An anatomical study of the anterior wall of the hypopharyngeal and the cervical esophageal junction.

OBJECTIVE: The upper esophageal sphincter plays a significant role by forming a physical barrier at the junction of the hypopharynx and the cervical esophagus. As few studies have focused on the ventral aspect of this junction, the contribution of the anterior wall of the cervical esophagus to upper esophageal sphincter function remains unknown. The purpose of this study was to examine the muscle fibers' arrangement at the junction, especially of those forming its anterior wall. METHODS: Thirteen specimens from 13 Japanese cadavers were analyzed. Six specimens were dissected macroscopically, while the remaining seven were examined histologically. RESULTS: The outer longitudinal layer of the proximal esophagus was well-developed anterolaterally. The uppermost fibers of the inner circular layer of the esophagus ascended longitudinally. The anterolateral part of the outer longitudinal layer and the uppermost region of the inner circular layer were continuous with the median tendinous band, in turn reaching superior to the cricoid cartilage. Histological analysis showed that the tendinous band was also continuous with the superior part of the perichondrium of the cricoid cartilage and with the aponeurosis of the transverse and oblique arytenoids. CONCLUSION: The well-developed anterolateral region of the outer longitudinal layer and the uppermost fibers of the inner circular layer were continuous with the median tendinous band, which reached superior to the cricoid cartilage. The contraction of the proximal esophagus may result in protrusion of the anteromedian esophageal wall into the lumen, thereby supporting the closure of the upper esophageal sphincter.

Morphology of the Upper Esophageal Sphincter or Cricopharyngeus Muscle Revisited: A Study Using Adult and Fetal Specimens.

Histological examination of specimens from 22 donated elderly cadavers and 15 human fetuses revealed that the cricopharyngeus muscle (CPM) provided (1) posterior circular muscle fibers adjacent to the external aspect of the uppermost esophageal circular muscle and (2) a thin anterior sling connecting to that same muscle. Another thick lateral bundle of longitudinal muscle originated independently from a fascia covering the posterior cricoarytenoideus muscle, extended laterally and posteriorly, and occupied a space after the CPM had disappeared at the anterolateral angle of the esophagus below the cricoid. The thick fascia contained abundant elastic fibers along the internal surface of the pharyngeal constrictors (posteromedial elastic lamina), but was interrupted or discontinued near the cricoid origin of the CPM. As no submucosal smooth muscles or elastic fibers were connected to it, the CPM did not accompany a specific elastic structure at the interface between the pharyngeal and esophageal muscles. In fetuses, the medial half of the CPM was inserted into the cricoid while the lateral half continued to the sternothyroideus muscle or ended at a fascia covering the cricothyroideus. These anterolateral ends provided a mechanical load for longitudinal growth of the pharyngeal constrictors. Consequently, the CPM was unlikely to develop and grow to form the upper esophageal sphincter, and the muscle bundle crossing the lateral aspect of the pharyngo-esophageal junction appeared to have a secondary passive role as a sphincter. This situation contrasts with that of another sphincter in the human body formed from striated muscle. Clin. Anat., 33:782-794, 2020. © 2019 Wiley Periodicals, Inc.

Three-dimensional analysis of the human pharyngoesophageal sphincter.

OBJECTIVES: Dysfunction of the pharyngoesophageal segment (PES) is a common cause of oropharyngeal dysphagia. Surgical dilation of the PES uses cylindrical dilators that expand radially in a circular shape. Animal studies, however, suggest that the PES is kidney-shaped. The purpose of this investigation was to evaluate the 3D shape of the human PES with a novel casting method. METHODS: A platinum-cured liquid silicone polymer was infused under pressure into the upper aerodigestive tract of nine fresh human cadavers to construct 3D casts of the maximally distended PES. Cross-sectional and volumetric analysis were performed using computed tomography and serial sectioning of the models. Canonical variate analysis was used to identify the shape features that best distinguishes the PES from the cervical esophagus. RESULTS: The mean age of the cadavers was 77.9 (SD ± 10.6) years, with 67% women. Analysis of the casts confirms that the human PES possesses a kidney-shaped structure at maximal distention, which is discretely different from the adjacent esophagus (P < 0.001). The posterior body of the cricoid cartilage formed the anterior wall of the PES, which provided a rigid structure responsible for preservation of the kidney shape during distention. The diameter of the maximally distended PES at the cricopharyngeus was highly variable (range = 0.86-4.68 cm2 ; SD = 1.33 cm2 ). CONCLUSION: The data suggest that the human PES is not round and that targeted expansion at the level of the cricopharyngeus with an eccentrically shaped dilator may provide improved distention. LEVEL OF EVIDENCE: 4 Laryngoscope, 2019.

