Effects of muscarinic receptor stimulation and nitric oxide synthase inhibition on gastric tone and gastric myoelectrical activity in canines.

AIMS: This study was designed to assess whether the muscarinic receptor stimulation and nitric oxide synthase inhibition were equally effective on gastric fundic tone or gastric myoelectrical activity (GMA) in canines, and the correlation between gastric fundic tone and GMA. METHODS: Gastric fundic tone and GMA were recorded on seven dogs implanted with serosal electrodes and a gastric cannula. RESULTS: Bethanechol and L-nitro-N-arginine (L-NNA) significantly increased gastric fundic tone; gastric volume was decreased with bethanechol or L-NNA (P < 0.05). Increased spike activities were observed after both bethanechol and L-NNA. The percentage of slow waves superimposed with spikes was increased with bethanechol (P < 0.001) and L-NNA (P < 0.05). There was a significant reduction in dominant frequency (DF) (P < 0.05), dominant power (DP) (P < 0.05) and percentage of normal slow waves (%N) (P < 0.05) with bethanechol, while no significant change was observed with L-NNA. The variation of gastric tone was not correlated with parameters of GMA. CONCLUSIONS: Muscarinic receptor stimulation and nitric oxide synthase inhibition have similar effects on gastric tone and gastric spike activities, but different effects on gastric slow waves. Gastric fundic tone does not correlate with gastric slow waves.

The effect on gastric tone of gastric electrical stimulation with trains of short pulses varies with sites and stimulation conditions.

BACKGROUND: Gastric electrical stimulation (GES) can improve symptoms in patients with gastroparesis and induce weight loss in obese subjects. AIMS: To evaluate the effect on gastric tone of GES under different conditions at different sites of the stomach. METHODS: Eleven dogs were implanted with a gastric cannula and two pairs of stimulation electrodes (in the middle of the lesser curvature and of the greater curvature, 10 cm from the pylorus). Gastric tone was assessed with a barostat. GES was applied using: (1) Enterra conditions (14 Hz, 5 mA, 0.3 ms, 0.1 s on, 5 s off); (2) modified Enterra conditions (40 Hz, 5 mA, 0.3 ms, 0.1 s on, 5 s off); and (3) implantable gastric stimulation (IGS) conditions (40 Hz, 5 mA, 0.3 ms, 2 s on, 3 s off). Six sessions were performed randomly with each animal on six separate days. RESULTS: (1) At the lesser curvature, GES with modified Enterra conditions significantly elevated gastric volume from 96.9 +/- 8.3 ml at baseline to 133.9 +/- 11.7 ml (P = 0.015) and a similar effect was observed with IGS (91.3 +/- 7.1 ml vs. 186.3 +/- 27.1 ml, P = 0.013). GES with Enterra conditions had no such an effect. (2) At the greater curvature, GES with Enterra conditions significantly increased gastric volume from basal 94.1 +/- 4.4 ml to 122.1 +/- 11.3 ml (P = 0.032); modified Enterra conditions had the opposite effect (96.5 +/- 9.0 ml vs. 77.4 +/- 11.7 ml, P = 0.025) and no significant effect was observed with IGS conditions. CONCLUSION: The effects of GES on gastric tone vary with the conditions and sites of stimulation. These findings may help to explain the distinct effects of GES therapy in patients with gastroparesis and obesity.

A phantom gallbladder on endoscopic retrograde cholangiopancreatography.

Various complications have been related to laparoscopic cholecystectomy but most occur shortly after the procedure. In this report, we present a case with very late complications in which an abscess developed within the gallbladder fossa 6 years after laparoscopic cholecystectomy. The abscess resolved after treatment with CT-guided extrahepatic aspiration. However, 4 years later, an endoscopic retrograde cholangiopancreatography (ERCP) performed for choledocholithiasis demonstrated a "gallbladder" which communicated with the common bile duct via a patent cystic duct. This unique case indicates that a cystic duct stump may communicate with the gallbladder fossa many years following cholecystectomy.

Environmental noise alters gastric myoelectrical activity: Effect of age.

