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PubMed Central (PMC3 - NLM DTD) (2,719,667 recursos)
Archive of life sciences journal literature at the U.S. National Institutes of Health (NIH), developed and managed by NIH's National Center for Biotechnology Information (NCBI) in the National Library of Medicine (NLM).

American Journal of Physiology - Gastrointestinal and Liver Physiology

Mostrando recursos 1 - 20 de 800

1. Reduced colonic microbial diversity is associated with colitis in NHE3-deficient mice - Larmonier, Claire B.; Laubitz, Daniel; Hill, Faihza M.; Shehab, Kareem W.; Lipinski, Leszek; Midura-Kiela, Monica T.; McFadden, Rita-Marie T.; Ramalingam, Rajalakshmy; Hassan, Kareem A.; Golebiewski, Marcin; Besselsen, David G.; Ghishan, Fayez K.; Kiela, Pawel R.
Chronic inflammation and enteric infections are frequently associated with epithelial Na+/H+ exchange (NHE) inhibition. Alterations in electrolyte transport and in mucosal pH associated with inflammation may represent a key mechanism leading to changes in the intestinal microbial composition. NHE3 expression is essential for the maintenance of the epithelial barrier function. NHE3−/− mice develop spontaneous distal chronic colitis and are highly susceptible to dextran sulfate (DSS)-induced mucosal injury. Spontaneous colitis is reduced with broad-spectrum antibiotics treatment, thus highlighting the importance of the microbiota composition in NHE3 deficiency-mediated colitis. We herein characterized the colonic microbiome of wild-type (WT) and NHE3−/− mice housed...

2. Glucose-dependent insulinotropic polypeptide regulates dipeptide absorption in mouse jejunum - Coon, Steven D.; Schwartz, John H.; Rajendran, Vazhaikkurichi M.; Jepeal, Lisa; Singh, Satish K.
Glucose-dependent insulinotropic polypeptide (GIP) secreted from jejunal mucosal K cells augments insulin secretion and plays a critical role in the pathogenesis of obesity and Type 2 diabetes mellitus. In recent studies, we have shown GIP directly activates Na-glucose cotransporter-1 (SGLT1) and enhances glucose absorption in mouse jejunum. It is not known whether GIP would also regulate other intestinal nutrient absorptive processes. The present study investigated the effect of GIP on proton-peptide cotransporter-1 (PepT1) that mediates di- and tripeptide absorption as well as peptidomimetic drugs. Immunohistochemistry studies localized both GIP receptor (GIPR) and PepT1 proteins on the basolateral and apical membranes...

3. Loss of NHE3 alters gut microbiota composition and influences Bacteroides thetaiotaomicron growth - Engevik, Melinda A.; Aihara, Eitaro; Montrose, Marshall H.; Shull, Gary E.; Hassett, Daniel J.; Worrell, Roger T.
Changes in the intestinal microbiota have been linked to diabetes, obesity, inflammatory bowel disease, and Clostridium difficile (C. difficile)-associated disease. Despite this, it remains unclear how the intestinal environment, set by ion transport, affects luminal and mucosa-associated bacterial composition. Na+/H+-exchanger isoform 3 (NHE3), a target of C. difficile toxin B, plays an integral role in intestinal Na+ absorption. Thus the NHE3-deficient mouse model was chosen to examine the effect of pH and ion composition on bacterial growth. We hypothesized that ion transport-induced change in the intestinal environment would lead to alteration of the microbiota. Region-specific changes in ion composition and...

4. Helicobacter pylori impedes acid-induced tightening of gastric epithelial junctions - Marcus, Elizabeth A.; Vagin, Olga; Tokhtaeva, Elmira; Sachs, George; Scott, David R.
Gastric infection by Helicobacter pylori is the most common cause of ulcer disease and gastric cancer. The mechanism of progression from gastritis and inflammation to ulcers and cancer in a fraction of those infected is not definitively known. Significant acidity is unique to the gastric environment and is required for ulcer development. The interplay between gastric acidity and H. pylori pathogenesis is important in progression to advanced disease. The aim of this study was to characterize the impact of acid on gastric epithelial integrity and cytokine release and how H. pylori infection alters these responses. Human gastric epithelial (HGE-20) cells...

