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PubMed1986

Electrical basis of excitation and inhibition of human colonic smooth muscle.

Excitation and inhibition of electrical activities of the musculature of the human colon and the consequent changes in motor activities were studied in vitro. The mechanisms of excitation and inhibition were very different from those of the small intestine and colons from animal models. Carbachol increased spiking activity and the frequency of bursts of electrical oscillations in longitudinal muscle. Each longitudinal muscle contraction was related to a burst of electrical oscillations. Carbachol induced one of three patterns of activity in circular muscle: (a) continuous electrical oscillatory activity (14-24 cpm) with spikes, associated with tonic contraction; (b) bursts of such electrical activity, associated with broad phasic contractions; or (c) prolonged membrane potential depolarizations (frequency 1-3 cpm) with superimposed intense spiking activity, associated with phasic contractions. Isoproterenol inhibited all electrical and mechanical activities in both muscle layers. These results may provide a better understanding of (a) the origins of the variable patterns of electrical and motor activities and (b) the relationship between electrical and mechanical activities of the human colon musculature.

Action Potentials↗
PubMed1993

A critical review of the genotoxic potential of electric and magnetic fields.

55 published articles were identified which reported results of tests of ELF (extremely low frequency) or static electric or magnetic fields for genotoxic effects. The biological assays used spanned a wide range, including microbial systems, plants, Drosophila, mammalian and human cells in vitro and in vivo. Experimental results were grouped into four exposure categories: ELF Electric; ELF Magnetic; Static Electric; and Static Magnetic. The internal electric fields present in media (for in vitro experiments) and in the torso and extremities (for in vivo experiments) were estimated, providing an index of comparison. All experiments were critically analyzed with respect to basic data quality criteria. Experiments within each exposure category were then compared to determine if results reinforced or contradicted one another. The preponderance of evidence suggests that neither ELF nor static electric or magnetic fields have a clearly demonstrated potential to cause genotoxic effects. However, there may be genotoxic activity from exposure under conditions where phenomena auxiliary to an electric field, such as spark discharges, electrical shocks, or corona can occur. In addition, two unconfirmed reports suggest the genotoxic potential of certain chemical mutagens or ionizing radiation may be affected by co-exposure to electric or magnetic fields. Certain exposure categories are not represented or are under-represented by tests in some genotoxicity test systems that are usually included in minimal test batteries as specified by EPA for chemicals. It is suggested that consideration be given to whether additional genotoxicity testing is warranted to fill these gaps.

Animals↗
PubMed1991

Effect of high-volume cardioplegia on small-amplitude electrical activity during cardioplegia arrest.

UNLABELLED: The effects of high-volume cardioplegia on the presence of small-amplitude electrical activity during cardioplegia arrest were investigated in 19 mongrel dogs. The animals were randomly assigned to receive either high-volume crystalloid cardioplegia (HV-plege) or crystalloid cardioplegia guided by continuous electrical monitoring (V-plege). Cardiac index, left ventricular stroke work index dp/dt, and myocardial oxygen consumption were measured before bypass and following 90 min ischemia and 45 min reperfusion. Biopsies were taken for measurement of adenosine triphosphate (ATP) and examination of myocardial ultrastructure. Nine animals received HV-plege, while the remaining 10 animals received cardioplegia guided by voltage criteria. Small-amplitude electrical potentials were recorded within 10-15 min after the infusion of cardioplegia in all animals receiving cardioplegia guided by voltage criteria. Electrical activity, however, was immediately abolished by reinfusion of cardioplegia. HV-plege reduced the incidence of small-amplitude electrical activity during cardioplegia arrest but did not prevent electrical activity. Left ventricular function and myocardial ultrastructure were better preserved when cardioplegia was guided by electrical monitoring. ATP decreased similarly in both groups following cardioplegic arrest, but myocardial oxygen consumption was significantly higher following the arrest in the V-plege group. CONCLUSIONS: HV-plege does not prevent small-amplitude electrical activity and may have adverse effects on myocardial metabolic and functional recovery.

