bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of sham feeding-stimulated acid secretion in dogs by immunoneutralization of gastrin
Authors: Kovacs T. O. , Lloyd K. C. , Lawson D. C. , Pappas T. N. , Walsh J. H.
Published: December 2017

A monoclonal antibody to gastrin was used to study the role of circulating gastrin in mediating acid secretion stimulated by sham feeding in dogs. On separate days, four conscious, fasted, adult mongrel dogs with esophageal and gastric fistulae were pretreated intravenously with either 7 mg of gastrin monoclonal antibody (MAb 28.2), 7 mg of keyhole limpet hemocyanin monoclonal antibody as control, or 12.5 micrograms/kg atropine sulfate. Thirty minutes later, acid secretion was stimulated first by sham feeding for 5 min, then, 60 min later, by an intravenous infusion of a maximum stimulatory dose of histamine (40 micrograms/kg) for 60 min, and after returning to basal, by intravenous infusion of a submaximal stimulatory dose of gastrin (200 pmol.kg-1.h-1) for 60 min. Acid output from secretions collected every 15 min by gravity drainage was determined by titration to pH 7.0 with 0.2 N NaOH. Sham feeding-stimulated acid output (17.7 +/- 5.5 mmol/h) was significantly inhibited by administration of either MAb 28.2 (0 mmol/h) or atropine (1.7 +/- 1.1 mmol/h). Histamine-stimulated acid output (19.6 +/- 3.4 mmol/h) was not reduced by either pretreatment. Gastrin-stimulated acid output (3.9 +/- 0.6 mmol/h) was significantly reduced only by pretreatment with MAb 28.2 (0.1 +/- 0.1 mmol/h) and not by atropine (2.2 +/- 1.4 mmol/h). A background intravenous infusion of pentagastrin (0.5 microgram.kg-1.h-1) restored sham feeding-stimulated acid output blocked by administration of MAb 28.2, although the intrinsic acid response to sham feeding could not be seen with the background pentagastrin infusion. Furthermore, the plasma gastrin response to sham feeding was not blocked by atropine pretreatment. Because immunoneutralization of both gastrin and cholinergic blockade significantly inhibited acid output during sham feeding, circulating gastrin and cholinergic pathways are involved in mediating the cephalic phase of gastric acid secretion in dogs.
Gastrogastric reflexes regulating gastric tone and their relationship to perception
Authors: Villanova N. , Azpiroz F. , Malagelada J. R.
Published: December 2017

Our aim was to investigate in humans the gastrogastric reflexes that regulate gastric tone and their relationship to perception. In nine healthy subjects, liquid distension (in 100-ml steps), warm stimuli (in 3 degrees C increments), and cold stimuli (in 6 degrees C decrements) were randomly applied in the stomach for 3 min at 8-min intervals. Gastric tone was measured as isobaric volume changes of air by a barostat, and perception was scored by a graded (0-6) questionnaire. Liquid accommodation produced an additional expansion of isobaric air maintained by the barostat (51 +/- 13 ml with 100 ml of liquid filling, P < 0.05), but this effect became inconsistent with further filling. An accommodation-like reflex was best evidenced by warm stimulation below the discomfort threshold (58 +/- 13 ml relaxation at 47 +/- 1 degrees C, P < 0.05). By contrast, cooling below discomfort induced a reflex contraction (-62 +/- 22 ml change at 18 +/- 2 degrees C, P < 0.05). In conclusion, gastric tone, i.e., accommodation and contraction, is modulated by a net of reflexes that arise from the proper wall of the stomach below the discomfort threshold.
IGF-I induces collagen and IGFBP-5 mRNA in rat intestinal smooth muscle
Authors: Zimmermann E. M. , Li L. , Hou Y. T. , Cannon M. , Christman G. M. , Bitar K. N.
Published: December 2017

Insulin-like growth factor (IGF) binding protein 5 (IGFBP-5) mRNA was studied in intestines of rats with peptidoglycan-polysaccharide enterocolitis by Northern analysis and in situ hybridization. IGFBP-5 mRNA was increased 2.4 ± 0.5-fold in inflamed rat colon compared with controls and was highly expressed in smooth muscle. Cultured rat intestinal smooth muscle cells were used to study the regulation of IGFBP-5 and type I collagen synthesis. IGF-I (100 ng/ml) increased IGFBP-5 mRNA (1.9 ± 0.1-fold) and collagen type α1(I) mRNA (1.6 ± 0.2-fold) in cultured smooth muscle cells. IGF-I induced a dose- and time-dependent increase in IGFBP-5 in conditioned medium by Western ligand blot and by immunoblot. IGF-I did not affect the IGFBP-5 mRNA decay rate after transcriptional blockade. Cycloheximide abolished IGFBP-5 mRNA. In conclusion, IGFBP-5 mRNA is expressed by intestinal smooth muscle and is increased during chronic inflammation. IGF-I increases IGFBP-5 and collagen mRNAs in intestinal smooth muscle cells.
Mechanism of inhibition of Na+-glucose cotransport in the chronically inflamed rabbit ileum
Authors: Sundaram U. , Wisel S. , Rajendren V. M. , West A. B.
Published: December 2017

