bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential symptomatic and electrogastrographic effects of distal and proximal human gastric distension
Authors: Ladabaum Uri , Koshy Sherin S. , Woods Michelle L. , Hooper Forrest G. , Owyang Chung , Hasler William L.
Published: December 2017

Nausea and gastric dysrhythmias occur in conditions associated with gastric distension. The roles of distal and proximal gastric mechanoreceptors in these responses are unexplored. Because antral distension induces vomiting in animals and antral and fundic vagal afferent discharges differ, we hypothesized that distal gastric distension in humans leads to greater symptomatic and dysrhythmic responses than proximal distension. Symptoms and electrogastrograms were recorded in healthy humans during distal and proximal gastric distension with a barostat. Distal but not proximal distension induced nausea and a 747 ± 250% increase in dysrhythmic power ( P < 0.05), responses not affected by granisetron, indomethacin, or atropine, agents that block dysrhythmias in other settings. In the distal stomach, bloating and pain developed at lower pressures ( P < 0.05) not modified by granisetron, and compliance was significantly lower ( P < 0.05). In conclusion, gastric mechanoreceptor activation in the less-compliant distal stomach produces nausea and dysrhythmias via non-5-hydroxytryptamine3(5-HT3), non-prostaglandin-dependent, and noncholinergic pathways. Distal mechanoreceptor activation induces greater bloating and pain than proximal mechanoreceptor activation via 5-HT3-independent pathways.
Transforming growth factor-β inhibits proliferation and maturation of cultured guinea pig gastric pit cells
Authors: Rokutan Kazuhito , Yamada Masahiko , Torigoe Jyunko , Saito Toshihiko
Published: December 2017

We studied the effects of transforming growth factor-β1 (TGF-β1) on guinea pig gastric mucous cells, cultured in serum-free conditions. Electron microscopy showed that most cells were pre-pit cells, characterized by the presence of a few secretory granules scattered in the cytoplasm. Epidermal growth factor (EGF) stimulated cell growth, [3H]glucosamine uptake, and accumulation of mucus granules positive for galactose oxidase-Schiff reaction. This EGF-induced maturation into pit cells was confirmed morphologically by the appearance of uniformly dense ovoid or spherical mucus granules packed in the ectoplasm. Western blotting with an antiphosphotyrosine antibody showed that TGF-β1 did not inhibit the EGF-initiated tyrosine phosphorylation of the EGF receptor. Northern blotting with cDNA probes for c- fos and c- myc demonstrated that TGF-β1 did not affect the EGF-induced expression of the transcripts. However, TGF-β1-treated cells did not replicate and remained in an immature stage, even in the presence of EGF, suggesting a potential role of TGF-β1 in the regulation of proliferation and differentiation of a pit cell lineage in vivo.
Uptake and metabolism of structured triglyceride by Caco-2 cells: reversal of essential fatty acid deficiency
Authors: Spalinger Johannes H. , Seidman Ernest G. , Lepage Guy , Ménard Daniel , Gavino Victor , Levy Emile
Published: December 2017

Structured lipids have been proposed as efficient vehicles for the supplementation of essential fatty acids (EFA) to patients with malabsorption. We investigated how a novel structured triglyceride (STG), containing purely octanoic acid in the sn-1/ sn-3 and [14C]linoleic acid in the sn-2 positions, was incorporated into different lipid classes in Caco-2 cells. We also evaluated the contribution of gastric lipase in the uptake and metabolism of [14C]linoleic acid from the STG. We furthermore determined the potential of the STG to correct EFA deficiency induced in Caco-2 cells. The absorption of STG by Caco-2 cells was significantly greater compared with that of triolein. The addition of human gastric lipase significantly enhanced cellular uptake of the labeled substrate, reflecting the stereoselectivity of gastric lipase to hydrolyze medium chain FA. Analysis of the intracellular lipids synthesized revealed a predominance of phospholipids-monoglycerides. Most of the radioactivity in the lipoproteins isolated from Caco-2 cells was recovered in TG-rich lipoproteins (45%) and to a lesser extent in the high-density lipoprotein (36%) and low-density lipoprotein (17%) fractions. The administration of STG to Caco-2 cells rendered EFA deficient produced a marked increase of the cellular level of linoleic and arachidonic acids. This resulted in a lower ratio of 20:3(n-9) to 20:4(n-6), reflecting the correction of EFA deficiency in Caco-2 cells. Our data demonstrate that STG, in the presence of gastric lipase, have beneficial effects on lipid incorporation, lipoprotein production, and EFA status, utilizing Caco-2 cells as a model of EFA deficiency.
Histamine sensitivity of mesenteric afferent nerves in the rat jejunum
Authors: Kreis M. E. , Haupt W. , Kirkup A. J. , Grundy D.
Published: December 2017

The concept of functional interaction between mast cells and intestinal afferents is gaining support. We have therefore characterized the action of histamine on jejunal afferent discharge in the anesthetized rat. Whole nerve mesenteric afferent discharge was recorded in conjunction with intestinal pressure in response to a range of histamine agonists and antagonists. Histamine at 2, 4, and 8 μmol/kg (iv) evoked a dose-dependent biphasic increase in afferent discharge together with a biphasic rise in intestinal pressure. However, these two events were mediated independently, since nifedipine (1 mg/kg) substantially reduced the intestinal pressure increase but not the afferent discharge. These responses were completely inhibited by pyrilamine (5 mg/kg) but unaffected by ranitidine (5 mg/kg) or thioperamide (2 mg/kg). Neither the selective H2receptor agonist dimaprit nor the selective H3receptor agonist R-α-methylhistamine caused any modulation of afferent discharge. We conclude that histamine stimulates an H1receptor-mediated increase in mesenteric afferent discharge that is independent of intestinal motor events. This suggests that histamine potentially acts as a mediator in mast cell-to-afferent nerve communication in the small intestine.
Hepatocellular expression of glucose-6-phosphatase is unaltered during hepatic regeneration
Authors: Zakko Wisam F. , Berg Carl L. , Gollan John L. , Green Richard M.
Published: December 2017

