|
| ||
|
|
||
Bipolar Electrodes (bipolar + electrode)
Selected AbstractsPreemptive effect of nucleus of the solitary tract stimulation on amygdaloid kindling in freely moving catsEPILEPSIA, Issue 3 2010Victor M. Magdaleno-Madrigal Summary Purpose:, The nucleus of the solitary tract (NTS) is a primary site where vagal afferents terminate. The aim of this study was to analyze the preemptive effect of NTS electrical stimulation on daily amygdaloid kindling (AK) in freely moving cats. Methods:, Seven adult male cats were used. Bipolar electrodes were stereotaxically implanted into both amygdalae, lateral geniculate bodies, hippocampi, and prefrontal cortices. In addition, a bipolar stainless steel electrode was implanted in the left NTS. Cats were recorded under the following experimental conditions: The NTS was stimulated for 6 days before the initiation of AK (1 min on/5 min off, 1 h total). AK was performed by stimulating the amygdala every 24 h (1 s, 60 Hz, 1 ms) until behavioral stage VI was reached. Results:, The number of stimulations to reach stage VI in control animals was 23.4 ± 3.7, in lateral tegmental field (LTF) animals was 17.0 ± 2.1 days. Animals subjected to preemptive NTS stimulation showed a significant increase (53.8 ± 5.9). In addition, behavioral development was retarded, with an increase in the number of stimulations required to reach stage III. In this group, overall kindling development was delayed, and amygdaloid afterdischarge duration did not show a progressive increase as was observed in the control group. Discussion:, Our results indicate that preemptive NTS electrical stimulation interferes with epileptogenesis. This anticonvulsive effect could be related to the activation of certain structures that inhibit seizure development. Therefore, results suggest that NTS mediates the anticonvulsive effect of vagus nerve stimulation. [source] Abnormal Excitability of Hippocampal CA3 Neurons in Noda Epileptic Rat (NER): Alteration of Seizure with AgingEPILEPSIA, Issue 2000Ryosuke Hanaya Purpose: Noda epileptic rat (NER), a mutant found in thc colony of Crj:Wistar rats, spontaneously shows tonic-clonic convulsions approximately once every 30 hours from 8,16 weeks of age. A long-lasting dcpolarization shift accompanied by repetitivc firings are observed in hippocampal CA3 pyramidal neurons of NER with seizures. Using hippocampal slice preparations of NER, the present electrophysiologi- cal study was performed to elucidate whether this abnormal firing in CA3 neurons developed with age and if abnormality of Ca2+ channel was involved. Methods: Hippocampal slices (40Opm) werc prepared from NER and normal Wistar rats (age; 4,29 weeks). A single rectangular pulse stimulus composed of 0.1-ms duration was delivered to the mossy fibers every 5 seconds though a bipolar electrode placed in the granular cell layer of the dentate gyrus. Intracellular recording was made from the CA3 pyramidal cell using a microelectrode containing 3M KCI intracellular recordings. A Ca2+ spike was elicited by applying a depolarizing pulse (InA, 120ms) in the cell through the recording electrode under a blockadc of Na+ and K+ channels using 1 pM tetrodotoxin and I 0mM tctraethylammonium added to the artificial CSF, respectivcly. Nicardipine (I-IOOnM), a Ca2+ channel blocker, was applicd to the bath. Results: Thirty-seven slices from I9 NER and 6 slices from 4 normal Wishe rats were used. There were no obvious changes in the resting membrane potentials of CA3 neurons between NER and Wistar rats tested. When a single stimulus was delivered to the mossy fibers, a long-lasting depolarization shift accompanied by repetitive firings followed by after-hyperpolarization werc also obtained i n hippocampal CA3 neurons of young NER (4,5 weeks of age) before occurrence of any seizurcs, although the depolarization shift in younger NER was shorter than that in NER aged more than 6 weeks. These abnormal firings werc evokcd in 58% and 30% of all CA3 neurons tested in the younger and mature NER (6,1 5 weeks of age), respectively. Furthermore, abnormal firing was not elicited in NER aged after I6 weeks. Agc-matched Wistar rats showed only single action potentials without any depolarization shift with single mossy fiber stimulation. Bath application of nicardipine (IOnM) inhibited this long-lasting depolarization shift and the accompanying repetitive firing followed by afterhypcrpolarization without affecting the first spike induced by mossy fiber stimulations. Furthermore, nicai-dipine (IOnM) inhibited the Ca2+ spikes elicited by applying a depolarizing pulse in the neurons of NER with seizures, although a higher dose (100nM) did not affect those in Wistar rats. Conclusions: These findings indicate that abnormal excitability of the NER CA3 pyramidal neurons is probably due to abnormality in the Ca2+ channcls. The abnorinal excitability was observed in NER at an age when tonic-clonic