bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of individual spikes as “patches” of activation in isolated feline duodenum
Authors: Lammers Wim J. E. P.
Published: December 2017

Asynchrony of spikes has made it difficult to study the spatial and temporal behavior of spikes in the gastrointestinal system. By simultaneously recording from a large number of closely spaced electrodes, we investigated the propagation of individual spikes. Recordings were performed from the serosal surface of the isolated feline duodenum at 240 sites simultaneously. Analysis of the tracings made it possible to reconstruct the propagation of individual spikes. Spikes propagate in the longitudinal and circumferential directions in self-limiting areas or “patches.” Conduction within patches may occur in the orad or aborad direction irrespective of the direction of the slow wave. Most of the patches are smaller (<40 mm2), although inhomogeneous activation by the preceding slow wave may increase their size. Stimulation by ACh, TTX, or tetraethylammonium does not affect the average patch size but does increase significantly their number and distribution in the duodenum [from 26% (control) to 56%, 61%, and 72%, respectively]. In conclusion, individual spikes activate limited areas or patches in the small intestine, and pharmacological stimulation increases the number and distribution of these patches. In the small intestine, this pattern of activation would induce localized contractions. Contraction could be modulated by the size, number, and distribution of spike patches.
Medium-chain triglycerides inhibit free radical formation and TNF-α production in rats given enteral ethanol
Authors: Kono Hiroshi , Enomoto Nobuyuki , Connor Henry D. , Wheeler Michael D. , Bradford Blair U. , Rivera Chantal A. , Kadiiska Maria B. , Mason Ronald P. , Thurman Ronald G.
Published: December 2017

This study determined whether free radical formation by the liver, tumor necrosis factor (TNF)-α production by isolated Kupffer cells, and plasma endotoxin are affected by dietary saturated fat. Rats were fed enteral ethanol and corn oil (E-CO) or medium-chain triglycerides (E-MCT) and control rats received corn oil (C-CO) or medium-chain triglycerides (C-MCT) for 2 wk. E-CO rats developed moderate fatty infiltration and slight inflammation; however, E-MCT prevented liver injury. Serum aspartate aminotransferase levels, gut permeability, and plasma endotoxin doubled with E-CO but were blunted ∼50% with E-MCT. In Kupffer cells from E-CO rats, intracellular calcium was elevated by lipopolysaccharide (LPS) in a dose-dependent manner. In cells from E-MCT rats, increases were blunted by ∼40–50% at all concentrations of LPS. The LPS-induced increase in TNF-α production by Kupffer cells was dose dependent and was blunted by 40% by MCT. E-CO increased radical adducts and was reduced ∼50% by MCT. MCT prevent early alcohol-induced liver injury, in part, by inhibition of free radical formation and TNF-α production by inhibition of endotoxin-mediated activation of Kupffer cells.
A novel in vitro model of Brunner's gland secretion in the guinea pig duodenum
Authors: Moore Beverley A. , Morris Gerald P. , Vanner Stephen
Published: December 2017

A novel in vitro model that combined functional and morphological techniques was employed to directly examine pathways regulating Brunner's gland secretion in isolation from epithelium. In vitro submucosal preparations were dissected from guinea pig duodenum. A videomicroscopy technique was used to measure changes in luminal diameter of glandular acini as an index of activation of secretion. Carbachol elicited concentration-dependent dilations of the lumen (EC50= 2 μM) by activating muscarinic receptors on acinar cells. Ultrastructural and histological analyses demonstrated that dilation was accompanied by single and compound exocytosis of mucin-containing granules and the accumulation of mucoid material within the lumen. Inflammatory mediators (histamine, PGE1, PGE2) and intestinal hormones (CCK, gastrin, vasoactive intestinal polypeptide, secretin) also stimulated glandular secretion, whereas activation of submucosal secretomotor neurons by 5-hydroxytryptamine did not. This study directly demonstrates that multiple hormonal, inflammatory, and neurocrine agents activate Brunner's glands, whereas many have dissimilar effects on the epithelium. This suggests that Brunner's glands are regulated by pathways that act both in parallel to and in isolation from those controlling epithelial secretion.
Regulation of adherens junction protein p120ctnby 10 nM CCK precedes actin breakdown in rat pancreatic acini
Authors: Leser J. , Beil M. F. , Musa O. A. , Adler G. , Lutz M. P.
Published: December 2017

The initial pathophysiological events that characterize CCK-hyperstimulation pancreatitis include the breakdown of the actin filament system and disruption of cadherin-catenin protein complexes. Cadherins and catenins are part of adherens junctions, which may act as anchor for the cellular actin filament system. We examined the composition and regulation of adherens junctions during CCK-induced acinar cell damage. Freshly isolated CCK-stimulated rat pancreatic acini were examined for actin filaments and functional adherens junctions by immunocytology and laser confocal scanning microscopy or by coprecipitation and immunoblotting for E-cadherin, β- and α-catenin, p120ctn, and phosphotyrosine. In addition to E-cadherin and β-catenin, acinar cells express the cadherin-regulatory protein p120ctn and the attachment protein α-catenin. Both colocalize and coimmunoprecipitate with E-cadherin in one complex, and all colocalize with the terminal actin web. Supramaximal secretory CCK concentrations (10 nM) initiated tyrosine phosphorylation of p120ctn but not of β-catenin within 2 min, preceding the breakdown of the terminal actin web by several minutes. Under these conditions, the cadherin-catenin association within the adherens junction complex remained intact. We describe for the first time supramaximal CCK-dependent tyrosine phosphorylation of the adherens junction protein p120ctnand demonstrate the presence of an intact adherens junction protein complex in acinar cells. p120ctn may participate in the actin filament breakdown during experimental conditions mimicking pancreatitis.
Domain-specific purinergic signaling in polarized rat cholangiocytes
Authors: Salter Kelli D. , Fitz J. Gregory , Roman Richard M.
Published: December 2017

