bluuebunny/crossref_metadata_2025 huggingface dataset:
hCG: its pancreatic and duodenal receptors and in vivo electrolyte secretion in female rats
Authors: Panesar N. S. , Poon C. W.
Published: December 2017

A state of fluid flux probably resulting from ion movement across the plasma membrane occurs during early pregnancy or trophoblastic disease, manifesting as emesis or hyperemesis gravidarum or hydatidiform moles. In emesis or hyperemesis gravidarum, excessive secretion induced by a humoral agent may trigger vomiting by distending and activating the gastrointestinal (GI) tract mechanoreceptors. This agent may be human chorionic gonadotropin (hCG). High-affinity hCG binding sites similar to those in the ovary were found in the duodenum and pancreas of female rats, with dissociation constant values of 0.11 ± 0.02, 1.9 ± 0.6, and 4.7 ± 3.5 nM, respectively. The isoelectric point for duodenal and ovarian proteins was 5.5. With the use of two antisera directed against amino acid residues 24–33 and 239–249 of the lutropin receptor, positive immunohistochemical staining was seen in smooth muscle, Brunner’s glands, parasympathetic ganglia, crypt cells, and blood vessels of the duodenum, in zymogen granules of acini, and in intralobular ducts and blood vessels of the pancreas. Under nonreducing conditions, 150- and 170-kDa proteins were seen, through Western blot analysis, in the pancreas, duodenum, and ovary. Administration of hCG to female rats in vivo caused a significant increase in[Formula: see text] and K+ secretion from the duodenum and pancreas. We hypothesize that during pregnancy hCG stimulates excessive secretion of electrolytes (and fluid) into the upper GI tract, which culminates in the vomiting during pregnancy.
Cellular distribution of secretin receptor expression in rat pancreas
Authors: Ulrich Charles D. , Wood Paul , Hadac Elizabeth M. , Kopras Elizabeth , Whitcomb David C. , Miller Laurence J.
Published: December 2017

Secretin is an important regulator of pancreatic function, but the molecular basis of its actions is not well understood. We have, therefore, used in situ autoradiography, photoaffinity labeling, and RNase protection assays with healthy rat pancreas, dispersed acinar cells, and pancreas depleted of acinar cells to explore the cellular distribution and molecular identity of high-affinity secretin receptors in this complex organ. The autoradiographic examination of125I-labeled [Tyr10]rat secretin-27 binding to normal pancreas demonstrated saturable and specific high-affinity binding sites on both acinar and duct cells, with a uniform lobular distribution, but with no binding above background over islets or vascular structures. Photoaffinity labeling demonstrated that the ductular binding site in acinar cell-depleted copper-deficient rat pancreas represented the same glycoprotein with a molecular weight of 50,000–62,000 that was present on acinar cells. RNase protection assays confirmed the molecular identity of the secretin receptors expressed on these distinct cells. The apparent absence or extreme low density of similar secretin receptors on islets and pancreatic vascular structures suggests that the pharmacological effects of secretin on those cells may either be indirect or mediated by another secretin family receptor that recognizes this hormone with lower affinity.
Fibroblasts stimulate acinar cell proliferation through IGF-I during regeneration from acute pancreatitis
Authors: Ludwig C. U. , Menke A. , Adler G. , Lutz M. P.
Published: December 2017

Pancreatic regeneration after caerulein-induced pancreatitis is characterized by transient fibroblast proliferation followed by replication of acinar cells. The mechanisms that coordinate regeneration are incompletely understood. In this study, we examine the role of insulin-like growth factor I (IGF-I). Acute edematous pancreatitis was induced in rats by 12 h caerulein infusion. Pancreatic IGF-I mRNA levels increased over 50-fold during regeneration, reaching a maximum at day 2. Immunohistochemically, IGF-I was localized to fibroblasts within the areas of interstitial tissue. IGF-I mRNA was demonstrated in primary cultures of pancreatic fibroblasts but not in cultured pancreatic acinar cells. However, with the use of Western blotting acinar cells did express IGF-I receptors. IGF-I stimulated 5-bromo-2′-deoxyuridine uptake and increased numbers of acinar cells in a dose-dependent manner. Stimulation was half maximal at 1.1 nM and completely inhibited by an IGF-I antagonist and by IGF binding protein-3 (IGFBP-3). Possible paracrine regulation was confirmed by stimulation of acinar cell proliferation with fibroblast-conditioned medium, which was partially inhibited by IGF-I antagonist or by IGFBP-3. We conclude that acinar cell proliferation during late regeneration from pancreatitis is mediated at least in part by paracrine release of IGF-I from fibroblasts.
FGF-2 enhances intestinal stem cell survival and its expression is induced after radiation injury
Authors: Houchen Courtney W. , George Robert J. , Sturmoski Mark A. , Cohn Steven M.
Published: December 2017

Fibroblast growth factors (FGFs) have mitogenic activity toward a wide variety of cells of mesenchymal, neuronal, and epithelial origin and regulate events in normal embryonic development, angiogenesis, wound repair, and neoplasia. FGF-2 is expressed in many normal adult tissues and can regulate migration and replication of intestinal epithelial cells in culture. However, little is known about the effects of FGF-2 on intestinal epithelial stem cells during either normal epithelial renewal or regeneration of a functional epithelium after injury. In this study, we investigated the expression of FGF-2 in the mouse small intestine after irradiation and determined the effect of exogenous FGF-2 on crypt stem cell survival after radiation injury. Expression of FGF-2 mRNA and protein began to increase at 12 h after γ-irradiation, and peak levels were observed from 48 to 120 h after irradiation. At all times after irradiation, the higher molecular mass isoform (∼24 kDa) of FGF-2 was the predominant form expressed in the small intestine. Immunohistochemical analysis of FGF-2 expression after radiation injury demonstrated that FGF-2 was predominantly found in the mesenchyme surrounding regenerating crypts. Exogenous recombinant human FGF-2 (rhFGF-2) markedly enhanced crypt stem cell survival when given before irradiation. We conclude that expression of FGF-2 is induced by radiation injury and that rhFGF-2 can enhance crypt stem cell survival after subsequent injury.
Atropine-resistant secretion of a putative luminal CCK-releasing peptide in conscious rats
Authors: Miyasaka Kyoko , Tateishi Kayoko , Masuda Masao , Jimi Atsuo , Funakoshi Akihiro
Published: December 2017