Adenosine Triphosphate↗
PubMed2006

Yeast cell inactivation related to local heating induced by low-intensity electric fields with long-duration pulses.

The effects of electric field (EF) treatments on Saccharomyces cerevisiae viability were investigated using a PG200 electroporator (Hoefer Scientific Instrument, San Fransisco, CA, USA) with specific attention to induced thermal effects on cell death. Lethal electric fields (1.5 kV cm(-1) for 5 s) were shown to cause heat variations in the cell suspension medium (water+glycerol), while corresponding classical thermal treatments at equivalent temperatures had no effect on the cells viability. Variations of the electrical conductivity of the intra- and extracellular matrix caused by ions and solutes transfer across the membrane were shown to be involved in the observed heating. The results permitted to build a theoretical model for the temperature variations induced by electric fields. Using this model and the electrical conductivity of the different media, a plausible explanation of the cell death induced by low-intensity electric fields with long-duration pulses has been proposed. Indeed, cell mortality could in part be caused by direct and indirect effects of electric fields. Direct effects are related to well known electromechanical phenomena, whereas indirect effects are related to secondary thermal stress caused by plasma membrane thermoporation. This thermoporation was attributed to electrical conductivity variations and the corresponding intracellular heating.

Colony Count, Microbial↗
PubMed1986

Spectral analysis of small-amplitude electrical activity in the cold potassium-arrested heart.

Recent reports have suggested that small-amplitude electrical activity may persist following the administration of potassium cardioplegia. This report confirms the presence of small-amplitude electrical activity in the potassium-arrested heart and describes a canine model that may be used to measure microvolt plunge-electrode potentials during ischemic arrest. Thirty-one adult mongrel dogs were placed on cardiopulmonary bypass and underwent 90 minutes of ischemic arrest. The heart was arrested with 10 ml per kilogram of body weight of crystalloid cardioplegia (20 mEq of KCl/L) at 4 degrees C. Core temperature was maintained at 26 degrees C and myocardial temperature, within a range of 8 degrees to 10 degrees C with topical ice-slush saline solution. Cardioplegic solution, 10 ml/kg, was reinfused every 30 minutes during the 90 minutes of ischemia. Electrical activity and transmural temperature were continuously monitored over the anterior surface of the left ventricle with specially designed plunge electrodes. Visual electrical and mechanical activity ceased in each animal after the infusion of cardioplegic solution, and was associated with an isoelectric electrocardiogram. However, microvolt (10(-6)V) small-amplitude electrical activity was recorded at a myocardial temperature of 10 degrees C in each animal during ischemic arrest, and the activity from 6 animals was stored on magnetic tape. Spectral analysis of electrical activity during cardioplegic arrest indicated that the fundamental frequency of small-amplitude electrical activity was in the range of 3.25 Hz. These data confirm the presence of small-amplitude electrical activity in the cardioplegia-arrested heart at 10 degrees C.

Animals↗
PubMed2004

Synaptic integration in electrically coupled neurons.

Interactions among chemical and electrical synapses regulate the patterns of electrical activity of vertebrate and invertebrate neurons. In this investigation we studied how electrical coupling influences the integration of excitatory postsynaptic potentials (EPSPs). Pairs of Retzius neurons of the leech are coupled by a nonrectifying electrical synapse by which chemically induced synaptic currents flow from one neuron to the other. Results from electrophysiology and modeling suggest that chemical synaptic inputs are located on the coupled neurites, at 7.5 microm from the electrical synapses. We also showed that the space constant of the coupled neurites was 100 microm, approximately twice their length, allowing the efficient spread of synaptic currents all along both coupled neurites. Based on this cytoarchitecture, our main finding was that the degree of electrical coupling modulates the amplitude of EPSPs in the driving neurite by regulating the leak of synaptic current to the coupled neurite, so that the amplitude of EPSPs in the driving neurite was proportional to the value of the coupling resistance. In contrast, synaptic currents arriving at the coupled neurite through the electrical synapse produced EPSPs of constant amplitude. This was because the coupling resistance value had inverse effects on the amount of current arriving and on the impedance of the neurite. We propose that by modulating the amplitude of EPSPs, electrical synapses could regulate the firing frequency of neurons.

