bluuebunny/crossref_metadata_2025 huggingface dataset:
PACAPs stimulate duodenal bicarbonate secretion at PACAP receptors in the rat
Authors: Takeuchi K. , Takehara K. , Kato S. , Yagi K.
Published: December 2017

We investigated the effects of pituitary adenylate cyclase-activating polypeptides (PACAPs) on gastroduodenal HCO(3)- secretion in anesthetized rats and characterized their effects by comparison with the effects of vasoactive intestinal polypeptide (VIP). Under urethan anesthesia, a rat proximal duodenal loop or a rat stomach mounted in an ex vivo chamber (in the absence of acid secretion) was perfused with saline, and HCO(3)- secretion was measured at pH 7.0 using a pH-stat method and by addition of 10 mM HCl. Intravenous injection of PACAP-27 stimulated HCO(3)- secretion in a dose-dependent manner in the duodenum, but not in the stomach, although this peptide had no effect on duodenal HCO(3)- secretion after intracisternal administration. The duodenal HCO(3)- stimulatory action was similarly observed after intravenous administration of PACAP-38 and VIP, and the potency of action was in the following order: PACAP-27 > PACAP-38 = VIP. The duodenal HCO(3)- stimulatory action of PACAP-27 was potentiated by pretreatment with 3-isobutyl-1-methylxanthine, similar to that of prostaglandin E2, and was significantly attenuated by PACAP-(6--27) (PACAP antagonist) or Ac-Tyr1,D-Phe2-VIP (VIP antagonist) but was not affected by bilateral vagotomy or prior administration of atropine, verapamil, and indomethacin. Forskolin, the stimulator of adenylate cyclase, also increased HCO(3)- secretion in the duodenum, but not in the stomach. These results suggest that 1) PACAP is a potent stimulator of HCO(3)- secretion in the duodenum, but not in the stomach, and may be involved in the peripheral regulation of duodenal HCO(3)- secretion, 2) this action is mediated by adenosine 3',5'-cyclic monophosphate, probably through PACAP and VIP receptors, and 3) adenosine 3',5'-cyclic monophosphate is a mediator in duodenal, but not in gastric, HCO(3)- secretion.
Colonic smooth muscle cells possess a different subtype of somatostatin receptor from gastric smooth muscle cells
Authors: Corleto V. D. , Severi C. , Coy D. H. , Delle Fave G. , Jensen R. T.
Published: December 2017

Somatostatin (SS) alters colonic motility. To investigate whether SS has a direct effect on colonic smooth muscle cells, we prepared isolated muscle cells from the descending guinea pig colon and compared the effects of SS with those on isolated gastric smooth muscle cells. In gastric cells, SS had no effect on carbachol-induced contraction, whereas in colonic cells it caused inhibition. In colonic muscle cells, SS-28 caused >85% inhibition of contraction by cholecystokinin octapeptide (CCK-8), bombesin, 12-O-tetradecanoylphorbol-13-acetate, and ionomycin, whereas it had no effect on contraction by these agents in gastric cells. In gastric cells, SS inhibited relaxation. Three synthetic SS analogs had different relative affinities for causing effects in gastric and colonic cells. Pertussis toxin inhibited the action of SS-28 in each muscle cell type by 50-75%. SS-28 alone had a small contractile effect on cells from the circular layer of the colon. SS-28 inhibited carbachol-induced contraction in colonic cells from both the longitudinal and circular layers. These results demonstrate that the action of SS differs in colonic and gastric smooth muscle cells. SS inhibits contractants in colonic cells and relaxants in gastric cells. In colonic cells, SS has a weak contractile effect due to an effect on circular muscle cells and an inhibitory effect on cells from both longitudinal and circular layers. A different SS receptor subtype mediates the actions of SS in colonic and gastric muscle cells. In both cell types, the actions of SS are mediated by pertussis toxin-sensitive and -insensitive G proteins.
Interleukin-2-induced hepatic injury involves temporal patterns of cell adhesion in the microcirculation
Authors: Lentsch A. B. , Miller F. N. , Edwards M. J.
Published: December 2017

The treatment of metastatic cancer with interleukin-2 (IL-2) is limited by systemic toxicities, including hepatic dysfunction. The objective of this study was to determine the cellular mechanisms of IL-2-induced hepatic injury. Intravital microscopy was used for the direct observation of the murine hepatic microcirculation after 2 h, 2 days, and 4 days of IL-2 treatment. At each interval, leukocyte- and platelet-endothelial adherence were observed and quantitated. Simultaneously, sinusoidal perfusion, serum levels of glutamate pyruvate transaminase, and edema were measured as indexes of hepatic toxicity. IL-2 increased neutrophil adhesion acutely in association with decreased sinusoidal perfusion. Leukocyte adhesion subsided at 2 days, but platelet-endothelial interactions were enhanced and 40% of mice receiving IL-2 had microvascular thrombi. These effects occurred in conjunction with decreased sinusoidal perfusion and the development of hepatic edema. After 4 days of IL-2, maximal hepatic edema, hypoperfusion, and increased serum levels of glutamate pyruvate transaminase were associated with increased lymphocyte adhesion and microvascular thrombosis. These data suggest coordinated, temporal roles of leukocytes and platelets in the generation of IL-2-induced hepatic injury.
Electrophysiological characterization of cultured hepatic stellate cells in rats
Authors: Kashiwagi S. , Suematsu M. , Wakabayashi Y. , Kawada N. , Tachibana M. , Koizumi A. , Inoue M. , Ishimura Y. , Kaneko A.
Published: December 2017

