bluuebunny/crossref_metadata_2025 huggingface dataset:
Endothelin-1 production by hepatic endothelial cells: characterization and augmentation by endotoxin exposure
Authors: Eakes A. T. , Howard K. M. , Miller J. E. , Olson M. S.
Published: December 2017

Activation of endothelin (ET) receptors in the liver causes vasoconstriction, glucose production, and lipid and peptide mediator synthesis. In the intact rat, a bolus infusion of endotoxin into a mesenteric vein served as an acute exposure model of endotoxemia. In response to this challenge, a ninefold increase in hepatic ET-1 mRNA occurred within 3 h. The plasma level of immunoreactive ET-1 (irET-1) increased correspondingly by 8.5-fold within 6 h. ET-1 mRNA levels in liver endothelial cells (EC) isolated from livers of endotoxin-treated rats at various times after endotoxin challenge showed a more gradual increase. Northern blot analyses of the major liver cell types demonstrated that ET-1 mRNA was most abundant in the EC. The present results document a significant increase in the circulating level of irET-1 during episodes of endotoxemia. The increased hepatic ET-1 production in response to endotoxin infusion suggests that ET-1 produced in the liver could make a significant contribution to the plasma irET-1 and may be an important component in the hepatic responses to systemic trauma.
Different effect of cold storage and rewarming on three pH regulating transporters in isolated rat hepatocytes
Authors: Forestal D. A. , Haimovici J. , Haddad P.
Published: December 2017

Disturbances in hepatic pH homeostasis are thought to participate in the functional damage to liver grafts caused by the cold preservation and warm reperfusion necessitated by transplantation surgery. We have used an in vitro model of isolated rat hepatocytes suspended in cold University of Wisconsin (UW) solution and subsequently cultured at 37 degrees C to evaluate liver cell pH regulatory mechanisms after cold preservation and rewarming. Cells were kept for up to 72 h in cold UW solution, and at 24-h intervals intracellular pH (pHi) was measured after 60-90 min of warm culture by cytofluorometry using the fluorochrome 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. When challenged with an alkaline load by isohydric HCO(3)(-)-CO(2) steps, hepatocytes exhibited similar maximal pH(i) values and recovered at the same rate, irrespective of cold storage time, indicating that Cl-/HCO(3)- exchange activity is quite resistant to hypothermic storage and subsequent rewarming. In parallel studies, cells were subjected to an acid load by the NH4Cl pulse technique in bicarbonate buffer containing 50 microM ethylisopropylamiloride to block Na+/H+ exchange. Despite similar nadir pH(i) (lowest pH(i) values due to acid load), the subsequent pH(i) recovery rate that reflects Na+-(HCO(3)-)n cotransport activity was increased significantly after hypothermic preservation. Hepatocytes were also perfused with a bicarbonate-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, and Na+/H+ exchange activity was evaluated using the same acid load protocol. Although cells always exhibited similar steady-state initial pH(i) and nadir, the rate of pH(i) recovery decreased significantly as a function of cold storage time in UW solution. Finally, intracellular buffering capacity was calculated from the sudden pH(i) changes induced by HCO(3)(-)-CO(2) steps or NH4Cl pulses and was found to remain stable throughout the 72 h of cold preservation. Therefore, the results strongly suggest that cold preservation and rewarming disturb hepatocellular pH regulatory mechanisms by attenuating Na+/H+ exchange and increasing Na+-(HCO(3)-)n cotransport, whereas Cl-/HCO(3)- exchange is not affected.
Effect of short-chain fatty acids on paracellular permeability in Caco-2 intestinal epithelium model
Authors: Mariadason J. M. , Barkla D. H. , Gibson P. R.
Published: December 2017

Control of paracellular permeability in the colonic epithelium is fundamental to its functional competence. This study examines the relationship between physiologically relevant short-chain fatty acids (SCFAs) and paracellular permeability using the Caco-2 cell line model. Butyrate induced a concentration-dependent, reversible increase in transepithelial resistance (TER) that was maximal after 72 h. Butyrate (2 mM) increased TER by 299 +/- 69% (mean +/- SE; n = 5; P < 0.05; t-test) and reduced mannitol flux to 52 +/- 11% (P < 0.05) of control. The effect of butyrate was dependent on protein synthesis and gene transcription but not dependent on its oxidation or activation of adenosine 3',5'-cyclic monophosphate. The other SCFAs, propionate and acetate, also induced a concentration-dependent increase in TER. The effect of butyrate paralleled changes in cellular differentiation, because alkaline phosphatase activity, carcinoembryonic antigen expression, and dome formation were increased. Furthermore, other differentiating agents (dimethyl sulfoxide and retinoic acid) also increased TER. Thus SCFAs reduce paracellular permeability in the Caco-2 cell line, possibly by promotion of a more differentiated phenotype. If such an effect occurs in vivo, it may have ramifications for the biology and pathobiology of colonic mucosa.
Nitric oxide and gallbladder motility in prairie dogs
Authors: Salomons H. , Keaveny A. P. , Henihan R. , Offner G. , Sengupta A. , Lamorte W. W. , Afdhal N. H.
Published: December 2017

