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PubMed2003

Acceptability of manual versus electric aspiration for first trimester abortion: a randomized trial.

This study was conducted to compare the acceptability of manual and electric vacuum aspiration for first trimester elective abortion. Eighty-four women seeking abortions at less than 10 weeks gestation were randomized to abortion by manual or electric vacuum aspiration. Post-procedure questionnaires were administered to patients to assess pain, noise disturbance and overall satisfaction with the abortion procedure. Physicians reported procedural difficulty, their perceptions of patient discomfort and their overall acceptance of the procedure. Other outcomes included amounts of anesthesia required and complication rates. There were no significant differences in pain levels or satisfaction reported by patients; however, significantly more women in the electric group were bothered by noise (19% vs. 2%, p = 0.03). There were no differences in physician assessments of procedural difficulty; however, there were significantly more times in the electric group that physicians would have preferred manual aspiration (43% vs. 17%, p = 0.02). There were four crossovers from manual to electric, and none from electric to manual. It is concluded that physicians and patients find manual vacuum aspiration as acceptable as electric vacuum aspiration for elective abortions performed at less than 10 weeks gestation.

Abortion, Induced↗
PubMed1999

Experimental studies on affinity chromatography in an electric field.

A multicompartment electrolyzer, which has been used for preparative electrophoresis [Z. Liu, Z. Huang, J.-Y. Cong, et al., Sep. Sci. Technol. 31 (1996) 427], is applied for carrying out affinity chromatography in an alternating electric field. The effect of electric field strength on the adsorption and desorption characteristics is experimentally examined with human serum albumin and Blue Sepharose Fast Flow as a model system. It is shown that the existence of an electric field leads to a significant change in the adsorption capacity of the blue dye, which may be used for establishing a preferential adsorption to achieve a high resolution. The adsorption speed increases slightly with respect to the increase of electric field strength, while adsorption capacity in the presence of an electric field is independent of the electric field strength. Different elution behavior is observed as function of adsorption condition and a high recovery of the adsorbed protein is obtained when the adsorption is carried out in the presence of an electric field.

Buffers↗
PubMed1992

The effect of experimental urethral obstruction and its reversal on changes in passive electrical properties of detrusor muscle.

The passive electrical properties of guinea pig detrusor muscle were studied in order to determine how bladder outflow obstruction and reversal might modify the electrical activity of the bladder and, thus, contractility. Experimental bladder outflow obstruction was produced in guinea pigs and resulted in an increase in bladder weight with a decrease in spontaneous electrical activity, membrane time constant and space constant. In addition, the membrane Na-K pump activity increased with obstruction. Following reversal of obstruction, bladder weight gain associated with obstruction was only partially reversible. The decrease in the membrane time constant induced by obstruction was almost fully reversible following release of obstruction. In contrast, the membrane space constant which reflects spread of current, in addition to spontaneous electrical activity, were only partially reversible. The membrane Na-K pump activity of the detrusor muscle decreased to control levels following reversal of bladder outflow obstruction. There was no significant change in the resting membrane potential of detrusor smooth muscle with either obstruction or following reversal of obstruction. These results suggest, that, the changes in the bladder smooth muscle membrane electrical properties induced by experimental bladder outflow obstruction are only partially reversible following release of obstruction. Furthermore, the results suggest that, the dysfunctional cystometric patterns associated with bladder outflow obstruction might not only be due to changes in detrusor innervation but, fundamental reorganization of the detrusor's electrical syncytium with irreversible suppression of cell-to-cell transfer of electrical activity.

Action Potentials↗
PubMed1998

Faces and emotions: brain electric field sources during covert emotional processing.

