bluuebunny/crossref_metadata_2025 huggingface dataset:
Impaired stimulation of intestinal glucose absorption via hepatoenteral nerves in streptozotocin-diabetic rats
Authors: Stümpel Frank , Kucera Tomas , Jungermann Kurt
Published: December 2017

In an ex situ organ perfusion system, that of the isolated nonrecirculating joint perfusion of rat small intestine and liver, insulin infused into the portal vein increased intestinal glucose absorption. This insulin action against the bloodstream can be blocked by TTX, indicating a propagation of the insulin signal via hepatoenteral nerves, which conforms with previous studies with atropine and carbachol. Insulin action could also be mimicked by dibutyryl cAMP (DBcAMP) acting directly on the absorptive enterocytes. Because autonomic neuropathy is a common late complication of diabetes mellitus, the possible impairment of these nerves in the diabetic state was studied in streptozotocin-diabetic rats. In the isolated joint intestine-liver perfusion, glucose was applied as a bolus into the lumen; its absorption was measured in the portal vein. In 5-day diabetic as well as in control rats, portal insulin, arterial carbachol, and arterial DBcAMP increased intestinal glucose absorption. In 3-mo diabetic rats portal insulin and arterial carbachol failed to stimulate glucose absorption, whereas arterial DBcAMP still did so, indicating an undisturbed function of the absorptive enterocytes. The lack of an effect of portal insulin and arterial carbachol and the unchanged action of DBcAMP in the chronically diabetic rats indicated that the signaling chain via the hepatoenteral nerves was impaired, which is in line with a diabetic neuropathy.
Hepatic artery buffer response following left portal vein ligation: its role in liver tissue homeostasis
Authors: Rocheleau B. , Éthier C. , Houle R. , Huet P. M. , Bilodeau M.
Published: December 2017

Occlusion of a lobar portal vein is known to induce atrophy of downstream liver lobes and hypertrophy of contralateral lobes. Changes in portal flow are known to be compensated by changes in hepatic arterial flow, thus defining the hepatic artery buffer response (HABR). To understand the role of liver flow in liver atrophy, we measured portal flow and hepatic artery flow after different degrees of left portal vein stenosis (LPVS). Surgery was performed to obtain 0, 43, 48, 59, 68, 72, 78, and 100% LPVS. Systemic and splanchnic blood flows were measured at 4 h or 7 days after surgery using radiolabeled microspheres. At 4 h, LPVS produced no changes in systemic hemodynamics. Increasing degrees of LPVS produced a significant decrease in left portal flow ( P < 0.0001) and a fully compensatory increase in right portal flow ( P < 0.0001) without significantly affecting total portal flow. Left hepatic artery flow increased by 210% ( P = 0.002), and right hepatic artery flow decreased by 67% ( P = 0.05) after full LPVS. There was a significant inverse correlation between portal and arterial flow changes induced by different degrees of LPVS in the left ( r 2 = 0.61) and right ( r 2 = 0.41) lobes. Despite this HABR, we observed a reduction in left liver flow (−45%; P = 0.01) and an increase in right liver flow (+230%; P = 0.01) with 100% LPVS. At 7 days, a significant decrease in the weight of left liver lobes (−75%; P < 0.0001) and a compensatory increase in the weight of the right lobes (+210%; P < 0.0001) were observed with 100% LPVS. Left and right liver flows were similar to results measured at 4 h, and HABR was still present. However, when expressed per gram of liver, liver flows were identical to results obtained with sham animals. Reduction in lobar portal flow is accompanied by an increase in ipsilateral hepatic artery flow and a compensatory increase in portal flow to the rest of the liver. In a given lobe, when compensatory HABR is overcome, liver weight changes occur so that at the end total liver flow per gram of liver tissue is restored. This suggests that in normal conditions liver flow is a major regulator of liver volume.
Glucocorticoids have pleiotropic effects on small intestinal crypt cells
Authors: Quaroni Andrea , Tian Jean Q. , Göke Michael , Podolsky Daniel K.
Published: December 2017

Glucocorticoids have long been known to accelerate maturation of the intestinal tract, but the molecular mechanisms that account for their physiological function in the epithelium remain poorly characterized. Using rat intestinal epithelial cell lines (IEC-6, IEC-17, and IEC-18) as models, we have characterized glucocorticoid receptors in crypt cells and documented striking morphological, ultrastructural, and functional alterations induced by these hormones in intestinal cells. They include arrest of growth, formation of tight junctions, appearance of long, slender microvilli, reorganization of the endoplasmic reticulum and trans-Golgi network, and downregulation of the cell cycle regulatory proteins cyclin-dependent kinase 6 and p27Kip1. These effects are consistent with the activation or modulation of multiple genes important in the physiological function of absorptive villous cells but are probably not directly involved in the induction of cell differentiation.
V. Knocking out genes to study liver regeneration: present and future
Authors: Fausto Nelson
Published: December 2017

Studies utilizing knockout mice have contributed important new knowledge about the mechanisms that initiate liver regeneration. New mouse lines need to be established to address major questions about these mechanisms, targeting genes for which there is experimental evidence of their involvement in important pathways. Development of conditional, liver-specific knockout mice would be of great value for these studies.
Regulation of G1cyclin-dependent kinases in the liver: role of nuclear localization and p27 sequestration
Authors: Albrecht Jeffrey H. , Rieland Brenda M. , Nelsen Christopher J. , Ahonen Cory L.
Published: December 2017