In this study we evaluated the role of nitric oxide (NO) on gallbladder motility in the normal prairie dog by 1) immunohistochemistry, 2) an enzymatic assay for NO synthase (NOS), and 3) an in vivo model to measure whole gallbladder tone and contractility. NOS was localized to gallbladder mucosal cells by NADPH-diaphorase and polyclonal antibodies to a constitutive brain NOS. Gallbladder mucosal homogenates demonstrated total NOS activity in the range of 578 +/- 115 pmol x mg protein(-1) x 30 min(-1). Blockade of NOS activity in vivo using N(omega)-nitro-L-arginine methyl ester resulted in an up to 80% increase in gallbladder tone from basal. A 40% increase in tone was seen with methylene blue, suggesting that tone was maintained by both NO activation of guanylate cyclase and possibly direct effects on Ca2+ channels. An exogenous nitrosothiol, S-nitroso-N-acetyl-cysteine, abolished cholecystokinin (CCK) octapeptide and bethanechol-stimulated gallbladder contraction. We conclude that the prairie dog gallbladder contains constitutive NOS and synthesizes NO, which is important for the maintenance of basal gallbladder tone and is an inhibitor of the contractile response of the gallbladder to agonists such as CCK and bethanechol.
Mechanisms of CCK regulation of monitor peptide mRNA expression in pancreatic acinar AR42J cells
Authors: Kinouchi T. , Tsuzuki S. , Minami C. , Hayashi Y. , Sugimoto E. , Fushiki T.
Published: December 2017

We explored the mechanism(s) by which cholecystokinin (CCK) stimulation of AR42J rat pancreatoma cells results in increased mRNA expression of a CCK-releasing peptide [monitor peptide (MP)]. With the use of a newly established reverse transcription-polymerase chain reaction assay system, CCK was shown to increase the level of MP mRNA by about ninefold. When protein synthesis was blocked by addition of cycloheximide, the MP mRNA level remained unchanged in the presence of CCK. Inhibition of transcription with actinomycin D resulted in a half-life for MP mRNA of approximately 17 h, and this rate remained unchanged after CCK treatment, suggesting that CCK may regulate the MP mRNA level by influencing gene transcription. A-23187, bombesin, substance P, and carbachol increased the MP mRNA level. CoCl(2) abolished actions of both CCK and A-23187 on MP mRNA expression. Dibutyryl-adenosine 3',5'-cyclic monophosphate, forskolin, secretin, and vasoactive intestinal polypeptide had no effect on MP mRNA expression. 12-O-tetradecanoylphorbol-13-acetate and phorbol 12,13-dibutyrate also failed to increase MP mRNA. It was therefore proposed that CCK stimulates MP mRNA expression of AR42J cells in a Ca2+-dependent and protein kinase C-independent manner.
Cranial nerve modulation of human cortical swallowing motor pathways
Authors: Hamdy S. , Aziz Q. , Rothwell J. C. , Hobson A. , Barlow J. , Thompson D. G.
Published: December 2017

Animal data indicate that cortical swallowing pathways can be modulated by cranial nerve afferent stimulation. We therefore studied the effects of human trigeminal and vagal nerve excitation on the corticofugal pathways to the oropharynx and esophagus, using electromagnetic stimulation. Unilateral stimulation of either the trigeminal or vagus nerve evoked two distinct reflex electromyographic responses in the pharynx and esophagus, an early response (latency range 19-30 ms) and a late response (latency range 42-72 ms). In the mylohyoid muscles, however, only a single response was seen (latency range 36-64 ms). Cortical stimulation also evoked electromyographic responses in the mylohyoid muscles, pharynx, and esophagus, with latencies of 8.5 +/- 0.3, 9.3 +/- 0.3, and 10.1 +/- 0.4 ms, respectively. When either trigeminal or vagus nerve stimulation preceded cortical stimulation, the cortically evoked responses were facilitated, with maximal effects at interstimulation intervals of 30-200 ms for pharynx and esophagus (P < 0.02) and at interstimulation intervals of 50-100 ms for mylohyoid muscles (P < 0.05). Our results demonstrate that stimulation of human cranial nerve afferent fibers facilitates cortical swallowing motor pathways.
Nitric oxide attenuates and xanthine oxidase exaggerates lung damage-induced gut injury
Authors: Brooks E. C. , Mahr N. N. , Radisavljevic Z. , Jacobson E. D. , Terada L. S.
Published: December 2017

Aspirated gastric contents can evoke multiorgan failure. We hypothesized that secondary intestinal epithelial dysfunction after lung damage would be mediated by xanthine oxidase (XO) and antagonized by endogenous gut nitric oxide (NO). Isosmotic saline or HCl solutions were instilled intratracheally in anesthetized rats, and intestinal injury was assessed 190 min later by measuring the blood-to-lumen clearance of 51Cr-labeled EDTA (51Cr-EDTA clearance) and gut wall neutrophil population density. Intratracheal HCl increased 51Cr-EDTA clearance, and this transepithelial leak was attenuated by either systemic L-arginine or intraluminal NO and by chronic dietary pretreatment with allopurinol or sodium tungstate. Conversely, lung damage-induced gut leak was exaggerated by NO synthase inhibition or intravenous XO administration. Intratracheal HCl also increased intestinal wall neutrophil density and myeloperoxide activity. We conclude that two enzymatic systems involved in remote gut barrier dysfunction after endobronchial acidification are XO as mediator and NO synthase as antagonist.
Role of plasma vasopressin as a mediator of nausea and gastric slow wave dysrhythmias in motion sickness
Authors: Kim M. S. , Chey W. D. , Owyang C. , Hasler W. L.
Published: December 2017

