bluuebunny/crossref_metadata_2025 huggingface dataset:
Intravenous glycine improves survival in rat liver transplantation
Authors: Schemmer Peter , Bradford Blair U. , Rose Michelle L. , Bunzendahl Hartwig , Raleigh James A. , Lemasters John J. , Thurman Ronald G.
Published: December 2017

In situ manipulation by touching, retracting, and moving liver lobes gently during harvest dramatically reduces survival after transplantation (P. Schemmer, R. Schoonhoven, J. A. Swenberg, H. Bunzendahl, and R. G. Thurman. Transplantation 65: 1015–1020, 1998). The development of harvest-dependent graft injury upon reperfusion can be prevented with GdCl3, a rare earth metal and Kupffer cell toxicant, but it cannot be used in clinical liver transplantation because of its potential toxicity. Thus the effect of glycine, which prevents activation of Kupffer cells, was assessed here. Minimal dissection of the liver for 12 min plus 13 min without manipulation had no effect on survival (100%). However, gentle manipulation decreased survival to 46% in the control group. Furthermore, serum transaminases and liver necrosis were elevated 4- to 12-fold 8 h after transplantation. After organ harvest, the rate of entry and exit of fluorescein dextran, a dye confined to the vascular space, was decreased about twofold, indicating disturbances in the hepatic microcirculation. Pimonidazole binding, which detects hypoxia, increased about twofold after organ manipulation, and Kupffer cells isolated from manipulated livers produced threefold more tumor necrosis factor-α after lipopolysaccharide than controls. Glycine given intravenously to the donor increased the serum glycine concentration about sevenfold and largely prevented the effect of gentle organ manipulation on all parameters studied. These data indicate for the first time that pretreatment of donors with intravenous glycine minimizes reperfusion injury due to organ manipulation during harvest and after liver transplantation.
Increased gastrointestinal permeability is an early lesion in the spontaneously diabetic BB rat
Authors: Meddings J. B. , Jarand J. , Urbanski S. J. , Hardin J. , Gall D. G.
Published: December 2017

The BB rat spontaneously develops autoimmune diabetes. Feeding these animals a hydrolyzed casein diet significantly reduces the incidence of this disease, suggesting that a dietary antigen is involved in the pathogenesis of this disease. In other syndromes associated with luminal antigens, including celiac and Crohn’s disease, increased intestinal permeability has been suggested to play an etiological role. Therefore, the objective of this study was to evaluate whether increased permeability was also present in BB rats before disease development. By measuring gastrointestinal permeability, in animals on a regular or hydrolyzed casein diet, we were able to demonstrate that increased gastric and small intestinal permeability appeared before the development of both insulitis and clinical diabetes. Although hydrolysis of dietary protein significantly reduced the incidence of diabetes, it did not alter the small intestinal permeability abnormality, suggesting that this is an early event. Increased permeability appears to have an early role in the genesis of several immunological diseases and may represent a common event in these diseases.
IV. Determinants of nitric oxide protection and toxicity in liver
Authors: Li Jianrong , Billiar Timothy R.
Published: December 2017

Whereas nitric oxide (NO) produced by constitutive endothelial NO synthase is protective to the liver, NO produced by the inducible NO synthase (iNOS) can be either toxic or protective depending on the conditions. The availability of selective iNOS inhibitors and mice lacking various NOS isoforms made it possible to begin to elucidate the precise roles of NO in the liver. Under conditions of redox stress, induced NO contributes to hepatic damage. However, in acute inflammatory conditions associated with cytokine exposure, NO acts as a potent inhibitor of apoptosis in the liver. Our current understanding of the mechanisms by which NO exerts both hepatoprotective and hepatotoxic actions is discussed in this themes article.
II. The yin and yang of T cells in intestinal inflammation: pathogenic and protective roles in a mouse colitis model
Authors: de Winter Hilde , Cheroutre Hilde , Kronenberg Mitchell
Published: December 2017

Inflammatory bowel disease (IBD) is a multifactorial immune disorder of uncertain etiology. The advent of several mouse models of mucosal inflammation that resemble IBD has provided insight into the mechanisms governing both normal and pathological mucosal immune function. In a widely used adoptive transfer model, the injection into immunodeficient mice of a subset of CD4+T lymphocytes, the CD4+CD45RBhighcells, leads to inflammation of the intestine. Pathogenesis is due in part to the secretion of proinflammatory cytokines. The induction of colitis can be prevented by cotransfer of another CD4+subpopulation, the CD4+CD45RBlowT cells. This population behaves analogously to the CD4+CD45RBhighpopulation in terms of the acquisition of activation markers and homing to the host intestine. However, their lymphokine profile when activated is different, and anti-inflammatory cytokines secreted and/or induced by CD4+CD45RBlowT cells prevent colitis. In this themes article, a description of the adoptive transfer model is given, the factors that promote and prevent colitis pathogenesis are discussed, and some controversial aspects of the model are addressed.
Effects of sustained low-flow perfusion on the response to vasoconstrictor agents in postnatal intestine
Authors: Nowicki Philip T.
Published: December 2017