In cholangiocytes, adenine nucleotides function as autocrine/paracrine signals that modulate ductular ion transport by activation of purinergic receptors. The purpose of these studies was to identify cellular signals that modulate ATP release and nucleotide processing in polarized normal rat cholangiocytes. In Ussing chamber studies, selective exposure of the apical and basolateral membranes to ATP or adenosine 5′- O-(3-thiotriphosphate) (ATPγS) stimulated increases in short-circuit current. Apical purinergic receptor agonist preference was consistent with the P2Y2subtype. In contrast, basolateral ADP was more potent in stimulating transepithelial currents, consistent with the expression of different basolateral P2 receptor(s). Luminometric analysis revealed that both membranes exhibited constitutive ATP efflux. Hypotonic exposure enhanced ATP release in both compartments, whereas decreases in ATP efflux during hypertonicity were more prominent at the apical membrane. Increases in intracellular cAMP, cGMP, and Ca2+also increased ATP permeability, but selective effects on apical and basolateral ATP release differed. Finally, the kinetics of ATP degradation in apical and basolateral compartments were distinct. These findings suggest that there are domain-specific signaling pathways that contribute to purinergic responses in polarized cholangiocytes.
TIEG proteins join the Smads as TGF-β-regulated transcription factors that control pancreatic cell growth
Authors: Cook Tiffany , Urrutia Raul
Published: December 2017

The control of epithelial cell proliferation, differentiation, and apoptosis requires a balance between signaling and transcriptional regulation. Recent developments in pancreatic cell research have revealed that transforming growth factor-β (TGF-β) signaling is important for the regulation of each of these phenomena. More importantly, perturbations in this pathway are associated with pancreatic cancer. A chief example of these alterations is the mutation in the TGF-β-regulated transcription factor Smad4/DPC4 that is found in a large percentage of pancreatic tumors. Surprisingly, studies on transcription factors have remained an underrepresented area of pancreatic research. However, the discovery of Smad4/DPC4 as a transcription factor fueled further studies aimed at characterizing transcription factors involved in normal and neoplastic pancreatic cell growth. Our laboratory recently described the existence of a novel family of zinc finger transcription factors, TGF-β-inducible early-response gene (TIEG)1 and TIEG2, from the exocrine pancreas that, similarly to Smads, participate in the TGF-β response and inhibit epithelial cell proliferation. This review therefore focuses on describing the structure and function of these two families of transcription factor proteins that are becoming key players in the regulation of pancreatic cell growth.
Differential lobular induction in rat liver of glutathioneS-transferase A1/A2 by phenobarbital
Authors: Selim Niazy , Branum Gene D. , Liu Xia , Whalen Richard , Boyer Thomas D.
Published: December 2017

Phenobarbital and other xenobiotics induce drug-metabolizing enzymes, including glutathione S-transferase A1/A2 (rGSTA1/A2). We examined the mechanism of induction of rGSTA1/A2 in rat livers after phenobarbital treatment. The induction of rGSTA1/A2 was not uniform across the hepatic lobule; steady-state transcript levels were threefold higher in perivenous hepatocytes relative to periportal hepatocytes when examined by in situ hybridization 12 h after a single dose of phenobarbital. Administration of a second dose of phenobarbital 12 or 24 h after the first dose did not equalize the induction of rGSTA1/A2 across the lobule. The transcriptional activity of the rGSTA1/A2 gene was increased 3.5- to 5.5-fold in whole liver by phenobarbital, but activities were the same in enriched periportal and perivenous subpopulations of hepatocytes from phenobarbital-treated animals. The half-life of rGSTA1/A2 mRNA in control animals was 3.6 h, whereas it was 10.2 h in phenobarbital-treated animals. We conclude that phenobarbital induces rGSTA1/A2 expression by increasing transcriptional activity across the lobule but induction of rGSTA1/A2 is greater in perivenous hepatocytes due to localized stabilization of mRNA transcripts.
Role of GRPergic neurons in secretin-evoked exocrine secretion in isolated rat pancreas
Authors: Park Hyung Seo , Kwon Hyeok Yil , Lee Yun Lyul , Chey William Y. , Park Hyoung Jin
Published: December 2017

Effects of intrapancreatic gastrin-releasing peptide (GRP)-containing neurons on secretin-induced pancreatic secretion were investigated in the totally isolated perfused rat pancreas. Electrical field stimulation (EFS) increased secretin (12 pM)-induced pancreatic secretions of fluid and amylase. EFS induced a twofold increase in GRP concentration in portal effluent, which was completely inhibited by tetrodotoxin but not modified by atropine. An anti-GRP antiserum inhibited the EFS-enhanced secretin-induced secretions of fluid and amylase by 12 and 43%, respectively, whereas a simultaneous infusion of the antiserum and atropine completely abolished them. Exogenous GRP dose-dependently increased the secretin-induced pancreatic secretion with an additive effect on fluid secretion and a potentiating effect on amylase secretion, which was not affected by atropine. In conclusion, excitation by EFS of GRPergic neurons in the isolated rat pancreas results in the release of GRP, which exerts an additive effect on fluid secretion and a potentiating effect on amylase secretion stimulated by secretin. The release and action of GRP in the rat pancreas are independent of cholinergic tone.
Effect of chronic inflammation on ileal short-chain fatty acid/bicarbonate exchange
Authors: Manokas Tasos , Fromkes John J. , Sundaram Uma
Published: December 2017