The possible role of vasopressin in nausea and gastric dysrhythmias in motion sickness was tested by electrogastrography in 14 subjects during circular vection (60 degrees/s) and vasopressin infusion. Tachygastria was expressed as the signal percent >4.5 cycles/min. Vection evoked nausea scores of 2.6 +/- 0.2 (0 = none to 3 = severe) in 10 subjects with increases in tachygastric activity (15 +/- 2 to 45 +/- 3%) and plasma vasopressin (4.5 +/- 1.5 to 8.4 +/- 2.5 pg/ml) that were blocked by atropine but not indomethacin. Four asymptomatic subjects had no tachygastria or vasopressin release. Vasopressin at 0.2 U/min (plasma level = 322.1 +/- 10.3 pg/ml) evoked nausea (2.6 +/- 0.4) and increases in tachyarrhythmic activity (41 +/- 5%) that were blunted by atropine but not indomethacin. There were no differences in nausea or dysrhythmias with vasopressin infusion in subjects who noted nausea during vection versus those who did not. To conclude, vection evokes nausea, dysrhythmias, and vasopressin release in motion sickness-susceptible humans via cholinergic prostaglandin-independent pathways. Supraphysiological vasopressin infusions evoke nausea and dysrhythmias by similar pathways to equal degrees in motion sickness-susceptible and -resistant subjects. Thus central but not peripheral actions of vasopressin may contribute to nausea and slow wave disruption with vection. Blunting of both the release and action of vasopressin by atropine may explain its beneficial action in motion sickness.
Rhythmic oscillating complexes in gastrointestinal tract of chickens: a role for motilin
Authors: Rodriguez-Sinovas A. , Jimenez M. , De Clercq P. , Peeters T. L. , Vergara P.
Published: December 2017

Rhythmic oscillating complex (ROC) is a highly organized gastrointestinal motility pattern recently described in fasted avian species. ROCs show several high-speed aborad-propagated contractions that progressively change into others of orad direction. In addition, chickens show migrating motor complexes (MMC) in both fed and fasting states. Recently, motilin was isolated and characterized from chicken small intestine. Accordingly, the aim of this study was to learn whether chicken motilin might be involved in either ROC or MMC induction. Electromyographic recordings were obtained from different areas of the gastrointestinal tract of chickens while motilin was infused. The response to chicken motilin was dose dependent in both fed and fasted animals; a bolus of 4 x 10(-11) mol/kg (n = 5) did not modify the intestinal motor pattern, whereas 4 x 10(-10) and 4 x 10(-9) mol/kg (n = 5 each) induced a complete ROC pattern of 5.2 +/- 0.6 and 10.8 +/- 0.9 min, respectively. ROCs induced by chicken motilin presented exactly the same pattern as that described during a spontaneous ROC. Furthermore, motilin concentration in plasma, measured by radioimmunoassay, increased during a spontaneous ROC. This study suggests that chicken motilin triggers an ROC in chickens. The fact that plasma motilin levels increased during spontaneous ROC strongly suggests that motilin is involved in the induction of the ROC pattern. Motilin seems to play a different role in avian and mammalian species, because a phase III of the MMC was never induced by motilin infusion.
Effect of hyperglycemia on gastric acid secretion during the gastric phase of digestion
Authors: Lam W. F. , Masclee A. A. , Muller E. S. , Lamers C. B.
Published: December 2017

We have examined the effect of an acute stable hyperglycemia on gastric acid secretion during the gastric phase of digestion. Gastric acid output was measured with a recovery marker (phenol red) under basal conditions and after repeated intragastric instillation of a liquid meal in seven healthy subjects on two separate occasions: during normoglycemia (serum glucose, 15 mM). Premeal gastric acid output was significantly (P < 0.05) reduced during hyperglycemia compared with during normoglycemia (2.6 +/- 1.0 vs. 5.8 +/- 1.8 mmol/h). Intragastric meal-stimulated incremental acid output during hyperglycemia was significantly (P < 0.05) reduced compared with during normoglycemia (19 +/- 4 vs. 38 +/- 9 mmol/120 min). Meal-stimulated gastrin release during hyperglycemia was significantly (P < 0.05) reduced compared with that during normoglycemia (4.9 +/- 1.3 vs. 6.6 +/- 1.6 micrograms.1(-1).120 min-1). The intragastric meal induced significant (P < 0.05) increases in pancreatic polypeptide concentrations only during normoglycemia. During hyperglycemia, recovery rates of gastric contents were significantly (P < 0.05) increased compared with during normoglycemia, both before (81 +/- 4 vs. 71 +/- 6%) and after (72 +/- 4 vs. 57 +/- 4%) meal ingestion, pointing to delayed gastric emptying of liquids during hyperglycemia. In conclusion, 1) gastric acid secretion under unstimulated conditions and during the gastric phase of digestion is reduced during hyperglycemia; 2) meal-stimulated gastrin release is significantly reduced during hyperglycemia; 3) the reduction in meal-stimulated acid output is correlated with the reduction in gastrin releases; and 4) pancreatic polypeptide secretion is significantly reduced during hyperglycemia, pointing to impaired vagal cholinergic tone.
Gastric epithelial morphogenesis in normal and transgenic mice
Authors: Karam S. M. , Li Q. , Gordon J. I.
Published: December 2017

The epithelium located in the corpus of the adult mouse stomach forms mucosal invaginations known as gastric units. Gastric units are populated by members of the pit, parietal, and neck-zymogenic cell lineages all of which are derived from multipotent stem cells. Gastric unit morphogenesis was examined in normal embryonic day 18 (E18) to postnatal day 28 (P28) FVB/N mice with electron microscopy and multilabel immunohistochemistry. E18 units appear as short, solid infoldings (primordial buds), 92% of whose cells represent pit, parietal, and neck cell precursors. Although the total number of cells per bud does not change from P1 to P7, immature cells decrease to 22% as differentiated pit, neck, and parietal cells appear. From P7 to P15, lineage precursors and their differentiated progeny increase and buds elongate. Between P15 and P21 the multipotent stem cell and its descendants are assembled into a distinct proliferative zone (isthmus) located in the midportion of each unit, and cellular migration-differentiation programs become compartmentalized. To examine the role of parietal cells in regulating gastric unit morphogenesis, nucleotides -1035 to +24 of the mouse H(+)-K(+)-adenosinetriphosphatase beta-subunit gene were used to express simian virus 40 large T antigen (SV40 TAg) exclusively in this lineage. SV40 TAg amplified the normally rare pre-parietal cell and disclosed a pre-parietal cell precursor. Pre-parietal cells and their precursors were the predominant cells in E18-P1 transgenic buds. At later stages of development (P1-P28) there was a block in differentiation of pre-parietal to mature parietal cells, a decrease in neck cells, and a marked depletion of zymogenic cells. These findings suggest that members of the parietal cell lineage are the source of instructions that affect the neck-zymogenic cell lineage, even before the gastric unit is compartmentalized into its anatomically distinct pit, isthmus, neck, and base regions.
Experimental esophagitis affects intracellular calcium stores in the cat lower esophageal sphincter
Authors: Rich H. , Sohn U. D. , Behar J. , Kim N. , Biancani P.
Published: December 2017