Defining pharyngeal contractile integral during high-resolution manometry in neonates: a neuromotor marker of pharyngeal vigor.

BACKGROUND: Pharyngeal contractility is critical for safe bolus propulsion. Pharyngeal contractile vigor can be measured by Pharyngeal Contractile Integral (PhCI): product of mean pharyngeal contractile amplitude, length, and duration. We characterized PhCI in neonates and examined the hypothesis that PhCI differs with mode of stimulation. METHODS: Nineteen neonates born at 38.6 (34-41) weeks gestation were evaluated at 42.9 (40.4-44.0) weeks postmenstrual age using high-resolution manometry (HRM). PhCI was calculated using: (a) Conventional and (b) Automated Swallow Detection algorithm (ASDA) methods. Contractility metrics of all pharyngeal regions were examined using mixed statistical models during spontaneous and adaptive state (pharyngeal and oral stimulus) swallowing. RESULTS: PhCI of oral stimuli swallows were distinct from pharyngeal stimuli and spontaneous swallows (P < 0.05). Correlation between conventional and ASDA methods was high (P < 0.001). PhCI increased with swallows for pharyngeal stimulation (P < 0.05) but remained stable for swallows with oral stimulation. PhCI differed between proximal and distal pharynx (P < 0.001). CONCLUSIONS: PhCI is a novel reliable metric capable of distinguishing (1) proximal and distal pharyngeal activity, (2) effects of oral and pharyngeal stimulation, and (3) effects of prolonged stimulation. Changes in pharyngeal contractility with maturation, disease, and therapies can be examined with PhCI.

Characterization of swallow modulation in response to bolus volume in healthy subjects accounting for catheter diameter.

OBJECTIVES/HYPOTHESIS: Characterization of the pharyngeal swallow response to volume challenges is important for swallowing function assessment. The diameter of the pressure-impedance recording catheter may influence these results. In this study, we captured key physiological swallow measures in response to bolus volume utilizing recordings acquired by two catheters of different diameter. STUDY DESIGN: Ten healthy adults underwent repeat investigations with 8- and 10-Fr catheters. Liquid bolus swallows of volumes 2.5, 5, 10, 20, and 30 mL were recorded. Measures indicative of distension, contractility, and flow timing were assessed. METHODS: Pressure-impedance recordings with pressure-flow analysis were used to capture key distension, contractility, and pressure-flow timing parameters. RESULTS: Larger bolus volumes increased upper esophageal sphincter distension diameter (P < .001) and distension pressures within the hypopharynx and upper esophageal sphincter (P < .05). Bolus flow timing measures were longer, particularly latency of bolus propulsion ahead of the pharyngeal stripping wave (P < .001). Use of a larger-diameter catheter produced higher occlusive pressures, namely upper esophageal sphincter basal pressure (P < .005) and upper esophageal sphincter postdeglutitive pressure peak (P < .001). CONCLUSIONS: The bolus volume swallowed changed measurements indicative of distension pressure, luminal diameter, and pressure-flow timing; this is physiologically consistent with swallow modulation to accommodate larger, faster-flowing boluses. Additionally, catheter diameter predominantly affects lumen occlusive pressures. Appropriate physiological interpretation of the pressure-impedance recordings of pharyngeal swallowing requires consideration of the effects of volume and catheter diameter. LEVEL OF EVIDENCE: NA. Laryngoscope, 128:1328-1334, 2018.

