bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of growth and apoptosis of cultured guinea pig gastric mucosal cells by mitogenic oxidase 1
Authors: Teshima Shigetada , Kutsumi Hiromu , Kawahara Tsukasa , Kishi Kyoichi , Rokutan Kazuhito
Published: December 2017

We previously reported that primary cultures of guinea pig gastric pit cells expressed all of the phagocyte NADPH oxidase components (gp91-, p22-, p67-, p47-, and p40- phox) and could spontaneously release superoxide anion (O2−). We demonstrate here that pit cells express a nonphagocyte-specific gp91- phox homolog (Mox1) but not gp91- phox. Inclusion of catalase significantly inhibited [3H]thymidine uptake during the initial 2 days of culture. Pit cells, matured on day 2, slowly underwent spontaneous apoptosis. Scavenging O2−and related oxidants by superoxide dismutase plus catalase or N-acetyl cysteine (NAC) and inhibiting Mox1 oxidase by diphenylene iodonium activated caspase 3-like proteases and markedly enhanced chromatin condensation and DNA fragmentation. This accelerated apoptosis was completely blocked by a caspase inhibitor, z-Val-Ala-Asp-CH2F. Mox1-derived reactive oxygen intermediates constitutively activated nuclear factor-κB, and inhibition of this activity by nuclear factor-κB decoy oligodeoxynucleotide accelerated their spontaneous apoptosis. These results suggest that O2−produced by the pit cell Mox1 oxidase may play a crucial role in the regulation of their spontaneous apoptosis as well as cell proliferation.
NK-1 antagonist reduces colonic inflammation and oxidative stress in dextran sulfate-induced colitis in rats
Authors: Stucchi Arthur F. , Shofer Scott , Leeman Susan , Materne Olivier , Beer Eve , McClung James , Shebani Khaled , Moore Finola , O'Brien Michael , Becker James M.
Published: December 2017

Although substance P (SP) has been implicated as a mediator of neurogenic inflammation in the small intestine, little information is available regarding the role of SP in the pathogenesis of chronic ulcerative colitis. In this study, our aim was to investigate whether the intraperitoneal administration of a nonpeptide neurokinin-1 (NK-1) antagonist, CP-96345, which antagonizes the binding of SP to its NK-1 receptor, results in the attenuation of colonic inflammation induced in rats by 5% dextran sodium sulfate (DSS) in drinking water for 10 days compared with an inactive enantiomer, CP-96344. Disease activity was assessed daily for 10 days, after which colonic tissue damage was scored and myeloperoxidase activity and colon and urinary 8-isoprostanes were measured. Animals receiving DSS exhibited marked physical signs of colitis by day 5 compared with controls. Chronic administration of the NK-1 antagonist significantly reduced the disease activity index, mucosal myeloperoxidase activity, colonic tissue damage score, and mucosal and urinary levels of 8-isoprostanes compared with inactive enantiomer- or vehicle-injected (saline) animals receiving DSS alone. These data indicate that the administration of an NK-1 antagonist can attenuate colonic inflammation and oxidative stress and suggest a novel therapeutic approach in the treatment of chronic ulcerative colitis.
Developmental reprogramming of rat GLUT-5 requires de novo mRNA and protein synthesis
Authors: Jiang Lan , Ferraris Ronaldo P.
Published: December 2017

Fructose transporter (GLUT-5) expression is low in mid-weaning rat small intestine, increases normally after weaning is completed, and can be precociously induced by premature consumption of a high-fructose (HF) diet. In this study, an in vivo perfusion model was used to determine the mechanisms regulating this substrate-induced reprogramming of GLUT-5 development. HF (100 mM) but not high-glucose (HG) perfusion increased GLUT-5 activity and mRNA abundance. In contrast, HF and HG perfusion had no effect on Na+-dependent glucose transporter (SGLT-1) expression but increased c- fos and c- jun expression. Intraperitoneal injection of actinomycin D before intestinal perfusion blocked the HF-induced increase in fructose uptake rate and GLUT-5 mRNA abundance. Actinomycin D also prevented the perfusion-induced increase in c- fos and c- jun mRNA abundance but did not affect glucose uptake rate and SGLT-1 mRNA abundance. Cycloheximide blocked the HF-induced increase in fructose uptake rate but not the increase in GLUT-5 mRNA abundance and had no effect on glucose uptake rate and SGLT-1 mRNA abundance. In neonatal rats, the substrate-induced reprogramming of intestinal fructose transport is likely to involve transcription and translation of the GLUT-5 gene.
Systemic and portal hemodynamic effects of anandamide
Authors: Garcia Nelson , Járai Zoltán , Mirshahi Faridoddin , Kunos George , Sanyal Arun J.
Published: December 2017

The endogenous cannabinoid anandamide causes hypotension and mesenteric arteriolar dilation. A detailed analysis of its effects on systemic and portal venous hemodynamics had not yet been performed. We assessed the effects of anandamide (0.4–10 mg/kg) on systemic and portal hemodynamics with and without prior treatment with various antagonists. The specific antagonists used included SR-141716A, N ω-nitro-l-arginine methyl ester, indomethacin, and nordihydroguaiaretic acid. Anandamide produced a dose-dependent decrease in mean arterial pressure due to a drop in systemic vascular resistance (SVR) that was accompanied by a compensatory rise in cardiac output. Anandamide also elicited an increase in both portal venous flow and pressure, along with a decline in mesenteric vascular resistance (MVR). Pretreatment with 3 mg/kg SR-141716A, a CB1 antagonist, prevented the decline of SVR and MVR from the lower dose of anandamide. Antagonism of nitric oxide synthetase, cyclooxygenase, or 5-lipoxygenase did not prevent the systemic nor the portal hemodynamic effects of anandamide. Furthermore, the use of R-methanandamide, a stable analog of anandamide, produced similar hemodynamic effects on the mesenteric vasculature, thereby implying that the effects of anandamide are not related to its breakdown products. Anandamide produced profound, dose-dependent alterations in both the systemic and portal circulations that could be at least partially blocked by pretreatment with SR-141716A.
Inducible and neuronal nitric oxide synthase involvement in lipopolysaccharide-induced sphincteric dysfunction
Authors: Fan Ya-Ping , Chakder Sushanta , Gao Feng , Rattan Satish
Published: December 2017

