Electrical Control Activity Research Articles

Design and curative effect of Embedded Intelligent External Neural Pacemaker for Prostate

Aiming at the problem of extracorporeal treatment of prostate diseases, an embedded intelligent prostate extracorporeal nerve pacemaker has been designed using smart chips through the principle of digital signal generator. The treatment effect has been tested through the experiment on 22 related patients in the urology department. Experimental results show that the device can accurately simulate a variety of neural signals and the frequency and amplitude of which are adjustable. The performance of the device can be considered as stable and reliable. In particular, it can generate bioelectrical signals which are similar to the basic electrical rhythm of a normal human prostate, so that the bioelectrical activity of prostate pacemaker can return to normal rhythm. The treatment has achieved good auxiliary treatment effects. The device provides a new solution for the auxiliary treatment of prostate diseases.

Phase-locking of resting-state brain networks with the gastric basal electrical rhythm

A network of myenteric interstitial cells of Cajal in the corpus of the stomach serves as its “pacemaker”, continuously generating a ca 0.05 Hz electrical slow wave, which is transmitted to the brain chiefly by vagal afferents. A recent study combining resting-state functional MRI (rsfMRI) with concurrent surface electrogastrography (EGG), with cutaneous electrodes placed on the epigastrium, found 12 brain regions with activity that was significantly phase-locked with this gastric basal electrical rhythm. Therefore, we asked whether fluctuations in brain resting state networks (RSNs), estimated using a spatial independent component analysis (ICA) approach, might be synchronized with the stomach. In the present study, in order to determine whether any RSNs are phase-locked with the gastric rhythm, an individual participant underwent 22 scanning sessions; in each, two 15-minute runs of concurrent EGG and rsfMRI data were acquired. EGG data from three sessions had weak gastric signals and were excluded; the other 19 sessions yielded a total of 9.5 hours of data. The rsfMRI data were analyzed using group ICA; RSN time courses were estimated; for each run, the phase-locking value (PLV) was computed between each RSN and the gastric signal. To assess statistical significance, PLVs from all pairs of “mismatched” data (EGG and rsfMRI data acquired on different days) were used as surrogate data to generate a null distribution for each RSN. Of a total of 18 RSNs, three were found to be significantly phase-locked with the basal gastric rhythm, namely, a cerebellar network, a dorsal somatosensory-motor network, and a default mode network. Disruptions to the gut-brain axis, which sustains interoceptive feedback between the central nervous system and the viscera, are thought to be involved in various disorders; manifestation of the infra-slow rhythm of the stomach in brain rsfMRI data could be useful for studies in clinical populations.

Polygonally Meshed Dipole Model Simulation of the Electrical Field Produced by the Stomach and Intestines.

Cutaneous electrogastrography (EGG) is used in clinical and physiological fields to noninvasively measure the electrical activity of the stomach and intestines. Dipole models that mathematically express the electrical field characteristics generated by the stomach and intestines have been developed to investigate the relationship between the electrical control activity (ECA) (slow waves) shown in EGG and the internal gastric electrical activity. However, these models require a mathematical description of the movement of an annular band of dipoles, which limits the shape that can be modeled. In this study, we propose a novel polygonally meshed dipole model to conveniently reproduce ECA based on the movement of the annular band in complex shapes, such as the shape of the stomach and intestines, constructed in three-dimensional (3D) space. We show that the proposed model can reproduce ECA simulation results similar to those obtained using conventional models. Moreover, we show that the proposed model can reproduce the ECA produced by a complex geometrical shape, such as the shape of the intestines. The study results indicate that ECA simulations can be conducted based on structures that more closely resemble real organs than those used in conventional dipole models, with which, because of their intrinsic construction, it would be difficult to include realistic complex shapes, using the mathematical description of the movement of an annular band of dipoles. Our findings provide a powerful new approach for computer simulations based on the electric dipole model.