Action Potentials↗
PubMed1997

Involvement of potentially distinct neurotensin receptors in neurotensin-induced stimulation of striatal [3H]dopamine release evoked by KCl versus electrical depolarization.

We intended to determine whether the effect of neurotensin (NT) on K+ and electrically evoked [3H]dopamine (DA) release from rat and guinea-pig striatal slices involved different mechanisms and/or receptors. In the two species, NT and three NT agonists were found to exhibit different relative potencies to enhance K+- and electrically-evoked [3H]DA release. NT(1-13) increased [3H]DA release with EC50 values in the nanomolar range and Emax values in the range of 100% of control. NT(8-13) and Eisai hexapeptide were both as active as NT(1-13) under K+ depolarization, but did not exceed 40% of the NT(1-13) effect under electrical depolarization. In rats, when [3H]DA release was stimulated with two successive K+ depolarizations, in the presence of NT(1-13), the NT effect during the second exposure to K+ was drastically decreased, suggesting that the NT receptor was desensitized. The desensitization process was essentially observed on Emax values, EC50 values being weakly affected. Similar results were obtained in guinea pig. In contrast, with two electrical depolarizations or with two different depolarizations (K+ followed by electrical), the NT effect during the second depolarization was not significantly affected. Concerning NT antagonists, SR 48692 antagonized with IC50 values in the nanomolar range the NT(1-13) stimulated K+-evoked [3H]DA release but did not affect, up to 10(-6) M, the NT(1-13) enhancement of electrically stimulated [3H]DA release. On the contrary, SR 142948A antagonized the NT(1-13) effect on K+- and electrically-evoked [3H]DA release. In conclusion, these results suggest the possible existence of potentially distinct neurotensin receptors differentially involved in the control exerted by NT on DA release under KCl vs electrical depolarization.

Adamantane↗
PubMed2000

Simultaneous recording of mechanical and intracellular electrical activity in guinea-pig urinary bladder smooth muscle: a comparison with human detrusor contraction.

OBJECTIVES: To study the relationship between the electrical and mechanical activity of guinea-pig detrusor muscle and compare this with the results obtained in human tissue. The guinea pig is the most used model to study the electrical basis of human bladder contraction. METHODS: We simultaneously recorded the mechanical and intracellular electrical activity in muscle strips. To study the effect of tissue movement on the membrane potential, the medium was made hypertonic with sucrose. Carbachol and KCl were applied to the bath to induce contractions. RESULTS: Carbachol resulted in a force response without a consistent change in the membrane electrical activity. KCl induced depolarization of the membrane associated with force development. Sucrose in the medium greatly impaired the ability to contract, without affecting the electrical activity. Compared with recordings in normal Krebs' solution, the resting membrane potential was not altered. In both media, spike-shaped potentials with variable amplitudes and shapes were recorded. These events were minimally affected by sucrose. CONCLUSIONS: In contrast to the response to KCl, the overall mechanical response of guinea-pig detrusor strips to muscarinic receptor stimulation did not correlate with the electrical activity of a single cell. Sucrose had only a minimal effect on the electrical activity, demonstrating that the electrical responses we measured were not affected by movement. Our intracellular recordings in guinea-pig tissue differed from the results obtained by other groups, but show great resemblance with those we recorded in human urinary bladder smooth muscle strips.

Animals↗
PubMed1997

Macrodipoles. Unusual electric properties of biological macromolecules.