Recent studies suggest that cyclin D1 mediates progression of hepatocytes through G1phase of the cell cycle. The present study further examines the regulation of cyclin D1-dependent kinase activity and the interplay between cyclin D1 and other G1phase regulatory proteins during liver regeneration. After 70% partial hepatectomy in rats, there was upregulation of kinase activity associated with cyclins (A, D1, D3, and E), cyclin-dependent kinases (Cdk2 and Cdk4), and Cdk-inhibitory proteins (p27, p107, and p130). Although cyclin D1/Cdk4 complexes were more abundant in the cytoplasmic fraction after partial hepatectomy, kinase activity was detected primarily in the nuclear fraction. Cytoplasmic cyclin D1/Cdk4 complexes were activated by recombinant cyclin H/Cdk7. Because endogenous Cdk7 activity was found in the nucleus, this suggests that activation of cyclin D1/Cdk4 requires nuclear importation and subsequent phosphorylation by cyclin H/Cdk7. Recombinant cyclin E/Cdk2 was inhibited by extracts from quiescent liver, and cyclin D1 could titrate out this inhibitory activity. Induction of cyclin D1 was accompanied by increased abundance of cyclin D1/p27 complexes, and most p27 was sequestered by cyclin D1 after partial hepatectomy. Thus cyclin D1 appears to play two roles during G1phase progression in the regenerating liver: it forms a nuclear kinase complex, and it promotes activation of Cdk2 by sequestering inhibitory proteins such as p27. These experiments underscore the complexity of cyclin/Cdk regulatory networks in the regenerating liver.
Lumen-to-surface pH gradients in opossum and rabbit esophagi: role of submucosal glands
Authors: Abdulnour-Nakhoul Solange , Nakhoul Nazih L. , Orlando Roy C.
Published: December 2017

The opossum esophagus, like that of humans, contains a network of submucosal glands with the capacity to secrete bicarbonate ions into the esophageal lumen. To evaluate the role of these glands in protecting the epithelial surface from acid insult, we measured the lumen-to-surface pH gradient in opossum esophagus at different luminal pH and compared it to that of rabbit esophagus, an organ devoid of submucosal glands. Sections of opossum and rabbit esophageal epithelium were mounted luminal side up in a modified Ussing chamber. pH-sensitive microelectrodes, positioned within 5 μm of the epithelial cell surface, were used to monitor surface pH during perfusion with solutions of different pH. At luminal pH 7.5, the pHsof both opossum and rabbit were similar (pHs= 7.5). Lowering luminal pH from 7.5 to 3.5 in opossum decreased pHsto 4.2 ± 0.16, a value significantly higher than pH of perfusate, whereas in rabbit this maneuver decreased pHsto 3.69 ± 0.08, a value not significantly different from pH of perfusate. In opossum but not in rabbit, addition of carbachol to the serosal solution increased basal pHsto 7.8 ± 0.1 and significantly blunted the decline in pHson perfusion with acidic Ringer solution (pH 3.5), with pHsfalling to 5.6 ± 0.45. The effect of carbachol on surface buffering was inhibited by prior treatment with atropine. Luminal acidification to pH 2.0 in opossum (as in rabbit) abolished the lumen-to-surface pH gradient even after addition of serosal carbachol. We conclude that the presence of submucosal glands in esophagus contributes through bicarbonate secretion to creation of a lumen-to-surface pH gradient. Although this gradient can be modulated by carbachol, its capacity to buffer (and therefore to protect) the epithelial surface against back-diffusing H+is limited and dissipated at pH 2.0.
Differential hepatic lobar gene expression in offspring exposed to altered maternal dietary protein intake
Authors: Zhang Junlong , Byrne Christopher D.
Published: December 2017

Increased plasma fibrinogen concentrations are a recognized risk factor for coronary heart disease, and increased fibrinogen levels in adults are associated with parameters of reduced early growth. We studied fibrinogen gene expression in adult offspring of dams fed either a 20% (control) or an 8% protein diet [maternal low-protein (MLP) rats] during pregnancy and lactation and determined whether any effects were consistent between left and right liver lobes, since the fetal liver has a unique blood supply that produces differential stimuli to the left and right lobes. In MLP offspring, there was a reduction in all three fibrinogen mRNA copy numbers in the left liver lobe [left vs. right lobes for α-, β-, and γ-fibrinogen (×106copies/ng total RNA): 8.04 vs. 23.16, P < 0.001; 4.74 vs. 13.07, P< 0.001; and 4.61 vs. 16.38, P = 0.007, respectively], with a parallel reduction in fibrinogen concentration in the left liver lobe (8.53 ± 0.33 vs. 10.41 ± 0.65 arbitrary units, P = 0.014, left and right lobes, respectively). No such effect was observed in offspring of control dams. To investigate the underlying mechanism, glucocorticoid receptor function and mRNA levels were studied, since expression of fibrinogen genes is regulated by glucocorticoid hormones. The binding affinity of the high-affinity glucocorticoid receptor was reduced only in the left liver lobe of the MLP offspring ( P = 0.02, left. vs. right), with a parallel reduction in this lobe in glucocorticoid receptor mRNA level ( P = 0.006, left vs. right). In conclusion, maternal dietary protein restriction reduces fibrinogen gene expression, fibrinogen protein, and mRNA level and binding affinity of glucocorticoid receptors only in the left liver lobe of the adult offspring.
Motilin receptors in the human antrum
Authors: Miller Paul , Roy André , St-Pierre Serge , Dagenais Michel , Lapointe Réal , Poitras Pierre
Published: December 2017

