Hrair P. Simonian

Regional Postprandial Differences in pH Within the Stomach and Gastroesophageal Junction

Our objective was to determine regional differences in intragastric pH after different types of meals. Ten normal subjects underwent 27-hr esophagogastric pH monitoring using a four-probe pH catheter. Meals were a spicy lunch, a high-fat dinner, and a typical bland breakfast. The fatty dinner had the highest postprandial buffering effect, elevating proximal and mid/distal gastric pH to 4.9 ± 0.4 and 4.0 ± 0.4, respectively, significantly (P< 0.05) higher compared to 4.2 ± 0.3 and 3.0 ± 0.4 for the spicy lunch and 3.0 ± 0.3 and 2.5 ± 0.8 for the breakfast. The buffering effect of the high-volume fatty meal to pH > 4 was also longer (150 min) compared to that of the spicy lunch (45 min) and the bland breakfast, which did not increase gastric pH to > 4 at any time. Proximal gastric acid pockets were seen between 15 and 90 min postprandially. These were located 3.4 ± 0.8 cm below the proximal LES border, extending for a length of 2.3 ± 0.8 cm, with a drop in mean pH from 4.7 ± 0.4 to 1.5 ± 0.9. Acid pockets were seen equally after the spicy lunch and fatty dinner but less frequently after the bland breakfast. We conclude that a high-volume fatty meal has the highest buffering effect on gastric pH compared to a spicy lunch or a bland breakfast. Buffering effects of meals are significantly higher in the proximal than in the mid/distal stomach. Despite the intragastric buffering effect of meals, focal areas of acidity were observed in the region of the cardia–gastroesophageal junction during the postprandial period.

Differential effects of sham feeding and meal ingestion on ghrelin and pancreatic polypeptide levels: evidence for vagal efferent stimulation mediating ghrelin release1

Abstract  Ghrelin has been suggested to function as an appetite‐stimulating signal from the gastrointestinal tract to the brain acting through a vagal afferent pathway. Ghrelin levels rise before meals and fall after meal ingestion. The purpose of this study was to investigate factors which regulate ghrelin release into the circulation by determining changes in systemic ghrelin concentrations after sham feeding and meal ingestion. Methods: Fifteen normal subjects underwent sham feeding of a bacon and cheese toasted sandwich. Serial blood samples were obtained before and every 5 min for another 30 min during sham feeding and for 30 min after actual meal ingestion. Radioimmunoassay was used to measure plasma ghrelin and pancreatic polypeptide concentrations. Results: During sham feeding, plasma ghrelin concentration increased from 1730 ± 237 to 1917 ± 269 pg/mL (P < 0.05) and plasma pancreatic polypeptide increased from 417 ± 50 to 841 ± 97 pg/mL (P < 0.01). Subsequent meal ingestion was characterized by an increase in pancreatic polypeptide from 782 ± 88 to 1710 ± 119 pg/mL (P < 0.01), but no significant change in ghrelin levels. Conclusions: Plasma ghrelin and pancreatic polypeptide concentrations increase with sham feeding. This suggests a vagal efferent pathway mediating ghrelin release. In contrast to pancreatic polypeptide which rises with actual meal ingestion, ghrelin levels did not change.

Abnormal Ghrelin and Pancreatic Polypeptide Responses in Gastroparesis

Vagal nerve dysfunction has been implicated in the pathogenesis of diabetic gastroparesis, but its role in idiopathic gastroparesis remains uncertain. The incre-ase in pancreatic polypeptide with sham feeding is often used as a measure of vagal integrity. Ghrelin has been suggested to function as an appetite-stimulating hormone from the gut to the brain acting through vagal afferent pathways. Systemic ghrelin also rises in part due to vagal efferent pathways. Alterations in ghrelin and its effects on appetite could play a role in gastroparesis. In this study we aimed [1] to investigate the presence of vagal nerve dysfunction in patients with idiopathic and diabetic gastroparesis and [2] to determine if alterations in ghrelin concentrations occur in gastroparesis. Normal subjects and patients with diabetic, idiopathic, or postsurgical gastroparesis underwent a sham feeding protocol. Serial blood samples were obtained for plasma ghrelin and pancreatic polypeptide. Sham feeding was characterized by an increase in pancreatic polypeptide and ghrelin in normal controls and patients with idiopathic gastroparesis. The changes in pancreatic polypeptide and ghrelin levels in diabetic and postsurgical gastroparesis were significantly less than those in normal subjects. Vagal nerve dysfunction, as evidenced by an impaired pancreatic polypeptide response with sham feeding, is present in diabetic gastroparesis but not idiopathic gastroparesis. Systemic ghrelin concentrations increased with sham feeding in normal subjects and patients with idiopathic gastroparesis but not in diabetic or postsurgical gastroparesis. Vagal function and regulation of ghrelin levels are impaired in diabetic gastroparesis.

The effect of rabeprazole on regional gastric acidity and the postprandial cardia/gastro-oesophageal junction acid layer in normal subjects: a randomized, double-blind, placebo-controlled study.

Background : Postprandial intragastric acidity is not uniform. Postprandial proximal gastric acid pockets have been described in the present study.

Multichannel electrogastrography (EGG) in normal subjects: a multicenter study.

