bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of long-term orall-arginine on esophageal motility and gallbladder dynamics in healthy humans
Authors: Luiking Y. C. , Weusten B. L. A. M. , Portincasa P. , Van Der Meer R. , Smout A. J. P. M. , Akkermans L. M. A.
Published: December 2017

Inhibitory nitrergic neurons are known to play a role in the regulation of motility patterns of the distal esophagus, the lower esophageal sphincter (LES), and the gallbladder. Our study aim was to investigate the effects of “long-term” (i.e., prolonged) oral intake ofl-arginine (l-Arg), the endogenous source for nitric oxide (NO) synthesis, on postprandial LES pressure (LESP), esophageal motility, gastroesophageal reflux, and gallbladder motility. l-Arg (30 g/day) or glycine (placebo; 13 g/day; isosmolar) was given orally to 10 healthy male volunteers for 8 days, according to a randomized, crossover design. Twenty-four-hour urinary nitrite/nitrate excretion was measured to indicate NO synthesis. Basal early postprandial LESP was lower after l-Arg ingestion (2.2 kPa) than after glycine ingestion (2.7 kPa) ( P < 0.05).l-Arg abolished the physiological late postprandial rise in LESP. Transient LES relaxations were longer lasting after l-Arg ingestion ( P < 0.02). Esophageal motility and reflux were not affected (not significant). Fasting and residual gallbladder volumes were greater afterl-Arg ingestion ( P < 0.05). Urinary nitrite/nitrate excretion was higher after l-Arg intake ( P < 0.05). In conclusion, long-term oral l-Arg suppresses late postprandial LESP increase, prolongs transient LES relaxations, and increases fasting and residual gallbladder volumes. These effects may be mediated by increased NO synthesis.
Interaction between neurokinin A, VIP, prostanoids, and enteric nerves in regulation of duodenal function
Authors: Hällgren Anneli , Flemström Gunnar , Nylander Olof
Published: December 2017

Neurokinin A (NKA) induces duodenal motility and increases mucosal permeability and bicarbonate secretion in the in situ perfused duodenum in anesthetized rats. In the present study, the NKA-induced increase in mucosal permeability was potentiated by luminal perfusion with lidocaine and diminished by vasoactive intestinal peptide (VIP) but unaltered by elevated intraluminal pressure. Elevation of intraluminal pressure, however, potentiated the stimulatory effect of NKA on bicarbonate secretion. In contrast, the tachykinin decreased the rate of alkalinization in rats subjected to elevated intraluminal pressure and treated with indomethacin. Similarly, NKA partially inhibited the VIP-stimulated bicarbonate secretion. Luminal lidocaine did not affect the secretory response to NKA. The motility induced by NKA was unaffected by VIP or lidocaine but decreased by elevated intraluminal pressure. It is concluded that the NKA-induced increase in duodenal mucosal bicarbonate secretion is independent of neurons and possibly mediated by prostanoids. The increase in mucosal permeability in response to NKA may be suppressed by mucosal nerves, perhaps utilizing VIP as one of the transmitters.
Biomechanical and sensory parameters of the human esophagus at four levels
Authors: Patel Rig S. , Rao Satish S. C.
Published: December 2017

The biomechanical and sensory characteristics of the lower esophageal sphincter (LES) and those of the striated and smooth muscle portions of the esophagus have not been compared in humans. Our aim was to determine sensory perception, cross-sectional area (CSA), and biomechanical parameters at different levels of the esophagus. We studied 11 healthy volunteers, using impedance planimetry. Intermittent balloon distensions (5–60 cmH2O) were performed at four sites: 1) the LES, 2) 5 cm above LES (distal), 3) 10 cm above LES (mid), and 4) 5 cm below the upper esophageal sphincter (proximal). During these distensions, CSAs, biomechanical parameters, and sensory responses were measured. The mid-esophagus had a higher ( P < 0.05) CSA than the distal esophagus. The LES had the smallest CSA ( P < 0.05). The LES and the proximal esophagus had greater ( P < 0.05) wall tension and were less ( P < 0.05) deformable than the mid- or distal esophagus. Sensory thresholds were lower ( P < 0.05) in the proximal compared with the mid- or distal esophagus. Biomechanical and sensory parameters are not uniform along the length of the esophagus. The striated muscle portion is more sensitive and less compliant than the smooth muscle portion. These differences could affect the results of balloon distension tests of the esophagus.
Postischemic inflammation: a role for mast cells in intestine but not in skeletal muscle
Authors: Kanwar Samina , Hickey Michael J. , Kubes Paul
Published: December 2017

The objective of this study was to directly study a role for mast cells in ischemia-reperfusion (I/R)-induced mucosal and microvascular dysfunction. I/R was induced in the intestine and skeletal muscle (gastrocnemius and cremaster muscle) of wild-type mice and mast cell-deficient mice ( W/ Wv). Changes in mucosal permeability (blood-to-lumen clearance of51Cr-EDTA), leukocyte infiltration (myeloperoxidase activity in the intestine and intravital microscopy in the cremaster muscle), and vascular permeability (tissue wet-to-dry weight ratio and FITC-albumin leakage) were measured as indexes of tissue dysfunction. In wild-type animals, intestinal I/R induced a significant increase in mucosal permeability, leukocyte infiltration, and vascular permeability. Mast cell-deficient animals were completely protected from I/R-induced mucosal dysfunction. However, skeletal muscle I/R induced a significant increase in leukocyte infiltration, FITC-albumin leakage, and edema formation to the same degree in both wild-type and mast cell-deficient animals. These data suggest that mast cells may be important mediators of I/R-induced mucosal and microvascular dysfunction in the intestine but not of microvascular dysfunction in skeletal muscle.
Mechanisms of ferric citrate uptake by human hepatoma cells
Authors: Trinder Deborah , Morgan Evan
Published: December 2017

