bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of duodenal distension on antropyloroduodenal pressures and perception are modified by hyperglycemia
Authors: Lingenfelser T. , Sun W.-M. , Hebbard G. S. , Dent J. , Horowitz M.
Published: December 2017

Marked hyperglycemia (blood glucose ∼15 mmol/l) affects gastrointestinal motor function and modulates the perception of gastrointestinal sensations. The aims of this study were to evaluate the effects of mild hyperglycemia on the perception of, and motor responses to, duodenal distension. Paired studies were done in nine healthy volunteers, during euglycemia (∼4 mmol/l) and mild hyperglycemia (∼10 mmol/l), in randomized order, using a crossover design. Antropyloroduodenal pressures were recorded with a manometric, sleeve-side hole assembly, and proximal duodenal distensions were performed with a flaccid bag. Intrabag volumes were increased at 4-ml increments from 12 to 48 ml, each distension lasting for 2.5 min and separated by 10 min. Perception of the distensions and sensations of fullness, nausea, and hunger were evaluated. Perceptions of distension ( P < 0.001) and fullness ( P < 0.05) were greater and hunger less ( P < 0.001) during hyperglycemia compared with euglycemia. Proximal duodenal distension stimulated pyloric tone ( P < 0.01), isolated pyloric pressure waves ( P < 0.01), and duodenal pressure waves ( P< 0.01). Compared with euglycemia, hyperglycemia was associated with increases in pyloric tone ( P < 0.001), the frequency ( P < 0.05) and amplitude ( P < 0.01) of isolated pyloric pressure waves, and the frequency of duodenal pressure waves ( P < 0.001) in response to duodenal distension. Duodenal compliance was less ( P < 0.05) during hyperglycemia compared with euglycemia, but this did not account for the effects of hyperglycemia on perception. We conclude that both the perception of, and stimulation of pyloric and duodenal pressures by, duodenal distension are increased by mild hyperglycemia. These observations are consistent with the concept that the blood glucose concentration plays a role in the regulation of gastrointestinal motility and sensation.
Interaction of asparagine and EGF in the regulation of ornithine decarboxylase in IEC-6 cells
Authors: Ray Ramesh M. , Viar Mary Jane , Patel Tarun B. , Johnson Leonard R.
Published: December 2017

Our laboratory has shown that asparagine (ASN) stimulates both ornithine decarboxylase (ODC) activity and gene expression in an intestinal epithelial cell line (IEC-6). The effect of ASN is specific, and other A- and N-system amino acids are almost as effective as ASN when added alone. In the present study, epidermal growth factor (EGF) was unable to increase ODC activity in cells maintained in a salt-glucose solution (Earle’s balanced salt solution). However, the addition of ASN (10 mM) in the presence of EGF (30 ng/ml) increased the activity of ODC 0.5- to 4-fold over that stimulated by ASN alone. EGF also showed induction of ODC with glutamine and α-aminoisobutyric acid, but ODC induction was maximum with ASN and EGF. Thus the mechanism of the interaction between ASN and EGF is important for understanding the regulation of ODC under physiological conditions. Therefore, we examined the expression of the ODC gene and those for several protooncogenes under the same conditions. Increased expression of the genes for c-Jun and c-Fos but not for ODC occurred with EGF alone. The addition of ASN did not further increase the expression of the protooncogenes, but the combination of EGF and ASN further increased the expression of ODC over that of ASN alone. Western analysis showed no significant difference in the level of ODC protein in Earle’s balanced salt solution, ASN, EGF, or EGF plus ASN. Addition of cycloheximide during ASN and ASN plus EGF treatment completely inhibited ODC activity without affecting the level of ODC protein. These results indicated that 1) the increased expression of protooncogenes in response to EGF is independent of increases in ODC activity and 2) potentiation between EGF and ASN on ODC activity may not be due to increased gene transcription but to posttranslational regulation and the requirement of ongoing protein synthesis involving a specific factor dependent on ASN.
Paracellular glucose transport plays a minor role in the unanesthetized dog
Authors: Lane John S. , Whang Edward E. , Rigberg David A. , Hines Oscar J. , Kwan David , Zinner Michael J. , McFadden David W. , Diamond Jared , Ashley Stanley W.
Published: December 2017

Traditionally, intestinal glucose absorption was thought to occur through active, carrier-mediated transport. However, proponents of paracellular transport have argued that previous experiments neglected effects of solvent drag coming from high local concentrations of glucose at the brush-border membrane. The purpose of this study was to evaluate glucose absorption in the awake dog under conditions that would maximize any contribution of paracellular transport. Jejunal Thiry-Vella loops were constructed in six female mongrel dogs. After surgical recovery, isotonic buffers containingl-glucose as the probe for paracellular permeability were given over 2-h periods by constant infusion pump. At physiological concentrations ofd-glucose (1–50 mM), the fractional absorption ofl-glucose was only 4–7% of total glucose absorption. Infusion of supraphysiological concentrations (150 mM) of d-glucose,d-maltose, ord-mannitol yielded low-fractional absorptions ofl-glucose (2–5%), so too did complex or nonabsorbable carbohydrates. In all experiments, there was significant fractional water absorption (5–19%), a prerequisite for solvent drag. Therefore, with even up to high concentrations of luminal carbohydrates in the presence of significant water absorption, the relative contribution of paracellular glucose absorption remained low.
Assessment of the mechanism of juxtacrine activation and adhesion of leukocytes in liver microcirculation
Authors: Carvalho-Tavares Juliana , Fox-Robichaud Alison , Kubes Paul
Published: December 2017

