AGA Abstracts impedance was measured over a period of ≥30 seconds and not containing any swallows or gastroesophageal reflux episodes. Baseline impedance was calculated over four segments (3, 5, 7 and 15 cm above the LES). Results were expressed as median with interquartile range (25 th -75 th percentile). Results: In 23 of 25 children both pre and postoperative 24- h tracings were successfully completed. LARS reduced acid exposure time from 8.5% (6.0- 16.2%) to 0.8% (0.2-2.8%), p<0.001. Distal baseline impedance increased after LARS from 2445 V (1147-3277 V) to 3792 V (3087-4700 V), p<0.001. Baseline impedance also increased at segments 5 cm (from 3275 V (1394 -3581 V) to 4234 V (3324 -5140 V), p= 0.001) and 7 cm above the LES (from 3369 V (1731 -4213 V) to 3917 V (3397 -4914 V), p=0.01), but not in the proximal segment (from 3116 V (2539 -4071 V) to 3379 V (3019 -4675 V), p=0.06). Prior to LARS baseline impedance showed a negative correlation with acid exposure time in both the distal and proximal segment (distal (+3 cm): r: -0.76, p<0.001 and proximal (+15 cm): r:-0.62, p=0.001). Conclusion: Reduction of acid exposure by laparoscopic antireflux surgery results in a significant increase in baseline impedance in children with GERD. We suggest that this may represent recovery of mucosal integrity after LARS. Mo1915 Analysis of Solid Swallows At High Resolution Manometry Unmasks Impaired Peristalsis in NERD Patients With Delayed Reflux Clearance Mentore Ribolsi, Paola Balestrieri, Fabiola De Biasio, Michele Cicala Background: Esophageal manometry with liquid swallows has poor sensitivity in demonstrat- ing impairment of esophageal motility in GERD patients. High resolution manometry (HRM) is considered the gold standard in the study of esophageal motor disorders. Few studies evaluating the esophageal motility during solid bolus swallows are available. Aim: To compar- atively assess the HRM findings during liquid and solid swallows and to evaluate their impact on reflux clearance in GERD patients. Method: 22 NERD patients with typical symptoms, without hiatal hernia, and 15 healthy volunteers (HVs), underwent HRM combined with impedance (HRM-MI), before and during a 10-minutes solid meal (bread) in a sitting position. Before meal, a total of 10 liquid (5ml) swallows, at 30-sec intervals, were performed. A catheter with 36 solid state pressure sensors and 9 impedance segments was used. Following HRM-MI, patients underwent 24h impedance-pH monitoring (MII-pH). The distal contractile integral (DCI), distal latency (DL) and contractile front velocity (CFV) were calculated according to the Chicago criteria, for both liquid and solid swallows. Esophageal bolus (liquid and solid) clearance was assessed by means of the total bolus transit time (TBTT). The occurrence of >2cm breaks was assessed in the 20 mmHg isobaric contour. Reflux clearing time (RCT) was calculated in the MII-pH tracings. Results: Of the 22 patients, 2 with normal MII-pH findings and 5 with hyper- or hypocontractile disorders were excluded. Mean DCI, DL, CFV and TBTT values are in Table. In all individuals, DL and TBTT were significantly higher during solid, whilst CFV was higher during liquid swallows. Four HVs displayed, during the liquid swallows, less than two breaks >2cm. In all HVs (100%) and in 9 out of 15 (60%) patients (p<0.05) the mean DCI values were higher during solid swallows respect to liquid swallows (1685±546 vs 1044±324, p<0.01 and 1579±334 vs 971±244, p<0.01, respectively). In the remaining 6 patients, mean DCI values for solid and liquid swallows were comparable (1203±433 vs 1021±327). The 9 patients with higher DCI presented breaks in 15/90 (17%) liquid swallows and in 28/207 (14%) solid swallows; mean RCT at MII-pH was 12.6±2.7sec; 2/9 displayed abnormal AET. On the other hand, the 6 patients with lower DCI presented breaks in 14/60 (23%) liquid swallows and in 62/167 (37%) solid swallows (p: ns and p<0.001); mean RCT at MII-pH was 15.6±2.2sec (p<0.05 respect to Group 1); 4/6 displayed abnormal AET. Conclusions: HRM analysis of solid swallows reveals motor abnormalities not detected during liquid swallows. Impaired peristal- sis, assessed during solid swallows, may play a role in delaying reflux clearance in NERD patients. Table *p<0.01 Mo1916 The