Gluconeogenesis and glycogenolysis are essential hepatic functions required for glucose homeostasis. During the initial phase of hepatic regeneration, the immediate-early genes (IEG) are rapidly expressed, and the IEG RL-1 encodes for glucose-6-phosphatase (G-6- Pase). G-6- Pase is a microsomal enzyme essential for gluconeogenesis and glycogenolysis. This study employs a partial-hepatectomy model to examine the expression and activity of G-6- Pase. After partial hepatectomy, rat hepatic G-6- Pase gene expression is transcriptionally regulated, and mRNA levels are increased ≈30-fold. However, in contrast to this rapid gene induction, microsomal enzyme activity is unchanged after partial hepatectomy. Western blotting demonstrates that microsomal G-6- Pase protein expression is also unchanged after partial hepatectomy, and similar results are also noted in whole liver homogenate. Thus, despite marked induction in gene expression of the IEG G-6- Pase after partial hepatectomy, protein expression and enzyme activity remain unchanged. These data indicate that, although this hepatocyte IEG is transcriptionally regulated, the physiologically important level of regulation is posttranscriptional. This highlights the importance of correlating gene expression of IEG with protein expression and physiological function.
Rat hepatic stellate cells produce cytokine-induced neutrophil chemoattractant in culture and in vivo
Authors: Maher Jacquelyn J. , Lozier John S. , Scott Myron K.
Published: December 2017

Hepatic stellate cells are widely recognized for their contribution to liver fibrosis. This study investigated whether these cells also promote hepatic inflammation by producing neutrophil chemoattractants. Specifically, stellate cells were examined as potential sources of cytokine-induced neutrophil chemoattractant (CINC), a rat chemokine resembling human interleukin-8. Stellate cells from normal rat liver expressed little or no CINC. In culture, CINC mRNA was induced rapidly, coinciding with the phenomenon of culture activation. CINC mRNA rose 4.6-fold within 3 days and was accompanied by secretion of immunoreactive and biologically active CINC protein (4.1 ng ⋅ μg DNA−1⋅ day−1). Studies in vivo demonstrated that CINC could be induced in stellate cells during liver injury. CINC mRNA rose significantly (4- to 6-fold) in two models of liver disease, both of which cause stellate cell activation. In summary, the data indicate that CINC is induced during stellate cell activation in culture and in vivo. They suggest that stellate cell-derived CINC can promote hepatic inflammation in vivo.
Effects of neurotransmitters, gut hormones, and inflammatory mediators on mucus discharge in rat colon
Authors: Plaisancié Pascale , Barcelo Aline , Moro Frederic , Claustre Jean , Chayvialle Jean-Alain , Cuber Jean-Claude
Published: December 2017

The effect of potential mediators of mucus secretion was investigated in the isolated vascularly perfused rat colon by using a sandwich enzyme-linked immunosorbent assay for rat colonic mucin and by histochemical analysis. Bethanechol (100–200 μM), bombesin (100 nM), and vasoactive intestinal peptide (VIP, 100 nM) provoked a dramatic mucin discharge (maximal response at 900, 900, and 600% of control loops, respectively). VIP-stimulated mucin secretion was abolished by tetrodotoxin, whereas atropine was without effect. In contrast, both tetrodotoxin and atropine significantly decreased mucin release induced by bombesin. Isoproterenol or calcitonin gene-related peptide was without effect. Serotonin (1–5 μM) and peptide YY (10 nM) evoked mucin discharge, whereas glucagon-like peptide-1 did not release mucin. Finally, bromolasalocid (20 μM), interleukin-1β (0.25 nM), sodium nitroprusside (1 mM), and dimethyl-PGE2(2.5 μM) induced mucus discharge. The results demonstrated a good correlation between the immunological method and histological analysis. In conclusion, these findings suggest a role for the enteric nervous system, the enteroendocrine cells, and resident immune cells in mediation of colonic mucus release.
Functional alterations in jejunal myenteric neurons during inflammation in nematode-infected guinea pigs
Authors: Palmer Jeffrey M. , Wong-Riley Margaret , Sharkey Keith A.
Published: December 2017

Intracellular recordings of jejunal myenteric neurons with an afterspike hyperpolarization (AH) from Trichinella spiralis-infected animals showed enhanced excitability on days 3, 6, and 10postinfection (PI) compared with uninfected animals. Lower membrane potential, increased membrane input resistance, decreased threshold for action potential discharge, decreased AH amplitude and duration, and increased fast excitatory postsynaptic potential amplitude and duration were characteristic of neuronal recordings from infected animals. Concurrent with electrophysiological changes during T. spiralis infection, increased cytochrome oxidase activity, a marker of neuronal metabolic activity, and the expression of nuclear c-Fos immunoreactivity, an indicator of transcriptional-translational activity, were also observed in myenteric ganglion cells. Double-labeling for calbindin-immunoreactive myenteric neurons revealed that ∼50% of these neurons also expressed increased c-Fos immunoreactivity during T. spiralis infection. Myeloperoxidase activity was significantly higher in the jejunum of T. spiralis-infected guinea pigs on days 3, 6, and 10 PI vs. uninfected counterparts. The expression of c-Fos in calbindin-immunoreactive neurons together with enhanced neuronal electrical and metabolic activity during nematode-induced intestinal inflammation suggests the onset of excitation-transcription coupled changes in enteric neural microcircuits.
IV. Pathogenetic mechanisms involved in hepatitis C virus-induced liver diseases
Authors: Lau Johnson Yiu-Nam
Published: December 2017