We examined the effect of endotoxin lipopolysaccharide (LPS) on the basal tone and on the effects of different stimuli and agonists and transcriptional and translational expression of nitric oxide (NO) synthase (NOS) isozymes in the lower esophageal sphincter (LES), pyloric sphincter (PS), and internal anal sphincter (IAS). NO release was also examined before and after LPS. LPS caused a dose-dependent fall in the basal tone and augmentation of the relaxation caused by nonadrenergic, noncholinergic (NANC) nerve stimulation in the LES and IAS. In the PS, LPS had no significant effect on the basal tone and caused an attenuation of the NANC relaxation and an augmentation of the contractile response of muscarinic agonist. Interestingly, the smooth muscle relaxation by atrial natriuretic factor was suppressed in the LES and IAS but not in the PS. These changes in the sphincteric function following LPS may be associated with increase in the inducible NOS (iNOS) expression since they were blocked by iNOS inhibitorl-canavanine. Augmentation of NANC relaxation in the LES and IAS smooth muscle by LPS may be due to the increased activity of neuronal NOS and NO production.
GATA family transcription factors activate lactase gene promoter in intestinal Caco-2 cells
Authors: Fang Rixun , Olds Lynne C. , Santiago Nilda A. , Sibley Eric
Published: December 2017

The GATA family of transcription factors regulate tissue-specific patterns of gene expression during development. We have characterized the interaction between GATA proteins and the lactase gene promoter. Nuclear protein bound to the lactase gene GATA region cis element (−97 to −73) was analyzed by electrophoretic mobility shift assays (EMSA) and supershift assays with GATA antibodies. Lactase promoter activities were assayed in Caco-2 cells transfected with wild-type and mutated luciferase promoter-reporter constructs and GATA-4/5/6 expression constructs. EMSA with the GATA region probe yields a specific DNA-protein complex that requires the GATA factor binding site WGATAR. The complex is recognized by GATA-4- and GATA-6-specific antibodies. GATA-4/5/6 expression constructs are able to activate transcription driven by the wild-type promoter, but not by a promoter in which the GATA binding site is mutated, in Caco-2 and nonintestinal QT6 cells. GATA factor binding to the lactase cis element correlates with functional promoter activation. We conclude that each of the GATA family zinc finger proteins expressed in the intestine, GATA-4, -5, and -6, can interact with the lactase promoter GATA element and can function to activate the promoter in Caco-2 cells.
Diurnal rhythmicity in intestinal SGLT-1 function,Vmax, and mRNA expression topography
Authors: Tavakkolizadeh Ali , Berger Urs V. , Shen K. Robert , Levitsky Lynne L. , Zinner Michael J. , Hediger Matthias A. , Ashley Stanley W. , Whang Edward E. , Rhoads David B.
Published: December 2017

Mechanisms underlying the circadian rhythmicity in intestinal sugar absorption remain unclear. To test whether this rhythmicity is caused by changes in Na+-glucose cotransporter 1 (SGLT-1) function, we measured phloridzin-inhibitable sugar fluxes as an index of SGLT-1 activity. Jejunum obtained from rats killed at 6-h intervals during a 12-h light-dark cycle (CT0 is circadian time 0 h, time of light onset) were mounted in Ussing chambers, and 3- O-methylglucose (3-OMG) fluxes were calculated before and after addition of phloridzin. 3-OMG-induced change in short-circuit current and absorptive flux were significantly greater at CT9 than at CT3. This increase was phloridzin inhibitable. Kinetic studies indicated a significant increase in SGLT-1 maximal velocity ( Vmax) at CT9. Food intake between CT3 and CT9 was <10% of the daily total, indicating that the increased SGLT-1 activity was anticipatory. Diurnicity of SGLT-1 mRNA was confirmed by Northern blotting. Expression topography analyzed by in situ hybridization revealed more intense labeling along the entire villus axis at CT9 and CT15 compared with CT3 and CT21. We conclude that diurnicity in intestinal sugar absorption is caused by periodicity in SGLT-1 Vmax.
Effect ofE. coliheat-stable enterotoxin on colonic transport in guanylyl cyclase C receptor-deficient mice
Authors: Charney Alan N. , Egnor Richard W. , Alexander-Chacko Jesline T. , Zaharia Valentin , Mann Elizabeth A. , Giannella Ralph A.
Published: December 2017

We studied the functional importance of the colonic guanylyl cyclase C (GCC) receptor in GCC receptor-deficient mice. Mice were anesthetized with pentobarbital sodium, and colon segments were studied in Ussing chambers in HCO3−Ringer under short-circuit conditions. Receptor-deficient mouse proximal colon exhibited similar net Na+absorption, lower net Cl−absorption, and a negative residual ion flux ( JR), indicating net HCO3−absorption compared with that in normal mice. In normal mouse proximal colon, mucosal addition of 50 nM Escherichia coli heat-stable enterotoxin (STa) increased the serosal-to-mucosal flux of Cl−( Js→mCl) and decreased net Cl−flux ( JnetCl) accompanied by increases in short-circuit current ( Isc), potential difference (PD), and tissue conductance ( G). Serosal STa had no effect. In distal colon neither mucosal nor serosal STa affected ion transport. In receptor-deficient mice, neither mucosal nor serosal 500 nM STa affected electrolyte transport in proximal or distal colon. In these mice, 1 mM 8-bromo-cGMP produced changes in proximal colon Js→mCland JnetCl, Isc, PD, G, and JRsimilar to mucosal STa addition in normal mice. We conclude that the GCC receptor is necessary in the mouse proximal colon for a secretory response to mucosal STa.
Influence of microbial species on small intestinal myoelectric activity and transit in germ-free rats
Authors: Husebye Einar , Hellström Per M. , Sundler Frank , Chen Jie , Midtvedt Tore
Published: December 2017

