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sParietal cells are particularly affected. Whether or not parietal cell dysfunction leads to poororganization of the gastric glands is unknown, and will be the subject of future study.

Su1948

In Vivo, Real Time Non-Invasive Assessment of Gastric Mucosal Injury UsingConfocal Laser Endomicroscopy: Focus on Mucosal Microvessels, ProgenitorCells and Mucosal Protection. Direct Comparison With Quantitative Histologyand Electron Microscopy.Andrzej S. Tarnawski, Amrita Ahluwalia, Michael K. Jones, Ercheng Zhu

Background/Aims: Studies of gastric mucosal injury and healing rely on macroscopic andhistological assessment of fixed stomach specimens, which may not fully reflect in vivoevents. As a result, the cellular targets and real time sequence of gastric mucosal injury arenot fully defined. Confocal laser endomicroscopy (CLE), a novel cutting edge technology,has enabled in vivo real-time visualization of mucosal structures at a subcellular resolution.This study was aimed to: 1) assess acute gastric injury in real time using CLE with a focuson mucosal microvessels and progenitor cells; 2) determine whether hydrotalcite (HTL),the newest generation antacid, can protect gastric mucosa against ethanol injury; and, 3)identify the mechanisms involved. Methods: Fischer F344 rats received 1 ml 0.5% fluoresceini.v. followed by intragastric (i.g.) ethanol (1 ml, 50%) or saline. In some rats, either 1 mlof vehicle or HTL (20mg/kg) was given i.g. 30 min prior to ethanol. CLE was performedusing the CellvizioLAB LSU F400 with Z ProFlex probe inserted i.g. and CLE images weremonitored for 30 min before and after ethanol administration. Studies: 1) CLE imaging ofgastric mucosa including epithelium and microvasculature; 2) vascular permeability; 3)mucosal blood flow dynamics; 4) progenitor cell integrity; 5) molecular imaging of VEGFR2using labeled antibody; 6) detection of i.v. injected bone marrow-derived stem cells (BMDSC)in gastric mucosa. For comparison we performed quantitative histology, and transmissionand scanning electron microscopy (EM). Results: At baseline, CLE of rat gastric mucosademonstrated a normal gastric gland pattern, vasculature, continuous microvascular bloodflow and low vascular permeability. Ethanol induced the exfoliation of surface epitheliumwithin 2-3 min, followed by a 550% increase in vascular permeability (p<0.001) at 3-5min; rupture of microvessels within 5-10 min, extensive extravasation of erythrocytes andvascular stasis. Progenitor cells were severely damaged. Histology and EM confirmed thesechanges. Pretreatment with HTL reduced ethanol-induced vascular permeability by 55%(p<0.01), preserved blood flow and reduced extent and severity of injury (all p<0.01). Incontrol rats VEGFR2 was visualized in endothelial cells of blood vessels and i.v. injectedBMDSC were present in gastric microcirculation. Conclusions: 1) CLE enables precise invivo, real time analysis of events taking place during gastric mucosal injury and evaluationof mucosal protection. 2) Microvascular injury and increased vascular permeability occurearly and precede progenitor cell damage and deep hemorrhagic necrosis. 3) CLE providesa significant advantage over standard histologic and EM assessment, by allowing real timemonitoring of in vivo mucosal structure and function, e.g. vascular permeability, and in vivomolecular imaging.

Su1949

Esophageal Mucosal Integrity Recovers After Laparoscopic Fundoplication inChildren With Gastroesophageal Reflux DiseaseFemke A. Mauritz, Nicolaas Fedde Rinsma, José M. Conchillo, Ernst van Heurn, Peter D.Siersema, David C. van der Zee, Maud van Herwaarden-Lindeboom