This study aimed to examine electrophysiological properties of cultured rat hepatic stellate cells (HSCs) using the whole cell configuration of patch-clamp technique. At least three different current components were identified. First, when the membrane was depolarized to voltages more positive than -40 mV, a transient outward K+ current was evoked. Second, membrane hyperpolarization below -60 mV evoked a sustained and inward-rectifying K+ current. The third component was a current flowing outward, which was activated when the cell was depolarized more positively than 0 mV. The channel for this current allowed Na+, K+, and Cl- to pass nonspecifically, suggesting the presence of hemi gap-junctional channel. Furthermore, a laser photobleaching technique revealed the presence of gap junctions between adjacent HSCs. A voltage-gated Ca2+ current, which is known to occur in smooth muscle cells, was searched for but was not detectable. These results suggest that membrane potential of HSCs is determined specifically by the two distinct K+ channels and by an intercellular mechanism involving gap-junctional communication.
Acute and neonatal capsaicin treatment inhibit jejunal amino acid absorption through a Na+-dependent mechanism
Authors: Barada K. A. , Dika S. S. , Atweh S. F. , Saade N. E. , Nassar C. F.
Published: December 2017

It has recently been shown that capsaicin inhibits alanine absorption in rat jejunum via mechanisms that involve intestinal capsaicin-sensitive primary afferent (CSPA) fibers. This study provides further evidence that the effect of capsaicin is neurally mediated and demonstrates that CSPA fibers regulate Na+-dependent amino acid absorption. In vivo, basal alanine absorption in rats neonatally treated with capsaicin was reduced by 35% below control. Furthermore, intraluminal perfusion of 400 microM capsaicin reduced jejunal alanine absorption by 31% in sham rats but had no significant effect in rats neonatally treated with capsaicin. In vitro, capsaicin significantly reduced uptake of alanine and proline by jejunal strips but had no effect on uptake of lysine. Tetrodotoxin (0.2 microM) partially blocked the effects of capsaicin but did not itself affect alanine absorption. Capsaicin reduced unidirectional mucosal-to-serosal alanine (1 mM) influx by 33%, an effect that becomes significant after 5 min of preincubation with capsaicin. Neonatal capsaicin treatment reduced basal alanine influx in jejunal strips by 37%; however, preincubation of these strips with capsaicin had no significant effect. Kinetic analysis of alanine steady-state uptake and influx by jejunal strips incubated with capsaicin revealed that capsaicin reduced the Na+-dependent component of alanine influx into intestinal epithelial cells. Long-term sensory denervation by capsaicin also decreased the Na+-dependent component of alanine absorption. These data suggest that intestinal capsaicin-sensitive primary afferent fibers regulate Na+-dependent amino acid absorption.
PSP expression in murine lacrimal glands and function as a bacteria binding protein in exocrine secretions
Authors: Robinson C. P. , Bounous D. I. , Alford C. E. , Nguyen K. H. , Nanni J. M. , Peck A. B. , Humphreys-Beher M. G.
Published: December 2017

Nonobese diabetic (NOD) mice, an animal model for type I autoimmune diabetes and autoimmune sialoadenitis, abnormally express parotid secretory protein (PSP) in the submandibular glands (Robinson, C. P., H. Yamamoto, A. B. Peck, and M. G. Humphreys-Beher. Clin. Immunol. Immunopathol. 79: 50-59, 1996). To evaluate possible PSP gene dysregulation in the NOD mouse, we have examined a number of organs and tissues for PSP mRNA transcripts and protein expression. Results indicate that PSP is produced in the lacrimal glands of NOD mice as well as most laboratory mouse strains. Although purified salivary PSP from C3H/HeJ or BALB/c mice fails to affect amylase enzyme activity in in vitro assays, PSP bound to whole bacteria in a Zn2+-dependent manner. Additionally, radiolabeled protein bound to specific bacterial membrane proteins using a ligand binding assay. PSP gene transcription, but not protein production, was observed in the heart and pancreas from NOD mice, indicating abnormal transcription of the PSP gene. Sequence analysis of PSP cDNA from NOD mice revealed numerous base differences (compared with the published PSP sequence) capable of leading to significant amino acid substitutions, suggestive of strain-specific differences for the protein in mice. Together these results suggest that there exists in the NOD mouse a dysregulation of PSP transcription in various tissues. However, except for C3H/HeJ mice, PSP appears as a normal product of the lacrimal glands where, as in saliva, it may function as a nonimmune antimicrobial agent in the protection of tissue surfaces exposed to the external environment.
Glutamine protects intestinal epithelial cells: role of inducible HSP70
Authors: Wischmeyer P. E. , Musch M. W. , Madonna M. B. , Thisted R. , Chang E. B.
Published: December 2017

Glutamine (Gln) protects gut mucosa against injury and promotes mucosal healing. Because the induction of heat shock proteins (HSP) protects cells under conditions of stress, we determined whether Gln conferred protection against stress in an intestinal epithelial cell line through HSP induction. Gln added to IEC-18 cells induces an increase in HSP70, a concentration-dependent effect also seen with mRNA. Two forms of injury, lethal heat (49 degrees C) and oxidant, were used, and viability was determined by 51Cr release. Gln-treated cells were significantly more resistant to injury. Treatment with 6-diazo-5-oxo-L-norleucine (DON), a nonmetabolizable analog of Gln, induced HSP70 and protected cells from injury, but less than Gln. These findings suggest that the effects of Gln on HSP70 induction and cellular protection are mediated by metabolic and nonmetabolic mechanisms. To determine whether HSP induction was central to the action of Gln and DON, quercetin, which blocks HSP induction, was used. Quercetin blocked HSP70 induction and the protective effect of Gln and DON. We conclude that the protective effects of Gln in intestinal epithelial cells are in part mediated by HSP70 induction.
A new method to measure gastric emptying in conscious dogs: a validity study and effects of EM523 and L-NNA
Authors: Tanaka T. , Mizumoto A. , Haga N. , Itoh Z.
Published: December 2017