Особливості періодичної активності шлунка за умов дисбалансу NO-ергічної системи

Nitric oxide is the main inhibitory mediator of the gastrointestinal smooth muscles’ relaxation which stimulates duodenal mucus and bicarbonate secretion. More recent studies have demonstrated that NO also protected the gastrointestinal tract by inhibiting gastric acid secretion. In this study we investigated gastric secretory and motor activity considering the NO imbalance condition. The experiments were carried out on male white laboratory rats (200–230 g). The control group was treated with 0.9% NaCl solution. The injections of NO donator (1.5 mg/kg of 0.1% (Sigma-Aldrich) sodium nitroprusside solution) were made in the second and the third groups during 6 and 12 days. The fourth and the fifth group were treated with NO synthesis inhibitor (40 mg/kg of 1% solution (Sigma-Aldrich) Nω-nitro-L-arginine) during 6 and 12 days respectively. Recording of gastric myoelectric activity (GMA) and gastric juice collection were carried out under anesthesia (ketamine, 110 mg/kg). Next, its volume, pH, glycoprotein and pepsin were measured. Within 6-days stimulation of NO excess decreased gastric juice volume by 47% and increased pH compared to control samples. Pepsin level increased by 62% and glycoprotein level decreased by 68% compared to the checkpoint. After 6 days of L-NNA injections we observed the increase of gastric juice secretion volume (78%) and pH level, however, pepsin concentration remained unchanged. Glycoprotein level increased by 21% compared to control samples. After 12 day NO synthesis inhibitor injections gastric secretion volume increased by 85%. Gastric juice pH level was 200% higher than the control value and exceeded gastric juice pH level (62%) in the third group. In addition, pepsin level tended to decrease when NO deficiency simulation was prolonged. Glycoprotein level decreased by 41% compared to control samples and by 51% compared to the third group. Pepsin level decreased after 12 day NO-inhibitor injections as gastric juice pH level increased. After 12 day Na-nitroprusside treatment, gastric myoelectric index decreased by 42% compared to the checkpoint. The type of contractions is typical to the I phase of the basic electrical rhythm (BER). Also, retrograde entrainment of duodenal rhythm took place. After 6 day L-NNA injections, GMA was the same as the period between II and III phase of BER. Late second and early third phases predominated, while the I phase wasn’t detected during the recording. In case of long-lasting disorder of NO-system, motor index value significantly differed from the control group samples and depended on the duration of NO-synthase blocking. On the 6th day of L-NNA treatment, the level of motor index increased 1.5 times. GMA phases could be identified only on the basis of motor index values. Stomach’s own rhythms disappeared and duodenogastric reflux resulted in domination of duodenal rhythms. After 12 day L-NNA injections, duration of the II and III phases increased while the I phase of gastric BER disappeared; gastric motor index decreased by 27%. After considering the results of the current investigation, it can be stated that NO system imbalance leads to desynchronization of gastric active phases and, perhaps, reassigns the influence of different compensatory-adaptive mechanisms. The longer is the L-NNA treatment, the more gastric functions are imbalanced and the stronger is the process of destruction.

Current status of multichannel electrogastrography and examples of its use

Electrogastrography (EGG) is a non-invasive diagnostic motility for recording gastric myoelectrical activity. Gastric myoelectrical activity was first recorded in 1922. Advances in recording equipment enabled widespread use of cutaneous EGG after 1985. Later, introduction of multichannel EGG (M-EGG) enabled measurement of electrical activity transmission. At present, M-EGG findings are used as objective indicators of gastric motility disorders caused by various diseases. EGG measures two categories of gastric electrical activity: electrical response activity, or spike potentials; and electrical control activity, or slow waves. The appearance of abnormal rhythmic electrical activity is indicative of abnormalities in gastric motility. The normal frequency range of gastric electrical activity (normogastria) is around 3 cycles per min. Multiple EGG parameters assist in the assessment of gastric myoelectrical activity, and significant correlations between EGG and other gastric motility tests have been demonstrated in many studies. In Japan, however, EGG remains in the exploratory stage, and its clinical use is limited. There are large variations in procedures and systems used in previous studies, thus there is a need for standardization of EGG procedures and technical terminology. Here, we outline the current status of EGG and report the M-EGG procedures used in our department in addition to our M-EGG findings.The abstract of this manuscript was presented during an educational seminar titled "Current status of gastrointestinal motility tests and keys for immediate implementation" at the 54th Annual Meeting of the Japan Society of Smooth Muscle Research