AIM: To evaluate the effect of age and acoustic stress on gastric myoelectrical activity (GMA) and autonomic nervous system function. METHODS: Twenty-one male subjects (age range 22-71 years, mean 44 years) were recruited and exposed, in random order, to three auditory stimuli (Hospital noise, conversation babble and traffic noise) after a 20-min baseline. All periods lasted 20 min and were interspersed with a 10 min of recovery. GMA was obtained using a Synectics Microdigitrapper. Autonomic nerve function was assessed by monitoring blood pressure and heart rate using an automatic recording device. RESULTS: Dominant power tended to decrease with increase of age (P < 0.05). The overall percentage of three cycle per minute (CPM) activity decreased during exposure to hospital noise (12.0%, P <0.05), traffic noise (13.9%, P < 0.05), and conversation babble (7.1%). The subjects in the younger group (< 50 years) showed a consistent reduction in the percentage of 3 CPM activity during hospital noise (22.9%, P < 0.05), traffic noise (19.0%, P < 0.05), and conversation babble (15.5%). These observations were accompanied by a significant increase in bradygastria: hospital noise (P < 0.05) and traffic noise (P < 0.05). In contrast, the subjects over 50 years of age did not exhibit a significant decrease in 3 CPM activity. Regardless of age, noise did not alter blood pressure or heart rate. CONCLUSION: GMA changes with age. Loud noise can alter GMA, especially in younger individuals. Our data indicate that even short-term exposure to noise may alter the contractility of the stomach.

Experimental gastric dysrhythmias and its correlation with in vivo gastric muscle contractions.

AIM: To study the direct correlation between gastric dysrhythmias and in vivo gastric muscle tone. METHODS: Five healthy dogs were implanted with 4 pairs of electrodes along the greater curvature, with a strain gauge (SG) being sutured parallel to the distal electrodes (2 cm above the pylorus). Intravenous vasopressin was given to induce gastric dysrhythmia. The percentage of regular slow waves and SG energy were calculated. RESULTS: (1) the regularity of gastric myoelectric activity (GMA) was reduced during and after infusion of vasopressin; (2) SG energy was significantly decreased during the infusion of vasopressin; (3) the decrease in SG energy was well correlated with the reduction in GMA regularity; (4) SG energy was negatively correlated with bradygastria and tachygastria. CONCLUSION: Vasopressin inhibits gastric contractions and impairs gastric slow waves; gastric dysrhythmias are associated with the reduced antral muscle contractions, and are indicative of antral hypomotility.

[Follow-up study for newborns and infants who failed hearing screening].

OBJECTIVE: To study the audiological characteristics of newborns and infants who failed hearing screening. METHODS: One hundred and six infants failed hearing screening received follow-up study with routine audiological evaluations (auditory brainstem response, distortion product otoacoustic emission, tympanometry and visual reinforcement audiometry). RESULTS: Sixty-five infants (61.3%) of this group were normal hearing subjects and 39(36. 8% ) of the infants had hearing loss. Two cases (1.9%) received follow-up by phone. Fifteen cases (14.2%) with conductive hearing loss and 24 cases (22.6%) with sensorineural hearing loss. Thirteen (12.3%), 14 (13.2%), 6 (5.7%), and 6 (5.7%) cases were found to be mild, moderate, severe and profound hearing loss respectively. Diagnosis of hearing loss in the thirty-nine infants conducted a prevalence of 0.264% (39/14 785) of congenital hearing loss (both binaural and monaural). The hearing level of those cases with severe and profound hearing loss basically did not change, but that of cases with mild and moderate hearing loss changed. CONCLUSIONS: Early identification and intervention of infants with severe and profound hearing loss by 6 months of age were successful. Infants with mild and moderate hearing loss should be followed up to six or eight months and received routine audiologic evaluations.

Rectal distension modulates canine gastric tone and accommodation.

Rectal distension affects upper GI myoelectrical activity and motility. The aim of this experiment was to investigate the effect of rectal distension on gastric tone, accommodation, and the underlying mechanism. Seven healthy dogs were surgically prepared and studied. Gastric tone and accommodation were assessed with a barostat. In Experiment 1, the effect of rectal distension on gastric tone and accommodation was evaluated; in Experiment 2, rectal distensions with various volumes were randomly applied and its effects on gastric tone were evaluated; and in Experiment 3, the role of the cholinergic pathway in distension-induced gastric relaxation was assessed. The results showed the following. (1) Rectal distension exerted an inhibitory effect on gastric tone, and this response was distension volume-dependent. (2) Postprandial gastric volume was similar in the control (468.6 +/- 24.7 ml) and the distension study (463.2 +/- 17.5 ml). However, rectal distension increased the preprandial gastric volume, and subsequently decreased the extent of gastric accommodation (139.3 +/- 34.7 ml), which was significantly lower than that of the control (383.2 +/- 26.3 ml; P < 0.001). (3) An intravenous bolus of atropine increased the astric volume from the baseline of 89.4 +/- 12.6 ml to 161.5 +/- 9.8 ml (P < 0.01), and subsequent rectal distension further increased this volume, but the overall change was comparable between the control (297.6 +/- 18.7 ml) and the atropine study (312.1 +/- 21.9 ml; P > 0.05). In conclusion, rectal distension inhibits gastric tone in a volume-dependent manner and impairs gastric accommodation. Atropine dose not block the effect of rectal distension on proximal gastric tone, suggesting that the observed effect may not be mediated by cholinergic pathway.