5. Degradation of cIAPs contributes to hepatocyte lipoapoptosis - Akazawa, Yuko; Guicciardi, Maria Eugenia; Cazanave, Sophie C.; Bronk, Steven F.; Werneburg, Nathan W.; Kakisaka, Keisuke; Nakao, Kazuhiko; Gores, Gregory J.
Hepatocyte apoptosis is a hallmark of nonalcoholic steatohepatitis. We have previously observed that the saturated free fatty acids (FFAs) induce hepatocyte apoptosis in part via a death receptor 5 (DR5)-mediated signaling pathway. Cellular inhibitor of apoptosis protein 1 and 2 (cIAP-1 and cIAP-2) proteins are potent inhibitors of death receptor-mediated apoptosis. However, the role of the cIAPs in FFA-mediated hepatocyte apoptosis is unexplored. Our aim was to determine whether cIAPs are dysregulated during hepatocyte lipoapoptosis. cIAP proteins underwent rapid cellular elimination following treatment with the saturated FFAs palmitate (PA) and stearate. In contrast, PA did not decrease cIAP-1 and cIAP-2...

6. Acyl chain length, saturation, and hydrophobicity modulate the efficiency of dietary fatty acid absorption in adult humans - McKimmie, Ryan L.; Easter, Linda; Weinberg, Richard B.
Intestinal fat absorption is known to be, overall, a highly efficient process, but much less is known about the efficiency with which individual dietary fatty acids (FA) are absorbed by the adult small intestine. We therefore measured the absorption efficiency of the major dietary FA using sucrose polybehenate (SPB) as a nonabsorbable marker and analyzed how it is modulated by acyl chain physicochemical properties and polymorphisms of proteins involved in chylomicron assembly. Dietary FA absorption efficiency was measured in 44 healthy subjects fed a standard diet containing 35% fat and 5% SPB. FA and behenic acid (BA) were measured in...

7. Combined genetic and pharmacological inhibition of TRPV1 and P2X3 attenuates colorectal hypersensitivity and afferent sensitization - Kiyatkin, Michael E.; Feng, Bin; Schwartz, Erica S.; Gebhart, G. F.
The ligand-gated channels transient receptor potential vanilloid 1 (TRPV1) and P2X3 have been reported to facilitate colorectal afferent neuron sensitization, thus contributing to organ hypersensitivity and pain. In the present study, we hypothesized that TRPV1 and P2X3 cooperate to modulate colorectal nociception and afferent sensitivity. To test this hypothesis, we employed TRPV1-P2X3 double knockout (TPDKO) mice and channel-selective pharmacological antagonists and evaluated combined channel contributions to behavioral responses to colorectal distension (CRD) and afferent fiber responses to colorectal stretch. Baseline responses to CRD were unexpectedly greater in TPDKO compared with control mice, but zymosan-produced CRD hypersensitivity was absent in TPDKO...

8. Maturation of upstream and downstream esophageal reflexes in human premature neonates: the role of sleep and awake states - Jadcherla, Sudarshan R.; Chan, Chin Yee; Fernandez, Soledad; Splaingard, Mark
We tested the hypothesis that the sensory-motor characteristics of aerodigestive reflexes are dependent on stimulus type and volumes, sleep or awake states, and maturation. Thirteen neonates were studied at 33.6 ± 0.5 wk (time 1) and 37.3 ± 0.5 wk (time 2) postmenstrual age using multimodal provocative esophageal manometry concurrent with video polysomnography. Effects of graded volumes (399 infusions at time 1, 430 infusions at time 2) of midesophageal stimulation with air, water, and apple juice on the sensory thresholds and recruitment frequency of upper esophageal sphincter (UES), esophageal body, and lower esophageal sphincter (LES) reflexes were investigated during sleep...

9. Recent advances in transport of water-soluble vitamins in organs of the digestive system: a focus on the colon and the pancreas - Said, Hamid M.
This review focuses on recent advances in our understanding of the mechanisms and regulation of water-soluble vitamin (WSV) transport in the large intestine and pancreas, two important organs of the digestive system that have only recently received their fair share of attention. WSV, a group of structurally unrelated compounds, are essential for normal cell function and development and, thus, for overall health and survival of the organism. Humans cannot synthesize WSV endogenously; rather, WSV are obtained from exogenous sources via intestinal absorption. The intestine is exposed to two sources of WSV: a dietary source and a bacterial source (i.e., WSV...

10. Intestinal microbiota and immune function in the pathogenesis of irritable bowel syndrome - Ringel, Yehuda; Maharshak, Nitsan
The pathophysiology of irritable bowel syndrome (IBS) is believed to involve alterations in the brain-gut axis; however, the etiological triggers and mechanisms by which these changes lead to symptoms of IBS remain poorly understood. Although IBS is often considered a condition without an identified “organic” etiology, emerging evidence suggests that alterations in the gastrointestinal microbiota and altered immune function may play a role in the pathogenesis of the disorder. These recent data suggest a plausible model in which changes in the intestinal microbiota and activation of the enteric immune system may impinge upon the brain-gut axis, causing the alterations in...