Analysis of pacemaker activity in the human stomach

Extracellular electrical recording and studies using animal models have helped establish important concepts of human gastric physiology. Accepted standards include electrical quiescence in the fundus, 3 cycles per minute (cpm) pacemaker activity in corpus and antrum, and a proximal-to-distal slow wave frequency gradient. We investigated slow wave pacemaker activity, contractions and distribution of interstitial cells of Cajal (ICC) in human gastric muscles. Muscles were obtained from patients undergoing gastric resection for cancer, and the anatomical locations of each specimen were mapped by the operating surgeon to 16 standardized regions of the stomach. Electrical slow waves were recorded with intracellular microelectrodes and contractions were recorded by isometric force techniques. Slow waves were routinely recorded from gastric fundus muscles. These events had similar waveforms as slow waves in more distal regions and were coupled to phasic contractions. Gastric slow wave frequency was significantly greater than 3 cpm in all regions of the stomach. Antral slow wave frequency often exceeded the highest frequency of pacemaker activity in the corpus. Chronotropic mechanisms such as muscarinic and prostaglandin receptor binding, stretch, extracelluar Ca(2+) and temperature were unable to explain the observed slow wave frequency that exceeded accepted normal levels. Muscles from all regions through the thickness of the muscularis demonstrated intrinsic pacemaker activity, and this corresponded with the widespread distribution in ICC we mapped throughout the tunica muscularis. Our findings suggest that extracellular electrical recording has underestimated human slow wave frequency and mechanisms of human gastric function may differ from standard laboratory animal models.

Gastric motility functional study based on electrical bioimpedance measurements and simultaneous electrogastrography

For some time now, the research on gastric motility and function has fallen behind in the amount of research on gastric endocrine, exocrine secretion, and gastric morphology. In this paper, a noninvasive method to study gastric motility was developed, taking bioimpedance measurements over the gastric area simultaneously with the electrogastrography (EGG). This is based on the concept of observing and analyzing simultaneously the intrinsic electrical gastric activity (basic electric rhythm) and the mechanical gastric activity. Additionally, preliminary clinical studies of healthy subjects and subjects with functional dyspepsia (FD) and gastritis were carried out. The impedance gastric motility (IGM) measurements of the healthy and FD subjects were compared, along with the studies of the FD subjects before treatment and after one week and three weeks of treatment. We also compared IGM measurements of healthy subjects and subjects with erosive gastritis, along with the studies of the subjects with erosive gastritis before treatment and after one week of treatment. Results show that FD subjects have poor gastric motility (P<0.01). After a week of treatment, the gastric motility of FD subjects was not yet improved although the EGG had returned to normal by this time. By three weeks of treatment, the regular IGM rhythm returned in FD subjects. There was a significant difference of IGM parameters between the gastritis and healthy subjects (P<0.05). The EGG rhythm of the gastritis subjects returned to normal at one week post-treatment, while IGM parameters showed a trend to improvement (P>0.05), These results suggest the possibility of clinic application of the proposed method.

Study of the regulatory effect of acupuncture on rotation-induced gastric dysrhythmia in rabbits.

A model of experimental gastric dysrhythmia in rabbits was set up to evaluate the effect of different acupoints on regulating gastric dysrhythmia in rabbits so as to promote acupuncture treatment for this kind of disease. A model of gastric dysrhythmia in rabbits was established by the rotation method using the basic electrical rhythm (BER) as an objective index. After puncturing at the points of Zusanli (ST36), Neiguan (PC6), Tiaokou (ST38) and Tianquan (PC2) in the four groups of experimental gastric dysrhythmia rabbits, the difference in regulatory effects on the disturbance and frequency of the gastric electric slow wave was observed. Before needling at the specific acupoints Zusanli and Neiguan, the percentage of disturbance electric slow wave for the Zusanli and Neiguan groups was 57.0785 ± 10.644 and 55.5173 ± 6.0500, respectively; after such needling, the percentage was 43.7823 ± 10.1518 and 43.5147 ± 6.8983 for the Zusanli and Neiguan groups, respectively, while the frequency of electric slow wave for the Zusanli and Neiguan groups was 2.2870 ± 0.3800 and 2.4020 ± 0.3536, respectively, before needling and after needling, the frequency was 2.7090 ± 0.5865 and 2.9220 ± 0.4923 for the Zusanli and Neiguan groups, respectively. Comparing the percentage and frequency for the Zusanli and Neiguan groups before and after needling, the result shows that both groups have a significant difference statistically (P < 0.05) but between the Zusanli and Neiguan groups, there was no significant difference. Before and after needling the nonspecific acupoints of Tiaokou and Tianquan, there was no difference between the Tiaokou and Tianquan groups. Between the Zusanli and Tiaokou groups and the Neiguan and Tianquan groups, there are significant differences in regulating gastric dysrhythmia. This model is suitable for the observation of gastric dysrhythmia. The specific acupoints of Zusanli and Neiguan have good effects on the treatment of gastric dysrhythmia.