The changes in levels of the newly discovered luminal CCK-releasing factor (LCRF) in the small intestinal lumen before and after bile-pancreatic juice diversion in conscious rats were examined by a specific RIA. Moreover, we also examined whether LCRF secretion was under cholinergic control. Anti-LCRF antiserum was raised in rabbits, and a sensitive RIA was established. The localization of LCRF was examined by immunohistochemistry. The luminal content of LCRF was significantly increased by bile-pancreatic juice diversion, during which luminal trypsin activity was eliminated. The increase in luminal LCRF content was not inhibited by intravenous infusion of atropine. The changes in plasma levels of CCK and pancreatic secretion were similar to those in luminal LCRF contents. LCRF immunostaining was observed in villus tip enterocytes of the small intestine and was most prominent in the duodenal portion. These results support our original hypothesis that LCRF may be released spontaneously into the small intestinal lumen from the villus tip enterocytes and its intraluminal degradation by proteases regulates CCK release. Furthermore, LCRF release was not subject to cholinergic regulation.
Human colonic epithelial cells express galanin-1 receptors, which when activated cause Cl−secretion
Authors: Benya Richard V. , Marrero Jorge A. , Ostrovskiy Denis A. , Koutsouris Athanasia , Hecht Gail
Published: December 2017

Galanin is a peptide hormone widely expressed in the central nervous system and gastrointestinal (GI) tract. Within the GI tract galanin is present in enteric nerve terminals where it is known to modulate intestinal motility by altering smooth muscle contraction. Recent studies also show that galanin can alter intestinal short-circuit current ( Isc) but with differing results observed in rats, rabbits, guinea pigs, and pigs. In contrast, nothing is known about the ability of galanin to alter ion transport in human intestinal epithelial tissues. By RT-PCR, we determined that these tissues express only the galanin-1 receptor (Gal1-R) subtype. To evaluate Gal1-R pharmacology and physiology, we studied T84 cells. Gal1-R expressed by these cells bound galanin rapidly (half time 1–2 min) and with high affinity (inhibitor constant 0.7 ± 0.2 nM). T84 cells were then studied in a modified Ussing chamber and alterations in Isc, a measure of all ion movement across the tissue, were determined. Maximal increases in Iscwere observed in a concentration-dependent manner around 2 min after stimulation with peptide, with 1 μM galanin causing Iscto rise more than eightfold and return to baseline occurring within 10 min. The increase in galanin-induced Iscwas shown by125I efflux studies to be due to Cl−secretion, which occurred independently of alterations in cAMP and phospholipase C. Rather, Cl−secretion is mediated via a Ca2+-dependent, pertussis toxin-sensitive mechanism. These data suggest that galanin released by enteric nerves may act as a secretagogue in the human colon by activating Gal1-R.
Effects of systemic hypotension on postnatal intestinal circulation: role of angiotensin
Authors: Nowicki Philip T. , Minnich Lisa A.
Published: December 2017

Systemic hypotension causes a greater degree of vasoconstriction in intestine from 3- than from 35-day-old postnatal swine. To determine the basis for this age-dependent difference, systemic hypotension (pressure reduction to ∼50% of baseline) was induced by creating pericardial tamponade in postnatal swine instrumented to allow measurement of intestinal hemodynamics and oxygenation in vivo. Hypotension caused gut vascular resistance to increase 77 ± 6% in 3-day-old subjects but only 18 ± 3% in 35-day-old subjects. Prior blockade of α1-receptors with phentolamine, vasopressin receptors with [d(CH2)5,d-Phe2,Ile4,Ala9-NH2]AVP, or surgical denervation of the gut loop had no effect on hypotension-induced gut vasoconstriction. Losartan, which blocks angiotensin AT1 receptors, significantly attenuated hypotension-induced gut vasoconstriction in both age groups. BQ-610, which blocks endothelin ETA receptors, also limited the magnitude of vasoconstriction but only in younger subjects. This effect may have been consequent to an interaction between endothelin and angiotensin, inasmuch as a subpressor concentration of endothelin increased the contractile response to angiotensin in mesenteric artery rings. The substantial rise in 3-day-old gut vascular resistance was partly consequent to a locally mediated vasoconstriction that occurred in response to pressure and/or flow reduction during hypotension, as evidenced by the significant attenuation of this constriction when blood flow was held constant by controlled-flow perfusion to the gut loop during hypotension. Intestinal O2 uptake was compromised to a significantly greater degree in 3- than in 35-day-old subjects during hypotension. This difference was primarily due to the inability of younger intestine to increase O2extraction in the face of reduced blood flow and may be mediated, in part, by an effect of angiotensin II on intestinal capillary perfusion.
Voltage sensitivity of slow wave frequency in isolated circular muscle strips from guinea pig gastric antrum
Authors: Huang S.-M. , Nakayama S. , Iino S. , Tomita T.
Published: December 2017