In a rabbit model of chronic ileal inflammation, we previously demonstrated that coupled NaCl absorption was reduced because of an inhibition of Cl−/[Formula: see text]but not Na+/H+exchange on the brush-border membrane (BBM) of villus cells. In this study we determined the alterations in Na+-stimulated glucose [Na+- O-methyl-d-glucose (Na+-OMG)] absorption during chronic ileitis. Na+-OMG uptake was reduced in villus cells from the chronically inflamed ileum. Na+-K+-adenosinetriphosphatase (ATPase), which provides the favorable Na+gradient for this cotransporter in intact cells, was found to be reduced also. However, in villus cell BBM vesicles from the inflamed ileum Na+-OMG uptake was reduced as well, suggesting an effect at the level of the cotransporter itself. Kinetic studies demonstrated that Na+-OMG uptake in the inflamed ileum was inhibited by a decrease in the maximal rate of uptake for OMG without a change in the affinity. Analysis of steady-state mRNA and immunoreactive protein levels of this cotransporter demonstrates reduced expression. Thus Na+-glucose cotransport was inhibited in the chronically inflamed ileum, and the inhibition was secondary to a decrease in the number of cotransporters and not solely secondary to an inhibition of Na+-K+-ATPase or altered affinity for glucose.
Pentoxifylline blocks hepatic stellate cell activation independently of phosphodiesterase inhibitory activity
Authors: Lee Kwan S. , Cottam Howard B. , Houglum Karl , Wasson D. Bruce , Carson Dennis , Chojkier Mario
Published: December 2017

Activated, but not quiescent, hepatic stellate cells (lipocytes) have a high level of collagen type I and smooth muscle actin (SMA) gene expression. Therefore, stellate cell activation is a critical step in hepatic fibrosis. The mechanisms leading to stellate cell activation in vivo are unknown. The characteristic hepatic oxidative stress cascade induced in rats by CCl4markedly stimulated stellate cell entry into S phase, nuclear factor (NF)-κB activity, and c- myb expression. These changes were prevented by pentoxifylline, which also decreased CCl4-induced hepatic injury. As expected, cAMP-mediated phosphorylation of CREB-Ser133was induced in vivo in stellate cells by pentoxifylline but not by its metabolite 5, an N-1 carboxypropyl derivative, which lacks phosphodiesterase inhibitory activity. Stellate cell nuclear extracts from CCl4-treated, but not from control, animals formed a complex with the critical promoter E box of the α-SMA gene, which was disrupted by c- myb antibodies and competed with by c- myb cognate DNA. Treatment with pentoxifylline or metabolite 5 prevented the molecular abnormalities characteristic of stellate cell activation induced by CCl4. These results suggest that induction of c- myb plays an important role in the in vivo activation of stellate cells. Pentoxifylline blocks stellate cell activation in vivo independently of its inhibitory effects on phosphodiesterases by interfering with the oxidative stress cascade and the activation of NF-κB and c- myb.
Cellular pathways mediating tachykinin-evoked secretomotor responses in guinea pig ileum
Authors: MacNaughton W. , Moore B. , Vanner S.
Published: December 2017

This study characterized tachykinin-evoked secretomotor responses in in vitro submucosal and mucosal-submucosal preparations of the guinea pig ileum using combined intracellular and Ussing chamber recording techniques. Superfusion of endogenous tachykinins substance P (SP), neurokinin A (NKA), and neurokinin B depolarized single submucosal neurons and evoked increased short-circuit current ( I sc) responses in Ussing chamber preparations. The NK1-receptor agonist [Sar9,Met(O2)11]SP [50% effective concentration (EC50) = 2 nM] depolarized all submucosal neurons examined. The NK3-receptor agonist senktide (EC50 = 20 nM) depolarized ∼50% of neurons examined, whereas the NK2-receptor agonist [Ala5,β-Ala8]NKA-(4—10) had no effect on membrane potential. [Sar9,Met(O2)11]SP and senktide evoked similar increases in I sc that were tetrodotoxin sensitive (91 and 100%, respectively) and were selectively blocked by the NK1antagonist CP-99,994 and the NK3antagonist SR-142801, respectively. Capsaicin-evoked increases in I sc were significantly inhibited (54%, P < 0.05) by CP-99,994 but not by SR-142801. Neither antagonist inhibited slow excitatory postsynaptic potentials. These findings suggest that tachykinin-evoked secretion in guinea pig ileum is mediated by NK1 and NK3 receptors on submucosal secretomotor neurons and that capsaicin-sensitive nerves release tachykinin(s) that activate the NK1 receptors.
Amino acid use by the gastrointestinal tract of sheep given lucerne forage
Authors: MacRae John C. , Bruce Les A. , Brown David S. , Calder A. Graham
Published: December 2017

Essential amino acid (EAA) utilization by gastrointestinal tract (GIT) tissues has been investigated in sheep given 800 and 1,200 g/day lucerne pellets. Animals prepared with indwelling catheters into the aorta and the portal drained viscera plus cannulas into the small intestine were infused with mixed U-13C-labeled amino acid or [1-13C]leucine tracers into the jugular vein or directly into the small intestine. GIT sequestration of EAA from arterial and luminal AA pools was determined from tracer and tracee arterioportal concentration differences at both levels of intake. Proportional tracer13C-labeled EAA extraction of the arterial supply, on first pass across the GIT during jugular infusion, ranged from 0.063 for histidine to 0.126 for leucine. Recovery of intestinally infused tracer13C-EAA at the portal vein ranged from 0.61 for histidine to 0.83 for valine. These data were independent of intake. Calculated rates of tracee sequestration by GIT tissues represented 0.45–0.65 of whole body EAA flux, except for histidine, for which the values were much lower (0.25–0.32). With the exception of phenylalanine, more than 0.8 of the EAA used by the GIT was extracted from circulating blood, thus calling into question the theory that GIT tissues make preferential use of EAA during absorptive metabolism, restricting supply to peripheral tissues such as skeletal muscle (growth) or mammary glands (lactation). Instead the GIT seems to compete very successfully with these tissues for circulating blood EAA.
Stenosis of a portacaval anastomosis affects circadian locomotor activity in the rat: a multivariable analysis
Authors: Córdoba Juan , Dupuis Joseé , Gottstein Jeanne , Blei Andrés T.
Published: December 2017

