bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative contributions of “pressure pump” and “peristaltic pump” to gastric emptying
Authors: Indireshkumar K. , Brasseur James G. , Faas Henryk , Hebbard Geoffrey S. , Kunz Patrik , Dent John , Feinle Christine , Li Meijng , Boesiger Peter , Fried Michael , Schwizer Werner
Published: December 2017

The relative contributions to gastric emptying from common cavity antroduodenal pressure difference (“pressure pump”) vs. propagating high-pressure waves in the distal antrum (“peristaltic pump”) were analyzed in humans by high-resolution manometry concurrently with time-resolved three-dimensional magnetic resonance imaging during intraduodenal nutrient infusion at 2 kcal/min. Gastric volume, space-time pressure, and contraction wave histories in the antropyloroduodenal region were measured in seven healthy subjects. The subjects fell into two distinct groups with an order of magnitude difference in levels of antral pressure activity. However, there was no significant difference in average rate of gastric emptying between the two groups. Antral pressure history was separated into “propagating high-pressure events” (HPE), “nonpropagating HPEs,” and “quiescent periods.” Quiescent periods dominated, and average pressure during quiescent periods remained unchanged with decreasing gastric volume, suggesting that common cavity pressure levels were maintained by increasing wall muscle tone with decreasing volume. When propagating HPEs moved to within 2–3 cm of the pylorus, pyloric resistance was found statistically to increase with decreasing distance between peristaltic waves and the pylorus. We conclude that transpyloric flow tends to be blocked when antral contraction waves are within a “zone of influence” proximal to the pylorus, suggesting physiological coordination between pyloric and antral contractile activity. We further conclude that gastric emptying of nutrient liquids is primarily through the “pressure pump” mechanism controlled by pyloric opening during periods of relative quiescence in antral contractile wave activity.
Mode of action of ANG II on ion transport in guinea pig distal colon
Authors: Hosoda Yutaka , Winarto Adi , Iwanaga Toshihiko , Kuwahara Atsukazu
Published: December 2017

The effect of ANG II on mucosal ion transport and localization of ANG type 1 receptor (AT1R) in the guinea pig distal colon was investigated. Submucosal/mucosal segments were mounted in Ussing flux chambers, and short-circuit current ( Isc) was measured as an index of ion transport. Serosal addition of ANG II produced a concentration-dependent (10−9–10−5M) increase in Isc. The maximal response was observed at 10−6M; the increase in Iscwas 164.4 ± 11.8 μA/cm2. The ANG II (10−6M)-evoked response was mainly due to Cl−secretion. Tetrodotoxin, atropine, the neurokinin type 1 receptor antagonist FK-888, and piroxicam significantly reduced the ANG II (10−6M)-evoked response to 28, 45, 58, and 16% of control, respectively. Pretreatment with prostaglandin E2(10−5M) resulted in a threefold increase in the ANG II-evoked response. The AT1R antagonist FR-130739 completely blocked ANG II (10−6M)-evoked responses, whereas the ANG type 2 receptor antagonist PD-123319 had no effect. Localization of AT1R was determined by immunohistochemistry. In the immunohistochemical study, AT1R-immunopositive cells were distributed clearly in enteric nerves and moderately in surface epithelial cells. These results suggest that ANG II-evoked electrogenic Cl−secretion may involve submucosal cholinergic and tachykinergic neurons and prostanoid synthesis pathways through AT1R on the submucosal plexus and surface epithelial cells in guinea pig distal colon.
Aging alters gastric mucosal responses to epidermal growth factor and transforming growth factor-α
Authors: Turner Jerrold R. , Liu Lei , Fligiel Suzanne E. G. , Jaszewski Richard , Majumdar Adhip P. N.
Published: December 2017

Administration of pharmacological doses of epidermal growth factor (EGF) or transforming growth factor-α (TGF-α) in young rats stimulates gastric mucosal proliferation, but, in aged rats, the same treatment inhibits proliferation. This may be due to enhanced ligand-induced internalization of EGF receptor (EGFR). In support of this, we demonstrated that although a single injection of EGF (10 μg/kg) or TGF-α (5 μg/kg) in young (4–6 mo old) rats greatly increased membrane-associated EGFR tyrosine kinase activity, the same treatment slightly inhibited the enzyme activity in aged (24 mo old) rats. This treatment also produced a greater abundance of punctate cytoplasmic EGFR staining in gastric epithelium of aged rats, consistent with EGFR internalization. In vitro analyses demonstrated that exposure of isolated gastric mucosal cells from aged but not young rats to 100 pM TGF-α resulted in marked increases in intracellular EGFR tyrosine kinase activity and that induction of EGFR tyrosine kinase activity in mucosal membranes from aged rats occurred at doses 1,000-fold less than those required in young rats. Our data suggest that aging enhances sensitivity of the gastric mucosa to EGFR ligands. This may partly explain EGFR-mediated inhibition of gastric mucosal proliferation in aged rats.
Bile salts induce or blunt cell proliferation in Barrett's esophagus in an acid-dependent fashion
Authors: Kaur Baljeet S. , Ouatu-Lascar Rodica , Omary M. Bishr , Triadafilopoulos George
Published: December 2017