Gastric electrical stimulation significantly increases canine lower esophageal sphincter pressure.

This study determined the effect of low-frequency and high-frequency gastric electrical stimulation (GES) on canine lower esophageal sphincter (LES) pressure and also evaluated the effect of such stimulation on neurohumoral factors that modulate LES pressure. Eight dogs were fitted with stimulation wires along the greater curvature of the stomach. A sleeve device measured LES pressure before, during, and after GES, and regulatory peptides were measured during fasting and after a meal. A consistent and significant rise in LES pressure was observed during GES, and it was sustained after GES was discontinued. Plasma concentration and area under the curve of pancreatic polypeptide, motilin, gastrin and neurotensin were not affected by GES. We conclude that acute low- and high-frequency GES significantly increases LES pressure. This effect may not be modulated by efferent vagal activity or release of regulatory peptides.

Effects and mechanisms of implantable gastric stimulation on gastric distention in conscious dogs.

BACKGROUND: While implantable gastric stimulation (IGS) on the lesser curvature has been reported to induce weight loss in obese patients, its mechanisms involving gastric mechanical activity remain largely unknown. The aim of this study was to investigate the effect and mechanism of IGS on gastric tone in canines. METHODS: 8 healthy dogs were implanted with a gastric cannula on anterior stomach and a pair of electrodes at lesser curvature. Gastric tone was assessed with an electronic barostat in 2 randomized sessions, a control and a session with L-NNA (nitric oxide synthase inhibitor). The control session included 30 min baseline, followed by 30 min with IGS; the L-NNA session included 30 min baseline, 30 min immediately after a bolus of L-NNA, and 30 min with IGS. RESULTS: 1) In the control session, IGS significantly increased the proximal gastric volume from baseline 91.3+/-7.1 ml to 186.3+/-27.1 ml (P<0.05); 2) L-NNA markedly reduced the proximal gastric volume from 110.3+/-11.9 ml to 56.9+/-10.8 ml (P<0.01); and subsequent IGS did not significantly increase the proximal gastric volume (P>0.05). CONCLUSION: IGS significantly inhibits proximal gastric tone or induces gastric distention, and this inhibitory effect is mediated via the nitrergic pathway.

Alterations of gastrointestinal motility in obesity.

All nutrients are absorbed in the gastrointestinal (GI) system, and GI motility plays a very critical role in the consumption of foods, digestion, and absorption of nutrients. Various segments of the GI tract (esophagus, stomach, and intestines) coordinate in a complex yet precise way to control the process of food consumption, digestion, and absorption of nutrients. GI motility not only regulates the rates at which nutrients are processed and absorbed in the gut but also participates in the control of appetite and satiety. Altered GI motility has been associated with various disease conditions (gastroparesis, etc.) and has been frequently observed in obese patients. The significance of these GI motility alterations in obesity is not fully understood, but they have been considered as potential contributing factors in the development and maintenance of obesity and changed eating behavior. Therapies aimed at regulating GI motility are being actively explored and applied clinically for the management of obese patients. To better understand the pathophysiology of obesity, we systematically reviewed GI motility changes observed in obese conditions. The relationship and pathological significance of these findings, as well as the potential therapies by modification of GI motility, are also discussed.

Electroacupuncture restores impaired gastric accommodation in vagotomized dogs.

The aim of this study was to investigate the effects of electroacupuncture (EA) on impaired gastric accommodation in a canine model. Ten dogs were chronically implanted with a gastric cannula in the stomach. Truncal vagotomy was performed in five of the dogs. A polyethylene bag attached at the end of a catheter was placed in the proximal stomach via the cannula. Gastric compliance, gastric tone, and postprandial gastric accommodation were evaluated using a gastric barostat with and without EA on two separate days, respectively. Results were as follows. (1) The postprandial gastric volume increase was 180.8 +/- 54.3 ml in vagotomized dogs, which was significantly lower than that (317.3 +/- 37.3 ml; P < 0.05) in normal dogs. (2) In normal dogs, EA did not affect gastric compliance, basal gastric tone, or postprandial gastric accommodation. (3) In vagotomized dogs, EA did not affect gastric compliance or basal gastric tone but restored the impaired gastric accommodation. The postprandial gastric volume increase was significantly enhanced with EA compared to the control (275.0 +/- 45.8 vs. 180.8 +/- 54.3 ml; P < 0.02). EA restores impaired gastric accommodation induced by vagotomy and may have therapeutic potential for patients with gastroparesis.