Motilin is an intestinal peptide that stimulates contraction of gut smooth muscle. The motilin receptor has not been cloned yet, but motilin-receptor agonists appear to be potent prokinetic agents for the treatment of dysmotility disorders. The aim of this study was to determine neural or muscular localization of motilin receptors in human upper gastrointestinal tract and to investigate their pharmacological characteristics. The binding of125I-labeled motilin to tissue membranes prepared from human stomach and duodenum was studied; rabbit tissues were used for comparison. Solutions enriched in neural synaptosomes or in smooth muscle plasma membranes were obtained. Various motilin analogs were used to displace the motilin radioligand from the various tissue membranes. The highest concentration of human motilin receptors was found in the antrum, predominantly in the neural preparation. Human motilin receptors were sensitive to the NH2-terminal portion of the motilin molecule, but comparison with rabbit showed that both species had specific affinities for various motilin analogs [i.e., Mot-(1—9), Mot-(1—12), Mot-(1—12) (CH2NH)10–11, and erythromycin]. Motilin receptors obtained from synaptosomes or muscular plasma membranes of human antrum expressed different affinity for two motilin-receptor agonists, Mot-(1—12) and Mot-(1—12) (CH2NH)10–11, suggesting that they correspond to specific receptor subtypes. We conclude that human motilin receptors are located predominantly in nerves of the antral wall, are functionally (and probably structurally) different from those found in other species such as the rabbit, and express specific functional (and probably structural) characteristics dependent on their localization on antral nerves or muscles, suggesting the existence of specific receptor subtypes, potentially of significant physiological or pharmacological relevance.
Putrescine does not support the migration and growth of IEC-6 cells
Authors: Yuan Qing , Viar Mary Jane , Ray Ramesh M. , Johnson Leonard R.
Published: December 2017

The migration of IEC-6 cells is inhibited when the cells are depleted of polyamines by inhibiting ornithine decarboxylase with α-difluoromethylornithine (DFMO). Exogenous putrescine, spermidine, and spermine completely restore cell migration inhibited by DFMO. Because polyamines are interconverted during their synthesis and catabolism, the specific role of individual polyamines in intestinal cell migration, as well as growth, remains unclear. In this study, we used an inhibitor of S-adenosylmethionine decarboxylase, diethylglyoxal bis(guanylhydrazone)(DEGBG), to block the synthesis of spermidine and spermine from putrescine. We found that exogenous putrescine does not restore migration and growth of IEC-6 cells treated with DFMO plus DEGBG, whereas exogenous spermine does. In addition, the normal distribution of actin filaments required for migration, which is disrupted in polyamine-deficient cells, could be achieved by adding spermine but not putrescine along with DFMO and DEGBG. These results indicate that putrescine, by itself, is not essential for migration and growth, but that it is effective because it is converted into spermidine and/or spermine.
IV. There is more to taste than meets the tongue
Authors: Katz Donald B. , Nicolelis Miguel A. L. , Simon S. A.
Published: December 2017

The tongue is the principal organ that provides sensory information about the quality and quantity of chemicals in food. Other information about the temperature and texture of food is also transduced on the tongue, via extragemmal receptors that form branches of the trigeminal, glossopharyngeal, and vagal nerves. These systems, together with information from the gastrointestinal (GI) system, interact to determine whether or not food is palatable. In this themes article, emphasis is placed on the integrative aspects of gustatory processing by showing the convergence of gustatory information with somatosensory, nociceptive, and visceral information (from the GI system) on the tongue and in the brain. Our thesis is that gustation should be thought of as an integral part of a distributed, interacting multimodal system in which information from other systems, including the GI system, can modulate the taste of food.
I. Cellular and molecular biology of sodium channel β-subunits: therapeutic implications for pain?
Authors: Isom Lori L.
Published: December 2017

Voltage-gated sodium channel α-subunits have been shown to be key mediators of the pathophysiology of pain. The present review considers the role of sodium channel auxiliary β-subunits in channel modulation, channel protein expression levels, and interactions with extracellular matrix and cytoskeletal signaling molecules. Although β-subunits have not yet been directly implicated in pain mechanisms, their intimate association with and ability to regulate α-subunits predicts that they may be a viable target for therapeutic intervention in the future. It is proposed that multifunctional sodium channel β-subunits provide a critical link between extracellular and intracellular signaling molecules and thus have the ability to fine tune channel activity and electrical excitability.
Glucagon-like peptide-2 increases sucrase-isomaltase but not caudal-related homeobox protein-2 gene expression
Authors: Kitchen P. A. , Fitzgerald A. J. , Goodlad R. A. , Barley N. F. , Ghatei M. A. , Legon S. , Bloom S. R. , Price A. , Walters J. R. F. , Forbes A.
Published: December 2017

To determine the effect of glucagon-like peptide-2 (GLP-2) on sucrase-isomaltase and caudal-related homeobox protein-2 (Cdx-2) gene expression, male Wistar rats were divided into total parenteral nutrition (TPN)-fed and GLP-2-treated, TPN-fed groups. TPN was given via a jugular line, inserted under anesthesia, for 7 days. The treatment group received 40 μg/day of GLP-2 intravenously with the TPN diet. The small intestine and colon were weighed and measured. Tissue was obtained from the jejunum, terminal ileum, and midcolon. RNA analysis, morphometry, and microdissection were performed. The weight of the small intestine of GLP-2-treated rats was greater than that of TPN-fed rats ( P < 0.001). GLP-2 increased the mean metaphase arrests/crypt in both the jejunum and ileum ( P < 0.001). Ileal expression of sucrase-isomaltase was increased by 1.6-fold ( P < 0.05). Jejunal expression was increased by a similar amount, although not significantly ( P = 0.08). There was no change in Cdx-2 gene expression. Thus GLP-2 can maintain small intestinal morphology and function, but effects on gene expression are not mediated by gross changes in the level of the mRNA for the homeobox protein Cdx-2.
Physiological roles of endogenous nitric oxide in lymphatic pump activity of rat mesentery in vivo
Authors: Shirasawa Yuichi , Ikomi Fumitaka , Ohhashi Toshio
Published: December 2017