In circular muscle preparations isolated from the guinea pig gastric antrum, regular spontaneous electrical activity (slow waves) was recorded. Under normal conditions (6 mM K+), the frequency and shape of the slow waves were similar to those observed in ordinary stomach smooth muscle preparations. When the resting membrane potential was hyperpolarized and depolarized by changing the extracellular K+ concentration (2–18 mM), the frequency of slow waves decreased and increased, respectively. Application of cromakalim hyperpolarized the cell membrane and reduced the frequency of slow waves in a dose-dependent manner. Cromakalim (3 μM) hyperpolarized the membrane, and slow waves ceased in most preparations. In the presence of cromakalim, subsequent increases in the extracellular K+ concentration restored the frequency of slow waves accompanied by depolarization. Also, glibenclamide completely antagonized this effect of cromakalim. In smooth muscle strips containing both circular and longitudinal muscle layers, such changes in the slow wave frequency were not observed. It was concluded that the maneuver of isolating circular smooth muscle altered the voltage dependence of the slow wave frequency.
Downregulation of Gαq-11protein expression in guinea pig antral and colonic circular muscle during pregnancy
Authors: Chen Qian , Xiao Zuo-Liang , Biancani Piero , Behar Jose
Published: December 2017

Pregnancy has an inhibitory effect on motility of the gastrointestinal tract. The present study was designed to examine the mechanisms responsible for antral and colonic hypomotility in pregnant guinea pigs. Circular smooth muscle cells from the antrum and left colon were isolated by enzymatic digestion with collagenase from pregnant and nonpregnant guinea pigs. Contractile responses to agonists were expressed as percent shortening from resting cell length. The function of G proteins in antral and colonic circular smooth muscle was assessed by [35S]guanosine 5′- O-(3-thiotriphosphate) (GTPγS) binding induced by CCK-8 and G protein quantitation. The contraction of antral and colonic circular smooth muscle from pregnant guinea pigs was reduced in response to CCK-8 and to GTPγS but was normal in response to KCl andd- myo-inositol 1,4,5-trisphosphate compared with nonpregnant animals. The stimulation of [35S]GTPγS binding to Gαq-11induced by 1 μM CCK-8 was significantly lower in antral and colonic circular smooth muscle from pregnant guinea pigs than that in controls. Furthermore, Western blot analysis showed a decreased Gαq-11and an increased Gsα protein content in both tissues during pregnancy. It is concluded that pregnancy appears to impair gastrointestinal circular smooth muscle contractility by downregulating G proteins such as Gαq-11protein, which mediates muscle contraction, and upregulating Gsα protein, which mediates muscle relaxation.
Receptor-mediated vascular and metabolic actions of endothelin-1 in canine small intestine
Authors: King-VanVlack Cheryl E. , Mewburn Jeffrey D. , Chapler Christopher K.
Published: December 2017

The effects of endothelin-1 (ET-1) infusion on blood flow (Q˙G) and O2 uptake (V˙o 2G) were examined in the small intestine of anesthetized dogs ( n = 10). Arterial and venous flows of a gut segment were isolated, and the segment was perfused at constant pressure. Arterial and gut venous blood samples were taken, gut perfusion pressure andQ˙G were measured, and O2 extraction ratio (OERG) andV˙o 2Gwere calculated. ET-1 was infused (0.118 μg ⋅ kg−1 ⋅ min−1ia) throughout the experiment. In group 1 ( n = 5), ETA receptors were blocked using BQ-123 (0.143 mg ⋅ kg−1 ⋅ min−1ia) followed by blockade of ETBreceptors with BQ-788 (0.145 mg ⋅ kg−1 ⋅ min−1ia). The order of ETA and ETB receptor blockade was reversed in group 2( n = 5). In group 1, the decrease inQ˙G observed with ET-1 infusion was partially reversed with BQ-123; no further change occurred after BQ-788 administration. In group 2, addition of BQ-788 to the infusate further decreasedQ˙G, whereas addition of BQ-123 returnedQ˙G to a value not different from that with ET-1 infusion alone. These data indicated that ET-1-induced vasoconstriction in the gut was mediated via ETA receptors and that this constriction was buffered by activation of ETB receptors.V˙o 2Gdecreased in proportion to the decrease inQ˙G with ET-1, decreased further with ET-1 plus ETB receptor blockade ( group 2), and increased in proportion to the increases in Q˙Gwith ETA receptor blockade (both groups). No changes in OERGoccurred during ETA and ETB receptor antagonism in either group. This study is the first to demonstrate that a flow-limited decrease in gutV˙o 2Goccurred with infusion of ET-1 in gut vasculature. An intriguing and novel finding was that, during O2limitation, OERG was only 50% of that normally associated with ischemia in this tissue.
Gastrointestinal responses to a panel of lectins in rats maintained on total parenteral nutrition
Authors: Jordinson Mark , Goodlad Robert A. , Brynes Audrey , Bliss Philip , Ghatei Mohammad A. , Bloom Stephen R. , Fitzgerald Anthony , Grant George , Bardocz Susan , Pusztai Arpad , Pignatelli Massimo , Calam John
Published: December 2017