A new method for measurement of gastric emptying without the use of radioisotope markers has been developed in dogs. A test meal was given after measurement of its freeze-dried weight, and 1-ml duodenal samples were collected through an indwelling tube at 15-min intervals, and their absolute weight was measured. The duodenum was continuously perfused with phenolsulfonphthalein to determine the recovery of each sample. Three different calorie or fat-enriched meals were administered with 100 ml saline containing polyethylene glycol as a liquid marker. The results showed that increasing the calorie load of, and adding fat to, the test meal proportionally delayed gastric emptying of the solid phase. Utilizing this method, it was found that EM523, an erythromycin derivative, accelerated the gastric emptying of solids, whereas N(omega)-nitro-L-arginine (L-NNA) markedly delayed the gastric emptying of both solids and liquids. In conclusion, this freeze-drying method is a reliable technique for measuring the gastric emptying of the solid phase in dogs.
Function of upper esophageal sphincter during swallowing: the grabbing effect
Authors: Pouderoux P. , Kahrilas P. J.
Published: December 2017

This study investigated deglutitive axial force developed within the pharynx, upper esophageal sphincter (UES), and cervical esophagus. Position and deglutitive excursion of the UES were determined using combined manometry and videofluoroscopy in eight healthy volunteers. Deglutitive clearing force was quantified with a force transducer to which nylon balls of 6- or 8-mm diameter were tethered and positioned within the oropharynx, hypopharynx, UES, and cervical esophagus. Axial force recordings were synchronized with videofluoroscopic imaging. Clearing force was dependent on both sphere diameter (P < 0.05) and location, with greater force exhibited in the hypopharynx and UES compared with the oropharynx and esophagus (P < 0.05). Within the UES, the onset of traction force coincided with passage of the pharyngeal clearing wave but persisted well beyond this. On videofluoroscopy, the persistent force was associated with the aboral motion of the ball caught within the UES. Force abated with gradual slippage of the UES around the ball. The force attributable to the combination of UES contraction and laryngeal descent was named the grabbing effect. The grabbing effect functions to transfer luminal contents distal to the laryngeal inlet at the end of the pharyngeal swallow, presumably acting to prevent regurgitation and/or aspiration of swallowed material.
Large but not small intrahepatic bile ducts are involved in secretin-regulated ductal bile secretion
Authors: Alpini G. , Glaser S. , Robertson W. , Rodgers R. E. , Phinizy J. L. , Lasater J. , LeSage G. D.
Published: December 2017

We have shown that agonist-regulated ductal secretion is limited to large cholangiocytes. To directly study cholangiocyte heterogeneity along the length of the normal biliary tree, we defined the genetic and functional expression of agonist-induced ductal secretion in intrahepatic bile duct units (IBDU) of different sizes. Small IBDU (< 15-microns diam) were separated from large IBDU (> or = 15-microns diam), and then ducts of different sizes were characterized by morphometric analysis, gene expression, secretin-induced adenosine 3',5'-cyclic monophosphate (cAMP) synthesis, and secretion by change in luminal size in response to agonists. IBDU diameters ranged from 11 to 65 microns. Secretin increased ductal secretion solely in large IBDU. Forskolin induced a modest increase in ductal secretion in small IBDU but markedly increased ductal secretion in large IBDU. Secretion increased Cl-/HCO3- exchanger activity and cAMP levels in large but not small IBDU. Secretin receptor and Cl-/HCO3 exchanger mRNAs were detected only in large IBDU. We propose that agonist-induced ductal secretion occurs in large (> or = 15-microns diam) but not small (< 15-microns diam) intrahepatic ducts.
Bile salt-induced apoptosis of hepatocytes involves activation of protein kinase C
Authors: Jones B. A. , Rao Y. P. , Stravitz R. T. , Gores G. J.
Published: December 2017

Toxic bile salts induce hepatocyte apoptosis, a model relevant to liver injury during cholestasis. However, the signaling mechanisms culminating in bile salt-induced apoptosis remain unclear. Because protein kinase C (PKC) is activated by bile salts in hepatocytes and causes apoptosis in other cells, we tested the hypothesis that bile salt-induced hepatocyte apoptosis is mediated by PKC. The PKC inhibitors chelerythrine and Go-6976 reduced, whereas a PKC agonist, phorbol 12-myristate 13-acetate (PMA), increased glycochenodeoxycholate (GCDC)-induced hepatocyte apoptosis. Membrane-associated total PKC activity was increased in GCDC-treated hepatocytes. Quantitative immunoblot analysis demonstrated membrane translocation of PKC-alpha, PKC-delta, and PKC-epsilon to hepatocyte membranes after administration of GCDC. Direct activation of PKC-alpha and PKC-delta by GCDC was also demonstrated using recombinant, baculovirus-expressed PKC isoforms in a medium of defined lipid composition. Chelerythrine and Go-6976 reduced, whereas PMA enhanced, cathepsin B activity during treatment of hepatocytes with GCDC, demonstrating coupling of PKC activity to the protease effector mechanisms of apoptosis. In conclusion, our data suggest for the first time that PKC-dependent signaling pathways play a critical role in bile salt-induced hepatocyte apoptosis.
Substance P in the dorsal vagal complex inhibits medullary TRH-induced gastric acid secretion in rats
Authors: Yang H. , Tache Y.
Published: December 2017

