scholarly journals MODELING OF ICRH SLOW WAVE PROPAGATION AND ABSORPTION IN WENDELSTEIN 7-X STELLARATOR

2021 ◽  
pp. 41-45
Author(s):  
D. Grekov ◽  
Yu. Turkin
Keyword(s):  
Wave Propagation ◽  
Ray Tracing ◽  
Slow Wave ◽  
Strong Influence ◽  
Slow Waves ◽  
Potential Difference ◽  
Magnetic Configuration ◽  
Standard Configuration ◽  
Lower Mirror ◽  
Qualitative Picture

The propagation and absorption of slow waves in the plasma of the Wendelstein 7-X stellarator was investigated by the ray tracing. The aim of the work was to obtain a qualitative picture of the penetration into the plasma of a wave excited by the potential difference between the antenna conductors and the antenna box. For this, a ray code was used, which performs calculations in the magnetic configuration of the stellarator obtained by the VMEC code. A strong influence of the type of magnetic configuration (“higher mirror”, “lower mirror”, or standard configuration) on the propagation and absorption of a slow wave was found.

scholarly journals Abnormal gastric slow waves in patients with functional dyspepsia assessed by multichannel electrogastrography

2001 ◽  
Vol 280 (6) ◽  
pp. G1370-G1375 ◽  
Author(s):  
Xuemei Lin ◽  
Jiande Z. Chen
Keyword(s):  
Wave Propagation ◽  
Functional Dyspepsia ◽  
Slow Wave ◽  
Single Channel ◽  
Slow Waves ◽  
Lower Percentage ◽  
Healthy Controls ◽  
Fasting State ◽  
Gastric Slow Wave ◽  
Gastric Slow Waves

The aim of this study was to utilize multichannel electrogastrography to investigate whether patients with functional dyspepsia had impaired propagation or coordination of gastric slow waves in the fasting state compared with healthy controls. The study was performed in 10 patients with functional dyspepsia and 11 healthy subjects. Gastric myoelectrical activity was measured by using surface electrogastrography with a specially designed four-channel device. The study was performed for 30 min or more in the fasting state. Special computer programs were developed for the computation of the propagation and coupling of the gastric slow wave. It was found that, compared with the healthy controls, the patients showed a significantly lower percentage of slow wave propagation (58.0 ± 8.9 vs. 89.9 ± 2.6%, P < 0.002) and a significantly lower percentage of slow wave coupling (46.9 ± 4.4 vs. 61.5 ± 6.9%, P < 0.04). In addition, the patients showed inconsistencies in the frequency and regularity of the gastric slow wave among the four-channel electrogastrograms (EGGs). It was concluded that patients with functional dyspepsia have impaired slow wave propagation and coupling. Multichannel EGG has more information than single-channel EGG for the detection of gastric myoelectrical abnormalities.

Slow waves actively propagate at submucosal surface of circular layer in canine colon

1990 ◽  
Vol 259 (2) ◽  
pp. G258-G263 ◽  
Author(s):  
K. M. Sanders ◽  
R. Stevens ◽  
E. Burke ◽  
S. W. Ward
Keyword(s):  
Wave Propagation ◽  
Slow Wave ◽  
Proximal Colon ◽  
Slow Waves ◽  
Pacemaker Cells ◽  
Transverse Axis ◽  
Active Mechanism ◽  
Conduction Velocities ◽  
Circular Layer ◽  
Thin Band

Colonic slow waves originate from pacemaker cells along the submucosal surface of the circular layer in the dog proximal colon. These events propagate in a nonregenerative manner into the bulk of the circular layer. Conduction velocities consistent with an active mechanism for slow-wave propagation in the longitudinal and circumferential axes of the colon have been reported. Experiments were performed using intracellular recording techniques on canine colonic muscles to determine the regenerative pathway for slow-wave propagation. In a thin band of muscle adjacent to the submucosal border of the circular layer, slow-wave amplitude was independent of distance from a pacing source, and events propagated at a rate of approximately 17 mm/s in the long axis of the circular fibers and 6 mm/s in the transverse axis of the circular fibers. These findings suggest that slow waves propagate in a regenerative manner in this region. Slow waves decayed as they conducted through regions from which the pacemaker cells had been removed with space constants of a few millimeters. Thus the integrity of the thin pacemaker region along submucosal surface is critical for propagation of slow waves and the organization of motility into segmental contractions.