Gastric electrical stimulation does not significantly affect canine gastric acid secretion and 24-hour gastric pH.

Gastric electrical stimulation (GES) was shown to improve symptoms in patients with gastroparesis. However, the underlying mechanisms remain unclear. This study assessed the influence of various patterns of GES on fasting and postprandial gastric acid secretion and 24-hr gastric pH. Eight healthy dogs were studied and we found that in the fasting state, low-frequency, long-pulse (6/12-cpm, 375-msec, 4-mA) GES at the proximal stomach significantly inhibited the secretion of gastric juice (P < 0.05). No such effect was observed during GES (6/12 cpm) at the distal stomach. In the postprandial period, low-frequency, long-pulse GES at both proximal and distal sites and at both frequencies did not significantly affect gastric acid secretion. High-frequency, short-pulse GES, investigated for obesity (21 Hz, 8 mA, and 250 microsec, with 2 secs on, 3 sec off), at the proximal and distal stomach did not significantly affect the 24-hr gastric pH profile. In conclusion, GES with various stimulation parameters, and at various sites, has little effect on gastric acid secretion. The clinical effects induced by GES at these parameters may not be related to their effect on gastric acid homeostasis.

Transcutaneous electrical acustimulation can reduce visceral perception in patients with the irritable bowel syndrome: a pilot study.

OBJECTIVES: Acupuncture has been used as a therapy for various gastrointestinal disorders, including irritable bowel syndrome (IBS). However, there is scant information on the effect of acupuncture on gut physiology. The purpose of this study was to evaluate the effect of transcutaneous electrical acustimulation (TEAS) on rectal tone, compliance and perception in IBS patients. METHODS: Seven patients with diarrhea-predominant IBS were studied during control, sham stimulation and acupoints (ST36 and P6) stimulation periods. Rectal tone, compliance and perception to rectal balloon distension were assessed with a barostat apparatus. RESULTS: Acustimulation at ST36 and P6, but not sham stimulation, significantly increased the threshold of rectal sensation of gas, desire to defecate and pain, as compared to control period. However, rectal tone and compliance were not significantly affected during TEAS. CONCLUSIONS: TEAS, at the above acupoints, can reduce rectal sensitivity in IBS patients. The effect is not modulated by changes in rectal biomechanics.

The effect of gastric electrical stimulation on canine gastric slow waves.

This study determined the most efficient parameters of low-frequency/long-pulse gastric electrical stimulation (GES) required to entrain gastric slow waves and also evaluated the effect of entrainment and high-frequency, short-pulse GES on gastric electrical activity (GEA). Nine dogs were fitted with stimulation wires along the greater curvature. Entrainment was observed in six or seven animals, with long-pulse GES at six cycles per minute (cpm), at various combinations of current and pulse width and was directly related to the energy delivered. Entrainment was observed in four to seven animals, with GES at 12 cpm, and the maximal driven frequency was 6 cpm. Entrainment did not significantly increase the dominant power of GEA. High-frequency, short-pulse GES, using pulse trains of 14 Hz, 5 mA, and 330 micros, with 0.1 s on and 5 s off, and pulse trains of 40 Hz, 10 mA, and 330 micros, with 2 s on 3 s off, did not affect variables of GEA. We conclude that acute low-frequency GES but not high-frequency, short-pulse GES can entrain slow waves; the power of slow waves is not affected by either type of stimulation.

Gastric electrical-stimulation effects on canine gastric emptying, food intake, and body weight.

OBJECTIVE: It has been reported that electrical stimulation at the distal stomach can disrupt intrinsic gastric electrical activity and delay gastric emptying. Gastric dysrhythmia and impaired gastric emptying are associated with upper gastrointestinal symptoms and weight loss. The purpose of this study was to evaluate the effect of low-frequency/long-pulse gastric electrical stimulation (GES), at proximal and distal stomach, on canine gastric emptying, food intake, and body weight. RESEARCH METHODS AND PROCEDURES: Eight dogs were surgically implanted with four pairs of electrodes along the greater curvature and a gastric tube at the dependent part of the stomach. Liquid gastric emptying at baseline, during proximal and distal GES at 6 cycles per minute, was assessed first by a dye dilution technique. Proximal and distal GES were then randomly delivered during feeding for 10 consecutive days, and food intake and body weight were recorded daily. RESULTS: There was no significant difference in gastric emptying parameters among the various sessions. The mean daily food consumption was significantly reduced during both sessions of GES, resulting in significant immediate weight loss. Percentage weight loss was comparable between both sessions of GES. DISCUSSION: Short-term GES significantly reduced canine food intake and weight. This effect may not be related to changes in gastric emptying. GES may have a potential role in the treatment of obesity.