Neurons that contain substance P (SP) and thyrotropin-releasing hormone (TRH) in medullary midline raphe nuclei project to the dorsal vagal complex (DVC). The modulatory role of SP on basal gastric acid secretion (GAS) and TRH on DVC-induced stimulation of GAS was studied in urethan-anesthetized rats. The stable SP agonist, DiMe-C7 ([pGlu5, MePhe8, MeGly9]SP5-11, 50 and 100 pmol), injected unilaterally into the DVC reduced the GAS response (47 +/- 12 mumol/60 min) to coinjected TRH analog, RX 77368 (25 pmol), by 53% and 85%, respectively, whereas DiMe-C7 (100 pmol) alone had no effect on basal and pentagastrin-stimulated GAS. DiMe-C7 (100 pmol/site) inhibited the GAS response to kainic acid injected into the raphe pallidus (Rpa) when it was injected bilaterally into the DVC but not the hypoglossal nuclei. The SP nourokinin-1-receptor antagonist, CP-96,345, injected bilaterally into the DVC (1 nmol/ site) increased basal GAS (33 +/- 8 mumol/90 min) and potentiated the GAS response to kainic acid injected into the Rpa by 40%. These results suggest that SP acts on neurokinin-1 receptors in the DVC to reduce medullary TRH-induced stimulation of GAS in rats.
Epithelial localization of a reptilian Na+/H+ exchanger homologous to NHE-1
Authors: Harris S. P. , Strong T. V. , Wys N. , Richards N. W. , Pouyssegur J. , Ernst S. A. , Dawson D. C.
Published: December 2017

Basolateral membranes of turtle (Pseudemys scripta) colon epithelial cells exhibit robust Na+/H+ exchange activity that can be activated by cell shrinkage and is blocked by amiloride [M. A. Post and D. C. Dawson. Am. J. Physiol. 262 Cell Physiol. 31):C1089-C1094, 1992]. The colonic epithelium actively absorbs Na+ and secretes K+ and HCO3-, but the role of basolateral Na+/H+ exchange, if any, in transepithelial transport is unknown. The current studies were undertaken to identify the gene product(s) responsible for the observed basolateral Na+/H+ exchange activity and to determine the cellular localization of the reptilian Na+/H+ exchange protein. We cloned and sequenced partial-length cDNAs that are likely to encode a reptilian homologue of the mammalian NHE-1 Na+/H+ exchanger isoform. The partial-length cDNAs were > 80% identical to mammalian NHE-1 homologues at the nucleotide level and recognized a transcript (approximately 5.8-6.0 kb) in RNA isolated from turtle colon, small intestine, stomach, kidney, urinary bladder, heart, and liver. In situ hybridization showed that mRNA encoding the reptile homologue of NHE-1 was expressed predominantly in the epithelial cells of these tissues. Immunofluorescent localization of the reptilian Na+/H+ exchanger protein using an antibody raised against a human NHE-1 fusion protein confirmed that protein expression paralleled abundant mRNA expression in epithelial cells of turtle stomach and colon, as well as in some nephron segments, and showed that the reptile NHE-1 homologue was localized exclusively to the basolateral membranes of these cells. The relatively high level of NHE-1 expression in epithelial cells, particularly those of the colon and stomach, suggests that NHE-1 function is important for the maintenance or regulation of ion transport processes that occur in these cell types.
GSH transport in mitochondria: defense against TNF-induced oxidative stress and alcohol-induced defect
Authors: Fernandez-Checa J. C. , Kaplowitz N. , Garcia-Ruiz C. , Colell A. , Miranda M. , Mari M. , Ardite E. , Morales A.
Published: December 2017

Mitochondria generate reactive oxygen species (ROS) as byproducts of molecular oxygen consumption in the electron transport chain. Most cellular oxygen is consumed in the cytochrome-c oxidase complex of the respiratory chain, which does not generate reactive species. The ubiquinone pool of complex III of respiration is the major site within the respiratory chain that generates superoxide anion as a result of a single electron transfer to molecular oxygen. Superoxide anion and hydrogen peroxide, derived from the former by superoxide dismutase, are precursor of hydroxyl radical through the participation of transition metals. Glutathione (GSH) in mitochondria is the only defense available to metabolize hydrogen peroxide. A small fraction of the total cellular GSH pool is sequestered in mitochondria by the action of a carrier that transports GSH from the cytosol to the mitochondrial matrix. Mitochondria are not only one of the main cellular sources of ROS, they also are a key target of ROS. Mitochondria are subcellular targets of cytokines, especially tumor necrosis factor (TNF); depletion of GSH in this organelle renders the cell more susceptible to oxidative stress originating in mitochondria. Ceramide generated during TNF signaling leads to increased production of ROS in mitochondria. Chronic ethanol-fed hepatocytes are selectively depleted of GSH in mitochondria due to a defective operation of the carrier responsible for transport of GSH from the cytosol into the mitochondrial matrix. Under these conditions, limitation of the mitochondrial GSH pool represents a critical contributory factor that sensitizes alcoholic hepatocytes to the prooxidant effects of cytokines and prooxidants generated by oxidative metabolism of ethanol. S-adenosyl-L-methionine prevents development of the ethanol-induced defect. The mitochondrial GSH carrier has been functionally expressed in Xenopus laevis oocytes microinjected with mRNA from rat liver. This critical carrier displays functional characteristics distinct from other plasma membrane GSH carriers, such as its ATP dependency, inhibitor specificity, and the size class of mRNA that encode the corresponding carrier, suggesting that the mitochondrial carrier of GSH is a gene product distinct from the plasma membrane transporters.
Biosynthesis of mucins (MUC2-6) along the longitudinal axis of the human gastrointestinal tract
Authors: Van Klinken B. J. , Dekker J. , Buller H. A. , de Bolos C. , Einerhand A. W.
Published: December 2017