The effect of an intestinal microflora consisting of selected microbial species on myoelectric activity of small intestine was studied using germ-free rat models, with recording before and after specific intestinal colonization, in the unanesthetized state. Intestinal transit, neuropeptides in blood (RIA), and neuromessengers in the intestinal wall were determined. Clostridium tabificum vp 04 promoted regular spike burst activity, shown by a reduction of the migrating myoelectric complex (MMC) period from 30.5 ± 3.9 min in the germ-free state to 21.2 ± 0.14 min ( P < 0.01). Lactobacillus acidophilus A10 and Bifidobacterium bifidum B11 reduced the MMC period from 27.9 ± 4.5 to 21.5 ± 2.1 min ( P < 0.02) and accelerated small intestinal transit ( P < 0.05). Micrococcus luteus showed an inhibitory effect, with an MMC period of 35.9 ± 9.3 min compared with 27.7 ± 6.3 min in germ-free rats ( P < 0.01). Inhibition was indicated also for Escherichia coli X7gnotobiotic rats. No consistent changes in slow wave frequency were observed. The concentration of neuropeptide Y in blood decreased after introduction of conventional intestinal microflora, suggesting reduced inhibitory control. Intestinal bacteria promote or suppress the initiation and aboral migration of the MMC depending on the species involved. Bacteria with primitive fermenting metabolism (anaerobes) emerge as important promoters of regular spike burst activity in small intestine.
Swallow-related cerebral cortical activity maps are not specific to deglutition
Authors: Kern Mark , Birn Rasmus , Jaradeh Safwan , Jesmanowicz Andrei , Cox Robert , Hyde James , Shaker Reza
Published: December 2017

Cortical representation of swallow-related motor tasks has not been systematically investigated. In this study, we elucidated and compared these cortical representations to those of volitional swallow using block-trial and single-trial methods. Fourteen volunteers were studied by functional magnetic resonance imaging. Cortical activation during both swallowing and swallow-related motor tasks that can be performed independent of swallowing, such as jaw clenching, lip pursing, and tongue rolling, was found in four general areas: the anterior cingulate, motor/premotor cortex, insula, and occipital/parietal region corresponding to Brodmann's areas 7, 19, and 31. Regions of activity, volume of activated voxels, and increases in signal intensity were found to be similar between volitional swallow and swallow-related motor tasks. These findings, using both block-trial and single-trial techniques, suggest that cerebral cortical regions activated during swallowing may not be specific to deglutitive function.
Lactase synthesis is pretranslationally regulated in protein-deficient pigs fed a protein-sufficient diet
Authors: Dudley Mary A. , Schoknecht Patricia A. , Dudley Alden W. , Jiang Lan , Ferraris Ronaldo P. , Rosenberger Judy N. , Henry Joseph F. , Reeds Peter J.
Published: December 2017

The in vivo effects of protein malnutrition and protein rehabilitation on lactase phlorizin hydrolase (LPH) synthesis were examined. Five-day-old pigs were fed isocaloric diets containing 10% (deficient, n = 12) or 24% (sufficient, n = 12) protein. After 4 wk, one-half of the animals in each dietary group were infused intravenously with [13C1]leucine for 6 h, and the jejunum was analyzed for enzyme activity, mRNA abundance, and LPH polypeptide isotopic enrichment. The remaining animals were fed the protein-sufficient diet for 1 wk, and the jejunum was analyzed. Jejunal mass and lactase enzyme activity per jejunum were significantly lower in protein-deficient vs. control animals but returned to normal with rehabilitation. Protein malnutrition did not affect LPH mRNA abundance relative to elongation factor-1α , but rehabilitation resulted in a significant increase in LPH mRNA relative abundance. Protein malnutrition significantly lowered the LPH fractional synthesis rate (FSR; %/day), whereas the FSR of LPH in rehabilitated and control animals was similar. These results suggest that protein malnutrition decreases LPH synthesis by altering posttranslational events, whereas the jejunum responds to rehabilitation by increasing LPH mRNA relative abundance, suggesting pretranslational regulation.
Regulated MIP-3α/CCL20 production by human intestinal epithelium: mechanism for modulating mucosal immunity
Authors: Izadpanah Arash , Dwinell Michael B. , Eckmann Lars , Varki Nissi M. , Kagnoff Martin F.
Published: December 2017