Disturbances of Gastric Electrical Control Activity after Laparotomic Cholecystectomy Are Related to Interleukin-6 Concentrations

Background: The aim of the present study was to characterize the disturbances of gastric electrical control activity after cholecystectomy and to correlate electrogastrographic (EGG) findings with inflammatory markers. Patients and Methods: 52 adult patients were examined in conjunction with planned laparotomic or laparoscopic cholecystectomy. Gastric myoelectrical activity was recorded with a MicroDigitrapper device using three Ag-AgCl disposable skin electrodes. The dominant frequency was calculated using computerized algorithms. Repeated EGG records were correlated with inflammatory parameters – interleukin-6 (IL-6), tumor necrosis factor-α, procalcitonin, and C-reactive protein. Results: Both basal and stimulated gastric electrical frequency decreased significantly in the postoperative phase measured 6 h after the start of surgery (p < 0.01). Postoperative bradygastria (electrical control activity frequency <2.4 cpm) was relatively more expressed after open cholecystectomy. Among the patients with a laparotomic cholecystectomy, IL-6 maximal postoperative concentrations correlated positively with a prolonged restitution of normal gastric activity. Conclusions: EGG examination showed a high sensitivity in the evaluation of gastric electrical activity after both laparotomic and laparoscopic cholecystectomy. A significant correlation of prolonged bradygastria and IL-6 plasma levels supports the role of the inflammatory milieu in the pathogenesis of impaired gastric electrical activity in the postoperative period.

A Barrier Kinetic Mapping Unit: Application to Ionic Transport in Gastric Smooth Muscle

A model has been developed to characterize the ionic basis of the shape of the electrical control activity (ECA) observed in gastric smooth muscle. The model uses barrier kinetics to describe the underlying ionic transport mechanisms responsible for the gastric ECA. The transmission coefficient parameter, which has been given little importance in the past, plays a major role in our model. It represents the gating and kinetics of the different channels. The model compares well with the Goldman-Hodgkin-Katz current equations for the sodium, calcium, and potassium channels. The model illustrates the importance of the calcium pump in maintaining the resting membrane potential and shows how the waveshape is influenced by the ratio of free to total intracellular calcium concentration. The effects of potassium accumulation and calcium on the waveform were also investigated. In the fundus of the stomach, where there are no voltage oscillations, the potassium channels were found to be more important than the other channels in maintaining the resting membrane potential.

Effects of Enteral and Parenteral Nutrition on Gastroenteric Hormones and Gastric Motility After Subtotal Gastrectomy

To investigate the effects of enteral nutrition (EN) and parenteral nutrition (PN) on gastric motility and gastroenteric hormones after subtotal gastrectomy. Forty-one patients underwent gastrectomy were randomly divided into EN group (n = 20) and PN group (n = 21). From the first postoperative day to the seventh day, patients received either EN (EN group) or PN (PN group) with isocaloric (84.9 kJ x kg(-1) x d(-1)) and isonitrogenous (0.11 g x kg(-1) x d(-1)) intake. Serum gastrin (GAS), plasma motilin (MTL), and plasma cholecystokinin (CCK) were measured on preoperative day, the first and seventh postoperative day. Electrogastrography (EGG) was measured on preoperative day and the seventh postoperative day. Compared with preoperation, blood GAS, MTL, and CCK levels of 41 patients decreased significantly on the first day after subtotal gastrectomy (P < 0.001), but returned to the preoperative levels one week later. EGG after gastrectomy showed that gastric basal electrical rhythm was significantly restrained (P < 0. 001). On the seventh day after subtotal gastrectomy, plasma MTL and CCK levels in EN group were higher than those in PN group (P < 0.05). There was no difference in GAS level between two groups. EGG in EN group was better than that in PN group postoperatively. The levels of gastroenteritic hormones and the gastric motility decrease significantly after subtotal gastrectomy. In contrast with PN, EN can accelerate the recovery of MTL, CCK, and gastric motility after subtotal gastrectomy.