Little is known about the biosynthesis of mucin molecules in humans. Our aim was to examine the mucin biosynthesis (MUC2-6) along the longitudinal axis of the healthy human gastrointestinal tract. Biopsies of human stomach and small and large intestine were metabolically labeled with 35S-labeled amino acids, [35S]sulfate, or[3H]galactose, immunoprecipitated with antibodies against MUC2-6, and analyzed by reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), MUC5AC [apparent molecular weight (M(r)) 500,000] and MUC6 (apparent M(r) 400,000) were detected in the stomach but not in the small or large intestine, MUC3 (apparent M(r) 550,000) was detected in duodenum and jejunum, MUC2 (apparent M(r)600,000) was detected throughout the small and large intestine, and MUC4 (apparent M(r) > 900,000) was detected predominantly in the large intestine. Interestingly, some individuals displayed double bands of MUC2 and MUC3 precursors, suggesting allelic variation within the respective genes. Between small and large intestine mature secreted MUC2 showed differences in mobility on SDS-PAGE, suggesting differences in glycosylation. Each of the MUC2, MUC3, MUC4, MUC5AC, and MUC6 precursors could be distinguished electrophoretically, and each showed region-specific expression along the gastrointestinal tract.
Exogenous xanthine promotes neutrophil adherence to cultured endothelial cells
Authors: Ichikawa H. , Wolf R. E. , Aw T. Y. , Ohno N. , Coe L. , Granger D. N. , Yoshikawa T. , Alexander J. S.
Published: December 2017

Oxidants generated by endothelial xanthine oxidase (XO) can help trigger free radical-mediated tissue injury. An important event in oxidant-mediated tissue injury is neutrophil-endothelial adhesion. Although activation of endothelial XO increases adhesion, little is known about xanthine in the adhesive effect of XO. This study examined administered xanthine on the adhesion of neutrophils. Endothelial [human umbilical vein endothelial cells (HUVEC)] monolayers were exposed to xanthine (15 min), and neutrophils were allowed to adhere to HUVEC in an adhesion assay. Adhesion was dose dependently increased by xanthine (3-100 microM). Either catalase (1,000 U/ml), oxypurinol (XO inhibitor; 100 microM), or platelet-activating factor (PAF) receptor antagonist (WEB 2086; 10 microM) reduced neutrophil adhesion. Superoxide dismutase (1,000 U/ml) had no effect. Pretreatment of HUVEC with 50 microM tungsten also blocked xanthine-induced adherence. Adhesion was also inhibited by preincubation with 100 U/ml heparin. Finally, anti-P-selectin antibody (PB1.3; 20 micrograms/ml) attenuated adhesion. Our results indicate that xanthine may promote neutrophil-endothelial adhesion via a hydrogen peroxide- and PAF-mediated P-selectin expression.
Protective action of gastrin-17 against alcohol-induced gastric injury in the rat: role in mucosal defense
Authors: Mercer D. W. , Cross J. M. , Smith G. S. , Miller T. A.
Published: December 2017

Exogenous cholecystokinin (CCK) or exposure of the stomach to the mild irritant 25% ethanol can prevent gastric injury. Ingestion of ethanol also elicits the release of CCK as well as gastrin, which is structurally similar to CCK. This study was undertaken in conscious rats to examine the gastroprotective actions of gastrin and to assess the effect of CCK-gastrin receptor blockade on adaptive cytoprotection with ethanol as the mild irritant. Intravenous (1-25 pmol/kg) administration of gastrin-17 dose dependently increased gastric mucosal blood flow (laser Doppler) and reduced gastric injury caused by 1 ml of orally administered acidified ethanol (150 mM HCl-50% ethanol). Similar gastroprotection was achieved with the gastrin secretagogue 5% peptone (1 ml orogastrically). The gastroprotective capabilities of gastrin-17 were attenuated by the type B CCK (gastrin) receptor antagonist L-365,260 (12.5-25 mg/kg i.p.) and by capsaicin desensitization (125 mg/kg s.c.). CCK octapeptide (5 nmol/kg i.v.)-induced protection was reversed by the type A CCK receptor antagonist MK-329 (1 mg/kg i.p.). Neither receptor antagonist, alone or in combination, reversed the protective effects of the mild irritant 25% ethanol (1 ml orogastrically). Thus, whereas gastrin may play a role in gastric mucosal defense, neither CCK nor gastrin appears to participate in the phenomenon of adaptive cytoprotection.
Role of sensory afferents in the myoelectric response to acute enteric inflammation in the rabbit
Authors: Shea-Donohue T. , Goldhill J. M. , Montcalm-Mazzilli E. , Colleton C. , Pineiro-Carrero V. M. , Sjogren R. W.
Published: December 2017

The role of sensory afferents in inflammation-induced alterations in myoelectric activity in vivo was investigated in the rabbit small intestine. Isolated ileal loops were implanted with serosal electrodes and exposed to ricin or vehicle after pretreatment with 125 mg/kg of subcutaneous (125 mg over 3 days) or intraluminal (640 microM) capsaicin. After 5 h of myoelectric recording, the loops were prepared for histology and for ex vivo generation of eicosanoids. Capsaicin exacerbated mucosal damage after exposure to ricin but did not alter neutrophil infiltration. Subcutaneous capsaicin alone elevated slow-wave frequency and spike events and transiently suppressed the myoelectric response to ricin. In contrast, intraluminal capsaicin alone did not alter myoelectric activity but produced a sustained inhibition of the response to ricin. Eicosanoid production was unchanged by capsaicin alone. Intraluminal capsaicin blocked increases in leukotriene C4 and prostaglandin E2 during inflammation, an effect that paralleled its inhibition of myoelectric activity. Thus the contribution of sensory afferents to altered motility during acute ileitis involves the release of mucosal inflammatory mediators that influence neural control of smooth muscle.
Tapeworm infection decreases intestinal transit and enteric aerobic bacterial populations
Authors: Dwinell M. B. , Bass P. , Schaefer D. M. , Oaks J. A.
Published: December 2017