scholarly journals High-resolution mapping of gastric slow-wave recovery profiles: biophysical model, methodology, and demonstration of applications

2017 ◽  
Vol 313 (3) ◽  
pp. G265-G276 ◽  
Author(s):  
N. Paskaranandavadivel ◽  
L. K. Cheng ◽  
P. Du ◽  
J. M. Rogers ◽  
G. O’Grady
Keyword(s):  
Wave Propagation ◽  
Wavelet Transform ◽  
High Resolution ◽  
Slow Wave ◽  
Recovery Phase ◽  
Slow Waves ◽  
Gastric Slow Wave ◽  
High Resolution Mapping ◽  
Resolution Mapping ◽  
Extracellular Potentials

Slow waves play a central role in coordinating gastric motor activity. High-resolution mapping of extracellular potentials from the stomach provides spatiotemporal detail on normal and dysrhythmic slow-wave patterns. All mapping studies to date have focused exclusively on tissue activation; however, the recovery phase contains vital information on repolarization heterogeneity, the excitable gap, and refractory tail interactions but has not been investigated. Here, we report a method to identify the recovery phase in slow-wave mapping data. We first developed a mathematical model of unipolar extracellular potentials that result from slow-wave propagation. These simulations showed that tissue repolarization in such a signal is defined by the steepest upstroke beyond the activation phase (activation was defined by accepted convention as the steepest downstroke). Next, we mapped slow-wave propagation in anesthetized pigs by recording unipolar extracellular potentials from a high-resolution array of electrodes on the serosal surface. Following the simulation result, a wavelet transform technique was applied to detect repolarization in each signal by finding the maximum positive slope beyond activation. Activation-recovery (ARi) and recovery-activation (RAi) intervals were then computed. We hypothesized that these measurements of recovery profile would differ for slow waves recorded during normal and spatially dysrhythmic propagation. We found that the ARi of normal activity was greater than dysrhythmic activity (5.1 ± 0.8 vs. 3.8 ± 0.7 s; P < 0.05), whereas RAi was lower (9.7 ± 1.3 vs. 12.2 ± 2.5 s; P < 0.05). During normal propagation, RAi and ARi were linearly related with negative unit slope indicating entrainment of the entire mapped region. This relationship was weakened during dysrhythmia (slope: −0.96 ± 0.2 vs −0.71 ± 0.3; P < 0.05). NEW & NOTEWORTHY The theoretical basis of the extracellular gastric slow-wave recovery phase was defined using mathematical modeling. A novel technique utilizing the wavelet transform was developed and validated to detect the extracellular slow-wave recovery phase. In dysrhythmic wavefronts, the activation-to-recovery interval (ARi) was shorter and recovery-to-activation interval (RAi) was longer compared with normal wavefronts. During normal activation, RAi vs. ARi had a slope of −1, whereas the weakening of the slope indicated a dysrhythmic propagation.

Relationship between transmural potential difference and smooth muscle slow waves and contractility in the rabbit small intestine in vitro

1988 ◽  
Vol 66 (9) ◽  
pp. 1161-1165 ◽  
Author(s):  
Beverley Greenwood ◽  
Jan D. Huizinga ◽  
Edwin Chow ◽  
Wylie J. Dodds
Keyword(s):  
Smooth Muscle ◽  
Electrical Activity ◽  
Slow Wave ◽  
Muscle Activity ◽  
Slow Waves ◽  
Potential Difference ◽  
Intraluminal Pressure ◽  
Mechanical Activity ◽  
Rabbit Ileum

The relationship between transmural potential difference (PD) and smooth muscle electrical and mechanical activity was investigated in the rabbit ileum in vitro. Transmural PD was monitored using agar salt bridge electrodes connected via calomel half cells to an electrometer. Force displacement transducers recorded predominantly longitudinal smooth muscle activity. Concurrently, predominantly circular muscle activity was recorded at three sites using intraluminal pressure probes. At the same sites, suction electrodes monitored electrical activity of the smooth muscle. In all experiments, fluctuations in transmural PD were temporally linked to smooth muscle mechanical and electrical activity. The frequency of PD oscillations, electrical slow waves, and cyclic pressure changes were identical within each segment. Adrenaline abolished smooth muscle electrical spiking, all mechanical activity, and transmural fluctuations in PD. However, the slow waves were not abolished, though their frequency was increased. Phentolamine but not propranolol reversed the effects of adrenaline, thus slow wave frequency is influenced by α-adrenergic stimulation in the rabbit ileum. In conclusion, oscillations in transmural PD are unrelated to the ionic processes associated with the slow wave. However, they are in some way linked to smooth muscle contractile activity, possibly via an intrinsic neural mechanism as observed in the guinea pig.