The mechanisms of uptake of non-transferrin-bound iron by human hepatoma cells (HuH7) were investigated using59Fe-citrate and [14C]citrate. The amount of iron associated with the cells increased linearly with time, whereas citrate uptake reached a plateau after 45 min, resulting in a cellular accumulation of iron over citrate. The cells displayed high-affinity membrane binding sites for citrate with maximum binding of 118 ± 17 pmol citrate/mg protein and a dissociation constant of 21 ± 2 μM ( n = 3). Iron uptake was saturable with a maximum uptake rate of 1.95 ± 0.43 pmol ⋅ mg protein−1⋅ min−1and an apparent Michaelis constant of 1.1 ± 0.1 μM. Nonradioactive ferric citrate and citrate inhibited59Fe uptake to a similar degree. This suggests that the uptake of citrate-bound iron is dependent on either binding to specific citrate binding sites or the concentration of unbound iron. The uptake of iron was inhibited by ferricyanide (>100 μM) and ferrous iron chelators but stimulated by ferrocyanide and ascorbate, suggesting that the iron is reduced from Fe3+to Fe2+and transported into the cell by an iron carrier-mediated step.
Water immersion-restraint stress induces expression of immediate-early genes in gastrointestinal tract of rats
Authors: Ueyama Takashi , Saika Misako , Koreeda Chikako , Senba Emiko
Published: December 2017

The aims of this study were to determine 1) which cells are involved in stress-induced acute gastric mucosal lesion and 2) what kinds of molecular alterations are induced by stress, using immediate-early genes (IEG) as tools for detection of cellular activation. Male Wistar rats were exposed to acute water immersion-restraint stress. Protein and mRNA for IEG were detected by immunohistochemistry and in situ hybridization, respectively. This stress induced the expression of c- fos and nerve growth factor-induced gene (NGFI-A) mRNA in gastric epithelial cells, the smooth muscle layer of small blood vessels, and the stomach wall. Stress upregulated the mRNA levels of these IEG in the duodenal epithelial cells and induced de novo expression of IEG in the smooth muscle layer of small blood vessels and the duodenal wall. These findings indicate that these cells are activated in response to stress. Expression of these IEG and/or transcriptional factors may reflect an initiation of mechanisms for repairing the lesions induced by stress as well as an adaptation to the stress.
Calcium signaling in cultured human and rat duodenal enterocytes
Authors: Chew Catherine S. , Säfsten Bengt , Flemström Gunnar
Published: December 2017

Vagal stimuli increase duodenal mucosal[Formula: see text] secretion and may provide anticipatory protection against acid injury, but duodenal enterocyte (duodenocyte) responses and cholinoceptor selectivity have not been defined. We therefore developed a stable primary culture model of duodenocytes from rats and humans. Brief digestion of scraped rat duodenal mucosa or human biopsies with collagenase/dispase yielded cells that attached to the extracellular matrix Matrigel within a few hours of plating. Columnar cells with villus enterocyte morphology that exhibited spontaneous active movement were evident between 1 and 3 days of culture. Rat duodenocytes loaded with fura 2 responded to carbachol with a transient increase in intracellular calcium concentration ([Ca2+]i), with an apparent EC50 of ∼3 μM. In a first type of signaling pattern, [Ca2+]ireturned to basal or near basal values within 3–5 min. In a second type, observed in cells with enlarged vacuoles characteristic of crypt cell morphology, the initial transient increase was followed by rhythmic oscillations. Human duodenocytes responded with a more sustained increase in [Ca2+]i, and oscillations were not observed. Rat as well as human duodenocytes also responded to CCK-octapeptide but not to vasoactive intestinal polypeptide. Equimolar concentrations (100 nM) of the subtype-independent muscarinic antagonist atropine and the M3 antagonist 4-diphenylacetoxy- N-methylpiperidine methiodide prevented the response to 10 μM carbachol, whereas the M1 antagonist pirenzepine and the M2 antagonists methoctramine and AF-DX 116BS had no effect at similar concentrations. Responses in rat and human duodenocytes were similar. A new agonist-sensitive primary culture model for rat and human duodenocytes has thus been established and the presence of enterocyte CCK and muscarinic M3 receptors demonstrated.
PAF and CD18 mediate neutrophil infiltration in upper gastrointestinal tract during intra-abdominal sepsis
Authors: Beyer A. James , Smalley David M. , Shyr Yi-Ming , Wood John G. , Cheung Laurence Y.
Published: December 2017

Neutrophil infiltration is a critical event in the development of multiple organ failure during sepsis. We hypothesized that platelet-activating factor (PAF) release contributes to neutrophil infiltration in the gastrointestinal tract during sepsis. In the first experiments we administered exogenous PAF (1.56, 6.25, 25, and 100 ng ⋅ kg−1⋅ min−1for 30 min) to urethan-anesthetized Sprague-Dawley rats. PAF was administered alone or in combination with either the PAF antagonist WEB-2086 (250 μg ⋅ kg−1⋅ min−1), a monoclonal antibody (MAb) to CD18, or a MAb to intercellular adhesion molecule 1 (ICAM-1). In separate groups of rats, cecal ligation and incision (CLI) was performed to create intra-abdominal sepsis, which we hypothesized would stimulate the release of endogenous PAF. CLI was performed in rats given either saline, WEB-2086, anti-CD18, or anti-ICAM-1 MAb. After these experiments, tissue myeloperoxidase (MPO) levels were determined as a marker of neutrophil infiltration. Both exogenous PAF and CLI induced significant increases in MPO activity in the stomach and duodenum. These increases were significantly attenuated by WEB-2086, anti-CD18 MAb, and anti-ICAM-1 MAb in both PAF- and CLI-treated rats. These results suggest that both the inflammatory mediator PAF and the CD18 integrins play a major role in neutrophil infiltration in the upper gastrointestinal tract during sepsis.
Unique mechanism of inhibition of Na+-amino acid cotransport during chronic ileal inflammation
Authors: Sundaram U. , Wisel S. , Fromkes J. J.
Published: December 2017