Human intestinal epithelial cells secrete an array of chemokines known to signal the trafficking of neutrophils and monocytes important in innate mucosal immunity. We hypothesized that intestinal epithelium may also have the capacity to play a role in signaling host adaptive immunity. The CC chemokine macrophage inflammatory protein (MIP)-3α/CCL20 is chemotactic for immature dendritic cells and CD45RO+T cells that are important components of the host adaptive immune system. In these studies, we demonstrate the widespread production and regulated expression of MIP-3α by human intestinal epithelium. Several intestinal epithelial cell lines were shown to constitutively express MIP-3α mRNA. Moreover, MIP-3α mRNA expression and protein production were upregulated by stimulation of intestinal epithelial cells with the proinflammatory cytokines tumor necrosis factor-α or interleukin-1α or in response to infection with the enteric bacterial pathogens Salmonella or enteroinvasive Escherichia coli. In addition, MIP-3α was shown to function as a nuclear factor-κB target gene. In vitro findings were paralleled in vivo by increased expression of MIP-3α in the epithelium of cytokine-stimulated or bacteria-infected human intestinal xenografts and in the epithelium of inflamed human colon. Mucosal T cells, other mucosal mononuclear cells, and intestinal epithelial cells expressed CCR6, the cognate receptor for MIP-3α. The constitutive and regulated expression of MIP-3α by human intestinal epithelium is consistent with a role for epithelial cell-produced MIP-3α in modulating mucosal adaptive immune responses.
V. Cholera: invasion of the intestinal epithelial barrier by a stably folded protein toxin
Authors: Lencer Wayne I.
Published: December 2017

Cholera toxin (CT) produced by Vibrio cholerae is the virulence factor responsible for the massive secretory diarrhea seen in Asiatic cholera. To cause disease, CT enters the intestinal epithelial cell as a stably folded protein by co-opting a lipid-based membrane receptor, ganglioside GM1. GM1sorts the toxin into lipid rafts and a retrograde trafficking pathway to the endoplasmic reticulum, where the toxin unfolds and transfers its enzymatic subunit to the cytosol, probably by dislocation through the translocon sec61p. The molecular determinants that drive entry of CT into this pathway are encoded entirely within the structure of the protein toxin itself.
In vivo recognition of mannosylated proteins by hepatic mannose receptors and mannan-binding protein
Authors: Opanasopit Praneet , Shirashi Keiko , Nishikawa Makiya , Yamashita Fumiyoshi , Takakura Yoshinobu , Hashida Mitsuru
Published: December 2017

In vivo recognition of mannosylated proteins by hepatic mannose receptors and serum mannan-binding protein (MBP) was investigated in mice. After intravenous administration, all three different111In-mannosylated proteins were taken up mainly by liver, and uptake was saturated with increasing doses.111In-Man-superoxide dismutases and111In-Man12- and111In-Man16-BSA had simple dose-dependent pharmacokinetic profiles, whereas other derivatives (111In-Man25-, -Man35-, and -Man46-BSA and111In-Man-IgGs) showed slow hepatic uptake at <1 mg/kg. Purified MBP experiments in vitro indicated that these derivatives bind to MBP in serum after injection, which interferes with their hepatic uptake. To quantitatively evaluate these recognition properties in vivo, a pharmacokinetic model-based analysis was performed for111In-Man-BSAs, estimating some parameters, including the Michaelis-Menten constant of the hepatic uptake and the dissociation constant of MBP, which correlate to the affinity of Man-BSAs for mannose receptors and MBP, respectively. The dissociation constant of Man-BSA and MBP decreased dramatically with increasing density of mannose, but the Michaelis-Menten constant of hepatic uptake of Man-BSA was not so sensitive to the change in density. This suggests that the in vivo recognition of MBP has a stronger cluster effect than that of mannose receptors. Differences obtained here are due to the unique arrangement of carbohydrate recognition domains on each mannose-specific lectin available for mannosylated ligand recognition.
Deglutitive movement of the tongue under local anesthesia
Authors: Fujiki Tatsuya , Takano-Yamamoto Teruko , Tanimoto Keiji , Sinovcic Jorge Nicolas Pereira , Miyawaki Shouichi , Yamashiro Takashi
Published: December 2017

The purpose of the present study was to investigate whether or not sensory input from the tongue affects deglutitive tongue movement. Subjects were seven healthy volunteers with anesthetic applied to the surface of the tongue (surface group) and seven healthy volunteers with the lingual nerve blocked by anesthetic (blocked group). We established six stages in deglutition and analyzed deglutitive tongue movement and the time between the respective stages by cineradiography before and after anesthesia. After anesthesia in both surface and blocked groups, deglutitive tongue movement slowed and bolus movement was delayed. The deglutitive tongue tip retreated in the blocked group. These results suggest that delay of tongue movement by anesthesia causes weak bolus propulsion and that deglutitive tongue tip position is affected by sensory deprivation of the tongue or the region innervated by the inferior alveolar nerve.
Relationship between esophageal muscle thickness and intraluminal pressure: an ultrasonographic study
Authors: Pehlivanov Nonko , Liu Jianmin , Kassab Ghassan S. , Puckett James L. , Mittal Ravinder K.
Published: December 2017

A number of studies show a close temporal relationship between the rate of change in muscle thickness as detected by high-frequency intraluminal ultrasonography (HFIUS) and intraluminal pressure measured by manometry. There is a marked variability in esophageal contraction amplitude from one swallow to another at a given level in the esophagus and along the length of the esophagus. Furthermore, peristaltic pressures are higher in the distal compared with the proximal esophagus. The goal of this study was to evaluate the relationship between the baseline and peak muscle thickness and the contraction amplitude during swallow-induced contractions along the length of the esophagus. Fifteen normal subjects were studied using simultaneous esophageal pressures and HFIUS or HFIUS alone. Recordings were made during baseline and standardized swallows in the lower esophageal sphincter (LES) and at 2, 4, 6, 8, and 10 cm above the LES. HFIUS images were digitized, and esophageal muscle thickness and peak contraction amplitudes were measured. In the resting state, muscle thickness is higher in the LES compared with the rest of the esophagus. Baseline muscle thickness is also significantly higher at 2 cm vs. 10 cm above the LES. In a given subject and among different subjects, there is a good relationship between peak muscle thickness and peak peristaltic pressures (r = 0.55) at all sites along the length of the esophagus. The positive correlation between pressure and muscle thickness implies that the mean circumferential wall stress is fairly uniform from one swallow to another, irrespective of the contraction amplitude.
Mechanism of action of baclofen in rat dorsal motor nucleus of the vagus
Authors: Browning K. N. , Travagli R. A.
Published: December 2017