Physiological roles of endogenous nitric oxide (NO) in the lymphatic pump activity of rat mesenteries in vivo were evaluated using an intravital video microscope system. Changes in the pumping frequency ( F), the end diastolic diameter (EDD), and the end systolic diameter (ESD) of the mesenteric lymph microvessels were measured with the microscope system and then the pump flow index (PFI) was calculated. A 15-min superfusion of 30 μM N ω-nitro-l-arginine methyl ester (l-NAME) in the mesenteries caused significant increases of F and PFI and a significant decrease of the EDD and ESD. Simultaneous superfusion of 1 mM l-arginine with 30 μMl-NAME produced a significant reversal of thel-NAME-mediated increase of F and decrease of ESD. A 15-min superfusion of 100 μM aminoguanidine caused no significant effects on F, EDD, and ESD of the mesenteric lymph vessels in vivo. These findings suggest that endogenous NO has physiologically modulated the lymphatic pump activity in rat mesentery in vivo and that the production and release of NO may be mediated by constitutive NO synthase but not by inducible NO synthase.
Differential jejunal and colonic adaptation due to resection and IGF-I in parenterally fed rats
Authors: Gillingham Melanie B. , Dahly Elizabeth M. , Carey Hannah V. , Clark Melanee D. , Kritsch Karen R. , Ney Denise M.
Published: December 2017

Patients with severe short-bowel syndrome (SBS) often require long-term total parenteral nutrition (TPN) to maintain their nutritional status because of limited intestinal adaptation. Growth factors, including insulin-like growth factor I (IGF-I), are under investigation to promote intestinal adaptation and tolerance to oral feeding. We investigated structural and functional adaptation of the jejunum and colon in four groups of rats maintained with TPN for 7 days after a 60% jejunoileal resection and cecectomy or sham surgery and treatment with IGF-I or vehicle. Resection alone did not stimulate jejunal growth. IGF-I significantly increased jejunal mucosal mass, enterocyte proliferation, and migration rates. IGF-I decreased jejunal sucrase specific activity and reduced active ion transport and ionic permeability; resection alone had no effect. In contrast, resection significantly increased colonic mass and crypt depth but had no effect on active ion transport or ionic permeability. IGF-I had minimal effects on colonic structure. IGF-I but not resection stimulates jejunal adaptation, whereas resection but not IGF-I stimulates colonic growth in rats subjected to a model for human SBS. IGF-I treatment may improve intestinal adaptation in humans with SBS.
Resistance to apoptosis is a mechanism of adaptation of rat stomach to aspirin
Authors: Alderman Barbara M. , Cook Gregory A. , Familari Mary , Yeomans Neville D. , Giraud Andrew S.
Published: December 2017

Adaptation of the gastric mucosa to nonsteroidal anti-inflammatory drug-induced injury is a well-documented phenomenon, but the mechanisms are not known. We investigated whether changes in stress protein expression and apoptosis play roles in adaptation of rat stomach to aspirin. RT-PCR and Western blotting techniques were used to analyze mRNA and protein expression of HSP72 and HSP90 and cleavage of caspase 3 protein. Apoptosis was detected by the TUNEL method and quantified. HSP72 mRNA and protein expression was unchanged in adapted mucosa, whereas HSP90 mRNA and protein levels decreased. Caspase 3 protein was activated, and the number of apoptotic cells increased in mucosa after one aspirin dose. However, in adapted mucosa after aspirin, activated caspase 3 and the number of apoptotic cells had returned to basal levels. Induction of the stress response was found not to be a mechanism of mucosal adaptation against multiple doses of aspirin. Our results lead us to propose instead that resistance to aspirin-induced apoptosis plays a role in the protective phenomenon of adaptation.
Luminal ammonia retards restitution of guinea pig injured gastric mucosa in vitro
Authors: Suzuki Hideo , Yanaka Akinori , Muto Hiroshi
Published: December 2017

The present study was conducted to elucidate the mechanisms by which Helicobacter pylori (HP)-derived ammonia causes gastric mucosal injury. Intact sheets of guinea pig gastric fundic mucosae were incubated in Ussing chambers. Both the luminal and the serosal pH were kept at 7.4. Transmucosal potential difference (PD) and electrical resistance ( R) were monitored as indices of mucosal integrity. Restitution was evaluated by recovery of PD, R, and transmucosal [3H]mannitol flux after Triton X-100-induced mucosal injury. The effects of luminal or serosal NH4Cl on function and morphology of uninjured or injured mucosae were examined. In uninjured mucosae, serosal NH4Cl induced more profound decreases in PD and R and more prominent vacuolation in gastric epithelial cells than did luminal NH4Cl. In contrast, luminal NH4Cl markedly inhibited restitution in injured mucosae and caused an extensive vacuolation in gastric epithelial cells, as did serosal NH4Cl. Transmucosal ammonia flux was greater in the injured than in the uninjured mucosae. These results suggest that 1) basolateral membrane of gastric epithelial cells is more permeable to ammonia than apical membrane and 2) luminal ammonia, at concentrations detected in HP-infected gastric lumen, retards restitution in injured mucosae.
Triggering of transient LES relaxations in ferrets: role of sympathetic pathways and effects of baclofen
Authors: Staunton Esther , Smid Scott D. , Dent John , Blackshaw L. Ashley
Published: December 2017

