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Wave Activity (wave + activity)
Kinds of Wave Activity Selected AbstractsSpatiotemporal changes of slow wave activities before and after 14 Hz/12 Hz sleep spindles during stage 2 sleepPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 3 2001Kazutaka Ueda Abstract The present study examined the spatiotemporal changes of slow wave (delta and theta bands) activities before and after 14 Hz/12 Hz sleep spindles during stage 2 sleep, using topographic mapping of electroencephalogram (EEG) power. Both types of sleep spindles appeared after slow wave activities of background EEG decreased. Moreover, the appearance of sleep spindles provided increasing EEG slow wave activities in the subsequent period. Further, the present results showed that an appearance of 14 Hz sleep spindle facilitated slow wave activities at the centro-parietal areas, while an appearance of 12 Hz sleep spindle facilitated slow wave activities at the fronto-central areas. These results suggest that sleep spindles provide cortical de-arousal, and serve to maintain sleep. [source] Switching of the transmitters that mediate hindbrain correlated activity in the chick embryoEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2009Hiraku Mochida Abstract Widely propagating correlated neuronal activity is a hallmark of the developing nervous system. The activity is usually mediated by multiple transmitters, and the contribution of gap junctions has also been suggested in several systems. In some structures, such as the retina and spinal cord, it has been shown that the dominant transmitter mediating the correlated wave switches from acetylcholine to glutamate during development, although the functional significance of this phenomenon has not been clarified. An important question is whether such a transmitter switch occurs in other systems, especially in the brain. In the present study, we demonstrate that the major transmitter mediating correlated wave activity in the embryonic chick hindbrain changes from acetylcholine/,-aminobutyric acid (GABA)/glycine to glutamate/GABA as development proceeds. The results show for the first time that the dominant transmitter switches from acetylcholine to glutamate in a region other than the retina and spinal cord. This finding sheds more light on the role of nicotinic acetylcholine receptors in the generation of correlated wave activity, which is considered to regulate the development of the nervous system. [source] Multiscale modelling of human gastric electric activity: can the electrogastrogram detect functional electrical uncoupling?EXPERIMENTAL PHYSIOLOGY, Issue 2 2006M. L. Buist During recent years there has been a growing interest in the assessment of gastric electrical health through cutaneous abdominal recordings. The analysis of such recordings is largely limited to an inspection of frequency dynamics, and this has raised doubts as to whether functional gastric electrical uncoupling can be detected using this technique. We describe here a computational approach to the problem in which the equations governing the underlying physics of the problem have been solved over an anatomically detailed human torso geometry. Cellular electrical activity was embedded within a stomach tissue model, and this was coupled to the torso using an equivalent current source approach. Simulations were performed in which normal and functionally uncoupled (through the introduction of an ectopic antral pacemaker) gastric slow wave activity was present, and corresponding cutaneous electrogastrograms were produced. These were subsequently analysed using the currently recommended techniques, and it was found that the functionally uncoupled situation was indistinguishable from normal slow wave activity using this approach. [source] Low-frequency passive seismic experiments in Abu Dhabi, United Arab Emirates: implications for hydrocarbon detectionGEOPHYSICAL PROSPECTING, Issue 5 2010Mohammed Y. Ali ABSTRACT Low-frequency passive seismic experiments utilizing arrays of 3-component broadband seismometers were conducted over two sites in the emirate of Abu Dhabi in the United Arab Emirates. The experiments were conducted in the vicinity of a producing oilfield and around a dry exploration well to better understand the characteristics and origins of microtremor signals (1,6 Hz), which had been reported as occurring exclusively above several hydrocarbon reservoirs in the region. The results of the experiments revealed that a strong correlation exists between the recorded ambient noise and observed meteorological and anthropogenic noises. In the frequency range of 0.15,0.4 Hz, the dominant feature is a double-frequency microseism peak generated by the non-linear interactions of storm induced surface waves in the Arabian Sea. We observed that the double-frequency microseism displays a high variability in spectral amplitude, with the strongest amplitude occurring when Cyclone Gonu was battering the eastern coast of Oman; this noise was present at both sites and so is not a hydrocarbon indicator. Moreover, this study