This laboratory has previously reported that sustained reduction of blood flow in newborn intestine causes a triphasic increase in vascular resistance that occurs over 3–4 h and that these changes are mediated, in part, by loss of endothelial nitric oxide (NO) production. This study examines the effects of exposure to sustained low-flow perfusion on the subsequent response to three contractile agonists: ANG II, norepinephrine (NE), and endothelin-1 (ET-1). Gut loops from 3- and 35-day-old swine were exposed to low-flow conditions in vivo (i.e., reduction of flow to ∼50% of baseline) for 30 min or 5 h. Thereafter, they were removed to an extracorporeal perfusion circuit for in vitro hemodynamic assessment; alternatively, the mesenteric artery perfusing the gut loop was removed and cut into rings for assessment of isometric tension development. Gut loops from 3-day-old subjects exposed to low-flow conditions demonstrated significantly increased contractile responses to ANG II, NE, and ET-1; also, mesenteric artery rings from these gut loops demonstrated a significant reduction of the ED50for all three agonists. Similar changes were not observed in intestine or mesenteric artery rings from older subjects. Sustained blockade of endogenous NO synthesis with NG-monomethyl- l-arginine duplicated the effects of exposure to sustained low-flow perfusion. It appears that sustained reduction of blood flow in newborn intestine decreases constitutive NO production, which in turn causes a generalized enhancement of the contractile efficacy of ANG II, NE, and ET-1.
Duodenal acid-induced gastric relaxation is mediated by multiple pathways
Authors: Lu Yuan-Xu , Owyang Chung
Published: December 2017

In this study, we used an in vivo anesthetized rat model to investigate the mechanisms responsible for duodenal acid-induced inhibition of gastric motility. Intraduodenal infusion of HCl produced a rate-dependent decrease in intragastric pressure. Infusion of HCl at 2 ml/h produced a physiological plasma secretin level and elicited a decrease in intragastric pressure of 3.0 ± 0.2 cmH20. Infusion of rabbit secretin antiserum reduced the acid-induced inhibition of gastric motility by 85 ± 5%, suggesting mediation mainly by endogenous secretin. Administration of the cholecystokinin (CCK)-A antagonist MK-329 caused only a modest 10 ± 3% reduction in gastric relaxation, whereas the serotonin antagonist ICS-205930 had no effect. In contrast, immunoneutralization with the secretin antibody caused only a 15% reduction in the relaxation evoked by a higher rate of HCl infusion (3 ml/h), whereas MK-329 and ICS-205930 caused a 20 ± 4% reduction and no reduction, respectively. Bilateral truncal vagotomy or perivagal application of capsaicin completely abolished gastric relaxation in response to low rates (1–2 ml/h) of 0.1 N HCl infusion but only partially affected gastric relaxation in response to a higher infusion rate (3 ml/h). These observations indicate that multiple pathways mediate the duodenal acid-induced inhibition of gastric motility. At low rates of HCl infusion, gastric relaxation is mediated primarily by endogenous secretin, which acts through vagal afferent pathways. At higher rates of HCl infusion, gastric relaxation is mediated by endogenous secretin, CCK, and possibly by the direct action of HCl on vagal afferent pathways or yet unidentified neuropathways.
Quantitation of rat hepatic stellate cell contraction: stellate cells’ contribution to sinusoidal resistance
Authors: Thimgan Matthew S. , Yee Hal F.
Published: December 2017

Although it has been hypothesized that contraction of hepatic stellate cells (HSC) regulates blood flow by modulating sinusoidal resistance, neither HSC contraction nor relaxation has been directly quantitated. To test this hypothesis, a force transducer was employed to directly measure the magnitude and rate of contraction and relaxation by primary rat HSC (4.7 × 105± 0.2 × 105cells) cultured within a collagen gel. Serial exposures to 10% fetal bovine serum stimulated 81 ± 14 and 82 ± 10 dyn of contractile force, respectively. Subsequent stimulation with 2 nM endothelin-1 (ET-1) resulted in the development of 185 ± 25 dyn of force. Contractions began within 10 s of ET-1 stimulation, and the half time of maximal force development was <5 min. Removal of agonist resulted in complete or nearly complete relaxation within 45 min. These results suggest that the magnitude and rate of HSC contraction and relaxation are capable of modulating blood flow via sinusoidal constriction.
A thermal injury-induced circulating factor(s) compromises intestinal cell morphology, proliferation, and migration
Authors: Varedi Maryam , Greeley George H. , Herndon David N. , Englander Ella W.
Published: December 2017

The effects of a 60% body surface area thermal injury in rats on the morphology and proliferation of the epithelium of the small intestine and the in vitro effects of serum collected from scalded rats on intestinal epithelial cells were investigated. Scald injury caused significant reductions in duodenal villus width and crypt dimensions, villus enterocytes changed in shape from columnar to cuboidal, and the number of goblet cells decreased. The proportion of bromodeoxyuridine-labeled S phase cells in crypts was also diminished. In vitro, incubation of intestinal epithelial cells (IEC-6) with scalded rat serum (SRS) collected at either 12 or 24 h after injury caused a disruption in the integrity of the confluent culture and induced the appearance of large denuded areas. SRS also decreased DNA synthesis and delayed wound closure in an in vitro wound-healing model. The thermal injury-induced changes in intestinal mucosal morphology and epithelial cell growth characteristics described in this study may underlie, in part, the mechanism(s) involved in the diminished absorption of nutrients, increased intestinal permeability, and sepsis in patients with thermal injury.
Cortical activation during human volitional swallowing: an event-related fMRI study
Authors: Hamdy Shaheen , Mikulis David J. , Crawley Adrian , Xue Shuwen , Lau Helena , Henry Stanley , Diamant Nicholas E.
Published: December 2017