Short-chain fatty acids (SCFA) have been demonstrated to at least partially ameliorate chronic intestinal inflammation. However, whether and how intestinal SCFA absorption may be altered during chronic intestinal inflammation is unknown. A rabbit model of chronic ileitis produced by coccidia was used to determine the effect of chronic inflammation on ileal SCFA/[Formula: see text] exchange. SCFA/[Formula: see text] exchange was present in the brush-border membrane (BBM) of villus but not crypt cells from normal rabbit ileum. An anion-exchange inhibitor, DIDS, significantly inhibited SCFA/[Formula: see text] exchange. Extravesicular Cl− did not alter the uptake of SCFA, suggesting that SCFA/[Formula: see text] exchange is a transport process distinct from Cl−/[Formula: see text] exchange. In chronically inflamed ileum, SCFA/[Formula: see text] exchange was also present only in BBM of villus cells. The exchanger was sensitive to DIDS and was unaffected by extravesicular Cl−. However, SCFA/[Formula: see text] exchange was significantly reduced in villus cell BBM vesicles (BBMV) from chronically inflamed ileum. Kinetic studies demonstrated that the maximal rate of uptake of SCFA, but not the affinity for SCFA, was reduced in chronically inflamed rabbit ileum. These data demonstrate that a distinct SCFA/[Formula: see text] exchange is present on BBMV of villus but not crypt cells in normal rabbit ileum. SCFA/[Formula: see text] exchange is inhibited in chronically inflamed rabbit ileum. The mechanism of inhibition is most likely secondary to a reduction in transporter numbers rather than altered affinity for SCFA.
Endogenous IGF-I regulates IGF binding protein production in human intestinal smooth muscle cells
Authors: Kuemmerle John F.
Published: December 2017

Human intestinal smooth muscle in culture produces insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP)-3, IGFBP-4, and IGFBP-5, which modulate the effects of IGF-I. This study examined the regulation of IGFBP production by endogenous IGF-I. R3-IGF-I, an agonist unaffected by IGFBPs, elicited concentration-dependent increase in growth, measured by [3H]thymidine incorporation, and production of IGFBP-3, IGFBP-4, and IGFBP-5, measured by Western blot. Antagonists of the IGF-I receptor, IGF-I Analog or monoclonal antibody 1H7, elicited concentration-dependent inhibition of growth and decrease in IGFBP-3, IGFBP-4, and IGFBP-5 production, implying that endogenous IGF-I stimulated growth and IGFBP production. R3-IGF-I-induced increase in IGFBP-3, IGFBP-4, and IGFBP-5 production was partially inhibited by a mitogen-activated protein (MAP) kinase or a phosphatidylinositol-3-kinase (PI 3-kinase) inhibitor and abolished by the combination. We conclude that endogenous IGF-I stimulates growth and IGFBP-3, IGFBP-4, and IGFBP-5 production in human intestinal smooth muscle cells. Regulation of IGFBP production by IGF-I is mediated by activation of distinct MAP kinase and PI 3-kinase pathways, the same pathways through which IGF-I stimulates growth.
Slowing of intestinal transit by fat depends on naloxone-blockable efferent, opioid pathway
Authors: Zhao Xiao-Tuan , Wang Lijie , Lin Henry C.
Published: December 2017

Slowing of transit through the proximal small intestine by fat in the distal gut is termed the ileal brake. Intravenous naloxone, an opioid receptor antagonist, abolished the fat-induced ileal brake, suggesting that an endogenous opioid pathway may be involved in this response. To test the hypothesis that slowing of intestinal transit by fat in the distal half of the gut depends on an opioid pathway located on the efferent limb of this response, we compared intestinal transit in dogs equipped with duodenal and midgut fistulas while naloxone was either compartmentalized with oleate to the distal half of the gut or with buffer to the proximal half of the gut. We found that intestinal transit depended on the perfusion conditions ( P < 0.00001). Specifically, compared with ileal brake (marker recovery of 35.7 ± 7.4%), intestinal transit was accelerated when naloxone was delivered into the proximal half of the gut (76.2 ± 5.2%) ( P< 0.005) but not the distal half of the gut (29.4 ± 5.4%). We conclude that slowing of intestinal transit by fat in the distal half of the gut depends on an opioid pathway located on the efferent limb of the ileal brake.
Glucagon-like peptide (GLP-1) is involved in the central modulation of fecal output in rats
Authors: Gülpinar M. Ali , Bozkurt Ayhan , Coşkun Tamer , Ulusoy Nefise B. , Yeǧen Berrak Ç.
Published: December 2017

In addition to its insulinotropic action, exogenously administered glucagon-like peptide (GLP-1) inhibits gastropancreatic motility and secretion via central pathways. The aims of the present study were to evaluate the effects of exogenous GLP-1-(7–36) amide on fecal output and to investigate the role of endogenous GLP-1 on stress-induced colonic activity. With the use of a stereotaxic instrument, adult male Sprague-Dawley rats weighing 200–250 g were fitted with stainless steel cerebroventricular guide cannulas under ketamine anesthesia. A group of rats were placed in Bollman-type cages to induce restraint stress. Fecal output monitored for 2 h was increased significantly by intracerebroventricular GLP-1 to 500, 1,000, and 3,000 pmol/rat ( P < 0.05–0.01), whereas intraperitoneal GLP-1 had no effect. Intracerebroventricular administration of the GLP-1 receptor antagonist exendin-(9–39) (10 nmol/rat) reversed the increases induced by GLP-1 (500 pmol/rat; P < 0.01). Similar results were also observed with the injection of corticotropin-releasing factor receptor antagonist astressin (10 μg/rat icv). The significant increase in fecal pellet output induced by restraint stress was also decreased by both intracerebroventricular exendin (10 nmol/rat) and astressin (10 μg/rat; P < 0.01–0.001). These results suggest that GLP-1 participates in the central, but not peripheral, regulation of colonic motility via its own receptor and that GLP-1 is likely to be a candidate brain-gut peptide that acts as a physiological modulator of stress-induced colonic motility.
Gene expression of divalent metal transporter 1 and transferrin receptor in duodenum of Belgrade rats
Authors: Oates Phillip S. , Thomas Carla , Freitas Elizabeth , Callow Matthew J. , Morgan Evan H.
Published: December 2017

