Role of sham feeding in postprandial changes of gastric myoelectrical activity

The aim of this study was to evaluate the role of sham feeding in postprandial changes of gastric myoelectrical activity. Eighteen asymptomatic healthy volunteers (10 men, 8 women; mean age: 31), with no history of gastrointestinal disease were studied. Gastric myoelectrical activity was recorded for 30 min at baseline, 30 min after sham feeding, and 1 hr after eating, using surface electrogastrography. The electrogastrogram (EGG) was analyzed by spectral analysis. It was found that the changes of postprandial EGG parameters were significantly correlated with those after sham feeding (EGG dominant power:r=0.6,P<0.01; dominant frequency:r=0.8,P<0.001; percentage of regular slow waves:r=0.7,P<0.003). We concluded that intrinsic gastric electrical activity can be altered by sham feeding and the cephalic phase of digestion plays an important role in the postprandial response of gastric myoelectrical activity.     

Effect of meal composition and sham feeding on duodenojejunal motility in humans

The disruptive effect of meals of different fat content and caloric value and of sham feeding on the interdigestive migrating motor complex (IDMMC) was studied in eight healthy subjects using an ambulatory recording system that allowed continuous monitoring of small bowel motility for three consecutive days. The durations of fed pattern were not significantly different between meals of 800 kcal/50% fat, 400 kcal/50% fat, and 800 kcal/25% fat, but were significantly longer compared to IDMMC cycle length and sham feeding. The latter two were not significantly different. On a separate day, five subjects consumed a meal of 400 kcal/9% fat and a second one of 800 kcal/50% fat. The duration of the fed pattern following the high fat meal was significantly longer than the low fat one. Sham feeding significantly increased plasma concentrations of gastrin and neurotensin (NT), but did not affect those of cholecystokinin (CCK), insulin, and peptide YY (PYY). The various variables of the IDMMC were not different during the two nights of the study, and velocity of migration of phase III during the first day and both nights was similar. We conclude that the duration of the fed pattern depends, in part, on the composition of the meal. Sham feeding, resulting in an increase in both plasma gastrin and NT concentrations, does not disrupt the IDMMC. When using thin probes, IDMMC is stable during prolonged recording.A preliminary report of this work was at the meeting of the American Motility Society, October 1990, and was published as an abstract in Gastroenterology 1990;99:A1232.This study was supported by grant RR59 for General Clinical Research Center Program, Division of Research Resources, NIH.     

Gastric Acid Response to Sham Feeding and Pentagastrin before and after Parietal Cell Vagotomy in Patients with Duodenal Ulcer

The influence of sham feeding (PAO_Sh) preceding pentagastrin-stimulated gastric acid secretion (PAO_Pg) was investigated in 28 patients with duodenal ulcer (DU) before vagotomy and in 36 after parietal cell vagotomy (PCV). Sham feeding had little influence on PAO_Pg and it is concluded that the two secretion tests may be combined. The ratio PAO_Sh/PAO_Pg was significantly reduced by PCV. Fourty-four patients with DU were studied for 1 year after PCV. and their PAO_Pg was measured preoperatively and their PAO_Pg and PAO_Sh postoperatively. Seven of the 44 patients had recurrent ulcer within 1 year. PAO_Pg had no predictive value pre- and postoperatively, but postoperative PAO_Sh and PAO_Sh/PAO_Pg were both significantly higher in patients with recurrent ulcer. It is concluded that PAO_Sh and PAO_Sh/PAO_Pg after PCV may assess completeness of vagotomy, but the relationship between PAO_Sh and risk of recurrent ulcer may be stronger than that between PAO_Sh/PAO_Pg and recurrence.     

