Anil K. Vegesna

A missing sphincteric component of the gastro‐oesophageal junction in patients with GORD

Abstract  It was recently shown that the tonic pressure contribution to the high‐pressure zone of the oesophago‐gastric segment (OGS) contains the contributions from three distinct components, two of which are smooth muscle intrinsic sphincter components, a proximal and a distal component [ J Physiol 2007; 580.3: 961 ]. The aim of this study was to compare the pressure contributions from the three sphincteric components in normal subjects with those in gastro‐oesophageal reflux disease (GORD) patients. A simultaneous endoluminal ultrasound and manometry catheter was pulled through the OGS in 15 healthy volunteers and seven patients with symptomatic GORD, before and after administration of atropine. Pre‐atropine (complete muscle tone), postatropine (non‐muscarinic muscle tone plus residual muscarinic tone) and subtracted (pure muscarinic muscle tone) pressure contributions to the sphincter were averaged after referencing spatially to the right crural diaphragm and the pull‐through start position. In the normal group, the atropine‐resistant and atropine‐attenuated pressures identified the crural and two smooth muscle sphincteric components respectively. The subtraction pressure curve contained proximal and distal peaks. The proximal component moved with the crural sling between full inspiration and full expiration and the distal component coincided with the gastric sling‐clasp fibre muscle complex. The subtraction curve in the GORD patients contained only a single pressure peak that moved with the crural sphincter, while the distal pressure peak of the intrinsic muscle component, which was previously recognized in the normal subjects, was absent. We hypothesize that the distal muscarinic smooth muscle pressure component (gastric sling/clasp muscle fibre component) is defective in GORD patients.

Pharmacologic Specificity of Nicotinic Receptor-Mediated Relaxation of Muscarinic Receptor Precontracted Human Gastric Clasp and Sling Muscle Fibers within the Gastroesophageal Junction

Relaxation of gastric clasp and sling muscle fibers is involved the transient lower esophageal sphincter relaxations underlying the pathophysiology of gastroesophageal reflux disease (GERD). These fibers do not contribute tone to the high-pressure zone in GERD patients, indicating their role in pathophysiology. This study identifies some mediators of the nicotine-induced relaxation of muscarinic receptor precontracted gastric clasp and sling fibers. Muscle strips from organ donors precontracted with bethanechol were relaxed with nicotine and then rechallenged after washing and adding inhibitors tetrodotoxin (TTX), the nitric-oxide synthase inhibitor l-nitro-arginine methyl ester (l-NAME), the β-adrenoceptor antagonist propranolol, the glycine receptor antagonist strychnine or ginkgolide B, and the GABAA receptor antagonist bicuculline or 2-(3-carboxypropyl)-3-amino-6-(4 methoxyphenyl)pyridazinium bromide [(gabazine) SR95531]. TTX only inhibited clasp fiber relaxations. l-NAME and propranolol inhibited, and ginkgolide B was ineffective in both. SR95531 was ineffective in clasp fibers and partially effective in sling fibers. Strychnine and bicuculline prevented relaxations with low potency, indicating actions not on glycine or GABAA receptors but more consistent with nicotinic receptor blockade. Bethanechol-precontracted fibers were relaxed by the nitric oxide donor S-nitroso-N-acetyl-dl-penicillamine and by the β-adrenergic agonist isoproterenol (clasp fibers only) but not by the glycine receptor agonist taurine or glycine or the GABAA agonist muscimol. These data indicate that nicotinic receptor activation mediates relaxation via release of nitric oxide in clasp and sling fibers, norepinephrine acting on β-adrenoceptors in clasp fibers, and GABA acting on GABAA receptors in sling fibers. Agents that selectively prevent these relaxations may be useful in the treatment of GERD.

Quantitation of the contractile response mediated by two receptors: M2 and M3 muscarinic receptor-mediated contractions of human gastroesophageal smooth muscle.