Activation of gastric vagal mechanoreceptors by distention is thought to be the trigger for transient lower esophageal sphincter relaxations (TLESR), which lead to gastroesophageal reflux. The contribution of higher-threshold gastric splanchnic mechanoreceptors is uninvestigated. GABABreceptor agonists, including baclofen, potently reduce triggering of TLESR by low-level gastric distention. We aimed to determine first whether this effect of baclofen is maintained at high-level distention and second the role of splanchnic pathways in triggering TLESR. Micromanometric/pH studies in conscious ferrets showed that intragastric glucose infusion (25 ml) increased triggering of TLESR and reflux. Both were significantly reduced by baclofen (7 μmol/kg ip) ( P < 0.05). When 40 ml of air was added to the glucose infusion, more TLESR occurred than with glucose alone ( P < 0.01). These were also reduced by baclofen ( P < 0.001). TLESR after glucose/air infusion were assessed before and after splanchnectomy (2–4, 9–11, and 23–25 days), which revealed no change. Baclofen inhibits TLESR after both low- and high-level gastric distention. Splanchnic pathways do not contribute to increased triggering of TLESR by high-level gastric distention.
CGRP modulates mucin synthesis in surface mucus cells of rat gastric oxyntic mucosa
Authors: Ichikawa Takafumi , Ishihara Kazuhiko , Kusakabe Tatsumi , Hiruma Hiromi , Kawakami Tadashi , Hotta Kyoko
Published: December 2017

We examined the effects of the calcitonin gene-related peptide (CGRP), including the possible participation of nitric oxide (NO), on mucin biosynthesis in the surface epithelium and remaining deep mucosa as well as the entire mucosa and compared the distribution of CGRP and NO synthase (NOS) using a combination of double immunofluorescence labeling and multiple dye filter. Pieces of tissue obtained from the corpus and antrum were incubated in a medium containing [3H]glucosamine and CGRP, with or without the NOS inhibitor. CGRP dose-dependently enhanced [3H]glucosamine incorporation into the corpus mucin but had no effect on antral mucin biosynthesis. The CGRP receptor antagonist, CGRP-(8–37), prevented the increase in3H-labeled corpus mucin. This stimulation of corpus mucin synthesis disappeared after removal of the surface mucus cell layer. CGRP activated the mucin biosynthesis in the surface mucus cells. In the full-thickness corpus mucosa, CGRP-induced activation was completely blocked by the NOS inhibitor. CGRP-immunoreactive fibers were intertwined within the surface mucus cell layer with type I NOS immunoreactivity. These results show that CGRP-stimulated mucin biosynthesis mediated by NO is limited to surface mucus cells of the rat gastric oxyntic mucosa.
Neural regulation of intestinal smooth muscle growth in vitro
Authors: Blennerhassett M. G. , Lourenssen S.
Published: December 2017

The loss of intrinsic neurons is an early event in inflammation of the rat intestine that precedes the growth of intestinal smooth muscle cells (ISMC). To study this relationship, we cocultured ISMC and myenteric plexus neurons from the rat small intestine and examined the effect of scorpion venom, a selective neurotoxin, on ISMC growth. By 5 days after neuronal ablation, ISMC number increased to 141 ± 13% ( n = 6) and the uptake of [3H]thymidine in response to mitogenic stimulation was nearly doubled. Atropine caused a dose-dependent increase in [3H]thymidine uptake in cocultures, suggesting the involvement of neural stimulation of cholinergic receptors in regulation of ISMC growth. In contrast, coculture of ISMC with sympathetic neurons increased [3H]thymidine uptake by 45–80%, which was sensitive to propranolol (30 μM) and was lost when the neurons were separated from ISMC by a permeable filter. Western blotting showed that coculture with myenteric neurons increased α-smooth muscle-specific actin nearly threefold to a level close to ISMC in vivo. Therefore, factors derived from enteric neurons maintain the phenotype of ISMC through suppression of the growth response, whereas catecholamines released by neurons extrinsic to the intestine may stimulate their growth. Thus inflammation-induced damage to intestinal innervation may initiate or modulate ISMC hyperplasia.
Novel nuclear corticosteroid binding in rat small intestinal epithelia
Authors: Sheppard Karen E. , Hourigan Susanne , Li Kevin X. Z. , Krozowski Zygmunt S.
Published: December 2017

When small intestinal epithelial cells are incubated with [3H]corticosterone, nuclear binding is displaced neither by aldosterone nor RU-28362, suggesting that [3H]corticosterone is binding to a site distinct from mineralocorticoid receptor and glucocorticoid receptor. Saturation and Scatchard analysis of nuclear [3H]corticosterone binding demonstrate a single saturable binding site with a relatively low affinity (49 nM) and high capacity (5 fmol/μg DNA). Competitive binding assays indicate that this site has a unique steroid binding specificity, which distinguishes it from other steroid receptors. Steroid specificity of nuclear binding mirrors inhibition of the low 11β-dehydrogenase activity, suggesting that binding may be to an 11β-hydroxysteroid dehydrogenase (11βHSD) isoform, although 11βHSD1 is not present in small intestinal epithelia and 11βHSD2 does not colocalize intracellularly with the binding site. In summary, a nuclear [3H]corticosterone binding site is present in small intestinal epithelia that is distinct from other steroid receptors and shares steroid specificity characteristics with 11βHSD2 but is distinguishable from the latter by its distinct intracellular localization.
Demonstration of a pH gradient in the gastric gland of the acid-secreting guinea pig mucosa
Authors: Schreiber Sören , Nguyen Thanh Hoa , Stüben Manuela , Scheid Peter
Published: December 2017