Gastric distension is a physiologic satiety signal in the dog

Gastric distension is thought to produce satiety, but whether this effect is seen during physiologic distension by food is unknown. The purpose of this study was to determine whether levels of gastric distension seen during a meal have a satiety effect and whether the nutrient value of the meal was important. Four dogs were prepared with gastric, duodenal, and esophageal fistulas. Physiologic distension was determined by allowing the animals to eat liquid nutrient diet until sated and measuring the volume consumed and the time it took to consume it (¯x 2000 ml in 4 min). To test the effect of gastric distension on satiety, distension was produced during sham feeding by infusions of either liquid nutrient, inert liquid (Karaya), or by a water-filled balloon. Lower degrees of distension were also tested to determine if a dose-response relationship existed. Balloon, inert, and nutrient distension all inhibited sham feeding dose-dependently. Peak inhibitions of sham feeding caused by physiologic gastric distension (balloon, inert, nutrient) were 69±5%, 67±12%, and 61±6%, respectively. In all cases, maximal distension terminated sham feeding before the end of the feeding period. The effect of gastric distension on feeding was not blocked by pretreatment with atropine (50 g/kg). Thus, graded degrees of gastric distension, comparable to those seen during ingestion of a normal meal, produced graded inhibition of food intake by a noncholinergic mechanism and independent of the nutrient properties of the food.Supported in part by NIH grant R29-DK40790-01.     

Myoelectric activity during chronic small bowel allograft rejection in rats

The aim of this study was to analyze the effect of chronic rejection on myoelectric activity of orthotopic small intestine transplants in vivo. Chronic rejection was achieved in orthotopic small bowel allografts (ACI-Lewis) using cyclosporin A for limited immunosuppression. Isogeneic transplants (ACI–ACI) as well as native bowels (ACI) with and without immunosuppression served as controls. Myoelectric activities were recorded after a 12-hr fasting period and analyzed visually. Pacemaker frequencies within grafts were significantly below normal values (group 1: 37; group 2: 31.7; group 3: 37; group 4: 32.3). MMC periods and MMC phases did not show significant differences. The propagation velocity of phase III contractions was elevated in the ileum of grafts undergoing chronic rejection (group 1: 1.79; group 2: 1.59; group 3: 2; group 4: 2.5). In conclusion, fasting motility is altered but preserved in intestinal allografts undergoing chronic rejection. Intrinsic reinnervation from the native duodenum, which is necessary to generate normal pacemaker frequencies, was observed neither in allografts nor in isografts after a three-month period.     

Clinical management of post-pyloric enteral feeding in children

Post-pyloric feeding (PF) allows the administration of enteral nutrition beyond the pylorus, either into the duodenum or, ideally, into the jejunum. The main indications of PF are: upper gastrointestinal tract obstructions, pancreatic rest (e.g., acute pancreatitis), gastric dysmotility (e.g., critically ill patients and chronic intestinal pseudo-obstruction) or severe gastroesophageal reflux with risk of aspiration (e.g., neurological disability). Physiological and clinical evidence derives from adults, but can also be pertinent to children. This review will discuss the practical management and potential clinical applications of PF in pediatric patients. Some key studies pertaining to the physiological changes during PF will also be considered because they support the strategy of PF management.     

Does irradiation produce irreversible changes in canine jejunal myoelectric activity?

We sought to determine whether acute irradiation-induced changes in jejunal myoelectric activity are reversible or chronic and progressive with repeated exposures. Five dogs underwent abdominal irradiation absorbing 938 cGy on four separate occasions, two weeks apart. Recordings of jejunal myoelectric activity were made before and 10–11 days after each irradiation exposure. Ten to 11 days after the first exposure, the animals recovered completely from the acute radiation syndrome, and the myoelectric activity returned to normal. After subsequent exposures, they developed chronic diarrhea, profound weight loss, and progressive changes in myoelectric activity. Slow waves exhibited highly variable configuration, had an irregular rhythm, and were frequently uncoupled. Spike burst activity, duration, and length of migration were reduced in association with abnormal motility patterns even though histologic abnormalities were mild. Such changes are likely to interfere with normal propulsion and contribute to impaired nutrition. The abnormalities suggest that irradiation causes dysfunction of one or more of the cellular elements involved in small bowel motility (muscle, nerve, and interstitial cells) prior to the development of severe histologic abnormalities or mechanical obstruction.Supported by medical research funds from the Department of Veterans Affairs.     