Total parenteral nutrition (TPN) causes atrophy of gastrointestinal epithelia, so we asked whether lectins that stimulate epithelial proliferation can reverse this effect of TPN. Two lectins stimulate pancreatic proliferation by releasing CCK, so we asked whether lectins that stimulate gastrointestinal proliferation also release hormones that might mediate their effects. Six rats per group received continuous infusion of TPN and a once daily bolus dose of purified lectin (25 mg ⋅ rat−1 ⋅ day−1) or vehicle alone (control group) for 4 days via an intragastric cannula. Proliferation rates were estimated by metaphase arrest, and hormones were measured by RIAs. Phytohemagglutinin (PHA) increased proliferation by 90% in the gastric fundus ( P < 0.05), doubled proliferation in the small intestine ( P < 0.001), and had a small effect in the midcolon ( P< 0.05). Peanut agglutinin (PNA) had a minor trophic effect in the proximal small intestine ( P < 0.05) and increased proliferation by 166% in the proximal colon ( P < 0.001) and by 40% in the midcolon ( P < 0.001). PNA elevated circulating gastrin and CCK by 97 ( P< 0.05) and 81% ( P < 0.01), respectively, and PHA elevated plasma enteroglucagon by 69% and CCK by 60% (both P < 0.05). Only wheat germ agglutinin increased the release of glucagon-like peptide-1 by 100% ( P < 0.05). PHA and PNA consistently reverse the fall in gastrointestinal and pancreatic growth associated with TPN in rats. Both lectins stimulated the release of specific hormones that may have been responsible for the trophic effects. It is suggested that lectins could be used to prevent gastrointestinal atrophy during TPN. Their hormone-releasing effects might be involved.
Partial hepatectomy-induced polyploidy attenuates hepatocyte replication and activates cell aging events
Authors: Sigal Samuel H. , Rajvanshi Pankaj , Gorla Giridhar R. , Sokhi Rana P. , Saxena Romil , Gebhard David R. , Reid Lola M. , Gupta Sanjeev
Published: December 2017

In understanding mechanisms of liver repopulation with transplanted hepatocytes, we studied the consequences of hepatic polyploidization in the two-thirds partial hepatectomy model of liver regeneration. Liver repopulation studies using genetically marked rodent hepatocytes showed that the number of previously transplanted hepatocytes did not increase in the liver with subsequential partial hepatectomy. In contrast, recipients undergoing partial hepatectomy before cells were transplanted showed proliferation in transplanted hepatocytes, with kinetics of DNA synthesis differing in transplanted and host hepatocytes. Also, partial hepatectomy caused multiple changes in the rat liver, including accumulation of polyploid hepatocytes along with prolonged depletion of diploid hepatocytes, as well as increased senescence-associated β-galactosidase and p21 expression. Remnant hepatocytes in the partially hepatectomized liver showed increased autofluorescence and cytoplasmic complexity on flow cytometry, which are associated with lipofuscin accumulation during cell aging, and underwent apoptosis more frequently. Moreover, hepatocytes from the partially hepatectomized liver showed attenuated proliferative capacity in cell culture. These findings were compatible with decreased proliferative potential of hepatocytes experiencing partial hepatectomy compared with hepatocytes from the unperturbed liver. Attenuation of proliferative capacity and other changes in hepatocytes experiencing partial hepatectomy offer novel perspectives concerning liver regeneration in the context of cell ploidy.
Cell type-specific requirement of the MAPK pathway for the growth factor action of gastrin
Authors: Stepan Vinzenz M. , Dickinson Chris J. , del Valle John , Matsushima Masashi , Todisco Andrea
Published: December 2017

Gastrin (G17) has a CCKBreceptor-mediated growth-promoting effect on the AR42J rat acinar cell line that is linked to induction of both mitogen-activated protein kinase (MAPK) and c- fos gene expression. We investigated the mechanisms that regulate the growth factor action of G17 on the rat pituitary adenoma cell line GH3. Both AR42J and GH3cells displayed equal levels of CCKBreceptor expression and similar binding kinetics of125I-labeled G17. G17 stimulation of cell proliferation was identical in both cell lines. G17 stimulation of GH3cell proliferation was completely blocked by the CCKBreceptor antagonist D2 but not by the MEK inhibitor PD-98059 or the protein kinase C inhibitor GF-109203X, which completely inhibited G17 induction of AR42J cell proliferation. G17 induced a c- fos SRE-luciferase reporter gene plasmid more than fourfold in the AR42J cells, whereas it had no effect in the GH3cells. In contrast to what we observed in the AR42J cells, G17 failed to stimulate MAPK activation and Shc tyrosyl phosphorylation and association with the adapter protein Grb2. Epidermal growth factor induced the MAPK pathway in the GH3cells, demonstrating the integrity of this signaling system. G17 induced Ca2+mobilization in both the GH3and AR42J cells. The calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide inhibited AR42J cell proliferation by 20%, whereas it completely blocked G17 induction of GH3cell growth. The Ca2+ionophore ionomycin stimulated GH3cell proliferation to a level similar to that observed in response to G17, but it had no effect on AR42J cell proliferation. Thus there are cell type specific differences in the requirement of the MAPK pathway for the growth factor action of G17. Whereas in the AR42J cells G17 stimulates cell growth through activation of MAPK and c- fos gene expression, in the GH3cells, G17 fails to activate MAPK, and it induces cell proliferation through Ca2+-dependent signaling pathways. Furthermore, induction of Ca2+mobilization in the AR42J cells appears not to be sufficient to sustain cell proliferation.
Blockade of hepatic nitric oxide synthase causes insulin resistance
Authors: Sadri Parissa , Lautt W. Wayne
Published: December 2017