Leukotriene C4(LTC4), histamine, and other mediators can induce expression of P-selectin and platelet-activating factor (PAF) on venular endothelium to recruit leukocytes in vivo and in vitro via a juxtacrine mechanism of adhesion. The objective of this study was to assess the effect of histamine and LTC4on the leukocyte recruitment in the liver and to study the components and molecular mechanisms involved in this process. We visualized the hepatic microvasculature using intravital microscopy and we determined that LTC4(20 nM) but not histamine (0.1, 0.3, or 1 mM) induced leukocyte recruitment in the liver microcirculation. Histamine could induce leukocyte recruitment but only in the presence of an antihistaminase. The LTC4-induced leukocyte recruitment occurred primarily in sinusoids (not venules) and was not inhibitable by three different anti-P-selectin antibodies (5H1, RMP-1, and RB40). Leukocyte recruitment in P-selectin-deficient mice, intercellular adhesion molecule 1 (ICAM-1)-deficient mice, and mice treated with a PAF antagonist was of the same magnitude as in wild-type animals in response to LTC4. Although PAF alone could induce adhesion in both sinusoids and postsinusoidal venules, this chemotactic agent was not involved in LTC4-induced adhesion in the liver. Finally, an overlapping role for P-selectin and ICAM-1 was ruled out as LTC4induced leukocyte recruitment in P-selectin and ICAM-1 double-deficient mice. These data demonstrate that LTC4does not activate the known early mechanisms of leukocyte recruitment, including P-selectin, PAF, or ICAM-1 in the hepatic microvasculature.
Endogenous interstitial adenosine in isolated myenteric neural networks varies inversely with prevailing P O 2
Authors: Deshpande N. A. , McDonald T. J. , Cook M. A.
Published: December 2017

Isolated myenteric ganglion networks were used in a perifusion protocol to characterize the response of interstitial adenosine levels to changes in prevailing[Formula: see text]. The biological activity of such adenosine was assessed using inhibition of release of substance P (SP) as a functional measure of adenosine activity, and the effect of altered O2 tension on both spontaneous and elevated extracellular K+ concentration-evoked SP release from networks was determined over a range of[Formula: see text] values from hypoxic ([Formula: see text] = 54 mmHg) to hyperoxic ([Formula: see text] = 566 mmHg). Release of SP was found to be sensitive to [Formula: see text], and a linear graded relationship was obtained. Perifusion in the additional presence of the adenosine A1-receptor-selective antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) revealed considerable adenosinergic inhibition with an inverse exponential relationship and hyperoxic threshold [Formula: see text]. Disinhibition of evoked SP release by DPCPX in the absence of TTX was double that observed in its presence, indicating a neural source for some of the adenosine released during hypoxia. A postulated neuroprotective role for adenosine is consistent with the demonstrated relationship between interstitial adenosine and prevailing O2 tension.
Validation of a novel luminal flow velocimeter with video fluoroscopy and manometry in the human esophagus
Authors: Andrews J. M. , Nathan H. , Malbert C. H. , Verhagen M. A. M. T. , Gabb M. , Hebbard G. S. , Kilpatrick D. , MacDonald S. , Rayner C. K. , Doran S. , Omari T. , O’Young E. , Frisby C. , Fraser R. J. , Schoeman M. , Horowitz M. , Dent J.
Published: December 2017

There is currently no ideal method for concurrently assessing intraluminal pressures and flows in humans with high temporal resolution. We have developed and assessed the performance of a novel fiber-optic laser-Doppler velocimeter, mounted in a multichannel manometric assembly. Velocimeter recordings were compared with concurrent fluoroscopy and manometry following 50 barium swallows in healthy subjects. During these swallows, the velocimeter sensor was situated in either the proximal (24 swallows) or the distal (26 swallows) esophagus. It signaled intraluminal flow following 46 of 50 swallows. A greater mean number of deflections were recorded in the distal compared with the proximal esophagus (4.3 vs. 2.4, P = 0.001). The maximal flow velocity recorded did not differ between the proximal and distal esophagus (76.7 vs. 73.8 mm/s). No velocimeter signals commenced after fluoroscopic lumen occlusion. The velocimeter signals were closely temporally related to fluoroscopic barium flow. Upward catheter movement on swallowing sometimes appeared to cause a velocimeter signal. Manometrically “normal” swallows were no different from “abnormal” swallows in the number and velocity of deflections recorded by the velocimeter. This novel instrument measures intraluminal flow velocity and pressures concurrently, thus enabling direct study of pressure-flow relationships. Flow patterns differed between the proximal and distal esophagus.
Experimental colitis increases blood-brain barrier permeability in rabbits
Authors: Hathaway Christopher A. , Appleyard Caroline B. , Percy William H. , Williams John L.
Published: December 2017