Regulation of iron absorption is thought to be mediated by the amount of iron taken up by duodenal crypt cells via the transferrin receptor (TfR)-transferrin cycle and the activity of the divalent metal transporter (DMT1), although DMT1 cannot be detected morphologically in crypt cells. We investigated the uptake of transferrin-bound iron by duodenal enterocytes in Wistar rats fed different levels of iron and Belgrade (b/b) rats in which iron uptake by the transferrin cycle is defective because of a mutation in DMT1. We showed that DMT1 in our colony of b/b rats contains the G185R mutation, which in enterocytes results in reduced cellular iron content and increased DMT1 gene expression similar to levels in iron deficiency of normal rats. In all groups the uptake of transferrin-bound iron by crypt cells was directly proportional to plasma iron concentration, being highest in iron-loaded Wistar rats and b/b rats. We conclude that the uptake of transferrin-bound iron by developing enterocytes is largely independent of DMT1.
Pathobiology of Visceral Pain: Molecular Mechanisms and Therapeutic Implications V. Central nervous system processing of somatic and visceral sensory signals
Authors: Ladabaum Uri , Minoshima Satoshi , Owyang Chung
Published: December 2017

Somatic and visceral sensation, including pain perception, can be studied noninvasively in humans with functional brain imaging techniques. Positron emission tomography and functional magnetic resonance imaging have identified a series of cerebral regions involved in the processing of somatic pain, including the anterior cingulate, insular, prefrontal, inferior parietal, primary and secondary somatosensory, and primary motor and premotor cortices, the thalamus, hypothalamus, brain stem, and cerebellum. Experimental evidence supports possible specific roles for individual structures in processing the various dimensions of pain, such as encoding of affect in the anterior cingulate cortex. Visceral sensation has been examined in the setting of myocardial ischemia, distension of hollow viscera, and esophageal acidification. Although knowledge regarding somatic sensation is more extensive than the information available for visceral sensation, important similarities have emerged between cerebral representations of somatic and visceral pain.
Attenuated febrile response to lipopolysaccharide in rats with biliary obstruction
Authors: McCullough L. K. , Takahashi Y. , Le T. , Pittman Q. J. , Swain M. G.
Published: December 2017

Patients with biliary tract obstruction have unexplained, inordinately high rates of perioperative morbidity and mortality, whereas cholestatic animals display abnormal hypothalamic responses to pyrogenic stimuli. We asked if obstructive cholestasis was associated with abnormal fever generation. Male Sprague-Dawley rats (250 g) underwent laparotomy for implantation of thermistors and either bile duct resection (BDR) or sham operation. After recovery, temperatures were recorded by telemetry and conscious, unrestrained rats in each group were injected intraperitoneally with either interleukin-1β (IL-1β;1 μg/kg) or Escherichia colilipopolysaccharide (LPS; 50 μg/kg). Baseline temperatures in both groups were similar. Febrile responses after IL-1β injection in BDR and sham groups were not significantly different. However, in response to LPS injection, BDR rats showed an initial hypothermia with a subsequently attenuated febrile response. Administration of anti-tumor necrosis factor-α (TNF-α) antibody 2 h before LPS injection blocked the LPS-induced hypothermia seen in BDR animals. However, serum levels of TNF-α were not significantly different between sham and BDR animals after LPS injection at any time point measured (0, 1.5, and 3 h).
Changes in methionine adenosyltransferase andS-adenosylmethionine homeostasis in alcoholic rat liver
Authors: Lu Shelly C. , Huang Zong-Zhi , Yang Heping , Mato José M. , Avila Matías A. , Tsukamoto Hidekazu
Published: December 2017

Liver-specific and non-liver-specific methionine adenosyltransferase (MAT) are products of two genes, MAT1A and MAT2A, respectively, that catalyze the formation of S-adenosylmethionine (SAM). We previously showed that MAT2A expression was associated with more rapid cell growth. Changes in MAT expression have not been examined in animal models of alcoholic liver injury, which is the focus of the current study. After rats were fed intragastrically with ethanol and high fat for 9 wk, the mRNA level of both MAT forms doubled but only the protein level of MAT2A increased. Although liver-specific MAT activity did not change, it was 32% lower after one and 68% lower after eight weekly enteral doses of lipopolysaccharide. Hepatic levels of methionine, SAM, and DNA methylation fell by ∼40%. c- myc was hypomethylated, and its mRNA level increased. Genome-wide DNA strand break increased. Thus in the prefibrotic stage of alcoholic liver injury, there is already a switch in MAT expression, global DNA hypomethylation, increased c- myc expression, and genome-wide DNA strand break. These changes may be important in predisposing this liver disease to malignant degeneration.
Cardiac excitation-contraction coupling in the portal hypertensive rat
Authors: Zavecz James H. , Bueno Orlando , Maloney Ronald E. , O'Donnell James M. , Roerig Sandra C. , Battarbee Harold D.
Published: December 2017