The hypothesis was tested that insulin sensitivity, previously shown to depend on a functional hepatic parasympathetic reflex, was mediated by hepatic production of nitric oxide (NO). Insulin sensitivity was measured using the rapid insulin sensitivity test. N-nitro-l-arginine methyl ester (l-NAME, 2.5 and 5.0 mg/kg iv) and N-monomethyl-l-arginine (l-NMMA, 0.73 mg/kg), nitric oxide synthase (NOS) antagonists, caused insulin resistance in rats. Intraportal administration ofl-NAME at a dose of 1.0 mg/kg significantly reduced the response to insulin (54.9 ± 5.2%); however, administration of the same dose ofl-NAME intravenously did not cause a significant decrease in insulin response. Intraportal, but not intravenous, administration of 3-morpholinosydnonimine (SIN-1, 5.0 mg/kg), a NO donor, partially reversed the insulin resistance caused byl-NMMA. Intraportal administration of SIN-1 (10.0 mg/kg) completely restored insulin sensitivity after l-NMMA or surgical denervation of the liver. Insulin resistance produced by denervation was not further increased by NOS blockade. These results suggest that blockade of NOS causes peripheral insulin resistance secondary to blockade of the hepatic parasympathetic reflex release of hepatic insulin-sensitizing substance in response to insulin.
Ion transport across the normal and CF neonatal murine intestine
Authors: Grubb B. R.
Published: December 2017

Neonatal mice with cystic fibrosis (CF) exhibit a very high mortality due to intestinal obstruction localized primarily to the ileum and colon. It has been hypothesized that lack of Cl− secretion and possibly elevated Na+ absorption contribute to the gut problems in CF neonates. Therefore, intestines (ileum, proximal colon, and distal colon) from normal and CF day-old mouse pups were studied on ultra-small-aperture (0.0135 cm2) Ussing chambers. All three regions of the normal neonatal intestine responded to forskolin with an increase in short-circuit current, which was completely absent in the CF intestine. The neonatal distal colon exhibited a high rate of amiloride-sensitive electrogenic Na+ absorption, which did not differ between the normal and CF preparations. The ileum and proximal colon of both genotypes exhibited a small but significant electrogenic Na+ absorption. The neonatal proximal colon and ileum also exhibited electrogenic Na+-glucose cotransport, which was significantly greater in the normal compared with the CF ileum. In addition, all three intestinal regions exhibited electrogenic Na+-alanine cotransport, which was significantly reduced in two of the regions of the CF neonatal intestine. It is speculated that: 1) the reduced rate of Na+-nutrient cotransport in the CF intestine contributes to the lower rate of growth in CF pups, whereas 2) the elevated electrogenic Na+ absorption in the neonatal intestine, coupled with an inability to secrete Cl−, contributes to the intestinal obstruction in the CF pups.
Bacterial cell wall polymers promote intestinal fibrosis by direct stimulation of myofibroblasts
Authors: van Tol Eric A. F. , Holt Lisa , Li Feng Ling , Kong Feng-Ming , Rippe Richard , Yamauchi Mitsuo , Pucilowska Jolanta , Lund P. Kay , Sartor R. Balfour
Published: December 2017

Normal luminal bacteria and bacterial cell wall polymers are implicated in the pathogenesis of chronic intestinal inflammation. To determine the direct involvement of bacteria and their products on intestinal fibrogenesis, the effects of purified bacterial cell wall polymers on collagen and cytokine synthesis were evaluated in intestinal myofibroblast cultures established from normal fetal and chronically inflamed cecal tissues. In this study, the intestines of Lewis rats were intramurally injected with peptidoglycan-polysaccharide polymers. Collagen and transforming growth factor (TGF)-β1 mRNA levels were measured and correlated with mesenchymal cell accumulation by immunohistochemistry. The direct effects of cell wall polymers on fibrogenic cytokine and collagen α1 (type I) expression were evaluated in intestinal myofibroblast cultures. We found that intramural injections of bacterial cell wall polymers induced chronic granulomatous enterocolitis with markedly increased collagen synthesis and concomitant increased TGF-β1 and interleukin (IL)-6 expression. Intestinal myofibroblast cultures were established, which both phenotypically and functionally resemble the mesenchymal cells that are involved in fibrosis in vivo. Bacterial cell wall polymers directly stimulated collagen α1 (I), TGF-β1, IL-1β, and IL-6 mRNA expression in the intestinal myofibroblasts derived from both normal and inflamed cecum. Neutralization of endogenous TGF-β1 inhibited in vitro collagen gene expression. From our results, we conclude that increased exposure to luminal bacterial products can directly activate intestinal mesenchymal cells, which accumulate in areas of chronic intestinal inflammation, thus stimulating intestinal fibrosis in genetically susceptible hosts.
I. Physiological studies with gastrin in transgenic mice
Authors: Wang Timothy C. , Dockray Graham J.
Published: December 2017

The role of gastrin in the regulation of gastrointestinal growth and acid secretion has been addressed through recent studies involving transgenic and knockout mice. The role of gastrin as a key modulator of parietal cell function and gastric acid secretion has been confirmed through studies in mice deficient in either gastrin or the gastrin/CCK-B receptor. However, although gastrin-deficient mice show no changes in gastric proliferation, they do show reduced colonic proliferation, and rates of colonic proliferation are increased in transgenic mice overexpressing glycine-extended gastrin or progastrin. This themes article highlights recent progress in our understanding of the biology of gastrin through studies in genetically modified mice.
Acid-sensing pathways of rat duodenum
Authors: Akiba Yasutada , Guth Paul H. , Engel Eli , Nastaskin Igor , Kaunitz Jonathan D.
Published: December 2017