In the chronically inflamed ileum, unique mechanisms of alteration of transport processes suggest regulation by different immune-inflammatory mediator pathways. We previously demonstrated that Na+-glucose cotransport in the chronically inflamed ileum was inhibited by a decrease in cotransporter number without a change in glucose affinity. The aim of this study was to determine the alterations in Na+-amino acid cotransport in chronically inflamed ileum produced by coccidial infection in rabbits. [3H]alanine uptake was performed in cells and vesicles by rapid filtration. In villus cells from chronically inflamed ileum, Na+-K+-ATPase was reduced 50% and Na+-alanine cotransport was also reduced (5.8 ± 1.2 in normal and 1.4 ± 0.5 nmol/mg protein in inflamed; n = 6, P < 0.05). [3H]alanine uptake in brush-border membrane vesicles was reduced in chronically inflamed ileum (73.2 ± 1.2 in normal and 21.5 ± 3.2 pmol/mg protein in inflamed; n = 3, P < 0.05), suggesting a direct effect on the cotransporter itself. Na+-amino acid cotransport in chronically inflamed ileum was inhibited by a decrease in affinity without a change in the maximal rate of uptake, and unaltered steady-state mRNA levels also suggested that the number of cotransporters was unchanged. Thus the mechanisms of inhibition of Na+-amino acid cotransport and Na+-glucose cotransport in chronically inflamed ileum are different. These observations suggest that different immune-inflammatory mediators may regulate different transport pathways during chronic ileitis.
Adsorptive-mediated endocytosis of a basic peptide in enterocyte-like Caco-2 cells
Authors: Sai Yoshimichi , Kajita Masahiro , Tamai Ikumi , Wakama Jun , Wakamiya Tateaki , Tsuji Akira
Published: December 2017

The internalization of a basic peptide, 001-C8 [H-MeTyr-Arg-MeArg-d-Leu-NH(CH2)8NH2], into enterocyte-like Caco-2 cells was evaluated. Internalization of125I-labeled 001-C8 (125I-001-C8) increased time dependently and reached steady state at 60 min. The steady-state internalization of125I-001-C8 (7.24 ± 0.41 μl/mg protein) was temperature and concentration dependent and was significantly decreased by dansylcadaverine (500 μM), protamine (1 mM), poly-l-lysine (1 mM), E-2078 (1 mM), and ebiratide (1 mM), whereas poly-l-glutamic acid (1 mM), tyrosine (1 mM), and glycylglycine (25 mM) were not inhibitory. Predigestion of acid mucopolysaccharides by heparinase I, heparitinase, and chondroitinase ABC also decreased the internalization. The maximal internalization, the half-saturation constant, and the nonsaturable internalization of125I-001-C8 were 1.13 ± 0.23 pmol/mg protein, 0.47 ± 0.43 μM, and 3.13 ± 0.19 μl/mg protein, respectively. Confocal microscopy also indicated the internalization of fluorescence-derived 001-C8 [001-C8–4-nitrobenz-2-oxa-1,3-diazole (001-C8-NBD)]. Granular staining seen within the cell, excluding nuclei, indicated the sequestration of 001-C8-NBD within endocytotic vesicles. Dansylcadaverine and protamine strongly decreased the granular distribution of 001-C8-NBD within the cell. These results demonstrate that 001-C8 is taken up by Caco-2 cells via adsorptive-mediated endocytosis.
Pharyngoglottal closure reflex: identification and characterization in a feline model
Authors: Shaker Reza , Medda Bidyut K. , Ren Junlong , Jaradeh Safwan , Xie Pengyan , Lang Ivan M.
Published: December 2017

Earlier studies in humans have shown that pharyngeal stimulation by water at a threshold volume induces a brief vocal cord adduction, i.e., pharyngoglottal closure reflex. The present study was undertaken to 1) develop a suitable animal model for physiological studies of this reflex and 2) delineate its neural pathway and effector organs. Studies were done in cats by concurrent videoendoscopy and manometry followed by electromyographic studies. At a threshold volume (0.3 ± 0.06 ml), injection of water into the pharynx resulted in a brief closure of the vocal folds, closing the introitus to the trachea. Duration of this closure averaged 1.1 ± 0.1 s. Bilateral transection of the glossopharyngeal nerve completely abolished this reflex but not swallows induced by pharyngeal water stimulation. The pharyngoglottal closure reflex is present in the cats. The glossopharyngeal nerve is the afferent pathway of this reflex, and the interarytenoid and lateral cricoarytenoid muscles are among its target organs.
Expression of intestinal brush-border membrane hydrolases and ferritin after segmental ischemia-reperfusion in rats
Authors: Yeh Kwo-Yih , Yeh Mary , Glass Jonathan
Published: December 2017