Effect of glucagon on vagally induced gastric acid secretion in humans

The effect of a physiologically relevant dose of pancreatic glucagon, 85 pmol/kg/hr, or saline on gastric acid secretion induced by modified sham feeding (chew and spit), was studied in 10 healthy volunteers. Gastric pH was held constant (pH 5.5) by intragastric titration. Glucagon infusion inhibited gastric acid secretion significantly, from 19.6±1.5 mmol H⁺ per hour during saline, to 10.4±1.4 mmol H⁺ per hour. Blood glucose increased during glucagon infusion and remained constant during saline infusion. Serum gastrin concentrations increased significantly by sham feeding, during saline as well as glucagon infusion, and no difference between the gastrin response during saline or glucagon infusion was found. Thus glucagon, in a physiologic dose, reduces vagally mediated acid secretion by a gastrin-independent mechanism.This study was supported by the Danish Hospital Foundation for Medical Research, Region of Copenhagen, The Faroe Islands and Greenland.     

Impaired Gastric Myoelectrical Activity in Patients with Parkinson's Disease and Effect of Levodopa Treatment

The aim of this study was to evaluate gastric myoelectrical activity in patients with Parkinson's disease during and after levodopa treatment. Thirteen Parkinson's patients and 13 age-matched Parkinson's-free controls were enrolled. Electrogastrography was used to record gastric myoelectrical activity in all subjects for 30 min before and 30 min after a standard meal. In the group with Parkinson's disease, gastric myoelectrical activity was recorded during both the "on" (with levodopa treatment) and the "wearing-off" (without levodopa for at least 12 hr) periods. Results were as follows. (1) The patients without treatment showed a significantly lower percentage of regular slow waves and a significantly higher instability coefficient of the dominant frequency; (2) the patients showed an absence of the normal postprandial increase in gastric slow wave frequency which was seen in the controls: and (3) treatment with levodopa resulted in an improvement in the fed state, including a marginal increase in the percentage of regular slow waves (P = 0.1), a significant decrease in the instability coefficient, and an enhanced postprandial power increase. In conclusion, patients with Parkinson's disease have reduced slow wave rhythmicity and an impaired postprandial response in gastric myoelectrical activity. These abnormalities may be partially corrected with levodopa treatment in the fed state.     

Exogenous Neuropeptide Y Blocks Myoelectric Activity in the Upper Gastrointestinal Tract of Starved Dogs: Brain Neuropeptide Y Converts a Fasting Pattern of Myoelectric Activity to a Fed Pattern

The effect of intracerebroventricular (ICV) neuropeptide Y (NPY) on the migrating motor complex (MMC) was examined in five starved dogs. Myoelectric activity was recorded using gastric, duodenal, and jejunal electrodes. Intragastric pressure was monitored via a gastric fistula, and ICV injections were given through a cerebroventricular guide. Recordings were made with no ICV injection and before and after 250-μl bolus injections of vehicle as control (0.1% dog serum albumin in saline) or 500 pmol/kg NPY. The mean interval between MMCs was 98 ± 10 min without ICV injection and 96 ± 7 min after control solution. After ICV injection of NPY no further MMCs were recorded in any dog, even though the study was continued for a minimum of 3.5 h. Instead, the myoelectric pattern became indistinguishable from that in fed dogs. We conclude that central NPY plays a role in modulation of upper gastrointestinal myoelectric activity. This may reflect a central regulatory role for NPY in the coordination of feeding.     

Origins and patterns of spontaneous and drug-induced canine gastric myoelectrical dysrhythmia

The aim of this study was to investigate the characteristics and orientation of gastric dysrhythmia using multichannel serosal recordings in dogs. Ten dogs chronically implanted with four to eight pairs of electrodes were studied. Gastric slow waves were recorded in four sessions: postsurgical and after atropine, vasopressin, and glucagon. A total of 554.7 min of bradygastria, 201 min of tachygastria and 22.3 min of arrhythmia were observed in the recordings. The majority of bradygastria (80.5 ± 9.4%) originated in the proximal stomach (P < 0.04, vs other locations) and propagated all the way to the distal antrum. In contrast, tachygastria mainly originated in the distal antrum (80.6 ± 8.8%) (P < 0.04, vs other locations) and propagated partially or all the way to the proximal stomach. Dysrhythmia appeared intermittently with normal gastric slow waves. In all recordings, normal slow waves were present 38.0 ± 5.3% of the time, while bradygastria, tachygastria, and arrhythmia were present 35.9 ± 5.3%, 23.0 ± 1.6%, and 2.4 ± 0.5% of the time, respectively. The prevalence of dysrhythmia was highest in the distal antrum (80.4%) (P < 0.01) and lowest in the proximal part of the stomach. In conclusion, tachygastria originates from an ectopic pacemaker in the distal antrum. It may completely or partially override the normal slow waves. Bradygastria is attributed to a decrease in the frequency of the normal pacemaker in the corpus. The prevalence of gastric dysrhythmia is different in different locations of the stomach and is highest in the distal antrum.     