Intestinal myoelectric patterns in rats are altered after chronic luminal infection with the tapeworm Hymenolepis diminuta. This study evaluates whether these altered patterns were associated with changes in intestinal fluid transit and endogenous enteric microbe levels. Luminal transit, measured throughout the small intestine during the interdigestive state, was significantly decreased during tapeworm infection. Reduced transit was regional, occurring in the same location as that of the tapeworm and maximal myoelectric alterations. In other experimental systems, aerobic and anaerobic bacterial overgrowth is associated with decreased transit; however, reduced transit during tapeworm infection was unexpectedly associated with decreased numbers of aerobic bacteria, whereas anaerobic bacterial populations remained unchanged. The lack of overgrowing endogenous microflora suggests that overgrowth is not responsible for tapeworm-stimulated alterations in host myoelectric patterns. We speculate that a tapeworm secretion could be responsible for both transit and motility changes while delayed intestinal transit could prevent tapeworm expulsion, aid the tapeworms' migration, and contribute to the digestion and absorption of nutrients by hosts and/or parasites.
Glucagon-like peptide-1 inhibits gastric emptying via vagal afferent-mediated central mechanisms
Authors: I˙meryüz Neşe , Yeğen Berrak Ç. , Bozkurt Ayhan , Coşkun Tamer , Villanueva-Peñacarrillo Maria L. , Ulusoy Nefise B.
Published: December 2017

Exogenous administration of glucagon-like peptide-1-(7—36) amide (GLP-1), an insulinotropic hormone, inhibits gastric emptying and acid secretion in humans. The role of GLP-1 as a regulator of gastric function is elusive. In gastric fistula rats, vagal afferent denervation and peripheral administration of the GLP-1 receptor antagonist exendin(9—39) amide enhanced emptying of a glucose meal, whereas intracerebroventricular exendin was ineffective. The rate of saline emptying was attenuated by peripheral as well as by central administration of GLP-1, and pretreatment with exendin by the respective routes reversed the inhibition by GLP-1. Vagal afferent denervation abolished the central and peripheral action of GLP-1 on gastric emptying. Neither peripheral cholinergic nor adrenergic blockade altered the delay of methyl cellulose meal emptying by intracisternal GLP-1 injection. Acid secretion in conscious pylorus-ligated rats was inhibited by intracisternal GLP-1 administration, whereas systemic GLP-1 was ineffective. These results support the notion that GLP-1 receptors participate in the central and peripheral regulation of gastric function. Furthermore, vagal afferent nerves mediate the inhibitory action of GLP-1 on gastric motor function. GLP-1 may be a candidate brain-gut peptide that acts as a physiological modulator of gastric function.
α2-Adrenergic modulation of colonic tone during hyperventilation
Authors: Bharucha Adil E. , Novak Vera , Camilleri Michael , Zinsmeister Alan R. , Hanson Russell B. , Low Phillip A.
Published: December 2017

Our aims were to assess the role of adrenergic modulation in the hyperventilation-induced increase in colonic tone. Of 40 healthy volunteers, 12 received placebo (saline) and the remaining 28 received either clonidine, yohimbine, phenylephrine, or ritodrine. Time-frequency mapping of heart rate based on Wigner distribution assessed variations in parasympathetic and sympathetic activity during hyperventilation. Tone in the descending colon was recorded by a barostat balloon before, during, and after 5 min of hyperventilation. Heart rate spectral analysis suggested diminished sympathetic and vagal activity during hyperventilation and increased sympathetic and vagal activity after hyperventilation. Adrenergic agents influenced ( P = 0.01) the tonic response after, but not during, hyperventilation. Yohimbine reduced the increment in colonic tone after hyperventilation compared with saline ( P < 0.05) and clonidine ( P = 0.002); phenylephrine and ritodrine had no effects. Different mechanisms modulate the increase in colonic tone during and after hyperventilation. Yohimbine attenuates the increase in colonic tone after hyperventilation probably by enhancing inhibitory sympathetic input to the colon.
Guinea pig pancreatic neurons: morphology, neurochemistry, electrical properties, and response to 5-HT
Authors: Liu Min-Tsai , Kirchgessner Annette L.
Published: December 2017

The morphology, neurochemistry, and electrical properties of guinea pig pancreatic neurons were determined. The majority of neurons expressed choline acetyltransferase (ChAT) immunoreactivity; however, ChAT-negative neurons were also found. Both cholinergic and noncholinergic neurons expressed nitric oxide synthase (NOS) immunoreactivity. Three types of pancreatic neurons were distinguished. Phasic neurons fired action potentials (APs) at the onset of depolarizing current pulse, tonic neurons spiked throughout the duration of a suprathreshold depolarizing pulse, and APs could not be generated in nonspiking neurons, even though they did receive synaptic input. APs were tetrodotoxin sensitive, and all types of neurons received fast and slow excitatory postsynaptic potentials (EPSPs). Fast EPSPs had cholinergic and noncholinergic components. The majority of pancreatic neurons appeared to innervate the acini. NOS- and/or neuropeptide Y-immunoreactive phasic and tonic neurons were found. Microejection of 5-hydroxytryptamine (5-HT) caused a slow depolarization that was inhibited by the 5-HT1P antagonist N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide and mimicked by the 5-HT1Pagonist 6-hydroxyindalpine. A pancreatic 5-HT transporter was located, and inhibition of 5-HT uptake by fluoxetine blocked slow EPSPs in 5-HT-responsive neurons by receptor desensitization.
IL-8 release and neutrophil activation byClostridium difficiletoxin-exposed human monocytes
Authors: Linevsky Joanne K. , Pothoulakis Charalabos , Keates Sarah , Warny Michel , Keates Andrew C. , Lamont J. Thomas , Kelly Ciarán P.
Published: December 2017