Basal contractility and responses to β-adrenoceptor activation are compromised in hearts from rats with chronic portal vein stenosis. Here we report the effect of partial ligation of the portal vein on myocardial G protein expression, β-adrenoceptor-G protein coupling, and excitation-contraction coupling (ECC). Contractility (d T/d t) was reduced 30–50% in right and left ventricles, but the rate of relaxation (−d T/d t) was unaffected. Isoproterenol-induced positive inotropism was diminished, but there was no difference in ED50. The concentration-dependent increase in −d T/d t was unaffected. Gsα and Giα expression, cholera toxin- and pertussis toxin-induced ADP-ribosylation, and formation of the agonist-receptor-Gscomplex were unaffected by portal vein stenosis. Of the components of ECC examined, the caffeine-sensitive sarcoplasmic reticulum Ca2+pool was reduced 35%, although the Ca2+uptake and release processes were unchanged; the apparent density of L-type Ca2+channels decreased 60% with no change in affinity; the dihydropyridine Ca2+channel agonist BAY K 8644 produced relative changes in d T/d t that were similar in both groups, suggesting normal function in the remaining Ca2+channels; and Na+/Ca2+exchange was reduced 50% in the portal vein stenosis group. These data suggest that the effect of portal vein stenosis on the myocardium is the result of alterations to ECC.
Upper esophageal sphincter function during gastroesophageal reflux events revisited
Authors: Torrico Silvia , Kern Mark , Aslam Muhammad , Narayanan Subashini , Kannappan Ananda , Ren Junlong , Sui Zhumei , Hofmann Candy , Shaker Reza
Published: December 2017

Upper esophageal sphincter (UES) function during gastroesophageal reflux events is not completely elucidated because previous studies addressing this issue yielded conflicting results. We reexamined the UES pressure response to intraluminal esophageal pressure and pH changes induced by reflux events. We studied 14 healthy, asymptomatic volunteers (age 49 ± 6 yr) and 7 gastroesophageal reflux disease patients (age 48 ± 5 yr). UES pressure, intraesophageal pressure, and pH were monitored at the distal, middle, and proximal esophagus concurrently in the supine position 1 h before and 2 h after a 1,000-calorie meal. A total of 321 reflux events were identified by the development of abrupt reflux-induced intraesophageal pressure increase (IPI); 285 events occurred in patients and 36 in control subjects. In control subjects 33 of 36 and in patients 252 of 285 IPI events were associated with a pH drop. Among patients and control subjects, 99% and 100%, respectively, of all IPI events irrespective of pH drop were associated with abrupt increase in UES pressure (34 ± 2 and 27 ± 6 mmHg, respectively). The average percentage of maximum UES pressure increase over prereflux values ranged between 66% and 96% (control subjects) and 34% and 122% (patients). IPIs induced by both acidic and nonacidic reflux events evoke strong UES contractile responses.
Esophageal tone in patients with total aperistalsis: gastroesophageal reflux disease versus achalasia
Authors: Mearin Fermín , Vasconez Celia , Zárate Natalia , Malagelada Juan R.
Published: December 2017

We have evaluated esophageal tone in two different conditions that, in some cases, similarly impair phasic esophageal motility. Studies were performed in 14 healthy volunteers, 10 patients with total esophageal aperistalsis secondary to gastroesophageal reflux disease (GERD), and 25 untreated achalasia patients. We quantified esophageal compliance and relaxation induced by a nitric oxide donor using a barostat. Intraesophageal volume at a minimal distending pressure (2 mmHg) was not significantly different among all three groups (4.1 ± 0.7, 3.8 ± 0.7, and 4.2 ± 1.2 ml for healthy, GERD, and achalasia groups, respectively). Esophageal compliance was significantly increased ( P < 0.05 vs. healthy group) in the two groups of patients with aperistalsis (1.9 ± 0.2, 3.0 ± 0.2, and 3.1 ± 0.3 ml/mmHg for healthy, GERD, and achalasia groups, respectively). Esophageal relaxation was decreased in GERD patients (Δ diameter: 0.4 ± 0.1 cm) and increased in achalasia patients (Δ diameter: 1.3 ± 0.4 cm) relative to healthy subjects (Δ diameter: 0.9 ± 0.2 cm) ( P < 0.05 for GERD vs. achalasia and healthy groups). Our results indicate that diseases that similarly impair phasic esophageal motility may affect esophageal tone differently.
In vivo changes in the intestinal reflexes and the response to CCK in the inflamed small intestine of the rat
Authors: Torrents D. , Vergara P.
Published: December 2017

Functional motor changes and morphological alterations have been associated with intestinal inflammation. The aim of our study was to evaluate functional alterations of intestinal reflexes and of the responses to CCK in the Trichinella spiralis model of intestinal inflammation. Rats were prepared with strain gauges and electrodes in the small intestine to evaluate spontaneous motor activity, the ascending contraction of the peristaltic reflex, and the motor responses to CCK-8 infusion. Infected animals showed increased motor activity at the duodenum and jejunum but not at the ileum. Ascending contraction was increased in both duodenum and ileum. Ascending excitation after Nω-nitro-l-arginine was still increased as well as the residual response after atropine. Response to CCK-8 during intestinal inflammation was changed in the jejunum, in which it turned from the inhibition shown in healthy animals to excitation. NADPH-diaphorase staining did not show any changes between distribution and density of positive neurons in either healthy or infected animals. In conclusion, intestinal inflammation induces functional changes in the motor activity that could explain the abnormal motor responses observed in inflammatory disorders.
Regulation of glucose-dependent insulinotropic polypeptide release by protein in the rat
Authors: Wolfe M. Michael , Zhao Ka-Bing , Glazier Kenneth D. , Jarboe Linda A. , Tseng Chi-Chuan
Published: December 2017