Pharyngo-Esophageal Motility Disturbances in Patients with Myotonic Dystrophy

Background: Esophageal motility is often disturbed in patients with myotonic dystrophy. The esophageal motor derangement pattern and its correlation with esophageal and peripheral motor symptoms is not well defined. Our aims were to evaluate: 1) pharyngo-esophageal motor abnormalities in these patients; 2) the relationship between motor involvement and clinical manifestations; and 3) the correlation between pharyngo-esophageal motility abnormalities and peripheral neuromuscular involvement. Methods: We compared data from 18 patients and 18 healthy controls. Neuromuscular affectation was quantified with a five-point muscular disability rating scale. Pharyngo-esophageal symptoms were assessed with a directed questionnaire, whereas motility was evaluated by means of manometry. Results: Myotonic dystrophy patients had diminished pharyngeal contraction amplitude, upper esophageal sphincter basal pressure, and esophageal body contraction amplitude compared with the control group (P &lt; 0.001). No signs of esophageal myotony were evident. Simultaneous esophageal waves after more than 40% of liquid swallows were found in 80% of patients. No relationship between esophageal manometric alteration and esophageal or peripheral motility symptoms was elicited. Conclusion: In patients with myotonic dystrophy pharyngo-esophageal motility is severely deranged in both amplitude and coordination. These abnormalities may be present even if symptoms referred by the patient or the severity of the disease is not remarkable.     

Is There a One-to-One Correlation Between Gastric Emptying of Liquids and Gastric Myoelectrical or Motor Activity in Dogs?

The aim of this study was to investigate the correlation of gastric emptying with gastric myoelectrical activity recorded from internal serosal electrodes and with gastric motility measured from strain gauges. The study was performed in eight healthy dogs chronically implanted with four pairs of electrodes and two strain gauges on the gastric serosa and equipped with a duodenal fistula for the assessment of gastric emptying. Each dog was fed four liquid test meals on four separate days with identical calories (320 kcal) and volume (473 ml). A correlation was found between gastric emptying and the energy of contraction in the frequency band of 3.75–7.50 cycles/min during the first 30 min after the meal (r = 0.46, P < 0.05). While none of the parameters of gastric myoelectrical activity was correlated with gastric emptying, two major parameters, percentage of regular gastric slow waves and percentage of slow-wave coupling, were found to be associated with delayed gastric emptying. A significant correlation was found between the frequency of gastric slow waves and that of the contractions in both fasting (r = 0.83, P < 0.001) and fed state (r = 0.70, P < 0.001 at 30 min, r = 0.86, P < 0.001 at 60 min). It was concluded that gastric emptying is correlated with the strength of gastric contractions in a frequency range identical to that of the gastric slow waves, and there is no one-to-one correlation between gastric emptying of liquids and any parameters of gastric myoelectrical activity. However, major parameters of gastric myoelectrical activity are associated with gastric emptying.     

Abnormal gastric myoelectrical activity and delayed gastric emptying in patients with symptoms suggestive of gastroparesis

Gastric myoelectrical activity modulates gastric motor activity. Abnormalities in gastric myoelectrical activity may be associated with gastric motility disorders. The aim of this study was to investigate the correlation of gastric myoelectrical activity with gastric emptying in symptomatic patients with and without gastroparesis. Ninety-seven patients with symptoms suggestive of gastroparesis participated in the study. Gastric myoelectrical activity was recorded using surface electrogastrography. The electrogastrogram (EGG) was recorded for 30 min in the fasting state and for 120 min after a solid test meal. Gastric emptying of the solid meal was simultaneously monitored for 120 min. Patients with delayed gastric emptying showed a significantly lower percentage of normal gastric slow waves (P<0.03) and a significantly reduced increase of the dominant power in the postprandial EGG (P<0.02). Postprandial EGG parameters were found to be able to predict delayed emptying of the stomach. Postprandial gastric dysrhythmia predicts delayed gastric emptying with an accuracy of 78%, while the abnormality in postprandial EGG power predicts delayed gastric emptying with an accuracy of 75%. All patients with abnormalities in both the rhythmicity and the power had delayed gastric emptying. Patients with delayed gastric emptying have a lower percentage of normal gastric slow waves in the EGG and a lower postprandial increase in the dominant power. Abnormalities in the postprandial EGG seem to be able to predict delayed emptying of the stomach. However, a normal EGG does not seem to guarantee normal emptying of the stomach.     