Covert brain activity related to task-free, spontaneous (i.e. unrequested), emotional evaluation of human face images was analysed in 27-channel averaged event-related potential (ERP) map series recorded from 18 healthy subjects while observing random sequences of face images without further instructions. After recording, subjects self-rated each face image on a scale from "liked" to "disliked". These ratings were used to dichotomize the face images into the affective evaluation categories of "liked" and "disliked" for each subject and the subjects into the affective attitudes of "philanthropists" and "misanthropists" (depending on their mean rating across images). Event-related map series were averaged for "liked" and "disliked" face images and for "philanthropists" and "misanthropists". The spatial configuration (landscape) of the electric field maps was assessed numerically by the electric gravity center, a conservative estimate of the mean location of all intracerebral, active, electric sources. Differences in electric gravity center location indicate activity of different neuronal populations. The electric gravity center locations of all event-related maps were averaged over the entire stimulus-on time (450 ms). The mean electric gravity center for disliked faces was located (significant across subjects) more to the right and somewhat more posterior than for liked faces. Similar differences were found between the mean electric gravity centers of misanthropists (more right and posterior) and philanthropists. Our neurophysiological findings are in line with neuropsychological findings, revealing visual emotional processing to depend on affective evaluation category and affective attitude, and extending the conclusions to a paradigm without directed task.

Adult↗
PubMed2000

Conditions for similitude between the fluid velocity and electric field in electroosmotic flow

Electroosmotic flow is fluid motion driven by an electric field acting on the net fluid charge produced by charge separation at a fluid-solid interface. Under many conditions of practical interest, the resulting fluid velocity is proportional to the local electric field, and the constant of proportionality is everywhere the same. Here we show that the main conditions necessary for this similitude are a steady electric field, uniform fluid and electric properties, an electric Debye layer that is thin compared to any physical dimension, and fluid velocities on all inlet and outlet boundaries that satisfy the Helmholtz-Smoluchowski relation normally applicable to fluid-solid boundaries. Under these conditions, the velocity field can be determined directly from the Laplace equation governing the electric potential, without solving either the continuity or momentum equations. Three important consequences of these conditions are that the fluid motion is everywhere irrotational, that fluid velocities in two-dimensional channels bounded by parallel planes are independent of the channel depth, and that such flows exhibit no dependence on the Reynolds number. Similitude is demonstrated by comparing measured and computed fluid streamlines with computed electric flux lines.

Journal Article↗
PubMed2005

Strong effect of hydrodynamic coupling on the electric dichroism of bent rods.

The effect of hydrodynamic coupling on the spatial orientation of rigid bent rods in electric fields has been analyzed by Brownian dynamics simulations. Bead models for smoothly bent rods were constructed with dimensions of DNA double helices, and established simulation procedures were used to calculate their diffusion tensor, including the translational-rotational coupling tensor. The electric and optical parameters were assigned on the basis of known properties of double helices. Brownian dynamics simulations of the orientation of these models in electric fields showed that both transients and amplitudes of the calculated dichroism are very strongly dependent on translational-rotational coupling over a wide range of electric field strengths. For example, the stationary dichroism of a smoothly bent 179 bp DNA fragment calculated at low field strengths is positive in the presence and negative in the absence of hydrodynamic coupling. The transients are converted from a biphasic to a monophasic shape, when hydrodynamic coupling is turned off. The large changes resulting from hydrodynamic coupling were controlled by calculations based on analytical expressions derived for electrooptical response curves in the limit of low electric field strengths; the results obtained by this independent approach are in very satisfactory agreement with our Brownian dynamics simulations. The effect is strongly dependent on the electric dipole and on its direction. In the absence of any dipole the coupling effect was not observed. The coupling effect increases with the size of the bent rods. Because most macromolecular structures are known to have induced and/or permanent dipole moments, large effects of hydrodynamic coupling on both the amplitudes and the transients of the electric dichroism/birefringence must be expected in general for structures with nonsymmetric shape.

Journal Article↗
PubMed1999

Gestational maturation of electrical activity of the stomach.