The aim of this study was to record gastric myoelectric activity using multichannel electrogastrography (EGG) and to determine if there are differences due to age, gender, body mass, and study location. In 61 normal subjects from four centers, fasting multichannel EGG was recorded for 1 h, followed by two 1-h postprandial recordings after a test meal. Variables assessed included dominant frequency (DF) and its power, percentage time in 2- to 4-cpm frequency, and percentage slow-wave coupling (%SWC). There were no significant differences in EGG parameters with respect to gender or age. Subjects with a BMI >25 had a decrease in the absolute DF power but a similar increase in the postprandial DF power. Subjects with a BMI >25 had a postprandial decrease in the %SWC compared to those with a BMI <25. There was a decrease in postprandial %SWC in European/Asian centers compared to American centers. In conclusion, multichannel EGG provides assessment of electrical slow-wave coupling in addition to determining dominant frequency, power, and percentage normal rhythm. This multicenter study of normal subjects shows similar multichannel EGG values among different genders and ages. Body mass and ethnicity may impact on some of the EGG values.

Multichannel electrogastrography (EGG) in symptomatic patients: a single center study.

OBJECTIVES:To determine the value of multichannel versus conventional single-channel electrogastrography (EGG) and of an additional postprandial hour recording in symptomatic patients.METHODS:Eighteen normal subjects and 47 patients with upper GI symptoms underwent multichannel EGG with four cutaneous recording electrodes placed on the antral axis. Fasting EGG was recorded for 1 h, followed by meal ingestion, followed by two 1-h postprandial EGG recordings. Variables assessed: (1) dominant frequency (DF) and its power; (2) percent time in normal (2,3,4) cpm frequency; (3) average percent of slow wave coupling (% SWC).RESULTS:Normal values for single-channel EGG were: (1) DF from 2.5–3.3, 2.7–3.5, and 2.6–3.5 cpm in the fasting, first, and second postprandial hours; (2) percentage of time in 2–4 cpm: >50%, >65%, and >65% in the fasting, first, and second postprandial hours. Normal values for percent SWC using multichannel EGG were >50%, >55%, >55% in the fasting, first, and second postprandial hours. In the symptomatic patients, an abnormal 2-h single-channel EGG was obtained in 16 of 47 (34%) patients. Adding an additional 1 h of postprandial recording identified another 4 abnormal patients (20/47 = 43%). With multichannel EGG, abnormal results were obtained in 24 of 47 patients (51%) with the 2-h study. An additional 1 h of postprandial recording identified another 4 patients as abnormal (28/47 = 60%).CONCLUSIONS:Multichannel EGG recording improved the detection of abnormal gastric myoelectric activity in symptomatic patients. This study also demonstrates prolonging the postprandial recording to 2 h increases the diagnostic yield for both single-channel and multichannel EGG.

Effect of prostoglandin inhibition with ketorolac on gastric activity and dyspeptic symptoms in patients with dyspeptic symptoms

Effect of prostoglandin inhibition with ketorolac on gastric activity and dyspeptic symptoms in patients with dyspeptic symptoms

A tool for handling uncertainty in segmenting regions of interest in medical images

We have developed intelligent software tools for handling the uncertainty in delineating the boundaries of complex structures when segmenting regions of interest (ROIs) in medical images. The focus is on efficiently delineating the boundary of complex 3D organ structures, enabling accurate measurement of their structural and physiologic properties. We employ intensity based thresholding algorithms for interactive and semi-automated analysis. We also explore fuzzy-connectedness concepts in order to deal with the uncertainty in identifying organ surrounding tissue and fully automate the segmentation process. We apply the proposed tools to 3D single-photon emission computed tomography (SPECT) images visualising gastric accommodation and emptying and compare their performance to that of the manual segmentation performed by a human expert. We show that the proposed tools achieve highly accurate delineation of the complex three-dimensional gastric boundaries shown in 3D SPECT images. We also demonstrate their ability to obtain accurate volume calculations based on the segmentation procedure, in order to quantitatively assess organ functional properties such as measuring the gastric mass variation.

A 3D image analysis tool for SPECT imaging

We have developed semi-automated and fully-automated tools for the analysis of 3D single-photon emission computed tomography (SPECT) images. The focus is on the efficient boundary delineation of complex 3D structures that enables accurate measurement of their structural and physiologic properties. We employ intensity based thresholding algorithms for interactive and semi-automated analysis. We also explore fuzzy-connectedness concepts for fully automating the segmentation process. We apply the proposed tools to SPECT image data capturing variation of gastric accommodation and emptying. These image analysis tools were developed within the framework of a noninvasive scintigraphic test to measure simultaneously both gastric emptying and gastric volume after ingestion of a solid or a liquid meal. The clinical focus of the particular analysis was to probe associations between gastric accommodation/emptying and functional dyspepsia. Employing the proposed tools, we outline effectively the complex three dimensional gastric boundaries shown in the 3D SPECT images. We also perform accurate volume calculations in order to quantitatively assess the gastric mass variation. This analysis was performed both with the semi-automated and fully-automated tools. The results were validated against manual segmentation performed by a human expert. We believe that the development of an automated segmentation tool for SPECT imaging of the gastric volume variability will allow for other new applications of SPECT imaging where there is a need to evaluate complex organ function or tumor masses.