Barrett's esophagus (BE) results from acid and bile reflux and predisposes to cancer. We investigated the effect of bile salts, with or without acid, on cell proliferation in BE and assessed mechanism(s) involved. To mimic physiological conditions, biopsies of esophagus, BE, and duodenum were exposed to a bile salt mixture, either continuously or as a 1-h pulse, and were compared with control media without bile salts (pH 7.4) for ≤24 h. Similar experiments were also performed with acidified media (pH 3.5) combined with the bile salt mixture as a 1-h pulse. Cell proliferation was assessed by a [3H]thymidine incorporation assay with or without bisindolylmaleimide (BIM), a selective protein kinase C inhibitor. Bile salt pulses enhanced cell proliferation in BE without affecting cell proliferation in esophageal or duodenal epithelia. In the presence of BIM, there was complete obliteration of the bile salt-induced BE hyperproliferation. In contrast, 1-h pulses of bile salts in combination with acid significantly inhibited proliferation in BE but had no effect on esophagus or duodenum. We conclude that in BE explants, brief exposure to bile salts, in the absence of acid, increases proliferation, whereas exposure to a combination of bile salts and acid together inhibits proliferation.
Accessibility of glycolipid and oligosaccharide epitopes on rabbit villus and follicle-associated epithelium
Authors: Mantis Nicholas J. , Frey Andreas , Neutra Marian R.
Published: December 2017

The initial step in many mucosal infections is pathogen attachment to glycoconjugates on the apical surfaces of intestinal epithelial cells. We examined the ability of virus-sized (120-nm) and bacterium-sized (1-μm) particles to adhere to specific glycolipids and protein-linked oligosaccharides on the apical surfaces of rabbit Peyer's patch villus enterocytes, follicle-associated enterocytes, and M cells. Particles coated with the B subunit of cholera toxin, which binds the ubiquitous glycolipid GM1, were unable to adhere to enterocytes or M cells. This confirms that both the filamentous brush border glycocalyx on enterocytes and the thin glycoprotein coat on M cells can function as size-selective barriers. Oligosaccharides containing terminal β(1,4)-linked galactose were accessible to soluble lectin Ricinus communistype I on all epithelial cells but were not accessible to lectin immobilized on beads. Oligosaccharides containing α(2,3)-linked sialic acid were recognized on all epithelial cells by soluble Maackia amurensis lectin II (Mal II). Mal II coated 120-nm (but not 1-μm) particles adhered to follicle-associated enterocytes and M cells but not to villus enterocytes. The differences in receptor availability observed may explain in part the selective attachment of viruses and bacteria to specific cell types in the intestinal mucosa.
Manometric changes during retrograde biliary infusion in mice
Authors: Wiener Stephen M. , Hoyt Robert F. , Deleonardis John R. , Clevenger Randall R. , Jeffries Kenneth R. , Nagashima Kunio , Mandel Myrna , Owens Jennie , Eckhaus Michael , Lutz Robert J. , Safer Brian
Published: December 2017

The manometric, ultrastructural, radiographic, and physiological consequences of retrograde biliary infusion were determined in normostatic and cholestatic mice. Intraluminal biliary pressure changed as a function of infusion volume, rate, and viscosity. Higher rates of constant infusion resulted in higher peak intraluminal biliary pressures. The pattern of pressure changes observed was consistent with biliary ductular and/or canalicular filling followed by leakage at a threshold pressure. Retrograde infusion with significant elevations in pressure led to paracellular leakage of lanthanum chloride, radiopaque dye, and [14C]sucrose with rapid systemic redistribution via sinusoidal and subsequent hepatic venous drainage. Chronic extrahepatic bile duct obstruction resulted in significantly smaller peak intrabiliary pressures and lower levels of paracellular leakage. These findings indicate that under both normostatic and cholestatic conditions elevated intrabiliary volumes/pressures result in an acute pressure-dependent physical opening of tight junctions, permitting the movement of infusate from the intrabiliary space into the subepithelial tissue compartment. Control of intraluminal pressure may potentially permit the selective delivery of macromolecules >18–20Å in diameter to specific histological compartments.
The contractile action of platelet-activating factor on gallbladder smooth muscle
Authors: Parkman Henry P. , James Arlene N. , Ryan James P.
Published: December 2017

Platelet-activating factor (PAF) may be a mediator of some sequelae of cholecystitis, a disorder with gallbladder motor dysfunction. The aims of this study were to determine the effect and mechanism of PAF on gallbladder muscle. Exogenous administration of PAF-16 or PAF-18 caused dose-dependent contractions of gallbladder muscle strips in vitro with threshold doses of 1 ng/ml and 10 ng/ml, respectively. The PAF-induced contractions were not significantly reduced by TTX, atropine, or hexamethonium but were significantly inhibited with the PAF receptor antagonists ginkolide B and CV-3988. The PAF-induced contraction was reduced by indomethacin. Preventing influx of extracellular calcium with a calcium-free solution nearly abolished the PAF contractile response. Nifedipine inhibited the PAF contractile response, whereas ryanodine had no effect. Pertussis toxin reduced the PAF contractile response. In conclusion, PAF causes gallbladder contraction through specific PAF receptors on gallbladder muscle. These PAF receptors appear to be linked to a prostaglandin-mediated mechanism and to pertussis toxin-sensitive G proteins. The contractile response is largely mediated through the utilization of extracellular calcium influx through voltage-dependent calcium channels.
Rotavirus infection impairs intestinal brush-border membrane Na+-solute cotransport activities in young rabbits
Authors: Halaihel Nabil , Liévin Vanessa , Alvarado Francisco , Vasseur Monique
Published: December 2017

The mechanism of rotavirus diarrhea was investigated by infecting young, specific pathogen-free, New Zealand rabbits with a lapine rotavirus, strain La/RR510. With 4-wk-old animals, virus shedding into the intestinal lumen peaked at 72 h postinfection (hpi), and a mild, watery diarrhea appeared at 124 hpi. No intestinal lesions were seen up to 144 hpi, indicating that diarrhea does not follow mucosal damage but can precede it, as if cell dysfunction were the cause, not the consequence, of the histological lesions. Kinetic analyses with brush-border membrane vesicles isolated from infected rabbits revealed strong inhibition of both Na+-d-glucose (SGLT1) and Na+-l-leucine symport activities. For both symporters, only maximum velocity decreased with time. The density of phlorizin-binding sites and SGLT1 protein antigen in the membrane remained unaffected, indicating that the virus effect on this symporter is direct. Because SGLT1 supports water reabsorption under physiological conditions, the mechanism of rotavirus diarrhea may involve a generalized inhibition of Na+-solute symport systems, hence, of water reabsorption. Massive water loss through the intestine may eventually overwhelm the capacity of the organ for water reabsorption, thereby helping the diarrhea to get established.
Molecular Physiology and Pathophysiology of Tight Junctions III. Tight junction regulation by intracellular messengers: differences in response within and between epithelia
Authors: Karczewski Jurgen , Groot Jack
Published: December 2017