found that very strong microtremor signals in the frequency range of 2,3 Hz were present in all of the locations surveyed, both within and outside of the reservoir boundary and surrounding the dry exploration well. This microtremor signal has no clear correlation with the microseism signals but significant variations in the characteristics of the signals were observed between daytime and nighttime recording periods that clearly correlate with human activity. High-resolution frequency-wavenumber (f - k) spectral analyses were performed on the recorded data to determine apparent velocities and azimuths of the wavefronts for the microseism and microtremor events. The f - k analyses confirmed that the double-frequency microseism originates from wave activity in the Arabian Sea, while the microtremor events have an azimuth pointing towards the nearest motorways, indicating that they are probably being excited by traffic noise. Results drawn from particle motion studies confirm these observations. The vertical-to-horizontal spectral ratios of the data acquired in both experiments show peaks around 2.5,3 Hz with no dependence on the presence or absence of subsurface hydrocarbons. Therefore, this method should not be used as a direct hydrocarbon indicator in these environments. Furthermore, the analyses provide no direct evidence to indicate that earthquakes are capable of stimulating the hydrocarbon reservoir in a way that could modify the spectral amplitude of the microtremor signal. [source] Effects of audio stimulation on gastric myoelectrical activity and sympathovagal balance in healthy adolescents and adultsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 1 2008Dennis D Chen Abstract Aim:, The primary aim of this study was to investigate the effects of different audio stimulations on gastric myoelectrical activity and sympathovagal balance in adolescents compared with adults. Methods:, The study was performed in 11 adults and 12 adolescents. Each subject underwent two sessions, one for classical music, and the other for noise. Each session consisted of 30 min of baseline, 30 min of fasting audio stimulation, a test meal, 30 min of fed audio stimulation, and 30 min of recovery. Electrocardiogram and electrogastrogram were both recorded throughout each session. Results:, (i) In the fasting state, both classical music and noise impaired gastric slow wave activity in adolescents. In adults, noise had no effects while classical music moderately improved slow wave rhythmicity. (ii) In the fed state, neither noise nor music had any effects on gastric slow waves. (iii) In the fasting state, both noise and music increased the sympathovagal balance in adolescents; in adults only noise had such an effect. (iv) The test meal increased the sympathovagal balance in all groups. Conclusions:, Gastric slow waves and the sympathovagal balance are more strongly affected by audio stimulation in adolescents than in adults. The test meal normalizes the audio stimulation-induced differences between the groups. [source] Multi-sensor synthesis of the mesoscale structure of a cold-air comma cloud systemMETEOROLOGICAL APPLICATIONS, Issue 2 2002K A Browning A multiscale study of a cold-air comma cloud that produced an area of heavy rain and locally severe weather has been undertaken by synthesising data from a research microwave Doppler radar and VHF and UHF Doppler wind profilers, along with routinely available radar-network, satellite, in situ and mesoscale-model data. The rain area was generated in the exit region of an upper-level jet characterised by laminated velocity perturbations. Some of the perturbations were attributable to inertia-gravity wave activity. The rain area itself is shown to have been composed of a well-organised set of mesoscale rainbands each being due to a mixture of upright and slantwise convection. The existence of the multiple rainbands may have been related to the multi-layered atmospheric structure upwind. Each of the rainbands had cold-frontal and warm-frontal portions, so as to form a series of mini warm sectors stacked along the axis of the comma cloud at roughly 70 km intervals. The multiple rainbands were accompanied by multiple fingers of overrunning low-,w air from part of a dry intrusion originating from just below a major tropopause fold. The fold contained an intense potential-vorticity maximum which appeared to be the focus of the overall system. The operational mesoscale version of the Met. Office's Unified Model, with its 12 km grid, is shown to have resolved many but not all of the key features of the rainbands. It is suggested that further improvements in very-short-range forecasting of important local detail could be achieved by further increasing its resolution and assimilating more mesoscale observational data. Copyright © 2002 Royal Meteorological Society [source] Effects of imatinib mesylate (Glivec®) as a c-kit tyrosine kinase inhibitor in the guinea-pig urinary bladderNEUROUROLOGY AND URODYNAMICS, Issue 3 2006Yasue Kubota Abstract Aims In the gastrointestinal tract, slow wave activity in smooth muscle is generated