Extraintestinal manifestations of inflammatory bowel disease are numerous. This study examined the effects of two models of acute colitis on cerebral blood flow (CBF) and permeability of the blood-brain barrier in rabbits. CBF (measured with radiolabeled microspheres), or the extraction ratio or permeability-surface area (PS) product of the blood-brain barrier to fluorescein and FITC-dextran, was measured 48 h after colitis induction with acetic acid (HAc) or trinitrobenzene sulfonic acid (TNBS). PS product for fluorescein increased ( P < 0.05) in TNBS colitis (1.33 × 10−5 ± 0.52 × 10−5ml/s and 0.48 × 10−5 ± 0.13 × 10−5ml/s (mean ± SE) for treated ( n = 14) and untreated ( n = 10) animals, respectively. PS product for the larger FITC-dextran was not different in TNBS colitis (0.24 × 10−5 ± 0.09 × 10−5ml/s, n = 7) compared with untreated controls (0.19 × 10−5 ± 0.04 × 10−5ml/s, n = 8). PS product for fluorescein increased ( P < 0.01) in HAc colitis compared with vehicle (2.66 × 10−5 ± 1.46 × 10−5ml/s and 0.33 × 10−5 ± 0.05 × 10−5ml/s, respectively; n = 6 in each group). The extraction of fluorescein from the blood to the brain increased by 75% during TNBS colitis when compared with vehicle ( P < 0.05). CBF and cerebrovascular resistance did not change from the untreated control after TNBS colitis. Our data suggest that, irrespective of induction method, acute colitis increases the permeability of the blood-brain barrier to small molecules without changing CBF.
CCK receptor dysfunction in muscle membranes from human gallbladders with cholesterol stones
Authors: Xiao Zuo-Liang , Chen Qian , Amaral Joseph , Biancani Piero , Jensen Robert T. , Behar Jose
Published: December 2017

Human gallbladders with cholesterol stones exhibit impaired muscle contraction induced by agonists that act on transmembrane receptors, increased membrane cholesterol content, and abnormal cholesterol-to-phospholipid ratio compared with those with pigment stones. The present study was designed to investigate the functions of the CCK receptor of gallbladder muscle membranes by radioreceptor assay and cross-linking.125I-labeled CCK-8 binding was time-dependent, competitive, and specific. Scatchard analysis showed that the maximum specific binding (Bmax) was significantly decreased in cholesterol compared with pigment stone gallbladders (0.18 ± 0.07 vs. 0.38 ± 0.05 pmol/mg protein, P < 0.05). In contrast, the affinity for CCK was higher in cholesterol than pigment stone gallbladders (0.18 ± 0.06 vs. 1.2 ± 0.23 nM). Similar results were observed in binding studies with the CCK-A receptor antagonist [3H]L-364,718. Cross-linking and saturation binding studies also showed significantly less CCK binding in gallbladders with cholesterol stones. These abnormalities were reversible after incubation with cholesterol-free liposomes. The Bmaxincreased ( P < 0.01) and the dissociation constant decreased ( P < 0.001) after incubation with cholesterol-free liposomes. In conclusion, human gallbladders with cholesterol stones have impaired CCK receptor binding compared with those with pigment stones. These changes are reversed by removal of the excess membrane cholesterol. These receptor alterations may contribute to the defective contractility of the gallbladder muscle in patients with cholesterol stones.
Visual parameters define the phase and the load of contractions in isolated guinea pig ileum
Authors: Schulze-Delrieu Konrad
Published: December 2017

How the movements of the intestinal walls relate to luminal pressures and outflow remains incompletely understood. We triggered the peristaltic reflex in the isolated ileum of the guinea pig and quantified wall movements through computerized measurements of diameter changes. Contractions developed as indentations close to the upstream end of the loop. The indentations deepened and expanded in length. The downstream shoulder of contractions started and stopped to propagate before the upstream shoulder. Shoulders differed in their length and gradient over most of the duration of the contraction, and this gives the contraction an axial asymmetry. Over the course of individual contractions, the length of the indented segment correlated well with the luminal pressure. Contractions in response to large volumes generated long indented segments and high luminal pressures. The onset and the end of pressure waves and of outflow did not necessarily coincide with the onset and end of visual parameters of contractions. These findings indicate that objective visual parameters might be useful to describe and to classify contractions.
Modeling intermittent digesta flow to calculate glucose uptake capacity of the bovine small intestine
Authors: Cant John P. , Luimes Paul H. , Wright Tom C. , McBride Brian W.
Published: December 2017

To test the hypothesis that the uptake capacity of the bovine small intestine for glucose is upregulated to match or slightly exceed glucose delivery, glucose was continuously infused into the proximal duodenum of four cannulated holstein heifers. Every 3 days, infusion rates were increased by an average of 34 mmol/h. A model of glucose disappearance from multiple boluses of intestinal digesta was used to estimate the transporter maximum velocity and functional maximum uptake capacity for the entire small intestine from average ileal glucose flows during the third day of each period. Because of its intermittency, digesta flow remained independent of simulated transit time. For each unit increase in glucose infusion rate, uptake capacity increased by only 0.55 units. Excess capacity for glucose uptake was approximately twofold in forage-fed cattle and declined to below delivery at infusions of >208 mmol/h added glucose, approximately three times the normal load. Calculations for cattle, sheep, and rats indicate that the glucose transport capacity of the small intestine is typically underutilized because of a fraction of time that transporters are not in contact with digesta.
MRP3, a new ATP-binding cassette protein localized to the canalicular domain of the hepatocyte
Authors: Ortiz Daniel F. , Li Shaohua , Iyer Ramachandran , Zhang Xingming , Novikoff Phyllis , Arias Irwin M.
Published: December 2017