Transcription, Translation and Activation of MLCK Maybe Participate in Regulating the Esophageal Epithelial Barrier of GERD Patients Jiacheng Tan, Yu R. Tang, Ying Wang, Nina Zhang, Xiaomeng Sun, Ting Yu, Lin Lin Background/Aims: Dilated intercellular space (DIS) represents the disrupted esophageal epithelial barrier in patients with gastroesophageal reflux disease (GERD). However, the forming mechanism of DIS remains unclear. Myosin light chain kinase (MLCK) and the structural tight junction (TJ) proteins (claudin-1, occludin and ZO-1) were considered to be important in regulating the intestine epithelial barrier. Our present research aims to explore whether MLCK and the structural TJ proteins participate in the forming mechanism of DIS. Methods: According to the inclusion criteria and exclusion criteria, 82 subjects were recruited and all of them signed informed consent forms. Upon the questionnaire survey and the upper gastrointestinal endoscopy, the participants were divided into control, non- erosive reflux disease (NERD) and reflux esophagitis (RE) groups. The squamous mucosa without erosion at 5 cm above the gastro-oesophageal junction was biopsied to perform the experiments. DIS in the esophageal epithelium was observed by transmission electron microscopy (TEM). The activity of MLCK was represented by myosin light chain (MLC) phosphorylation. The expression and phosphorylation of MLCK, MLC and extracellular signal regulated kinases 1/2 (ERK1/2) were examined by western blotting (WB). The intracellular distribution and expression of the structural TJproteins (claudin-1, occludin and ZO-1) were S-738 AGA Abstracts assessed by immunohistochemical (IHC) staining and WB. Real-time PCR was used to analyze the mRNA expression of MLCK, claudin-1, occludin and ZO-1. Results: Compared with control group, DIS occurred in NERD and RE esophagus. The expression and activity of MLCK increased in the esophageal epithelium of NERD and RE patients. Relevance between DIS and the expression and activity of MLCK were shown by correlation analysis. The phosphorylation level of ERK1/2 was also up-regulated in NERD and RE group. Claudin- 1, occludin and ZO-1 were shown to be redistributed and down-regulated by using IHC staining, WB and Real-time PCR. The occurrence of DIS was noticed to be accompanied with the variation of TJ proteins. Although significant differences were found when compared NERD and RE groups with control group, no significant difference was noticed between NERD and RE groups. Conclusion: Our data indicate that the transcription, translation and activation of MLCK participate in regulating TJ proteins in the esophageal epithelium of GERD patients. The process may be mediated by ERK1/2 signal transduction. This may be the forming mechanism of DIS and cause the esophageal epithelial barrier dysfunction in GERD patients. Since TEM examination is costly, MLCK and TJ proteins could be considered as sensitive markers of GERD instead of DIS in the future. Key Words: GERD, dilated intercellular space, myosin light chain kinase, tight junction Mo1917 Melatonin Protects the Esophageal Epithelial Barrier Function by Protecting the Structural TJ Proteins Through ERK-MLCK Signal Transduction Jiacheng Tan, Yu R. Tang, Ying Wang, Nina Zhang, Xiaomeng Sun, Ting Yu, Lin Lin Background/Aims: The reflux of acid from the stomach makes bad effects on the esophageal epithelium. Melatonin is reported to protect the esophageal mucosa. However, the protecting mechanism of melatonin remains unclear. Myosin light chain kinase (MLCK) and the struc- tural tight junction (TJ) proteins (claudin-1, occludin and ZO-1) were considered to be important in regulating the intestine epithelial barrier. Our present research aims to explore whether MLCK and the structural TJ proteins participate in the protecting mechanism of melatonin. Methods: A non-neoplastic esophageal keratinocyte derived cell line, Het-1A, was used in the present study. We treated the Het-1A cells in different groups: blank, DMSO, DMSO+acid, DMSO+PD98059 (an ERK1/2 inhibitor) +acid, DMSO+melatonin+acid, DMSO+melatonin+PD98059+acid. The Het-1A monolayer barrier function was investigated by measuring transepithelial resistance (TER) and FITC-dextran paracellular permeation. The activity of myosin