The normal squamocolumnar junction is circumferentially even and minimal irregularities are manifestations of gastroesophageal acid reflux.

BACKGROUND: The macroscopic appearance of the normal squamocolumnar junction (SCJ) is often described as serrated with short projections of columnar mucosa that extend into the esophagus. As studies of the normal SCJ are sparse, the aim of this study was to test the hypothesis that the normal SCJ is even and that irregularities are manifestations of acid reflux. METHOD: Fifty asymptomatic subjects and 149 patients with symptoms suggestive of gastroesophageal reflux disease underwent endoscopy and 48-h pH monitoring with a pH electrode positioned immediately above the SCJ. The shape of the SCJ was assessed according to the Z-line appearance classification and correlated with clinical characteristics and the degree of esophageal acid exposure in the most distal esophagus. RESULTS: Even SCJs without irregularities were significantly more common in asymptomatic subjects compared with patients (50% versus 10%, p < .001) and were never found in patients with erosive esophagitis. The median degree of distal esophageal acid exposure in individuals with an even SCJ was within normal limits. With increasing degree of irregularity of the SCJ, the frequency and duration of reflux episodes, the degree of distal esophageal acid exposure, and the prevalence of abnormal acid exposure increased progressively and significantly. CONCLUSION: The shape of the normal SCJ is even and also minimal irregularities are a consequence of acid reflux, likely due to the formation of small areas of metaplastic columnar mucosa.

Normal and abnormal physiology, pharmacology, and anatomy of the gastroesophageal junction high-pressure zone.

The high-pressure zone of the gastroesophageal junction acts as a multifunctional valve that comprises different groups of smooth muscles located in the distal esophagus and the proximal stomach, in addition to the extrinsic crural diaphragm, composed of skeletal muscle. In this review article, we evaluate the current literature with respect to human subjects, discussing the anatomic locations and physiologic and pharmacologic processes controlling these muscles. These muscles work individually and as a group to prevent reflux of gastric contents while allowing anterograde passage of food and liquid and retrograde passage of gas. We also reviewed new findings with respect to abnormalities that are permissive of reflux of gastric contents into the esophagus, which may lead to gastroesophageal reflux disease.

[Anatomy of the upper esophageal sphincter]. / Anatomie des oberen Ösophagussphinkters.

The upper esophageal sphincter (UES) forms a barrier between the pharynx and the esophagus. When closed, the barrier function serves to prevent reflux and aerophagia; when open, swallowing, belching and vomiting are possible. The closing muscles include caudal parts of the inferior pharyngeal sphincter and cranial parts of the upper esophagus musculature. Sphincter opening is achieved by muscles that insert from the outside to connect to the larynx and pharynx in the sphincter region. The closing muscles are innervated by branches of the glossopharyngeal and vagal nerves, and central control is probably mediated by several reflexes. This article presents an overview of the current understanding of the complex UES anatomy.

The upper esophageal sphincter is not round: a pilot study evaluating a novel, physiology-based approach to upper esophageal sphincter dilation.

OBJECTIVES: Recent basic science investigations have suggested that the upper esophageal sphincter (UES), in cross section, is not round, but that it more closely approximates a kidney shape. Dilation with simultaneous use of two cylindrical dilators provides a novel, physiology-based approach to UES distention. We evaluated the initial safety and efficacy of UES dilation with simultaneous use of two controlled radial expansion balloon dilators. METHODS: Using a computerized database, we reviewed the charts of all persons who underwent UES dilation with simultaneous use of two radial expansion balloon dilators between December 1, 2011, and March 15, 2012. Information regarding patient demographics, indications, technique, and complications was abstracted. Self-reported swallowing impairment was assessed with the validated 10-item Eating Assessment Tool (EAT-10). RESULTS: Ten individuals underwent simultaneous dilation with two dilators. Their mean age was 65 years (SD, 14 years), and 7 (70%) of them were male. The indications for dilation were radiation-induced UES stenosis (50%), cricopharyngeus muscle dysfunction (30%), upper esophageal web (10%), and anastomotic stricture (10%). After the double-balloon dilation, no complications were reported. The mean EAT-10 score improved significantly, from 34.3 (SD, 13.5) to 16.7 (SD, 8.4), after the simultaneous dilation (p = 0.003). CONCLUSIONS: Pilot data suggest that simultaneous dilation of the UES with two controlled radial expansion balloon dilators is feasible, safe, and effective. Future investigation is necessary to confirm the safety of this technique in a larger cohort and to use objective measures of efficacy to compare the technique to conventional dilation with a single dilator.