Using whole cell patch-clamp recordings, we investigated the effects of the GABAB receptor agonist baclofen in thin slices of rat brain stem containing identified gastric- or intestinal-projecting dorsal motor nucleus of the vagus (DMV) neurons. Perfusion with baclofen (0.1–100 μM) induced a concentration-dependent outward current (EC50, 3 μM) in 54% of DMV neurons with no apparent differences between gastric- and intestinal-projecting neurons. The outward current was attenuated by pretreatment with the selective GABAB antagonists saclofen and 2-hydroxysaclofen, but not by the synaptic blocker TTX, indicating a direct effect at GABAB receptors on DMV neurons. Using the selective ion channel blockers barium, nifedipine, and apamin, we showed that the outward current was due to effects on potassium and calcium currents as well as calcium-dependent potassium currents. The calcium-mediated components of the outward current were more prominent in intestinal-projecting neurons than in gastric-projecting neurons. These data indicate that although baclofen inhibits both intestinal- and gastric-projecting neurons in the rat DMV, its mechanism of action differs among the neuronal subpopulations.
Hepatic uptake and metabolism of benzoate: a multiple indicator dilution, perfused rat liver study
Authors: Schwab Andreas J. , Tao Lei , Yoshimura Tsutomu , Simard André , Barker Ford , Pang K. Sandy
Published: December 2017

Multiple, noneliminated references (51Cr-labeled erythrocytes,125I-albumin, [14C]- or [3H]sucrose, and [2H]2O), together with [3H]hippurate or [14C]benzoate, were injected simultaneously into the portal vein of the perfused rat liver during single-pass delivery of benzoate (5–1,000 μM) and hippurate (5 μM) to investigate hippurate formation kinetics and transport. The outflow dilution data best fit a space-distributed model comprising vascular and cellular pools for benzoate and hippurate; there was further need to segregate the cellular pool of benzoate into shallow (cytosolic) and deep (mitochondrial) pools. Fitted values of the membrane permeability-surface area products for sinusoidal entry of unbound benzoate were fast and concentration independent (0.89 ± 0.17 ml · s−1· g−1) and greatly exceeded the plasma flow rate (0.0169 ± 0.0018 ml · s−1· g−1), whereas both the influx of benzoate into the deep pool and the formation of hippurate occurring therein appeared to be saturable. Results of the fit to the dilution data suggest rapid uptake of benzoate, with glycination occurring within the deep and not the shallow pool as the rate-determining step.
The intestine expresses pancreatic triacylglycerol lipase: regulation by dietary lipid
Authors: Mahan James T. , Heda Ghanshyam D. , Rao R. Hanumantha , Mansbach Charles M.
Published: December 2017

We identified the enzyme responsible for alkaline lipolysis in mucosa of rat small intestine. RT-PCR was used to amplify a transcript that, by cloning and sequencing, is identical to pancreatic triacylglycerol lipase. In rats fed normal laboratory chow, pancreatic triacylglycerol lipase mRNA was detected in all four quarters of the small intestine, with the first quarter expressing about three times as much of this transcript as was found in the more distal three-quarters combined. Both acutely and chronically administered dietary fat were shown to regulate pancreatic triacylglycerol lipase mRNA expression and lipase activity. The synthesis of pancreatic triacylglycerol lipase protein by the small intestine was demonstrated by in vivo radiolabeling experiments using [35S]methionine/cysteine followed by immunoprecipitation with an anti-pancreatic triacylglycerol lipase antibody. Immunohistochemical studies suggest that pancreatic triacylglycerol lipase protein expression is restricted to enterocytes throughout the small intestine. To our knowledge, this is the first report identifying rat small intestinal mucosa as a site of pancreatic triacylglycerol lipase synthesis and the first demonstration of its modulation in the mucosa by dietary fat. We propose that pancreatic triacylglycerol lipase is used by the intestine to hydrolyze the mucosal triacylglycerol that is not transported in chylomicrons.
iNOS upregulation mediates oxidant-induced disruption of F-actin and barrier of intestinal monolayers
Authors: Banan A. , Fields J. Z. , Zhang Y. , Keshavarzian A.
Published: December 2017

Using oxidant-induced hyperpermeability of monolayers of intestinal (Caco-2) cells as a model for the pathophysiology of inflammatory bowel disease (IBD), we previously showed that oxidative injury to the F-actin cytoskeleton is necessary for the disruption of monolayer barrier integrity. We hypothesized that this cytoskeletal damage is caused by upregulation of an inducible nitric oxide (NO) synthase (iNOS)-driven pathway that overproduces reactive nitrogen metabolites (RNMs) such as NO and peroxynitrite (OONO−), which cause actin nitration and disassembly. Monolayers were exposed to H2O2or to RNMs with and without pretreatment with antioxidants or iNOS inhibitors. H2O2concentrations that disassembled and/or disrupted the F-actin cytoskeleton and barrier integrity also caused rapid iNOS activation, NO overproduction, and actin nitration. Added OONO−mimicked H2O2; iNOS inhibitors and RNM scavengers were protective. Our results show that oxidant-induced F-actin and intestinal barrier disruption are caused by rapid iNOS upregulation that further increases oxidant levels; a similar positive feedback mechanism may underlie the episodic recurrence of the acute IBD attack. Confirming these mechanisms in vivo would provide a rationale for developing novel anti-RNM therapies for IBD.
Cell proliferation, apoptosis, NF-κB expression, enzyme, protein, and weight changes in livers of burned rats
Authors: Jeschke Marc G. , Low J. F. Aili , Spies Marcus , Vita Randi , Hawkins Hal K. , Herndon David N. , Barrow Robert E.
Published: December 2017