Neutrophil infiltration is central to the pathogenesis of Clostridium difficiletoxin A-induced enterocolitis. This study examines whether monocyte activation by C. difficile toxins is instrumental in initiating neutrophil activation and recruitment. Human monocytes were exposed to low concentrations of highly purified C. difficile toxins, and the conditioned media were harvested for cytokine and functional assays. Monocytes exposed to C. difficiletoxin A (10−10M) or toxin B (10−12M) released 100 and 20 times basal levels, respectively, of the neutrophil chemoattractant interleukin-8 (IL-8). Reverse transcriptase-polymerase chain reaction demonstrated a marked increase in IL-8 mRNA expression by monocytes 3 h after toxin exposure. Conditioned media from toxin A- and toxin B-treated monocytes stimulated neutrophil migration (324 and 245% of control, respectively). This effect was completely blocked by IL-8 antiserum. These media also upregulated neutrophil CD11b/CD18 and endothelial cell intercellular adhesion molecule-1 expression. C. difficile toxins, at low concentrations, potently activate monocytes to release factors, including IL-8, that facilitate neutrophil extravasation and tissue infiltration. Our findings indicate a major role for toxin-mediated monocyte and macrophage activation in C. difficile colitis.
Relationships between cecoileal reflux and ileal motor patterns in conscious pigs
Authors: Cuche G. , Malbert C. H.
Published: December 2017

Ileal infusion of cecocolonic contents, used to mimick reflux, enhanced terminal ileal motility, increasing the frequencies of prolonged propagated contractions (PPC) and discrete clustered contractions (DCC). Because the reflux rate in dogs and humans is marginal, the relationship of these motor patterns to reflux remained putative. In six conscious pigs, the ileal pH, used to indicate reflux event, was measured 10 and 5 cm proximal to the ileocecal sphincter (ICS). Ileal motility was evaluated with three strain gauges 15, 10, and 5 cm proximal to the ICS. Ileal pH dips were observed about eight times per hour in the fasting or fed state, and 46% of the pH dips were preceded by a retrograde contraction. During pH dips, frequency of ileal contractions not classified as PPC or DCC was significantly increased. Of the PPC 52% occurred immediately after the start of the dip and might act as a clearance mechanism because dips associated with PPC were of smaller amplitude and duration than those not associated with PPC. Most DCC also occurred during pH dips but their delay to the onset of the dip was longer. The pig presents frequent cecoileal reflux events associated with ileal motor patterns, some of them might facilitate reflux, whereas others act as a clearance mechanism.
Expression of intrinsic factor and pepsinogen in the rat stomach identifies a subset of parietal cells
Authors: Shao J.-S. , Schepp W. , Alpers D. H.
Published: December 2017

Morphological and functional heterogeneity of parietal cells has been thought to be due to different maturation positions within the gastric gland. Morphodynamic studies have shown that 2% of parietal cells in mice derive from a pre-neck (chief) cell precursor. Intrinsic factor (IF) and pepsinogen, markers of rat chief cells, were used to determine if these proteins identified a subset of parietal cells that might reflect origin from the pre-neck cell lineage. The zymogenic region of the rat stomach and gradient-isolated fractions enriched in parietal and chief cells were fixed in 10% buffered Formalin or in Bouin’s solution. Immunostaining was performed using indirect immunoperoxidase histochemistry and double-labeled immunofluorescence with antibodies raised against human IF, pepsinogen II, and H+-K+-adenosinetriphosphatase (H+-K+-ATPase). In intact tissue, parietal (H+-K+-ATPase-positive) cells were found starting at the upper edge of the isthmus, but parietal cells positive for IF and pepsinogen were only found from just below the isthmus and neck region to the base of the gastric gland. Three to four percent of isolated parietal cells were positive for these ectopic markers. This subset of cells was also positive for H+-K+-ATPase. Thus products of rat chief cells are expressed in a subset of parietal cells. The percentage of positive cells is similar to that predicted to be derived from the pre-neck (chief) precursor lineage in the mouse. The distribution of these cells to the lower neck and base of the gland suggests that the expression of chief cell products is consistent with either predetermination by lineage or parietal cell maturation or with both processes.
Effect of intracisternal thyrotropin-releasing hormone on hepatic blood flow in rats
Authors: Tamori Keisuke , Yoneda Masashi , Nakamura Kimihide , Makino Isao
Published: December 2017

Central neuropeptides play a role in many physiological regulatory processes through the autonomic nervous system. Thyrotropin-releasing hormone (TRH) is distributed in the central nervous system and acts as a neurotransmitter to regulate gastric functions through vagal-muscarinic pathways. The central effect of the TRH analog on hepatic blood flow was investigated in urethan-anesthetized rats. Hepatic blood flow was determined by the hydrogen gas clearance technique. Intracisternal injection of the stable TRH analog RX-77368 (5–100 ng) dose dependently increased hepatic blood flow with peak response at 15 min after the peptide was administered (net change from basal for vehicle and 5, 10, 100, and 500 ng RX-77368 was 2.0 ± 0.2, 8.9 ± 0.8, 19.4 ± 2.6, 32.6 ± 3.3, and 28.5 ± 6.8 ml ⋅ min−1 ⋅ 100 g−1, respectively), and this stimulatory effect returned to baseline at 90 min. The stimulation of hepatic blood flow by the intracisternally administered TRH analog was abolished by atropine methyl nitrate (0.15 mg/kg ip), indomethacin (5 mg/kg ip), N G-nitro-l-arginine methyl ester (10 mg/kg iv), and hepatic branch vagotomy but not by cervical spinal cord transection (C6 level). Intravenous injection of RX-77368 did not have any effect on hepatic blood flow. These results indicate that TRH acts in the central nervous system to stimulate hepatic blood flow through vagal-muscarinic and indomethacin- and nitric oxide-dependent pathways.
DNA methylation contributes to expression of the human neurotensin/neuromedin N gene
Authors: Dong Zizheng , Wang Xiaofu , Zhao Qingzheng , Townsend Courtney M. , Evers B. Mark
Published: December 2017