The wide range of different effects induced by electric fields in biological macromolecules is clearly due to the unusual quality and quantity of their electric parameters. A general concept for a quantitative description of the polarizability of macromolecules remains to be established. In the case of DNA, experimental data indicate the existence of an effective polarization length N(p); at chain lengths N < N(p) the polarizability increases with N(2), whereas saturation is approached at N > or = N(p). The polarization length decreases with increasing ionic strength in close analogy to the Debye length, but is approximately 10 times larger than the Debye length. The dynamics of DNA polarization at high field strengths has been observed in the ns time range and is consistent with biased field induced ion dissociation. In the range of chain lengths from approximately 400 to approximately 850 base pairs DNA molecules exhibit permanent dipole moments, which are in a preferentially perpendicular direction to the end-to-end-vector, leading to a positive electric dichroism. These results are consistent with a "frozen" ensemble of bent DNA configurations and provide evidence for the existence of slow, non-elastic bending transitions. The electric parameters of proteins are usually dominated by a permanent anisotropy of the charge distribution, corresponding to permanent dipole moments of the order of several hundred Debye up to about 1500 Debye. Relatively small dipole moments of protein monomers add up to millions of Debye, when these proteins are in a vectorial organization in membrane patches, as found for bacteriorhodopsin and Na (+)K (+)-ATPase . In these cases the dipole vector may support vectorial ion transport. It is remarkable that the dipole moments of proteins usually show a relatively small dependence on the salt concentration; a rational for these observations is provided by a dipole potential at the plane of shear for rotational diffusion, which is defined in close analogy to the zeta-potential for translational diffusion. Symmetry breaking leading to huge electric dipole moments may be expected for mixed lipid vesicles: according to model calculations the phase separation of lipid components with and without net charges may lead to very high dipole moments; the expectation has been verified experimentally for vesicles containing DMPA and DMPC. The state of these systems should be extremely sensitive to electric fields. In summary, there is an unusual wide variation of electric parameters associated with biological macromolecules and with biomolecular assemblies, which is the basis for the complexity of different phenomena induced by electric fields in biological systems.

Journal Article↗
PubMed2000

Ion-protein dissociation predicts 'windows' in electric field-induced wound-cell proliferation.

There are many experiments showing that weak, non-thermal electric fields influence living tissues. In many cases, biological effects display 'windows' in biologically effective parameters of electric fields: most dramatic is the fact that relatively intense electric fields sometimes do not cause appreciable effect, while smaller fields do. Linear resonant physical processes do not explain frequency windows in this case. Both frequency and amplitude windows are evident from experiments on human dermal fibroblasts in a collagen matrix. For this in vitro model of skin, exposure to extremely low frequency (ELF) electric fields in the frequency range 10-100 Hz and the amplitude range of 0-130 microA/cm(2) macroscopic current density demonstrates such unusual 'window' behavior. Amplitude window phenomena suggest a non-linear physical mechanism. We consider non-linear quantum-interference effects on protein-bound substrate ions: These ions experience, due to electric fields in the media or biological tissue as small as 1 mV/m, electric gradients produced by polarized binding ligand atomic shells. The electric gradients cause an interference of ion quantum states. This ion-interference mechanism predicts specific electric-field frequency and amplitude windows within which fibroblast proliferation occurs.

Cell Division↗
PubMed1998

Study of fast switching processes due to electric and magnetic fields--an NMR approach.