The pathogenetic mechanisms for liver damage in acute hepatitis C are not clear, but a host immune cellular response may be involved. In chronic hepatitis C, there is strong evidence that host cellular immune response is involved in the control of viral replication and contributes to hepatocellular damage. As hepatitis C virus infection persists, continuous liver damage and regeneration, together with enhanced fibrogenesis, may eventually lead to cirrhosis in a proportion of patients. Transplant patients on high-dose immunosuppression may have high-level intrahepatic hepatitis C viral expression, and, in this setting, the virus may induce direct cytopathic liver damage.
Functional polarity of Na+/H+and Cl−/ HCO 3 − exchangers in a rat cholangiocyte cell line
Authors: Spirlì Carlo , Granato Anna , Zsembery Àkos , Anglani Franca , Okolicsànyi Lajos , LaRusso Nicholas F. , Crepaldi Gaetano , Strazzabosco Mario
Published: December 2017

Intrahepatic bile duct cells (cholangiocytes) play an important role in the secretion and alkalinization of bile. Both Na+/H+exchange (NHE) and Cl−/[Formula: see text]exchange (AE) contribute to these functions, but their functional distribution between the apical and basolateral membrane domains remains speculative. We have addressed this issue in a normal rat cholangiocyte cell line (NRC-1), which maintains a polarized distribution of membrane markers. Gene expression of AE and NHE isoforms was studied by RT-PCR. For functional studies, cells were placed in a chamber that allowed separate perfusion of the apical and basolateral aspect of the epithelial sheet; intracellular pH (pHi) was measured by 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein microfluorometry. In[Formula: see text]-CO2free medium and in the presence of apical amiloride, pHirecovery from an acid load was Na+dependent and was inhibited by basolateral amiloride and by HOE-642 (10 μM), consistent with basolateral localization of the NHE1 isoform, which had clearly expressed mRNA. Apical Na+readmission induced a slow pHirecovery that was inhibited by apical administration of 1 mM HOE-642 or amiloride. Among the apical NHE isoforms, NHE2 but not NHE3 gene expression was detected. The AE1 gene was not expressed, but two different variants of AE2 mRNAs (AE2a and AE2b) were detected; pHiexperiments disclosed AE activities at both sides of the membrane, but only apical AE was activated by cAMP. In conclusion, these studies provide the first functional description of acid-base transporters in a polarized cholangiocyte cell line. NHE1, NHE2, AE2a, and AE2b isoforms are expressed and show different membrane polarity, functional properties, and sensitivity to inhibitors. These observations add a considerable level of complexity to current models of electrolyte transport in cholangiocytes.
Migrating motor complex cycle duration is determined by gastric or duodenal origin of phase III
Authors: Luiking Yvette C. , van der Reijden Astrid C. , van Berge Henegouwen Gerard P. , Akkermans Louis M. A.
Published: December 2017

The migrating motor complex (MMC) shows large variations within an individual and between individuals. This study aimed to investigate, with respect to this variability, the importance of gastric or duodenal origin of phase III activity. Interdigestive 6- to 10-h stationary antroduodenal motility recordings of 19 healthy male subjects were analyzed for MMC cycle durations and duration of phases I, II, and III, all with respect to the place of origin of each phase III. Data are given for the duodenal recording site as means ± SE. Mean MMC cycle duration was 117.3 ± 13.9 min, regardless of the place of origin of phase III. Seventy-two phase III cycles were observed in total, 35 and 37 starting in the “antrum” and duodenum, respectively. After a phase III of “antral” origin, MMC cycle duration was 156.1 ± 11.0 min, significantly longer than MMC cycle duration following a phase III of duodenal origin, 80.5 ± 10.7 min ( P < 0.001). Phase III duration was longer when of “antral” origin than when starting in the duodenum (7.6 ± 0.4 and 5.3 ± 0.4 min, respectively; P < 0.001). MMC cycle duration and duration of phases I, II, and III depend on the place of origin of phase III (“antral” or duodenal) and on the origin of the preceding phase III. This factor explains part of the MMC variability observed within individuals. Mean MMC cycle duration in healthy subjects or patients should therefore also include information on the origin of phase III.
IGFBP-3 and IGFBP-5 production by human intestinal muscle: reciprocal regulation by endogenous TGF-β1
Authors: Bushman Toni L. , Kuemmerle John F.
Published: December 2017

Insulin-like growth factor-I (IGF-I)-mediated growth of cells can be modulated by specific IGF binding proteins (IGFBPs) that inhibit or augment IGF-I ligand-receptor interaction. IGFBP expression and production by human intestinal muscle cells in culture was characterized in rapidly growing cells ( day 3 of culture), in confluent cells ( day 7), and in postconfluent cells ( day 14). RT-PCR analysis identified IGFBP-3, IGFBP-4, and IGFBP-5 mRNA during all three phases of growth. The production of IGFBP-3 and IGFBP-5 was regulated in reciprocal fashion. IGFBP-5 production was high on day 3and decreased two- to fivefold by day 14, and IGFBP-3 production was low on day 3and increased five- to eightfold by day 14. IGFBP-4 production remained constant. IGFBP-3 inhibited and IGFBP-5 augmented IGF-I-induced proliferation. IGFBP-3 and IGFBP-5 production was regulated in reciprocal fashion by transforming growth factor-β1 (TGF-β1). Immunoneutralization of endogenous TGF-β1 decreased the production of IGFBP-3 and increased the production of IGFBP-5. Addition of exogenous recombinant human TGF-β1 had the opposite effect. We conclude that the expression and time-dependent production of IGFBP-3, IGFBP-4, and IGFBP-5 and their regulation by endogenous TGF-β1 represent mechanisms by which human intestinal muscle cells regulate autocrine IGF-I-mediated growth.
Hepatic oxygen metabolism in porcine endotoxemia: the effect of nitric oxide synthase inhibition
Authors: Saetre Torunn , Gundersen Yngvar , Smiseth Otto A. , Scholz Tim , Carlsen Hege , Nordsletten Lars , Lilleaasen Per , Sautner Thomas , Függer Reinhold , Aasen Ansgar O.
Published: December 2017