Gestational maturation of gastrointestinal motility is a key factor in readiness of the preterm neonates for enteral nutrition. Since gastric motility mainly depends on the electrical activity of the smooth muscle cells, it was of interest to investigate the developmental aspects of electrical activity of the stomach. The latter was recorded weekly through cutaneous electrogastrography in 27 preterm infants (aged 29-34 weeks of gestation). Recordings were done for 1 hr before and 1 hr after meal. The electrogastrographic variables measured were: percentage of normal gastric rhythm, ie, 2-4 cpm; percentage of tachygastria (>4 cpm); the fed-to-fasting ratio of the dominant electrogastrographic power; and the instability coefficient of the dominant frequency. Data were compared with those measured in 10 full-term infants. Peaks of normal electrical activity (2-4 cpm) were present in most of the recordings at all the gestational ages; however, percentages of both normal electrical rhythm and tachygastria in preterm infants were similar to those measured in full-term infants (mean +/- SD) (normal rhythm; fasting: 70.2 +/- 3.8, fed: 72.2 +/- 5.0; tachygastria: fasting: 24.6 +/- 4.0, fed: 19.1 +/- 3.5) by 35 weeks of gestation (normal rhythm; fasting: 67.5 +/- 2.0, fed: 69.6 +/- 4.4; tachygastria: fasting: 27.1 +/- 4.0, fed: 25.6 +/- 4.1). The coefficient of instability of the dominant frequency in preterm infants was also similar to the value measured in full-term infants by 35 weeks of gestation, whereas the EGG power showed a significant increase in the postprandial state at all the gestational ages. We conclude that a maturation pattern of the electrical activity of the stomach can be detected by means of a noninvasive tool such as cutaneous electrogastrography: a normal electrical rhythm can be detected at very early gestational ages; however, this activity becomes dominant at around the 35 weeks of gestational age. In preterm infants developmental changes of gastric electrical activity are a function of advancing postnatal age.

Electrodiagnosis↗
PubMed2001

Comparison of the clinical effects and gingival abrasion aspects of manual and electric toothbrushes.

AIMS: The clinical effects and gingival abrasion aspects of 2 electrical tooth-brushes (Braun Oral-B Plak Control Ultra and the novel development Braun Oral-B Plak Control 3D) were to be compared with conventional manual tooth-brushing. MATERIAL AND METHODS: In a cross-over study, 26 dental student volunteers participated and were assigned to 1 of 3 groups. Following instruction in the use of the electric as well as manual toothbrushes, the volunteers were timed for 2 min each day to apply one electric or the manual toothbrush, respectively, during 3 experimental phases of 2 weeks. No other methods of tooth cleaning were to be performed except the one specified for the respective test period. When brushing manually, the Bass toothbrushing technique was applied. Between each test period, a recovery period of 1 week was allowed during which no oral hygiene was performed at all. At the start and the end of each of the experimental periods, the extension of plaque deposits from the gingival margin in coronal direction was assessed using the Turesky et al. modification of the Quigley and Hein plaque index. Presence or absence of gingival inflammation was evaluated by bleeding and probing (BOP). The extent and severity of gingival abrasions were assessed by use of a modified method of Breitenmoser et al. and adapted by Danser et al. RESULTS: The plaque-reducing effect was similar in all groups with the same cleaning regime. For that reason, the result of the different experimental phases with the respective cleaning modalities were collapsed. Cleaning with the Braun Oral-B Plak Control Ultra electric toothbrush resulted consistently in the lowest plaque scores when compared to both the Braun Oral-B Plak Control 3D and the manual toothbrush. Although the differences in plaque reduction were statistically significant between cleaning with Braun Oral-B Plak Control Ultra and 3D, they were small and of questionable clinical relevance. No significant differences in plaque reductions were found between manual brushing and any of the 2 electric brushes. Gingival abrasions were least pronounced following brushing with the Braun Oral-B Plak Control 3D electric toothbrush. However, no significant differences in gingival abrasion were encountered following brushing with the Braun Oral-B Plak Control Ultra electric in comparison with the manual toothbrush. CONCLUSIONS: The results of the present study have shown that in a group of dental students trained in manual brushing technique, where efficacy was similar with the 3 toothbrushes tested, there is no evidence of greater gingival abrasion with either Braun Oral-B Plak Control Ultra or 3D when compared with a manual brush.