Solid state NMR techniques have been developed to investigate dynamic molecular effects (e.g., molecular reorientations) due to simultaneously applied external electric fields on electrically sensitive materials such as liquid crystals (LC), liquid crystalline polymers (LCP) and polymeric electrets. Such effects can be observed only on relatively thin systems (10-200 microm). That means that many scans are necessary to achieve a sufficiently high signal-to-noise-ratio in the spectra (500-1000 scans). If the material is also magnetically sensitive, the electric field can be used to orient molecules in a starting orientational state and by switching-off the voltage to access fast reorientation processes in the magnetic field B0. Until now, the behaviour of orientable molecular systems under the influence of electric fields has been investigated by means of a more or less quasistatic approach (LCP: 100 V, electrets: 1 kV) in equilibrium states. The achievable time resolution depends on the desired signal-to-noise-ratio. For the case of proton NMR this means a time resolution of about 10 min. However, very often switching processes occur on a much shorter time scale. Using conventional techniques it is impossible to observe fast (ca. 100 micros) electrically or magnetically induced reorientation processes. In this work, we present a concept to overcome the problems outlined above and to extend the area of our current in situ NMR investigations on thin electrically-switched or poled polymeric layers. The basic idea is to include synchronized electric pulses during the NMR experiment using the preparation and/or mixing periods of a 1D or 2D pulse sequence for the application of an orienting field (electric or magnetic) and to use the reversibility of the molecular switching phenomenon to achieve a sufficient signal-to-noise-ratio. The techniques extend the range of possible investigations from about 100 micros to approximately T1 for correlated spectra (and to longer times of applied fields for uncorrelated spectra). Results are shown for a nematic LC and a nematic polymer having a similar side chain.

Electromagnetic Fields↗
PubMed1998

Regulation by tolbutamide and diazoxide of the electrical activity in mouse pancreatic beta-cells recorded in vivo.

1. The glucose-dependence of beta-cell electrical activity and the effects of tolbutamide and diazoxide were studied in anaesthetized mice. 2. In untreated animals there was a direct relationship between glycaemia and the burst pattern of electrical activity. Animals with high glucose concentration showed continuous electrical activity. The application of insulin led to a steady decrease in blood glucose concentration and a transition from continuous to oscillatory activity at 7.7+/-0.1 mM glucose (mean+/-s.d.) and a subsequent transition from oscillatory to silent at 4.7+/-0.6 mM glucose. 3. At physiological blood glucose concentrations the electrical activity was oscillatory. The injection of tolbutamide (1800 mg kg[-1]) transformed this oscillatory pattern into one of continuous electrical activity. The increased electrical activity was associated with a decrease in blood glucose concentration from 7.1+/-0.9 (control) to 5.5+/-1.0 mM (10 min after tolbutamide injection). The effects of tolbutamide are consistent with a direct blocking effect on the K(ATP) channel that leads to membrane depolarization. 4. The injection of diazoxide (6000 mg kg[-1]) hyperpolarized the cells and transformed the oscillatory pattern into a silent one. This is consistent with a direct stimulant effect by diazoxide on the K(ATP) channel. The use of tolbutamide or diazoxide correspondingly led to the lengthening or shortening of the active phase of electrical activity, respectively. This indicates that in vivo, such activity can be modulated by the relative degree of activation or inhibition of the K(ATP) channel. 5. These results indicate that under physiological conditions, tolbutamide and diazoxide have direct and opposite effects on the electrical activity of pancreatic beta-cells, most likely through their action on K(ATP) channels. This is consistent with previous work carried out on in vitro models and explains the drugs hypo- and hyperglycaemic effects.

Animals↗
PubMed2006

Review of in vivo static and ELF electric fields studies performed at Gazi Biophysics Department.

In vivo effects of Static Electric and ELF Magnetic and Electric fields have been carried out for more than 20 years in the Bioelectromagnetic Laboratory at the Biophysics Department of the Medical Faculty of Gazi University. In this article, the results of in vivo ELF Electric field studies are presented as a review. Static and 50 Hz ELF (Extremely Low Frequency) Electric (E) fields effects on free radical synthesis, antioxidant enzyme level, and collagen synthesis were analyzed on tissues of guinea pigs, such as brain, liver, lung, kidney, spleen, testis, and plasma. Animals were exposed to static and ELF electric fields with intensities ranging from 0.3 kV/m to 1.9 kV/m in vertical and horizontal directions. Exposure periods were 1, 3, 5, 7, and 10 days. Electric fields were generated from a specially designed parallel plate capacitor system. The results indicate that the effects of electric fields on the tissues studied depend significantly on the type and magnitude of electric field and exposure period.