Functional magnetic resonance imaging (fMRI) provides a safe, noninvasive method for studying task-related cortical neuronal activity. Because the cerebral cortex is strongly implicated in the control of human swallowing, we sought to identify its functional neuroanatomy using fMRI. In 10 healthy volunteers, a swallow event-related paradigm was performed by injecting 5 ml water bolus into the oral cavity every 30 s. Whole brain functional magnetic susceptibility[Formula: see text]-weighted spiral imaging data were simultaneously acquired over 600 s on a 1.5-T magnetic resonance scanner, utilizing the blood oxygenation level-dependent technique, and correlation maps were generated using both >99% percentile rank and spatial extent thresholding. We observed areas of increased signal change consistently in caudal sensorimotor cortex, anterior insula, premotor cortex, frontal operculum, anterior cingulate and prefrontal cortex, anterolateral and posterior parietal cortex, and precuneus and superiomedial temporal cortex. Less consistent activations were also seen in posterior cingulate cortex and putamen and caudate nuclei. Activations were bilateral, but almost every region, particularly the premotor, insular, and frontal opercular cortices, displayed lateralization to one or the other hemisphere. Swallow-related cortical activity is multidimensional, recruiting brain areas implicated in processing motor, sensory, and attention/affective aspects of the task.
Development of an endogenous epithelial Na+/H+exchanger (NHE3) in three clones of Caco-2 cells
Authors: Janecki Andrzej J. , Montrose Marshall H. , Tse C. Ming , de Medina Fermin Sanchez , Zweibaum Alain , Donowitz Mark
Published: December 2017

Expression of endogenous Na+/H+exchangers (NHEs) NHE3 and NHE1 at the apical (AP) and basolateral (BL) membrane domains was investigated in three clones (ATCC, PF-11, and TC-7) derived from the human adenocarcinoma cell line Caco-2. In all three clones, NHE1 was the only isoform detected at the BL domain during 3 to 22 postconfluent days (PCD). In clone PF-11, the BL NHE1 activity increased up to 7 PCD and remained stable thereafter. Both NHE1 and NHE3 were found at the AP domain at 3 PCD and contributed 67 and 33% to the total AP Na+/H+exchange, respectively. The AP NHE3 activity increased significantly from 3 to 22 PCD, from 93 to 450 μM H+/s, whereas AP NHE1 activity decreased from 192 to 18 μM H+/s during that time. Similar results were obtained with the ATCC clone, whereas very little AP NHE3 activity was observed in clone TC-7. Surface biotinylation and indirect immunofluorescence confirmed these results and also suggested an increase in the number of cells expressing NHE3 being the major mechanism of the observed overall increase in NHE3 activity in PF-11 and ATCC clones. Phorbol 12-myristate 13-acetate (PMA, 1 μM) acutely inhibited NHE3 activity by 28% of control, whereas epidermal growth factor (EGF, 200 ng/ml) stimulated the activity by 18%. The effect of PMA was abolished by the protein kinase C (PKC) inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, suggesting involvement of PKC in the PMA-induced inhibition of NHE3. Similar magnitude of inhibition by PMA and stimulation by EGF was observed at 7 and 17 PCD, suggesting the development of regulatory mechanisms in the early postconfluent period. Taken together, these data suggest a close similarity of membrane targeting and regulation of endogenous NHE3 between Caco-2 cells and native small intestinal epithelial cells and support the usefulness of some Caco-2 cell clones as an in vitro model for studies on physiology of NHE3 in the intestinal epithelium.
β-Adrenergic agonists stimulate Na+-K+-Cl−cotransport by inducing intracellular Ca2+ liberation in crypt cells
Authors: del Castillo Jesús R. , Arévalo Julio C. , Burguillos Luis , Súlbaran-Carrasco María C.
Published: December 2017

Epinephrine and β-adrenergic agonists (β1 and β2 for isoproterenol, β1 for dobutamine, β2 for salbutamol) stimulated K+ (or86Rb) influx mediated by the Na+-K+-2Cl−cotransporter and the Na+-K+pump in isolated colonic crypt cells. Preincubation with bumetanide abolished the epinephrine effect on the Na+-K+pump, suggesting that the primary effect is on the cotransporter. Maximal effect was obtained with 1 μM epinephrine with an EC50 of 91.6 ± 9.98 nM. Epinephrine-induced K+ transport was blocked by propranolol with an IC50 of 134 ± 28.2 nM. α-Adrenergic drugs did not modify K+ transport mechanisms. Neither Ba2+ nor tetraethylammonium nor DIDS modified the adrenergic enhancement on the cotransporter. In addition, epinephrine did not affect K+ efflux. Dibutyryl cAMP did not alter K+ transport. Reduction of extracellular Ca2+ to 30 nM did not influence the response to epinephrine. However, 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid-AM abolished epinephrine-induced K+ transport. Ionomycin increased Na+-K+-2Cl−cotransport activity. Moreover, epinephrine increased intracellular Ca2+ concentration in a process inhibited by propranolol. In conclusion, epinephrine stimulated the Na+-K+-2Cl−cotransporter in a process mediated by β1- and β2-receptors and modulated by intracellular Ca2+ liberation.
Group I secreted PLA2and arachidonic acid metabolites in the maintenance of cat LES tone
Authors: Cao W. B. , Harnett K. M. , Chen Q. , Jain M. K. , Behar J. , Biancani P.
Published: December 2017