Peripheral pacemakers and patterns of slow wave propagation in the canine small intestine in vivo

2005 ◽  
Vol 83 (11) ◽  
pp. 1031-1043 ◽  
Author(s):  
Wim J.E.P Lammers ◽  
Luc Ver Donck ◽  
Jan A.J Schuurkes ◽  
Betty Stephen
Keyword(s):  
Wave Propagation ◽  
Small Intestine ◽  
Slow Wave ◽  
Electrode Array ◽  
Canine Model ◽  
Slow Waves ◽  
Velocity Amplitude ◽  
Local Site ◽  
Propagation Pattern

In an anesthetized, open-abdomen, canine model, the propagation pattern of the slow wave and its direction, velocity, amplitude, and frequency were investigated in the small intestine of 8 dogs. Electrical recordings were made using a 240-electrode array from 5 different sites, spanning the length of the small intestine. The majority of slow waves propagated uniformly and aborally (84%). In several cases, however, other patterns were found including propagation in the oral direction (11%) and propagation block (2%). In addition, in 69 cases (3%), a slow wave was initiated at a local site beneath the electrode array. Such peripheral pacemakers were found throughout the entire intestine. The frequency, velocity, and amplitude of slow waves were highest in the duodenum and gradually declined along the intestine reaching lowest values in the distal ileum (from 17.4 ± 1.7 c/min to 12.2 ± 0.7 c/min; 10.5 ± 2.4 cm/s to 0.8 ± 0.2 cm/s, and 1.20 ± 0.35 mV to 0.31 ± 0.10 mV, respectively; all p < 0.001). Consequently, the wavelength of the slow wave was strongly reduced from 36.4 ± 0.8 cm to 3.7 ± 0.1 cm (p < 0.001). We conclude that the patterns of slow wave propagation are usually, though not always, uniform in the canine small intestine and that the gradient in the wavelength will influence the patterns of local contractions.Key words: slow waves, conduction velocity, peripheral pacemakers, wavelength.

scholarly journals Integrity of corpus callosum is essential for the cross-hemispheric propagation of sleep slow waves: a high-density EEG study in split-brain patients

2019 ◽  
Author(s):  
Giulia Avvenuti ◽  
Giacomo Handjaras ◽  
Monica Betta ◽  
Jacinthe Cataldi ◽  
Laura Sophie Imperatori ◽  
...  
Keyword(s):  
Wave Propagation ◽  
White Matter ◽  
Corpus Callosum ◽  
Slow Wave ◽  
Nrem Sleep ◽  
High Density ◽  
Slow Waves ◽  
Wave Parameter ◽  
P Value ◽  
The Cross

AbstractThe slow waves of NREM-sleep (0.5-4Hz) reflect experience-dependent plasticity and play a direct role in the restorative functions of sleep. Importantly, slow waves behave as traveling waves and their propagation is assumed to reflect the structural properties of white matter connections. Based on this assumption, the corpus callosum (CC) may represent the main responsible for cross-hemispheric slow wave propagation. To verify this hypothesis, here we studied a group of patients who underwent total callosotomy due to drug-resistant epilepsy. Overnight high-density (hd)-EEG recordings (256 electrodes) were performed in five totally callosotomized in-patients (CP; 40-53y, 2F), in three control non-callosotomized neurological in-patients (NP; 44-66y, 2F, 1M epileptic), and in an additional sample of 24 healthy adult subjects (HS; 20-47y, 13F). Data were inspected to select NREM-sleep epochs and artefactual or non-physiological activity was rejected. Slow waves were detected using an automated algorithm and their properties and propagation patterns were computed. For each slow wave parameter and for each patient, the relative z-score and the corresponding p-value were calculated with respect to the distribution represented by the HS-group. Group differences were considered significant only when a Bonferroni corrected P < 0.05 was observed in all the CP and in none of the NP. A regression-based adjustment was used to exclude potential confounding effects of age. Slow wave density, amplitude, slope and propagation speed did not differ across CP and HS. In all CP slow waves displayed a significantly reduced probability of cross-hemispheric propagation and a stronger inter-hemispheric asymmetry. Moreover, we found that the incidence of large slow waves tended to differ across hemispheres within individual NREM epochs, with a relative predominance of the right over the left hemisphere in both CP and HS. The absolute magnitude of this inter-hemispheric difference was significantly greater in CP relative to HS. This effect did not depend on differences in slow wave origin within each hemisphere across groups. Present results indicate that the integrity of the CC is essential for the cross-hemispheric traveling of sleep slow waves, supporting the assumption of a direct relationship between white matter structural integrity and cross-hemispheric slow wave propagation. Our findings also imply a prominent role of cortico-cortical connections, rather than cortico-subcortico-cortical loops, in slow wave cross-hemispheric synchronization. Finally, this data indicate that the lack of the CC does not lead to differences in sleep depth, in terms of slow wave generation/origin, across brain hemispheres.