Animals↗
PubMed1955

Mechanisms of direct and neural excitability in electroplaques of electric eel.

1. Current flow outward through the caudal, reactive membrane of the cell causes direct stimulation of the electroplaque. The electrical response in denervated as well as in normal preparations recorded with internal microelectrodes is first local and graded with the intensity of the stimulus. When membrane depolarization reaches about 40 mv. a propagated, all-or-nothing spike develops. 2. Measured with internal microelectrodes the resting potential is 73 mv. and the spike 126 mv. The latter lasts about 2 msec. and is propagated at approximately 1 M.P.S. 3. The latency of the response decreases nearly to zero with strong direct stimulation and the entire cell may be activated nearly synchronously. 4. Current flow inward through the caudal membrane of the cell does not excite the latter directly, but activation of the innervated cell takes place through stimulation of the nerve terminals. This causes a response which has a latency of not less than 1.0 msec. and up to 2.4 msec. 5. The activity evoked by indirect stimulation or by a neural volley includes a prefatory potential which has properties different from the local response. This is a postsynaptic potential since it also develops in the excitable membrane which produces the local response and spike. 6. On stimulation of a nerve trunk the postsynaptic potential is produced everywhere in the caudal membrane, but is largest at the outer (skin) end of the cell. The spike is initiated in this region and is propagated at a slightly higher rate than is the directly elicited response. Strong neural stimulation can excite the entire cell to simultaneous discharge. 7. The postsynaptic potential caused by neural or indirect stimulation may be elicited while the cell is absolutely refractory to direct excitation. 8. The postsynaptic potential is not depressed by anodal, or enhanced by cathodal polarization. 9. It is therefore concluded that the postsynaptic potential represents a membrane response which is not electrically excitable. Neural activation of this therefore probably involves a chemical transmitter. 10. The nature of the transmitter is discussed and it is concluded that this is not closely related to acetylcholine. 11. Paired homosynaptic excitation discloses facilitation which is not present when the conditioning stimulus is direct or through a different nerve trunk. These results may be interpreted in the light of the existence of a neurally caused chemical transmitter or alternatively as due to presynaptic potentiation. 12. The electrically excitable system of the electroplaque has two components. In the normal cell a graded reaction of the membrane develops with increasing strength of stimulation until a critical level of depolarization, which is about 40 mv. 13. At this stage a regenerative explosive reaction of the membrane takes place which produces the all-or-nothing spike and propagation. 14. During early relative refractoriness or after poisoning with some drugs (eserine, etc.) the regenerative process is lost. The membrane response then may continue as a graded process, increasing proportionally to the stimulus strength. Although this pathway is capable of producing the full membrane potential the response is not propagated. 15. Propagation returns when the cell recovers its regenerative reaction and the all-or-nothing response is elicited. 16. Excitable tissues may be classified into three categories. The axon is everywhere electrically excitable. The skeletal muscle fiber is electrically excitable everywhere except at a restricted region (the end plate) which is only neurally or chemically excitable. The electroplaque of the eel, and probably also cells of the nervous system have neurally and electrically excitable membrane components intermingled. The electroplaques of Raia and probably also of Torpedo as well as frog muscle fibers of the "slow" system have membranes which are primarily neurally and chemically excitable. Existence of a category of invertebrate muscle fibers with graded electrical excitability is also considered. 17. In the eel electroplaque and also probably in the cells of neurons, tests of the mode of neural activation carried out by direct or antidromic stimulation cannot reveal the neurally and chemically activated component. The data of such tests though they appear to prove electrical transmission are therefore inadequate for the detection and study of the chemically initiated process.

Acetylcholine↗
PubMed1994

Breast cancer mortality among female electrical workers in the United States.