Although muscarinic receptors are known to mediate tonic contraction of human gastrointestinal tract smooth muscle, the receptor subtypes that mediate the tonic contractions are not entirely clear. Whole human stomachs with attached esophagus were procured from organ transplant donors. Cholinergic contractile responses of clasp, sling, lower esophageal circular (LEC), midesophageal circular (MEC), and midesophageal longitudinal (MEL) muscle strips were determined. Sling fibers contracted greater than the other fibers. Total, M2 and M3 muscarinic receptor density was determined for each of these dissections by immunoprecipitation. M2 receptor density is greatest in the sling fibers, followed by clasp, LEC, MEC, and then MEL, whereas M3 density is greatest in LEC, followed by MEL, MEC, sling, and then clasp. The potency of subtype-selective antagonists to inhibit bethanechol-induced contraction was calculated by Schild analysis to determine which muscarinic receptor subtypes contribute to contraction. The results suggest both M2 and M3 receptors mediate contraction in clasp and sling fibers. Thus, this type of analysis in which multiple receptors mediate the contractile response is inappropriate, and an analysis method relating dual occupation of M2 and M3 receptors to contraction is presented. Using this new method of analysis, it was found that the M2 muscarinic receptor plays a greater role in mediating contraction of clasp and sling fibers than in LEC, MEC, and MEL muscles in which the M3 receptor predominantly mediates contraction.

Circular smooth muscle contributes to esophageal shortening during peristalsis

AIM To study the angle between the circular smooth muscle (CSM) and longitudinal smooth muscle (LSM) fibers in the distal esophagus. METHODS In order to identify possible mechanisms for greater shortening in the distal compared to proximal esophagus during peristalsis, the angles between the LSM and CSM layers were measured in 9 cadavers. The outer longitudinal layer of the muscularis propria was exposed after stripping the outer serosa. The inner circular layer of the muscularis propria was then revealed after dissection of the esophageal mucosa and the underlying muscularis mucosa. Photographs of each specimen were taken with half of the open esophagus folded back showing both the outer longitudinal and inner circular muscle layers. Angles were measured every one cm for 10 cm proximal to the squamocolumnar junction (SCJ) by two independent investigators. Two human esophagi were obtained from organ transplant donors and the angles between the circular and longitudinal smooth muscle layers were measured using micro-computed tomography (micro CT) and Image J software. RESULTS All data are presented as mean ± SE. The CSM to LSM angle at the SCJ and 1 cm proximal to SCJ on the autopsy specimens was 69.3 ± 4.62 degrees vs 74.9 ± 3.09 degrees, P = 0.32. The CSM to LSM angle at SCJ were statistically significantly lower than at 2, 3, 4 and 5 cm proximal to the SCJ, 69.3 ± 4.62 degrees vs 82.58 ± 1.34 degrees, 84.04 ± 1.64 degrees, 84.87 ± 1.04 degrees and 83.72 ± 1.42 degrees, P = 0.013, P = 0.008, P = 0.004, P = 0.009 respectively. The CSM to LSM angle at SCJ was also statistically significantly lower than the angles at 6, 7 and 8 cm proximal to the SCJ, 69.3 ± 4.62 degrees vs 80.18 ± 2.09 degrees, 81.81 ± 1.75 degrees and 80.96 ± 2.04 degrees, P = 0.05, P = 0.02, P = 0.03 respectively. The CSM to LSM angle at 1 cm proximal to SCJ was statistically significantly lower than at 3, 4 and 5 cm proximal to the SCJ, 74.94 ± 3.09 degrees vs 84.04 ± 1.64 degrees, 84.87 ± 1.04 degrees and 83.72 ± 1.42 degrees, P = 0.019, P = 0.008, P = 0.02 respectively. At 10 cm above SCJ the angle was 80.06 ± 2.13 degrees which is close to being perpendicular but less than 90 degrees. The CSM to LSM angles measured on virtual dissection of the esophagus and the stomach on micro CT at the SCJ and 1 cm proximal to the SCJ were 48.39 ± 0.72 degrees and 50.81 ± 1.59 degrees. Rather than the angle of the CSM and LSM being perpendicular in the esophagus we found an acute angulation between these two muscle groups throughout the lower 10 cm of the esophagus. CONCLUSION The oblique angulation of the CSM may contribute to the significantly greater shortening of distal esophagus when compared to the mid and proximal esophagus during peristalsis.