Jejunal expression of three brush-border membrane (BBM) enzymes, intestinal alkaline phosphatase (IAP), lactose-phlorizin hydrolase (LPH), and sucrase-isomaltase (SI), and a cytosolic protein, ferritin (Ft), was investigated after transient segmental ischemia-reperfusion (I/R). I/R reduced mucosal IAP, LPH, and SI mRNAs to 36%, 11%, and 38% of normal jejunal levels after 3 h of reperfusion and to 22%, 8%, and 51% of normal jejunal levels after 6 h of reperfusion, respectively. Intriguingly, in the internal control jejunum IAP and LPH mRNAs also decreased significantly. LPH and SI mRNA rapidly recovered to levels significantly higher than those of normal jejunum at 12 h, whereas IAP mRNA levels did not recover until 48 h. Enzyme activity paralleled changes in mRNA levels in the ischemic reperfused jejunum. Electrophoretic mobility shift assays showed that I/R significantly increased SI footprinting 1 (SIF1) binding activity. The mobility of one of the DNA-protein complexes was further retarded in the presence of anti-Cdx-2 antibody, suggesting that either Cdx-2 or a related protein was interacting with the SIF1 sequences. Similar to BBM enzymes, cytosolic Ft mRNA and protein were significantly decreased at 3 and 6 h after I/R. By 12 h, Ft mRNA, but not Ft protein, had increased to higher than normal levels. We conclude that a rapid recovery of BBM mRNAs and enzymes occurs in regenerating mucosa after upper villus damage. The increase of SIF1 binding protein activity after I/R may enhance SI, and perhaps LPH, gene transcription. The expression of Ft is regulated at both pretranslational and translational levels.
Migration of intestinal intraepithelial lymphocytes into a polarized epithelial monolayer
Authors: Shaw Sunil K. , Hermanowski-Vosatka Anne , Shibahara Takeshi , McCormick Beth A. , Parkos Charles A. , Carlson Susan L. , Ebert Ellen C. , Brenner Michael B. , Madara James L.
Published: December 2017

Intraepithelial lymphocytes (IEL) are a phenotypically distinct population of lymphocytes that reside in mucosal epithelia, below the intercellular tight junctions. Although adhesive functions of this population have been previously studied, relatively little is known about IEL migration from the microvasculature into the epithelium. We demonstrated that cultured human IEL were capable of migration into polarized epithelial cells in vitro, where they assumed a subjunctional position, identical to that observed in vivo. The migration was rapid and efficient and was directionally polarized, such that IEL migrated into epithelial monolayers from the basolateral, but not the apical, aspect. After a 4-h period of residence, up to one-half of the IEL then exited the monolayer basolaterally. Migration was partially inhibited by pertussis toxin, suggesting a potential mechanism for IEL migration by chemokine receptor-mediated signaling. The conditions and ligand pairs used in IEL migration were different from those for neutrophils, another cell type known to migrate through epithelia. This system may serve as a model for microenvironmental homing of IEL into the epithelium.
Protein kinase G expression in the small intestine and functional importance for smooth muscle relaxation
Authors: Huber Andrea , Trudrung Peter , Storr Martin , Franck Hartmut , Schusdziarra Volker , Ruth Peter , Allescher Hans-Dieter
Published: December 2017

In functional experiments, the nitric oxide (NO) donor N-morpholino- N-nitroso-aminoacetonitrile or the cGMP analog 8-(4-chlorophenylthio)-cGMP caused a concentration-dependent, tetrodotoxin-resistant relaxation of precontracted strips from rat small intestine. The inhibitory effect of both substances was completely blocked at lower concentrations and was significantly attenuated at higher concentrations by the selective cGMP-dependent protein kinase (cGK) antagonist KT-5823 (1 μM). cGK-I was identified by immunohistochemistry in circular and longitudinal muscle, lamina muscularis mucosae, and smooth muscle cells of the villi and in fibroblast-like cells of the small intestine. Additionally, there was staining of a subpopulation of myenteric and submucous plexus neurons. Double staining for neuronal NO synthase (nNOS) and cGK-I demonstrated a colocalization of these two enzymes. Western blot analysis of smooth muscle preparations and isolated nerve terminals demonstrated that these structures predominantly contain the cGK-Iβ isoenzyme, whereas the cGK-Iα expression is about threefold less. The isoform cGK-II was entirely confined to mucosal epithelial cells. These results show that cGK-I is expressed in different muscular structures of the small intestine and participates in the NO-induced relaxation of gastrointestinal smooth muscle. The presence of cGK-I in NOS-positive enteric neurons further suggests a possible neuronal action site.
Cystatin A expression reduces bile salt-induced apoptosis in a rat hepatoma cell line
Authors: Jones Blake , Roberts Patricia J. , Faubion William A. , Kominami Eiki , Gores Gregory J.
Published: December 2017

We have previously demonstrated abrogation of bile salt-induced apoptosis by cathepsin B inhibitors. However, caspases have been strongly implicated in apoptosis, and the mechanistic interface between caspase and cathepsin B activation is unclear. Thus our aims were to determine the mechanistic relationship between caspases and cathepsin B in bile salt-induced apoptosis in a rat hepatoma cell line. Expression of cystatin A was used to inhibit cathepsin B, whereas Z-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) was used to inhibit caspases. Cystatin A expression prevented cathepsin B activation and apoptosis during treatment with glycochenodeoxycholate (GCDC), a toxic bile salt. Caspase N-acetyl-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin (DEVD-AMC) hydrolytic activity increased in both wild-type and cystatin A-transfected cells treated with GCDC, demonstrating caspase activation despite inhibition of cathepsin B. In contrast, Z-VAD-FMK blocked both DEVD-AMC hydrolytic activity and cathepsin B activity during GCDC treatment. Our data demonstrate that 1) bile salt-induced apoptosis can be inhibited by the cystatin A transgene and 2) caspase and cathepsin B activation are linked mechanistically with cathepsin B downstream of caspases.
Anaphylaxis-induced alterations in intestinal motility: role of extrinsic neural pathways
Authors: Scott R. B. , Tan D. T. M. , Miampamba M. , Sharkey K. A.
Published: December 2017