convulsions were not detected, suggesting that thc hippocampus may probably scrve as an epileptogenic focus in younger NER and the seizure impulses originating i n this area are transinittcd to the new other seizurc foci in mature NER. [source] Entrainment by an Extracellular AC Stimulus in a Computational Model of Cardiac TissueJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2001JASON M. MEUNIER B.S. Sinusoidal Stimulation of Cardiac Sheet.Introduction: Cardiac tissue can be entrained when subjected to sinusoidal stimuli, often responding with action potentials sustained for the duration of the stimulus. To investigate mechanisms responsible for both entrainment and extended action potential duration, computer simulations of a two-dimensional grid of cardiac cells subjected to sinusoidal extracellular stimulation were performed. Methods and Results: The tissue is represented as a bidomain with unequal anisotropy ratios. Cardiac membrane dynamics are governed by a modified Beeler-Reuter model. The stimulus, delivered by a bipolar electrode, has a duration of 750 to 1,000 msec, an amplitude range of 800 to 3,200 ,A/cm, and a frequency range of 10 to 60 Hz. The applied stimuli create virtual electrode polarization (VEP) throughout the sheet. The simulations demonstrate that periodic extracellular stimulation results in entrainment of the tissue. This phase-locking of the membrane potential to the stimulus is dependent on the location in the sheet and the magnitude of the stimulus. Near the electrodes, the oscillations are 1:1 or 1:2 phase-locked; at the middle of the sheet, the oscillations are 1:2 or 1:4 phase-locked and occur on the extended plateau of an action potential. The 1:2 behavior near the electrodes is due to periodic change in the voltage gradient between VEP of opposite polarity; at the middle of the sheet, it is due to spread of electrotonic current following the collision of a propagating wave with refractory tissue. Conclusion: The simulations suggest that formation of VEP in cardiac tissue subjected to periodic extracellular stimulation is of paramount importance to tissue entrainment and formation of an extended oscillatory action potential plateau. [source] Evaluation of Fractal-Coated Temporary Pacing Leads in the Early Postoperative CoursePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2008FRITZ MELLERT M.D. Background:The performance of temporary pacing wires is still limited by capture and sensing problems. Fractal coating can enhance electrical properties and reliability. We therefore investigated fractal-laminated wires in comparison with conventional wires. Methods:In 21 patients two unipolar, fractal-coated pacing wires (fe) and one conventional bipolar electrode (se) were implanted in ventricular position. Afterward pacing threshold (V), R-wave sensing (mV), lead impedance (ohm), and slew-rate (mV/s) were measured. Loss of capture or sensing and dislocation was documented. fe wires were examined with energy dispersive x-ray diffraction (EDX)-analysis and scanning electrode microscopy (SEM). Results:Failure in pacing was less frequent in fe wires. Also fe leads had lower pacing thresholds at implantation (0.76 ± 0.15 V vs 1.51 ± 0.95 V, P< 0.0001) and afterward. Furthermore fe wires showed lower increase of pacing threshold/time (0.25 V/day vs 0.42 V/day). R-wave sensing and slew-rate values in the fe group on day of operation (5.81 ± 4.80 mV; 0.63 ± 0.71 V/s) were lower than in the se group (10.37 ± 6.89 mV; 1.85 ± 1.71 V/s P< 0.0001) and afterward. Nevertheless, decrease of amplitude/time was lower in fe wires (0.17mV/day vs 0.46 mV/day). fe wires always had lower impedance values. Conclusions:Lower pacing threshold and increase of threshold/time in fe wires indicate more reliable function. Initial lower sensitivity values are still not understandable and must be investigated. However, fe wires, constancy of sensing and impedance values was more stable, so fe epicardial wires can be recommended for safe and feasible use. [source] Penile and clitoral stimulation for faecal incontinence: external application of a bipolar electrode for patients with faecal incontinenceCOLORECTAL DISEASE, Issue 1 2004F. A. Frizelle Abstract Objective, The aim of this study was to assess the effect of a novel pudendal nerve stimulator on clinical and anorectal manometric parameters in patients with faecal incontinence. Method, Retrospective cohort analysis of consecutive patients presenting with faecal incontinence who had failed initial conservative treatment and were not suitable for surgical intervention in a university hospital incontinence clinic. Biofeedback using a pudendal nerve stimulator comprising a bipolar electrode applied to the base of the clitoris or penis. Electrical pulse voltage was self-titrated and defined periods of treatment were prescribed. Anorectal manometry and Cleveland incontinence scores were assessed. Results, There