11. Helicobacter hepaticus increases intestinal injury in a rat model of necrotizing enterocolitis - Dvorak, Katerina; Coursodon-Boyiddle, Christine F.; Snarrenberg, Chelsea L.; Kananurak, Anchasa; Underwood, Mark A.; Dvorak, Bohuslav
Enterohepatic helicobacter species (EHS) infect the intestinal tract and biliary tree, triggering intestinal and hepatic disorders. Helicobacter hepaticus, the prototypic murine EHS, is also associated with inflammation. Necrotizing enterocolitis (NEC) is a devastating disease of premature infants. The cause of NEC is not fully understood, but anomalies of bacterial colonization (dysbiosis) are thought to play an important role in disease onset. To evaluate the effect of H. hepaticus infection on the development of NEC, premature formula-fed rats were kept either in H. hepaticus-free conditions or colonized with H. hepaticus; both groups were exposed to asphyxia and cold stress. The incidence...

12. Irgm1-deficient mice exhibit Paneth cell abnormalities and increased susceptibility to acute intestinal inflammation - Liu, Bo; Gulati, Ajay S.; Cantillana, Viviana; Henry, Stanley C.; Schmidt, Elyse A.; Daniell, Xiaoju; Grossniklaus, Emily; Schoenborn, Alexi A.; Sartor, R. Balfour; Taylor, Gregory A.
Crohn's disease (CD) is a chronic, immune-mediated, inflammatory disorder of the intestine that has been linked to numerous susceptibility genes, including the immunity-related GTPase (IRG) M (IRGM). IRGs comprise a family of proteins known to confer resistance to intracellular infections through various mechanisms, including regulation of phagosome processing, cell motility, and autophagy. However, despite its association with CD, the role of IRGM and other IRGs in regulating intestinal inflammation is unclear. We investigated the involvement of Irgm1, an ortholog of IRGM, in the genesis of murine intestinal inflammation. After dextran sodium sulfate exposure, Irgm1-deficient [Irgm1 knockout (KO)] mice showed increased...

13. Epimorphin deletion inhibits polyposis in the Apcmin/+ mouse model of colon carcinogenesis via decreased myofibroblast HGF secretion - Swietlicki, Elzbieta A.; Bala, Shashi; Lu, Jianyun; Shaker, Anisa; Kularatna, Gowri; Levin, Marc S.; Rubin, Deborah C.
Interactions between the epithelium and surrounding mesenchyme/stroma play an important role in normal gut morphogenesis, the epithelial response to injury, and epithelial carcinogenesis. The tumor microenvironment, composed of stromal cells including myofibroblasts and immune cells, regulates tumor growth and the cancer stem cell niche. Deletion of epimorphin (Epim), a syntaxin family member expressed in myofibroblasts and macrophages, results in partial protection from colitis and from inflammation-induced colon cancer in mice. We sought to determine whether epimorphin deletion protects from polyposis in the Apcmin/+ mouse model of intestinal carcinogenesis. Epim−/− mice were crossed to Apcmin/+ mice; Apcmin/+ and Apcmin/+/Epim−/− mice were...

14. A multicenter study to standardize reporting and analyses of fluorescence-activated cell-sorted murine intestinal epithelial cells - Magness, Scott T.; Puthoff, Brent J.; Crissey, Mary Ann; Dunn, James; Henning, Susan J.; Houchen, Courtney; Kaddis, John S.; Kuo, Calvin J.; Li, Linheng; Lynch, John; Martin, Martin G.; May, Randal; Niland, Joyce C.; Olack, Barbara; Qian, Dajun; Stelzner, Matthias; Swain, John R.; Wang, Fengchao; Wang, Jiafang; Wang, Xinwei; Yan, Kelley; Yu, Jian; Wong, Melissa H.
Fluorescence-activated cell sorting (FACS) is an essential tool for studies requiring isolation of distinct intestinal epithelial cell populations. Inconsistent or lack of reporting of the critical parameters associated with FACS methodologies has complicated interpretation, comparison, and reproduction of important findings. To address this problem a comprehensive multicenter study was designed to develop guidelines that limit experimental and data reporting variability and provide a foundation for accurate comparison of data between studies. Common methodologies and data reporting protocols for tissue dissociation, cell yield, cell viability, FACS, and postsort purity were established. Seven centers tested the standardized methods by FACS-isolating a specific...