Gastrointestinal myoelectric activity in an infant with congenital idiopathic motility disorder

We investigated myoelectric activity in an 8-month-old male who presented with a perinatal bowel obstruction, duodenal band, congenital short small intestine, and persistent feeding intolerance. Serosal electrodes were surgically implanted on stomach, duodenum, and jejunum during Nissen fundoplication and ileostomy. A 5-cm ileal specimen was taken for in vitro studies. Spontaneous migrating myoelectric complexes (MMC) were present in stomach and small intestine. Bethanechol increased electrical response activity (ERA) in stomach and duodenum. Morphine induced intense ERA and distinct phase III activity. Pentagastrin infusion did not disrupt MMC cycling. Feeding disrupted MMC complex cycling 30-40 min after the meal. Metoclopramide before feeding delayed disruption of the MMC cycling after the feeding. Intermittent gastric arrhythmias were present after the fifth postoperative day. In vitro muscle strips showed spontaneous contractions and electrical control activity (ECA). Bethanechol, McNeil A-343, motilin, and cholecystokinin induced contractions, but pentagastrin had no effect. We conclude that in spite of a major clinical motility dysfunction, several of our findings were normal. The abnormalities include short MMC period, absence of disruption of MMC by pentagastrin, and gastric arrhythmias.     

Effect of barium meals on gastric electromechanical activity in man

The relationship between the cutaneously recorded electrogastrogram (EGG) and gastric contractions in man is unclear. We investigated: (1) the relationship between the electrogastrogram (EGG) signals and gastric contractions elicited by barium meals and (2) the effects of barium meals on frequency and amplitude of EGG signals. As documented by fluoroscopy in four healthy subjects, barium meals stimulated three per minute gastric peristalsis which corresponded with simultaneously recorded three cycle per minute (cpm) EGG waves. Eighteen other healthy volunteers ingested 45% (w/v) or 60% barium suspensions. As determined by Fourier analysis, the dominant EGG frequency before barium was 3 cpm in 16 subjects; two subjects had no distinct frequency peaks. After barium ingestion, the mean amplitude or power at 3 cpm and 1 cpm increased, but the increase was significant only after 45% barium. In conclusion: (1) individual EGG waves after barium reflect gastric peristaltic sequences, which are reflected in increases in amplitude or power of 3 cpm EGG activity; (2) density or viscosity of the barium meal affects the gastric myoelectric response; and (3) mechanical correlates of 1 cpm EEG activity are unknown.     

Identification and Quantification of Aberrant Crypt Foci in the Colon of Min Mice - A Murine Model of Familial Adenomatous Polyposis

Min mice are heterozygous for a nonsense mutation in the murine adenomatous polyposis coli (APC) gene and spontaneously develop multiple intestinal neoplasms similar to the familial adenomatous polyposis (FAP) syndrome in humans. Aberrant crypt foci (ACF) are assumed to be preneoplastic lesions in both murine and human colon carcinogenesis and have been observed in FAP patients. Light microscopic examination of the colonic mucosa of 42 Min mice did not show even a single 'classical' ACF on the basis of previously defined criteria, specifying that they are elevated above the surrounding mucosa. However, in Min mice we discovered aberrant crypt foci of a different type, which we denoted ACFMin. In contrast to the classical type, ACFMin were not elevated above the surrounding mucosa, their detection was totally dependent on methylene blue staining and transillumination, and they could not be identified with scanning electron microscopy. Histopathologic examination of ACFMin showed dysplastic crypts, similar to those found in larger lesions-that is, microadenomas in the Min mouse. The number of ACFMin increased up to the age of 6 weeks and then seemed to remain at a constant level of approximately four per colon. In conclusion, by transillumination of whole-mount preparations stained with methylene blue, we have identified and quantified small microscopic lesions that may be precursors of colonic adenomas in Min mice.     