Thermal injury has been shown to alter gut epithelium and heart myocyte homeostasis by inducing programmed cell death. The effect of thermal injury on hepatocyte apoptosis and proliferation, however, has not been established. The purpose of this study was to determine whether a large thermal injury increases liver cell apoptosis and proliferation and whether these changes were associated with alterations in hepatic nuclear factor κB (NF-κB) expression and changes in liver enzymes and amount of protein. Sprague-Dawley rats received a 40% total body surface area scald burn or sham burn. Rats were killed and livers were harvested at 1, 2, 5, and 7 days after burn. Liver cell apoptosis was determined by terminal deoxyuridine nick end labeling (TUNEL) assay and cell proliferation by immunohistochemistry for proliferating cell nuclear antigen. Hepatic NF-κB expression was determined by Western blot, and total hepatic protein content was determined by protein assay. Protein concentration decreased after burn compared with sham controls ( P < 0.05). Liver cell apoptosis, proliferation, and NF-κB expression in hepatocytes increased in burned rats compared with controls ( P < 0.05). It was concluded that thermal injury induces hepatic cell apoptosis and proliferation associated with an increase in hepatic NF-κB expression and a decrease in hepatic protein concentration.
Neural change inTrichinella-infected mice is MHC II independent and involves M-CSF-derived macrophages
Authors: Galeazzi Francesca , Lovato Paola , Blennerhassett Patricia A. , Haapala Eric M. , Vallance Bruce A. , Collins Stephen M.
Published: December 2017

Intestinal inflammation due to nematode infection impairs enteric cholinergic nerve function and induces hypercontractility of intestinal muscle. Macrophages have been implicated in the neural changes, but the subpopulation and mechanism involved are unknown. We examined whether macrophages alter nerves by virtue of their ability to activate lymphocytes via major histocompatibility complex (MHC) II-restricted antigen presentation. We also attempted to evaluate the role of macrophage subsets using op/op mice deficient in macrophage colony-stimulating factor (M-CSF). ACh release from the myenteric plexus was measured in MHC II- and M-CSF-deficient ( op/op) mice infected with Trichinella spiralis. F4/80-positive macrophages and interleukin-1β were constitutively present in op/op and op/? mice but increased only in op/? mice postinfection. After infection, a marked suppression of ACh release occurred only in infected MHC II-deficient and op/? mice. Muscle hypercontractility remained evident in infected op/? mice. Treatment with M-CSF restored macrophage number, and this was accompanied by suppression of cholinergic nerve function during infection. Thus M-CSF plays a critical role in this model by recruiting a subset of macrophages that selectively suppresses enteric neural function.
Neural regulation of in vitro giant contractions in the rat colon
Authors: Gonzalez Asensio , Sarna Sushil K.
Published: December 2017

The rat middle colon spontaneously generates regularly occurring giant contractions (GCs) in vitro. We investigated the neurohumoral and intracellular regulation of these contractions in a standard muscle bath. cGMP content was measured in strips and single smooth muscle cells. The circular muscle strips generated spontaneous GCs. Their amplitude and frequency were significantly increased by tetrodotoxin (TTX), ω-conotoxin, N ω-nitro-l-arginine (l-NNA), and the dopamine D1 receptor antagonist Sch-23390. The GCs were unaffected by hexamethonium, atropine, and antagonists of serotonergic (5-HT1–4), histaminergic (H1–2), and tachykininergic (NK1–2) receptors but enhanced by NK3receptor antagonism. The guanylate cyclase inhibitor 1H-[1,2,4]oxidiazolo[4,3-a]quinoxalin-1-one (ODQ) also enhanced GCs to the same extent as TTX and l-NNA, and each of the three agents prevented the effects of the others. GCs were abolished by electrical field stimulation, S-nitroso- N-acetyl-penicillamine, and 8-bromo-cGMP. BAY-K-8644 and apamin enhanced the GCs, but they were abolished by D-600. Basal cGMP content in strips was decreased by TTX,l-NNA, or ODQ, but these treatments had no effect on cGMP content of enzymatically dissociated single smooth muscle cells. We conclude that spontaneous contractions in the rat colonic muscle strips are not generated by cholinergic, serotonergic, or histaminergic input. Constitutive release of nitric oxide from enteric neurons sustains cGMP synthesis in the colonic smooth muscle to suppress spontaneous in vitro GCs.
Vagal afferent input determines the volume dependence of rat esophageal motility patterns
Authors: Dong Haiheng , Loomis Christopher W. , Bieger Detlef
Published: December 2017

The volume dependence of balloon distension-evoked esophageal rhythmic motor responses and their neural correlates was investigated in 72 urethane-anesthetized rats. With increasing balloon volume (75–200 μl), distal esophageal rhythmic contractions decreased in rate and became tonic in the range of 150–250 μl. This change in motor pattern involved only the striated musculature of the esophageal body and persisted after acute transection of the spinal cord at C2. Impulse frequency in single vagal afferents of the distal esophagus increased with intraluminal pressure over the entire range of balloon volumes tested (50–300 μl). Distension-responsive neurons in the nucleus tractus solitarii showed rhythmic burst activity (type I), tonic excitation (type II), or inhibition followed by off bursts (type III). Increasing strength of stimulation changed type I responses to nonrhythmic but intensified type II and III responses. We conclude that load-dependent changes in distal esophagus motility pattern are encoded by vagal afferents alone and do not involve a spinal afferent input even at near-noxious stimulus strengths.
Mechanism of folate transport across the human colonic basolateral membrane
Authors: Dudeja P. K. , Kode A. , Alnounou M. , Tyagi S. , Torania S. , Subramanian V. S. , Said H. M.
Published: December 2017