Adult↗
PubMed2002

Observation of coupled magnetic and electric domains.

Ferroelectromagnets are an interesting group of compounds that complement purely (anti-)ferroelectric or (anti-)ferromagnetic materials--they display simultaneous electric and magnetic order. With this coexistence they supplement materials in which magnetization can be induced by an electric field and electrical polarization by a magnetic field, a property which is termed the magnetoelectric effect. Aside from its fundamental importance, the mutual control of electric and magnetic properties is of significant interest for applications in magnetic storage media and 'spintronics'. The coupled electric and magnetic ordering in ferroelectromagnets is accompanied by the formation of domains and domain walls. However, such a cross-correlation between magnetic and electric domains has so far not been observed. Here we report spatial maps of coupled antiferromagnetic and ferroelectric domains in YMnO3, obtained by imaging with optical second harmonic generation. The coupling originates from an interaction between magnetic and electric domain walls, which leads to a configuration that is dominated by the ferroelectromagnetic product of the order parameters.

Journal Article↗
PubMed2003

Single-nanowire electrically driven lasers.

Electrically driven semiconductor lasers are used in technologies ranging from telecommunications and information storage to medical diagnostics and therapeutics. The success of this class of lasers is due in part to well-developed planar semiconductor growth and processing, which enables reproducible fabrication of integrated, electrically driven devices. Yet this approach to device fabrication is also costly and difficult to integrate directly with other technologies such as silicon microelectronics. To overcome these issues for future applications, there has been considerable interest in using organic molecules, polymers, and inorganic nanostructures for lasers, because these materials can be fashioned into devices by chemical processing. Indeed, amplified stimulated emission and lasing have been reported for optically pumped organic systems and, more recently, inorganic nanocrystals and nanowires. However, electrically driven lasing, which is required in most applications, has met with several difficulties in organic systems, and has not been addressed for assembled nanocrystals or nanowires. Here we investigate the feasibility of achieving electrically driven lasing from individual nanowires. Optical and electrical measurements made on single-crystal cadmium sulphide nanowires show that these structures can function as Fabry-Perot optical cavities with mode spacing inversely related to the nanowire length. Investigations of optical and electrical pumping further indicate a threshold for lasing as characterized by optical modes with instrument-limited linewidths. Electrically driven nanowire lasers, which might be assembled in arrays capable of emitting a wide range of colours, could improve existing applications and suggest new opportunities.

Journal Article↗
PubMed2004

Simulation and experimental demonstration of the electric field assisted electroporation microchip for in vitro gene delivery enhancement.

Simulation and experimental demonstration of the in vitro gene delivery enhancement using electrostatic forces and electroporation (EP) microchips were conducted. Electroporation is a technique with which DNA molecules can be delivered into cells using electric field pulses. This study demonstrates that plasmid DNA can be attracted to the cell surfaces at the specific regions using an electrostatic force. Therefore, the DNA concentration on the cell surface is dramatically increased, which highly enhances the gene transfection efficiency compared to that without an attracting-electric field. The electrostatic force can be designed into specific regions, where the DNA plasmids are attracted to, to provide the region-targeting function. In this micro-device, the top electrode and the interdigitated electrodes provided the DNA attracting-electric field, and the interdigitated electrodes provided adequate electric fields for the electroporation process on the chip surface. Using the EP microchip, cells could be manipulated in situ without detachment if adherent cells were used for electroporation. Five different cells of two different types, primary cell and cell line, were successfully transfected under multi-pulse or single pulse electric field stimulation without applying an attracting-electric field. This study simulated and analyzed the electric field distributions at the DNA attracting and electroporation processes, and successfully demonstrated that the electrostatic force attracted DNA plasmids to specific regions and highly enhanced the gene delivery. In summary, this EP microchip should provide many potential applications for gene therapy.