The role of endotoxin (lipopolysaccharide, LPS) and nitric oxide in hepatic oxygen metabolism was investigated in 36 pigs receiving 1) LPS (1.7 μg ⋅ kg−1 ⋅ h−1) for 7 h and N G-nitro-l-arginine methyl ester (l-NAME; 25 mg/kg) after 3 h, 2) LPS, 3) NaCl andl-NAME, and 4) NaCl. Infusion of LPS reduced hepatic oxygen delivery (Do 2H) from 60 ± 4 to 30 ± 5 ml/min ( P < 0.05) and increased the oxygen extraction ratio from 0.29 ± 0.07 to 0.68 ± 0.04 after 3 h ( P < 0.05). Hepatic oxygen consumption (V˙o 2H) was maintained (18 ± 4 and 21 ± 4 ml/min, change not significant), but acidosis developed. Administration ofl-NAME during endotoxemia caused further reduction of Do 2H from 30 ± 3 to 13 ± 2 ml/min ( P < 0.05) and increased hepatic oxygen extraction ratio from 0.46 ± 0.04 to 0.80 ± 0.03 ( P< 0.05). There was a decrease inV˙o 2H from 13 ± 2 to 9 ± 2 ml/min that did not reach statistical significance, probably representing a type II error. Acidosis was aggravated. Administration of l-NAME in the absence of endotoxin also increased the hepatic oxygen extraction ratio, but no acidosis developed. In a different experiment, liver blood flow was mechanically reduced in the presence and absence of endotoxin, comparable to the flow reductions caused byl-NAME. The increase in hepatic oxygen extraction ratio (0.34) and maximum hepatic oxygen extraction ratio (∼0.90) was similar whether Do 2H was reduced by occlusion or byl-NAME. We concluded thatl-NAME has detrimental circulatory effects in this model. However, neither endotoxin norl-NAME seemed to prevent the ability of the still circulated parts of the liver to increase hepatic oxygen extraction ratio to almost maximum when oxygen delivery was reduced. The effect of l-NAME on oxygen transport thus seems to be caused by a reduction in Do 2H rather than by alterations in oxygen extraction capabilities.
Expression of extracellular glutathione peroxidase in human and mouse gastrointestinal tract
Authors: Tham Doris M. , Whitin John C. , Kim Kenneth K. , Zhu Shirley X. , Cohen Harvey J.
Published: December 2017

Extracellular glutathione peroxidase (EGPx) is a glycosylated selenoprotein capable of reducing hydrogen peroxide, organic hydroperoxides, free fatty acid hydroperoxides, and phosphatidylcholine hydroperoxides. We found that human large intestinal explant cultures synthesize EGPx and cellular glutathione peroxidase (CGPx) and secrete EGPx. The level of EGPx mRNA expression relative to α-tubulin was similar throughout the mouse gastrointestinal tract. EGPx mRNA transcripts have been localized to mature absorptive epithelial cells in human and mouse large intestine. Western blot analysis of mouse intestinal protein has demonstrated the presence of EGPx protein in the small intestine, cecum, and large intestine, with the highest protein levels found in the cecum. Immunohistochemistry studies of human large intestine and mouse small and large intestine sections demonstrated the presence of EGPx protein within mature absorptive epithelial cells. In human large intestine and mouse small intestine, EGPx protein is also present in the extracellular milieu. These results suggest a role for EGPx in protection of the intestinal tract from peroxidative damage and/or in intercellular metabolism of peroxides.
Mechanism of inhibition of VIP-induced LES relaxation by heme oxygenase inhibitor zinc protoporphyrin IX
Authors: Rattan Satish , Fan Ya-Ping , Chakder Sushanta
Published: December 2017

The putative heme oxygenase inhibitor zinc protoporphyrin IX (ZnPP IX) is known to exert diverse actions, including inhibitory action on smooth muscle relaxation by vasoactive intestinal polypeptide (VIP). The studies were performed in the opossum lower esophageal sphincter (LES) smooth muscle to determine the site of the inhibitory action of ZnPP IX in the smooth muscle relaxation by VIP. We also examined the effect of a direct Gsprotein activator, cholera toxin (CTX), known to stimulate adenylate cyclase (AC). CTX caused relaxation of the LES smooth muscle by its action directly at the smooth muscle cells. The convergence of the common mechanisms of actions of VIP and CTX on AC was determined by the suppression of their effects by the AC inhibitor and CTX desensitization. ZnPP IX caused attenuation of the LES smooth muscle relaxation by VIP but not by CTX. ZnPP IX but not zinc deuteroporphyrin IX caused significant inhibition of VIP binding to the membrane receptor. We conclude that ZnPP IX attenuates VIP-induced LES smooth muscle relaxation by inhibition of VIP binding to G protein-coupled receptors linked to AC at a point proximal to G protein activation.
Jejunal mucosal protein synthesis: validation of luminal flooding dose method and effect of luminal osmolarity
Authors: Adegoke Olasunkanmi A. J. , McBurney Michael I. , Baracos Vickie E.
Published: December 2017

To validate a system to study acute regulation of protein synthesis in intestinal mucosa by luminal nutrients, we compared the fractional rate of protein synthesis ( K s) in jejunal mucosa using the intravenous flooding dose technique with the administration of a comparable concentration and specific activity of tracer in a luminal perfusate. Routes of tracer administration and surgery and perfusion trauma had no effect on mucosal K s. Furthermore, four 10-cm jejunal segments (within a piglet) simultaneously but separately perfused with a luminal flooding dose had similar K s values (mean, 43 ± 2%/day; P > 0.05). Nutrient solutions perfused through four intestinal segments within an animal did not affect plasma levels of most amino acids or glucose. Because cellular hydration is important in regulating metabolism, the effects of physiological variation in luminal osmolarity were studied. Luminal osmolarities between 250 and 380 mosM did not affect mucosal K s. The system described allows multiple comparisons within an animal and provides a robust model to study acute modulation of protein synthesis in intestinal mucosa by luminal stimuli.
Endogenous glucocorticoids released during acute toxic liver injury enhance hepatic IL-10 synthesis and release
Authors: Swain Mark G. , Appleyard Caroline , Wallace John , Wong Howard , Le Tai
Published: December 2017