Previous studies from our laboratory have demonstrated the existence of a folate transporter in the human colonic apical membranes. The current studies were undertaken to examine the possible presence and function of a folate carrier in the human colonic basolateral membrane vesicles (BLMV). BLMV were purified from mucosal scrapings of colons of organ donors by a Percoll-density gradient centrifugation technique, and uptake studies were performed using a rapid filtration technique. Our results on [3H]Pte-Glu uptake are summarized as follows: 1) uptake was sensitive to osmolarity of the incubation medium; 2) Na+removal from the incubation medium did not affect folate uptake into BLMV; 3) uptake was significantly increased with decreasing incubation buffer pH from 8 to 4; 4) uptake demonstrated saturation kinetics with an apparent Michaelis constant of 9.6 ± 0.48 μM and a maximal velocity of 8.10 ± 0.36 pmol · mg protein−1· 10 s−1; 5) uptake was markedly inhibited by the structural analog methotrexate (inhibitory constant = 8.28 ± 1.0 μM); 6) uptake into BLMV demonstrated a trans-stimulation phenomenon; 7) anion exchange inhibitors DIDS and SITS significantly inhibited folate uptake; and 8) uptake was potential-insensitive, as voltage clamping of vesicles or making them inside positive with K+/valinomycin failed to influence folate uptake. Western blot analysis using purified human colonic basolateral membrane preparations and specific polyclonal antibodies against the human reduced folate carrier (hRFC) has shown expression of the hRFC protein at this membrane domain. These data demonstrate the existence of a pH-dependent, DIDS-sensitive, electroneutral, carrier-mediated mechanism for folate transport across the human colonic basolateral membranes.
Differential activation of intestinal gene promoters: functional interactions between GATA-5 and HNF-1α
Authors: Krasinski Stephen D. , Van Wering Herbert M. , Tannemaat Martijn R. , Grand Richard J.
Published: December 2017

The effects of GATA-4, -5, and -6, hepatocyte nuclear factor-1α (HNF-1α) and -β, and Cdx-2 on the rat and human lactase-phlorizin hydrolase (LPH) and human sucrase-isomaltase (SI) promoters were studied using transient cotransfection assays in Caco-2 cells. GATA factors and HNF-1α were strong activators of the LPH promoters, whereas HNF-1α and Cdx-2 were strong activators of the SI promoter, although GATA factors were also necessary for maximal activation of the SI gene. Cotransfection of GATA-5 and HNF-1α together resulted in a higher activation of all three promoters than the sum of the activation by either factor alone, demonstrating functional cooperativity. In the human LPH promoter, an intact HNF-1 binding site was required for functional synergy. This study is the first to demonstrate 1) differential activation of the LPH and SI promoters by multiple transcription factors cotransfected singly and in combination and 2) that GATA and HNF-1 transcription factors cooperatively activate intestinal gene promoters. Synergistic activation is a mechanism by which higher levels of tissue-specific expression might be attained by overlapping expression of specific transcription factors.
H. pylori and transient lower esophageal sphincter relaxations induced by gastric distension in healthy humans
Authors: Zerbib Frank , Bicheler Valérie , Leray Véronique , Joubert Madeleine , Bruley des Varannes Stanislas , Galmiche Jean-Paul
Published: December 2017

The role of Helicobacter pylori infection in the control of lower esophageal sphincter (LES) motility, especially the occurrence of transient LES relaxations (TLESRs), was studied in eight H. pylori-positive and eight H. pylori-negative healthy subjects. During endoscopy, biopsy specimens were taken from the cardia, fundus, and antrum for determinations of H. pyloristatus, gastritis, and proinflammatory cytokine mucosal concentrations. LES motility was monitored during three different 30-min periods: baseline, gastric distension (barostat), and gastric distension with CCK infusion. Gastric distension significantly increased the TLESR rate, whereas CCK increased the rate of distension-induced TLESRs further and reduced resting LES pressure without significant differences between infected and noninfected subjects. H. pylori status did not influence resting LES pressure or gastric compliance. Cytokine mucosal concentrations were increased in infected patients, but no correlation was found with the TLESR rate, which was also independent of inflammation at the cardia, fundus, and antrum. These results suggest that H. pylori-associated inflammation does not affect the motor events involved in the pathogenesis of gastroesophageal reflux.
Influence of pH on the phase distribution of nascent deoxycholic acid in fresh human cecal aspirates
Authors: Thomas Linzi A. , Veysey Martin J. , Murphy Gerard M. , Dowling R. Hermon
Published: December 2017

Prolonged large bowel transit time and an associated increase in the proportion of deoxycholic acid (DCA) in serum and bile have been implicated in the development of cholesterol-rich gallstones and colon cancer. Prolongation of intestinal transit also increases intracolonic pH that, we hypothesized, should favor the solubilization and absorption of newly formed DCA within the colon. To test this hypothesis, we performed in vitro studies on homogenized cecal aspirates (obtained at colonoscopy) that were incubated anaerobically with [14C]cholic acid for 16 h after which the pH was adjusted to between 4.0 and 7.0 in 0.5-pH unit steps. The resultant reaction mixtures were centrifuged to separate the supernatant from the precipitate, and the specific activity of [14C]DCA was quantitated in both phases. As the pH in the aspirates was manipulated from 4.0 to 7.0, the proportion of newly formed, labeled DCA increased in the supernatant and fell in the precipitate, particularly at a hydrogen ion concentration of <100 × 10−7(equivalent to pH 5.0–7.0). These results show that the solubility of DCA in colonic contents increases with increasing pH. If solubility is rate limiting, this should lead to increased absorption that, in turn, would explain why the proportion of DCA in serum and bile increases with the prolongation of large bowel transit time.
Substrate utilization by intestinal mucosal tissue strips from patients with inflammatory bowel disease
Authors: Jørgensen Jimmy , Mortensen Per Brøbech
Published: December 2017