BACKGROUND: Previous epidemiologic studies have suggested that exposure to electric or magnetic fields in occupational and residential environments may cause cancer. Recent experimental findings provide some support for the hypothesis that exposure to extremely low-frequency electromagnetic fields reduces the pineal gland's nocturnal production of the hormone melatonin, thereby increasing susceptibility to sex hormone-related cancers such as breast cancer. PURPOSE: Our purpose was to assess the evidence that cancer of the female breast might be associated with exposure to extremely low-frequency electromagnetic fields. METHODS: Records of women who had breast cancer as the underlying cause of their death (ICD-9 174) and control subjects (four per case) were selected from computer files of U.S. mortality data for the years 1985-1989. Women 20 years and older at the time of their death were eligible for inclusion if they were residents of and died in one of the 24 states that provided death certification records with occupation and industry codes to the National Center for Health Statistics for at least 1 year during the study interval. Data from death certificates were used to classify the case and control subjects with regard to potential occupational exposure to electric and magnetic fields. Control subjects were a random sample of women who died of any other underlying cause, excluding leukemia and brain cancer. RESULTS: The data analysis contrasted 68 women with breast cancer and 199 controls, all with electrical occupations, with 27,814 women with breast cancer and 110,750 controls, all of whom had other occupations. Electrical workers had excess mortality from breast cancer relative to other employed women [odds ratio (OR) = 1.38; 95% confidence interval (CI) = 1.04-1.82]). Adjusted ORs for specific electrical occupations were 1.73 (95% CI = 0.92-3.25) for electrical engineers, 1.28 (95% CI = 0.79-2.07) for electrical technicians, and 2.17 (95% CI = 1.17-4.02) for telephone installers, repairers, and line workers. There was no excess of breast cancer, however, in seven other occupations held more frequently by women and also involving potentially elevated electrical exposures, including telephone operators, data keyers, and computer operators and programmers. CONCLUSIONS: In light of the limitations inherent in death certification data and the design of this study, any conclusions regarding the hypothesis that exposure to extremely low-frequency electromagnetic fields causes breast cancer among women must be limited. Nevertheless, our findings are broadly consistent with that hypothesis and encourage further investigation with improvements in study design and data quality.

Adult↗
PubMed1989

Steps in the development of chemical and electrical synapses by pairs of identified leech neurons in culture.

Experiments have been made to follow the development of chemical and electrical transmission between pairs of leech neurons in culture. 1. The cell bodies of identified neurons were isolated from the CNS by suction after mild enzyme treatment, together with a length of the initial segment (or 'stump'). The neurons tested were Retzius cells (R), annulus erector motoneurons (AE), Anterior pagoda cells (AP) and pressure sensory cells (P). Pairs of cells were placed together in various configurations, with different sites on their surfaces making contact. 2. When pairs of Retzius cells were apposed with their stumps touching, serotonergic, chemically mediated synaptic transmission became apparent before electrical transmission. By 2.5 h impulses in either of the two Retzius cells produced hyperpolarizing inhibitory potentials in the other. These potentials were reversed by raised intracellular Cl and showed clear facilitation. The strength of chemical transmission between Retzius cells increased over the next 72 h. 3. After chemical transmission had been established, weak non-rectifying electrical transmission became apparent between Retzius cells at about 24-72 h. By 4 days coupling became stronger and tended to obscure chemically evoked synaptic potentials. 4. When pairs of Retzius cells were aligned in culture with the tip of one cell stump touching the soma of the other, chemical transmission also developed rapidly. Transmission was, however, in one direction, from stump to soma. At later stages non-rectifying electrical coupling developed as with stump-stump configuration. With the cell bodies of two Retzius cells apposed, electrical coupling developed after several days, before chemical transmission could be observed. 5. When Retzius and P cells were cultured with their stumps in contact, inhibitory chemical synaptic transmission developed within 24 h. Transmission was always in one direction, from Retzius to P cell. Electrical coupling of Retzius and P cells never occurred whatever the spatial relations of the cells to one another. 6. Annulus erector motoneurons, which contain ACh and a peptide resembling FMRFamide, first developed electrical coupling when the two stumps were in contact and then, later, bi-directional chemical transmission. Anterior Pagoda pairs placed stump-to-stump showed electrical connections. 7. Electronmicrographs revealed the presence of synaptic structures within 24 h after Retzius-Retzius, Retzius-P or AE-AE stumps were apposed. 8. The specificity of connections between cultured cells was similar to that observed in earlier experiments.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2006

Linear instability of a coflowing jet under an axial electric field.