was a significant reduction in incontinence symptom score after pudendal nerve stimulator treatment in the 42 patients treated and who had a complete set of data (median age 57 years (range 37,81); 39 female, 3 male). This was accompanied by significant improvements (P < 0.05) in anal sphincter tone, maximal tolerated rectal volume and the sustained rectoanal inhibitory reflex. Conclusions, An externally applied pudendal nerve stimulator improves symptoms and physiological evidence of faecal incontinence but long-term follow up is not available for these patients. [source] Development of Amygdaloid Kindling in Histidine Decarboxylase,deficient and Histamine H1 Receptor,deficient MiceEPILEPSIA, Issue 4 2004Tadashi Hirai Summary: Purpose: This study attempted to clarify the role of histamine or histamine H1 receptors in the development of amygdaloid kindling by using histidine decarboxylase (HDC)-deficient and histamine H1 receptor (H1R)-deficient mice. Methods: Under pentobarbital anesthesia, mice were fixed to a stereotaxic apparatus, and bipolar electrodes were implanted into the right amygdala. Electrodes were connected to a miniature receptacle, which was embedded in the skull with dental cement. A bipolar electroencephalogram was recorded; bipolar stimulation of the amygdala was applied every day with a constant-current stimulator and continued until a generalized convulsion was obtained. Results: The development of amygdaloid kindling in HDC-deficient and H1R-deficient mice was significantly accelerated compared with that in their respective wild-type mice. In addition, the afterdischarge (AD) duration and generalized seizure duration in HDC-deficient and H1R-deficient mice were prolonged. Intraperitoneal injection of histidine resulted in an inhibition of amygdaloid kindled seizures in wild-type mice at doses that caused an increase in the histamine contents of the brain. However, no significant effect was observed with histidine in H1R-deficient mice at the same dose. Conclusions: These findings suggest that histaminergic mechanisms through H1 receptors play a crucial role not only in amygdaloid kindled seizures but also in the development of amygdaloid kindling. [source] Influence of Wavefront Dynamics on Transmembrane Potential Characteristics During Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2000CHARLES A. ATHILL M.D. Transmembrane Potential Characteristics. Introduction: Although computerized mapping studies have demonstrated the presence of multiple wavelets during atrial fibrillation (AF) and that action potential amplitude and duration in AF vary significantly from beat to heat, no study has correlated the single cell action potential changes with the patterns of activation during AF. Methods and Results: We studied wavefront dynamics and single cell transmembrane potential (TMP) characteristics in 12 isolated perfused canine right atria. The endocardial surface was mapped using 477 bipolar electrodes while TMP was recorded with a standard glass microelectrode from an epicardial cell. AF was induced in the presence of acetylcholine. Successful simultaneous TMP recordings and activation maps were made during six episodes of AF and for a total of 141 activations. Large variations of TMP amplitude and duration were observed frequently; 34% of them have a low amplitude (<50% of the amplitude recorded during pacing). Low-amplitude potentials were recorded when the impaled cell was (1) in an area of random reentry (67%, n = 36); (2) within 3.2 mm of the core of organized functional reentry (22%, n = 12); (3) in the middle of two merging wavefronts (9%, n = 5); and (4) at the point of spontaneous wavebreak (2%, n = 1). Conclusion: Large variations of TMP are observed frequently during in vitro AF. Low-amplitude TMPs are associated with specific patterns of AF activation wavefronts. [source] Effluent treatment using a bipolar electrochemical reactor with rotating cylinder electrodes of woven wire meshesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2009Javier M Grau Abstract BACKGROUND: The behaviour of a bipolar electrochemical reactor consisting of one or more rotating cylinder electrodes of woven wire meshes is reported using copper and cadmium deposition from dilute solutions as test reactions. RESULTS: The best performance related to electrode number was determined for copper deposition and was achieved by an arrangement with two bipolar electrodes, for which the conversion in a single pass was approximately 47%. The specific energy consumption was 3.27 kWh kg,1 with a normalised space velocity of 23.05 h,1. The copper powder obtained showed a nodular and dendritic surface morphology. This reactor configuration was also analysed for cadmium deposition, in which hydrogen evolution takes place simultaneously as a side cathodic reaction, considering the effect of flow rate and total current. The maximum conversion per pass for