Tight junction permeability differs with the type of permeants, their size, and their charge. Selective changes in permeability do occur, and they illustrate the diversity in functional reactions of tight junctions. This suggests that special structures in the tight junctions are involved. More and more structural components of the tight junctions are becoming known. The divergence in behavior of native tissue and filter-grown epithelial monolayers with respect to the effects of intracellular messengers offers the possibility to relate structure and function. In addition to the tools for conventional permeability studies, probes have become available to detect changes in activation of intracellular effector proteins such as the protein kinase C isotypes, and with in situ imaging techniques the way is open for a functional approach in the study of tight junctions.
Effects of γ-aminobutyric acid on secretagogue-induced exocrine secretion of isolated, perfused rat pancreas
Authors: Park Hyung Seo , Park Hyoung Jin
Published: December 2017

Because GABA and its related enzymes have been determined in β-cells of pancreas islets, effects of GABA on pancreatic exocrine secretion were investigated in the isolated, perfused rat pancreas. GABA, given intra-arterially at concentrations of 3, 10, 30, and 100 μM, did not exert any influence on spontaneous or secretin (12 pM)-induced pancreatic exocrine secretion. However, GABA further elevated CCK (10 pM)-, gastrin-releasing peptide (100 pM)-, or electrical field stimulation-induced pancreatic secretions of fluid and amylase dose dependently. The GABA (30 μM)-enhanced CCK-induced pancreatic secretions were completely blocked by bicuculline (10 μM), a GABAA receptor antagonist, but were not affected by saclofen (10 μM), a GABAB receptor antagonist. The enhancing effects of GABA (30 μM) on CCK-induced pancreatic secretions were not changed by tetrodotoxin (1 μM) but were partially reduced by cyclo-(7-aminoheptanonyl-Phe-d-Trp-Lys-Thr[BZL]) (10 nM), a somatostatin antagonist. In conclusion, GABA enhances pancreatic exocrine secretion induced by secretagogues, which predominantly induce enzyme secretion, via GABAA receptors in the rat pancreas. The enhancing effect of GABA is partially mediated by inhibition of islet somatostatin release.
Rectal sensitivity assessed by a reflexologic technique: further evidence for two types of mechanoreceptors
Authors: Sabate Jean-Marc , Coffin Benoit , Jian Raymond , Le Bars Daniel , Bouhassira Didier
Published: December 2017

We previously showed that slow-ramp rectal distensions induce graded inhibitions of the somatic nociceptive RIII reflex recorded from the lower limb, which correlated with both distension volume and visceral sensation. In contrast, rapid phasic rectal distensions induced facilitatory or biphasic effects (i.e., facilitations followed by inhibitions) depending on the level of distension. To examine the role of mucosal and serosal rectal mechanoreceptors in these viscerosomatic interactions, we analyzed, in six healthy volunteers, the effects of both types of rectal distension on the RIII reflex after topical application of lidocaine or placebo administered in a double-blind and crossover fashion. Inhibitions of the RIII reflex induced by both slow-ramp and rapid distensions were strongly reduced after administration of lidocaine but not after placebo. In contrast, facilitations of the RIII reflex observed during the initial phase of rapid distensions were not modified after lidocaine or placebo applications. These results suggest that inhibitions, but not facilitations, of the nociceptive RIII reflex triggered by rectal distensions depend preferentially on the activation of superficial mucosal receptors. This reflexologic technique might thus represent an interesting tool for studying the role of the different rectal mechanoreceptors involved in visceral sensations.
Evaluation of multiple-point measurement of sphincter of Oddi motility in the Australian brush-tailed possum
Authors: Craig A. G. , Omari T. I. , Saccone G. T. P. , Toouli J. , Dent J.
Published: December 2017

Manometric assembly diameter is a major limitation on the number of perfused manometric recording points for recordings from the sphincter of Oddi (SO). We evaluated novel polyimide manometric assemblies whereby four recording channels were incorporated in an overall assembly diameter of 0.8 mm. Over the very low range of perfusion rates tested (0.005–0.04 ml/min), the assemblies had pressure offsets attributable to water perfusion from 2 to 23 mmHg and pressure rise rates from 20 to 163 mmHg/s. In six anesthetized Australian brush-tailed possums, manometric recordings from the SO showed a significant reduction in the recorded peak amplitude of pressure waves with perfusion rates below 0.02 ml/min. The pressure profile of the sphincter was found to be asymmetric, and phasic wave propagation patterns were complex (antegrade 35.6%, “mixed” 64.4%). In conclusion, accurate multipoint SO manometry in the possum can be performed with micromanometric assemblies at very low perfusion rates to give a more complete understanding of SO mechanics. These methods are also potentially applicable to perfusion manometry in other small laboratory animals such as mice.
Dietary iron induces rapid changes in rat intestinal divalent metal transporter expression
Authors: Yeh Kwo-Yih , Yeh Mary , Watkins J. Abra , Rodriguez-Paris Juan , Glass Jonathan
Published: December 2017