Bile secretion in liver is driven in large part by ATP-binding cassette (ABC)-type proteins that reside in the canalicular membrane and effect ATP-dependent transport of bile acids, phospholipids, and non-bile acid organic anions. Canalicular ABC-type proteins can be classified into two subfamilies based on membrane topology and sequence identity: MDR1, MDR3, and SPGP resemble the multidrug resistance (MDR) P-glycoprotein, whereas MRP2 is similar in structure and sequence to the multidrug resistance protein MRP1 and transports similar substrates. We now report the isolation of the rMRP3 gene from rat liver, which codes for a protein 1522 amino acids in length that exhibits extensive sequence similarity with MRP1 and MRP2. Northern blot analyses indicate that rMRP3 is expressed in lung and intestine of Sprague-Dawley rats as well as in liver of Eisai hyperbilirubinemic rats and TR−mutant rats, which are deficient in MRP2 expression. rMRP3 expression is also transiently induced in liver shortly after birth and during obstructive cholestasis. Antibodies raised against MRP3 recognize a polypeptide of 190–200 kDa, which is reduced in size to 155–165 kDa after treatment with endoglycosidases. Immunoblot analysis and immunoconfocal microscopy indicate that rMRP3 is present in the canalicular membrane, suggesting that it may play a role in bile formation.
Differential changes in ACh-, motilin-, substance P-, and K+-induced contractility in rabbit colitis
Authors: Depoortere Inge , van Assche Gert , Thijs Theo , Geboes Karel , Peeters Theo L.
Published: December 2017

To test the hypothesis that the changes in intestinal contractility, which accompany inflammation of the gut, are agonist specific, we compared the response of inflamed strips to substance P (SP), motilin, ACh, and K+ as a function of time. In parallel experiments, changes in the general mechanical properties (passive tension, optimal stretch) of the colitic tissue were evaluated. Colitis was induced by trinitrobenzenesulfonic acid, and rabbits were killed after 1, 2, 3, 5, or 8 days. Passive tension was increased starting from day 2 until day 8, and maximal active tension ( T max) was generated at less stretch from day 5. A 50% decrease in T max was observed for ACh and K+ between days 2 and 3 and for motilin and SP between days 3 and 5. For all compounds, T max returned to normal after 8 days. The pEC50value (negative logarithm of the concentration that induces 50% of the maximal contractile activity) for ACh was increased from day 3 until day 8 and for SP at day 3, whereas for motilin it was decreased at day 1. The changes in passive tension and optimal stretch indicate generalized structural alterations of smooth muscle tissue. However, the different time profiles of the changes in active tension and contractile potency for different contractile agents suggest that inflammation specifically affects receptor-mediated mechanisms.
Lymphatic absorption of structured triglycerides vs. physical mix in a rat model of fat malabsorption
Authors: Tso Patrick , Lee Theresa , Demichele Stephen J.
Published: December 2017

Comparison was made between the intestinal absorption and lymphatic transport of a randomly interesterified fish oil and medium-chain triglyceride (MCT) structured triglycerides (STG) vs. the physical mix in rat small intestine following ischemia and reperfusion (I/R) injury. Under halothane anesthesia, the superior mesenteric artery (SMA) was occluded for 20 min and then reperfused in I/R rats. The SMA was isolated but not occluded in control rats. In both treatment groups, the mesenteric lymph duct was cannulated and a gastric tube was inserted. Each treatment group received 1 ml of the fish oil-MCT STG or physical mix (7 rats/group) through the gastric tube followed by an infusion of PBS at 3 ml/h for 8 h. Lymph was collected hourly for 8 h. Lymph triglyceride, cholesterol, and decanoic and eicosapentaenoic acids increased rapidly and maintained a significantly higher output ( P < 0.01) with STG compared with physical mix in control rats over 8 h. After I/R, lymphatic triglyceride output decreased 50% compared with control. Gastric infusion of STG significantly improved lipid transport by having a twofold higher triglyceride, cholesterol, and decanoic and eicosapentaenoic acids output to lymph compared with its physical mix ( P < 0.01). We conclude that STG is absorbed into lymph significantly better than physical mix by both the normal intestine and the intestine injured by I/R.
Corticosteroid receptors and 11β-hydroxysteroid dehydrogenase isoforms in rat intestinal epithelia
Authors: Sheppard Karen E. , Li Kevin X. Z. , Autelitano Dominic J.
Published: December 2017

To evaluate the potential roles that both receptors and enzymes play in corticosteroid regulation of intestinal function, we have determined glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and 11β-hydroxysteroid dehydrogenase (11β-HSD) expression in intestinal epithelial cells. GR and MR mRNA and receptor binding were ubiquitously expressed in epithelial cells, with receptor levels higher in ileum and colon than jejunum and duodenum. RNase protection analysis showed that 11β-HSD1 was not expressed in intestinal epithelial cells, and enzyme activity studies detected no 11-reductase activity. 11β-HSD2 mRNA and protein were demonstrated in ileal and colonic epithelia; both MR and GR binding increased when enzyme activity was inhibited with carbenoxolone. Duodenal and jejunal epithelial cells showed very little 11β-HSD2 mRNA and undetectable 11β-HSD2 protein; despite minor (<7%) dehydrogenase activity in these cells, enzyme activity did not alter binding of corticosterone to either MR or GR. These findings demonstrate the ubiquitous but differential expression of MR and GR in intestinal epithelia and that 11β-HSD2 modulates corticosteroid binding to both MR and GR in ileum and proximal and distal colon but not in duodenum or jejunum.
Na transport in sheep rumen is modulated by voltage-dependent cation conductance in apical membrane
Authors: Lang Ingo , Martens Holger
Published: December 2017

The effects of clamping the transepithelial potential difference (PDt; mucosa reference) have been studied in sheep rumen epithelium. Pieces of ruminal epithelium were examined in Ussing chambers, in a part of the experiments combined with conventional intracellular recordings. After equilibration, the tissue conductance ( G t) was 2.50 ± 0.09 mS/cm2, the potential difference of the apical membrane (PDa) was −47 ± 2 mV, and the fractional resistance of the apical membrane (f R a) was 68 ± 2% under short-circuit conditions. Hyperpolarization of the tissue (bloodside positive) depolarized PDa, decreased f R a, and increased G tsignificantly. Clamping PDt at negative values caused converse effects on PDa and f R a. All changes were completely reversible. The determination of individual conductances revealed that the conductance of the apical membrane increased almost linearly with depolarization of PDa. The PD-dependent changes were significantly reduced by total replacement of Na. These observations support the assumption of a PD-dependent conductance in the apical membrane that permits enhanced apical uptake of Na even at depolarized PDa. This mechanism appears to be important for the regulation of osmotic pressure in forestomach fluid.
Gastrointestinal motor and myoelectric correlates of motion sickness
Authors: Lang Ivan M. , Sarna S. K. , Shaker R.
Published: December 2017