Origin and spread of slow waves in canine gastric antral circular muscle

1985 ◽  
Vol 249 (6) ◽  
pp. G800-G806 ◽  
Author(s):  
A. J. Bauer ◽  
N. G. Publicover ◽  
K. M. Sanders
Keyword(s):  
Wave Propagation ◽  
Slow Wave ◽  
Myenteric Plexus ◽  
Circular Muscle ◽  
Slow Waves ◽  
Three Dimensions ◽  
Muscle Strip ◽  
Velocity Measurements ◽  
Conduction Velocities ◽  
Axis Parallel

Electrical slow waves recorded from circular muscle cells near the myenteric and submucosal plexuses were found to be significantly different. By measuring the latencies between the arrival of evoked events at two recording sites, slow wave conduction velocities were determined in the three dimensions of circular muscle. Slow waves propagated more rapidly in the axis parallel to the circular fibers than in the axes perpendicular to the circular fibers. The rates of slow wave propagation were also determined in axes parallel and perpendicular to fibers in myenteric and submucosal circular muscles. Slow waves conducted more slowly in the circular muscle near the submucosa than in circular muscle near the myenteric plexus. From conduction velocity measurements, a technique was developed to determine the pacemaker site of spontaneous slow waves in a muscle strip. These data demonstrate that slow waves originate from multiple discrete foci; in muscle strips cut along the long axis of the stomach, these foci are found predominantly in the orad region of the muscle strip; and slow waves originate in the outer myenteric half of the muscle.

Voltage-gated Ca2+ currents are necessary for slow-wave propagation in the canine gastric antrum

2007 ◽  
Vol 293 (5) ◽  
pp. C1645-C1659 ◽  
Author(s):  
Orline Bayguinov ◽  
Sean M. Ward ◽  
James L. Kenyon ◽  
Kenton M. Sanders
Keyword(s):  
Wave Propagation ◽  
Slow Wave ◽  
Propagation Velocity ◽  
Circular Muscle ◽  
Slow Waves ◽  
Dependent Manner ◽  
Voltage Dependent ◽  
Lesser Curvature ◽  
Propagation Velocities ◽  
Upstroke Velocity

Electrical slow waves determine the timing and force of peristaltic contractions in the stomach. Slow waves originate from a dominant pacemaker in the orad corpus and propagate actively around and down the stomach to the pylorus. The mechanism of slow-wave propagation is controversial. We tested whether Ca2+ entry via a voltage-dependent, dihydropyridine-resistant Ca2+ conductance is necessary for active propagation in canine gastric antral muscles. Muscle strips cut parallel to the circular muscle were studied with intracellular electrophysiological techniques using a partitioned-chamber apparatus. Slow-wave upstroke velocity and plateau amplitude decreased from the greater to the lesser curvature, and this corresponded to a decrease in the density of interstitial cells of Cajal in the lesser curvature. Slow-wave propagation velocity between electrodes impaling cells in two regions of muscle and slow-wave upstroke and plateau were measured in response to experimental conditions that reduce the driving force for Ca2+ entry or block voltage-dependent Ca2+ currents. Nicardipine (0.1–1 μM) did not affect slow-wave upstroke or propagation velocities. Upstroke velocity, amplitude, and propagation velocity were reduced in a concentration-dependent manner by Ni2+ (1–100 μM), mibefradil (10–30 μM), and reduced extracellular Ca2+ (0.5–1.5 mM). Depolarization (by 10–15 mM K+) or hyperpolarization (10 μM pinacidil) also reduced upstroke and propagation velocities. The higher concentrations (or lowest Ca2+) of these drugs and ionic conditions tested blocked slow-wave propagation. Treatment with cyclopiazonic acid to empty Ca2+ stores did not affect propagation. These experiments show that voltage-dependent Ca2+ entry is obligatory for the upstroke phase of slow waves and active propagation.