Spontaneous tone of in vitro lower esophageal sphincter (LES) circular muscle is associated with elevated levels of arachidonic acid (AA), PGF2α, and increased [35S]guanosine 5′- O-(3-thiotriphosphate) (GTPγS) binding to Gq-, Gi3-, and Gi1/i2-like G proteins. Tone and AA levels were reduced by inhibitors of a pancreatic-like (group I) secreted phospholipase A2(sPLA2), by the cyclooxygenase inhibitor indomethacin, and by the thromboxane A2antagonist SQ-29548. In addition, pertussis toxin (PTX) reduced LES tone, confirming a role of PTX-sensitive G proteins in maintenance of LES tone. PGF2αcontracted LES smooth muscle (strips and cells) and increased [35S]GTPγS binding to Gqand Gi3in solubilized LES circular muscle membranes. PGF2α-induced contraction of LES permeable muscle cells was inhibited by Gqand Gi3but not by Gi1/i2and Goantibodies. The thromboxane A2analog U-46619 contracted LES smooth muscle and increased Gqbinding. U-46619-induced contraction was inhibited by Gqbut not by Gi3, Gi1/i2, and Goantibodies. LES tone and [35S]GTPγS binding were significantly reduced by indomethacin. We conclude that group I sPLA2may mediate “spontaneous” LES tone by producing AA, which is metabolized to PGF2αand thromboxane A2. These AA metabolites activate receptors linked to Gi3and Gqto maintain LES contraction.
Peripheral gastric leptin modulates brain stem neuronal activity in neonates
Authors: Yuan Chun-Su , Attele Anoja S. , Wu Ji An , Zhang Liu , Shi Zhi Q.
Published: December 2017

Afferent sensory fibers are the primary neuroanatomic link between nutrient-related events in the gastrointestinal tract and the central neural substrates that modulate ingestion. In this study, we evaluated the peripheral gastric effects of leptin (OB protein) on brain stem neuronal activities using an in vitro neonatal rat preparation. We also tested gastric leptin effects as a function of age in neonates. For ∼33% of the nucleus tractus solitarius units observed, gastric leptin (10 nM) produced a significant activation of 188.2 ± 8.6% (mean ± SE) compared with the control level of 100% ( P < 0.01). Concentration-dependent leptin effects have also been shown. The remaining neurons (67%) had no significant response to gastric leptin application. Next, we evaluated the peripheral gastric effects of leptin (10 nM) on brain stem unitary activity in three different age groups (1–2 days old, 3–5 days old, and 7–8 days old) of neonatal rats. In the 1- to 2-day-old and the 3- to 5-day-old groups, we observed that response ratios and activity levels were similar. However, there was a significant difference between the 7- to 8-day-old group and the two younger age groups in both the response ratios and the activation levels. The percentage of activation responses increased from ∼26% in the 1- to 2-day-old and the 4- to 5-day-old age groups to 70% in the 7- to 8-day-old group ( P < 0.05). The level of activation increased from 168.3 ± 2.7% (compared with the control level) in the 1- to 2-day-old and the 4- to 5-day-old age groups to 231.4 ± 11.9% in the 7- to 8-day-old group ( P < 0.01). Our data demonstrate that peripheral gastric leptin modulates brain stem neuronal activity and suggest that gastric leptin has a significantly stronger effect in the 7- to 8-day-old animals than in the younger neonates.
II. The intestine as a sensory organ: neural, endocrine, and immune responses
Authors: Furness John B. , Kunze Wolfgang A. A. , Clerc Nadine
Published: December 2017

The lining of the gastrointestinal tract is the largest vulnerable surface that faces the external environment. Just as the other large external surface, the skin, is regarded as a sensory organ, so should the intestinal mucosa. In fact, the mucosa has three types of detectors: neurons, endocrine cells, and immune cells. The mucosa is in immediate contact with the intestinal contents so that nutrients can be efficiently absorbed, and, at the same time, it protects against the intrusion of harmful entities, such as toxins and bacteria, that may enter the digestive system with food. Signals are sent locally to control motility, secretion, tissue defense, and vascular perfusion; to other digestive organs, for example, to the stomach, gallbladder, and pancreas; and to the central nervous system, for example to influence feeding behavior. The three detecting systems in the intestine are more extensive than those of any other organ: the enteric nervous system contains on the order of 108 neurons, the gastroenteropancreatic endocrine system uses more than 20 identified hormones, and the gut immune system has 70– 80% of the body's immune cells. The gastrointestinal tract has an integrated response to changes in its luminal contents. When this response is maladjusted or is overwhelmed, the consequences can be severe, as in cholera intoxication, or debilitating, as in irritable bowel syndrome. Thus it is essential to obtain a full understanding of the sensory functions of the intestine, of how the body reacts to the information, and of how neural, hormonal, and immune signals interact.
III. Endocrine cell recognition of luminal nutrients
Authors: Buchan Alison M. J.
Published: December 2017

The profile of hormone secretion from the gastrointestinal tract on food ingestion depends to a great extent on the composition of the meal. High levels of protein result in a quantitatively and qualitatively different response compared with a meal rich in fats. The outstanding question is whether this differential response is driven by the ability of gastroenteric endocrine cells to directly sense the contents of the lumen via apical microvilli. Alternative effectors would include activation of the intrinsic and extrinsic innervation or other epithelial cell populations. The data available indicate that the role of the gastrointestinal innervation is relatively limited and is probably a major factor only in the postprandial responses of hormones released from endocrine cells in the distal small intestine. However, whether nutrients directly stimulate gastroenteric endocrine cells or another epithelial cell type has yet to be established.
Role of the PI3K/PKB signaling pathway in cAMP-mediated translocation of rat liver Ntcp
Authors: Webster Cynthia R. L. , Anwer M. Sawkat
Published: December 2017