The gastric mucosa is covered by a continuous layer of mucus. Although important for understanding the mechanism of this protective function, only scarce information exists about the pH inside the gastric gland and its outlet. pH in the lumen of the gastric glands, in the outlet of gastric crypts, and in the adjacent cells was measured in the isolated acid-secreting mucosa of the guinea pig. Ultrafine double-barreled pH microelectrodes were advanced at high acceleration rates through the gastric mucus and the tissue to ensure precise intracellular and gland lumen pH measurements. A pH gradient was found to exist along the gastric gland, where the pH is 3.0 at parietal cells, i.e., in the deepest regions, and increases to 4.6 at the crypt outlet. Intracellular pH (pHi) of epithelial cells bordering a crypt outlet, and of neck cells bordering a gland, was acidic, averaging 6.0 and 6.5, respectively. pHi of deep cells bordering a gland was nearly neutral, averaging 7.1, and the secreting parietal cells were characterized by a slightly alkaline pHi of 7.5. This gland pH gradient is in general agreement with a model that we recently proposed for proton transport in the gastric mucus, in which protons secreted by the parietal cells are buffered to and transported with the simultaneously secreted mucus toward the gastric lumen, where they are liberated from the degraded mucus.
Cubilin expression and posttranslational modification in the canine gastrointestinal tract
Authors: Xu Danbin , Fyfe John C.
Published: December 2017

Cubilin is an endocytic receptor of the apical brush border membrane that is essential for intrinsic factor-mediated cobalamin absorption in small intestine. However, cubilin is more highly expressed in kidney and yolk sac, and recent molecular characterization of the receptor has focused on these tissues. The aim of this investigation was to examine tissue-specific cubilin expression and posttranslational modifications with an emphasis on the gastrointestinal tract. Intrinsic factor-cobalamin binding activity, cubilin immunoreactivity, and cubilin mRNA levels were determined in multiple segments of canine gastrointestinal mucosa and other tissues. These aspects of cubilin expression varied in parallel, suggesting that the major determinant of regional cubilin expression in the gastrointestinal tract is modulation of cubilin mRNA. Cell fractionation indicated that ileal cubilin is not strongly membrane associated. An ∼185-kDa brush border specific and two >400-kDa precursor forms of cubilin were identified. Asparagine-linked oligosaccharide modifications characterized by differential glycosidase digestion of affinity-purified cubilin from ileal mucosa and renal cortex differed, but ileal and renal intracellular cubilin comigrated on SDS-PAGE at ∼400 kDa after oligosaccharide removal, thus reconciling previous conflicting size estimates of the cubilin polypeptide.
Differential Ca2+ signaling characteristics of inhibitory and excitatory myenteric motor neurons in culture
Authors: Vanden Berghe Pieter , Molhoek Sander , Missiaen Ludwig , Tack Jan , Janssens Jozef
Published: December 2017

Physiological studies on functionally identified myenteric neurons are scarce because of technical limitations. We combined retrograde labeling, cell culturing, and fluorescent intracellular Ca2+ concentration ([Ca2+]i) signaling to study excitatory neurotransmitter responsiveness of myenteric motor neurons. 1,1-Didodecyl-3,3,3′,3′-tetramethyl indocarbocyanine (DiI) was used to label circular muscle motor neurons of the guinea pig ileum. DiI-labeled neurons were easily detectable in cultures prepared from these segments. The excitatory neurotransmitters (10−5 M) acetylcholine, substance P, and serotonin induced a transient rise in [Ca2+]i in subsets of DiI-labeled neurons (66.7, 56.5, and 84.3%, respectively). DiI-labeled motor neurons were either inhibitory (23.8%) or excitatory (76.2%) as assessed by staining for nitric oxide synthase or choline acetyltransferase. Compared with excitatory motor neurons, significantly fewer inhibitory neurons in culture responded to acetylcholine (0 vs. 69%) and substance P (12.5 vs. 69.2%). We conclude that combining retrograde labeling and Ca2+ imaging allows identification of differential receptor expression in functionally identified neurons in culture.
Investigation of gastroprotective compounds at subcellular level in isolated gastric mucosal cells
Authors: Nagy Lajos , Morales Romeo E. , Beinborn Martin , Vattay Peter , Szabo Sandor
Published: December 2017

We tested the hypothesis that recognized gastroprotective agents exert direct protection against ethanol-induced injury in isolated rat gastric mucosal cells in vitro. If protection exists, we also wanted to identify subcellular targets in the reversible and/or irreversible stages of cell injury. Ethanol-induced cell injury was quantified by measuring plasma membrane leakage (trypan blue exclusion and lactate dehydrogenase release), mitochondrial integrity (succinic dehydrogenase), and nuclear damage (ethidium bromide-DNA fluorescence). Initial cell viability and responsiveness were estimated by the effects of carbachol, carbachol + atropine, or 16,16-dimethyl-PGE2on chief cell pepsinogen secretion. Enriched parietal cells were stimulated by histamine, carbachol, or histamine + IBMX. Preincubation of cells with PG, sucrose octasulfate, or the sulfhydryl compounds N-acetylcysteine, taurine, or cysteamine increased cell resistance ≤21% against ethanol. Similar protection was found with low histamine concentrations, but a higher concentration aggravated ethanol toxicity. Other naturally occurring or synthetic gastroprotective agents offered partial protection or aggravated ethanol-induced cell injury. Only a few in vivo gastroprotective agents demonstrated in vitro direct cytoprotection, which involved mainly the reversible stage of cell injury (e.g., plasma membrane changes) and, less often, irreversible (e.g., mitochondrial and nuclear) damage. Our findings also indicate that a major part of the beneficial effect of gastroprotective agents is expressed at the tissue level.
Different actions of secretin and Gly-extended secretin predict secretin receptor subtypes
Authors: Solomon Travis E. , Varga Gabor , Zeng Ning , Wu S. Vincent , Walsh John H. , Reeve Joseph R.
Published: December 2017