The study of hepatic encephalopathy is limited by the lack of standardized experimental models to assess behavior. We have shown that rats continuously monitored while running on a wheel show abnormalities of the circadian rhythm of locomotor activity after portacaval anastomosis (PCA), such that entrainment of running activity to the light-dark cycle is severely impaired. To identify factors that affect postoperative circadian behavior, we have performed a multivariable analysis of 69 sham-operated controls and 107 rats after PCA. Our results indicate that shunt stenosis, as determined by the pressure gradient from the splenic pulp to the inferior vena cava, ameliorated the postoperative deterioration of the circadian rhythm. In addition, postoperative behavior was affected by preoperative performance, diet, and gender. Postoperative body weight gain, spleen weight, and liver atrophy did not impact this model. Because shunt stenosis is known to ameliorate hepatic encephalopathy in humans, our findings support the validity of this behavioral end point as a correlate of hepatic encephalopathy. Measurement of the pressure gradient across the anastomosis and achievement of sufficient preoperative entrainment appear critical for the standardization of the model.
Dexamethasone suppresses iNOS gene expression by upregulating I-κBα and inhibiting NF-κB
Authors: De Vera Michael E. , Taylor Bradley S. , Wang Qi , Shapiro Richard A. , Billiar Timothy R. , Geller David A.
Published: December 2017

Cytokine-stimulated inducible nitric oxide synthase (iNOS) gene expression is dependent on nuclear factor-κB (NF-κB) activation and is suppressed by glucocorticoids (GC). In this study we examined the molecular mechanisms of GC inhibition of iNOS expression in rat hepatocytes. Combinations of tumor necrosis factor-α, interleukin-1β, and interferon-γ (cytokine mixture CM) induced high levels of iNOS mRNA and NO synthesis. The synthetic GC dexamethasone markedly repressed iNOS mRNA and protein expression, and nuclear run-on assays showed that this inhibition was occurring at the level of transcription. In addition, transfection studies showed that CM-stimulated activity of a 1.6-kb murine iNOS promoter fragment linked upstream of luciferase was suppressed by dexamethasone. Electromobility shift assays demonstrated that CM induced the appearance of an NF-κB complex composed of p50 and p65 subunits; the addition of dexamethasone markedly decreased this band shift. I-κBα expression was decreased by CM and upregulated in the presence of dexamethasone. Subsequently, nuclear p65 levels were decreased by dexamethasone compared with CM-treated cells. Thus GC repress NF-κB DNA-binding activity in rat hepatocytes in part through the upregulation of its inhibitor I-κBα. These data indicate that one mechanism by which GC block iNOS expression is through the inhibition of NF-κB activation resulting in decreased iNOS transcription.
Modulation of P-selectin expression in the postischemic intestinal microvasculature
Authors: Eppihimer Michael J. , Russell Janice , Anderson Donald C. , Epstein Charles J. , Laroux Stephan , Granger D. Neil
Published: December 2017

The dual radiolabeled monoclonal antibody technique was used to 1) define the magnitude and kinetics of P-selectin expression in murine small intestine exposed to ischemia-reperfusion (I/R), and 2) determine the factor(s) responsible for initiating this response. Within 10 min after release of a 20-min arterial occlusion, intestinal P-selectin expression increased two- to threefold compared with control values. Peak (4-fold) expression of P-selectin was noted at 5 h after reperfusion, returning to the control value at 24 h. The early (10–30 min) I/R-induced upregulation of P-selectin appears to reflect mobilization of a preformed pool of the adhesion molecule, whereas the later (5 h) rise appears to be transcription dependent. The early increase in P-selectin expression was not inhibited by pretreatment with either oxypurinol (inhibits xanthine oxidase), diphenhydramine (H1-receptor antagonist), or MK-571 (leukotriene C4/D4antagonist), nor was it blunted in transgenic mice expressing three times the normal level of copper-zinc superoxide dismutase or in mast cell-deficient mice. However, significant inhibition was noted after treatment with either MK-886 (5-lipoxygenase inhibitor) or a nitric oxide (NO) donor (diethylenetriamine/NO). These findings indicate that the early I/R-induced increase in intestinal P-selectin expression is mediated by a 5-lipoxygenase-dependent NO-inhibitable mechanism.
Parenteral nutrition selectively decreases protein synthesis in the small intestine
Authors: Dudley Mary A. , Wykes Linda J. , Dudley Alden W. , Burrin Douglas G. , Nichols Buford L. , Rosenberger Judy , Jahoor Farook , Heird William C. , Reeds Peter J.
Published: December 2017

We investigated the effects of an elemental diet fed parenterally or enterally on total mucosal protein and lactase phlorizin hydrolase (LPH) synthesis. Catheters were placed in the stomach, jugular vein, and carotid artery of 12 3-day-old pigs. Half of the animals were given an elemental regimen enterally and the other half parenterally. Six days later, animals were infused intravenously with [2H3]leucine for 6 h and killed, and the midjejunum of each animal was collected for analysis. The weight of the midjejunum was 8 ± 1.5 and 17 ± 1.6 g in parenterally fed and enterally fed piglets, respectively. LPH activities (μmol ⋅ min−1⋅ g protein−1) were significantly higher in parenterally vs. enterally fed piglets. Total small intestinal LPH activities were lower in parenterally vs. enterally fed animals. The abundance of LPH mRNA relative to elongation factor-1α mRNA was not different between groups. The fractional synthesis rate of total mucosal protein and LPH was significantly lower in parenterally fed animals (67 ± 7 and 66 ± 7%/day, respectively) than in enterally fed animals (96 ± 7 and 90 ± 6%/day, respectively). The absolute synthesis rate (the amount of protein synthesized per gram of mucosa) of total mucosal protein was significantly lower in parenterally fed than in enterally fed piglets. However, the absolute synthesis rate of LPH was unaffected by the route of nutrient administration. These results suggest that the small intestine partially compensates for the effects of parenteral feeding by maintaining the absolute synthesis rate of LPH at the same levels as in enterally fed animals.
Subcellular kinetics of early trypsinogen activation in acute rodent pancreatitis
Authors: Mithöfer Kai , Castillo Carlos Fernández-Del , Rattner David , Warshaw Andrew L.
Published: December 2017