The divalent metal transporter (DMT1, also known as NRAMP2 or DCT1) is the likely target for regulation of intestinal iron absorption by iron stores. We investigated changes in intestinal DMT1 expression after a bolus of dietary iron in iron-deficient Belgrade rats homozygous for the DMT1 G185R mutation (b/b) and phenotypically normal heterozygous littermates (+/b). Immunofluorescent staining with anti-DMT1 antisera showed that DMT1 was located in the brush-border membrane. Duodenal DMT1 mRNA and protein levels were six- and twofold higher, respectively, in b/b rats than in +/b rats. At 1.5 h after dietary iron intake in +/b and b/b rats, DMT1 was internalized into cytoplasmic vesicles. At 1.5 and 3 h after iron intake in +/b and b/b rats, there was a rapid decrease of DMT1 mRNA and a transient increase of DMT1 protein. The decrease of DMT1 mRNA was specific, because ferritin mRNA was unchanged. After iron intake, an increase in ferritin protein and decrease in iron-regulatory protein binding activity occurred, reflecting elevated intracellular iron pools. Thus intestinal DMT1 rapidly responds to dietary iron in both +/b and b/b rats. The internalization of DMT1 may be an acute regulatory mechanism to limit iron uptake. In addition, the results suggest that in the Belgrade rat DMT1 with the G185R mutation is not an absolute block to iron.
Activation of Na+- and Ca2+-dependent Mg2+extrusion by α1- and β-adrenergic agonists in rat liver cells
Authors: Fagan Theresa E. , Romani Andrea
Published: December 2017

The administration of selective α1(phenylephrine)-, β (isoproterenol)-, or mixed (epinephrine) adrenergic agonists induces a marked Mg2+extrusion from perfused rat livers. In the absence of extracellular Ca2+, phenylephrine does not induce a detectable Mg2+extrusion, isoproterenol-induced Mg2+mobilization is unaffected, and epinephrine induces a net Mg2+extrusion that is lower than in the presence of extracellular Ca2+and quantitatively similar to that elicited by isoproterenol. In the absence of extracellular Na+, no Mg2+is extruded from the liver irrespective of the agonist used. Similar results are observed in perfused livers stimulated by glucagon or 8-chloroadenosine 3′,5′-cyclic monophosphate. In the absence of extracellular Na+or Ca2+, adrenergic-induced glucose extrusion from the liver is also markedly decreased. Together, these results indicate that liver cells extrude Mg2+primarily via a Na+-dependent mechanism. This extrusion pathway can be activated by the increase in cellular cAMP that follows the stimulation by glucagon or a specific β-adrenergic receptor agonist or, alternatively, by the changes in cellular Ca2+induced by the stimulation of the α1-adrenoceptor. In addition, the stimulation of the α1-adrenoceptor appears to activate an auxiliary Ca2+-dependent Mg2+extrusion pathway. Finally, our data suggest that experimental conditions that affect Mg2+mobilization also interfere with glucose extrusion from liver cells.
Effect of splanchnectomy on jejunal motility and Fos expression in brain stem after intestinal anaphylaxis in rat
Authors: Scott R. Brent , Tan Daimen T. M. , Sharkey Keith A.
Published: December 2017

This study was to determine whether alterations in jejunal motility observed after antigen challenge of sensitized rats occurred after extirpation of the celiac-superior mesenteric ganglia. Hooded-Lister rats were prepared with an intact or extirpated celiac-superior mesenteric ganglion, an isolated Thiry-Vella loop of ileum for instillation of antigen, and jejunal electrodes for myoelectric recording. Animals were sensitized by injection of 10 μg egg albumin (EA, ip), and specific anti-EA IgE titers were determined to be >1:64. In both control and splanchnectomized rats, normal fasting migrating myoelectric complexes (MMC) were observed before challenge with EA. MMCs were disrupted, and diarrhea was observed immediately after EA challenge of control but not splanchnectomized animals. Brain stems were removed and processed for Fos immunoreactivity. The absence of perivascular neuropeptide Y immunoreactivity in the submucosa was used to confirm the success of splanchnectomy. The number of Fos-immunoreactive neuronal nuclei was significantly reduced in the brain stem after splanchnectomy. Thus the mesenteric sympathetic ganglia are an integral part of the extramural neuronal pathways required for altered motility in this model of intestinal anaphylaxis.
Tumor-influenced amino acid transport activities in zonal-enriched hepatocyte populations
Authors: Easson Alexandra M. , Pawlik Timothy M. , Fischer Craig P. , Conroy Jennifer L. , Sgroi Dennis , Souba Wiley W. , Bode Barrie P.
Published: December 2017

Cancer influences hepatic amino acid metabolism in the host. To further investigate this relationship, the effects of an implanted fibrosarcoma on specific amino acid transport activities were measured in periportal (PP)- and perivenous (PV)-enriched rat hepatocyte populations. Na+-dependent glutamate transport rates were eightfold higher in PV than in PP preparations but were relatively unaffected during tumor growth. System N-mediated glutamine uptake was 75% higher in PV than in PP preparations and was stimulated up to twofold in both regions by tumor burdens of 9 ± 4% of carcass weight compared with hepatocytes from pair-fed control animals. Excessive tumor burdens (26 ± 7%) resulted in hypophagia, loss of PV-enriched system N activities, and reduced transporter stimulation. Conversely, saturable arginine uptake was enhanced fourfold in PP preparations and was induced twofold only after excessive tumor burden. These data suggest that hepatic amino acid transporters are differentially influenced by cancer in a spatial and temporal manner, and they represent the first report of reciprocal zonal enrichment of system N and saturable arginine uptake in the mammalian liver.
Hepatic microvascular responses to ischemia-reperfusion in low-density lipoprotein receptor knockout mice
Authors: Mori Naoharu , Horie Yoshinori , Nimura Yuji , Wolf Robert , Granger D. Neil
Published: December 2017