Only one secretin receptor has been cloned and its properties characterized in native and transfected cells. To test the hypothesis that stimulatory and inhibitory effects of secretin are mediated by different secretin receptor subtypes, pancreatic and gastric secretory responses to secretin and secretin-Gly were determined in rats. Pancreatic fluid secretion was increased equipotently by secretin and secretin-Gly, but secretin was markedly more potent for inhibition of basal and gastrin-induced acid secretion. In Chinese hamster ovary cells stably transfected with the rat secretin receptor, secretin and secretin-Gly equipotently displaced125I-labeled secretin (IC50 values 5.3 ± 0.5 and 6.4 ± 0.6 nM, respectively). Secretin, but not secretin-Gly, caused release of somatostatin from rat gastric mucosal D cells. Thus the equipotent actions of secretin and secretin-Gly on pancreatic secretion appear to result from equal binding and activation of the pancreatic secretin receptor. Conversely, secretin more potently inhibited gastric acid secretion in vivo, and only secretin released somatostatin from D cells in vitro. These results support the existence of a secretin receptor subtype mediating inhibition of gastric acid secretion that is distinct from the previously characterized pancreatic secretin receptor.
Insulin signal transduction in rat small intestine: role of MAP kinases in expression of mucosal hydrolases
Authors: Marandi Soheila , De Keyser Nadine , Saliez Alain , Maernoudt Anne-Sophie , Sokal Etienne Marc , Stilmant Catherine , Rider Mark H. , Buts Jean-Paul
Published: December 2017

The postreceptor events regulating the signal of insulin downstream in rat intestinal cells have not yet been analyzed. Our objectives were to identify the nature of receptor substrates and phosphorylated proteins involved in the signaling of insulin and to investigate the mechanism(s) by which insulin enhances intestinal hydrolases. In response to insulin, the following proteins were rapidly phosphorylated on tyrosine residues: 1) insulin receptor substrates-1 (IRS-1), -2, and -4; 2) phospholipase C-isoenzyme-γ; 3) the Ras-GTPase-activating protein (GAP) associated with Rho GAP and p62Src; 4) the insulin receptor β-subunit; 5) the p85 subunits of phosphatidylinositol 3-kinase (PI 3-kinase); 6) the Src homology 2 α-collagen protein; 7) protein kinase B; 8) mitogen-activated protein (MAP) kinase-1 and -2; and 9) growth receptor-bound protein-2. Compared with controls, insulin enhanced the intestinal activity of MAP kinase-2 and protein kinase B by two- and fivefold, respectively, but did not enhance p70/S6 ribosomal kinase. Administration of an antireceptor antibody or MAP-kinase inhibitor PD-98059 but not a PI 3-kinase inhibitor (wortmannin) to sucklings inhibited the effects of insulin on mucosal mass and enzyme expression. We conclude that normal rat enterocytes express all of the receptor substrates and mediators involved in different insulin signaling pathways and that receptor binding initiates a signal enhancing brush-border membrane hydrolase, which appears to be regulated by the cascade of MAP kinases but not by PI 3-kinase.
Gender influence on jejunal migrating motor complex
Authors: Aytuğ Neci˙p , Gi˙ral Adnan , I˙meryüz Neşe , Enç Feruze Y. , Beki˙roğlu Nural , Aktaş Güler , Ulusoy Nefi˙se B.
Published: December 2017

The role of gender and the menstrual cycle in small bowel motility has not been clearly elucidated. Jejunal motility was recorded with a nasojejunal catheter incorporating five solid-state pressure transducers in ambulatory menstruating women and men of comparable age over 24 h. All women were studied twice, in the early follicular (early-F) and midluteal (mid-L) phases of the menstrual cycle, verified by determining serum levels of gonadal steroids and gonadotropins. The propagation velocity of phase III was slow and the contraction amplitude was high in both menstrual cycle phases compared with men, and these parameters were correlated with serum estrogen levels in the mid-L phase. In the early-F phase, migrating motor complex (MMC) cycle duration during sleep was long compared with other groups and positively correlated with estrogen concentrations, whereas in the mid-L phase MMC cycle duration during sleep was negatively correlated with serum progesterone levels. In all groups, the frequency of phase III contractions was low and the intercontractile interval measured from pressure peak to peak was long during sleep compared with the awake state. Postprandial motility did not display gender difference in any parameter examined. The results demonstrate that the majority of patterns of motility are similar in menstruating women and men, whereas certain aspects of the MMC, most conspicuously propagation velocity and phase III contraction amplitude, differ. We have also documented circadian variation of phase III contraction frequency in both women and men.
Kupffer cell-initiated remote hepatic injury following bilateral hindlimb ischemia is complement dependent
Authors: Brock Robert W. , Nie Robert G. , Harris Kenneth A. , Potter Richard F.
Published: December 2017