Cell Line↗
PubMed1999

Electrical activity of the corpus cavernosum in denervated rats.

BACKGROUND: We evaluated the electrical activity of the corpus cavernosum after intracavernous papaverine injection in rats that had been denervated experimentally. METHODS: Twenty-four male adult Sprague Dawley rats were divided into three groups: (i) controls (n=8) (ii) unilateral cavernous nerve resection on the right side (n=8); and (iii) bilateral cavernous nerve resection (n=8). Through a suprapubic incision, the urinary bladder was retracted laterally to locate the major pelvic plexus on the lateral surface of the prostate. The major branch of the cavernous nerve, running caudally from the pelvic plexus, was isolated and excised using an operating microscope. Three weeks later, recording of the electrical activity of the corpus cavernosum (EACC) was performed by using a Neuropack-2 EMG unit (Nihon Kohden, Tokyo, Japan) and coencentric needle electrode. Changes in amplitude were evaluated before and after intracavernosal papaverine injection. The results in the flaccid state and after papaverine injection were compared by using the Mann Whitney U-test in all three groups and paired t-test between groups. RESULTS: In the flaccid penis, the mean (+/- SD) amplitude of electrical activity of the corpus cavernosum was 17.42+/-2.05, 12.42+/-1.88, 9.71+/-1.59 and 5.85+/-0.96 microV in control rats, in unilaterally denervated rats (in which the cavernous nerve was intact on the left side), in unilaterally denervated rats in which the cavernous nerve was resected on the right side and in bilaterally denervated rats, respectively. In the flaccid state, EACC is lower in the bilaterally denervated group than in the control and unilaterally nerve-resected groups (P < or = 0.05). The recording of electrical activity of the corpus cavernosum was continued for 20 min after papaverine injection. In the control group and in both groups of unilaterally denervated rats, we observed a significant decrease in the electrical activity of the corpus cavernosum in the first 5 min after papaverine injection (P < or = 0.05). However, no difference was observed in bilaterally denervated rats after injection (P > or = 0.05). CONCLUSIONS: We conclude that electrical activity of the corpus cavernosum continues after unilateral nerve injury in rats. Cross-innervation may play a role in penile innervation and corpus cavernosum electromyography shows electrical activity in denervated rats.

Animals↗
PubMed2001

Electrical muscle stimulation as an adjunct to exercise therapy in the treatment of nonacute low back pain: a randomized trial.

A prospective, randomized, double-blind, placebo-controlled clinical trial was performed to investigate the efficacy of electrical muscle stimulation when combined with a therapist-guided, standardized exercise therapy program in the treatment of nonacute low back pain. Eighty patients with low back pain of at least 6 weeks' duration were randomized into the following 2 groups: standardized exercise therapy with functional electrical muscle stimulation or standardized exercise therapy with placebo electrical stimulation. Subjects were evaluated at baseline, 2 months, and 6 months with a standardized back pain questionnaire and objective measurements of lumbar spine function. Exercise therapy was continued for 6 months, but electrical stimulation was discontinued at the 2-month interval. Of the 80 patients initially enrolled, 42 discontinued or withdrew before completing the entire study protocol. At the 2-month follow-up interval, subjects in the treatment group had statistically significantly improved lumbar spine function compared with the control subjects. This effect continued during the last 4 months of the study after electrical stimulation had been discontinued. This suggests that electrical muscle stimulation can be an effective adjunctive treatment modality for nonacute low back pain. The effects of this combined therapy seem to last beyond the duration of electrical stimulation treatment.

Clinical Trial↗
PubMed1986

Blockade of electrical activity promotes the death of mammalian retinal ganglion cells in culture.