Ileocecal valve dysfunction in small intestinal bacterial overgrowth： A pilot study

AIM To explore whether patients with a defective ileocecal valve (ICV)/cecal distension reflex have small intestinal bacterial overgrowth. METHODS Using a colonoscope, under conscious sedation, the ICV was intubated and the colonoscope was placed within the terminal ileum (TI). A manometry catheter with 4 pressure channels, spaced 1 cm apart, was passed through the biopsy channel of the colonoscope into the TI. The colonoscope was slowly withdrawn from the TI while the manometry catheter was advanced. The catheter was placed across the ICV so that at least one pressure port was within the TI, ICV and the cecum respectively. Pressures were continuously measured during air insufflation into the cecum, under direct endoscopic visualization, in 19 volunteers. Air was insufflated to a maximum of 40 mmHg to prevent barotrauma. All subjects underwent lactulose breath testing one month after the colonoscopy. The results of the breath tests were compared with the results of the pressures within the ICV during air insufflation. RESULTS Nineteen subjects underwent colonoscopy with measurements of the ICV pressures after intubation of the ICV with a colonoscope. Initial baseline readings showed no statistical difference in the pressures of the TI and ICV, between subjects with positive lactulose breath tests and normal lactulose breath tests. The average peak ICV pressure during air insufflation into the cecum in subjects with normal lactulose breath tests was significantly higher than cecal pressures during air insufflation (49.33 ± 7.99 mmHg vs 16.40 ± 2.14 mmHg, P = 0.0011). The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflations in subjects with normal lactulose breath tests was significantly higher (280.72% ± 43.29% vs 100% ± 0%, P = 0.0006). The average peak ICV pressure during air insufflation into the cecum in subjects with positive lactulose breath tests was not significantly different than cecal pressures during air insufflation 21.23 ± 3.52 mmHg vs 16.10 ± 3.39 mmHg. The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflation was not significantly different 101.08% ± 7.96% vs 100% ± 0%. The total symptom score for subjects with normal lactulose breath tests and subjects with positive lactulose breath tests was not statistically different (13.30 ± 4.09 vs 24.14 ± 6.58). The ICV peak pressures during air insufflations were significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.005). The average percent difference of the area under the pressure curve in the ICV from cecum was significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.0012). Individuals with positive lactulose breath tests demonstrated symptom scores which were significantly higher for the following symptoms: not able to finish normal sized meal, feeling excessively full after meals, loss of appetite and bloating. CONCLUSION Compared to normal, subjects with a positive lactulose breath test have a defective ICV cecal distension reflex. These subjects also more commonly have higher symptom scores.

Endoscopic pyloric suturing to facilitate weight loss: a canine model

BACKGROUND More than 66% of adults in United States are overweight or obese. OBJECTIVE To decrease gastric emptying and cause early and prolonged satiety by endoscopically narrowing the gastric pylorus. DESIGN Thirteen dogs were randomized into 3 groups (suture, sham, and control). SETTING Animal facility. INTERVENTIONS Sutures were placed across the pylorus in the 7 dogs in the suture group by using an endoscopic suturing device. Three sham dogs had endoscopy without suturing, and 3 control dogs did not have any intervention. MAIN OUTCOME MEASUREMENTS Gastric emptying studies were conducted on all of the dogs by using 13C-octanoic acid breath tests. All dogs were monitored for daily food intake and weight gain/loss. RESULTS The suture dogs decreased their food consumption by 48% (P < .02), whereas the sham and control dogs showed 9.5% increase (P = .16). The suture dogs lost 12.7% (P = .001) of their initial body weight, whereas the sham and control dogs gained 13.4% (P = .03). There was a delay in gastric emptying between the presuturing baseline and last postsuturing measurement by 30.75% (P = .005) in the suture dogs. In the sham plus control dogs, there was a delay in gastric emptying during the same period by only 6.75% (P = .55). LIMITATIONS Long-term efficacy of the sutures was not evaluated. CONCLUSIONS There was a significant weight loss and decreased food consumption along with a significant prolongation of gastric emptying in the suture dogs compared with the sham and control dogs.