Transcutaneous Electrogastrography in Patients with Ileus

Background: The aim of the prospective study was to characterize the disturbance of gastric electrical control activity in different types of ileus and to correlate surface electrogastrography (EGG) findings with a set of inflammatory markers. Patients and Methods: Fifty-four adult patients with mechanic, vascular and paralytic ileus proven on clinical and radiological exams and 14 age- and sex-matched controls were examined. Gastric myoelectrical activity was recorded using 3 Ag-AgCl disposable skin electrodes connected in pseudo-unipolar mode by Microdigitrapper device. The captured signal was amplified and digitalized. The dominant frequency was calculated using computerized algorithms (Fast Fourier transform and running spectrum analysis). The results were correlated with the known pathological diagnoses and 4 inflammatory parameters – interleukin (IL)-1β, IL-6, procalcitonin (PCT) and C-reactive protein. Results: Irregular EGG activity without a dominant frequency or bradygastria (electrical control activity frequency <2.4 cycles/min) was seen in all patients with both vascular and parayltic ileus and in 67.86% of the patients with obstructive ileus. Normogastria (2.4–3.7 cycles/min) was found in 32.14% of the patients with obstructive ileus. Among the patients with obstructive ileus and bradygastria, higher concentrations of IL-6 (642.0 ± 214.7 ng/l) and PCT (0.93 ± 0.22 µg/l) were observed compared with the patients with normogastria – IL-6 (354.5 ± 109.2 ng/l), PCT (0.69 ± 0.11 µg/l); p < 0.05 for both. The C-reactive protein concentration did not differ in both subgroups on p < 0.05. Conclusions: EGG examination confirmed a high sensitivity in the evaluation of gastric electrical control activity in both vascular and paralytic ileus. Significant correlation of EGG findings and both IL-6 and PCT plasma levels supports a role of the inflammatory milieu in the pathogenesis of impaired gastric electrical activity in patients with ileus.

Ketamine anesthesia reduces intestinal ischemia/reperfusion injury in rats

To investigate the effects of ketamine anesthesia on the motility alterations and tissue injury caused by ischemia/reperfusion in rats. Thirty male Wistar rats weighing 200-250 g were used. Ischemia was induced by obstructing blood flow in 25% of the total small intestinal length (ileum) with a vascular clamp for 45 min, after which either 60 min or 24 h of reperfusion was allowed. Rats were either anesthetized with pentobarbital sodium (50 mg/kg) or ketamine (100 mg/kg). Control groups received sham surgery. After 60 min of reperfusion, the intestine was examined for morphological alterations, and after 24 h intestinal basic electrical rhythm (BER) frequency was calculated, and intestinal transit determined in all groups. The intestinal mucosa in rats that were anesthetized with ketamine showed moderate alterations such as epithelial lifting, while ulceration and hemorrhage was observed in rats that received pentobarbital sodium after 60 min of reperfusion. Quantitative analysis of structural damage using the Chiu scale showed significantly less injury in rats that received ketamine than in rats that did not (2.35+/-1.14 vs 4.58+/-0.50, P<0.0001). The distance traveled by a marker, expressed as percentage of total intestinal length, in rats that received pentobarbital sodium was 20%+/-2% in comparison with 25.9%+/-1.64% in rats that received ketamine (P=0.017). BER was not statistically different between groups. Our results show that ketamine anesthesia is associated with diminished intestinal injury and abolishes the intestinal transit delay induced by ischemia/reperfusion.

Fractures and Nonunions of the Carpal Navicular

To study the effect of hypokinesia on rats small intestine (jejunum and ileum) biopotentials it was first necessary to characterize it. Biopotentials were recorded by intracellular placed microelectrodes from oral and caudal segments of the small intestine. The character of rats small intestine biopotentials differs from that of other species (man, cat, rabbit, dog, e.a.), the slow waves (SW) being smaller and the frequency of basal electrical rhythm higher (31.23 c/min orally and 24.50 caudally). Spike potentials are inscribed on the descending slope of SW but frequently delayed in each successive wave with a regular interval. Hypokinesia obtained by keeping rats in small cages for two weeks create only little changes in intestine biopotentials. The only clear difference was the increase of the slow waves amplitude. The other parameters were not specifically changed.