During the first 2 postnatal weeks, up to 50% of the ganglion cells in the mammalian retina normally die. Natural cell death may result from several factors, and electrical activity has been proposed as one critical element. Recent experiments in vivo using intraocular injection of tetrodotoxin (TTX) have suggested that competition for survival between ganglion cells from the two eyes is mediated by their degree of neuronal activity. In addition, the level of activity of afferents to the ganglion cells has been postulated to be an important variable in determining their survival. To investigate the mechanism of cell death engendered by altered activity, I studied the effect of electrical blockade with TTX (to block sodium channels and thus action potentials) or low Ca/high Mg (to block transmitter release and hence synaptic activity) on individual neurons in vitro. For this purpose, identified retinal ganglion cells (RGCs) from postnatal rats were maintained in culture. Unlike the previous in vivo experiments, this approach permitted the exact concentration of each agent to be controlled and the electrical activity of the RGCs to be recorded. In cultures from animals of postnatal day 2-10 (P2-10), 1 microM TTX or 0.2 mM Ca/20 mM Mg resulted in the death of about 50% of the RGCs, representing those cells that had displayed spontaneous electrical activity, but did not affect RGCs that lacked activity. However, the death of RGCs with spontaneous activity from P11-13 animals was not influenced by these drugs. These findings suggest that during a critical period of development neurons become dependent upon electrical activity, and the cessation of this activity can result in their death. In addition, conditioned medium, collected from cultures lacking TTX, rescued from death a large proportion of TTX-treated RGCs. Thus, the critical element for survival may represent modulation of a trophic factor related to the level of activity rather than electrical activity itself. Since, in vivo, natural cell death occurs in neurons of similar type and age, and in the same proportion as that induced by the artificial blockade of electrical activity in culture, these findings may be germane to the mechanism of natural cell death in the retina.

Action Potentials↗
PubMed1993

Electrical activity-dependent regulation of the acetylcholine receptor delta-subunit gene, MyoD, and myogenin in primary myotubes.

Expression of the skeletal muscle acetylcholine receptor (AChR) is regulated by nerve-evoked muscle activity. Studies using transgenic mice have shown that this regulation is controlled largely by transcriptional mechanisms because responsiveness to electrical activity can be conferred by transgenes containing cis-acting sequences from the AChR subunit genes. The lack of a convenient muscle cell culture system for studying electrical activity-dependent gene regulation, however, has made it difficult to identify the important cis-acting sequences and to characterize an electrical activity-dependent signaling pathway. We developed a muscle culture system to study the mechanisms of electrical activity-dependent gene expression. Gene fusions between the murine AChR delta-subunit gene and the human growth hormone gene were transfected into primary myoblasts, and the amount of growth hormone secreted into the culture medium from either spontaneously electrically active or inactive myotube cultures was measured. We show that 181 bp of 5'-flanking DNA from the AChR delta-subunit gene are sufficient to confer electrical activity-dependent gene expression. In addition, we show that the rate of AChR delta-subunit gene expression differs among individual nuclei in a single myotube but that highly expressing nuclei are not necessarily colocalized with AChR clusters. We also show that expression of MyoD and myogenin are regulated by electrical activity in primary myotube cultures and that all nuclei within a myotube express similar levels of MyoD and similar levels of myogenin.

Animals↗
PubMed2004

Wavelet analysis in a canine model of gastric electrical uncoupling.