We tested the hypothesis that the duodenal hyperemic response to acid occurs through activation of capsaicin-sensitive afferent nerves with subsequent release of vasodilatory substances such as calcitonin gene-related peptide (CGRP) and nitric oxide (NO). Laser-Doppler flowmetry was used to measure duodenal blood flow in urethan-anesthetized rats. Duodenal mucosa was superfused with pH 7.0 buffer with capsaicin or bradykinin or was acid challenged with pH 2.2 solution, with or without vanilloid receptor antagonists, a CGRP receptor antagonist, an NO synthase (NOS) inhibitor, or a cyclooxygenase inhibitor. The selective vanilloid receptor antagonist capsazepine (CPZ) dose dependently inhibited the hyperemic response to acid and capsaicin but did not affect bradykinin-induced hyperemia. Ruthenium red was less inhibitory than capsazepine. Selective ablation of capsaicin-sensitive nerves, CGRP-(8—37), and N G-nitro-l-arginine methyl ester inhibited acid-induced hyperemia, but indomethacin did not. We conclude that luminal acid, but not bradykinin, stimulates CPZ-sensitive receptors on capsaicin-sensitive afferent nerves of rat duodenum. Activation of these receptors produces vasodilation via the CGRP-NO pathway but not via the cyclooxygenase pathway. Acid appears to be the endogenous ligand for duodenal vanilloid receptors.
Differential inflammatory modulation of canine ileal longitudinal and circular muscle cells
Authors: Shi Xuan-Zheng , Sarna Sushil K.
Published: December 2017

The aim of this study was to identify the subtypes of muscarinic receptors that mediate in vivo and in vitro canine ileal longitudinal muscle contractions and whether their role is modulated by inflammation. Previous studies have reported that circular muscle contractions are suppressed in ileal inflammation induced by mucosal exposure to ethanol and acetic acid. We found that inflammation had no significant effect on in vivo and in vitro spontaneous or muscarinic receptor-mediated contractions of the longitudinal muscle. The longitudinal muscle contractions were mediated primarily by the M3 receptor subtype. However, the IC50 of the M2 receptor antagonist methoctramine was only 10 times greater than that of the M3 receptor antagonist 4-DAMP in the longitudinal muscle, whereas it was 224 times greater in the circular muscle. M2receptor-coupled decrease of intracellular cAMP occurred in the longitudinal but not in the circular muscle from the normal ileum. Inflammation did not alter this coupling in the longitudinal muscle but established it in the circular muscle. In conclusion, M2 receptors may play a greater role in the mediation of longitudinal muscle contractions than circular muscle contractions. Inflammation does not alter the contractility or the relative role of muscarinic receptor subtypes in longitudinal muscle cells. However, it modulates the M2 receptor coupling to adenylate cyclase in the circular muscle.
Hsp90 regulation of endothelial nitric oxide synthase contributes to vascular control in portal hypertension
Authors: Shah Vijay , Wiest Reiner , Garcia-Cardena Guillermo , Cadelina Greg , Groszmann Roberto J. , Sessa William C.
Published: December 2017

The molecular chaperone, heat shock protein 90 (Hsp90), acts as an intermediate in the signaling cascades leading to activation of endothelial nitric oxide synthase (eNOS). In this study, we examine the participation of this pathway in nitric oxide (NO)-dependent vasodilation in the rat mesentery in vitro. In normal animals, immunoprecipitation of eNOS from intact mesentery coimmunoprecipitates Hsp90 and, additionally, both eNOS and Hsp90 colocalize to the endothelial lining of mesenteric vessels. In the perfused mesenteric vasculature of normal animals, geldanamycin (GA), a specific inhibitor of Hsp90 signaling, attenuates ACh-dependent vasodilation but does not affect vasodilation in response to sodium nitroprusside. Next, studies were performed in animals with experimental portal hypertension induced by portal vein ligation (PVL). In PVL animals, NOS catalytic activity is markedly enhanced in mesenteric tissue and the perfused mesentery is hyporesponsive to the vasoconstrictor methoxamine (MTX). GA significantly potentiates MTX-induced vasoconstriction after PVL, thereby partially reversing the hyporeactivity to this agent exhibited in the mesenteric vasculature after PVL. These studies suggest that Hsp90 can act as a signaling mediator of NO-dependent responses in the mesenteric circulation and indicate that the excessive NO production observed in portal hypertension is mediated in part through Hsp90 signaling.
Ammonia blockade of intestinal epithelial K+ conductance
Authors: Hrnjez Bruce J. , Song Jaekyung C. , Prasad Madhu , Mayol Julio M. , Matthews Jeffrey B.
Published: December 2017

Ammonia profoundly inhibits cAMP-dependent Cl− secretion in model T84 human intestinal crypt epithelia. Because colonic lumen concentrations of ammonia are high (10–70 mM), ammonia may be a novel regulator of secretory diarrheal responsiveness. We defined the target of ammonia action by structure-function analysis with a series of primary amines (ammonia, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, and octylamine) that vary principally in size and lipid solubilities. The amine concentrations required for 50% inhibition of Cl− secretion in intact monolayers and 50% inhibition of outward K+ current ( I K) in apically permeabilized monolayers vs. the logs of the respective amine partition coefficients give two plots that are strikingly similar in character. Half-maximal inhibition of short-circuit current ( I sc) by ammonia was seen at 6 mM and for I K at 4 mM; half-maximal inhibition for octylamine was 0.24 mM and 0.19 mM for I sc and I K, respectively. The preferentially water-soluble hydrophilic amines (ammonia, methylamine, ethylamine) increase in blocking ability with decreasing size and lipophilicity. Conversely, the preferentially lipid-soluble hydrophobic (propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine) amines increase in blocking ability with increasing size and lipophilicity. Ammonia does not affect isolated apical Cl− conductance; amine-induced changes in cytosolic and endosomal pH do not correlate with secretory inhibition. We propose that ammonia in its protonated ammonium form ([Formula: see text]) inhibits cAMP-dependent Cl− secretion in T84 monolayers by blocking basolateral K+ channels.
Biphasic relaxation of the opossum lower esophageal sphincter: roles of NO ⋅, VIP, and CGRP
Authors: Uc Aliye , Oh S. T. , Murray Joseph A. , Clark Eugene , Conklin Jeffrey L.
Published: December 2017