To investigate the debated role of intracellular trypsinogen activation and its relation to lysosomal enzyme redistribution in the pathogenesis of acute pancreatitis, rats were infused with the cholecystokinin analog caerulein at 5 μg ⋅ kg−1⋅ h−1for intervals up to 3 h, and the changes were contrasted with those in animals receiving saline or 0.25 μg ⋅ kg−1⋅ h−1caerulein. Saline or 0.25 μg ⋅ kg−1⋅ h−1caerulein did not induce significant changes. In contrast, 5 μg ⋅ kg−1⋅ h−1caerulein caused significant hyperamylasemia and pancreatic edema within 30 min. Pancreatic content of trypsinogen activation peptide (TAP) increased continuously (significant within 15 min). TAP generation was predominantly located in the zymogen fraction during the first hour but expanded to other intracellular compartments thereafter. Cathepsin B activity in the zymogen compartment increased continuously throughout the experiments and correlated significantly with TAP generation in the same compartment. Total trypsinogen content increased to 143% with marked interstitial trypsinogen accumulation after 3 h. Supramaximal caerulein stimulation causes trypsinogen activation by 15 min that originates in the zymogen compartment and is associated with increasing cathepsin B activity in this subcellular compartment. However, a much larger pool of trypsinogen survives and accumulates in the extracellular space and may become critical in the evolution of necrotizing pancreatitis.
Polyamine metabolism of rat gastric mucosa after oral administration of hypertonic sodium chloride solution
Authors: Otani Kenjiro , Yano Yoshihisa , Hasuma Tadayoshi , Arakawa Tetsuo , Kobayashi Kenzo , Matsui-Yuasa Isao , Otani Shuzo
Published: December 2017

Oral administration of 1 ml of 3.42 M NaCl solution to rats induced spermidine/spermine N1-acetyltransferase (SSAT) activity in gastric mucosa as well as ornithine decarboxylase (ODC) activity. SSAT activity increased and peaked at 5 h and again at 7 h, whereas ODC activity peaked at 6 h. SSAT mRNA also increased after 3.42 M NaCl administration to an extent similar to the increase in SSAT activity at 5 h. Intracellular putrescine level and DNA synthesis were increased by NaCl administration. A polyamine oxidase inhibitor, N, N′-bis(2,3-butadienyl)-1,4-butanediamine (MDL-72527), but not an ODC inhibitor, α-difluoromethylornithine (DFMO), inhibited the increases in putrescine level and DNA synthesis at 5 h. The inhibition of DNA synthesis by MDL-72527 was reversed by putrescine administration. In contrast, both MDL-72527 and DFMO inhibited the increase in putrescine level and DNA synthesis at 16.5 h. These findings suggest that putrescine produced from preexistent spermidine by SSAT is responsible for the initial DNA synthesis after mucosal injury induced by NaCl and that both SSAT and ODC are involved in formation of putrescine, which is required for subsequent DNA synthesis.
Muscarinic modulation of voltage-dependent Ca2+channels in insulin-secreting HIT-T15 cells
Authors: Love Jeffrey A. , Richards Neil W. , Owyang Chung , Dawson David C.
Published: December 2017

Potentiation of insulin secretion from pancreatic β-cells by acetylcholine requires ongoing cyclic electrical activity initiated by other depolarizing secretagogues. Patch-clamp recordings in glucose-free solutions were made from the clonal β-cell line HIT-T15 to determine whether the muscarinic agonist bethanechol (BCh) modulated voltage-dependent Ca2+channels independent of effects on membrane potential. Only high-threshold, dihydropyridine-sensitive (L-type) Ca2+channels with a mean conductance of 26 pS were observed in cell-attached patches. BCh (100 μM) caused a two- to threefold increase in both fractional open time and mean current of single Ca2+channels. These changes resulted from a 44% decrease in the longer of two apparent mean closed times and a 25% increase in the mean open time. Similar BCh-stimulated increases in macroscopic Ca2+currents were recorded in whole cell, perforated-patch recordings. The role of protein kinase C (PKC) in the muscarinic activation of Ca2+channels was tested using a variety of PKC activators and inhibitors. Acute application of either the active phorbol ester phorbol 12-myristate 13-acetate (PMA) or the membrane-permeable diacylglycerol analog 1,2-didecanoyl- rac-glycerol mimicked the effects of BCh, whereas an inactive phorbol (4α) had no effect. Depletion of PKC activity by chronic exposure to PMA or acute application of the PKC inhibitor staurosporine greatly reduced or abolished muscarinic activation of Ca2+channels. These results are consistent with muscarinic activation of L-type, voltage-dependent Ca2+channels mediated in large part by PKC.
The primary and final effector mechanisms required for kinin-induced epithelial chloride secretion
Authors: Cuthbert Alan W. , Huxley Clare
Published: December 2017

The short-circuit current technique was used to examine the effects of N 2-l-lysylbradykinin (LBK) on chloride secretion in the mucosae of the mouse intestine. It was found to be a potent chloride secretagogue in the mucosa lining the colon, jejunum, and cecum, as it is in most mammals, with 2 nM being sufficient to cause half-maximal secretion. The extent of the responses was in the order cecum > colon > jejunum. In cystic fibrosis (CF) null mice, with no CF transmembrane conductance regulator (CFTR) chloride channels, LBK caused no chloride secretion, but transporting activities for other ions were revealed. Introduction of the human CF gene into the genome of CF null mice at the zygote stage restored the chloride secretory activity of LBK, with only minor differences in potency. In mice in which the kinin B2 receptor gene had been disrupted, LBK had no effect, whereas the responses to forskolin were unchanged. Thus the acute effects of kinins on chloride secretion depend uniquely on kinin B2receptors and CFTR chloride channels, which form the primary and final effector mechanisms of the secretory process.
Polyamines are required for microtubule formation during gastric mucosal healing
Authors: Banan Ali , McCormack Shirley A. , Johnson Leonard R.
Published: December 2017