Glucose-dependent insulinotropic polypeptide (GIP) release has been demonstrated predominantly after ingestion of carbohydrate and fat. These studies were conducted to determine the effects of protein on GIP expression in the rat. Whereas no significant changes in duodenal mucosal GIP mRNA levels were detected in response to peptone, the duodenal GIP concentration increased from 8.4 ± 1.5 to 19.8 ± 3.2 ng GIP/mg protein at 120 min ( P < 0.01). Plasma GIP levels also increased from 95 ± 5.2 pg/ml to a peak of 289 ± 56.1 pg/ml at 120 min ( P < 0.01). To determine whether the effects of protein on GIP were due to stimulation of acid secretion, rats were pretreated with 10 mg/kg omeprazole, after which mucosal and plasma GIP concentrations were partially attenuated. To further examine the effects of luminal acid, rats were administered intraduodenal 0.1 M HCl for 120 min, which significantly enhanced GIP expression. These studies indicate that nutrient protein provides a potent stimulus for GIP expression in the rat, an effect that occurs at the posttranslational level and may be mediated in part through the acid-stimulatory properties of protein. The effects of acid on GIP are consistent with a role for GIP as an enterogastrone in the rat.
Peripheral PYY inhibits intracisternal TRH-induced gastric acid secretion by acting in the brain
Authors: Yang Hong , Kawakubo Keishi , Wong Helen , Ohning Gordon , Walsh John , Taché Yvette
Published: December 2017

The site of action of peripheral peptide YY (PYY)-induced inhibition of vagally stimulated gastric acid secretion was studied using immunoneutralization with PYY antibody in urethan-anesthetized rats. Gastric acid secretion (59 ± 7 μmol/90 min) stimulated by intracisternal injection of the stable thyrotropin-releasing hormone (TRH) analog RX-77368 (14 pmol/rat) was dose-dependently inhibited by 52%, 69%, and 83% by intravenous infusion of 0.25, 0.5, and 1.0 nmol · kg−1 · h−1 PYY, respectively. PYY or PYY3–36 (2.4 pmol/rat) injected intracisternally also inhibited the acid response to intracisternal RX-77368 by 73% and 80%, respectively. Intravenous pretreatment with PYY antibody (4.5 mg/rat), which shows a 35% cross-reaction with PYY3–36 by RIA, completely prevented the inhibitory effect of intravenously infused PYY (1 nmol · kg−1 · h−1). When injected intracisternally, the PYY antibody (280 μg/rat) reversed intracisternal PYY (2.4 pmol)- and intravenous PYY (1 nmol · kg−1 · h−1)-induced inhibition of acid response to intracisternal RX-77368 by 64% and 93.5%, respectively. These results provide supporting evidence that peripheral PYY inhibits central vagal stimulation of gastric acid secretion through an action in the brain.
Transplanted reporter cells help in defining onset of hepatocyte proliferation during the life of F344 rats
Authors: Sokhi Rana P. , Rajvanshi Pankaj , Gupta Sanjeev
Published: December 2017

Transplanted hepatocytes integrate in the liver parenchyma and exhibit gene expression patterns that are similar to adjacent host hepatocytes. To determine the fate of genetically marked hepatocytes in the context of hepatocellular proliferation throughout the rodent life span, we transplanted Fischer 344 (F344) rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient rats. The proliferative activity in transplanted hepatocytes was studied in animals ranging in age from a few days to 2 yr. Transplanted hepatocytes proliferated during liver development between 1 and 6 wk of age, each dividing an estimated two to five times. DNA synthesis in occasional cells was demonstrated by localizing bromodeoxyuridine incorporation. There was no evidence for transplanted cell proliferation between 6 wk and 1 yr of age. Subsequently, transplanted cells proliferated again, with increased sizes of transplanted cell clusters at 18 and 24 mo of age. The proliferative activity of transplanted cells was greater in rats entering senescence compared with during postnatal liver development. In old rats, some liver lobules were composed entirely of transplanted cells. We conclude that hepatocyte proliferation in the livers of very young and old F344 rats is regulated in a temporally determined, biphasic manner. The findings will be relevant to mechanisms concerning liver development, senescence, and oncogenesis, as well as to cell and gene therapy.
GH decreases hepatic amino acid degradation after small bowel resection in rats without enhancing bowel adaptation
Authors: Ljungmann K. , Grøfte T. , Kissmeyer-Nielsen P. , Flyvbjerg A. , Vilstrup H. , Tygstrup N. , Laurberg S.
Published: December 2017

Growth hormone (GH) treatment in short bowel syndrome is controversial, and the mechanisms of a possible positive effect remain to be elucidated. Rats were randomly subjected to either an 80% jejunoileal resection or sham operation and were given either placebo (NaCl) or biosynthetic rat GH (brGH). The in vivo capacity of urea nitrogen synthesis (CUNS) and the expression of urea cycle enzymes were measured and related to changes in body weight and adaptive growth in ileal segments on days 7and 14. Ileal segments were examined by unbiased stereological techniques. brGH treatment decreased CUNS among the resected rats by 19% ( P < 0.05) and 36% ( P < 0.05) on days 7 and 14, respectively. The mRNA levels of urea cycle enzyme genes were not influenced by brGH treatment. brGH treatment did not increase the adaptive growth in the ileal segments. In conclusion, we found that GH treatment decreased the accelerated postoperative hepatic amino acid degradation in experimental short bowel syndrome without enhancing the morphological intestinal adaptation.
Intestinal ion transport in NKCC1-deficient mice
Authors: Grubb B. R. , Lee E. , Pace A. J. , Koller B. H. , Boucher R. C.
Published: December 2017