cAMP stimulates Na+-taurocholate (TC) cotransport by translocating the Na+-TC-cotransporting peptide (Ntcp) to the plasma membrane. The present study was undertaken to determine whether the phosphatidylinositol-3-kinase (PI3K)-signaling pathway is involved in cAMP-mediated translocation of Ntcp. The ability of cAMP to stimulate TC uptake declined significantly when hepatocytes were pretreated with PI3K inhibitors wortmannin or LY-294002. Wortmannin inhibited cAMP-mediated translocation of Ntcp to the plasma membrane. cAMP stimulated protein kinase B (PKB) activity by twofold within 5 min, an effect inhibited by wortmannin. Neither basal mitogen-activated protein kinase (MAPK) activity nor cAMP-mediated inhibition of MAPK activity was affected by wortmannin. cAMP also stimulated p70S6Kactivity. However, rapamycin, an inhibitor of p70S6K, failed to inhibit cAMP-mediated stimulation of TC uptake, indicating that the effect of cAMP is not mediated via p70S6K. Cytochalasin D, an inhibitor of actin filament formation, inhibited the ability of cAMP to stimulate TC uptake and Ntcp translocation. Together, these results suggest that the stimulation of TC uptake and Ntcp translocation by cAMP may be mediated via the PI3K/PKB signaling pathway and requires intact actin filaments.
Regulation and function of p38 protein kinase in isolated canine gastric parietal cells
Authors: Pausawasdi N. , Ramamoorthy S. , Stepan V. , del Valle J. , Todisco A.
Published: December 2017

We examined the regulation and functional role of p38 kinase in gastric acid secretion. p38 kinase was immunoprecipitated from cell lysates of highly purified gastric parietal cells in primary culture, and its activity was quantitated by in vitro kinase assay. Carbachol effects were dose- and time-dependent, with a maximal 10-fold stimulatory effect detected after 30 min of incubation. SB-203580, a highly selective inhibitor of p38 kinase, blocked carbachol induction of p38 kinase activity, with maximal inhibition at 10 μM. Stimulation by carbachol was unaffected by preincubation of parietal cells with the intracellular Ca2+chelator BAPTA-AM, but incubation of cells in Ca2+-free medium led to a 50% inhibition of carbachol induction of p38 kinase activity. Because some of the effects of carbachol are mediated by the small GTP-binding protein Rho, we examined the role of Rho in carbachol induction of p38 kinase activity. We tested the effect of exoenzyme C3 from Clostridium botulinum (C3), a toxin known to ADP-ribosylate and specifically inactivate Rho. C3 led to complete ADP-ribosylation of Rho, and it inhibited carbachol induction of p38 kinase by 50%. We then tested the effect of SB-203580 and C3 on carbachol-stimulated uptake of [14C]aminopyrine (AP). Inhibition of p38 kinase by SB-203580 led to a dose-dependent increase in AP uptake induced by carbachol, with maximal (threefold) effect at 10 μM SB-203580. Similarly, preincubation of parietal cells with C3 led to a twofold increase in AP uptake induced by carbachol. Thus carbachol induces a cascade of events in parietal cells that results in activation of p38 kinase through signaling pathways that are at least in part dependent on Rho activation and on the presence of extracellular Ca2+. p38 kinase appears to inhibit gastric acid secretion.
V. Mechanisms of immunologic sensation of intestinal contents
Authors: Shanahan Fergus
Published: December 2017

Immune perception of intestinal contents reflects a functional dualism with systemic hyporesponsiveness to dietary antigens and resident microflora (oral tolerance) and active immune responses to mucosal pathogens. This facilitates optimal absorption of dietary nutrients while conserving immunologic resources for episodic pathogenic challenge. Discrimination between dangerous and harmless antigens within the enteric lumen requires continual sampling of the microenvironment by multiple potential pathways, innate and adaptive recognition mechanisms, bidirectional lymphoepithelial signaling, and rigorous control of effector responses. Errors in these processes disrupt mucosal homeostasis and are associated with food hypersensitivity and mucosal inflammation. Mechanisms of mucosal immune perception and handling of dietary proteins and other antigens have several practical and theoretical implications including vaccine design, therapy of systemic autoimmunity, and alteration of enteric flora with probiotics.
Ionizing radiation induces iNOS-mediated epithelial dysfunction in the absence of an inflammatory response
Authors: Freeman Samara L. , MacNaughton Wallace K.
Published: December 2017

Ionizing radiation induces intestinal epithelial hyporesponsiveness to secretagogues through an unknown mechanism. We investigated the role of the inducible isoform of nitric oxide (NO) synthase (iNOS)-derived NO in radiation-induced hyporesponsiveness. C57BL/6 mice were sham treated or exposed to 10-Gy γ-radiation and were studied 3 days later. Tissues were mounted in Ussing-type diffusion chambers to assess chloride secretion in response to electrical field stimulation (EFS) and forskolin (10 μM). Transport studies were also repeated in iNOS-deficient mice. White blood cell counts were significantly lower in irradiated mice, and there was no inflammatory response as shown by myeloperoxidase activity and histological assessment. iNOS mRNA levels and nitrate/nitrite concentrations were significantly elevated in irradiated colons. iNOS immunoreactivity localized to the epithelium. Colons from irradiated wild-type, but not iNOS-deficient, mice exhibited a significant reduction in the responsiveness of the tissue to EFS and forskolin. The hyporesponsiveness was reversed byl- N6-(1-iminoethyl)lysine, 1400W, and dexamethasone treatments. iNOS-derived NO mediates colonic hyporesponsiveness 3 days after irradiation in the mouse in the absence of an inflammatory response.
Antroduodenal motility in chronic pancreatitis: are abnormalities related to exocrine insufficiency?
Authors: Vu M. K. , Vecht J. , Eddes E. H. , Biemond I. , Lamers C. B. H. W. , Masclee A. A. M.
Published: December 2017