Polyamines are essential for the repair of gastric and duodenal erosions. Concentrated NaCl (3.4 M) given intragastrically damages the oxyntic gland mucosa and increases the activity of gastric mucosal ornithine decarboxylase (ODC), the first rate-limiting enzyme in polyamine synthesis. The nature of the process of restitution of damaged mucosa is not well known, except that cell migration and the actin cytoskeleton play a prominent role. Microtubules are cytoskeletal components essential for cell migration. The present investigation determines the relationship between polyamines, the distribution of microtubules, and gastric healing in mucosa damaged with hypertonic NaCl solution. Rats were fasted for 22 h and then given 1.0 ml of 3.4 M NaCl intragastrically. Animals were killed 1, 2, 4, 8, and 10 h after 3.4 M NaCl. The oxyntic gland mucosa was removed, and tubulin was visualized by immunofluorescence. Microtubule density was increased around and below the damaged mucosa in the upper one-third of the glandular epithelium at 2 and 4 h and returned to near control levels by 10 h. In rats damaged with 3.4 M NaCl and pretreated intraperitoneally with α-difluoromethylornithine (DFMO), a specific inhibitor of ODC, microtubule content was reduced significantly at all time points after NaCl treatment. Addition of spermidine after pretreatment with DFMO and 3.4 M NaCl significantly prevented the effects of DFMO. Colchicine, a potent microtubule-disrupting drug, significantly delayed normal gastric mucosal healing with no effect on ODC activity. These data show that polyamines influence the distribution of microtubules during damage in vivo and indicate a partial mechanism for the dependency of mucosal healing on polyamines.
Restoration by intratracheal gene transfer of bicarbonate secretion in cystic fibrosis mouse gallbladder
Authors: Curtis C. M. , Martin L. C. , Higgins C. F. , Colledge W. H. , Hickman M. E. , Evans M. J. , MacVinish L. J. , Cuthbert A. W.
Published: December 2017

Gallbladders from cystic fibrosis (CF) mice ( Cftrtm1Cam and Cftrtm2Cam ) were examined with the short-circuit current technique. The tissues failed to show any electrogenic anion transport in response to forskolin (cAMP stimulus) but responded to the Ca2+ ionophore ionomycin. Administration of the plasmid pTrial10-CFTR2 complexed with cationic liposomes {3β-[ N-(dimethylaminoethane)-carbamoyl]cholesterol andl-α-phosphatidylethanolamine dioleolyl} to the airways restored the phenotype of CF gallbladders to that of the wild type, but did not do so when given orally. Formation of human CFTR mRNA in gallbladders of transfected CF null mice was demonstrated. Using the reporter genes pCMV- luc and pCMV- LacZ, we showed that 1) the intratracheal route was more effective than the oral, intravenous, intramuscular, subcutaneous, or intraperitoneal routes in expressing luciferase activity in the gallbladder and 2) β-galactosidase staining after pCMV- LacZ was confined to the columnar epithelium lining the gallbladder without any discernible activity in its smooth muscle. The discovery of an unusual route for gene transfer to the biliary system may give useful insight into counteracting the consequences of biliary fibrosis in human CF patients.
Postnatal changes in gut hemodynamics: a possible role for substance P
Authors: Nowicki Philip T.
Published: December 2017

Studies were conducted in young postnatal swine to determine if substance P (SP) participates in the regulation of postnatal intestinal hemodynamics and oxygenation. SP was present in homogenates of whole intestine from postnatal swine in an age-dependent manner as follows: 1 day old and never fed, 126 ± 35; 3 days old and fasted, 148 ± 30; and 14 days old, 51 ± 10 pg/mg protein ( P < 0.01, 14- vs. 1- or 3-day-olds). Phenylephrine-precontracted rings of mesenteric artery from 3-day-old subjects mounted for tension recording within buffer-filled myographs demonstrated brisk relaxation in response to SP (EC50, 2 × 10−10M). This relaxation was eliminated by mechanical removal of the endothelium or blockade with the l-arginine analog NG-monomethyl-l-arginine (l-NMMA) and was significantly attenuated by pretreatment with N-acyl-l-Trp-3,5-bis-(trifluoromethyl) benzyl ester (NATB), a highly selective NK-1 receptor antagonist (pA25 × 10−10M). Infusion of exogenous SP into the mesenteric artery of innervated in vivo gut loops reduced intestinal vascular resistance 35% and increased tissue oxygen uptake 40% in both 3- and 14-day-old subjects. By contrast, blockade of the NK-1 receptor for SP with NATB increased intestinal vascular resistance 19% in 3-day-old subjects but only 5% in 14-day-old subjects ( P < 0.01). SP-induced changes in gut vascular resistance were significantly attenuated by prior coinfusion of NATB orl-NMMA, indicating that the peptide exerted this vascular effect via the NK-1 receptor, which is linked to endothelial cell nitric oxide synthase. Both NATB andl-NMMA attenuated flow-induced dilation within pump-perfused in vitro gut loops from 3-day-old subjects. SP appears to participate in the regulation of the newborn intestinal circulation, especially during the first days after birth.
IV. Neural regulation of gastrointestinal smooth muscle
Authors: Sanders Kenton M.
Published: December 2017