A primary metabolic disorder may be present in the colonic mucosa of patients with ulcerative colitis. Preserving the epithelium in situ, we evaluated the metabolism of the colonic mucosa of control patients and patients with ulcerative colitis and Crohn's disease. Colonic mucosal strips (∼500 mg) were incubated with partially14C-labeled acetate (C2), butyrate (C4), hexanoate (C6), octanoate (C8), and glucose, and the production of CO2and ketone bodies was quantitated. Metabolism by small intestinal mucosal strips was also evaluated. Compared with controls, no decrease in either CO2or ketone body production by colonic strips from patients with either ulcerative colitis or Crohn's disease was observed for any substrate. The CO2production from each of the C2–C8fatty acids was the same for colonic and small intestinal strips, whereas CO2production from glucose was higher in small intestinal strips than in colonic strips. The production of ketone bodies was low in small intestinal strips. A primary metabolic disorder in the colonic mucosa of patients with inflammatory bowel disease was not found.
Sustained esophageal contraction: a motor correlate of heartburn symptom
Authors: Pehlivanov Nonko , Liu Jianmin , Mittal Ravinder K.
Published: December 2017

Heartburn occurs in the presence as well as the absence of acid reflux. We searched for a motor correlate of heartburn. Twelve subjects with heartburn were studied with 24-h synchronized pressure, pH, and high-frequency intraluminal ultrasound (HFIUS) imaging of the esophagus. The HFIUS images were analyzed every 2 s for a period of 2 min before and 30 s after the onset of heartburn during 20 acid reflux-positive and 20 acid reflux-negative heartburn episodes. The esophageal muscle thickness was measured as a marker of contraction. Esophageal pressure and HFIUS images were recorded during the Bernstein test in 15 subjects. Sustained esophageal contractions (SECs) were identified during 13 of 20 heartburn episodes associated with acid reflux and 15 of 20 heartburn episodes without acid reflux. SECs were detected during 2 of 40 matched control periods only ( P < 0.05). The duration of SECs was 44.9 ± 26.9 s. The Bernstein test reproduced heartburn symptoms in 8 of 15 subjects. SECs were identified during 6 of 8 (75%) Bernstein-positive and in 1 of 7 (14.3%) Bernstein-negative tests ( P = 0.04). We conclude that a SEC precedes both spontaneous and induced heartburn symptoms and may be the cause of heartburn sensation.
Changes in serotonin levels and 5-HT receptor activity in duodenum of streptozotocin-diabetic rats
Authors: Takahara H. , Fujimura M. , Taniguchi S. , Hayashi N. , Nakamura T. , Fujimiya M.
Published: December 2017

Few previous studies have discussed the changes in serotonin receptor activity in the small intestine of diabetic animals. Therefore, we examined serotonin content in duodenal tissue and dose-dependent effects of serotonin agonists and antagonists on the motor activity of ex vivo vascularly perfused duodenum of streptozotocin (STZ)-diabetic rats. Serotonin content was significantly increased in enterochromaffin cells but not altered in serotonin-containing neurons in STZ-diabetic rats. Motor activity assessed by frequency, amplitude, and percent motility index per 10 min of pressure waves was reduced in the duodenum of diabetic rats, and this reduction was reversed by insulin treatment. Serotonin dose dependently increased the motor activity in control rat duodenum but only a higher concentration of serotonin increased the motor activity in diabetic rats. The 5-hydroxytryptamine (5-HT) receptor subtype 4 (5-HT4) antagonist SB-204070 dose dependently reduced motor activity in both control and diabetic rats, whereas the 5-HT3receptor antagonist azasetron, even at a higher concentration, failed to affect motor activity in diabetic rat duodenum but dose dependently reduced motor activity in control rat duodenum. These results suggest that 5-HT3receptor activity was impaired but 5-HT4receptor activity was intact in STZ-diabetic rat duodenum. Such an impairment of 5-HT3receptor activity may induce the motility disturbance in the small intestine of diabetes mellitus.
Association of protein kinase A with AKAP150 facilitates pepsinogen secretion from gastric chief cells
Authors: Xie Guofeng , Raufman Jean-Pierre
Published: December 2017

Cross talk between signal transduction pathways augments pepsinogen secretion from gastric chief cells. A-kinase anchoring proteins (AKAPs) associate with regulatory subunits of protein kinase A (PKA), protein kinase C (PKC), and protein phosphatase 2B (PP2B) and localize this protein complex to specific cell compartments. We determined whether an AKAP-signaling protein complex exists in chief cells and whether this modulates secretion. In Western blots, we identified AKAP150, a rodent homologue of human AKAP79 that coimmunoprecipitates with PKA, PKC, and actin. The association of PKA and PP2B was demonstrated by affinity chromatography. Confocal microscopy revealed colocalized staining at the cell periphery for AKAP150 and PKC. Ht31, a peptide that competitively displaces PKA from the AKAP complex, but not Ht31P, a control peptide, inhibited 8-Br-cAMP-induced pepsinogen secretion. Ht31 did not inhibit secretion that was stimulated by agents whose actions are mediated by PKC and/or calcium. However, Ht31, but not Ht31P, inhibited carbachol- and A23187 -stimulated augmentation of secretion from cells preincubated with cholera toxin. These data suggest the existence in chief cells of a protein complex that includes AKAP150, PKA, PKC, and PP2B. Disruption of the AKAP-PKA linkage impairs cAMP-mediated pepsinogen secretion and cross talk between signaling pathways.