Dynamic magnetic resonance imaging of the pharynx during deglutition.

OBJECTIVES: We utilized dynamic magnetic resonance imaging to visualize the pharynx and upper esophageal segment in normal, healthy subjects. METHODS: A 3-T scanner with a 4-channel head coil and a dual-channel neck coil was used to obtain high-speed magnetic resonance images of subjects who were swallowing liquids and pudding. Ninety sequential images were acquired with a temporal resolution of 113 ms. Imaging was performed in axial planes at the levels of the oropharynx and the pharyngoesophageal segment. The images were then analyzed for variables related to alterations in the area of the pharynx and pharyngoesophageal segment during swallowing, as well as temporal measures related to these structures. RESULTS: All subjects tolerated the study protocol without complaint. Changes in the area of the pharyngeal wall lumen and temporal measurements were consistent within and between subjects. The inter-rater and intra-rater reliabilities for the measurement tool were excellent. CONCLUSIONS: Dynamic magnetic resonance imaging of the swallow sequence is both feasible and reliable and may eventually complement currently used diagnostic methods, as it adds substantive information.

[Clinical anatomy of the esophagogastric junction]. / Anatomia clinica a jonctiunii eso-gastrice.

UNLABELLED: The esophagogastric junction is a controversial anatomical area, due to its sphincteric mechanism which does not show an obvious anatomical basis. The aim of this study is to investigate the anatomical components that endoscopically indicate the mucosal esophagogastric junction in hiatal hernia patients. MATERIAL AND METHODS: The esophagogastric junction was investigated in 27 hiatal hernia patients undergoing surgery. Hiatal hernia is an extension of the stomach situated between the esophagogastric junction and the diaphragmatic indentation. The following types of hiatal hernia were found: sliding hiatal hernia (type I) in 4 patients (14.81%), rolling hiatal hernia (type II) in 2 (7.4%), mixed hiatal hernia (type III) in 12 (44.44%), type IV hiatal hernia in 4 (14.81%) and recurrent hiatal hernia in 5 (18.51%). Of the 27 hiatal hernia patients, 8 (29.6%) were operated using classical procedures: laparotomy--6 (75%) and laparoscopic surgery--2 (25%). RESULTS: The angle of His cannot be used for marking the mucosal esophagogastric junction due to the severe damage of the lower esophageal sphincter in hiatal hernia patients. The squamocolumnar junction is displaced in hiatal hernia patients and was not an option for the study group. The distal end of the esophageal longitudinal palisading vessels needs medication (proton pump inhibitors that reduce the gastric acid production), in order to enhance the visibility of these vessels. The proximal end of gastric longitudinal mucosal folds proved to be the most reliable site to identify endoscopically the mucosal esophagogastric junction. CONCLUSIONS: The anatomical structure of the esophagogastric junction differs in hiatal hernia patients and these peculiarities are very important in surgery.

Structural analysis of muscles elevating the hyolaryngeal complex.