Endogenous glucocorticoids are known to play a role in the regulation of the inflammatory response possibly by modulating pro- and anti-inflammatory cytokine expression. We examined endogenous glucocorticoid secretion, hepatic damage, tumor necrosis factor-α (TNF-α), and interleukin-10 (IL-10) mRNA expression and release in rats treated with carbon tetrachloride (CCl4) after treatment with vehicle or a glucocorticoid receptor antagonist (RU-486). Rats treated with CCl4demonstrated striking elevations of plasma corticosterone levels. Inhibition of endogenous glucocorticoid activity by pretreatment with the glucocorticoid receptor antagonist RU-486 resulted in augmented CCl4-mediated hepatotoxicity, as reflected by histology and serum transaminase levels, which were independent of alterations in serum TNF-α levels or hepatic mRNA expression. CCl4treatment resulted in enhanced hepatic IL-10 mRNA expression and elevated serum IL-10 levels, which were markedly attenuated by glucocorticoid receptor blockade. In summary, significant endogenous glucocorticoid release occurs during acute toxic liver injury in the rat and suppresses the inflammatory response independent of effects on TNF-α but possibly by upregulating hepatic IL-10 production.
Role of endotoxin in intestinal reperfusion-induced expression of E-selectin
Authors: Bauer Philippe , Russell Janice M. , Granger D. Neil
Published: December 2017

Products of enteric bacteria, including endotoxin [lipopolysaccharide (LPS)], have been implicated in the acute inflammatory responses elicited by ischemia and reperfusion (I/R) of the small intestine. The objective of this study was to assess the contribution of LPS to the increased E-selectin expression observed in the intestinal vasculature after I/R. The dual radiolabeled monoclonal antibody technique was used in LPS-sensitive (C3HeB/FeJ) and LPS-insensitive (C3H/HeJ) mice that were exposed to either exogenous LPS or to gut I/R (45 min ischemia, 5 h reperfusion). LPS elicited a dose-dependent (0.5–50 μg LPS/animal) increase in E-selectin expression (at 3 h) in LPS-sensitive mice, whereas LPS-insensitive mice were largely unresponsive. E-selectin expression was increased fivefold by I/R in the small bowel of both LPS-sensitive and -insensitive mice. These results indicate that, although exogenous LPS is capable of eliciting profound dose-dependent increases in E-selectin expression, endogenous LPS does not contribute significantly to I/R-induced expression of this endothelial cell adhesion molecule.
Analysis of fast synaptic pathways in myenteric plexus of guinea pig ileum
Authors: LePard Kathy J. , Galligan James J.
Published: December 2017

Most fast excitatory postsynaptic potentials (fEPSPs) recorded from guinea pig ileum myenteric plexus are mediated by acetylcholine acting at nicotinic receptors and ATP acting at P2X receptors. These studies examine length and polarity of projection of neurons releasing mediators of fEPSPs. Under ketamine-xylazine anesthesia, animals were sham treated or myenteric pathways were interrupted. After severed axons degenerated, fEPSPs were recorded at the operated site using conventional, intracellular electrophysiological methods and were classified as nicotinic or mixed on the basis of sensitivity to hexamethonium. Cholinergic and noncholinergic fEPSPs were recorded from small, operated segments, suggesting that some neurons have projections between adjacent ganglia. The mean amplitudes of nicotinic and mixed fEPSPs were reduced after circumferential and descending pathways degenerated. The proportion of nicotinic vs. mixed fEPSPs recorded from tissues lacking descending projections was greater than that recorded from sham-treated tissues, suggesting that fibers releasing noncholinergic mediators project aborally. Descending projections communicate with neurons in ganglia at least three rows aboral to their origin. The data suggest that fast noncholinergic neurotransmission could contribute to hexamethonium-resistant descending inhibition during the peristaltic reflex.
II. Nitric oxide protects in intestinal inflammation
Authors: Lefer Allan M. , Lefer David J.
Published: December 2017

This article examines the evidence for nitric oxide (NO) as a protective agent in splanchnic ischemia-reperfusion and other forms of acute intestinal inflammation. Four major points emerge from this body of data. First, acute intestinal inflammation results in an early (i.e., <5 min) and severe decrease in endothelium-derived NO. Thus the early trigger event in this condition is a functional loss of NO. Second, administration of exogenous NO, NO donors, or NO precursors ameliorate splanchnic ischemia-reperfusion and other forms of acute intestinal inflammation (i.e., splanchnic trauma). These beneficial effects occur at physiological levels of NO when given early in the course of the inflammatory state. Third, blockade of nitric oxide synthase (NOS) or gene deletion of NOS exacerbates intestinal inflammation. Fourth, there are a variety of signaling mechanisms that may mediate the protective effect of NO.
Hepatocyte-specific localization and copper-dependent trafficking of the Wilson’s disease protein in the liver
Authors: Schaefer Mark , Hopkins Robin G. , Failla Mark L. , Gitlin Jonathan D.
Published: December 2017