A temporal linear stability analysis is carried out for a coflowing jet with two immiscible inviscid liquids under a uniform axial electric field. According to the electrical properties of the inner and outer liquids, four cases, i.e., IDOC (inner: dielectric; outer: conductor), ICOD (inner: conductor; outer: dielectric), ICOC (inner and outer: conductor), and IDOD (inner and outer: dielectric), are considered. The analytical dimensionless dispersion relation is derived for both axisymmetric and nonaxisymmetric perturbations and is solved for axisymmetric ones. Three unstable modes, i.e., the paravaricose, parasinuous and transitional modes, are identified in the Rayleigh regime. The influences of the axial electric field, liquid electrical properties, and Weber number are studied at length. The results show that the axial electric field has a generally stabilizing effect on the unstable modes. The effects of the liquid electrical properties are quite different but all great for each case. The change of dominant mode is detected with the variation of the electric field intensity, electrical properties or Weber number. It is found that the parasinuous instability is the easiest to realize in IDOC. And the comparison with the experiment validates that the parasinuous mode is predominant in coaxial electrospray.

Journal Article↗
PubMed1987

Myogenic electrical control activity in longitudinal muscle of human and dog colon.

1. The myogenic electrical activities of longitudinal muscle cells of the dog and human colon were investigated using intracellular microelectrodes. 2. The resting membrane potentials of dog and human longitudinal muscle cells at the serosal side of the muscle layer were -49.4 +/- 0.9 and -44.8 +/- 1.3 mV respectively. 3. Spontaneous electrical activity consisted of electrical oscillations of 13.7 +/- 1.1 mV and 8.6 +/- 2.1 mV amplitude, and 19.8 +/- 1.0 cycles/min and 26.1 +/- 1.6 cycles/min frequency for dog and human cells respectively. 4. Spiking activity only occurred superimposed on the electrical oscillations; the mean rate of rise of spikes was approximately 150 mV/s in the dog and approximately 260 mV/s in human cells and that of the oscillations was approximately 18 mV/s in the dog and approximately 16 mV in human cells. 5. Spiking activity was abolished by calcium influx blockers and 0.01 mM-calcium Krebs solution. The amplitude of the electrical oscillations was reduced to 0.2-1.0 mV 30 min after calcium influx blockade or 30 min in 0.01 mM-calcium Krebs solution. 6. Because of the high frequency of the oscillation-spike complexes, there was summation of associated contractile events in such a way that contraction frequency corresponded to frequency of bursts of oscillations and not to the frequency of the individual oscillations. 7. The resting membrane potential of the longitudinal muscle cells at the myenteric plexus side of the layer was -44.9 +/- 1.0 mV, significantly lower than at the serosal side. 8. A gradient in membrane potential and slow-wave amplitude exists in circular muscle of dog colon, with the highest value at the mucosal side (-68.4 and 28.1 mV respectively) and the lowest at the myenteric side (-62.5 and 8.6 mV) of the muscle layer. 9. Differences between resting membrane potential and electrical activity of longitudinal and circular muscle cells of the dog colon measured at the myenteric side of both muscle layers suggests absence of electrotonic coupling between the two types of cells. 10. Similarity of resting membrane potentials of longitudinal and circular muscle of the human colon suggests possible electronic coupling. 11. Since the electrical oscillations in longitudinal muscle control occurrence of spiking activity and type of contraction, they may be called 'electrical control activity'.

Action Potentials↗