Visceral syndrome differentiation in traditional Chinese medicine and the changes of nutrition status or blood gas analysis in patients with chronic obstructive pulmonary disease

To investigate the relationship between visceral syndrome differentiation in traditional Chinese medicine (TCM) and the changes of nutrition status or blood gas analysis in patients with chronic obstructive pulmonary disease (COPD). Sixty patients with COPD in stable phase were divided into dysfunction of lung (DL, n=20) group, dysfunction of lung and spleen (DLS, n=16) group and dysfunction of lung, spleen and kidney (DLSK, n=24) group according to syndrome differentiation of TCM. Moreover, the basic electric rhythm, percentage of bradygastria in electrogastrogram (EGG), ratio of actual body weight (ABW) to ideal body weight (IBW) and serum albumin level were determined to evaluate the nutrition status of the patients with COPD. Blood gas analysis was made too. The basic electric rhythm values in the DL, DLS and DLSK groups were (56.20+/-13.24)%, (47.38+/-10.24)% and (41.35+/-10.01)%, respectively. Compared with the DL group, the basic electric rhythm values in the DLS and DLSK groups decreased obviously (P<0.05). The percentages of bradygastria in the DL, DLS and DLSK groups were (45.18+/-18.13)%, (46.31+/-15.83)% and (49.90+/-17.54)%, respectively, and there were no differences among the three groups (P>0.05). The incidence rates of ABW/IBW<90% in the DL, DLS and DLSK groups were 50%, 75% and 54.17%, respectively, and there were no differences among the three groups (P>0.05). The incidence rates of serum albumin less than 35 g/L were 20%, 37.5% and 54.17%, respectively, and there were no differences among the three groups (P>0.05). PO2 in the DLS group [(63.56+/-15.06) mmHg] and DLSK group [(63.17+/-19.05) mmHg] were decreased as compared with the DL group [(78.15+/-16.63) mmHg] (P<0.05). PCO2 in the DL, DLS and DLSK groups were (42.25+/-12.46) mmHg, (48.60+/-17.60) mmHg and (49.97+/-13.43) mmHg respectively, and there were no differences among the three groups (P>0.05). Several dysfunction organs described in TCM were involved in COPD followed by the increased severity, hypoxemia and PCO2. Dysfunction of gastrointestinal tract and malnourishment took place accordingly.

Dependent component analysis for the magnetogastrographic detection of human electrical response activity

The detection of the basic electric rhythm (BER), composed of a 3 cycles min−1 oscillation, can be performed using SQUID magnetometers. However, the electric response activity (ERA), which is generated when the stomach is performing a mechanical activity, was detected mainly by invasive electrical measurements and only recently was one report published describing its detection by magnetic measurements. This study was performed with the aim of detecting the ERA noninvasively after a meal. MGG recordings were made with a 74-channel first-order gradiometer (Magnes II, biomagnetic technologies) housed in a shielded room. Seven nonsymptomatic volunteers were measured in the study. Initially a 10 min recording was performed with the subject in the fasted state. A 250 kcal meal was given to the subject without moving out of the magnetometers and two epochs of 10 min each were acquired. The signals were processed to remove cardiac interference by an algorithm based on a variation of independent component analysis (ICA), then autoregressive and wavelet analysis was performed. Preliminary results have shown that there is an increase in the signal power at higher frequencies around (0.6 Hz–1.3 Hz) usually associated with the basic electric rhythm. The center of the frequency band and its width varied from subject to subject, demonstrating the importance of pre-prandial acquisition as a control. Another interesting finding was an increase in power after about 5 min of meal ingestion. This period roughly agrees with the lag phase of gastric emptying, measured by scintigraphy and other techniques. We confirm that MGG can detect the electric response activity in normal volunteers. Further improvements in signal processing and standardization of signal acquisition are necessary to ascertain its possible use in clinical situations.