Wilson’s disease is an inherited disorder of copper metabolism characterized by hepatic cirrhosis and neuronal degeneration. In this current study, a polyclonal antiserum specific for the Wilson’s disease ATPase was used to examine the hepatic expression of this protein. Immunoblot analysis of lysates from human and rat liver detected a single 165-kDa protein, which by immunofluorescence was present only in hepatocytes and localized predominantly to the trans-Golgi network and exclusively in this compartment under low hepatic copper concentrations. Although hepatic copper concentration had no effect on the steady-state levels of the Wilson’s disease protein, copper administration in vivo resulted in redistribution of this protein to a cytoplasmic vesicular compartment localized toward the hepatocyte canalicular membrane. The relative abundance of the Wilson’s disease protein in the liver was found to be greatest in the fetus before the onset of biliary copper excretion. Taken together, these studies reveal a novel posttranslational mechanism of copper homeostasis in vivo consistent with the proposed function of the Wilson’s disease protein in holoceruloplasmin biosynthesis and biliary copper excretion and of relevance to the broad clinical heterogeneity observed in this disease.
β2-Adrenergic receptor-selective agonist clenbuterol prevents Fas-induced liver apoptosis and death in mice
Authors: André Claudine , Couton Dominique , Gaston Jesintha , Erraji Loubna , Renia Laurent , Varlet Paule , Briand Pascale , Guillet Jean-Gérard
Published: December 2017

Stimulation of the cAMP-signaling pathway modulates apoptosis in several cell types and inhibits Jo2-mediated apoptosis in cultured rat hepatocytes. No information is yet available as to whether the hepatic β2-adrenergic receptor (AR) expression level, including β2-AR-dependent adenylyl cyclase activation, modulates hepatocyte sensitivity to apoptosis in vivo or whether this sensitivity can be modified by β2-AR ligands. We have examined this using C57BL/6 mice, in which hepatic β2-AR densities are low, and transgenic F28 mice, which overexpress β2-ARs and have elevated basal liver adenylyl cyclase activity. The F28 mice were resistant to Jo2-induced liver apoptosis and death. The β-AR antagonist propranolol sensitized the F28 livers to Jo2. In normal mice clenbuterol, a β2-AR-specific agonist, considerably reduced Jo2-induced liver apoptosis and death; salbutamol, another β2-AR-selective agonist, also reduced Jo2-induced apoptosis and retarded death but with less efficacy than clenbuterol; and propranolol blocked the protective effect of clenbuterol. This indicates that the expression level of functional β2-ARs modulates Fas-regulated liver apoptosis and that this apoptosis can be inhibited in vivo by giving β2-AR agonists. This may well form the basis for a new therapeutic approach to diseases involving abnormal apoptosis.
Factors mediating the hemodynamic effects of tumor necrosis factor-α in portal hypertensive rats
Authors: Muñoz Javier , Albillos Agustín , Pérez-Páramo María , Rossi Irma , Alvarez-Mon Melchor
Published: December 2017

Nitric oxide, prostacyclin, and glucagon have been implicated in promoting the hyperdynamic circulatory state of portal hypertension. Recent evidence also indicates that increased tumor necrosis factor-α (TNF-α) production is involved in the pathogenesis of this hemodynamic abnormality. This study was aimed at investigating in rats with portal vein stenosis (PVS) the effects on splanchnic hemodynamics of blocking circulating TNF-α and the factors mediating the vascular action of this cytokine in this setting. Anti-TNF-α polyclonal antibodies or placebo was injected into rats ( n = 96) before and 4 days after PVS (short-term inhibition) and at 24 h and 4, 7, 10 days after PVS (long-term inhibition). Short-term TNF-α inhibition reduced portal venous inflow and cardiac index and increased splanchnic and systemic resistance. Portal pressure was unchanged, but portal-systemic shunting was decreased. After long-term TNF-α inhibition, portal venous inflow and portal pressure were unchanged, but arterial pressure and systemic resistance rose significantly. Anti-TNF-α PVS rats exhibited lower increments of systemic resistance after N ω-nitro-l-arginine methyl ester and indomethacin administration and lower serum levels of TNF-α, nitrates-nitrites, and 6-keto-PGF1α, both over the short and the long term. Serum glucagon levels rose after long-term inhibition. In conclusion, the specific role played by TNF-α in the development of the hyperdynamic state of portal hypertension appears to be mainly mediated through an increased release of nitric oxide and prostacyclin. Maintenance of the splanchnic hyperemia after long-term TNF-α inhibition could be due to a compensatory release of glucagon.
Regional effects of cholecystokinin octapeptide on colonic phasic and tonic motility in healthy humans
Authors: Coffin Benoit , Fossati Sophie , Flourié Bernard , Lémann Marc , Jouet Pauline , Franchisseur Claire , Jian Raymond , Rambaud Jean-Claude
Published: December 2017

The aim of this study was to assess in nine healthy subjects the effects of CCK octapeptide (CCK-8) on colonic tonic activity, measured by a barostat, and phasic activity, measured by manometry. On 2 consecutive days, recordings were performed in the unprepared proximal and distal colons during intravenous infusion of saline and CCK-8 at 5, 20, and 40 ng ⋅ kg−1⋅ h−1. In the proximal colon CCK-8 induced, at the 20 and 40 ng ⋅ kg−1⋅ h−1doses, a tonic relaxation with an increase in barostat bag volume to 156 ± 25 and 157 ± 19% of basal ( P < 0.01) and a decrease in phasic activity to 72 ± 7 and 76 ± 7% of basal ( P < 0.01). In the distal colon, CCK-8 induced, at the 20 and 40 ng ⋅ kg−1⋅ h−1doses, a tonic relaxation (increase in intrabag volume to 133 ± 12 and 149 ± 15%, respectively; P< 0.01), whereas phasic activity increased (128 ± 8 and 132 ± 6%, respectively; P < 0.01). Effects of CCK-8 on tonic and phasic activities are different according to the colonic segment. Because meals induce colonic tonic contraction, our results suggest that CCK, as a hormone, is not an important mediator of the response of the colon to feeding in humans.
III. A molecular prelude to intestinal inflammation
Authors: Miller Mark J. S. , Sandoval Manuel
Published: December 2017