G protein-coupled receptors receive many of the neural, hormonal, and paracrine inputs to gastrointestinal (GI) smooth muscle cells. This article examines the major G protein-coupled receptors, G proteins, and effectors that mediate responses to enteric neuromuscular transmitters. Excitatory transmitters primarily couple through Gq/11 and Gi/Goproteins and elicit responses via formation of inositol trisphosphate and diacylglycerol and inhibition of adenylyl cyclase. Several inhibitory transmitters couple through Gs and activation of adenylyl cyclase. There are interesting examples, however, of inhibitory transmitters apparently using pathways regulated by Gq/11 to elicit responses by localized Ca2+ release and activation of Ca2+-dependent ion channels. G protein-coupled receptors may also be differentially expressed by smooth muscle cells and interstitial cells of Cajal, which may increase the diversity of responses and allow specialized innervation of GI muscle tissues.
IGF-I stimulates intestinal muscle cell growth by activating distinct PI 3-kinase and MAP kinase pathways
Authors: Kuemmerle John F. , Bushman Toni L.
Published: December 2017

Insulin-like growth factor I (IGF-I), acting via its cognate receptor, plays an autocrine role in the regulation of growth of intestinal muscle cells. In the present study the signaling pathways mediating the growth effects of IGF-I were characterized in cultured human intestinal smooth muscle cells. Growth induced by a maximally effective concentration of IGF-I (100 nM), measured as [3H]thymidine incorporation, was only partially inhibited by LY-294002 [phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor] or PD-98059 [mitogen-activated protein (MAP) kinase kinase (MEK) inhibitor] (86 ± 7% and 35 ± 6% inhibition, respectively) alone but was abolished by the two combined (114 ± 18% inhibition), implying the participation of both pathways. IGF-I elicited time- and concentration-dependent increases in PI 3-kinase activity. This effect was inhibited only by LY-294002 (89 ± 12%). IGF-I elicited time- and concentration-dependent phosphorylation of p44/p42 MAP kinase and increased MAP kinase activity. These effects were inhibited only by PD-98059 (78 ± 9% and 98 ± 7%, respectively). We conclude that in human intestinal muscle cells IGF-I activates distinct PI 3-kinase and MAP kinase signaling pathways, which act in conjunction to mediate growth.
Altered sodium-hydrogen exchange activity is a mechanism for acid-induced hyperproliferation in Barrett’s esophagus
Authors: Fitzgerald R. C. , Omary M. B. , Triadafilopoulos G.
Published: December 2017

Acid produces a dynamic effect on the cell phenotype of Barrett’s esophagus (BE) ex vivo. An acid pulse induces hyperproliferation, whereas continuous acid exposure promotes differentiation. To examine the mechanism for acid pulse-induced hyperproliferation, we studied the Na+/H+exchanger (NHE), which plays a role in the control of intracellular pH and cell proliferation. NHE was inhibited pharmacologically in endoscopic BE biopsies using amiloride analogs. Cell proliferation was assessed after pulsed or continuous acid exposure using tritiated thymidine incorporation assays and immunohistochemical analysis of proliferating cell nuclear antigen expression. The NHE-dependent intracellular pH response to an acid pulse was examined by pH-sensitive microfluorimetry using a Barrett’s adenocarcinoma cell line TE7. NHE inhibition significantly reduced the hyperproliferative acid-pulse effect. Furthermore, the acid-pulse activation of NHE occurred via increased transporter activity (22Na uptake) without any change in NHE-1 protein levels. Inhibition of protein kinase C (PKC), an NHE activator, also reduced the hyperproliferative response. The response of TE7 cells to an acid pulse was similar to that of BE biopsies in terms of cell proliferation and NHE and PKC dependence. Acid-pulse exposure of TE7 cells resulted in intracellular acidification followed by reneutralization to an intracellular pH greater than preacidosis values. We conclude that NHE may mediate the hyperproliferative response of BE to an acid pulse via changes in intracellular pH.
L-FABP and I-FABP expression increase NBD-stearate uptake and cytoplasmic diffusion in L cells
Authors: Murphy Eric J.
Published: December 2017

The effects of intestinal and liver fatty acid binding protein (I- and L-FABP, respectively) expression on single-cell fatty acid uptake, internalization, and cytoplasmic diffusion were determined in transfected L cell fibroblasts. These parameters were measured using the nonesterifiable fluorescent fatty acid probe 12- N-methyl-(7-nitrobenz-2-oxa-1,3-diazol)aminostearate (NBD-stearate) and fluorescence digital imaging. In single-cell fluorescence imaging experiments, L-FABP-expressing cells, but not I-FABP-expressing cells, increased NBD-stearate uptake 1.7-fold compared with control cells. Both I- and L-FABP increased the cytoplasmic diffusion rate of the internalized NBD-stearate 2.6- and 1.9-fold, respectively, compared with control cells. However, increased NBD-stearate lateral membrane mobility was observed only in L-FABP-expressing cells. After incubation of the cells with 4 μM NBD-stearate at 37°C for 30 min, fluorescence deconvolution imaging indicated that NBD-stearate was localized primarily into lipid droplets in all cell lines. The differential effect of these proteins on fatty acid uptake and intracellular trafficking in single cells illustrates a possible difference in the physiological function of I- and L-FABP in intact cells.
Effects of endotoxin on gastric injury from luminal irritants in rats: potential roles of nitric oxide
Authors: Mercer David W. , Castaneda Antonio A. , Denning Jeremy W. , Chang Lily , Russell Diane H.
Published: December 2017