We previously showed that lower esophageal spincter (LES) tone depends on spontaneous production of inositol 1,4,5-trisphosphate (IP3) and release of intracellular Ca2+ and that acute experimental esophagitis reduces LES tone and IP3 production, suggesting damage to mechanisms responsible for release of Ca2+ from intracellular stores. In the present investigation, we examined the possibility that mechanisms responsible for Ca2+ storage or uptake may also be damaged. LES circular muscle cells were isolated by enzymatic digestion. Contraction was measured in response to IP3 and thapsigargin, which enhances release of Ca2+ from intracellular stores, and in response to calmodulin and to diacylglycerol. In addition, normal cells were incubated in thapsigargin to assess the effect of depletion of intracellular Ca2+ stores on contractile response. Contraction in response to IP3 and thapsigargin was reduced in experimental esophagitis, but contraction in response to calmodulin or diacylglycerol was not. Acetylcholine (ACh)-induced contraction of normal cells was inhibited by the calmodulin antagonist CGS-9343B but not by 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine dihydrochloride (H-7). In contrast, in cells from animals with esophagitis or in thapsigargin-treated cells from normal animals, ACh-induced contraction was inhibited by H-7 and not by CGS-9343B. We conclude that experimental esophagitis may damage intracellular Ca2+ stores in the LES and change the intracellular contractile pathways activated by ACh from calmodulin dependent in normal cells to protein kinase C dependent in esophagitis.
Mechanisms mediating gastric hyperemic and acid responses to central TRH analog at a cytoprotective dose
Authors: Kiraly A. , Suto G. , Guth P. H. , Tache Y.
Published: December 2017

Gastric hyperemic and acid responses to the stable thyrotropin-releasing hormone (TRH) analog RX-77368 injected intracisternally at a cytoprotective dose were investigated, as well as the underlying mechanisms of the responses. Gastric acid secretion (GAS), mucosal blood flow (GMBF; measured by the hydrogen gas clearance technique), and mucosal vascular resistance (GMVR) and mean arterial pressure (MAP) were assessed simultaneously for 30 min before and after RX-77368 (1.5 ng) administration in urethan-anesthetized rats. RX-77368 increased GMBF from 46.8 +/- 5.3 to 100.6 +/- 20.9 ml.min-1.100 g-1 and MAP from 70.3 +/- 2.1 to 84.3 +/- 5.9 mmHg and decreased GMVR from 1.50 +/- 0.33 to 0.84 +/- 0.08 mmHg.ml-1.min.100 g, whereas GAS was not significantly altered (1.8 +/- 0.4 vs. 4.7 +/- 1.7 mumol/30 min) in vehicle-pretreated rats. The GMBF, MAP, and GMVR responses to RX-77368 were not modified by indomethacin (5 mg/kg ip), whereas GAS was increased. In rats pretreated with capsaicin (125 mg/kg sc) or calcitonin gene-related peptide (CGRP) antagonist hCGRP-(8-37), intracisternal RX-77368 did not increase GMBF or decrease GMVR but did stimulate GAS. These data show that vagal stimulation by the TRH analog RX-77368 injected intracisternally at a nonacid secretory dose increases GMBF. Gastric hyperemia is mediated by CGRP contained in capsaicin-sensitive afferent fibers, whereas acid secretion is under the inhibitory influence of prostaglandins and CGRP.
Developmental expression of SI is regulated in transgenic mice by an evolutionarily conserved promoter
Authors: Tung J. , Markowitz A. J. , Silberg D. G. , Traber P. G.
Published: December 2017

Developmental expression of the sucrase-isomaltase (SI) gene in the mouse intestine involves two major transitions that correspond to critical developmental events. Low levels of SI mRNA were first identified in day 16.5 fetal mouse intestine, immediately after the transition from stratified endoderm to a columnar epithelium organized in nascent villi. Low levels were maintained until the third week of life, when induction of SI mRNA to adult levels was observed coincident with the time of weaning. The mechanism of this pattern of SI gene expression was studied in transgenic mice using a reporter gene construct containing an SI gene promoter that is evolutionarily conserved between mouse and human (nucleotides -201 to +54 of the mouse SI gene). This promoter included the necessary regulatory information to direct transcription to enterocytes in developmental and differentiation-dependent patterns that recapitulated the expression of the endogenous SI gene. However, transgenes lacked the ability to direct induction of precocious expression in suckling animals after administration of corticosteroids. These findings define a short SI gene promoter that contains cis-acting elements that are responsible for developmental and differentiation-dependent transcriptional regulation.
Human hepatocytes express an array of proinflammatory cytokines after agonist stimulation or bacterial invasion
Authors: Rowell D. L. , Eckmann L. , Dwinell M. B. , Carpenter S. P. , Raucy J. L. , Yang S. K. , Kagnoff M. F.
Published: December 2017