Nitric oxide (NO) synthesis is markedly augmented in states of inflammation, largely due to the expression of inducible nitric oxide synthase (iNOS). Although NO has anti-inflammatory consequences under basal conditions, it remains enigmatic as to why NO displays proinflammatory characteristics in chronic inflammation. Either the anti-inflammatory actions are weak and of little consequence or, alternatively, other factors influence the role of NO in chronic inflammation. We propose that the answer to this enigma lies in the conversion of NO to other higher oxides of nitrogen (NO2, nitrogen dioxide; N2O3, dinitrogen trioxide; and ONOO−, peroxynitrite). Emerging therapeutic strategies may be independent of NO synthesis; e.g., antioxidants have no direct interaction with NO but attenuate the levels and activity of higher nitrogen oxides. Thus, whereas iNOS may be a marker for the proinflammatory actions of NO, the species that mediate tissue injury/dysfunction in inflammation are likely to be nitrogen oxides other than NO.
Effects of IBMX on norepinephrine-induced vasoconstriction in small mesenteric arteries
Authors: Taylor Mark S. , Gao Hong , Gardner Jason D. , Benoit Joseph N.
Published: December 2017

The present study assesses the effects of the phosphodiesterase inhibitor IBMX on norepinephrine (NE)-induced constriction of small mesenteric arteries. Arteries (∼150 μm) were dissected from rats and mounted on a wire myograph for isometric force measurement. NE concentration effect curves were generated after exposure to 500 μM IBMX for 60 min. IBMX significantly reduced NE-induced tension development. Studies were also conducted following sarcoplasmic reticulum (SR) depletion (ryanodine, 10 μM) or L-type Ca2+channel blockade [(+)-BAY K 8644, 10 μM] in the presence and absence of IBMX. Both SR depletion and L-channel blockade reduced NE-induced tension generation, consistent with incomplete Ca2+mobilization. IBMX significantly attenuated NE responses in ryanodine and (+)-BAY K 8644-treated vessels. Finally, treatment of NE-stimulated vessels with IBMX (500 μM) caused a reduction in vascular tension that was greater than the concomitant reduction in cytosolic Ca2+concentration ([Ca2+]i), indicating that a portion of the IBMX-mediated relaxation is Ca2+-independent. These data suggest that IBMX attenuation of NE responsiveness not only involves a reduction in [Ca2+]ibut also a significant decrease in Ca2+sensitivity.
Normal human colonic subepithelial myofibroblasts enhance epithelial migration (restitution) via TGF-β3
Authors: McKaig Brian C. , Makh Shavcharn S. , Hawkey Christopher J. , Podolsky Daniel K. , Mahida Yashwant R.
Published: December 2017

-After injury and loss of epithelial cells, intestinal barrier function is reestablished by migration of viable epithelial cells from the wound edge (restitution). Myofibroblasts are located close to the basal surface of epithelial cells. This study aimed to investigate the role of human colonic subepithelial myofibroblasts in epithelial restitution. Primary cultures of subepithelial myofibroblasts were established. Monolayers of the epithelial cell lines IEC-6 and T84 were “wounded” in a standard manner to create an in vitro model of restitution. Migration of epithelial cells across the wound edge was assessed following culture in myofibroblast-conditioned medium. Myofibroblast expression of transforming growth factor (TGF)-β isoforms was examined using RT-PCR, and TGF-β isoform bioactivity was assessed using Mv 1 Lu bioassay. Myofibroblast-conditioned medium, via a TGF-β-dependent pathway, significantly enhanced migration of epithelial cells across the wound edge and significantly inhibited cell proliferation in wounded monolayers. Messenger RNA for TGF-β1, -β2, and -β3 was detected in the myofibroblasts, and Mv 1 Lu bioassay showed the presence of predominantly bioactive TGF-β3. This study shows that human colonic subepithelial myofibroblasts secrete predominantly bioactive TGF-β3 and enhance restitution in wounded epithelial monolayers via a TGF-β-dependent pathway.
Regulation of α1-antitrypsin gene expression in human intestinal epithelial cell line Caco-2 by HNF-1α and HNF-4
Authors: Hu Chaobin , Perlmutter David H.
Published: December 2017

There is still relatively limited information about mechanisms of gene expression in enterocytes and mechanisms by which gene expression is regulated during enterocyte differentiation. Using the human intestinal epithelial cell line Caco-2, which spontaneously differentiates from a cryptlike to a villouslike enterocyte, we have previously shown that there is a marked increase in transcription of the well-characterized α1-antitrypsin (α1-AT) gene during enterocyte differentiation. In this study we examined the possibility of identifying the cis-acting elements and trans-acting DNA-binding proteins responsible for expression of the α1-AT gene in Caco-2 cells during differentiation. Footprint analysis and electrophoretic mobility shift assays showed that hepatocyte nuclear factor-1α (HNF-1α), HNF-1β, and HNF-4 from nuclear extracts of Caco-2 cells specifically bound to two regions in the proximal promoter of the α1-AT gene. Cotransfection studies showed that HNF-1α and HNF-4 had a synergistic effect on α1-AT gene expression. RNA blot analysis showed that HNF-1α and HNF-4 mRNA levels and electrophoretic mobility shift assays showed that HNF-1α binding activity increase coordinately with α1-AT mRNA levels during differentiation of Caco-2 cells. Finally, overexpression of antisense ribozymes for HNF-1α in Caco-2 cells resulted in a selective decrease in endogenous α1-AT gene expression. Together, these results provide evidence that HNF-1α and HNF-4 play a role in the mechanism by which the α1-AT gene is upregulated during enterocyte differentiation in the model Caco-2 cell system.
Splanchnic tissues undergo hypoxic stress during whole body hyperthermia
Authors: Hall David M. , Baumgardner Kirk R. , Oberley Terry D. , Gisolfi Carl V.
Published: December 2017