The objectives of this study were to characterize the digestive tract motor and myoelectric responses associated with motion sickness. Twenty-two cats (1.5–3.0 kg) were chronically implanted with force transducers and electrodes on the stomach and small intestine. Motion sickness was activated by vertical oscillation (VO) at ±0.5 g and identified as salivation, licking, or vomiting. Vomiting was initiated chemically by UK-14304 (2.5–15 μg/kg iv) or CuSO4(10–50 mg ig). We found that VO caused vomiting (45% of trials), a decrease in gastrointestinal (GI) motility (69% of trials), salivation or licking (59% of trials), bradygastria (39% of trials), retrograde giant contraction (RGC, 43% of trials), giant migrating contraction (GMC, 5% of trials), and defecation (18% of trials). The decrease in GI motility occurred with (62% of trials) or without (69% of trials) vomiting. Motion sickness was accompanied by bradygastria (52% of trials) and decreased GI motility (70% of trials). Similar events occurred after CuSO4and UK-14304, but the incidences of responses after CuSO4were less frequent, except for vomiting, RGC, and GMC. UK-14304 never caused GMCs or defecation. The magnitude and velocity of the RGC were the same during all emetic stimuli, and RGCs never occurred without subsequent vomiting. Supradiaphragmatic vagotomy ( n = 1) or atropine ( n = 2, 10 or 50 μg/kg iv) blocked the RGC, but not vomiting, due to VO. We concluded that 1) oculovestibular stimulation causes digestive tract responses similar to other types of emetic stimuli, 2) decreased GI motility and bradygastria may be physiological correlates of the motion sickness, and 3) motion sickness may not be dependent on any specific GI motor or myoelectric response.
Differential protective effects of Bcl-xLand Bcl-2 on apoptotic liver injury in transgenic mice
Authors: de la Coste Alix , Fabre Monique , McDonell Nathalie , Porteu Arlette , Gilgenkrantz Helène , Perret Christine , Kahn Axel , Mignon Alexandre
Published: December 2017

Fas ligand (CD95L) and tumor necrosis factor-α (TNF-α) are pivotal inducers of hepatocyte apoptosis. Uncontrolled activation of these two systems is involved in several forms of liver injury. Although the broad antiapoptotic action of Bcl-2 and Bcl-xLhas been clearly established in various apoptotic pathways, their ability to inhibit the Fas/CD95- and TNF-α-mediated apoptotic signal has remained controversial. We have demonstrated that the expression of BCL-2 in hepatocytes protects them against Fas-induced fulminant hepatitis in transgenic mice. The present study shows that transgenic mice overexpressing[Formula: see text]in hepatocytes are also protected from Fas-induced apoptosis in a dose-dependent manner. Bcl-xLand Bcl-2 were protective without any change in the level of endogenous[Formula: see text]or Bax and inhibited hepatic caspase-3-like activity. In vivo injection of TNF-α caused massive apoptosis and death only when transcription was inhibited. Under these conditions,[Formula: see text]mice were partially protected from liver injury and death but PK-BCL-2 mice were not. A similar differential protective effect of Bcl-xLand Bcl-2 transgenes was observed when Fas/CD95 was activated and transcription blocked. These results suggest that apoptosis triggered by activation of both Fas/CD95 and TNF-α receptors is to some extent counteracted by the transcription-dependent protective effects, which are essential for the antiapoptotic activity of Bcl-2 but not of Bcl-xL. Therefore, Bcl-xLand Bcl-2 appear to have different antiapoptotic effects in the liver whose characterization could facilitate their use to prevent the uncontrolled apoptosis of hepatocytes.
Cholesterol inhibits spontaneous action potentials and calcium currents in guinea pig gallbladder smooth muscle
Authors: Jennings Lee J. , Xu Qi-Wei , Firth Tracy A. , Nelson Mark T. , Mawe Gary M.
Published: December 2017

Elevated cholesterol decreases agonist-induced contractility and enhances stone formation in the gallbladder. The current study was conducted to determine if and how the electrical properties and ionic conductances of gallbladder smooth muscle are altered by elevated cholesterol. Cholesterol was delivered as a complex with cyclodextrin, and effects were evaluated with intracellular recordings from intact gallbladder and whole cell patch-clamp recordings from isolated cells. Cholesterol significantly attenuated the spontaneous action potentials of intact tissue. Furthermore, calcium-dependent action potentials and calcium currents were reduced in the intact tissue and in isolated cells, respectively. However, neither membrane potential hyperpolarizations induced by the ATP-sensitive potassium channel opener, pinacidil, nor voltage-activated outward potassium currents were affected by cholesterol. Hyperpolarizations elicited by calcitonin gene-related peptide were reduced by cholesterol enrichment, indicating potential changes in receptor ligand binding and/or second messenger interactions. These data indicate that excess cholesterol can contribute to gallbladder stasis by affecting calcium channel activity, whereas potassium channels remained unaffected. In addition, cholesterol enrichment may also modulate receptor ligand behavior and/or second messenger interactions.
Substance P may attenuate gastric hyperemia by a mast cell-dependent mechanism in the damaged gastric mucosa
Authors: Rydning Astrid , Lyng Oddveig , Aase Steinar , Grønbech Jon Erik
Published: December 2017