An experimental study of the electrical activity of the bypassed stomach in the Roux-en-Y gastric bypass

Surgical options for morbid obesity are diverse, and the Roux-en-Y gastric bypass, initially described by Fobi has gained popularity. Knowledge about the physiology of the bypassed stomach is limited because this newly produced segment of the stomach is inaccessible to endoscopic or contrast radiological studies. To evaluate the myoelectric activity of the bypassed stomach and its reply to the feeding. An experimental protocol was conducted to evaluate postoperative gastric bypassed motility in dogs submitted to the Roux-en-Y gastric bypass procedure. Two groups of five animals were studied on postoperative fasting and after a standard meal, recording electrical response and control activity. Both control and Roux-en-Y gastric bypass operated study group had a pair of electrodes placed on three points of the remaining stomach: fundus, body and antrum. Data registration was performed after complete ileus resolution, and analysed with DATA Q Inst. series 200. The results achieved on the conditions of this study suggest that: 1. the remaining stomach maintain the same pattern of motility; 2. there is a reduced fasting electromyography activity following the Roux-en-Y gastric bypass procedure; 3. significantly reduced fasting electric control activity when compared both groups, and a markedly reduced fasting response electric activity and; 4. the electric response to the feeding kept the same standard of the stomach, however in a statistically reduced way. The electrical activity of the bypassed stomach of Roux-en-Y gastric bypass procedure kept the same pattern but in a statistically reduced number of contraction.

A biomagnetic assessment of colonic electrical activity in pigs

The electrical control activity of the large intestine was recorded in six pigs using a SQUID magnetometer. The study was performed in pre- and post-colectomy/sham-colectomy conditions. The biomagnetic field associated with colonic ECA changed drastically in subjects that underwent the colectomy procedure, whereas the signal for the control animals was nearly unchanged. Power spectral analysis was used to determine the average changes of dominant frequency and amplitude between baseline versus colectomy and sham-colectomy conditions. The dominant frequency was increased by 68 ± 24% (versus 2 ± 3% in control). The amplitude was decreased by 69 ± 24% (versus 13 ± 17% in control). This is the first study of transabdominal magnetic fields associated with colonic ECA, suggests some of the side effects generated in colectomy surgery and shows the utility of the biomagnetic technique in studies of the large intestine.

Magnetogastrographic detection of gastric electrical response activity in humans

The detection and characterization of gastric electrical activity has important clinical applications, including the early diagnosis of gastric diseases in humans. In mammals, this phenomenon has two important features: an electrical control activity (ECA) that manifests itself as an electric slow wave (with a frequency of 3 cycles per minute in humans) and an electrical response activity (ERA) that is characterized by spiking potentials during the plateau phase of the ECA. Whereas the ECA has been recorded in humans both invasively and non-invasively (magnetogastrography—MGG), the ERA has never been detected non-invasively in humans before. In this paper, we report on our progress towards the non-invasive detection of ERA from the human stomach using a procedure that involves the application of principal component analysis to MGG recordings, which were acquired in our case from ten normal human patients using a Superconducting QUantum Interference Device (SQUID) magnetometer. Both pre- and post-prandial recordings were acquired for each patient and 20 min of recordings (10 min of pre-prandial and 10 min of post-prandial data) were analysed for each patient. The mean percentage of ECA slow waves that were found to exhibit spikes of suspected ERA origin was 41% and 61% for pre- and post-prandial recordings, respectively, implying a 47% ERA increase post-prandially (P < 0.0001 at a 95% confidence level). The detection of ERA in humans is highly encouraging and points to the possible use of non-invasive ERA recordings as a valuable tool for the study of human gastric disorders.

Artifact reduction in magnetogastrography using fast independent component analysis

The analysis of magnetogastrographic (MGG) signals has been limited to epochs of data with limited interference from extraneous signal components that are often present and may even dominate MGG data. Such artifacts can be of both biological (cardiac, intestinal and muscular activities, motion artifacts, etc) and non-biological (environmental noise) origin. Conventional methods—such as Butterworth and Tchebyshev filters—can be of great use, but there are many disadvantages associated with them as well as with other typical filtering methods because a large amount of useful biological information can be lost, and there are many trade-offs between various filtering methods. Moreover, conventional filtering cannot always fully address the physicality of the signal-processing problem in terms of extracting specific signals due to particular biological sources of interest such as the stomach, heart and bowel. In this paper, we demonstrate the use of fast independent component analysis (FICA) for the removal of both biological and non-biological artifacts from multi-channel MGG recordings acquired using a superconducting quantum intereference device (SQUID) magnetometer. Specifically, we show that the signal of gastric electrical control activity (ECA) can be isolated from SQUID data as an independent component even in the presence of severe motion, cardiac and respiratory artifacts. The accuracy of the method is analyzed by comparing FICA-extracted versus electrode-measured respiratory signals. It is concluded that, with this method, reliable results may be obtained for a wide array of magnetic recording scenarios.