The roles of mast cells and extrinsic and vagal neural pathways in the anaphylaxis-induced alterations in motility observed at sites remote from antigen exposure were explored. Rats were sensitized to egg albumin (EA) and prepared with 1) electrodes to monitor intestinal myoelectric activity, 2) an isolated intestinal loop, and 3) either intact vagal innervation or a subdiaphragmatic vagotomy. Fasting myoelectric activity was recorded before and after challenge of the jejunum in continuity or the isolated loop with EA or BSA. Intestinal segments and the brain stems were processed for mast cell identification (intestine) or Fos immunoreactivity (brain stem). EA but not BSA challenge of the jejunum or the isolated loop induced altered motility at both sites and diarrhea. Granulated mast cells were significantly reduced at the site local to but not remote from challenge. Vagotomy did not inhibit antigen-induced alterations in motility or diarrhea. The number of Fos-immunoreactive nuclei in vagal sensory or motor nuclei was not significantly altered by vagotomy. Thus antigen challenge of sensitized animals causes mast cell degranulation only at the site of direct challenge but alters motility at sites local and remote from challenge. The remote response requires intact extrinsic but not necessarily vagal neural pathways.
A choline-rich diet improves survival in a rat model of endotoxin shock
Authors: Rivera Chantal A. , Wheeler Michael D. , Enomoto Nobuyuki , Thurman Ronald G.
Published: December 2017

This study investigated whether dietary choline can prevent endotoxin shock. Female Sprague-Dawley rats fed chow or chow plus choline chloride (0.025–0.4%) for 3 days were given lipopolysaccharide (LPS) via the tail vein. Eighty-three percent and 56% of chow-fed rats survived after 2.5 or 5.0 mg/kg LPS, respectively. Choline increased survival in a dose-dependent manner, with maximal effects observed at 0.4%; this dose of choline prevented mortality completely after 2.5 or 5 mg/kg LPS. Choline also improved the microscopic appearance of the lungs and blunted increases in serum aspartate aminotransferase levels. Intracellular Ca2+was monitored in liver and lung macrophages during LPS exposure. Ca2+increases in macrophages from choline-fed rats were blunted by 40–60% compared with chow-fed controls. Feeding choline also blunted tumor necrosis factor-α production. Feeding glycine, which prevents macrophage activation via a chloride channel, in addition to choline was even more effective than feeding choline alone, suggesting that glycine and choline act via distinct sites. These data are consistent with the hypothesis that choline diminishes endotoxin shock by preventing macrophage activation.
5-HT is present in nerves of guinea pig sphincter of Oddi and depolarizes sphincter of Oddi neurons
Authors: Hillsley Kirk , Mawe Gary M.
Published: December 2017

This study involved immunohistochemistry and intracellular electrophysiology to investigate serotonergic neurotransmission in the sphincter of Oddi (SO). 5-Hydroxytryptamine (HT)-positive neurons (14 cells/preparation) and nerve fibers were observed in the ganglionated plexus. Serotonergic nerve fibers, which persisted under 2- to 6-day organ culture, were densely distributed, with varicose endings encircling some SO neurons. When 5-HT was applied to SO neurons, it elicited three different responses: 1) a fast depolarization to 5-HT in 31 of 62 cells was mimicked by 2-methyl-5-HT and blocked by LY-278584 (1 μM); 2) a prolonged depolarization to 5-HT in 21 of 62 cells evoked an increase in input resistance and was attenuated by the 5-HT1P antagonist renzapride (1 μM) but not by the 5-HT4antagonist SDZ-205557 (0.1–10 μM); and 3) an indirect depolarization blocked by TTX or atropine was observed in 32 of 62 cells. 5-HT superfusion elicited a dose-dependent monophasic depolarization (EC50 = 2 μM, n=14). In conclusion, 5-HT is present in nerves of the SO and elicits both 5-HT3 and 5-HT1P receptor-mediated depolarizations, supporting the concept that 5-HT plays a role in SO regulation.
Characterization and mechanisms of the pharyngoesophageal inhibitory reflex
Authors: Lang Ivan M. , Medda Bidyut K. , Ren Junlong , Shaker Reza
Published: December 2017

The objectives of this study were to identify and to characterize the pharyngoesophageal inhibitory reflex (PEIR) in an animal model. Thirty-one cats (2.4–5.0 kg) were anesthetized using α-chloralose (45 mg/kg ip), and esophageal peristalsis was recorded manometrically. Secondary peristalsis was activated by rapid air injection (8–20 ml) at midesophagus or slow infusion of water through the manometric catheters. Neither stimulus activated primary peristalsis. The PEIR was activated by rapid water injection or focal mechanical stimulation of the pharynx. Rapid air injection activated secondary peristalsis in 92% of the trials, and slow water infusion activated 1 secondary peristalsis every 3.2 min. Pharyngeal stimulation by 0.3, 0.5, 0.8, or 1.0 ml of water inhibited or blocked ongoing secondary peristalsis in 67, 82, 97, or 93% of trials, respectively. Mechanical stimulation of the posterior wall of the pharynx with 11–20 g pressure attenuated secondary peristalsis in 96% of the trials or blocked secondary peristalsis in 41% of the trials. Centripetal electrical stimulation at 30 Hz, 0.2 ms, 2 V for 4 s of the superior laryngeal (SLN) or glossopharyngeal (GPN) nerves blocked or inhibited secondary peristalsis in 100% of the trials. Bilateral transection of the GPN ( n = 8), but not the SLN ( n = 6), blocked the PEIR. Anesthetization of the pharyngeal mucosa using lidocaine (2%) blocked the PEIR ( n = 3). We concluded that 1) the PEIR exists in the cat, 2) mechanical stimulation of the pharynx more strongly activates the PEIR than water, 3) activation of either SLN or GPN afferents attenuates ongoing secondary peristalsis, 4) the receptors mediating the PEIR are located in the pharyngeal mucosa, and 5) both SLN and GPN contribute to the PEIR, but the GPN is the major afferent limb of this reflex.
Characterization and splice variants of neuronal nitric oxide synthase in rat small intestine
Authors: Huber Andrea , Saur Dieter , Kurjak Manfred , Schusdziarra Volker , Allescher Hans-Dieter
Published: December 2017