Inflammatory cells infiltrate the liver in response to microbial infection or hepatic injury. To assess the potential role hepatocytes may play in initiating or amplifying the acute inflammatory response in the liver, we used three human hepatocyte cell lines and primary human hepatocyte cultures to characterize the repertoire of cytokines that can be expressed and regulated in hepatocytes in response to agonist stimulation or bacterial infection. As reported herein, a proinflammatory cytokine gene program that includes C-X-C and C-C chemokines [interleukin-8(IL-8), growth related (GRO)-alpha, GRO-beta, GRO-gamma, epithelial neutrophil activating peptide-78 (ENA-78), and RANTES] and the cytokines tumor necrosis factor-alpha (TNF-alpha) and macrophage colony stimulating factor was upregulated in human hepatocytes after stimulation with IL-1 alpha or TNF-alpha or bacterial invasion. In contrast, expression of hematopoietic/ lymphoid growth factors by the same cells was either down-regulated (erythropoietin and stem cell factor) or unchanged (IL-7 and IL-15) in response to the identical stimuli. Hepatocytes did not express cytokines that often are associated with the regulation of antigen-specific immune responses (IL-2, IL-4, IL-5, IL-10, IL-12p40, IL-13, and interferon-gamma) or genes for several other proinflammatory cytokines [IL-1 alpha, IL-6, monocyte chemotactic protein-1 (MCP-1), and MCP-3] or hematopoietic growth factors (granulocyte colony stimulating factor, granulocyte macrophage colony stimulating factor, IL-3, and IL-11). Together, these studies suggest that hepatocytes can both initiate and amplify acute inflammatory responses in the liver through the regulated expression and secretion of a specific array of proinflammatory cytokines.
Analysis of the responses of myenteric neurons in the small intestine to chemical stimulation of the mucosa
Authors: Bertrand P. P. , Kunze W. A. , Bornstein J. C. , Furness J. B. , Smith M. L.
Published: December 2017

Responses of myenteric AH and S neurons to local application of chemicals to the mucosa of the guinea pig small intestine were obtained using conventional intracellular recording techniques. Preparations were dissected to reveal the myenteric plexus over one-half of the circumference of the gut with intact mucosa on the the half. Neurons were impaled within the exposed one-half, whereas potential stimulants, in buffered saline, were transiently applied to the mucosa, 1-1.5 mm circumferential from the impalement. The stimulants elicited action potentials (AP) in AH neurons that did not arise from synaptic activity. AH neurons also responded with slow excitatory postsynaptic potentials (EPSP). S neurons were activated synaptically, via fast and slow EPSP, but not nonsynaptically. Mucosal application of solutions of a low pH (3-5) or a high pH (9-11) were both effective stimulants. Solutions of a neutral pH, which was also a control for mild mechanical stimulation, were usually ineffective. Both a short-chain fatty acid, acetate (pH 7.2), and 5-hydroxytryptamine elicited responses in each neuronal type. We conclude that myenteric AH neurons of the guinea pig distal ileum are primary afferent neurons that respond to a variety of mucosally applied chemical stimuli with burst of AP. In addition, the physiologically evoked transmission of slow EPSP to AH neurons suggests that primary afferent neurons interconnect in a self-reinforcing network. S neurons are second or higher order neurons in the reflex pathways.
PACAP-(1-38) as neurotransmitter in pig pancreas: receptor activation revealed by the antagonist PACAP-(6-38)
Authors: Tornoe K. , Hannibal J. , Fahrenkrug J. , Holst J. J.
Published: December 2017

The pituitary adenylyl cyclase-activating polypeptide PACAP-(1-38) has potent pancreatic secretory effects. We studied its immunohistochemical localization, release, and contribution to secretion induced by electrical vagus stimulation using isolated perfused porcine pancreas and the PACAP receptor antagonist PACAP-(6-38) (10(-7) M). PACAP was found in nerve fibers throughout the pancreas but, in particular, encircling ganglionic vasoactive intestinal polypeptide (VIP)-positive nerve cell bodies and, mostly, colocalized with VIP. Vagus stimulation caused its release. PACAP-(1-38)(4 x 10(-9) M) stimulated exocrine and endocrine secretion and released VIP. PACAP-(6-38) decreased PACAP-induced flow of juice to 59 +/- 7.8% and insulin secretion and VIP release to 12 +/- 6.8 and 57 +/- 13%, respectively. Glucagon secretion was unaffected. PACAP-(6-38) reduced vagus-stimulated flow rate to 63 +/- 7.6%, insulin and glucagon responses to 31.8 +/- 13 and 6 +/- 4%, respectively, and VIP release to 23 +/- 8.4% and reduced VIP-induced (2 x 10(-9) M) juice and insulin (but not glucagon) outputs to 8.3 +/- 4.2 and 67 +/- 14%, respectively. In conclusion, 1) pancreatic PACAP fibers seem to activate intrapancreatic VIPergic neurons, 2) PACAP-(6-38) antagonism documents the role of VIP/PACAP for neural regulation but cannot distinguish their relative importance, and 3) a PACAP receptor with low affinity for PACAP-(6-38), associated with glucagon cells, may exist.
Correlation of electrical and contractile activities of the cricopharyngeus muscle in the cat
Authors: Medda B. K. , Lang I. M. , Dodds W. J. , Christl M. , Kern M. , Hogan W. J. , Shaker R.
Published: December 2017