A critical event of pharyngeal swallowing is the elevation of the hyolaryngeal complex to open the upper esophageal sphincter. Current swallowing theory assigns this function to the submental and thyrohyoid muscles. However, the attachments of the long pharyngeal muscles indicate that they could contribute to this function, yet their role is uninvestigated in humans. In addition, there is evidence the posterior digastric and stylohyoid contribute to hyoid elevation. A cadaver model was used to document the structural properties of muscles. These properties were used to model muscle groups as force vectors and analyze their potential for hyolaryngeal elevation. Vector magnitude was determined using physiological cross-sectional areas (PCSAs) of muscles calculated from structural properties of muscle taken from 12 hemisected cadaver specimens. Vector direction (lines of action) was calculated from the three-dimensional coordinates of muscle attachment sites. Unit force vectors in the superior direction of submental, suprahyoid (which includes the submental muscles), long pharyngeal, and thyrohyoid muscles were derived and compared by an analysis of variance (ANOVA) to document each muscle's potential contribution to hyolaryngeal elevation. An ANOVA with Tukey HSD post hoc analysis of unit force vectors showed no statistically significant difference between the submental (0.92 ± 0.24 cm(2)) and long pharyngeal (0.73 ± 0.20 cm(2)) muscles. Both demonstrated greater potential to elevate the hyolaryngeal complex than the thyrohyoid (0.49 ± 0.18 cm(2)), with P < 0.01 and P < 0.05, respectively. The suprahyoid muscles (1.52 ± 0.35 cm(2)) demonstrated the greatest potential to elevate the hyolaryngeal complex: greater than both the long pharyngeal muscles (P < 0.01) and the thyrohyoid (P < 0.01). The submental and thyrohyoid muscles by convention are thought to elevate the hyolaryngeal complex. This study demonstrates that structurally the long pharyngeal muscles have similar potential to contribute to this critical function, with the suprahyoid muscles having the greatest potential. If verified by functional data, these findings would amend current swallowing theory.

General anatomy of the esophagus.

This article reviews the embryology and general anatomy of the esophagus, including the topography and relationships of the esophagus to surrounding structures. The esophagus is the only internal organ that traverses 3 body cavities, and a complete understanding of the anatomy and anatomic relationships of the esophagus in each area is essential for surgeons who address esophageal disorders. Details regarding the normal histology and basic function of the esophagus are also provided.

Anatomic-manometric correlation of the upper esophageal sphincter: a concurrent US and manometry study.

BACKGROUND: The pharyngoesophageal segment commonly referred to as the upper esophageal sphincter (UES) generates a high-pressure zone (HPZ) between the pharynx and the esophagus. However, the exact anatomical components of the UES-HPZ remain incompletely determined. OBJECTIVE: To systematically define the US signature of various components of the pharyngoesophageal junction and to determine how these structures contribute to the development of the UES-HPZ. DESIGN: Prospective, experimental study. SETTING: Tertiary Academic Medical Center. PATIENTS: This study involved 18 healthy volunteers. INTERVENTION: We studied 5 participants by using a high-frequency US miniprobe (US-MP) and concurrent fluoroscopy and another 13 participants by using the US-MP and concurrent manometry. MAIN OUTCOME MEASUREMENTS: Relative contribution of various muscles in the UES-HPZ. RESULTS: Manometrically, the UES-HPZ had a median length of 4.0 cm (range 3.0-4.5 cm). A C-shaped muscle, believed to represent the cricopharyngeus muscle, was observed for a median length of 3.5 cm (range 2.0-4.0 cm). The oval configuration representing the esophageal contribution to the UES was seen in 10 of 13 participants (77%) at the distal HPZ (esophagus to UES transition zone). The flat configuration of the inferior constrictor muscle was noted in 7 of 13 participants (54%) at the proximal HPZ (UES to pharynx transition zone). There were 4 to 5 wall layers versus 3 layers in the distal and proximal HPZ, respectively. The mean (+/- SD) muscle thickness was relatively constant along the length of the UES-HPZ. LIMITATIONS: Air artifacts in the UES-HPZ. CONCLUSION: The configuration and layers of the UES-HPZ vary along its length. The upper esophagus is a significant contributor to the distal UES-HPZ.

The normal anatomy around the oesophagogastric junction: an endoscopic view.