The aim of this study was to characterize neuronal nitric oxide synthase (nNOS) activity and 5′-end splice variants in rat small intestine. nNOS was predominantly expressed in the longitudinal muscle layer, with attached myenteric plexus (LM-MP). The biochemical properties of NOS activity in enriched nerve terminals resemble those of nNOS isolated from the brain. Western blot analysis of purified NOS protein with an nNOS antibody showed a single band in the particulate fraction and three bands in the soluble fraction. Rapid amplification of 5′ cDNA ends-PCR revealed the presence of three different 5′-end splice variants of nNOS. Two variants encode for nNOSα, which has a specific domain for membrane association. The third variant encodes for nNOSβ, which lacks the domain for membrane association and should therefore be soluble. nNOS is predominantly expressed in LM-MP and can be enriched in enteric nerve terminals. We present the first evidence that three 5′-end splice variants of nNOS encoding two different proteins are expressed in rat small intestine. These two nNOS enzymes exhibit different subcellular locations and might be implicated in different biological functions.
T lymphocyte-dependent and -independent intestinal smooth muscle dysfunction in theT.spiralis-infected mouse
Authors: Vallance Bruce A. , Croitoru Kenneth , Collins Stephen M.
Published: December 2017

We examined the profile of increased intestinal muscle contractility after primary infection with Trichinella spiralis in the mouse, correlating it with parasite expulsion. We also examined the extent to which the changes in muscle contraction were T lymphocyte dependent, by infecting athymic and SCID mice. Infection was accompanied by increased tension development by intestinal muscle. Two components of this response were identified, a rapid peak increase in tension generation observed on day 6 postinfection, and a smaller but sustained increase in tension evident thereafter in euthymic BALB/c mice. The peak muscle response was significantly delayed in infected athymic and SCID mice, along with a corresponding reduction in the magnitude of the sustained component. These changes were accompanied by reduced parasite expulsion in athymic and SCID mice, compared with euthymic mice. Reconstitution of T cell function in athymic mice restored both the acute and sustained profile of muscle contraction seen in euthymic mice, and this was accompanied by faster expulsion of the worms. These results identify T cell-dependent and -independent components of the muscle response to nematode infection in the mouse and suggest that the onset of the peak contractile response, as well as the magnitude of the sustained muscle response, contributes to parasite eviction from the gut.
III. Intracellular signaling in response to toxic liver injury
Authors: Jones Brett E. , Czaja Mark J.
Published: December 2017

Toxin-induced liver injury was formerly considered a passive biochemical event, but recent evidence has demonstrated that signal transduction pathways actively modulate the hepatocyte’s response to this form of injury. Investigations have examined the effects of a variety of toxins on the activation of receptor-coupled signal transduction, mitogen-activated protein kinases, and Fas signaling, as well as the generation of second messengers such as ceramide and nitric oxide. Many of these pathways culminate in the activation of transcription factors such as activator protein-1, c-Myc, or nuclear factor-κB. This Themes article discusses the effects of toxic injury on these signaling pathways and their known functions in regulating hepatocyte death and proliferation following injury.
Rat gastroduodenal motility in vivo: interaction of GABA and VIP in control of spontaneous relaxations
Authors: Krantis Anthony , Mattar Kamal , Glasgow Ian
Published: December 2017

Spontaneous relaxations occurring within motor activity in the rat gastroduodenum in vivo can be distinguished by their dependence on either nitric oxide (NO) or ATP. We examined the interaction of γ-aminobutyric acid (GABA) and vasoactive intestinal peptide (VIP) within pathways controlling this activity in the antrum (S) and duodenum (D) of anesthetized Sprague-Dawley rats, using miniaturized extraluminal foil strain gauges oriented perpendicular to (S1, D1) or in the axis of (S2) the circular smooth muscle. The NO synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME; 10 mg/kg iv) attenuated ( P < 0.05) antral relaxations and, in the duodenum, nonpropagating “intergroup” relaxations. The GABAA receptor antagonist bicuculline (350 μg/kg sc) had similar effects. The GABAA agonist 3-amino-1-propanesulfonic acid stimulatedl-NAME-sensitive relaxations at S1 and D1. Propagating “grouped” responses were unchanged. VIP (6 μg/kg iv) always induced a relaxation of the duodenum, which was attenuated by bicuculline andl-NAME. VIP caused simultaneous responses at S1 and S2; however, the antrum displayed either contraction or relaxation in response to VIP. All antral relaxations in response to VIP were attenuated ( P < 0.05) byl-NAME; however, only VIP-induced relaxations at S1 were sensitive to bicuculline. VIP-induced contractions were also unaffected. GABAA receptors mediate the pathway(s) controlling NO-related spontaneous relaxations of the antrum and duodenal circular muscle. All VIP-induced relaxations are mediated by NO. Spontaneous relaxations of the rat gastroduodenum include responses that involve a GABAAergic NO-related pathway, which is targeted by VIP. In addition, VIP can target NO relaxations of the antrum via other pathways.
Endogenous cholecystokinin in postprandial lower esophageal sphincter function and fundic tone in humans
Authors: Zerbib Frank , Bruley Des Varannes Stanislas , Scarpignato Carmelo , Leray Véronique , D’Amato Massimo , Rozé Claude , Galmiche Jean-Paul
Published: December 2017