In patients with chronic pancreatitis (CP) the relation among exocrine pancreatic secretion, gastrointestinal hormone release, and motility is disturbed. We studied digestive and interdigestive antroduodenal motility and postprandial gut hormone release in 26 patients with CP. Fifteen of these patients had pancreatic insufficiency (PI) established by urinary para-aminobenzoic acid test and fecal fat excretion. Antroduodenal motility was recorded after ingestion of a mixed liquid meal. The effect of pancreatic enzyme supplementation was studied in 8 of the 15 CP patients with PI. The duration of the postprandial antroduodenal motor pattern was significantly ( P < 0.01) prolonged in CP patients (324 ± 20 min) compared with controls (215 ± 19 min). Antral motility indexes in the first hour after meal ingestion were significantly reduced in CP patients. The interdigestive migrating motor complex cycle length was significantly ( P < 0.01) shorter in CP patients (90 ± 8 min) compared with controls (129 ± 8 min). These abnormalities were more pronounced in CP patients with exocrine PI. After supplementation of pancreatic enzymes, these alterations in motility reverted toward normal. Digestive and interdigestive antroduodenal motility are abnormal in patients with CP but significantly different from controls only in those with exocrine PI. These abnormalities in antroduodenal motility in CP are related to maldigestion.
Patch-clamp study of neurons and glial cells in isolated myenteric ganglia
Authors: Hanani M. , Francke M. , Härtig W. , Grosche J. , Reichenbach A. , Pannicke T.
Published: December 2017

Most of the physiological information on the enteric nervous system has been obtained from studies on preparations of the myenteric ganglia attached to the longitudinal muscle layer. This preparation has a number of disadvantages, e.g., the inability to make patch-clamp recordings and the occurrence of muscle movements. To overcome these limitations we used isolated myenteric ganglia from the guinea pig small intestine. In this preparation movement was eliminated because muscle was completely absent, gigaseals were obtained, and whole cell recordings were made from neurons and glial cells. The morphological identity of cells was verified by injecting a fluorescent dye by micropipette. Neurons displayed voltage-gated inactivating inward Na+ and Ca2+currents as well as delayed-rectifier K+ currents. Immunohistochemical staining confirmed that most neurons have Na+ channels. Neurons responded to GABA, indicating that membrane receptors were retained. Glial cells displayed hyperpolarization-induced K+ inward currents and depolarization-induced K+ outward currents. Glia showed large “passive” currents that were suppressed by octanol, consistent with coupling by gap junctions among these cells. These results demonstrate the advantages of isolated ganglia for studying myenteric neurons and glial cells.
XI. Novel mouse models to study pathogenic mechanisms of Crohn's disease
Authors: Pizarro Theresa T. , Arseneau Kristen O. , Cominelli Fabio
Published: December 2017

Crohn's Disease (CD) affects more than 500,000 individuals in the United States and represents the second most common chronic inflammatory disorder after rheumatoid arthritis. Although major advances have been made in defining the basic mechanisms underlying chronic intestinal inflammation, the precise etiopathogenesis of CD remains unknown. We have recently characterized two novel mouse models of enteritis that express a CD-like phenotype, namely the TNF ΔARE model of tumor necrosis factor (TNF) overexpression and the SAMP1/Yit model of spontaneous ileitis. The unique feature of these models is that they closely resemble CD for location and histopathology. These genetically manipulated new models of intestinal inflammation offer a powerful tool to investigate potential causes of human disease and may allow the development of novel disease-modifying therapeutic modalities for the treatment of CD.
Murine colonic mucosa hyperproliferation. I. Elevated CFTR expression and enhanced cAMP-dependent Cl−secretion
Authors: Umar Shahid , Scott Jason , Sellin Joseph H. , Dubinsky William P. , Morris Andrew P.
Published: December 2017

Fluid transport in the large intestine is mediated by the cystic fibrosis gene product and cAMP-dependent anion channel cystic fibrosis transmembrane conductance regulator (CFTR). cAMP-mediated Cl−secretion by gastrointestinal cell lines in vitro has been positively correlated with the insertion of CFTR into the apical membrane of differentiated senescent colonocytes and negatively correlated with the failure of CFTR to insert into the plasma membrane of their undifferentiated proliferating counterparts. In native tissues, this relationship remains unresolved. We demonstrate, in a transmissible murine colonic hyperplasia (TMCH) model, that (8-fold) colonocyte proliferation was accompanied by increased cellular CFTR mRNA and protein expression (8.3- and 2.4-fold, respectively) and enhanced mucosal cAMP-dependent Cl−secretion (2.3-fold). By immunofluorescence microscopy, cellular CFTR expression was restricted to the apical pole of cells at the base of the epithelial crypt. In contrast, increased cellular proliferation in vivo led to increases in both the cellular level and the total number of cells expressing this anion channel, with cellular CFTR staining extending into the crypt neck region. Hyperproliferating colonocytes accumulated large amounts of CFTR in apically oriented subcellular perinuclear compartments. This novel mode of CFTR regulation may explain why high endogenous levels of cellular CFTR mRNA and protein within the TMCH epithelium were not matched with larger increases in transmucosal CFTR Cl−current.
Murine colonic mucosa hyperproliferation. II. PKC-β activation and cPKC-mediated cellular CFTR overexpression
Authors: Umar Shahid , Sellin Joseph H. , Morris Andrew P.
Published: December 2017