We correlated the electrical and contractile activities of the cricopharyngeus (CP) to better understand the function of the CP and the upper esophageal sphincter (UES). In 40 decerebrate cats, we recorded resting and active tension of the CP and CP force and electromyographic (EMG) activity simultaneously during electrical stimulation of the pharyngoesophageal (PE) nerve, esophageal distension, or swallowing. In six intact cats, the change in diameter of the UES during food swallows was determined in two planes using videofluoroscopy. We found that resting tension of the CP developed quickly with stretch, and the strain-energy function, y = 6.5e3.4(z-1), fit (r = 0.94 +/- 0.06) this relationship. Active tension peaked at 1.68 +/- 0.03 times resting length, which is greater than the maximum distension during swallowing. Activation and relaxation of the CP occurred in approximately 50 and 120 ms, respectively. PE nerve stimulation bilaterally caused a force equal to approximately 90% of the summed force generated by separate stimulation of each PE nerve. The magnitude of the EMG response of the contralateral CP was approximately 18% of the ipsilateral response to unilateral PE nerve stimulation. We conclude that the CP exhibits tension throughout its physiological range of stretch. The CP functions more like a bilateral than a single contiguous muscle, and more like cardiac than striated muscle with regard to its passive elastic properties.
Prevention of parenteral nutrition-induced gut hypoplasia by coinfusion of glucagon-like peptide-2
Authors: Chance W. T. , Foley-Nelson T. , Thomas I. , Balasubramaniam A.
Published: December 2017

Maintaining rats on total parenteral nutrition (TPN) for 6 days significantly reduced mass (-34%), protein (-32%), and DNA (-35%) in small intestine and colon (29-37% decrease). Coinfusion of glucagon-like peptide-2 (GLP-2) normalized each of these variables in duodenum, jejunum, and ileum, but not in colon. Histological analysis of tissue revealed normal mucosa thickness and villus height in small intestine of GLP-2-treated rats, whereas nontreated rats maintained on TPN exhibited villus shortening (-30%) and thinning (-23%) of mucosa. These results suggest that hormonal alterations may be more important than an absence of luminal nutrition in TPN-associated mucosal changes. Additionally, GLP-2 normalization of gut mucosa permits accurate assessment of the influence of reversal of hypoplasia on gut barrier function.
cAMP increases liver Na+-taurocholate cotransport by translocating transporter to plasma membranes
Authors: Mukhopadhayay Sunil , Ananthanarayanan M. , Stieger Bruno , Meier Peter J. , Suchy Frederick J. , Anwer M. Sawkat
Published: December 2017

Adenosine 3′,5′-cyclic monophosphate (cAMP), acting via protein kinase A, increases transport maximum of Na+-taurocholate cotransport within 15 min in hepatocytes (S. Grüne, L. R. Engelking, and M. S. Anwer. J. Biol. Chem. 268: 17734–17741, 1993); the mechanism of this short-term stimulation was investigated. Cycloheximide inhibited neither basal nor cAMP-induced increases in taurocholate uptake in rat hepatocytes, indicating that cAMP does not stimulate transporter synthesis. Studies in plasma membrane vesicles showed that taurocholate uptake was not stimulated by the catalytic subunit of protein kinase A but was higher when hepatocytes were pretreated with cAMP. Immunoblot studies with anti-fusion protein antibodies to the cloned Na+-taurocholate cotransport polypeptide (Ntcp) showed that pretreatment of hepatocytes with cAMP increased Ntcp content in plasma membranes but not in homogenates. Ntcp was detected in microsomes, endosomes, and Golgi fractions, and cAMP pretreatment resulted in a decrease only in endosomal Ntcp content. It is proposed that cAMP increases transport maximum of Na+-taurocholate cotransport, at least in part, by translocating Ntcp from endosomes to plasma membranes.
Alanine uptake activates hepatocellular chloride channels
Authors: Lidofsky Steven D. , Roman Richard M.
Published: December 2017

Cells involved in the retrieval and metabolic conversion of amino acids undergo significant increases in size in response to amino acid uptake. The resultant adaptive responses to cell swelling are thought to include increases in membrane K+and Cl−permeability through activation of volume-sensitive ion channels. This viewpoint is largely based on experimental models of hypotonic swelling, but few mammalian cells experience hypotonic challenge in vivo. Here we have examined volume regulatory responses in a physiological model of cell-swelling alanine uptake in immortalized hepatocytes. Alanine-induced cell swelling was followed by a decrease in cell volume that was temporally associated with an increase in membrane Cl−currents. These currents were dependent both on alanine concentration and Na+, suggesting that currents were stimulated by Na+-coupled alanine uptake. Cl−currents were outwardly rectifying, exhibited an anion permeability sequence of I−> Br−> Cl−, and were inhibited by the Cl−channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid, features similar to those reported for a widely distributed class of volume-sensitive anion channels evoked by experimental hypotonic stress. These findings suggest that volume-sensitive anion channels participate in adaptive responses to amino acid uptake and provide such channels with a new physiological context.
Identification and functional assay of an extracellular calcium-sensing receptor in Necturusgastric mucosa
Authors: Cima Robert R. , Cheng Ivan , Klingensmith Mary E. , Chattopadhyay Naibedya , Kifor Olga , Hebert Steven C. , Brown Edward M. , Soybel David I.
Published: December 2017

In mammals and amphibians, increases in extracellular Ca2+ can activate bicarbonate secretion and other protective functions of gastric mucosa. We hypothesized that the recently cloned extracellular Ca2+-sensing receptor (CaR) is functioning in the gastric mucosa. In Necturus maculosus gastric mucosa, reverse transcription-polymerase chain reaction using primers based on previously cloned CaR sequences amplified a 326-bp DNA fragment that had 84% nucleotide sequence identity with the rat kidney CaR. Immunohistochemical localization of the CaR using specific anti-CaR antiserum revealed its presence on the basal aspect of gastric epithelial cells. In microelectrode studies of Necturus antral mucosa, exposure to elevated Ca2+ (4.8 mM) and the CaR agonists NPS-467 and neomycin sulfate resulted in significant hyperpolarizations of basal membrane electrical potentials and increases in apical-to-basal membrane resistance ratios. Circuit analysis revealed that these changes reflected specific decreases in basolateral membrane resistance. Inhibition of prostaglandin synthesis using indomethacin significantly attenuated these effects. We conclude that the CaR is present and functioning in Necturus gastric antrum.
Outwardly rectifying Cl− channel in guinea pig small intestinal villus enterocytes: effect of inhibitors
Authors: Monaghan Alan S. , Mintenig Gerard M. , Sepúlveda Francisco V.
Published: December 2017