Transient lower esophageal sphincter (LES) relaxations (TLESRs) are the main underlying mechanism of gastroesophageal reflux. Although CCK acts through CCK-A receptors to increase the TLESRs induced by gastric distension, the respective roles of endogenous CCK and fundic tone in triggering postprandial TLESRs remain unknown. The aim of this study was to determine the effect of the CCK-A receptor antagonist, loxiglumide, on postprandial LES function and fundic tone in humans. LES motor events and fundic tone were simultaneously monitored in two groups of healthy volunteers. Recordings were performed during fasting and for 3 h after a liquid meal (200 ml/200 kcal) administered either orally or intraduodenally at a rate mimicking gastric emptying. Each subject received loxiglumide (10 mg ⋅ kg−1 ⋅ h−1) or saline (control) in randomized order, which was started 40 min before the meal and maintained for 3 h thereafter. After the oral meal, loxiglumide significantly reduced TLESRs ( P = 0.002) without significantly affecting LES pressure and fundic tone. After duodenal infusion of the meal, loxiglumide totally abolished the increase in TLESRs, reduced LES pressure fall ( P < 0.02), and strongly inhibited fundic relaxation ( P = 0.0001). We concluded that endogenous CCK is involved in the postprandial control of both LES function and fundic tone through activation of CCK-A receptors.
Rate at which glutamine enters TCA cycle influences carbon atom fate in intestinal epithelial cells
Authors: Quan J. , Fitch M. D. , Fleming S. E.
Published: December 2017

Glutamine carbon entry into the tricarboxylic acid (TCA) cycle was assessed in small intestinal epithelial cells by measuring CO2production from [1-14C]glutamine, and these data together with [U-14C]glutamine data were used to calculate fractional oxidation rates for glutamine. CO2production from either [1-14C]glutamine or [U-14C]glutamine showed saturation kinetics, and the concentration needed to achieve the half-maximal rate of CO2production was 0.7 and 0.4 mmol/l, respectively. Maximal rate for [1-14C]glutamine was twice that for [U-14C]glutamine. Increasing glutamine concentration did not cause proportional increases in glutamine entry into the TCA cycle and glutamine oxidation. Consequently, fractional oxidation of glutamine decreased with increasing glutamine concentration. Fractional oxidation could be predicted from the rate at which glutamine carbon entered the TCA cycle. (Aminooxy)acetic acid, an aminotransferase inhibitor, reduced entry of glutamine into the TCA cycle and increased fractional oxidation of glutamine. Glutamate carbon entered the TCA cycle at about one-half the rate of glutamine-derived glutamate carbon and had a higher fractional oxidation rate when provided at equivalent concentrations to glutamine. These differences in the rate of entry predictably account for the differences in the metabolic fate of glutamine vs. glutamate carbon.
Aggravating action of zymosan on acute liver damage in perfused liver of rats treated withd-galactosamine
Authors: Cui Tai-Xing , Iwai Masaru , Yamauchi Tadashige , Shimazu Takashi
Published: December 2017

To study the role of Kupffer cells in the aggravation of liver injury, effects of zymosan on acute liver damage were explored using perfused livers of rats 24 h after intraperitoneal injection ofd-galactosamine (800 mg/kg). The leakage of lactate dehydrogenase and aspartate aminotransferase into the effluent was used to indicate acute liver damage. Infusion of zymosan (30 μg/ml) into the portal vein rapidly increased the leakage of lactate dehydrogenase and aspartate aminotransferase from galactosamine-treated liver with decreased perfusion flow. Pretreatment of animals with gadolinium, which diminished an immunostaining of resident macrophages in the injured liver, significantly attenuated the flow reduction induced by zymosan, whereas it did not affect the increases in enzyme leakage. Infusions of PGF2α, PGE2, and leukotriene D4, the eicosanoids mainly produced by Kupffer cells, decreased perfusion flow without rapid augmentation of enzyme leakage from galactosamine-treated liver. These results indicate that zymosan potentiates acute liver damage after galactosamine injection and suggest that certain types of nonparenchymal cells other than Kupffer cells are mainly involved in the action of zymosan.
Segment-specific effects of epinephrine on ion transport in the colon of the rat
Authors: Hörger Silke , Schultheiß Gerhard , Diener Martin
Published: December 2017

The effect of epinephrine on transport of K+, Na+, Cl−, and[Formula: see text] across the rat colon was studied using the Ussing chamber technique. Epinephrine (5 × 10−6mol/l) induced a biphasic change in short-circuit current ( Isc) in distal and proximal colon: a transient increase followed by a long-lasting decay. The first phase of the Iscresponse was abolished in Cl−-poor solution or after bumetanide administration, indicating a transient induction of Cl−secretion. The second phase of the response to epinephrine was suppressed by apical administration of the K+channel blocker, quinine, and was concomitant with an increase in serosal-to-mucosal Rb+flux, indicating that epinephrine induced K+secretion, although this response was much smaller than the change in Isc. In addition, the distal colon displayed a decrease in mucosal-to-serosal and serosal-to-mucosal Cl−fluxes when treated with epinephrine. In the distal colon, indomethacin abolished the first phase of the epinephrine effect, whereas the second phase was suppressed by TTX. In the proximal colon, indomethacin and TTX were ineffective. The neuronally mediated response to epinephrine in the distal colon was suppressed by the nonselective β-receptor blocker, propranolol, and by the β2-selective blocker, ICI-118551, whereas the epithelial response in the proximal colon was suppressed by the nonselective α-blocker, phentolamine, and by the selective α2-blocker, yohimbine. These results indicate a segment-specific action of epinephrine on ion transport: a direct stimulatory action on epithelial α2-receptors in the proximal colon and an indirect action on secretomotoneurons via β2-receptors in the distal colon.
Regulation of apolipoprotein secretion by biliary lipids in newborn swine intestinal epithelial cells
Authors: Wang Heng , Roberson Russell , Du Jianhui , Eshun John K. , Berschneider Helen M. , Black Dennis D.
Published: December 2017