by the interstitial cells of Cajal (ICC). Detrusor smooth muscle strips of most species show spontaneous contractions which are triggered by action potential bursts, however, the pacemaker mechanisms for the detrusor are still unknown. Recently, ICC-like cells have been found in guinea-pig bladder, using antibodies to the c-kit receptor. We have investigated the effects of Glivec, a c-kit tyrosine kinase inhibitor, on spontaneous action potentials in guinea-pig detrusor and intravesical pressure of isolated guinea-pig bladders. Methods Changes in the membrane potential were measured in guinea-pig detrusor smooth muscle using conventional microelectrode techniques. Pressure changes in the bladder were recorded using whole organ bath techniques. Results Smooth muscle cells in detrusor muscle bundles exhibited spontaneous action potentials, and spontaneous pressure rises occurred in isolated bladders. Glivec (10 ,M) converted action potential bursts into continuous firing with no effects on the shape of individual action potentials. Glivec (>50 ,M) reduced the amplitude of spontaneous pressure rises in the whole bladder in a dose dependent manner and abolished spontaneous action potentials in detrusor smooth muscle cells. Conclusions The results suggest that ICC-like cells may be responsible for generating bursts of action potentials and contractions in detrusor smooth muscle. Drugs inhibiting the c-kit receptor may prove useful for treating the overactive bladder. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc. [source] The Chinese herbal preparation Qing Yi Tang (QYT) improves intestinal myoelectrical activity and Increases intestinal transit during acute pancreatitis in RodentsPHYTOTHERAPY RESEARCH, Issue 4 2007Yong-Yu Li Abstract The aim was to investigate alterations of intestinal motility in models of acute pancreatitis and to investigate the effects of the Chinese herbal preparation Qing Yi Tang (QYT) on these alterations. Upper gastrointestinal transit was evaluated in mice following induction of mild acute pancreatitis (MAP) using caerulein. Myoelectrical activity was recorded in rats after induction of severe acute pancreatitis (SAP) using sodium deoxycholate (SDOC). The contractility of jejunum segments was evaluated in the presence of SDOC, lipopolysaccharide (LPS) and trypsin. QYT accelerated the transit in MAP mice in a concentration dependent manner. Slow wave activity of smooth muscle in rat stomach and jejunum remained unchanged following SAP, but the spiking activity was significantly decreased, with bursts of 7.2 ± 2.6/10 min compared with 47.9 ± 13.2/10 min without SAP (p < 0.01). QYT reversed this decrease. Additionally, the amplitudes of slow waves and spikes were enhanced by QYT in SAP rats. The tension and amplitude of spontaneous contractile activity was reduced by SDOC and LPS and increased by trypsin. Gastrointestinal (GI) transit is altered by SAP but not by MAP. The Chinese herbal preparation QYT improves disturbed motility in AP by stimulating myoelectrical activity and accelerating GI transit. Copyright © 2007 John Wiley & Sons, Ltd. [source] The first intestinal motility patterns in fetal mice are not mediated by neurons or interstitial cells of CajalTHE JOURNAL OF PHYSIOLOGY, Issue 7 2010Rachael R. Roberts In mature animals, neurons and interstitial cells of Cajal (ICC) are essential for organized intestinal motility. We investigated motility patterns, and the roles of neurons and myenteric ICC (ICC-MP), in the duodenum and colon of developing mice in vitro. Spatiotemporal mapping revealed regular contractions that propagated in both directions from embryonic day (E)13.5 in the duodenum and E14.5 in the colon. The propagating contractions, which we termed ripples, were unaffected by tetrodotoxin and were present in the intestine of embryonic Ret null mutant mice, which lack enteric neurons. Neurally mediated motility patterns were first observed in the duodenum at E18.5. To examine the possible role of ICC-MP, three approaches were used. First, intracellular recordings from the circular muscle of the duodenum did not detect slow wave activity at E16.5, but regular slow waves were observed in some preparations of E18.5 duodenum. Second, spatiotemporal mapping revealed ripples in the duodenum of E13.5 and E16.5 W/Wv embryos, which lack KIT+ ICC-MP and slow waves. Third, KIT-immunoreactive cells with the morphology of ICC-MP were first observed at E18.5. Hence, ripples do not appear to be mediated by ICC-MP and must be myogenic. Ripples in the duodenum and colon were abolished by cobalt chloride (1 mm). The L-type Ca2+ channel antagonist nicardipine (2.5 ,m) abolished ripples in the duodenum and reduced their frequency and size in the colon. Our findings demonstrate that prominent propagating contractions (ripples) are present in the duodenum and colon of fetal mice. Ripples are not mediated by neurons or ICC-MP, but entry of extracellular Ca2+ through L-type Ca2+ channels is essential. Thus, during development of the intestine, the first motor patterns to develop are myogenic. [source] | ||||||||||||||||