Vasoactive intestinal polypeptide (VIP) and nitric oxide (NO ⋅) are thought to mediate lower esophageal sphincter (LES) relaxation. Transverse muscle strips from the opossum LES were used to test this hypothesis. Electrical field stimulation (EFS) produced a biphasic LES relaxation: a rapid component during the stimulus was more prominent at lower stimulus frequencies, and a sustained component was more prominent at higher frequencies. N ω-nitro-l-arginine and hemoglobin inhibited the rapid component but affected the sustained component less. Exogenous VIP decreased LES tone. A number of purported VIP antagonists blocked neither VIP-induced nor EFS-induced relaxation of the LES. The calcitonin gene-related peptide (CGRP) antagonist CGRP-(8—37) did not alter EFS-induced LES relaxation. EFS-induced relaxation of opossum LES muscle is biphasic, and the initial, rapid component of the relaxation is mediated primarily by NO ⋅. The mediator of the sustained component was not identified.
Cerebral topography of rectal stimulation using single photon emission computed tomography
Authors: Bouras Ernest P. , O’Brien Terence J. , Camilleri Michael , O’Connor Michael K. , Mullan Brian P.
Published: December 2017

Central processing of visceral information in humans is incompletely understood. We aimed to demonstrate the feasibility of single photon emission computed tomography (SPECT) and to quantitate the changes in regional cerebral blood flow during rectal distension. Ten healthy volunteers underwent randomized sham and active rectal distensions on separate days, during which cerebral blood flow was assessed by intravenous technetium-99m ethyl cysteinate dimer (99mTc-ECD) SPECT. Three-dimensional coregistration of brain images was used to quantitate activation in four preselected cerebral foci and two control regions. Paired analysis compared blood flow during sham and active distensions. There was increased right anterior cingulate gyrus activity (6.5 ± 2.9%, P = 0.03) with active rectal distension. A 5.4 ± 2.4% reduction in blood flow in the superior parieto-occipital control region ( P = 0.04) suggested blood “redistribution” during stimulation. Marked variability in activation of the frontal cortex, thalamus/basal ganglia complex, and mesiotemporal lobe was noted. Thus rectal distension increases activity in the right anterior cingulate gyrus on average; other foci of cerebral activation are quite variable, suggesting a lack of specific cerebral projections during rectal stimulation.
Carbon monoxide disposition in the perfused rat liver
Authors: le Couteur David G. , Yin Zhan Li , Rivory Laurent P. , McLean Allan J.
Published: December 2017

A simple method for determining carbon monoxide (CO) disposition in the rat liver perfused with erythrocyte-free buffer was developed. Wash-in experiments were performed with buffer containing tracer quantities of [14C]sucrose and3H2O and equilibrated with CO. Outflow samples were collected into tubes containing human erythrocytes, which avidly bind CO. Outflow curves were analyzed using compartmental models. Fractional recovery of CO was 1.07 ± 0.17, and the apparent volume of distribution was 1.37 ± 0.30 ml/g of liver ( n = 8). A flow-limited model fitted the data most effectively, although estimates of the permeability-to-surface area product were attempted using a barrier-limited model. This technique will facilitate investigation of the effects of disease on gaseous substrate disposition in perfused organs.
Mechanical stretch modulates TGF-β1 and α1(I) collagen expression in fetal human intestinal smooth muscle cells
Authors: Gutierrez Jorge A. , Perr Hilary A.
Published: December 2017

Intestinal muscle undergoes stretch intermittently during peristalsis and persistently proximal to obstruction. The influence of this pervasive biomechanical force on developing smooth muscle cell function remains unknown. We adapted a novel in vitro system to study whether stretch modulates transforming growth factor-β1 (TGF-β1) and type I collagen protein and component α1 chain [α1(I) collagen] expression in fetal human intestinal smooth muscle cells. Primary confluent cells at 20-wk gestation, cultured on flexible silicone membranes, were subjected to two brief stretches or to 18 h tonic stretch. Nonstretched cultures served as controls. TGF-β1 protein was measured by ELISA and type I collagen protein was assayed by Western blot. TGF-β1 and α1(I) collagen mRNA abundance was determined by Northern blot analysis, quantitated by phosphorimaging, and normalized to 18S rRNA. Transcription was examined by nuclear run-on assay. Tonic stretch increased TGF-β1 protein 40%, type I collagen protein 100%, TGF-β1 mRNA content 2.16-fold, and α1(I) collagen mRNA 3.80-fold and enhanced transcription of TGF-β1 and α1(I) collagen by 3.1- and 4.25-fold, respectively. Brief stretch stimulated a 50% increase in TGF-β1 mRNA content but no change in α1(I) collagen. Neutralizing anti-TGF-β1 ablated stretch-mediated effects on α1(I) collagen. Therefore, stretch upregulates transcription for TGF-β1, which stimulates α1(I) collagen gene expression in smooth muscle from developing gut.
Nitric oxide mediates hepatic arterial vascular escape from norepinephrine-induced constriction
Authors: Ming Zhi , Han Chao , Lautt W. Wayne
Published: December 2017