Calcitonin gene-related peptide (CGRP) released from sensory neurons, which are closely apposed to mast cells and blood vessels, mediates gastric hyperemia in response to acid challenge of the damaged mucosa. Substance P (SP) is coreleased with CGRP from sensory neurons, but the role of this peptide in gastric blood flow regulation is largely unknown. Chambered rat stomachs were exposed to 1.5 M NaCl and acidic saline after treatment with SP, aprotinin (serine protease inhibitor), and the mast cell stabilizers ketotifen and sodium cromoglycate (SCG). Gastric hyperemia (measured with a laser Doppler flow velocimeter) after hypertonic injury and acid challenge was nearly abolished by SP. Aprotinin infused together with SP and pretreatment with ketotifen and SCG before SP restored the gastric hyperemia. Ketotifen and SCG inhibited mast cell degranulation in SP-treated rats. Preservation of gastric hyperemia was correlated with improved mucosal repair. These data suggest that impaired hyperemia by SP during acid challenge of the gastric mucosa may be mediated by a mast cell-dependent mechanism involving the release of proteases from mast cells.
Expression and modulation of p42/p44 MAPKs and cell cycle regulatory proteins in rat pancreas regeneration
Authors: Morisset Jean , Aliaga JoséCristobal , Calvo Ezéquiel L. , Bourassa Judith , Rivard Nathalie
Published: December 2017

Pancreatic growth occurs after CCK, CCK-induced pancreatitis, and pancreatectomy; the mechanisms involved remain unknown. This study evaluates mitogen-activated protein kinase (MAPK) activation and expression of cell cycle regulatory proteins after pancreatectomy to understand the cellular and molecular mechanisms involved in pancreas regeneration. Rats were killed 1–12 days after pancreatectomy, and p42/p44 MAPK activation, expression of the cyclins D and E, cyclin-dependent kinase (Cdk)-2 activity, retinoblastoma protein (pRb) hyperphosphorylation, and expression of the cyclin kinase inhibitors p15, p21, and p27 were examined. Pancreatic remnants exhibited sustained p42/p44 MAPK activation within 8 h. Cyclins D1 and E showed maximal expression after 2 and 6 days, coinciding with maximal hyperphosphorylation of pRb and Cdk2 activity. The expression of p15 vanished after 12 h, p27 disappeared gradually, and p21 increased early. The p27 complexed with Cdk2 dissociated after 2 days, whereas p21 associated in a reverse fashion. In conclusion, sustained activation of p42/p44 MAPKs and Cdk2 along with overexpression of cyclins D1 and E and reduction of p15 and p27 cyclin inhibitors occurred early after pancreatectomy and are active factors involved in signaling that leads to pancreas regeneration.
Mg2+transport in sheep rumen epithelium: evidence for an electrodiffusive uptake mechanism
Authors: Schweigel Monika , Lang Ingo , Martens Holger
Published: December 2017

The potential difference (PD)-dependent component of transcellular Mg2+uptake in sheep rumen epithelium was studied. Unidirectional28Mg2+fluxes were measured at various transepithelial PD values, and the unidirectional mucosal-to-serosal28Mg2+flux ([Formula: see text]) was correlated with the PD across the apical membrane (PDa) determined by mucosal impalement with microelectrodes. PDawas found to be −54 ± 5 mV, and [Formula: see text] was 65.9 ± 13.8 nmol ⋅ cm−2⋅ h−1under short-circuit conditions. Hyperpolarization of the ruminal epithelium (blood-side positive) depolarized PDaand, most noticeably, decreased [Formula: see text]. Further experiments were performed with cultured ruminal epithelial cells (REC). With the aid of the fluorescence probe mag-fura 2, we measured the intracellular free Mg2+concentration ([Mg2+]i) of isolated REC under basal conditions at various extracellular Mg2+concentrations ([Mg2+]e) and after alterations of the transmembrane voltage. Basal [Mg2+]iwas 0.54 ± 0.08 mM. REC suspended in media with [Mg2+]ebetween 0.5 and 7.5 mM showed an increase in [Mg2+]ithat was dependent on [Mg2+]eand that exhibited a saturable component (Michaelis-Menten constant = 1.2 mM; maximum [Mg2+]i= 1.26 mM). Membrane depolarization with high extracellular K+(40, 80, or 140 mM K+) and the K+channel blocker quinidine (50 and 100 μM ) resulted in a decrease in [Mg2+]i. On the other hand, hyperpolarization created by K+diffusion (intracellular K+concentration > extracellular K+concentration) in the presence of valinomycin induced a 15% increase in [Mg2+]i. None of the manipulations had any effect on intracellular Ca2+concentration and intracellular pH. The results support the assumption that the membrane potential acts as a principal driving force for Mg2+entry in REC and suggest that the pathway for this electrodiffusive Mg2+uptake across the luminal membrane is a channel or a carrier.
VI. Liver repopulation systems and study of pathophysiological mechanisms in animals
Authors: Gupta Sanjeev , Rogler Charles E.
Published: December 2017