Where the oesophagus ends and the stomach begins has been a bone of contention for decades between the histologist, physiologist, gastroenterologist, radiologist and surgeon. The oesophagogastric junction (OGJ) is an important anatomical region because of its essential functions in relation to swallowing and as a site of structural defects, inflammation, metaplasia and neoplasia. The location of the diaphragmatic hiatus in relation to the distal oesophagus, the level of the squamocolumnar mucosal junction (SCJ), the location of the distal margin of the mucosal palisade veins and the proximal margin of the gastric mucosal folds are features that permit an accurate endoscopic diagnosis of hiatal hernia and reflux sequelae, including even a minimal extent for Barrett's oesophagus. The physiological OGJ region can be considered to be between the rosette of the lower oesophageal sphincter (LOS) and the angle of His. The most reliable benchmarks for the precise mural OGJ that can be identified during endoscopy are the levels of the cephalad margins of the linear gastric mucosal folds, viewed with the lumen deflated as much as possible, that are juxtaposed to the level of the caudad extent of the oesophageal mucosal palisade veins.

The transnasal esophagoscopy documentation dilemma.

OBJECTIVE: To determine radiographically the anatomic length difference between the nasal and oral aerodigestive tracts and to clarify gaps in the literature regarding standardized landmark measurements and documentation techniques in transnasal esophagoscopy, as opposed to traditional transoral esophagoscopy. STUDY DESIGN: This is a prospective radiographic cohort study. METHODS: Digital computerized tomography measurement techniques were used to determine the difference in length between the nasal and oral aerodigestive tracts. Using sagittal plane images from consecutive patients, the mean nares-cricoid (NC) distance, upper incisor-cricoid (IC) distance, and their mean differences were determined. Male, female, and overall distances and differences were calculated. Standard deviations, 95% confidence intervals, and 90% prediction intervals were also calculated. Mean difference data were applied to reported standard oral esophagoscopy landmark measurements to convert to standard landmark measurements from the nares. RESULTS: Overall mean NC and IC distances were 175.4 mm and 147.5 mm, respectively. For males, these mean distances were 185.5 mm and 155.0 mm, respectively. For females, these mean distances were 165.3 mm and 140.0 mm, respectively. Overall mean NC to IC difference was 27.9 mm. The mean NC to IC difference for males and females was 30.5 mm and 25.2 mm, respectively. CONCLUSIONS: Historically, landmark and report measurements in esophagoscopy have been measured and standardized from the upper incisor. This study demonstrates and clarifies the inherent anatomic length difference of the nasal and oral aerodigestive tracts and the resultant documentation dilemma produced by transnasal esophagoscopy techniques. These data provide easy conversion of esophagoscopy measurements reported from the incisors or nares, providing better communication between endoscopists of different disciplines and techniques.

Anatomic continuity of longitudinal pharyngeal and esophageal muscles.

OBJECTIVES: The pharyngeal and esophageal shortenings during deglutition are attributable to longitudinal muscle contraction. The two shortenings may be independent events because the longitudinal pharyngeal and esophageal muscular insertions are believed to be separated from each other. The aim of this study was to investigate the superior attachments of the longitudinal esophageal muscle. STUDY DESIGN: Prospective. METHODS: With use of dissection, sectional anatomy, and confocal microscopy, 30 adult cadavers were examined in this study. RESULTS: We found that the longitudinal esophageal muscle fibers had multiple superior insertions. Some of the fibers were continuous with the longitudinal pharyngeal muscles and merged with a membrane-like fascia that anchored the pharyngoesophageal wall to the thyroid cartilage. CONCLUSIONS: This study demonstrates that the longitudinal pharyngeal and esophageal muscle fibers are continuous with each other and are integrated with fibrous and cartilaginous structures. Such anatomic integrity at the pharyngoesophageal junction is important for the function of the upper esophageal sphincter.

Is the anatomical protrusion on the posterior hypopharyngeal wall associated with cadavers of only the elderly?