cadmium removal was 38.91%. In this case the reactor with two bipolar electrodes showed a performance similar to that of a monopolar reactor operated at a rotation speed three times higher. CONCLUSION: A continuous electrochemical reactor with two rotating bipolar electrodes of woven wire meshes presents a good performance for copper or cadmium removal from dilute solutions. Copyright © 2009 Society of Chemical Industry [source] Possible gender-related differences in a jaw reflex evoked by stimulation of the human lipJOURNAL OF ORAL REHABILITATION, Issue 9 2002M. F. LYONS It has been reported that the latency of the jaw jerk reflex in symptom-free human female subjects is significantly shorter than in male subjects (Kossioni et al., 1994). In the present study, we have begun to investigate whether there are any gender-related differences in other jaw reflexes. The EMG recordings were made from an active masseter muscle in 16 young adult age-matched subjects (eight male, eight female; aged 20,43 years). Inhibitory reflexes were evoked in the muscle by applying stimuli through bipolar electrodes clipped over the lower lip with the cathode placed intraorally on the oral mucosa. While the stimuli were being applied, the subjects maintained the EMG level at around 10% of maximum with the aid of visual feedback. The presence or absence of reflex responses was determined as previously described (Louca et al., 1996). Wilcoxon Rank Sum tests were used to compare the properties of the short- (,10,15 ms) and long- (,40,50 ms) latency inhibitory reflexes evoked by the stimuli in the two groups. There was no significant difference between the male and female groups in the threshold or latency of either reflex. However, the duration of the long-latency inhibition was significantly shorter in females than in males (median values: 29·0 versus 44·0 ms, P=0·015). These preliminary findings suggest that, at least in young human subjects, there is a gender-related difference in the strength but not in the presence of long-latency inhibitory jaw reflexes. [source] Electromyography of scoliotic patients treated with a braceJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2003Daniel Odermatt Abstract When a brace is used to correct spinal deviation, patients may seek to ease the discomfort from the pressure exerted by the orthosis by actively recruiting specific trunk muscles. The effect of bracing on trunk electromyography (EMG) has been reported in only one study where a limited number of electrodes were placed mainly in the thoracic region. Our hypothesis was that a multi-electrode mapping of the activity of the thoracic, lumbar, and abdominal trunk muscles would provide a more representative picture of the muscular reaction in response to bracing. With a larger number of EMG measuring sites, the presence of any brace-induced trunk muscle activity should be detected. Therefore, EMG signals of 11 adolescent idiopathic scoliosis patients who had been undergoing Boston brace treatment for 0.7-3 years were collected during four isometric tasks to evaluate the response of trunk muscles in the minutes following the application of the brace. Twenty-two pairs of bipolar electrodes were used to measure the EMG signals of the main superficial trunk muscles during four isometric tasks. EMG signals of trunk muscles were compared in braced and unbraced conditions. Brace-induced increases in EMG activity were significant in 43% of the individual measurements and in three of the four tasks for the group mean values. Increases were greater in the lumbar area, especially on the convex side of the secondary (lumbar) curve. These results thus suggest that immediately following the application of the brace, significant muscular responses can be observed in some patients. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] The incretin hormones GIP and GLP-1 in diabetic rats: effects on insulin secretion and small bowel motilityNEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2009T. Edholm Abstract, Incretin hormones often display inhibitory actions on gut motility. The aim of this study was to investigate if altered responsiveness to glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1) as regards insulin release and small bowel motility could bring further clarity to the pathophysiology of diabetes in the Goto-Kakizaki (GK) rat. The isolated perfused pancreas was studied in male GK and Wistar rats (controls) under euglycemic and hyperglycemic conditions. Glucose-dependent insulinotropic peptide (10 nmol L,1) or GLP-1 (10 nmol L,1) were added to the medium and perfusate was collected and analysed for insulin. Moreover, GK and Wistar rats were supplied with bipolar electrodes in the small bowel and myoelectric activity was recorded during intravenous administration of GIP (1,400 pmol kg,1 min,1) or GLP-1 (0.1,20 pmol kg,1 min,1). Finally, tissue was collected from GK and Wistar