The overall objective of this study was to determine whether genetically induced hypercholesterolemia alters the inflammatory and microvascular responses of mouse liver to ischemia-reperfusion (I/R). The accumulation of rhodamine 6G-labeled leukocytes and the number of nonperfused sinusoids (NPS) were monitored (by intravital microscopy) in the liver of wild-type (WT) and low-density lipoprotein receptor-deficient (LDLr−/−) mice for 1 h after a 30-min period of normothermic ischemia. Plasma alanine transaminase (ALT) levels were used to monitor hepatocellular injury. Microvascular leukostasis as well as increases in NPS and plasma ALT were observed at 60 min after hepatic I/R in both WT and in LDLr−/− mice; however, these responses were greatly exaggerated in LDLr−/− mice. Pretreatment of LDLr−/− mice with gadolinium chloride, which reduces Kupffer cell function, attenuated the hepatic leukostasis, NPS, and hepatocellular injury elicited by I/R. Similar protection against I/R was observed in LDLr−/− mice pretreated with antibodies directed against tumor necrosis factor-α, intercellular adhesion molecule-1 (ICAM-1), or P-selectin. These findings indicate that chronic hypercholesterolemia predisposes the hepatic microvasculature to the deleterious effects of I/R. Kupffer cell activation and the leukocyte adhesion receptors ICAM-1 and P-selectin appear to contribute to the exaggerated inflammatory responses observed in the postischemic liver of LDLr−/− mice.
Simple epithelial keratins are dispensable for cytoprotection in two pancreatitis models
Authors: Toivola Diana M. , Baribault Hélène , Magin Thomas , Michie Sara A. , Omary M. Bishr
Published: December 2017

Pancreatic acinar cells express keratins 8 and 18 (K8/18), which form cytoplasmic filament (CF) and apicolateral filament (ALF) pools. Hepatocyte K8/18 CF provide important protection from environmental stresses, but disruption of acinar cell CF has no significant impact. We asked whether acinar cell ALF are important in providing cytoprotective roles by studying keratin filaments in pancreata of K8- and K18-null mice. K8-null pancreas lacks both keratin pools, but K18-null pancreas lacks only CF. Mouse but not human acinar cells also express apicolateral keratin 19 (K19), which explains the presence of apicolateral keratins in K18-null pancreas. K8- and K18-null pancreata are histologically normal, and their acini respond similarly to stimulated secretion, although K8-null acini viability is reduced. Absence of total filaments (K8-null) or CF (K18-null) does not increase susceptibility to pancreatitis induced by caerulein or a choline-deficient diet. In normal and K18-null acini, K19 is upregulated after caerulein injury and, unexpectedly, forms CF. As in hepatocytes, acinar injury is also associated with keratin hyperphosphorylation. Hence, K19 forms ALF in mouse acinar cells and helps define two distinct ALF and CF pools. On injury, K19 forms CF that revert to ALF after healing. Acinar keratins appear to be dispensable for cytoprotection, in contrast to hepatocyte keratins, despite similar hyperphosphorylation patterns after injury.
Intestinal aminooligopeptidase in diabetic BioBreed rat: altered posttranslational processing and trafficking
Authors: Najjar Sonia M. , Broyart Jean-Pierre , Hampp Lydia T. , Gray Gary M.
Published: December 2017

The structure of aminooligopeptidase (AOP), an intestinal brush-border digestive hydrolase, is abnormal in human diabetes and in the congenitally diabetic BioBreed Wistar (BBd) rat. Its assembly in the BBdrat was examined. After normal initial synthesis and assembly of immature AOP precursor (AOPi) with high-mannose N-linked chains in the endoplasmic reticulum (ER), processing of N-linked glycans in Golgi yielded a smaller than normal mature AOP precursor (AOPm) with persistence of some high-mannose N-linked chains. Deglycosylation analyses suggested that the mass difference could be attributed to a lower mass of N-linked with unaltered O-linked glycans in AOPmof the diabetic rat. Intrajejunal pulse-chase experiments revealed that the conversion of AOPito AOPmoccurred at 30 min of chase in normal rats but at 60–90 min in diabetic rats, reflecting delay in ER-to-Golgi transport or a slower processing of high-mannose chains. Once maximal transport to Golgi was achieved, the residence time in Golgi was shortened in diabetes. This altered processing of the precursor accounted for the altered structure of AOP in diabetes.
Relationship between flow rate and NO production in postnatal mesenteric arteries
Authors: Reber Kristina M. , Mager Gennifer M. , Miller Charles E. , Nowicki Philip T.
Published: December 2017

We studied mesenteric arterial arcades from 3- and 35-day-old swine to determine the relationship between perfusate flow rate and release of nitric oxide (NO) into mesenteric effluent. Mesenteric arterial arcades were perfused under controlled-flow conditions with a peristaltic pump using warm oxygenated Krebs buffer. Basal rates of NO production were 43.6 ± 4.2 vs. 12.1 ± 2.5 nmol/min in 3- vs. 35-day-old mesentery during perfusion at in vivo flow rates (9 vs. 20 ml/min, respectively). Rate of NO production was directly related to flow rate over a wide range of flows (5–40 ml/min) in 3- but not 35-day-old mesentery. Both age groups demonstrated a brisk, albeit brief, increase in NO production in response to infusion of NO-dependent vasodilator substance P (10−8M/min). Tyrosine kinase inhibitor herbimycin A andl-arginine analog l-NMMA significantly attenuated flow-induced increase in NO production, and phosphatase inhibitor phenylarsine oxide increased magnitude of flow-induced increase in NO production in 3-day-olds. Removal of extracellular Ca2+and depletion of intracellular Ca2+stores (Ca2+-free Krebs with EGTA plus thapsigargin) had no effect on NO production in either group. Thus, basal rate of NO production is greater in mesenteric arterial arcades from 3- than from 35-day old swine, a direct relationship between flow rate and NO production rate is present in mesentery from 3- but not 35-day-olds, and phosphorylation events are necessary for this interaction to occur.
Esophagitis-related esophageal shortening in opossum is associated with longitudinal muscle hyperresponsiveness
Authors: White Robert J. , Zhang Yong , Morris Gerald P. , Paterson William G.
Published: December 2017