15. Adaptive regulation of human intestinal thiamine uptake by extracellular substrate level: a role for THTR-2 transcriptional regulation - Nabokina, Svetlana M.; Subramanian, Veedamali S.; Valle, Judith E.; Said, Hamid M.
The intestinal thiamine uptake process is adaptively regulated by the level of vitamin in the diet, but the molecular mechanism involved is not fully understood. Here we used the human intestinal epithelial Caco-2 cells exposed to different levels of extracellular thiamine to delineate the molecular mechanism involved. Our results showed that maintaining Caco-2 cells in a thiamine-deficient medium resulted in a specific and significant increase of [3H]thiamine uptake compared with cell exposure to a high level of thiamine (1 mM). This adaptive regulation was also associated with a higher level of mRNA expression of thiamine transporter-2 (THTR-2), but not thiamine...

16. Transcellular oxalate and Cl− absorption in mouse intestine is mediated by the DRA anion exchanger Slc26a3, and DRA deletion decreases urinary oxalate - Freel, Robert W.; Whittamore, Jonathan M.; Hatch, Marguerite
Active transcellular oxalate transport in the mammalian intestine contributes to the homeostasis of this important lithogenic anion. Several members of the Slc26a gene family of anion exchangers have a measurable oxalate affinity and are expressed along the gut, apically and basolaterally. Mouse Slc26a6 (PAT1) targets to the apical membrane of enterocytes in the small intestine, and its deletion results in net oxalate absorption and hyperoxaluria. Apical exchangers of the Slc26a family that mediate oxalate absorption have not been established, yet the Slc26a3 [downregulated in adenoma (DRA)] protein is a candidate mediator of oxalate uptake. We evaluated the role of DRA...

17. Cysteine 96 of Ntcp is responsible for NO-mediated inhibition of taurocholate uptake - Ramasamy, Umadevi; Anwer, M. Sawkat; Schonhoff, Christopher M.
The Na+ taurocholate (TC) cotransporting polypeptide Ntcp/NTCP mediates TC uptake across the sinusoidal membrane of hepatocytes. Previously, we demonstrated that nitric oxide (NO) inhibits TC uptake through S-nitrosylation of a cysteine residue. Our current aim was to determine which of the eight cysteine residues of Ntcp is responsible for NO-mediated S-nitrosylation and inhibition of TC uptake. Thus, we tested the effect of NO on TC uptake in HuH-7 cells transiently transfected with cysteine-to-alanine mutant Ntcp constructs. Of the eight mutants tested, only C44A Ntcp displayed decreased total and plasma membrane (PM) levels that were also reflected in decreased TC uptake....

18. Developmental origins of colon smooth muscle dysfunction in IBS-like rats - Li, Qingjie; Winston, John H.; Sarna, Sushil K.
Epidemiological studies show that subsets of adult and pediatric patients with irritable bowel syndrome (IBS) have prior exposures to psychological or inflammatory stress. We investigated the cellular mechanisms of colonic smooth muscle dysfunction in adult rats subjected to neonatal inflammation. Ten-day-old male rat pups received 2,4,6-trinitrobenzene sulfonic acid to induce colonic inflammation. Colonic circular smooth muscle strips were obtained 6 to 8 wk later. We found that about half of the neonate pups subjected to inflammatory insult showed a significant increase in expression of the pore-forming α1C-subunit of Cav1.2b channels in adult life. These were the same rats in whom...

19. Reduced thoracic fluid content in early-stage primary biliary cirrhosis that associates with impaired cardiac inotropy - Zalewski, Paweł; Jones, David; Lewis, Ieuan; Frith, James; Newton, Julia L.
Primary biliary cirrhosis (PBC) is a chronic liver disease characterized by cholestasis. Recent MRI studies have confirmed the presence of cardiac abnormalities in noncirrhotic PBC patients. However, cardiorespiratory consequences of these abnormalities have not been explored. Thoracic fluid content (TFC) is a noninvasive bioelectrical impedance measure of the electrical conductivity of the chest cavity. We explored TFC and its relationship with cardiac contractility parameters in early-stage PBC patients, compared with chronic liver disease and community controls. TFC was measured in early-stage PBC (noncirrhotic; n = 78), nonalcoholic fatty liver disease (n = 23), and primary sclerosing cholangitis (n = 18)...

20. Characterization of CFTR High Expresser cells in the intestine - Jakab, Robert L.; Collaco, Anne M.; Ameen, Nadia A.
The CFTR High Expresser (CHE) cells express eightfold higher levels of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel compared with neighboring enterocytes and were first identified by our laboratory (Ameen et al., Gastroenterology 108: 1016, 1995). We used double-label immunofluorescence microscopy to further study these enigmatic epithelial cells in rat intestine in vivo or ex vivo. CHE cells were found in duodenum, most frequent in proximal jejunum, and absent in ileum and colon. CFTR abundance increased in CHE cells along the crypt-villus axis. The basolateral Na+K+Cl− cotransporter NKCC1, a key transporter involved in Cl− secretion, was detected at...

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