The ability to localize transplanted hepatocytes in the liver offers exciting new opportunities. Transplanted hepatocytes enter liver plates, form hybrid plasma membrane structures with adjacent hepatocytes, express liver genes correctly, and survive indefinitely. The transplanted cell mass is regulated, such that cell proliferation is limited in the normal adult liver, whereas the liver is repopulated extensively when proliferation rates in transplanted and host hepatocytes become dissociated or host hepatocytes are ablated selectively. Transplanted hepatocytes are susceptible to hepatitis viruses. These aspects of transplanted hepatocyte biology indicate that liver repopulation systems can help address questions concerning pathophysiological mechanisms.
Capsaicin sensitivity and voltage-gated sodium currents in colon sensory neurons from rat dorsal root ganglia
Authors: Su Xin , Wachtel Ruth E. , Gebhart G. F.
Published: December 2017

DiI-labeled colon sensory neurons were acutely dissociated from S1 rat dorsal root ganglia (DRG) and studied using perforated whole cell patch-clamp techniques. Forty-six percent (54/116) of labeled sensory neurons responded to capsaicin (10−8– 10−5M) with an increase in inward current, which was a nonspecific cation conductance. Responses to capsaicin applied by puffer ejection were dependent on dose, with a half-maximal response at 4.9 × 10−7M; bath application was characterized by marked desensitization. Voltage-gated Na+currents in 23 of 30 DRG cells exhibited both TTX-sensitive and TTX-resistant components. In these cells, capsaicin induced an inward current in 11 of 17 cells tested. Of the cells containing only a TTX-sensitive component, none of six cells tested was sensitive to capsaicin. In all cells that responded to capsaicin with an increase in inward current, capsaicin abolished voltage-gated Na+currents ( n = 21). Capsazepine (10−6M) significantly attenuated both the increase in inward current and the reduction in Na+currents. Na+currents were not significantly altered by adenosine, bradykinin, histamine, PGE2, or serotonin at 10−6M and 10−5M. These findings may have important implications for understanding both the irritant and analgesic properties of capsaicin.
Cloning, expression, and vesicular localization of zinc transporter Dri 27/ZnT4 in intestinal tissue and cells
Authors: Murgia Chiara , Vespignani Isabella , Cerase Joanna , Nobili Fabio , Perozzi Giuditta
Published: December 2017

We have identified the Dri 27 cDNA on the basis of its upregulated expression during rat intestinal development. It encodes a hydrophobic protein of 430 amino acids that shares significant homology with members of the mammalian zinc transporter family ZnT. The murine homologue of Dri 27 (named ZnT4) was recently associated with the mouse mutation “lethal milk.” The primary sequence of Dri 27/ZnT4 displays features characteristic of polytopic membrane proteins. In this paper, we show that Dri 27/ZnT4 is localized in the membrane of intracellular vesicles, the majority of which concentrate in the basal cytoplasmic region of polarized enterocytes. A Dri 27/ZnT4 myc-tagged construct, transiently transfected in intestinal Caco-2 cells, partially colocalizes with the transferrin receptor and with the β-subunits of the clathrin adaptor complexes AP-1 and AP-2 in a subpopulation of endosomal vesicles. By subcloning distinct portions of the protein in frame with glutathione- S-transferase, we also provide experimental evidence of their function as zinc-binding and protein-protein-interaction domains.
Bacterial colonization and healing of gastric ulcers: the effects of epidermal growth factor
Authors: Elliott Susan N. , Wallace J. L. , McKnight W. , Gall D. G. , Hardin J. A. , Olson M. , Buret A.
Published: December 2017

.—Experimental gastric ulcers are rapidly colonized by various bacteria, resulting in significantly impaired healing. Epidermal growth factor (EGF) is capable of preventing bacterial colonization of the healthy intestinal mucosa. In this study, we examined the possibility that EGF accelerates gastric ulcer healing by reducing bacterial colonization of the ulcer. Gastric ulcers were induced by serosal application of acetic acid. The effect of daily administration of EGF on ulcer healing and bacterial colonization was assessed and compared with the effect of daily treatment with broad-spectrum antibiotics. EGF administration reduced colonization levels and accelerated ulcer healing as effectively as the antibiotic treatment. EGF was without effect on acid secretion or neutrophil infiltration into the ulcer. Bacterial growth was not inhibited in the presence of EGF in vitro. These results demonstrate that EGF reduces bacterial colonization during an established infection of a compromised mucosal surface. This effect may contribute to the ability of EGF to accelerate gastric ulcer healing. This effect is acid independent and not due to an anti-inflammatory effect or to direct bactericidal actions.
Heme oxygenase-2 distribution in anorectum: colocalization with neuronal nitric oxide synthase
Authors: Battish Raman , Cao Gao-Yuan , Lynn Richard B. , Chakder Sushanta , Rattan Satish
Published: December 2017

Recent investigations have suggested carbon monoxide (CO) as a putative messenger molecule. Although several studies have implicated the heme oxygenase (HO) pathway, responsible for the endogenous production of CO, in the neuromodulatory control of the internal anal sphincter (IAS), its exact role is not known. Nitric oxide, produced by neuronal nitric oxide synthase (nNOS) of myenteric neurons, is an important inhibitory neural messenger molecule mediating nonadrenergic noncholinergic (NANC) relaxation of the IAS. The present studies were undertaken to investigate in detail the presence and coexistence of heme oxygenase-2 (HO-2) with nNOS in the opossum anorectum. In perfusion-fixed, frozen-sectioned tissue, HO-2 immunoreactive (IR) and nNOS IR nerves were identified using immunocytochemistry. Ganglia containing HO-2 IR neuronal cell bodies were present in the myenteric and submucosal plexuses throughout the entire anorectum. Colocalization of HO-2 IR and nNOS IR was nearly 100% in the IAS and decreased proximally from the anal verge. In the rectum, colocalization of HO-2 IR and nNOS IR was ∼70%. Additional confocal microscopy studies using c-Kit staining demonstrated the localization of HO-2 IR and nNOS IR in interstitial cells of Cajal (ICC) of the anorectum. From the high rate of colocalization of HO-2 IR and nNOS IR in the IAS as well as the localization of HO-2 IR and nNOS IR in ICC in conjunction with earlier studies of the HO pathway, we speculate an interaction between HO and NOS pathways in the NANC inhibitory neurotransmission of the IAS and rectum.
Rat and guinea pig pancreatic acini possess both VIP1and VIP2receptors, which mediate enzyme secretion
Authors: Ito T. , Hou W. , Katsuno T. , Igarashi H. , Pradhan T. K. , Mantey S. A. , Coy D. H. , Jensen R. T.
Published: December 2017