light chain kinase (MLCK) was represented by the phosphorylation level of myosin light chain (MLC). The expression and phosphorylation of MLCK, MLC and ERK were examined by western blot (WB) analysis. Immunofluorescence (IF) staining was used to examine the cellular distribution of the tight junction (TJ) structural proteins (claudin- 1, occludin and ZO-1). WB was used to analyze the expression levels of claudin-1, occludin and ZO-1. Results: Upon acid treatment, the Het-1A monolayer barrier function was dis- rupted. The transcription, expression and activity of MLCK were up-regulated by acid through ERK1/2 signal transduction. The structural TJ proteins (claudin-1, occludin and ZO-1) were redistributed and down-regulated after acid treatment. The effects of acid were reversed when the Het-1A monolayer was pretreated with melatonin or PD98059 or melatonin+PD98059. The Het-1A monolayer barrier function as well as the structural TJ proteins (claudin-1, occludin and ZO-1) were protected by measuring the permeability of Het-1A monolayer and the expression and location of TJ proteins. The expression and phosphorylation of MLCK and ERK1/2 were down-regulated after pretreatment with melato- nin or PD98059 or melatonin+PD98059. There were no significant difference between the melatonin-PD98059-acid-treated Het-1A monolayer compared with the PD98059-acid- treated and melatonin-acid-treated Het-1A monolayer. Conclusion: Melatonin protects the esophageal epithelial barrier by protecting TJ structural proteins (claudin-1, occludin and ZO-1). The effect of melatonin is mediated by suppressing the transcription, translation and activity of MLCK through ERK1/2 signal transduction. These findings inspire us that melato- nin has the potential value of clinical application in GERD treatment. Key Words: melatonin, esophageal epithelial barrier, myosin light chain kinase, tight junction Mo1918 Shift Work and Social Jetlag Negatively Impacts GERD Associated Quality of Life Shifali Arora, James Philip G. Esteban, Louis Fogg, Ali Keshavarzian, Rana R. Abraham Background Shift work is a well-known form of circadian disruption. It is associated with increased rates of disease including metabolic syndrome, hypertension, obesity and GERD. The correlation between sleep disruption and GERD is well established however the relation- ship between GERD and circadian disruption is not defined. The aims of this study are to: 1) define circadian disruption in shift workers, 2) define the relationship between circadian disruption and GERD symptom severity and quality of life (QOL), and 3) determine if variation in shifts effects GERD symptom severity and QOL. Methodology Sample: Nurses working morning, evening, night, or a combination of shifts from Rush University Hospitals were asked to participate. Procedures: Participants were emailed a link to a survey compiled of validated questionnaires. Measure: The key questionnaires included the Quality of Life in Reflux and Dyspepsia (QOLRAD) and the Munich Chronotype Questionnaire (MCTQ). MCTQ measures social jet lag, defined as a greater than 2 hour difference between midsleep during work compared to free days. Data Analysis: Correlations were tested by the Pearson Coefficient. Comparisons between the means were tested by ANOVA. Results There were 103 respondents: 90% of participants were female, 48% were 20-30 years old. Of these, 88.3% completed the MCTQ. Night shift workers or combination day and night shift workers had significant social jet lag (Table 1). Day shift workers alone did not meet criteria for social jetlag. Secondly, a larger social jetlag significantly correlated with worse QOL assessed through QOLRAD (Table 2). The significant correlations apply to all QOLRAD domains including emotional distress, sleep disturbances, food and drink problems, physical and social functioning, and vitality. The most significant correlations are between greater social jetlag and more impaired physical and social functioning (r=-0.368, p<0.001) and vitality (r=-0.391, p<0.001). Conclusion This study suggests: (1) that circadian disruption can be identified by the presence of social jetlag, as it was identified in only those engaged in night shift and combination shift workers. These findings imply that the MCTQ can be used as