Acute intraluminal acid perfusion induces esophageal shortening in humans and opossums. Lower esophageal sphincter (LES) hypotension and peristaltic dysfunction occur in patients and animal models of reflux esophagitis. This study examined whether similar shortening and motor dysfunction occur in anesthetized opossums after repeated esophageal acid exposure and whether this is associated with longitudinal muscle (LM) hyperresponsiveness. Manometry used before and after 3 consecutive days of 45-min perfusion with 100 mmol/l HCl or normal saline measured esophageal length and motor responses to induced swallows. LM electrical and mechanical responses were assessed using standard isometric tension and intracellular recording techniques. Compared with controls, repeated acid perfusion induced erosive esophagitis and significant esophageal shortening, associated with enhanced LM responses to carbachol, a significantly depolarized resting membrane potential, and abnormal spike patterns. LES resting pressure and swallow-induced peristalsis were unaffected. In this model of reflux esophagitis, marked persistent esophageal shortening and associated LM hyperresponsiveness occur before significant LES or peristaltic dysfunction, suggesting that esophageal shortening is the earliest motor disorder induced by acid injury.
Ontogenic and longitudinal activity of Na+-nucleoside transporters in the human intestine
Authors: Ngo Leock Y. , Patil Shivakumar D. , Unadkat Jashvant D.
Published: December 2017

The objectives of our study were to identify the types of nucleoside transporters present in the human fetal small intestine and to characterize their developmental activity, longitudinal distribution, and transport kinetics compared with those present in the adult intestine. Nucleoside uptake by intestinal brush-border membrane vesicles was measured by an inhibitor-stop rapid filtration technique. Only the purine-specific (N1; hCNT2) and the pyrimidine-specific (N2; hCNT1) Na+-dependent nucleoside transporters were found to be present on the brush-border membranes of the enterocytes along the entire length of the fetal and adult small intestines. The activity of these transporters was higher in the proximal than in the distal small intestine. Both the N1 and N2 transporters found in the fetal intestine shared similar kinetic properties (Michaelis-Menten constant and Na+-nucleoside stoichiometry) to those in the adult intestine. During the period of rapid morphogenesis (11–15 wk gestation), no temporal differences were apparent in the activity of the N1 and N2 transporters in the fetal small intestine. These findings have implications for the absorption of drugs from the amniotic fluid by the fetus after maternal drug administration of nucleoside drugs such as the antivirals zidovudine and didanosine.
GABAB receptors on vagal afferent pathways: peripheral and central inhibition
Authors: Partosoedarso Elita R. , Young Richard L. , Blackshaw L. Ashley
Published: December 2017

To investigate GABAB receptors along vagal afferent pathways, we recorded from vagal afferents, medullary neurons, and vagal efferents in ferrets. Baclofen (7–14 μmol/kg iv) reduced gastric tension receptor and nucleus tractus solitarii neuronal responses to gastric distension but not gastroduodenal mucosal receptor responses to cholecystokinin (CCK). GABAB antagonists CGP-35348 or CGP-62349 reversed effects of baclofen. Vagal efferents showed excitatory and inhibitory responses to distension and CCK. Baclofen (3 nmol icv or 7–14 μmol/kg iv) reduced both distension response types but reduced only inhibitory responses to CCK. CGP-35348 (100 nmol icv or 100 μmol/kg iv) reversed baclofen's effect on distension responses, but inhibitory responses to CCK remained attenuated. They were, however, reversed by CGP-62349 (0.4 nmol icv). In conclusion, GABAB receptors inhibit mechanosensitivity, not chemosensitivity, of vagal afferents peripherally. Mechanosensory input to brain stem neurons is also reduced centrally by GABAB receptors, but excitatory chemosensory input is unaffected. Inhibitory mechano- and chemosensory inputs to brain stem neurons (via inhibitory interneurons) are both reduced, but the pathway taken by chemosensory input involves GABAB receptors that are insensitive to CGP-35348.
Activation of NF-κB by hepatitis B virus X protein through an IκB kinase-independent mechanism
Authors: Purcell Nicole H. , Yu Chenfei , He Daoyao , Xiang Jialing , Paran Nir , DiDonato Joseph A. , Yamaoka Shoji , Shaul Yosef , Lin Anning
Published: December 2017

pX, the hepatitis B virus-encoded transcription coactivator, is involved in viral infection in vivo. pX stimulates the activity of several transcription factors including nuclear factor-κB (NF-κB), but the mechanism of activation is poorly understood. The IκB kinase complex (IKK) mediates activation of NF-κB in response to various extracellular stimuli, including inflammatory cytokines like tumor necrosis factor and interleukin 1, human T cell lymphoma virus 1 Tax protein, and tumor promoters like phorbol esters. It is not known whether IKK also mediates activation of NF-κB by pX. Here we report that IKK was not essential for activation of NF-κB by pX. Expression of pX resulted in the degradation of IκBα in the absence of its phosphorylation at Ser32and Ser36residues. Although pX stimulated the activity of cotransfected IKK-β when it was overexpressed, it failed to activate endogenous IKK. Furthermore, expression of pX stimulated NF-κB nuclear translocation and transcriptional activity in IKK-γ-null fibroblast 5R cells. Our data indicate that pX stimulates NF-κB activity through a mechanism that is dependent on IκBα degradation but not on IKK activation.
Colonic production and expression of IL-4, IL-6, and IL-10 in neonatal suckling rats after LPS challenge
Authors: Adams Jodi K. , Tepperman Barry L.
Published: December 2017