Background Esophageal intraluminal baseline impedance levels reflect the electrical resistanceof the esophageal wall and may serve as an instrument for in vivo evaluation of esophagealmucosal integrity in gastroesophageal reflux disease (GERD) in children. Fundoplication astreatment for GERD aims to reduce (acid) reflux events and restore mucosal integrity. Thiscould be reflected by increased intraluminal baseline impedance levels after operation. Theaim of this study was, therefore, to evaluate the effect of laparoscopic fundoplication onmucosal integrity by assessing intraluminal baseline impedance levels before and after fun-doplication in children with GERD. Methods Eleven children (5 males) with therapy resistantGERD were included. Median age was 6.5 years (range, 1.6 - 18.2) at the time of laparoscopicfundoplication. Twenty-four hour multichannel intraluminal impedance pH monitoring(MII-pH monitoring) was performed before and 3 months after fundoplication. For everyconsecutive two hour intervals in the 24-h tracings, intraluminal baseline impedance levelswere measured over a period of ≥ 30 seconds not containing any swallows or gastroesophagealreflux episodes. Intraluminal baseline impedance levels were calculated over four segments(3, 5, 7 and 15 cm above the LES) using a specific function incorporated in the analysissoftware (Ohmega MMS). Results Fundoplication was successful in reducing total acidexposure time (from 11.4% ± 2.3% to 0.9% ± 0.3%, p<0.001) and overall number of refluxepisodes (from 106.5 ± 20.1 to 19.7 ± 3.9, p=0.001). The mean distal baseline impedancelevel increased after fundoplication (from 2423 ± 414 Ω to 3560 ± 328 Ω, p<0.01). Baselineimpedance levels also increased at 5 cm (from 2969 ± 428 Ω to 4105 ± 300 Ω, p=0.02)and 7 cm segments (from 3124 ± 459 Ω to 3980 ± 248 Ω, p=0.04) above the LES. In theproximal segment, no significant changes were found after fundoplication (from 3099 ±341 Ω to 3621 ± 172 Ω, p=0.12). Prior to fundoplication, mean distal baseline impedancelevel showed a negative correlation with acid exposure time (r: -0.78, p<0.01). We alsoobserved a gradual increase of intraluminal baseline impedance levels from the distal to theproximal impedance segment in the esophagus, reflecting the distribution of acid exposurein the esophagus. Conclusion Reduction of acid exposure and number of reflux episodes bylaparoscopic fundoplication leads to a significant increase in intraluminal baseline impedancelevels in children with GERD, which may indicate repair of mucosal integrity and successof therapy.

S-506AGA Abstracts

Su1950

Effect of Celecoxib, a Selective Cycloxygenase-2 Inhibitor, on Acid-InducedHCO3- and Ulcerogenic Responses in Rat Duodenums; A Comparative StudyWith Conventional Non-Steroidal Anti-Inflammatory DrugsKoji Takeuchi, Kikuko Amagase, Hiroshi Satoh

Duodenal HCO3- secretion increases in response to luminal acid. This response is mainlymediated by endogenous prostaglandin E2 (PGE2) derived from cyclooxygenase (COX)-1.However, a recent study showed in cats that rofecoxib, a selective COX-2 inhibitor, by itselfdamaged the duodenal mucosa, similar to indomethacin, a non- selective COX inhibitor.In the present study, to confirm the importance of COX-1 in the duodenal mucosal defense,we examined the effect of celecoxib, another COX-2 selective inhibitor, on HCO3- andulcerogenic responses caused by acid in rat duodenums. Methods: Male SD rats were usedafter 18 h fasting. Under urethane anesthesia, a loop made in the proximal duodenum wasperfused with saline, and the HCO3- secretion was measured at pH 7.0 using a pH-statmethod and by adding 10 mM HCl. Mucosal acidification was performed by exposing theloop to 10 mM HCl for 10 min. In addition, the duodenal damage was induced by perusingthe loop with 100 mM HCl at a flow rate of 1 ml/h for 4 h. Indomethacin (5 mg/kg),loxoprofen (10 mg/kg), SC-560 (a selective COX-1 inhibitor, 3-30 mg/kg) and celecoxib (aselective COX-2 inhibitor, 30 mg/kg) were given ID 1 h before exposure to 10 mM HCl orthe onset of 100 mM HCl perfusion. Results: The mucosal acidification stimulated HCO3-secretion with an increase of mucosal PGE2 contents in the duodenum. The increase ofHCO3- secretion and PGE2 content in response to acidification were significantly inhibitedby prior administration of indomethacin. Likewise, a selective COX-1 inhibitor SC-560,dose-dependently inhibited the HCO3- response to acidification; a significant effect wasobserved at 10 mg/kg, together with the effect on the increased PGE2 production. However,a selective COX-2 inhibitor celecoxib had no effect on either of these responses. RT-PCRanalyses showed that COX-2 mRNA was not expressed in the duodenal mucosa afteracidification, while COX-1 mRNA was expressed in the normal mucosa and remainedunchanged before and after acid treatment. On the other hand, perfusion of the loop with100 mM HCl for 4 h produced mild hemorrhagic damage, and the severity of these lesionswas significantly worsened by indomethacin, loxoprofen and SC-560, while celecoxib didnot affect. Conclusion: These results confirmed that COX-1 is a key enzyme responsible forproducing PGs involved in the mechanism for the acid-induced HCO3- secretion in theduodenum, and further suggested that COX-1/PGs play a crucial role in the protection ofthe duodenal mucosa against acid injury.