Exposure of conscious animals to environmental heat stress increases portal venous radical content. The nature of the observed heat stress-inducible radical molecules suggests that hyperthermia produces cellular hypoxic stress in liver and intestine. To investigate this hypothesis, conscious rats bearing in-dwelling portal venous and femoral artery catheters were exposed to normothermic or hyperthermic conditions. Blood gas levels were monitored during heat stress and for 24 h following heat exposure. Hyperthermia significantly increased arterial O2saturation, splanchnic arterial-venous O2difference, and venous[Formula: see text], while decreasing venous O2saturation and venous pH. One hour after heat exposure, liver glycogen levels were decreased ∼20%. Two hours after heat exposure, the splanchnic arterial-venous O2difference remained elevated in heat-stressed animals despite normal Tc. A second group of rats was exposed to similar conditions while receiving intra-arterial injections of the hypoxic cell marker [3H]misonidazole. Liver and intestine were biopsied, and [3H]misonidazole content was quantified. Heat stress increased tissue [3H]misonidazole retention 80% in the liver and 29% in the small intestine. Cellular [3H]misonidazole levels were significantly elevated in intestinal epithelial cells and liver zone 2 and 3 hepatocytes and Kupffer cells. This effect was most prominent in the proximal small intestine and small liver lobi. These data provide evidence that hyperthermia produces cellular hypoxia and metabolic stress in splanchnic tissues and suggest that cellular metabolic stress may contribute to radical generation during heat stress.
Pancreatic function in CCK-deficient mice: adaptation to dietary protein does not require CCK
Authors: Lacourse Karen A. , Swanberg Lisa J. , Gillespie Patrick J. , Rehfeld Jens F. , Saunders Thomas L. , Samuelson Linda C.
Published: December 2017

A CCK-deficient mouse mutant generated by gene targeting in embryonic stem cells was analyzed to determine the importance of CCK for growth and function of the exocrine pancreas and for pancreatic adaptation to dietary changes. RIAs confirmed the absence of CCK in mutant mice and demonstrated that tissue concentrations of the related peptide gastrin were normal. CCK-deficient mice are viable and fertile and exhibit normal body weight. Pancreas weight and cellular morphology appeared normal, although pancreatic amylase content was elevated in CCK-deficient mice. We found that a high-protein diet increased pancreatic weight, protein, DNA, and chymotrypsinogen content similarly in CCK-deficient and wild-type mice. This result demonstrates that CCK is not required for protein-induced pancreatic hypertrophy and increased proteolytic enzyme content. This is a novel finding, since CCK has been considered the primary mediator of dietary protein-induced changes in the pancreas. Altered somatostatin concentrations in brain and duodenum of CCK-deficient mice suggest that other regulatory pathways are modified to compensate for the CCK deficiency.
ATP is a mediator of the fast inhibitory junction potential in human jejunal circular smooth muscle
Authors: Xue L. , Farrugia G. , Sarr M. G. , Szurszewski J. H.
Published: December 2017

The neurotransmitter(s) that generates the fast component of the inhibitory junction potential (IJP-F) in human jejunal circular smooth muscle is not known. The aim of this study was to determine the role of ATP and purinergic receptors in the generation of the IJP-F in human jejunal circular smooth muscle strips. The P2-receptor antagonist suramin (100 μM) reduced the IJP-F by 28%. Apamin (1 μM) reduced the IJP-F by 25%. Desensitization of muscle strips with the putative P2x-receptor agonist α,β-methylene ATP (α,β-MeATP, 100 μM) decreased the IJP-F by 44%, and desensitization with the putative P2y-receptor agonist adenosine 5′- O-2-thiodiphosphate (ADPβS) completely abolished the IJP-F. Desensitization with the putative P2y-receptor agonist 2-methylthioATP had no effect on the IJP-F. Exogenous ATP evoked a hyperpolarization with a time course that matched the IJP-F. The ATP-evoked hyperpolarization was reduced by apamin and suramin, reduced by desensitization with α,β-MeATP (69% decrease), and abolished by desensitization with ADPβS. These data suggest that the IJP-F in human jejunal circular smooth muscle is mediated in part by ATP through an ADPβS-sensitive P2receptor.
NO releases bombesin-like immunoreactivity from enteric synaptosomes by cross-activation of protein kinase A
Authors: Kurjak M. , Fritsch R. , Saur D. , Schusdziarra V. , Allescher H. D.
Published: December 2017

The effect of nitric oxide (NO) on the release of bombesin-like immunoreactivity (BLI) was examined in synaptosomes of rat small intestine. The NO donor S-nitroso- N-acetylpenicillamine (SNAP; 10−7to 10−4M) significantly stimulated BLI release. In the presence of the NO scavenger oxyhemoglobin (10−3M) or the guanylate cyclase inhibitor ODQ (10−5M), SNAP-induced BLI release was antagonized. In addition, SNAP increased the synaptosomal cGMP content and elevation of cGMP levels by zaprinast (3 × 10−5M), an inhibitor of the cGMP-specific phosphodiesterase (PDE) type 5, and increased basal and SNAP-induced BLI release. NO-induced BLI release was blocked by Rp-adenosine 3′,5′-cyclic monophosphorothioate (3 × 10−5M and 10−4M), an inhibitor of the cAMP-dependent protein kinase A, whereas KT-5823 (3 × 10−6M) and Rp-8-(4-chlorophenylthio)-cGMP (5 × 10−5M), inhibitors of the cGMP-dependent protein kinase G, had no effect. Because cGMP inhibits the cAMP-specific PDE3, thereby increasing cAMP levels, the role of PDE3 was investigated. Trequinsin (10−8M), a specific blocker of PDE3, stimulated basal BLI release but had no additive effect on NO-induced release, suggesting a similar mechanism of action. These data demonstrate that because of a cross-activation of cAMP-dependent protein kinase A by endogenous cGMP BLI can be released by NO from enteric synaptosomes.