The gut and liver share a common embryological origin. The gene encoding the gut hormone neurotensin/neuromedin N (NT/N) is expressed in the adult small bowel, and NT/N is transiently expressed in the fetal liver, suppressed in the adult liver, and reexpressed in certain liver cancers. In our present study, we found that the NT/N gene was expressed at high levels in the human hepatoma cell line Hep 3B but was not expressed in Hep G2 cells. To further determine the mechanisms regulating NT/N expression, we performed Southern blotting and gene cloning techniques. Neither alteration nor mutation of the NT/N gene was responsible for this differential NT/N expression pattern. Human NT/N promoter constructs were transfected into either Hep 3B or Hep G2. Both cell lines supported NT/N transcription, indicating that the absence of NT/N expression in Hep G2 cells was due to mechanisms other than the absence of positive transcription factors. The role of DNA methylation was next assessed. Methylation of NT/N promoter constructs in vitro resulted in a 67-fold reduction in promoter activity, whereas treatment with the demethylating agent 5-azacytidine induced NT/N expression in Hep G2 cells, thus suggesting that DNA methylation plays a role in the expression of the gut endocrine gene NT/N. Defining the mechanisms regulating NT/N expression in these hepatic-derived cell lines will provide not only a better understanding of cell-specific and developmental regulation of a gut endocrine gene but also possible insight into liver cell lineage patterns and the derivation of certain hepatocellular cancers.
Hypoxia and CYP1A1 induction-dependent regulation of proteins involved in glucose utilization in Caco-2 cells
Authors: Carrière Véronique , Rodolosse Annie , Lacasa Michel , Cambier Danièle , Zweibaum Alain , Rousset Monique
Published: December 2017

Although induction of cytochrome P-450 1A1 (CYP1A1) in the Caco-2 clone TC7 alters glucose utilization and modifies the expression of sucrase-isomaltase (SI) and hexose transporters, nothing is known of the events that control these effects. In this study, we analyzed the effects of β-naphthoflavone (β-NF) and hypoxia on these parameters and expression of key enzymes of glucose metabolism. Both β-NF and hypoxia induce similar changes: 1) induction of CYP1A1 mRNA; 2) increased glucose consumption and lactic acid production and lower glycogen content; 3) downregulation of SI and upregulation of GLUT1 mRNAs; 4) downregulation of fructose-1,6-bisphosphatase and pyruvate kinase mRNAs and upregulation of phospho enolpyruvate carboxykinase, pyruvate dehydrogenase, lactate dehydrogenase, and phosphofructokinase mRNAs; and 5) upregulation of c- fos and c- jun mRNAs. Although addition of inhibitors of CYP1A1 catalytic activity to β-NF-treated cells totally inhibits the enzyme activity, it does not modify CYP1A1 mRNA response and associated effects, thus excluding a direct role for the enzyme per se. These results point to a possible physiological implication of the signal-transduction pathway responsible for CYP1A1 induction.
Gastric emptying flow curves separated from carbon-labeled octanoic acid breath test results
Authors: Maes B. D. , Mys G. , Geypens B. J. , Evenepoel P. , Ghoos Y. F. , Rutgeerts P. J.
Published: December 2017

Recently, we developed the [13/14C]octanoic acid breath test to measure gastric emptying of solids. Although the method has been validated extensively, absorption, metabolism, and excretion of the label in the breath need to be corrected for. In this study a mathematical model was developed that allows for 1) separation of the global CO2 excretion after ingestion of the labeled test meal into the emptying rate of the labeled test meal from mouth to pylorus and the postgastric processing of absorption, metabolism, and excretion of the label, and 2) numerical calculation of the half-emptying time and lag phase of the emptied meal. The model was applied to the gastric emptying results obtained by simultaneous scintigraphic and breath test measurements. An excellent correlation was found between the gastric half-emptying time ( r = 0.98) and lag phase ( r = 0.85) determined scintigraphically and via breath test. There was also a good agreement between the two methods [mean values and confidence limits for differences: t ½= 10 min (−20 to 41) and t lag = −3 min (−39 to 34)]. Moreover, the separated gastric emptying curves, lacking the influence of postgastric processing of the label, showed real patterns of gastric outflow, which changes from moment to moment.
CD4+T cells mediate superantigen-induced abnormalities in murine jejunal ion transport
Authors: McKay Derek M. , Benjamin Michelle A. , Lu Jun
Published: December 2017

The immunomodulatory properties of bacterial superantigens (SAgs) have been defined, yet comparatively little is known of how SAgs may affect enteric physiology. Staphylococcus aureus enterotoxin B (SEB) was used to examine the ability of SAgs to alter epithelial ion transport. BALB/c mice, severe combined immunodeficient (SCID, lack T cells) mice, or SCID mice reconstituted with lymphocytes or CD4+T cells received SEB intraperitoneally, and jejunal segments were examined in Ussing chambers; controls received saline only. Baseline short-circuit current ( Isc, indicates net ion transport) and Iscresponses evoked by electrical nerve stimulation, histamine, carbachol, or forskolin were recorded. Serum levels of interleukin-2 (IL-2) and interferon-γ (IFN-γ) were measured. SEB-treated BALB/c mice showed elevated serum IL-2 and IFN-γ levels, and jejunal segments displayed a time- and dose-dependent increase in baseline Isccompared with controls. Conversely, evoked ion secretion was selectively reduced in jejunum from SEB-treated mice. Elevated cytokine levels and changes in jejunal Iscwere not observed in SEB-treated SCID mice. In contrast, SCID mice reconstituted with T cells were responsive to SEB challenge as shown by increased cytokine production and altered jejunal Iscresponses that were similar to those observed in jejunum from SEB-treated BALB/c mice. We conclude that exposure to a model bacterial SAg causes distinct changes in epithelial physiology and that these events can be mediated by CD4+T cells.