Biliary lipids, composed of bile acids, cholesterol, and phosphatidylcholine, are a major source of luminal lipid in the small intestine. In the present study in a newborn swine intestinal epithelial cell line (IPEC-1), taurocholate and phosphatidylcholine were found to have no effect on apolipoprotein B (apo B) secretion but did significantly increase the basolateral secretion of apo A-I. This regulation of apo A-I secretion occurred at the pretranslational level for taurocholate and at the posttranslational level for phosphatidylcholine. The regulation of apo A-I secretion by phosphatidylcholine did not involve changes in apo A-I degradation and may involve mobilization of a preformed pool of apo A-I. Cholesterol, whether solubilized with taurocholate or phosphatidylcholine, had no effect on the secretion of either apo B or apo A-I. However, when taurocholate, phosphatidylcholine, and cholesterol were combined, apo B secretion was decreased, and the increase in apo A-I secretion noted with taurocholate and phosphatidylcholine alone was ablated. Another primary bile acid, taurochenodeoxycholate, was found to decrease apo B secretion but had no effect on apo A-I secretion. However, the significance of this effect is uncertain, since this bile acid caused significant cellular membrane injury, as evidenced by increased apical medium lactate dehydrogenase activity. Phosphatidylcholine, but not taurocholate, dramatically increased the basolateral secretion of radiolabeled phospholipid with a modest increase in cellular triglyceride radiolabeling. Furthermore, this effect of phosphatidylcholine on lipid synthesis did not require significant hydrolysis or uptake of the phosphatidylcholine molecule. Studies using radiolabeled taurocholate did not demonstrate active transport of taurocholate by these cells.
Role of actin in EGF-induced alterations in enterocyte SGLT1 expression
Authors: Chung Brian M. , Wong Jason K. , Hardin James A. , Gall D. Grant
Published: December 2017

Na+-glucose cotransporter (SGLT1) expression and the role of actin in epidermal growth factor (EGF)-induced alterations in glucose transport and brush-border surface area were examined in New Zealand White rabbit jejunal loops. In separate experiments, EGF or EGF concurrent with cytochalasin D, an inhibitor of actin polymerization, was administered to the experimental loop and compared with its vehicle control. SGLT1 expression was measured by Western blot in brush-border membrane vesicles (BBMV) after 5-min and 1-h exposure. Glucose kinetics were determined by a rapid filtration technique, and brush-border surface area was examined by electron microscopy after 1-h exposure. The effect of cytochalasin D alone on BBMV glucose kinetics and brush-border surface area was also assessed. EGF resulted in a significant increase in BBMV SGLT1 expression ( P < 0.05), glucose maximal uptake ( Vmax; P < 0.001), and absorptive brush-border surface area ( P < 0.001). These effects were abolished with concurrent cytochalasin D treatment. Cytochalasin D alone had no effect on glucose transport or brush-border surface area. The findings suggest that EGF acutely upregulates jejunal brush-border surface area and the Vmaxfor jejunal glucose uptake via the recruitment and insertion of SGLT1 from an internal pool into the brush border by a mechanism that is dependent on actin polymerization.
Epidermal growth factor regulates fatty acid uptake and metabolism in Caco-2 cells
Authors: Darimont Christian , Gradoux Nathalie , de Pover Alain
Published: December 2017

Epidermal growth factor (EGF) has been reported to stimulate carbohydrate, amino acid, and electrolyte transport in the small intestine, but its effects on lipid transport are poorly documented. This study aimed to investigate EGF effects on fatty acid uptake and esterification in a human enterocyte cell line (Caco-2). EGF inhibited cell uptake of [14C]palmitate and markedly reduced its incorporation into triglycerides. In contrast, the incorporation in phospholipids was enhanced. To elucidate the mechanisms involved, key steps of lipid synthesis were investigated. The amount of intestinal fatty acid-binding protein (I-FABP), which is thought to be important for fatty acid absorption, and the activity of diacylglycerol acyltransferase (DGAT), an enzyme at the branch point of diacylglycerol utilization, were reduced. EGF effects on DGAT and on palmitate esterification occurred at 2–10 ng/ml, whereas effects on I-FABP and palmitate uptake occurred only at 10 ng/ml. This suggests that EGF inhibited palmitate uptake by reducing the I-FABP level and shifted its utilization from triglycerides to phospholipids by inhibiting DGAT. This increase in phospholipid synthesis might play a role in the restoration of enterocyte absorption function after intestinal mucosa injury.
Transplanted hepatocytes proliferate differently after CCl4treatment and hepatocyte growth factor infusion
Authors: Gupta Sanjeev , Rajvanshi Pankaj , Aragona Emma , Lee Chang-Don , Yerneni Purnachandra R. , Burk Robert D.
Published: December 2017

To understand regulation of transplanted hepatocyte proliferation in the normal liver, we used genetically marked rat or mouse cells. Hosts were subjected to liver injury by carbon tetrachloride (CCl4), to liver regeneration by a two-thirds partial hepatectomy, and to hepatocellular DNA synthesis by infusion of hepatocyte growth factor for comparative analysis. Transplanted hepatocytes were documented to integrate in periportal areas of the liver. In response to CCl4treatments after cell transplantation, the transplanted hepatocyte mass increased incrementally, with the kinetics and magnitude of DNA synthesis being similar to those of host hepatocytes. In contrast, when cells were transplanted 24 h after CCl4administration, transplanted hepatocytes appeared to be injured and most cells were rapidly cleared. When hepatocyte growth factor was infused into the portal circulation either subsequent to or before cell transplantation and engraftment, transplanted cell mass did not increase, although DNA synthesis rates increased in cultured primary hepatocytes as well as in intact mouse and rat livers. These data suggested that procedures causing selective ablation of host hepatocytes will be most effective in inducing transplanted cell proliferation in the normal liver. The number of transplanted hepatocytes was not increased in the liver by hepatocyte growth factor administration. Repopulation of the liver with genetically marked hepatocytes can provide effective reporters for studying liver growth control in the intact animal.