The involvement of nitric oxide (NO) in the vascular escape from norepinephrine (NE)-induced vasoconstriction was investigated in the hepatic arterial vasculature of anesthetized cats. The hepatic artery was perfused by free blood flow or pump-controlled constant-flow, and NE (0.15 and 0.3 μg ⋅ kg−1 ⋅ min−1, respectively) was infused through the portal vein. In the free-flow perfusion model, the NE-induced hepatic vasoconstriction recovered from the maximum point of the constriction, resulting in 36.6 ± 5.9% vascular escape. Blockade of NO formation with N ω-nitro-l-arginine methyl ester (l-NAME, 2.5 mg/kg ipv) potentiated NE-induced maximum vasoconstriction, and the potentiation was reversed byl-arginine (75 mg/kg ipv). Furthermore, NE-induced vasoconstriction became more stable after l-NAME, resulting in an inhibition of vascular escape (7.5 ± 3.3%), and the inhibition was reversed by l-arginine (23.0 ± 6.4%). Similar potentiation of NE-induced vasoconstriction and inhibition of hepatic vascular escape by l-NAME (40.4 ± 4.3% control vs. 10.2 ± 3.7% post-l-NAME escape) and the reversal byl-arginine were also observed in the constant-flow perfusion model. The data suggest that NO is the major endogenous mediator involved in the hepatic vascular escape from NE-induced vasoconstriction.
Desensitization to LPS after ethanol involves the effect of endotoxin on voltage-dependent calcium channels
Authors: Enomoto Nobuyuki , Yamashina Shunhei , Goto Moritaka , Schemmer Peter , Thurman Ronald G.
Published: December 2017

Hepatic macrophages are sensitized to alcohol in 24 h due to increases in the endotoxin receptor, CD14; however, desensitization to lipopolysaccharide (LPS), which occurred earlier, could not be explained by changes in CD14. Therefore, the purpose of this work was to attempt to understand factors responsible for ethanol-induced desensitization to LPS in hepatic macrophages. Rats were given ethanol (5 g/kg body wt) intragastrically, and hepatic macrophages were isolated 2 h later. After addition of endotoxin, intracellular Ca2+concentration ([Ca2+]i) was measured using fura 2 and tumor necrosis factor (TNF)-α was measured by ELISA. Ethanol given 2 h before injection of LPS totally prevented liver injury and blunted LPS-induced increases in [Ca2+]iand TNF-α in hepatic macrophages. Furthermore, the protein kinase C (PKC) agonist phorbol 12-myristate 13-acetate and acute ethanol treatment both activated PKC and largely prevented the influx of [Ca2+]icaused by LPS. Sterilization of the gut with antibiotics completely blocked all effects of ethanol on [Ca2+]iand TNF-α release. Thus ethanol-induced desensitization of hepatic macrophages correlates with gut-derived endotoxin after ethanol and involves the effect of PKC on voltage-dependent Ca2+channels.
Inhibition of rat colon tumors by sulindac and sulindac sulfone is independent of K-ras (codon 12) mutation
Authors: de Jong Tanya A. , Skinner Stewart A. , Malcontenti-Wilson Cathy , Vogiagis Daphne , Bailey Michael , van Driel Ian R. , O'Brien Paul E.
Published: December 2017

Nonsteroidal anti-inflammatory drug (NSAID) use reduces the risk of colorectal cancer by 40–50%. Previous studies suggest that effective inhibition of colorectal cancer by NSAIDs may be dependent on the presence or absence of a K-ras mutation. This study was aimed at determining the relationship between inhibition of colorectal cancer by sulindac and sulindac sulfone and the presence of activating K-ras mutations in the 1,2-dimethylhydrazine dihydrochloride rat model. Sulindac (20 mg ⋅ kg−1 ⋅ day−1), sulindac sulfone (40 mg ⋅ kg−1 ⋅ day−1), or vehicle was administered orally to male Sprague-Dawley rats for a 4-wk period beginning 20 wk after tumor induction. Tumor number and volume were measured before treatment by laparotomy and colonoscopy and again after treatment. Sulindac and sulindac sulfone treatment significantly reduced the number and volume of colorectal tumors compared with control rats. For K-ras (codon 12) mutation detection, frozen tumor tissue was collected at the endpoint. We found K-ras codon 12 mutations in 11 of 21 (52%) control tumors. The proportion of tumors with K-ras mutations in the sulindac-treated group [5 of 8 (62%); odds ratio = 1.51 (95% confidence interval = 0.29, 8.33)] and the proportion of sulindac sulfone-treated tumors [9 of 14 (64%); odds ratio = 1.63 (95% confidence interval = 0.41, 6.66)] were not significantly different from controls. Tumor inhibition did not correlate with K-ras (codon 12) mutation status, which suggests that the mechanism of inhibition of rat colorectal cancer by sulindac and sulindac sulfone is independent of K-ras mutation.
MRP2, a human conjugate export pump, is present and transports fluo 3 into apical vacuoles of Hep G2 cells
Authors: Cantz Tobias , Nies Anne T. , Brom Manuela , Hofmann Alan F. , Keppler Dietrich
Published: December 2017

The multidrug resistance protein 2 (MRP2, symbol ABCC2) transports anionic conjugates and certain amphiphilic anions across the apical membrane of polarized cells. Human hepatoma Hep G2 cells retain hepatic polarity and form apical vacuoles into which cholephilic substances are secreted. Immunofluorescence microscopy showed that human MRP2 was expressed in the apical vacuole membrane of polarized Hep G2 cells, whereas the isoform MRP3 was localized to the lateral membrane. Expression of both MRP2 and MRP3 was confirmed by immunoblotting and reverse transcription PCR. Fluo 3 secretion into the apical vacuoles was inhibited by cyclosporin A but not by selective inhibitors of multidrug resistance 1 P-glycoprotein. In addition, carboxyfluorescein, rhodamine 123, and the fluorescent bile salt derivatives ursodeoxycholyl-(Nε-nitrobenzoxadiazolyl)-lysine and cholylglycylamido-fluorescein were secreted into the apical vacuoles; the latter two probably via the bile salt export pump. We conclude that MRP2 mediates fluo 3 secretion into the apical vacuoles of polarized Hep G2 cells. Thus the function of human MRP2 and the action of inhibitors can be analyzed by the secretion of fluorescent anions such as fluo 3.