The expression and function of inducible nitric oxide synthase (iNOS) in the stomach is unclear. This study assessed the effects of endotoxin on rat gastric iNOS expression and its role in gastric injury from luminal irritants. In conscious rats, a 5-h treatment with intraperitoneal lipopolysaccharide (LPS; 1–20 mg/kg) dose dependently increased gastric mucosal iNOS immunoreactivity and increased gastric luminal nitrate and nitrite accumulation (Griess reaction). LPS also increased gastric luminal fluid accumulation and reduced macroscopic gastric injury from orogastric acidified ethanol. Aminoguanidine (45 mg/kg) did not prevent LPS-induced gastroprotection or gastric fluid accumulation. NG-nitro-l-arginine methyl ester increased gastric luminal fluid and caused macroscopic gastric injury when given with LPS. Using an anesthetized preparation followed by removal of luminal fluid, LPS reduced gastric mucosal blood flow and exacerbated gastric injury from either acidified ethanol or acidified taurocholate, an effect that was negated by aminoguanidine. These data indicate that in conscious rats, the gastroprotective effect of endotoxin is dependent on constitutive NOS but not iNOS activity. However, the inducible isoform participates in the ability of endotoxin to exacerbate gastric injury from luminal irritants in the anesthetized rat.
Organization of intrinsic cholinergic neurons projecting within submucosal plexus of guinea pig ileum
Authors: Moore B. A. , Vanner S.
Published: December 2017

Electrophysiological techniques were employed to examine the organization of the projections of submucosal neurons in the submucosal plexus of guinea pig ileum. These neurons were activated by focal pressure-pulse application of 5-hydroxytryptamine (5-HT) to single ganglia in submucosal preparations in vitro, and resulting fast excitatory postsynaptic potentials (EPSPs) were recorded intracellularly in S-type neurons. 5-HT-evoked fast EPSPs were blocked by TTX, hexamethonium, and ICS-205-930 (tropisetron). 5-HT was applied either directly to the ganglion containing the neuron recorded intracellularly or to adjacent ganglia positioned at increasing distances on either side of the impaled cell in circumferential or longitudinal orientations. All S-type neurons recorded in this study ( n = 103) received nicotinic fast EPSPs from cholinergic neurons when 5-HT was applied directly to the ganglion containing the impaled neuron. Stimulation of adjacent ganglia also evoked nicotinic fast EPSPs, but the number of neurons that received this input decreased as the distance between the stimulus and the impaled cell increased. Maximal projections were 3 mm in the circumferential and orad-to-aborad orientations. There were no significant projections in the aborad-to-orad direction. These findings suggest that S-type neurons in the submucosal plexus are innervated by intrinsic cholinergic neurons that project over relatively short distances and have a distinct orad-to-aborad polarity.
Differential 5-HT3 mediation of human gastrocolonic response and colonic peristaltic reflex
Authors: Björnsson Einar S. , Chey William D. , Ladabaum Uri , Woods Michelle L. , Hooper Forrest G. , Owyang Chung , Hasler William L.
Published: December 2017

Colonic motor function is modulated by extended and local neural reflexes involving unknown mediators. To test the role of serotonin (5-HT3) pathways, increases in colonic tone during antral distension and duodenal lipid perfusion (gastrocolonic responses) and changes in orad and caudad colonic tone in response to local colonic distension (peristaltic reflex) were measured after double-blind granisetron (10 μg/kg) or placebo infusion in healthy human volunteers. Antral distension evoked increases in colonic tone, which were blunted by granisetron ( P < 0.05) without effects on antral compliance. Intraduodenal lipid perfusion also evoked increased colonic tone, which was reduced by granisetron ( P < 0.05). In contrast, orad colonic contractions and caudad relaxations and contractions during colonic distension were unaffected by granisetron. In conclusion, 5-HT3 receptor antagonism blunts both the mechano- and chemoreceptor components of the human gastrocolonic response without altering antral compliance. In contrast, 5-HT3 pathways play no role in the ascending or descending components of the colonic peristaltic reflex. These findings demonstrate different roles for 5-HT3 receptors in the control of colonic motor function by the proximal gastrointestinal tract and by local neural reflexes.
Stimulation of oxygen uptake by prostaglandin E2is oxygen dependent in perfused rat liver
Authors: Qu Wei , Zhong Zhi , Arteel Gavin E. , Thurman Ronald G.
Published: December 2017

The aim of this study was to determine if the effect of prostaglandin E2(PGE2) on hepatic oxygen uptake was affected by oxygen tension. Livers from fed female Sprague-Dawley rats were perfused at normal or high flow rates (4 or 8 ml ⋅ g−1⋅ min−1) to vary local oxygen tension within the liver lobule. During perfusion at normal flow rates, PGE2(5 μM) infusion increased oxygen uptake by about 50 μmol ⋅ g−1⋅ h−1; however, when livers were perfused at high flow rates, the increase was nearly twice as large. Simultaneously, glucose output was increased rapidly by about 50%, whereas glycolysis was decreased about 60%. When flow rate was held constant, increases in oxygen uptake due to PGE2were proportional to oxygen delivery. Infusion of PGE2into livers perfused at normal flow rates increased state 3 rates of oxygen uptake of subsequently isolated mitochondria by about 25%; however, rates were increased 50–75% in mitochondria isolated from livers perfused at high flow rates. Thus it is concluded that PGE2stimulates oxygen uptake via mechanisms regulated by oxygen tension in perfused rat liver. High flow rates also increased basal rates of oxygen uptake: this increase was prevented by inactivation of Kupffer cells with GdCl3. In addition, conditioned medium from Kupffer cells incubated at high oxygen tension (75% oxygen) stimulated oxygen uptake of isolated parenchymal cells by >30% and elevated PGE2production about twofold compared with Kupffer cells exposed to normal air-saturated buffer (21% oxygen). These effects were blocked completely by both indomethacin and nisoldipine. These data support the hypothesis that oxygen stimulates Kupffer cells to release mediators such as PGE2which elevate oxygen consumption in parenchymal cells, possibly by mechanisms involving cyclooxygenase and calcium channels.
Neural mediation of vasoactive intestinal polypeptide inhibitory effect on jejunal alanine absorption
Authors: Barada K. A. , Saadé N. E. , Atweh S. F. , Nassar C. F.
Published: December 2017