It has been demonstrated that the neonatal suckling rat is more susceptible to endotoxin [lipopolysaccharide (LPS)]-induced colonic damage compared with weaned littermates. There is evidence to suggest that differences in the production of certain cytokines, including interleukin (IL)-4, IL-6, and IL-10, are associated with intestinal inflammation in children. We have examined the production, localization, and mRNA detection of these cytokines in suckling and weaned rat colons after bacterial LPS challenge. Suckling (10 day old) and weaned (25 day old) rats were injected with LPS (3 mg/kg ip). Colon samples were taken up to 4 h after treatment, and cytokines were measured by ELISA. LPS-induced cytokine levels were significantly different in suckling rats compared with weaned rats. Cytokine localization to the colonic mucosa was evident in suckling rats up to 4 h after LPS administration but was not consistently seen in weaned rats. The mRNA for cytokines examined were detected by RT-PCR in suckling but not in weaned rat colons after LPS treatment. Induction of neutropenia via anti-neutrophil serum (ANS) administration did not affect cytokine mRNA detection in neonates after LPS treatment. Weaned animals displayed positive detection of all cytokines examined after ANS. Therefore, we have shown that the suckling rat displays a different production and expression of colonic IL-4, IL-6, and IL-10 compared with weaned littermates after LPS challenge. Furthermore, neutrophils may be implicated in colonic cytokine expression after LPS challenge in rats.
Desensitization of ileal vagal receptors by short-chain fatty acids in pigs
Authors: Cuche G. , Blat S. , Malbert C. H.
Published: December 2017

Coloileal reflux episodes trigger specialized ileal motor activities and inhibit gastric motility in pigs. The initiation of these events requires the detection by the distal ileum of the invading colonic contents that differ from the ileal chyme primarily in short-chain fatty acid (SCFA) concentrations. In addition to the already described humoral pathway, this detection might also involve ileal vagal afferents. Sensitivity to SCFA of 12 ileal vagal units was investigated in anesthetized pigs with single-unit recording at the left cervical vagus. SCFA mixtures (0.35, 0.7, and 1.4 mol/l) containing acetic, propionic, and butyric acids in proportions identical to that in the porcine cecocolon were compared with isotonic and hypertonic saline. All units behaved as slowly adapting mechanoreceptors (half-adaptation time = 35.4 ± 15.89 s), and their sensitivity to local mechanical probing was suppressed by local anesthesia; 7 units significantly decreased their spontaneous firing with 0.7 and 1.4 but not 0.35 mol/l SCFA infusion compared with hypertonic or isotonic saline. Similarly, the response induced by distension in the same seven units was reduced (5 neurons) or abolished (2 neurons) after infusion of 0.7 (22.8 ± 2.39 impulses/s) and 1.4 (30.3 ± 2.12 impulses/s) mol/l SCFA solutions compared with isotonic saline (38.6 ± 4.09 impulses/s). These differences in discharge were not the result of changes in ileal compliance, which remained constant after SCFA. In conclusion, SCFA, at concentrations near those found during coloileal reflux episodes, reduced or abolished mechanical sensitivity of ileal vagal afferents.
Ontogeny of hepatic enzymes involved in serine- and folate-dependent one-carbon metabolism in rabbits
Authors: Thompson Henry R. , Jones Gayle M. , Narkewicz Michael R.
Published: December 2017

Serine occupies a central position in folate-dependent, one-carbon metabolism through 5,10-methylenetetrahydrofolate (MTHF) and 5-formyltetrahydrofolate (FTHF). We characterized the ontogeny of the specific activity of key enzymes involved in serine, 5,10-MTHF, and 5-FTHF metabolism: methenyltetrahydrofolate synthetase (MTHFS), MTHF reductase (MTHFR), the glycine cleavage system (GCS), methionine synthase (MS), and serine hydroxymethyltransferase (SHMT) in rabbit liver, placenta, brain, and kidney. In liver, MTHFS activity is low in the fetus (0.36 ± 0.07 nmol · min−1· mg protein−1), peaks at 3 wk (1.48 ± 0.50 nmol · min−1· mg protein−1), and then decreases to adult levels (1.13 ± 0.32 nmol · min−1· mg protein−1). MTHFR activity is highest early in gestation (24.9 ± 2.4 nmol · h−1· mg protein−1) and declines rapidly by birth (4.7 ± 1.3 nmol · h−1· mg protein−1). MS is highest during fetal life and declines after birth. Cytosolic SHMT activity does not vary during development, but mitochondrial SHMT peaks at 23 days. GCS activity is high in the fetus and the neonate, declining after weaning. In placenta and brain, all activities are low throughout gestation. Cytosolic and mitochondrial SHMT activities are low in kidney and rise after weaning, whereas MTHFS is low throughout development. These data suggest that the liver is the primary site of activity for these enzymes. Throughout development, there are multiple potential sources for production of 5,10-MTHF, but early in gestation high MTHFR activity and low MTHFS activity could reduce 5,10-MTHF availability.
Chronic ethanol consumption exacerbates microcirculatory damage in rat mesentery after reperfusion
Authors: Han Jing-Yan , Miura Soichiro , Akiba Yasutada , Higuchi Hajime , Kato Shinzo , Suzuki Hidekazu , Yokoyama Hirokazu , Ishii Hiromasa
Published: December 2017