Abnormal gastric motility function could be related to gastric electrical uncoupling, the lack of electrical, and respectively mechanical, synchronization in different regions of the stomach. Therefore, non-invasive detection of the onset of gastric electrical uncoupling can be important for diagnosing associated gastric motility disorders. The aim of this study is to provide a wavelet-based analysis of electrogastrograms (EGG, the cutaneous recordings of gastric electric activity), to detect gastric electric uncoupling. Eight-channel EGG recordings were acquired from 16 dogs in basal state and after each of two circular gastric myotomies. These myotomies simulated mild and severe gastric electrical uncoupling, while keeping the separated gastric sections electrophysiologically active by preserving their blood supply. After visual inspection, manually selected 10 min EGG segments were submitted to wavelet analysis. Quantitative methodology to choose an optimal wavelet was derived. This 'matching' wavelet was determined using the Pollen parametrization for 6-tap wavelet filters and error minimization criteria. After a wavelet-based compression, the distortion of the approximated EGG signals was computed. Statistical analysis on the distortion values allowed us to significantly (p < 0.05) distinguish basal state from mild and severe gastric electrical uncoupling groups in particular EGG channels.

Algorithms↗
PubMed1988

A review of epidemiological studies of the health effects of living near or working with electricity generation and transmission equipment.

In the last ten years there has been increasing concern that the extremely low frequency (ELF), non-ionising electromagnetic fields emitted by electrical installations and equipment using alternating current at 50-60 Hertz might have long-term effects on health. Studies of the association between disease and residence near installations transmitting or generating electricity and studies of the health of workers in the electrical industry are reviewed. Most of the investigations relate to cancer, although other conditions such as outcome of pregnancy have been studied. The most consistent finding is that electrical workers appear to be at increased risk of leukaemia, especially acute myeloid leukaemia. The effect is small. Combining the results of eleven separate investigations suggests an 18% increase in the risk of leukaemia (RR = 1.18, 95% confidence interval (CI) 1.09-1.29) which is partly or wholly due to a 46% increase in the risk of acute myeloid leukaemia (RR = 1.46, 95% CI 1.27-1.65). It is not clear whether this increase is specific to certain types of work within the electrical industry. Nor is it possible to determine from the available data if the increase in leukaemia is due to electromagnetic fields or to other factors to which electrical workers are exposed. There is no clear association between cancer risk and residence near sources transmitting electricity, although some data suggest that there may be small increases in leukaemia in those living very close to the sources. The relationship between adverse outcome of pregnancy and exposure to sources of ELF electromagnetic fields needs further investigation. Studies of the possible effects of ELF electromagnetic fields on health are hampered by problems in measuring exposure and by the ubiquity of exposure in the community.

Adolescent↗
PubMed1997

Functional electrical properties of the endothelium in lymphatic vessels of the guinea-pig mesentery.

1. The resting and agonist-stimulated properties of endothelial cells and electrical communication between the endothelium and smooth muscle were investigated in open segments of guinea-pig mesenteric lymphatic vessels using intracellular microelectrodes. 2. Endothelial cells had a mean resting membrane potential (RMP) of -71.5 +/- 0.5 mV (n = 100) which was significantly different from the value of -60.8 +/- 1.1 mV (n = 75) recorded in smooth muscle. 3. Acetylcholine (ACh, 5-10 microM) generally evoked an initial hyperpolarization followed by depolarization (mean 3.4 +/- 0.5 mV and 15.4 +/- 1.0 mV, respectively, n = 75). 4. Ca(2+)-activated K+ channels were likely to underlie the ACh-induced hyperpolarization as this response exhibited an increased in membrane conductance, was larger in 0.5 mM K+ solution and was blocked by charybdotoxin (50 nM). 5. The endothelium did not exhibit a response to nitric oxide (NO) as the NO-donor sodium nitroprusside did not alter the RMP and the electrical responses to ACh were not affected by the NO-synthase inhibitor N omega-nitro L-arginine at a concentration which markedly inhibited smooth muscle hyperpolarization. 6. Electrical coupling between the endothelium and smooth muscle was not functional as there was extremely limited electrical continuity (1 in 12, endothelial/smooth muscle cell simultaneous recordings) and bradykinin, noradrenaline and isoprenaline caused different electrical responses in the two cell types. 7. These results provide the first description of RMP and electrical responses to various agonists in the lymphatic endothelium and its lack of functional electrical coupling with the smooth muscle.

Acetylcholine↗