Pathways of slow-wave propagation in proximal colon of cats

1990 ◽  
Vol 258 (6) ◽  
pp. G894-G903 ◽  
Author(s):  
J. L. Conklin ◽  
C. Du
Keyword(s):  
Wave Propagation ◽  
Smooth Muscle ◽  
Slow Wave ◽  
Interstitial Cells Of Cajal ◽  
Muscularis Propria ◽  
Interstitial Cells ◽  
Proximal Colon ◽  
Slow Waves ◽  
Cells Of Cajal ◽  
Circular Axis

Colonic slow waves (SWs) are generated by nonneuronal cells located at the interface of the submucosa and muscularis propria. It has been proposed that SWs arise from a complex of nerves, interstitial cells of Cajal, and smooth muscle found at this location. These experiments test the hypothesis that the propagation of colonic SWs depends on an intact interface between the submucosa and muscularis propria. The electromyogram was recorded from segments of the proximal colon of the cat. All intact tissues generated SWs that propagated in the long and circumferential axes of the colon. Tetrodotoxin did not disrupt SW propagation in either axis. Transection of tissues between recording sites interrupted the spread of SWs in both axes. Transection of the submucosa disrupted the longitudinal spread of SWs, whereas transection of the muscularis propria did not. Removing the submucosa from the midportion of tissue segments oriented in the long axis of the colon resulted in a loss of SWs from the segment devoid of submucosa. Transection of the submucosa of tissue segments oriented in the circular axis of the colon did not disrupt circumferential propagation of SWs. Dissecting a 1-cm-wide segment of submucosa from the midportion of such a circularly oriented tissue did not disrupt the circumferential spread of SWs, and SWs were recorded from the muscle segment that was devoid of submucosa. SWs were not recorded from the segment devoid of submucosa when it was isolated from adjacent intact segments. The data support the hypothesis that the regeneration of SWs during their longitudinal propagation takes place at the interface between the submucosa and muscularis propria.

Origin and propagation of the slow wave in the canine stomach: the outlines of a gastric conduction system

2009 ◽  
Vol 296 (6) ◽  
pp. G1200-G1210 ◽  
Author(s):  
Wim J. E. P. Lammers ◽  
Luc Ver Donck ◽  
Betty Stephen ◽  
Dirk Smets ◽  
Jan A. J. Schuurkes
Keyword(s):  
Wave Propagation ◽  
Slow Wave ◽  
Ventral Surface ◽  
High Amplitude ◽  
Conduction System ◽  
Slow Waves ◽  
Low Velocity ◽  
Anesthetized Dogs ◽  
Greater Curvature ◽  
Low Amplitude

Slow waves are known to originate orally in the stomach and to propagate toward the antrum, but the exact location of the pacemaker and the precise pattern of propagation have not yet been studied. Using assemblies of 240 extracellular electrodes, simultaneous recordings of electrical activity were made on the fundus, corpus, and antrum in open abdominal anesthetized dogs. The signals were analyzed off-line, pathways of slow wave propagation were reconstructed, and slow wave velocities and amplitudes were measured. The gastric pacemaker is located in the upper part of the fundus, along the greater curvature. Extracellularly recorded slow waves in the pacemaker area exhibited large amplitudes (1.8 ± 1.0 mV) and rapid velocities (1.5 ± 0.9 cm/s), whereas propagation in the remainder of the fundus and in the corpus was slow (0.5 ± 0.2 cm/s) with low-amplitude waveforms (0.8 ± 0.5 mV). In the antrum, slow wave propagation was fast (1.5 ± 0.6 cm/s) with large amplitude deflections (2.0 ± 1.3 mV). Two areas were identified where slow waves did not propagate, the first in the oral medial fundus and the second distal in the antrum. Finally, recordings from the entire ventral surface revealed the presence of three to five simultaneously propagating slow waves. High resolution mapping of the origin and propagation of the slow wave in the canine stomach revealed areas of high amplitude and rapid velocity, areas with fractionated low amplitude and low velocity, and areas with no propagation; all these components together constitute the elements of a gastric conduction system.

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