The Na+-K+-2Cl− cotransporter (NKCC1) located on the basolateral membrane of intestinal epithelia has been postulated to be the major basolateral Cl− entry pathway. With targeted mutagenesis, mice deficient in the NKCC1 protein were generated. The basal short-circuit current did not differ between normal and NKCC1 −/− jejuna. In the −/− jejuna, the forskolin response (22 μA/cm2; bumetanide insensitive) was significantly attenuated compared with the bumetanide-sensitive response (52 μA/cm2) in normal tissue. Ion-replacement studies demonstrated that the forskolin response in the NKCC1 −/− jejuna was HCO3 − dependent, whereas in the normal jejuna it was independent of the HCO3 − concentration in the buffer. NKCC1 −/− ceca exhibited a forskolin response that did not differ significantly from that of normal ceca, but unlike that of normal ceca, was bumetanide insensitive. Ion-substitution studies suggested that basolateral HCO3 − as well as Cl− entry (via non-NKCC1) paths played a role in the NKCC1 −/− secretory response. In contrast to cystic fibrosis mice, which lack both basal and stimulated Cl− secretion and exhibit severe intestinal pathology, the absence of intestinal pathology in NKCC1 −/− mice likely reflects the ability of the intestine to secrete HCO3 − and Cl− by basolateral entry mechanisms independent of NKCC1.
Systemic lipopolysaccharide influences rectal sensitivity in rats: role of mast cells, cytokines, and vagus nerve
Authors: Coelho Anne-Marie , Fioramonti Jean , Buéno Lionel
Published: December 2017

Intraperitoneal lipopolysaccharide (LPS) produces somatic hyperalgesia, releases interleukin (IL)-1β and tumor necrosis factor-α (TNF-α), and activates vagal afferents. The aim of this study was to evaluate the effect of peripheral LPS on rectal sensitivity and to specify the mechanisms involved. Abdominal muscle contractions were recorded in conscious rats equipped with intramuscular electrodes. Rectal distension (RD) was performed at various times after LPS or experimental treatments. In controls, RD significantly increased the number of abdominal contractions from a threshold volume of distension of 0.8 ml. At the lowest volume (0.4 ml), this number was increased after administration of LPS (3, 9, and 12 h later), recombinant human IL-1β (from 3 to 9 h), recombinant bovine TNF-α (from 6 to 9 h), and BrX-537A (from 6 to 12 h), a mast cell degranulator. The effect of LPS was reduced by doxantrazole, Lys-d-Pro-Thr, and soluble recombinant TNF receptor. Vagotomy selectively amplified the response to LPS. We conclude that, in vivo, intraperitoneal LPS lowers visceral pain threshold (allodynia) through a mechanism involving mast cell degranulation and IL-1β and TNF-α release and that the vagus nerve may exert a tonic protective role against LPS-induced rectal allodynia.
Cell transplantation causes loss of gap junctions and activates GGT expression permanently in host liver
Authors: Gupta Sanjeev , Rajvanshi Pankaj , Malhi Harmeet , Slehria Sanjeev , Sokhi Rana P. , Vasa Srinivasa R. G. , Dabeva Mariana , Shafritz David A. , Kerr Andrew
Published: December 2017

Cell transplantation into hepatic sinusoids, which is necessary for liver repopulation, could cause hepatic ischemia. To examine the effects of cell transplantation on host hepatocytes, we transplanted Fisher 344 rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient rats. Within 24 h of cell transplantation, areas of ischemic necrosis, along with transient disruption of gap junctions, appeared in the liver. Moreover, host hepatocytes expressed γ-glutamyl transpeptidase (GGT) extensively, which was observed even 2 years after cell transplantation. GGT expression was not associated with α-fetoprotein activation, which is present in progenitor cells. Increased GGT expression was apparent after transplantation of nonparenchymal cells and latex beads but not after injection of saline, fragmented hepatocytes, hepatocyte growth factor, or turpentine. Some host hepatocytes exhibited apoptosis, as well as DNA synthesis, between 24 and 48 h after cell transplantation. Changes in gap junctions, GGT expression, DNA synthesis, and apoptosis after cell transplantation were prevented by vasodilators. The findings indicated the onset of ischemic liver injury after cell transplantation. These hepatic perturbations must be considered when transplanted cells are utilized as reporters for biological studies.
p53-Dependent acinar cell apoptosis triggers epithelial proliferation in duct-ligated murine pancreas
Authors: Scoggins Charles R. , Meszoely Ingrid M. , Wada Michihiko , Means Anna L. , Yang Liying , Leach Steven D.
Published: December 2017

The mechanisms linking acinar cell apoptosis and ductal epithelial proliferation remain unknown. To determine the relationship between these events, pancreatic duct ligation (PDL) was performed on p53(+/+) and p53(−/−) mice. In mice bearing a wild-type p53 allele, PDL resulted in upregulation of p53 protein in both acinar cells and proliferating duct-like epithelium. In contrast, upregulation of Bcl-2 occurred only in duct-like epithelium. Both p21WAF1/CIP1and Bax were also upregulated in duct-ligated lobes. After PDL in p53(+/+) mice, acinar cells underwent widespread apoptosis, while duct-like epithelium underwent proliferative expansion. In the absence of p53, upregulation of p53 target genes and acinar cell apoptosis did not occur. The absence of acinar cell apoptosis in p53(−/−) mice also eliminated the proliferative response to duct ligation. These data demonstrate that PDL-induced acinar cell apoptosis is a p53-dependent event and suggest a direct link between acinar cell apoptosis and proliferation of duct-like epithelium in duct-ligated pancreas.
Selective sparing of goblet cells and Paneth cells in the intestine of methotrexate-treated rats
Authors: Verburg Melissa , Renes Ingrid B. , Meijer Helen P. , Taminiau Jan A. J. M. , Büller Hans A. , Einerhand Alexandra W. C. , Dekker Jan
Published: December 2017