Intravital fluorescence microscopy was applied to the livers of male Wistar rats to test the hypothesis that complement mobilization stimulates Kupffer cells and subsequently initiates hepatic injury after hindlimb ischemia/reperfusion (I/R). Following 3 h of limb reperfusion, hepatocellular viability (serum levels of alanine transaminase and cell death via propidium iodide labeling) decreased significantly from levels in sham-operated animals. Inhibition of complement mobilization with soluble complement receptor type 1 (20 mg/kg body wt) and interruption of Kupffer cell function with GdCl3(1 mg/100g body wt) resulted in significant hepatocellular protection. Although the effects of hindlimb I/R on hepatic microvascular perfusion were manifest as increased heterogeneity, both complement inhibition and suppression of Kupffer cell function resulted in marked improvements. No additional hepatocellular protection and microvascular improvements were provided by combining the interventions. Furthermore, inhibition of complement mobilization significantly depressed Kupffer cell phagocytosis by 42% following limb reperfusion. These results suggest that the stimulation of Kupffer cells via complement mobilization is necessary but is not the only factor contributing to the early pathogenesis of hepatic injury following hindlimb I/R.
Characterization of apical membrane Cl-dependent Na/H exchange in crypt cells of rat distal colon
Authors: Rajendran Vazhaikkurichi M. , Geibel John , Binder Henry J.
Published: December 2017

A novel Cl-dependent Na/H exchange (Cl-NHE) has been identified in apical membranes of crypt cells of rat distal colon. The presence of Cl is required for both outward proton gradient-driven Na uptake in apical membrane vesicles (AMV) and Na-dependent intracellular pH recovery from an acid load in the crypt gland. The present study establishes that Cl-dependent outward proton gradient-driven22Na uptake 1) is saturated with increasing extravesicular Na concentration with a Michaelis constant ( Km) for Na of ∼24.2 mM; 2) is saturated with increasing outward H concentration gradient with a hyperbolic curve and a Kmfor H of ∼1.5 μM; 3) is inhibited by the Na/H exchange (NHE) inhibitors amiloride, ethylisopropylamiloride, and HOE-694 with an inhibitory constant ( Ki) of ∼480.2, 1.1, and 9.5 μM, respectively; 4) is inhibited by 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid, an anion exchange inhibitor at low concentration and a Cl channel blocker at high dose, and by 5-nitro-2(3-phenylpropylamino)benzoic acid, a Cl channel blocker, with a Kiof ∼280.6 and 18.3 μM, respectively; and 5) substantially stimulated Cl-NHE activity by dietary Na depletion, which increases plasma aldosterone and inhibits NHE in surface cell AMV. These properties of Cl-NHE are distinct from those of NHE1, NHE2, and NHE3 isoforms that are present in colonic epithelial cells; thus these results suggest that the colonic crypt cell Cl-NHE is a novel NHE isoform.
The role of protein kinase C isozymes in TNF-α-induced cytotoxicity to a rat intestinal epithelial cell line
Authors: Chang Q. , Tepperman B. L.
Published: December 2017

Tumor necrosis factor (TNF)-α can induce cytotoxicity and apoptosis in a number of cell types and has been implicated in the regulation of many inflammatory processes. It has been suggested that protein kinase C (PKC) is one of the intracellular mediators of the actions of TNF-α. In the present study, the role of PKC isoforms in TNF-α-mediated cytotoxicity and apoptosis in intestinal cells was investigated using the rat epithelial cell line, IEC-18. Cells were incubated with TNF-α in the presence or absence of the transcription inhibitor actinomycin D (AMD). The extent of cell damage was enhanced when AMD was added to incubation medium, suggesting that new protein synthesis plays a role in the cytotoxic action of TNF. TNF-α also induced the translocation of PKC-α, -δ, and -ε from cytosol to the membrane fraction of the intestinal cells. Furthermore, the cytotoxic and apoptotic effects of TNF were reduced by pretreating the cells with the PKC-ε translocation inhibitor, PKC-εV1–2. In contrast, although cells incubated with the phorbol ester phorbol 12-myristate 13-acetate (PMA) also displayed an increase in cell injury, the extent of cytotoxicity and apoptosis was not enhanced by AMD. Furthermore, PMA-induced cell damage was reduced by rottlerin, a PKC-δ inhibitor. Caspase-3, an enzyme implicated in the mediation of apoptosis, was activated in cells in response to either TNF-α or PMA stimulation, and its effects on this activity were reduced by selective inhibition of PKC-ε and -δ, respectively. Furthermore, inhibition of caspase-3 activity reduced apoptosis. These data suggest that activation of selective PKC isoforms mediate the effects of TNF-α on intestinal epithelial cell injury.
Arterial compliance in patients with cirrhosis: stroke volume-pulse pressure ratio as simplified index
Authors: Henriksen Jens H. , Fuglsang Stefan , Bendtsen Flemming , Christensen Erik , Møller Søren
Published: December 2017

Arterial function may be altered in patients with cirrhosis. We determined compliance of the arterial tree (C1) in relation to systemic and splanchnic hemodynamic derangement and clinical variables. C1 and the stroke volume-pulse pressure index (SV/PP) were significantly higher (+62% and +40%, respectively; P < 0.001) in cirrhotic patients ( n = 49) than in control subjects ( n = 19), and a close correlation between C1 and SV/PP was found in both cirrhotic patients ( r = 0.86, P < 0.001) and control subjects ( r = 0.96, P < 0.001). Univariate analysis showed significant relations between C1and SV/PP on one side and age, sex, body weight, portal pressure, systemic hemodynamics, biochemical variables, and severity of disease on the other. In the multiple-regression analysis, sex, age, mean arterial blood pressure, systemic vascular resistance, and biochemical variables were significant independent predictors of SV/PP ( P < 0.005–0.00001). In conclusion, arterial compliance is elevated in cirrhosis. A simplified SV/PP index seems to reflect abnormalities in the arterial compliance of these patients.