Cricopharyngeal bars are commonly seen on a barium swallow radiologic examination and represent the failure of the cricopharyngeus to relax. Traditionally, the bars have been considered as functional or physiologic protrusions. Recently, anatomical cricopharyngeal protrusion has been found in about 30% of cadavers of the elderly, suggesting that such a structural change may become a physical barrier that affects the normal deglutition in a living person. This suggests that such a radiographic finding should be carefully considered when interpreting radiologic and manometrical examinations and managing dysphagia of the elderly. However, the finding of the anatomical cricopharyngeal protrusion was based on the observation of cadavers of the elderly (mean age = 77 years). The aim of this study was to further investigate whether such an anatomical cricopharyngeal protrusion exists in cadavers of other ages. Using the dissection method, we examined 63 human cadavers that were divided into three age groups: young adult (6 females and 10 males, age = 16-24 years old), adult (8 females and 23 males, age = 25-64 years old), and early elderly (5 females and 11 males, age = 65-69 years old). We found that 57 of the 63 cadavers had a smooth mucosal surface on the posterior hypopharyngeal and upper esophageal wall. A slightly thickened posterior muscular wall was observed at the cricoid level in six cadavers (five from the adult group and one from the early elderly group), but its boundary was not clearly identified. Taking the previous reports together, our results suggest that an anatomical cricopharyngeal protrusion is closely associated with the aging process.

Generation of nitric oxide in the opossum lower esophageal sphincter during physiological experimentation.

Lipopolysaccharide (LPS), given in vivo, modulates opossum esophageal motor functions by inducing the inducible nitric oxide synthase (iNOS), which increases nitric oxide (NO) production. Superoxide, a NO scavenger, is generated during this endotoxemia. Superoxide is cleared by superoxide dismutase (SOD) and catalase (CAT) to protect the physiological function of NO. This study examined whether lower esophageal sphincter (LES) motility, NO release, and iNOS and nitrotyrosine accumulation in the LES are affected by LPS in vitro. Muscle strips from the opossum LES were placed in tissue baths containing oxygenated Krebs buffer. NO release was measured with a chemiluminescence NOx analyzer, and Western blots were performed to analyze iNOS and nitrotyrosine production. The percent change in resting LES tone after a 6-hour exposure to LPS was significantly increased compared to pretreatment values. The percent LES relaxation upon electrical stimulation was significantly decreased in the control group at 6 hours, indicating that the LPS treatment had an effect. The NO concentration in the tissue bath of LPS- treated muscle without nerve stimulation was significantly less than that of LPS treatment combined with SOD/CAT or SOD/CAT alone. iNOS and nitrotyrosine were detectable and increased over time in the LES muscle of both the control and LPS-treated groups. Antioxidant enzymes may play a role in regulating NO-mediated neuromuscular functions in the LES.

Generation of Nitric Oxide in the Opossum Lower Esophageal Sphincter during Physiological Experimentation

Lipopolysaccharide (LPS), given in vivo, modulates opossum esophageal motor functions by inducing the inducible nitric oxide synthase (iNOS), which increases nitric oxide (NO) production. Superoxide, a NO scavenger, is generated during this endotoxemia. Superoxide is cleared by superoxide dismutase (SOD) and catalase (CAT) to protect the physiological function of NO. This study examined whether lower esophageal sphincter (LES) motility, NO release, and iNOS and nitrotyrosine accumulation in the LES are affected by LPS in vitro. Muscle strips from the opossum LES were placed in tissue baths containing oxygenated Krebs buffer. NO release was measured with a chemiluminescence NOx analyzer, and Western blots were performed to analyze iNOS and nitrotyrosine production. The percent change in resting LES tone after a 6-hour exposure to LPS was significantly increased compared to pretreatment values. The percent LES relaxation upon electrical stimulation was significantly decreased in the control group at 6 hours, indicating that the LPS treatment had an effect. The NO concentration in the tissue bath of LPS-treated muscle without nerve stimulation was significantly less than that of LPS treatment combined with SOD/CAT or SOD/CAT alone. iNOS and nitrotyrosine were detectable and increased over time in the LES muscle of both the control and LPS-treated groups. Antioxidant enzymes may play a role in regulating NO-mediated neuromuscular functions in the LES.