Although the negative effect of excessive alcohol consumption on later stressful events has long been recognized, pathophysiological mechanisms are incompletely understood. We examined possible roles of oxygen radicals and glutathione content in mesenteric venules of chronically ethanol-fed rats exposed to ischemia-reperfusion. Changes in microvascular hemodynamics, such as red blood cell (RBC) velocity, leukocyte adherence, and albumin extravasation, were monitored in postcapillary venules by intravital fluorescence microscopy. Chronic ethanol feeding significantly exaggerated the magnitude of the decrease in RBC velocity, the increased number of adherent leukocytes, and increased albumin leakage elicited by 10 min of ischemia followed by 30 min of reperfusion. Oxidative stress in the endothelium of venules monitored by dihydrorhodamine 123 (DHR) fluorescence was more severe in rats fed ethanol chronically. Both superoxide dismutase and N-acetyl-l-cysteine, which is known to increase glutathione content, reduced the ischemia-reperfusion-induced decrease in RBC velocity, the number of adherent leukocytes, and the increase in albumin leakage, as well as oxidative activation of DHR. This suggests that the increased reperfusion-induced microvascular disturbances in the mesenteric venules of rats fed ethanol chronically are significantly correlated with excessive production of oxygen-derived free radicals and decreased glutathione synthesis.
Complement factor C5a exerts an anti-inflammatory effect in acute pancreatitis and associated lung injury
Authors: Bhatia Madhav , Saluja Ashok K. , Singh Vijay P. , Frossard Jean-Louis , Lee Hong-Sik , Bhagat Lakshmi , Gerard Craig , Steer Michael L.
Published: December 2017

Complement factor C5a acting via C5a receptors (C5aR) is recognized as an anaphylotoxin and chemoattractant that exerts proinflammatory effects in many pathological states. The effects of C5a and C5aR in acute pancreatitis and in pancreatitis-associated lung injury were evaluated using genetically altered mice that either lack C5aR or do not express C5. Pancreatitis was induced by administration of 12 hourly injections of cerulein (50 μg/kg ip). The severity of pancreatitis was determined by measuring serum amylase, neutrophil sequestration in the pancreas, and acinar cell necrosis. The severity of lung injury was evaluated by measuring neutrophil sequestration in the lung and pulmonary microvascular permeability. In both strains of genetically altered mice, the severity of pancreatitis and pancreatitis-associated lung injury was greater than that noted in the comparison wild-type strains of C5aR- and C5-sufficient animals. This exacerbation of injury in the absence of C5a function indicates that, in pancreatitis, C5a exerts an anti-inflammatory effect. Potentially, C5a and its receptor are capable of both promoting and reducing the extent of acute inflammation.
VII. EnteropathogenicEscherichia coli: physiological alterations from an extracellular position
Authors: Hecht Gail
Published: December 2017

Enteropathogenic Escherichia coli (EPEC) is primarily associated with infantile diarrhea in developing countries. This intriguing pathogen exerts numerous physiological effects on its host target tissue, the intestinal epithelium, all from an extracellular location. Expression of a type III secretory apparatus allows this organism to transfer bacterial effector molecules directly into host cells. As a result of EPEC attachment to and/or translocation of proteins into intestinal epithelial cells, many signaling cascades are activated. Ultimately, host functions are perturbed, including alteration of ion transport, disruption of the tight junction barrier, and activation of the inflammatory response.
Mechanisms of intestinal gas retention in humans: impaired propulsion versus obstructed evacuation
Authors: Serra Jordi , Azpiroz Fernando , Malagelada Juan-R.
Published: December 2017

To explore the clinical role of intestinal gas dynamics, we investigated two potential mechanisms of gas retention, defective propulsion and obstructed evacuation. In healthy subjects, a gas mixture was continuously infused into the jejunum (4 ml/min) 1) during a 2-h control period of spontaneous gas evacuation and 2) during a 2-h test period either with impaired gut propulsion caused by intravenous glucagon ( n = 6) or with obstructed (self-restrained) anal evacuation ( n = 10) while anal gas evacuation, sympton perception (0–6 scale), and abdominal girth were measured. Impaired gut propulsion and obstructed evacuation produced similar gas retention (558 ± 68 ml and 407 ± 85 ml, respectively, vs. 96 ± 58 ml control; P < 0.05 for both) and abdominal distension (8 ± 3 mm and 6 ± 3 mm, respectively, vs. 1 ± 1 mm control; P < 0.05 for both). However, obstructed evacuation increased symptom perception (2.3 ± 0.6 score change; P < 0.05), whereas gas retention in the glucagon-induced hypotonic gut was virtually unperceived (−0.4 ± 0.7 score change; not significant). In conclusion, the perception of intestinal gas accumulation depends on the mechanism of retention.
Attenuation of CCl4-induced hepatic fibrosis by GdCl3treatment or dietary glycine
Authors: Rivera C. A. , Bradford B. U. , Hunt K. J. , Adachi Y. , Schrum L. W. , Koop D. R. , Burchardt E.-R. , Rippe R. A. , Thurman R. G.
Published: December 2017

The role of Kupffer cells in CCl4-induced fibrosis was investigated in vivo. Male Wistar rats were treated with phenobarbital and CCl4for 9 wk, and a group of rats were injected with the Kupffer cell toxicant gadolinium chloride (GdCl3) or were fed glycine, which inactivates Kupffer cells. After CCl4alone, the fibrosis score was 3.0 ± 0.1 and collagen protein and mRNA expression were elevated, but GdCl3or glycine blunted these parameters. Glycine did not alter cytochrome P-450 2E1, making it unlikely that glycine affects CCl4metabolism. Treatment with GdCl3or glycine prevented CCl4-induced increases in transforming growth factor (TGF)-β1 protein levels and expression. CCl4treatment increased α-smooth muscle actin staining (score 3.0 ± 0.2), whereas treatment with GdCl3and glycine during CCl4exposure blocked this effect (1.2 ± 0.5); there was no staining with glycine treatment. These results support previous in vitro data and demonstrate that treatment of rats with the selective Kupffer cell toxicant GdCl3prevents stellate cell activation and the development of fibrosis.