Previous studies in enterocytes isolated from the villus region of small intestinal epithelium have identified a macroscopic current carried by Cl−. In this work a single-channel patch-clamp study was carried out in the same cells, and a spontaneously active, outwardly rectifying Cl− channel was identified and proposed to underlie the whole cell current. The channel had conductances of 62 and 19 pS at 80 and −80 mV, respectively, in symmetrical Cl− solutions in excised patches. Similar activity was seen in cell-attached patches, but only outward currents could be discerned in this configuration. The activity of the channel, measured as open probability, was independent of intracellular calcium levels and voltage. The selectivity sequence for different anions was SCN− > I− > Br− > Cl− > F− > (gluconate, glutamate, [Formula: see text]). The channel was inhibited by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), verapamil, and 4-hydroxytamoxifen (but not by tamoxifen), with potencies similar to those observed for Cl− channels previously described in other cells. Inhibition by trinitrophenyladenosine 5′-triphosphate was also observed but only at depolarized potentials. At 50 mV the half-maximal inhibitory concentration was 18 nM. It is proposed that this channel plays a role in transepithelial Cl−transport and certain regulatory Cl− fluxes.
Reduction of shock-induced gastric damage by a nitric oxide-releasing aspirin derivative: role of neutrophils
Authors: Wallace John L. , McKnight Webb , Wilson Tammy L. , Del Soldato Piero , Cirino Giuseppe
Published: December 2017

The gastric damage associated with hemorrhagic shock appears to occur, at least in part, through neutrophil-dependent mechanisms. Nitric oxide (NO)-releasing derivatives of aspirin have been shown to spare the gastrointestinal tract of injury. As NO can inhibit neutrophil adherence, it is possible that such a derivative of aspirin (NCX-4016) would exert inhibitory effects on neutrophil adherence and therefore be capable of protecting the stomach against shock-induced gastric damage. This hypothesis was tested in this study. Oral administration of NCX-4016 or glyceryl trinitrate or depletion of circulating neutrophils with antineutrophil serum significantly reduced the extent of gastric damage induced by hemorrhagic shock, whereas aspirin had no effect. NCX-4016 and antineutrophil serum pretreatment resulted in significant preservation of gastric blood flow during the shock period. Moreover, NCX-4016, but not aspirin, was capable of inhibiting N-formyl-Met-Leu-Phe-induced leukocyte adherence to postcapillary mesenteric venules. These results suggest that an NO-releasing aspirin derivative reduces the susceptibility of the stomach to shock-induced damage through inhibitory effects on neutrophil adherence to the vascular endothelium.
Intestinal response to growth factors administered alone or in combination with human [Gly2]glucagon-like peptide 2
Authors: Drucker Daniel J. , Deforest Lorraine , Brubaker Patricia L.
Published: December 2017

The control of intestinal epithelial growth is regulated by interactions of growth factors in various cellular compartments of the small and large bowel. Little information is available on the intestinal growth response to combinations of growth factors. We studied the intestinotrophic properties of a dipeptidyl peptidase IV resistant glucagon-like peptide 2 (GLP-2) analog, human [Gly2]GLP-2 (h[Gly2]GLP-2), as well as of epidermal growth factor (EGF), long [Arg3]insulin-like growth factor I (LR3IGF-I), [Gly1]IGF-II, and human growth hormone (hGH), administered by subcutaneous injection alone or in combination in mice. At the doses tested, h[Gly2]GLP-2 was the most potent agent for increasing small and large bowel mass. Mice treated with h[Gly2]GLP-2 and either GH or IGF-I exhibited greater increases in histological parameters of small intestinal growth than did mice treated with h[Gly2]GLP-2 alone. Administration of all five growth factors together induced significant increases in crypt plus villus height and in small and large bowel length and weight. The results of these experiments define regional differences in both the cellular targets and relative activities of intestinotrophic molecules and raise the possibility that selective growth factor combinations may be useful for enhancement of intestinal adaptation in vivo.
Identification and localization of extracellular Ca2+-sensing receptor in rat intestine
Authors: Chattopadhyay Naibedya , Cheng Ivan , Rogers Kimberly , Riccardi Daniela , Hall Amy , Diaz Ruben , Hebert Steven C. , Soybel David I. , Brown Edward M.
Published: December 2017

The extracellular calcium ([Formula: see text])-sensing receptor (CaR) plays vital roles in [Formula: see text] homeostasis, but no data are available on its expression in small and large intestine. Polymerase chain reaction products amplified from reverse-transcribed duodenal RNA using CaR-specific primers showed >99% homology with the rat kidney CaR. Northern analysis with a CaR-specific cRNA probe demonstrated 4.1- and 7.5-kb transcripts in all intestinal segments. Immunohistochemistry with CaR-specific antisera showed clear basal staining of epithelial cells of small intestinal villi and crypts and modest apical staining of the former, whereas there was both basal and apical staining of colonic crypt epithelial cells. In situ hybridization and immunohistochemistry also demonstrated CaR expression in Auerbach’s myenteric plexus of small and large intestines and in the submucosa in the region of Meissner’s plexus. Our results reveal CaR expression in several cell types of small and large intestine, in which it may modulate absorptive and/or secretomotor functions.
Inhibition of bradykinin B2receptor preserves microcirculation in experimental pancreatitis in rats
Authors: Bloechle Christian , Kusterer Klaus , Kuehn Regina M. , Schneider Claus , Knoefel Wolfram T. , Izbicki Jakob R.
Published: December 2017