rats for RNA extraction. Under euglycemia, GIP and GLP-1 stimulated the initial insulin response by 10-fold in GK rats (P < 0.05). At later hyperglycemia, the insulin response to GIP and GLP-1 was blunted to about one-third compared with controls (P < 0.05). In the bowel GLP-1 was about 2.6,16.7 times more potent than GIP in abolishing the migrating myoelectric complex in the GK and control rats. Polymerase chain reaction (PCR) showed GIP and GLP-1 receptor gene expression in pancreatic islets and in small bowel. The initially high, but later low insulin responsiveness to stimulation with GIP and GLP-1 along with inhibition of small bowel motility in the GK rat indicates a preserved incretin response on motility in diabetes type 2. [source] 12 Effects of synchronized intestinal electrical stimulation on small intestinal motility in dogsNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2006J YIN Our previous studies showed that synchronized gastric electrical stimulation enhanced antral contractions, accelerated gastric emptying in dogs. It has never been reported whether synchronized electrical stimulation could improve small intestinal motility. The aim of this study was to investigate the effects of synchronized intestinal electrical stimulation (SIES) on small bowel motility in both fasting and fed states in dogs. Methods:, Five healthy female dogs (18,24 kg) were equipped with a duodenal cannula for the measurement of small bowel motility using manometry. Two pairs of bipolar electrodes were implanted on the small intestinal serosa with an interval of 25 cm; the first one was 10 cm beyond the pylorus and used for stimulation. The experiment was consisted of four sessions in each dog with a randomized order. In the fasting state, 20 min after occurrence of phase III, SIES was initiated and maintained for 45 min, small bowel motility was recorded during the entire experiment, and no stimulation was performed in the control session. In other two sessions, dogs were fed with solid meal at the beginning of the experiment; glucagon (0.1 mg kg1) was injected 20 min after feeding, SIES was initiated at the same time for 20 min followed by 20 min recovery period. The stimulus was composed of train of pulses with on-time of 0.5 s, frequency of 20 Hz, pulse width of 2 ms and amplitude of 4 mA. Results:, 1). In the fasting state, SIES induced small intestinal contractions during phase I. The motility index was 5.2 ± 0.6 in the control session and significantly increased to 10.3 ± 0.7 with SIES (P = 0.003). 2). In the fed state, glucagon substantially and significantly inhibited small intestinal motility. The motility index was 11.3 ± 0.7 after feeding and reduced to 3.4 ± 0.5 with glucagon injection (P < 0.001). SIES significantly enhanced glucagon-induced small intestinal postprandial hypomotility. The motility index was 3.4 ± 0.5 in the control session and increased to 6.0 ± 0.3 with the presence of SIES (P = 0.03). Conclusions:, Intestinal electrical stimulation synchronized with intestinal slow waves induces intestinal contractions during phase I and enhanced small intestinal postprandial hypomotility induced by glucagon. SIES may have the therapeutic potential for treating small intestinal motility disorders. (Supported by a grant from American Diabetes Association). [source] Comparison of the experience with acute and chronic electrically stimulated detrusor myoplasty,NEUROUROLOGY AND URODYNAMICS, Issue 5 2002John G. Van Savage Abstract Aims To evaluate the acute and chronic urodynamic effects of electrically stimulated detrusor myoplasty in dogs. Methods Eight female mongrel dogs were studied acutely and six dogs chronically (0 to 12 weeks postoperatively). Bladders were wrapped with the rectus abdominis muscle, keeping an intact blood supply and at least two intercostal nerves of the flap preserved. Bladders were electrically stimulated with bipolar electrodes inserted into the muscle. Urodynamics and post void residual were measured post operatively in the acute studies and every 2 weeks for 3 months in chronic studies. Results Acutely, the increase in intravesical pressure was 45±7 cm H2O, which resulted in a postvoid residual of 26±3%. In the chronic study, increases of intravesical pressure sufficient to empty the bladder during myoplasty electrical stimulation were not sustained, although detrusor compliance and flap viability were preserved. Conclusions The electrically stimulated detrusor myoplasty worked well acutely to increase vesical pressure sufficient to empty the bladder, but the chronically stimulated myoplasty did not maintain efficient bladder emptying primarily due to electrode problems. Further studies with improved electrode material and placement are required before clinical application of the electrically stimulated detrusor myoplasty can be assessed. Neurourol. Urodynam. 21:516,521, 2002. © Wiley-Liss, Inc. [source] | ||||||||||