Characterization of the distal esophagus high-pressure zone with manometry, ultrasound and micro-computed tomography.

Background  We sought to determine how the individual components of the distal esophagus and proximal stomach form the gastroesophageal junction high‐pressure zone (GEJHPZ) antireflux barrier.

The esophagogastric junction

The following discussion of the esophagogastric junctions includes commentaries on the three component structures of the sphincteric segment between the stomach and the esophagus; the pressure contributions from the three sphincteric components in normal subjects and in gastroesophageal reflux (GERD) patients; the mechanism of action of endoscopic plication to determine the underlying pathophysiology of GERD; and in vitro muscle strip studies of defects within the gastroesophageal sphincteric segment potentially leading to GERD.

Comparison of human and porcine gastric clasp and sling fiber contraction by M2 and M3 muscarinic receptors

To compare the gastroesophageal junction of the human with the pig, M(2) and M(3) receptor densities and the potencies of M(2) and M(3) muscarinic receptor subtype selective antagonists were determined in gastric clasp and sling smooth muscle fibers. Total muscarinic and M(2) receptors are higher in pig than human clasp and sling fibers. M(3) receptors are higher in human compared with pig sling fibers but lower in human compared with pig clasp fibers. Clasp fibers have fewer M(3) receptors than sling fibers in both humans and pigs. Similar to human clasp fibers, pig clasp fibers contract significantly less than pig sling fibers. Analysis of the methoctramine Schild plot suggests that M(2) receptors are involved in mediating contraction in pig clasp and sling fibers. Darifenacin potency suggests that M(3) receptors mediate contraction in pig sling fibers and that M(2) and M(3) receptors mediate contraction in pig clasp fibers. Taken together, the data suggest that both M(2) and M(3) muscarinic receptors mediate the contraction in both pig clasp and sling fibers similar to human clasp and sling fibers.

Minimally invasive measurement of esophageal variceal pressure and wall tension (with video)

BACKGROUND There is no simple method to measure intravariceal pressure in patients with esophageal varices. OBJECTIVE Our purpose was to develop a new noninvasive technique to measure resting intravariceal pressure and wall tension. DESIGN A model was developed. A long balloon (varix) was fitted inside an airtight cylinder (esophagus). Fluid ran through the model varices to maintain 5 different constant pressures. An endoscope was placed in the model esophagus, and pressure was increased by air insufflation. The endoscopy and pressure readings from the esophagus and varix were recorded continuously until variceal collapse. SETTING Patient studies were done in an endoscopy suite with the patient under fentanyl and midazolam sedation. PATIENTS Esophageal pressure was measured during air insufflation in patients with varices until the varices collapsed. EUS was used to measure radius and wall thickness to calculate wall tension. RESULTS In the varix model, the mean (SD) intraluminal esophageal pressures at variceal flattening for the model varices at 5, 10, 15, 20, and 25 mm Hg were 5.69 (0.34), 11 (0.32), 15.72 (0.51), 21.55 (0.63), and 25.8 (0.14) mm Hg. The correlation between actual and measured variceal pressure in the model at variceal flattening was r = 0.98. In the patients, a total of 10 varices in 3 patients were evaluated. The mean (SD) for the varices in each subject was 12.16 (2.4), 23.2 (1.3), and 6.5 (2.2) mm Hg for subjects 1, 2, and 3, respectively. CONCLUSION Standard endoscopy with air insufflation and manometry can be used as an accurate, simple, and reproducible method to measure intravariceal pressure.