The effect of B2 receptor bradykinin antagonist icatibant on postcapillary leukostasis, microcirculatory stasis, and tissue necrosis was studied in acute pancreatitis. In rats, pancreatitis was induced by intraductal injection of sodium taurocholate (ST), intravenous caerulein and intraductal infusion of glucodeoxycholic acid (GDOC), or intravenous caerulein infusion alone. Intravital pancreatic microcirculation was observed. Icatibant or vehicle was given 30 min before induction of pancreatitis. In ST pancreatitis, the number of perfused capillaries increased in icatibant-pretreated rats (77% vs. 0% for controls, P < 0.001). Capillary flow was preserved in icatibant-treated rats; total stasis was observed in controls. Mean venular leukocyte adherence decreased in icatibant-treated rats (26% vs. 74% for controls, P < 0.001), and median histopathologic score was reduced (icatibant vs. controls, 5.0 vs. 12 points, respectively; P < 0.01). Kinase II inhibitor captopril or exogenous bradykinin in addition to an otherwise effective dosage of icatibant resulted in microcirculatory stasis, extensive venular leukocyte adherence, and severe histological damage. With a 100 times greater icatibant dosage, this adverse effect was compensated. The beneficial effects of icatibant were also observed in intermediate pancreatitis (caerulein + GDOC). In ST and intermediate pancreatitis, icatibant preserved microcirculation, reduced venular leukocyte adherence, and prevented pancreatic tissue damage. B2 receptor bradykinin-mediated postcapillary leukostasis plays an important role in the pathogenesis of severe forms of acute pancreatitis.
Motilin controls cyclic release of insulin through vagal cholinergic muscarinic pathways in fasted dogs
Authors: Suzuki Hideki , Mochiki Erito , Haga Norihiro , Satoh Minoru , Mizumoto Akiyoshi , Itoh Zen
Published: December 2017

The effect of motilin on insulin release has not been studied in the interdigestive state. Adult mongrel dogs were chronically implanted with force transducers in the stomach and duodenum to monitor contractile activity, and the plasma motilin and insulin concentrations were measured by a specific radioimmunoassay and enzyme immunoassay, respectively. The concentration of insulin in plasma was found to fluctuate in close association with that of motilin and phase III of the interdigestive migrating contractions in the stomach. This spontaneous release of insulin was mimicked by intravenous infusion of motilin at a dose of 0.3 μg ⋅ kg−1⋅ h−1. Exogenous motilin (0.01–0.3 μg/kg) dose dependently stimulated insulin release, which was abolished by atropine, hexamethonium, ondansetron, and truncal vagotomy. Phentolamine significantly enhanced, whereas propranolol inhibited, motilin-induced insulin release. In a perifusion system using islet cells from the canine pancreas, motilin did not affect insulin release. In conclusion, motilin stimulates insulin release through vagal cholinergic, muscarinic receptors on pancreatic β-cells, and the effect appears to be modulated by adrenergic nerves.
Structure of murine enterokinase (enteropeptidase) and expression in small intestine during development
Authors: Yuan Xin , Zheng Xinglong , Lu Deshun , Rubin Deborah C. , Pung Christopher Y. M. , Sadler J. Evan
Published: December 2017

Enterokinase (enteropeptidase) is expressed only in proximal small intestine, where it initiates digestive enzyme activation by converting trypsinogen into trypsin. To investigate this restricted expression pattern, mouse enterokinase cDNA was cloned, and the distribution of enterokinase mRNA and enzymatic activity were determined in adult mice and during gestation. Analysis of enterokinase sequences showed that a mucinlike domain near the NH2terminus is composed of repeated ∼15-amino acid Ser/Thr-rich motifs. By Northern blotting and trypsinogen activation assays, enterokinase mRNA and enzymatic activity were undetectable in stomach, abundant in duodenum, and decreased distally until they were undetectable in midjejunum, ileum, and colon. By in situ mRNA hybridization, enterokinase mRNA was localized to the enterocytes throughout the villus. Expression was not observed in goblet cells, Paneth cells, or Brunner’s glands. Enterokinase mRNA and enzymatic activity were not detected in the duodenum of fetal mice but were easily detected in the duodenum on postnatal days 2–6. Both enterokinase mRNA and enzymatic activity decreased to very low levels after day 7 but increased after weaning and reached a high level characteristic of adult life by day 60. Therefore, in mice, duodenal enterocytes are the major type of cells expressing enterokinase, which appears to be regulated at the level of mRNA abundance.
Postsynaptic enhancement by motilin of muscarinic receptor cation currents in duodenal smooth muscle
Authors: Yamada Kazunori , Yanagida Hiroe , Ito Yushi , Inoue Ryuji
Published: December 2017

We have investigated a potential role of motilin in amplifying the postsynaptic muscarinic responses in the rabbit duodenal smooth muscle cells, using the whole cell variant of patch-clamp technique. Stimulation of motilin receptors by exogenously applied motilin (1 nM) resulted in a large increase in carbachol (CCh)-induced atropine-sensitive cation current ( ICCh) at threshold concentrations of CCh (0.3–1 μM) at 30°C. This potentiation was abolished in the presence of a specific blocker of motilin receptor (GM109) and was attenuated with increased concentrations of either motilin or CCh, being virtually absent with maximally effective concentrations of these agonists. Motilin failed to potentiate ICChwhen the ambient temperature was reduced to 20°C or if the cation current had been directly activated by internal perfusion with guanosine 5′- O-(3-thiotriphosphate) (50 μM) bypassing the muscarinic receptor. These results suggest that some biochemical processes, such as enzymatic reactions, might be involved in the motilin-induced potentiation and that its site of action might be the muscarinic receptor and/or associated G proteins.