In the companion article (Umar S, Scott J, Sellin JH, Dubinsky WP, and Morris AP, Am J Physiol Gastrointest Liver Physiol 278: 753–764, 2000), we have shown that transmissible murine colonic hyperplasia (TMCH) increased cellular cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and protein expression, relocalized CFTR within colonocytes, and enhanced mucosal cAMP-dependent Cl−secretion. We show here that these changes were dependent on elevated cellular levels of membrane-bound Ca2+- and diacylglycerol-sensitive protein kinase C (PKC) activity (12-fold), induced by selective (3- to 4-fold) rises in conventional PKC (cPKC) isoform expression and membrane translocation. Three cPKC isoforms were detected in isolated crypts: α, β1, and β2. cPKC-β1 rises preceded and those of cPKC-α and cPKC-β2 paralleled cellular hyperproliferation and its effects on CFTR expression and cAMP-dependent Cl−current secretion. Only cPKC-β1 and cPKC-β2 were membrane translocated during TMCH. Furthermore, only cPKC-β1 trafficked to the nucleus, whereas cPKC-β2 remained partitioned among cytosolic, membrane, and cytoskeletal subcellular fractions. Modest increases in novel PKC-ε (nPKC-ε) expression and subcellular membrane partitioning were recorded during TMCH, but no changes were seen for PKC-δ or -η. No nPKC isoform nuclear partitioning was detected. The orally bioactive cPKC inhibitor Ro-32–0432 reversed both TMCH and elevated cellular CFTR mRNA levels, whereas a pharmacologically inert analog (Ro-31–6045) failed to inhibit either response. On the basis of these facts, we present a new hypothesis whereby PKC-dependent cellular proliferation promotes endogenous cellular CFTR levels. PKC-β1 was identified as a candidate regulatory PKC isoform.
IV. Visceral afferent contributions to the pathobiology of visceral pain
Authors: Gebhart G. F.
Published: December 2017

Functional bowel and other visceral disorders exhibit multiple characteristics that suggest the presence of visceral hyperalgesia. The discomfort, pain, and altered sensations (e.g., to intraluminal contents) that define the hyperalgesia typically arise in the absence of tissue insult or inflammation. Visceral hyperalgesia thus differs from somatic hyperalgesia, which is commonly associated with tissue injury and inflammation. Hyperalgesia could develop and be maintained by either peripheral or central mechanisms; the altered sensations associated with functional visceral disorders are contributed to by both peripheral and central mechanisms. The relative contributions of peripheral and central mechanisms are not well understood, and the focus in this Themes article is on potential peripheral contributions: sensitization of visceral receptors, nerve injury, and ion channels.
Regulation of E-selectin expression in postischemic intestinal microvasculature
Authors: Russell Janice , Epstein Charles J. , Grisham Matthew B. , Alexander J. Steven , Yeh Kwoh-Yih , Granger D. Neil
Published: December 2017

Monolayers of cultured endothelial cells exposed to hypoxia-reoxygenation exhibit a transcription-dependent increase in E-selectin expression and E-selectin-dependent neutrophil-endothelial cell adhesion. The overall objectives of this study were 1) to determine whether ischemia-reperfusion (I/R) promotes upregulation of E-selectin in vivo; 2) if so, to define the mediators of this response; and 3) to assess the contribution of E-selectin to I/R-induced neutrophil recruitment. The dual-radiolabeled monoclonal antibody (MAb) technique was used to measure E-selectin expression in the intestinal vasculature. Ischemia was induced by complete occlusion (30–60 min) of the superior mesenteric artery followed by 3–24 h of reperfusion. Increasing durations of ischemia elicited progressively increasing (2- to 5-fold) levels of E-selectin expression, with the peak response noted after 45 min of ischemia and 5 h of reperfusion. Subsequent experiments revealed that I/R-induced increase in E-selectin expression (at 5 h) is significantly blunted in transgenic mice that overexpress Cu,Zn-superoxide dismutase or by treatment of wild-type mice with either a blocking antibody against tumor necrosis factor (TNF)-α or an inhibitor of nuclear factor-κB (NF-κB) activation (PS341). Administration of an E-selectin-specific MAb dramatically reduced I/R-induced recruitment of neutrophils in the intestine. These findings suggest that superoxide and TNF-α mediate gut I/R-induced E-selectin expression via an NF-κB-dependent mechanism; this upregulation of E-selectin contributes significantly to I/R-induced neutrophil recruitment.
Receptor-induced Ca2+ signaling in cultured myenteric neurons
Authors: vanden Berghe Pieter , Tack Jan , Andrioli Antonius , Missiaen Ludwig , Janssens Jozef
Published: December 2017

We studied the effect of excitatory neurotransmitters (10− 5 M) on the intracellular Ca2+ concentration ([Ca2+]i) of cultured myenteric neurons. ACh evoked a response in 48.6% of the neurons. This response consisted of a fast and a slow component, respectively mediated by nicotinic and muscarinic receptors, as revealed by specific agonists and antagonists. Substance P evoked a [Ca2+]i rise in 68.2% of the neurons, which was highly dependent on Ca2+ release from intracellular stores, since after thapsigargin (5 μM) pretreatment only 8% responded. The responses to serotonin, present in 90.7%, were completely blocked by ondansetron (10− 5M), a 5-HT3 receptor antagonist. Specific agonists of other serotonin receptors were not able to induce a [Ca2+]i rise. Removing extracellular Ca2+ abolished all serotonin and fast ACh responses, whereas substance P and slow ACh responses were more persistent. We conclude that ACh-induced signaling involves both nicotinic and muscarinic receptors responsible for a fast and a more delayed component, respectively. Substance P-induced signaling requires functional intracellular Ca2+ stores, and the 5-HT3 receptor mediates the serotonin-induced Ca2+ signaling in cultured myenteric neurons.
Extracellular UTP stimulates electrogenic bicarbonate secretion across CFTR knockout gallbladder epithelium
Authors: Clarke Lane L. , Harline Matthew C. , Gawenis Lara R. , Walker Nancy M. , Turner John T. , Weisman Gary A.
Published: December 2017

