenesis induced by the hippocampal kindling process and the refractoriness to subsequent seizures during the postictal period in rats.

Animals↗