Integration of canine proximal gastric,antral, pyloric,and proximal duodenal motility during fasting and after a liquid meal

The aim was to investigate the integration of proximal gastric, antral, pyloric, and duodenal motility during fasting and after feeding. Using a proximal gastric barostat and a manometric assembly with an array of side holes astride the gastroduodenal junction, the gastrointestinal interdigestive migrating motor complex was detected in five of seven conscious fasting dogs. During phase III of the complex, which lasted a mean ± SEM of 13 ± 0.5 min, 9.6 ± 0.9 volume waves were present in the proximal stomach. The volume waves were coordinated with clusters of antral waves 64 ± 11% of the time and with inhibition of duodenal waves 91±3% of the time. A 300-ml calorie-dense liquid meal abolished the complex and promptly increased proximal gastric volume in five of six dogs. Volume waves were nearly completely suppressed, while antral waves decreased from 24 ±3.0 waves/10 min to 10±2.8 waves/10 min (P<0.05) and isolated pyloric pressure waves increased from 7.2±2.8 waves/10 min to 22±3.3 waves/10 min (P<0.005). In summary, proximal gastric motility was integrated with antral, pyloric, and duodenal motility under both fasting and fed conditions. The integrated patterns likely account for the efficient clearance of indigestible solids during fasting and the controlled emptying of nutrients with feeding.Supported in part by USPHS NIH Grants DK 18278, DK34988, and DK07198, the Winthrop Travelling Fellowship of the Royal Australasian College of Physicians, the S.K.F. (Australia) Travelling Fellowship, and the Mayo Foundation.This work was presented in part before the World Congress of Gastroenterology, Sydney, Australia, August 30, 1990     

Effect of Preinjury Large Bowel Emptying on the Inhibition of Upper Gastrointestinal Motility After Spinal Cord Injury in Rats

Spinal cord transection (SCT) inhibits gastrointestinal motility in rats. We evaluated the effect of preinjury large bowel emptying on this phenomenon. Male Wistar rats (N = 52) were fasted for 24 or 48 hr with water ad libitum and pretreated with lactose (0.8 g) or saline. Next, laminectomy followed or not by complete SCT between T4 and T5 vertebrae was performed. Phenol red recovery in the stomach and proximal, medial, and distal small intestine was determined 1 day later. In animals submitted to 24 hr fasting + saline, SCT increased gastric recovery by 42.8% decreased medial small intestine recovery by 56.2%, while 48 hr fasting + saline or 24 hr fasting + lactose prevented the inhibition of gastric emptying (GE) in SCT animals. The 48 hr fasting + lactose prevented the inhibition of both GE and gastrointestinal transit. SCT-induced inhibition of upper gastrointestinal motility may involve enhancement of inhibitory reflexes, which can be prevented by large bowel emptying.     

Cutaneous gastric electrical stimulation alters gastric motility in dogs: New option for gastric electrical stimulation?

Background and Aim:  We investigated the effects of cutaneous gastric electrical stimulation (CGES) on gastric myoelectrical activity, postprandial antral contractions and gastric tone in dogs.
Methods:  CGES was carried out via abdominal surface electrodes over the stomach. After an overnight fast, gastric slow waves were recorded from the serosal electrodes in six dogs at a frequency of 4.4 cycles/min (c.p.m.) or 10 c.p.m. Nine dogs were used for the measurement of postprandial antral contractions. Gastric tone at baseline and during CGES was measured in six of the dogs.
Results:  We found that: (i) CGES at 4.4 c.p.m. decreased slow wave frequency (5.1 vs 4.6 c.p.m., P  < 0.05) and increased slow wave power (−6.2 vs 2.7 c.p.m., P  < 0.05); CGES at 10 c.p.m. increased slow wave frequency (5.1 vs 9.2 dB, P  < 0.05) and decreased normal slow waves (85.4% vs 60.0%, P  < 0.05); (ii) CGES at 10 c.p.m. significantly suppressed postprandial antral contractions ( P  < 0.01); (iii) CGES had no effects on gastric tone.
Conclusions:  CGES is capable of altering gastric slow waves and inhibiting gastric motility. It may have therapeutic potential for treating eating disorders, such as obesity. However, clinical studies are needed to explore the potential of CGES.