It was recently shown that vasoactive intestinal polypeptide (VIP) inhibits rat jejunal alanine absorption, an effect that was significantly reduced by vagotomy. This study assesses the role of capsaicin-sensitive primary afferents (CSPA) and the myenteric plexus in the inhibition of rat jejunal alanine absorption by VIP. Continuous intravenous infusion of VIP (11.2 ng ⋅ kg−1⋅ min−1) reduced alanine absorption by 60% in sham control rats and by 20% in rats neonatally treated with capsaicin ( P < 0.01). In in vitro experiments, VIP decreased alanine uptake by jejunal strips isolated from sham control rats in a dose-dependent manner. In the presence of 40 nM VIP, alanine uptake by full-thickness jejunal strips was reduced by 54% in sham control rats and by 25% in rats neonatally treated with capsaicin ( P < 0.001). On the other hand, VIP reduced alanine uptake by mucosal scrapings by 25% in sham rats compared with 9% reduction in neonatally treated rats. Chemical ablation of the extrinsic innervation and jejunal myenteric plexuses by pretreatment with benzalkonium chloride significantly ( P < 0.001) reduced basal alanine absorption and the inhibitory effect of VIP. Moreover, incubation of intestinal strips with tetrodotoxin and atropine reduced significantly ( P < 0.05) the inhibitory effect of VIP on alanine absorption. These data suggest that VIP exerts its inhibitory effect on alanine absorption through the CSPA fibers and the myenteric plexus. The neuronal circuitry of this inhibitory process may involve cholinergic muscarinic mechanisms.
Identification and functional importance of IL-1 receptors on rat parietal cells
Authors: Schepp Wolfgang , Dehne Kerstin , Herrmuth Hedda , Pfeffer Klaus , Prinz Christian
Published: December 2017

We studied the expression of interleukin-1 (IL-1) receptors and the effect of IL-1β on the function of highly enriched (>97%) rat parietal cells. RT-PCR of parietal cell poly(A)+RNA with primers specific for the rat IL-1 receptor revealed a single 547-kb PCR product highly homologous to the published sequence of the IL-1 receptor. Northern blot analysis of poly(A)+RNA of rat parietal cells and brain revealed a single RNA species of 5.7 kb. Cytochemistry of parietal cell IL-1 receptor was performed with biotinylated recombinant human IL-1β, visualized by avidin-coupled fluorescein. Corresponding to the high degree of parietal cell enrichment, 95% of the cells stained positive. Basal H+production ([14C]aminopyrine accumulation) was not changed by IL-1β (0.25–100 pg/ml) nor was the response to histamine or carbachol when added simultaneously with the cytokine. However, when parietal cells were preincubated with IL-1β (0.5–5 pg/ml) for 10 min before the addition of histamine or carbachol, the response to these secretagogues was reduced by 35 and 67%, respectively. Inhibition by IL-1β was fully reversed by the human recombinant IL-1 receptor antagonist. Preincubation of parietal cells with IL-1β failed to alter histamine-stimulated cAMP production but markedly inhibited carbachol-induced formation ofd- myo-inositol 1,4,5-trisphosphate. In fura 2-loaded, purified parietal cells, 10 min preincubation with IL-1β dramatically reduced the initial transient peak elevation of intracellular Ca2+concentration in response to carbachol. We conclude that rat parietal cells express IL-1 receptors mediating inhibition of H+production. The antisecretory effect of IL-1β may contribute to hypoacidity secondary to acute Helicobacter pylori infection or during chronic colonization by H. pylori preferring the fundic mucosa.
Localization of cyclooxygenase-2 and regulation of its mRNA expression in gastric ulcers in rats
Authors: Takahashi Satoru , Shigeta Jun-Ichi , Inoue Hiroyasu , Tanabe Tadashi , Okabe Susumu
Published: December 2017

It has been reported that cyclooxygenase-2 (COX-2) may play a crucial role in gastric ulcer healing. We examined the localization of COX-2 and the regulation of COX-2 mRNA expression in acetic acid ulcers in rats. PGE2 production was elevated in ulcerated tissue but not in intact tissue. COX-2 mRNA expression was induced in only the ulcerated tissue, and COX-2 protein was found in fibroblasts, monocytes/macrophages, and granulocytes. A selective COX-2 inhibitor inhibited increased PGE2 production by the ulcerated tissue. Interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and transforming growth factor-β1 (TGF-β1) mRNAs were also expressed only in the ulcerated tissue. In a culture of isolated ulcer base, blockade of IL-1β and TNF-α reduced COX-2 mRNA expression and PGE2 production. In contrast, COX-2 mRNA expression and PGE2 production were promoted by prevention of TGF-β1 action. These results indicate that COX-2 protein is highly localized in the base of gastric ulcers in rats and that COX-2 mRNA expression might be regulated positively by IL-1β and TNF-α and negatively by TGF-β1.
V. Genes, lineages, and tissue interactions in the development of the enteric nervous system
Authors: Gershon Michael D.
Published: December 2017

The enteric nervous system is derived from the vagal, rostral-truncal, and sacral levels of the neural crest. Because the crest-derived population that colonizes the bowel contains multipotent cells, terminal differentiation occurs in the gut and is influenced by both the enteric microenvironment and the responsivity of multiple lineages of precursors. Enteric growth factor-receptor combinations, which promote the development of enteric neurons and/or glia in most of the gastrointestinal (GI) tract, include glial cell line-derived neurotrophic factor-GFRα-1-Ret, NT-3-TrkC, a still-to-be-identified neuropoietic cytokine-ciliary neurotrophic factor receptor-α, serotonin (5-HT)-5-HT2B, and LBP110, a 110-kDa laminin-1 binding protein. A qualitatively different effect is shown by the peptide-receptor combination ET-3-ETB, which inhibits neuronal differentiation and appears to prevent the premature differentiation of enteric neurons before colonization of the GI tract has been completed (resulting in aganglionosis of the terminal colon).