The loss of cystic fibrosis transmembrane conductance regulator (CFTR)-mediated transepithelial HCO3 − secretion contributes to the pathogenesis of pancreatic and biliary disease in cystic fibrosis (CF) patients. Recent studies have investigated P2Y2 nucleotide receptor agonists, e.g., UTP, as a means to bypass the CFTR defect by stimulating Ca2+-activated Cl− secretion. However, the value of this treatment in facilitating transepithelial HCO3 − secretion is unknown. Gallbladder mucosae from CFTR knockout mice were used to isolate the Ca2+-dependent anion conductance during activation of luminal P2Y2receptors. In Ussing chamber studies, UTP stimulated a transient peak in short-circuit current ( I sc) that declined to a stable plateau phase lasting 30–60 min. The plateau I sc after UTP was Cl− independent, HCO3 − dependent, insensitive to bumetanide, and blocked by luminal DIDS. In pH stat studies, luminal UTP increased both I sc and serosal-to-mucosal HCO3 − flux ( J s→m) during a 30-min period. Substitution of Cl− with gluconate in the luminal bath to inhibit Cl−/HCO3 −exchange did not prevent the increase in J s→mand I sc during UTP. In contrast, luminal DIDS completely inhibited UTP-stimulated increases in J s→m and I sc. We conclude that P2Y2 receptor activation results in a sustained (30–60 min) increase in electrogenic HCO3 − secretion that is mediated via an intracellular Ca2+-dependent anion conductance in CF gallbladder.
Hepatic preconditioning preserves energy metabolism during sustained ischemia
Authors: Peralta C. , Bartrons R. , Riera L. , Manzano A. , Xaus C. , Gelpí E. , Roselló-Catafau J.
Published: December 2017

We evaluated the possibility that ischemic preconditioning could modify hepatic energy metabolism during ischemia. Accordingly, high-energy nucleotides and their degradation products, glycogen and glycolytic intermediates and regulatory metabolites, were compared between preconditioned and nonpreconditioned livers. Preconditioning preserved to a greater extent ATP, adenine nucleotide pool, and adenylate energy charge; the accumulation of adenine nucleosides and bases was much lower in preconditioned livers, thus reflecting slower adenine nucleotide degradation. These effects were associated with a decrease in glycogen depletion and reduced accumulation of hexose 6-phosphates and lactate. 6-Phosphofructo-2-kinase decreased in both groups, reducing the availability of fructose-2,6-bisphosphate. Preconditioning sustained metabolite concentration at higher levels although this was not correlated with an increased glycolytic rate, suggesting that adenine nucleotides and cAMP may play the main role in the modulation of glycolytic pathway. Preconditioning attenuated the rise in cAMP and limited the accumulation of hexose 6-phosphates and lactate, probably by reducing glycogen depletion. Our results suggest the induction of metabolic arrest and/or associated metabolic downregulation as energetic cost-saving mechanisms that could be induced by preconditioning.
Functional and molecular biological evidence of SGLT-1 in the ruminal epithelium of sheep
Authors: Aschenbach Jörg R. , Wehning Heike , Kurze Martina , Schaberg Elisabeth , Nieper Hermann , Burckhardt Gerhard , Gäbel Gotthold
Published: December 2017

Because of the effective catabolism ofd-glucose to short-chain fatty acids by intraruminal microorganisms, the absorption of d-glucose from the rumen was thought to be of minor importance. However, clinical studies suggested that significant quantities of d-glucose are transported from the ruminal contents to the blood. We therefore tested the ruminal epithelium of sheep for the presence of Na+-glucose cotransporter 1 (SGLT-1) on both the functional and mRNA levels. In the absence of an electrochemical gradient, 3- O-methylglucose (3-OMG) was net absorbed across isolated ruminal epithelia mounted in Ussing chambers. The net transport of 3-OMG followed Michaelis-Menten kinetics and was sensitive to phlorizin or decreasing Na+concentrations. The mucosal addition of 10 mM d-glucose induced an immediate, phlorizin-sensitive increase in short-circuit current ( Isc). Isccould also be increased by serosal addition of d-glucose or d-mannose, but electrogenic uptake of d-glucose or 3-OMG added on the mucosal side was still detectable after serosal stimulation of Isc. RT-PCR using primers specific for the ovine intestinal SGLT-1 with subsequent TA cloning and sequencing revealed 100% identity between the cloned cDNA and mRNA fragment 187–621 of ovine intestinal SGLT-1. In conclusion, the ruminal epithelium has a high-affinity SGLT-1, which indicates that it maintains the capacity for d-glucose absorption.
Cyclooxygenase-2-derived prostaglandin D2is an early anti-inflammatory signal in experimental colitis
Authors: Ajuebor Maureen N. , Singh Anita , Wallace John L.
Published: December 2017

The ability of nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors to exacerbate inflammatory bowel disease suggests that prostaglandins are important anti-inflammatory mediators in this context. Prostaglandin D2has been suggested to exert anti-inflammatory effects. We investigated the possibility that prostaglandin D2derived from cyclooxygenase-2 plays an important role in downregulating colonic inflammation in rats. Colitis was induced by intracolonic administration of trinitrobenzene sulfonic acid. At various times thereafter (from 1 h to 7 days), colonic prostaglandin synthesis and myeloperoxidase activity (index of granulocyte infiltration) were measured. Prostaglandin D2synthesis was elevated >4-fold above controls within 1–3 h of induction of colitis, preceding significant granulocyte infiltration. Treatment with a selective cyclooxygenase-2 inhibitor abolished the increase in prostaglandin D2synthesis and caused a doubling of granulocyte infiltration. Colonic granulocyte infiltration was significantly reduced by administration of prostaglandin D2or a DP receptor agonist (BW-245C). These results demonstrate that induction of colitis results in a rapid increase in prostaglandin D2synthesis via cyclooxygenase-2. Prostaglandin D2downregulates granulocyte infiltration into the colonic mucosa, probably through the DP receptor.