Pancreatic acini from most species possess vasoactive intestinal peptide (VIP) receptors. Recently, two subtypes of VIP receptors, VIP1-R and VIP2-R, were cloned. Which subtype exists on pancreatic acini or mediates secretion is unclear. To address this, we examined pancreatic acini from both rat and guinea pig. VIP1-R and VIP2-R mRNA were identified in dispersed acini from both species by Northern blot analysis and in rat by Southern blot analysis. With the use of the VIP2-R-selective ligand Ro-25-1553 in both species, inhibition of binding of125I-labeled VIP to acini showed a biphasic pattern with a high-affinity component (10%) and a second representing 90%. The VIP1-R-selective ligand, [Lys15,Arg16,Leu27]VIP-(1—7)-GRF-(8—27), gave a monophasic pattern. Binding of Ro-25-1553 was better fit by a two-site model. In both rat and guinea pig acini, the dose-response curve of Ro-25-1553 for stimulation of enzyme secretion was biphasic, with a high-affinity component of 10–15% of the maximal secretion and a low-affinity component accounting for 85–90%. At low concentrations (10 nM) of Ro-25-1553 and [Lys15,Arg16,Leu27]VIP-(1—7)-GRF(8—27), which only occupy VIP receptors, a 4-fold and a 56-fold increase in cAMP occurred, respectively. These results show that both VIP1-R and VIP2-R subtypes exist on pancreatic acini of rat and guinea pig, their activation stimulates enzyme secretion by a cAMP-mediated mechanism, and the effects of VIP are mediated 90% by activation of VIP1-R and 10% by VIP2-R. Because VIP has a high affinity for both VIP-R subtypes, its effect on pancreatic acini is mediated by two receptor subtypes, which will need to be considered in future studies of the action of VIP in the pancreas.
NHE1, NHE2, and NHE3 contribute to regulation of intracellular pH in murine duodenal epithelial cells
Authors: Praetorius J. , Andreasen D. , Jensen B. L. , Ainsworth M. A. , Friis U. G. , Johansen T.
Published: December 2017

Na+/H+-exchangers (NHE) mediate acid extrusion from duodenal epithelial cells, but the isoforms involved have not previously been determined. Thus we investigated 1) the contribution of Na+-dependent processes to acid extrusion, 2) sensitivity to Na+/H+exchange inhibitors, and 3) molecular expression of NHE isoforms. By fluorescence spectroscopy the recovery of intracellular pH (pHi) was measured on suspensions of isolated acidified murine duodenal epithelial cells loaded with 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Expression of NHE isoforms was studied by RT-PCR and Western blot analysis. Reduction of extracellular Na+concentration ([Na+]o) during pHirecovery decreased H+efflux to minimally 12.5% of control with a relatively high apparent Michaelis constant for extracellular Na+. The Na+/H+exchange inhibitors ethylisopropylamiloride and amiloride inhibited H+efflux maximally by 57 and 80%, respectively. NHE1, NHE2, and NHE3 were expressed at the mRNA level (RT-PCR) as well as at the protein level (Western blot analysis). On the basis of the effects of low [Na+]oand inhibitors we propose that acid extrusion in duodenal epithelial cells involves Na+/H+exchange by isoforms NHE1, NHE2, and NHE3.
Release of osmolytes induced by phagocytosis and hormones in rat liver
Authors: Wettstein Matthias , Peters-Regehr Thorsten , Kubitz Ralf , Fischer Richard , Holneicher Claudia , Mönnighoff Irmhild , Häussinger Dieter
Published: December 2017

Betaine, taurine, and inositol participate as osmolytes in liver cell volume homeostasis and interfere with cell function. In this study we investigated whether osmolytes are also released from the intact liver independent of osmolarity changes. In the perfused rat liver, phagocytosis of carbon particles led to a four- to fivefold stimulation of taurine efflux into the effluent perfusate above basal release rates. This taurine release was inhibited by 70–80% by the anion exchange inhibitor DIDS or by pretreatment of the rats with gadolinium chloride. Administration of vasopressin, cAMP, extracellular ATP, and glucagon also increased release of betaine and/or taurine, whereas insulin, extracellular UTP, and adenosine were without effect. In isolated liver cells, it was shown that parenchymal cells and sinusoidal endothelial cells, but not Kupffer cells and hepatic stellate cells, release osmolytes upon hormone stimulation. This may be caused by a lack of hormone receptor expression in these cells, because single-cell fluorescence measurements revealed an increase of intracellular calcium concentration in response to vasopressin and glucagon in parenchymal cells and sinusoidal endothelial cells but not in Kupffer cells and hepatic stellate cells. The data show that Kupffer cells release osmolytes during phagocytosis via DIDS-sensitive anion channels. This mechanism may be used to compensate for the increase in cell volume induced by the ingestion of phagocytosable material. The physiological significance of hormone-induced osmolyte release remains to be evaluated.