Su1951

Recovery of Gastric Function After Acetium Administration: A 6 MonthsStudy in Atrophic Gastritis SubjectsFrancesco Di Mario, Hunor Pal Farkas, Francesco Ferrara, Nadia Dal Bo, Tiziana Slongo,Roberto Marcello, Massimo Rugge, Carmelo Scarpignato

Background: No consensus from different studies exists regarding the reversibility of atrophicgastritis; however, removal of H pylori from the already atrophic stomach may block furtherprogression of the disease. Although studies report a partial restoration of serum pepsinogenI (sPGI) levels after eradication, it is not clear if this finding reflects gastric mucosal healingon a morphological level. Immune-mediated atrophic changes in the stomach by definitionseem to be irreversible. Recently a new compound (L-cystein Acetium, Biohit, Finland) hasbeen proposed for prevention of gastric carcinogenesis in patients with atrophic gastritis,by reducing acetaldehyde (class I human carcinogen) production after food intake. Aims:To assess the changes in gastric function after long term administration of L-cysteine inmoderate to severe atrophic gastritis by sPGI and gastrin 17 (sG17). Methods: 30 patientswith histological features of moderate-severe body atrophic gastritis and sPGI < 25 μg/L (7men, mean age 47.9 years, range 27-71) had sPGI and sG17 measured at baseline. In 8patients autoimmune origin was confirmed by anti-parietal cell antibodies, the rest underwenteradication therapy for Helicobacter pylori infection earlier. Long term oral therapy withAcetium (3x100mg L-cysteine/day before meals) has been initiated and serologic markerswere determined at 3 and/or 6 months. Results Mean sPGI levels prior to treatment were7.9 μg/L, compared to the latest measurements' mean of 11,38 μg/L (p<0.001) reflectingpossible increase in active parietal cell mass. On the other hand the mean baseline level ofsG17 decreased from 34.4 pmol/L to 26,25 pmol/L (p<0.001) indicating changes in thenegative feedback of the regulation transmitted by gastrin. In a few cases, where multipleserological measurements were available, an obvious increasing trend was observed in sPGIlevels over time, as well as decrease in sG17 levels. Conclusion: L-cysteine seems to beuseful in restoring gastric secretion in subjects with chronic atrophic gastritis both after H.p.eradication and in case of autoimmune etiology.

Su1952

TH17 Pathway Promotes Mucosal Host Defense Against EsophagealCandidiasis in HIV-Infected PatientsAna Luiza Werneck-Silva, Carla Pagliari, Rosely A. Patzina, Wellington F. da Silva,Luciane K. Galo, Maria Irma S. Duarte

INTRODUCTION: Esophageal candidiasis is the most common opportunistic infection inthe GI tract in HIV+ patients. Host defense mechanisms against Candida albicans vary byanatomical site, as HIV+ patients are primarily susceptible to oropharyngeal and esophageal,but not vaginal or disseminated candidiasis. Although immunity to C. albicans was longconsidered to be mediated by Th1 cells, new data in both rodent and in humans haverevealed a role for the Th17 lineage, a subset of effector T cells that are localized at themucosal level, including the gut mucosa. To date, the relative contribution(s) of Th1 andTh17 responses in esophageal candidiasis have not been defined. AIMS: To determine therole of mucosal T cell immunity and IL-17 pathway against esophageal Candida infectionin HIV+ patients. METHODS: Immunohistochemistry to CD4+ and CD8+ T cells, INFγ,TGFβ, IL-6 and IL-17 were performed in esophageal histological samples obtained fromendoscopy in 28 HIV+, 16 with Candida esophagitis (Group A) (6 female and 10 male)