Proliferation, differentiation, and cell death were studied in small intestinal and colonic epithelia of rats after treatment with methotrexate. Days 1–2 after treatment were characterized by decreased proliferation, increased apoptosis, and decreased numbers and depths of small intestinal crypts in a proximal-to-distal decreasing gradient along the small intestine. The remaining crypt epithelium appeared flattened, except for Paneth cells, in which lysozyme protein and mRNA expression was increased. Regeneration through increased proliferation during days 3–4 coincided with villus atrophy, showing decreased numbers of villus enterocytes and decreased expression of the enterocyte-specific genes sucrase-isomaltase and carbamoyl phosphate synthase I. Remarkably, goblet cells were spared at villus tips and remained functional, displaying Muc2 and trefoil factor 3 expression. On days 8–10, all parameters had returned to normal in the whole small intestine. No methotrexate-induced changes were seen in epithelial morphology, proliferation, apoptosis, Muc2, and TFF3 immunostaining in the colon. The observed small intestinal sparing of Paneth cells and goblet cells following exposure to methotrexate is likely to contribute to epithelial defense during increased vulnerability of the intestinal epithelium.
Inhibition of enterotoxin-induced porcine colonic secretion by diarylsulfonylureas in vitro
Authors: O'Donnell Erin K. , Sedlacek Roger L. , Singh Ashvani K. , Schultz Bruce D.
Published: December 2017

Muscle-stripped piglet colon was used to evaluate changes in short-circuit current ( Isc) as an indicator of anion secretion. Mucosal exposure to Escherichia coli heat-stable (STa) or heat-labile enterotoxins (LT) stimulated Iscby 32 ± 5 and 42 ± 7 μA/cm2, respectively. Enterotoxin-stimulated Iscwas not significantly affected by either 4,4′-diaminostilbene-2,2′-disulfonic acid or CdCl2, inhibitors of Ca2+-activated Cl−channels and ClC-2 channels, respectively. Alternatively, N-(4-methylphenylsulfonyl)- N′-(4-trifluoromethylphenyl)urea (DASU-02), a compound that inhibits cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl−secretion, reduced Iscby 29 ± 7 and 34 ± 11 μA/cm2, respectively. Two additional diarylsulfonylurea (DASU)-based compounds were evaluated for their effects on enterotoxin-stimulated secretion. The rank order of potency for inhibition by these three closely related DASU structures was identical to that observed for human CFTR. The degree of inhibition by each of these compounds was similar for both STa and LT. The structure- and concentration-dependent inhibition shown indicates that CFTR mediates both STa- and LT-stimulated colonic secretion. Similar structure-dependent inhibitory effects were observed in forskolin-stimulated rat colonic epithelium. Thus DASUs compose a family of inhibitors that may be of therapeutic value for the symptomatic treatment of diarrhea resulting from a broad spectrum of causative agents across species.
Metabolism and acid secretory effect of sulfated and nonsulfated gastrin-6 in humans
Authors: Hansen C. Palnæs , Stadil F. , Rehfeld J. F.
Published: December 2017

The antral hormone gastrin is synthesized by processing progastrin into different peptides that stimulate gastric secretion. The effect on acid secretion depends mainly on the metabolic clearance rate of the peptides, but some of them may differ in potency and maximum acid output at similar concentrations in plasma. Sulfated and nonsulfated gastrin-6 are the smallest circulating bioactive gastrins in humans. Their effect and metabolism have now been investigated in nine normal subjects and compared with nonsulfated gastrin-17, a main product of progastrin. Maximum acid output after stimulation with gastrin-17, sulfated gastrin-6, and nonsulfated gastrin-6 were 28.3 ± 2.0, 24.5 ± 2.0 ( P < 0.02), and 19.3 ± 2.3 ( P < 0.05) mmol H+/50 min, respectively, and the corresponding EC50values were 43 ± 6, 24 ± 2 ( P < 0.01), and 25 ± 2 (not significant) pmol/l. The half-life of gastrin-17 was 5.3 ± 0.3 min, the metabolic clearance rate (MCR) was 16.5 ± 1.3 ml · kg−1· min−1, and the apparent volume of distribution (Vd) was 124.3 ± 9.6 ml/kg. The half-lives of sulfated and nonsulfated gastrin-6 were 2.1 ± 0.3 and 1.9 ± 0.3 min, the MCRs were 42.8 ± 3.7 and 139.4 ± 9.6 ml kg−1min−1( P < 0.01), and the Vdwere 139.0 ± 30.5 and 392.0 ± 81.6 ( P < 0.01) ml kg−1. All pharmacokinetic parameters differed significantly from gastrin-17 ( P < 0.01). We conclude that gastrin 6 has a higher potency but a lower efficacy than gastrin-17. The efficacy of gastrin-6 is increased by tyrosine O-sulfation, which also enhances the protection against elimination.
Dietary betaine modifies hepatic metabolism but not renal injury in rat polycystic kidney disease
Authors: Ogborn Malcolm R. , Nitschmann Evan , Bankovic-Calic Neda , Buist Richard , Peeling James
Published: December 2017

We undertook a morphometric and proton nuclear magnetic resonance (1H-NMR) study to test the hypothesis that 1% dietary betaine supplementation would ameliorate renal disease in the heterozygous Han:SPRD- cyrat, a model of polycystic kidney disease (PKD) and progressive chronic renal failure. After 8 wk of pair feeding, betaine had no effect on renal cystic change, renal interstitial fibrosis, serum creatinine, serum cholesterol, or serum triglycerides.1H-NMR spectroscopy of renal tissue revealed no change in renal osmolytes, including betaine, or renal content of other organic anions in response to diet.1H-NMR spectroscopy of hepatic tissue performed to explore the metabolic fate of ingested betaine revealed that heterozygous animals fed the control diet had elevated hepatic levels of gluconeogenic amino acids, increased β-hydroxybutyrate, and increased levels of some citric acid cycle metabolites compared with animals without renal disease. Betaine supplementation eliminated these changes. Chronic renal failure in the Han:SPRD- cy rat is associated with disturbances of hepatic metabolism that can be corrected with betaine therapy, suggesting the presence of a reversible methylation defect in this form of chronic renal failure.