bluuebunny/crossref_metadata_2025 huggingface dataset:
TRH and substance P independently affect gastric motility in nucleus raphe obscurus of the rat
Authors: Krowicki Z. K. , Hornby P. J.
Published: December 2017

The purpose of this study was to investigate whether there exists a functional interaction between thyrotropin-releasing hormone (TRH) and substance P (SP) in the nucleus raphe obscurus (NRO) in their effects on gastric motor function. This was accomplished by microinjection of TRH (6-45 pmol) and SP (10 and 135 pmol) into the NRO alone and then either as a mixture or in rapid sequential order in alpha-chloralose-anesthetized rats, while intragastric pressure and pyloric and greater curvature motility were monitored. TRH (15 and 45 pmol) evoked significant increases in gastric motor activity, whereas SP (135 pmol) elicited decreases in intragastric pressure. SP at a dose of 10 pmol was ineffective alone in altering gastric motor function. Microinjection of a mixture of TRH (15 pmol) and SP (10 pmol) into the NRO resulted in significant increases in intragastric pressure, pyloric motility, and greater curvature motility; these changes in gastric motor function were similar to the effect of TRH (15 pmol) alone. A mixture of TRH (15 pmol) and SP (135 pmol) resulted in changes in gastric motor activity that were significantly less than the effect of TRH (15 pmol) microinjected into the NRO alone and appeared to be an additive effect of each peptide. The results of sequential microinjections of both peptides were consistent with these findings. The stimulative effect of TRH (15 and 45 pmol) on intragastric pressure, microinjected into the NRO 30 s after SP (135 pmol), did not differ from the effect of TRH microinjected at the same doses after vehicle.(ABSTRACT TRUNCATED AT 250 WORDS)
Pleiotropic effect of LEC mutation: a rodent model of Wilson's disease
Authors: Schilsky M. L. , Stockert R. J. , Sternlieb I.
Published: December 2017

Metabolic studies with 67Cu were undertaken to identify the site of the cellular defect in copper metabolism in the Long-Evans Cinnamon (LEC) rat. The apparent rate of copper uptake by LEC primary hepatocytes was increased [maximal velocity (Vmax) = 259 pmol.min-1.mg protein-1] compared with controls (Vmax = 161 pmol.min-1.mg protein-1); however, Michaelis-Menten constant (Km) values were comparable (11.8 and 12.7 microM, LEC and control, respectively). Efflux of copper from LEC and control hepatocytes was similar from 0 to 15 min, but was reduced from 15 to 60 min in the former. Although hepatic copper contents were markedly elevated in LEC rats compared with controls (658 +/- 199 vs. 21.5 +/- 6.6 micrograms/g dry wt), biliary copper concentration was reduced in LEC rats compared with controls (0.187 vs. 1.39 +/- 0.66 microgram/ml). Subcellular fractionation of LEC liver homogenates revealed approximately 75% of copper to be present in cytosol, with gradients of copper concentration from cytosol to either lysosome or microsomal subcellular fractions. LEC rat bile and hepatic microsome and lysosome fractions contained smaller fractions of 67Cu administered intravenously as cupric acetate compared with control rats. However, recovery of 67Cu in bile and in lysosomal subcellular fractions were similar for LEC and controls following administration of 67Cu-labeled asialoceruloplasmin, which is targeted to lysosomes. This discordance suggests a possible defect in the entry of copper into lysosomes but normal delivery of lysosomal copper to bile. Based on these findings, we conclude that the mutation in LEC rats alters copper transport at more than one cellular site.
Upregulation of secretin receptor gene expression in rat cholangiocytes after bile duct ligation
Authors: Alpini G. , Ulrich C. D. , Phillips J. O. , Pham L. D. , Miller L. J. , LaRusso N. F.
Published: December 2017

Secretion stimulates ductular bile secretion by binding to receptors on intrahepatic bile duct epithelial cells (i.e., cholangiocytes). In the rat, this choleretic effect increases after bile duct ligation (BDL). Although cholangiocyte proliferation induced by BDL contributes to secretin-induced hypercholeresis, the mechanisms modulating these alterations in secretin-induced ductular bile secretion are obscure. Thus we studied the expression of secretin receptor mRNA (SR-mRNA) in purified liver cells from normal and BDL rats. Northern blot analysis and RNase protection assays with mRNA from purified liver cells demonstrated SR-mRNA only in cholangiocytes; moreover, SR gene expression showed a seven- to ninefold increase in individual cholangiocytes from BDL rats compared with controls. This increase in SR-mRNA expression was related to a similar increase in the rate of transcription of SR-mRNA in cholangiocytes from BDL rats. Thus our studies indicate that 1) SR-mRNA is detected in liver only in cholangiocytes; 2) BDL causes an increase in SR-mRNA in individual cholangiocytes; and 3) the increase in SR-mRNA after BDL is partly related to an increase in the rate of transcription of SR-mRNA by cholangiocytes after BDL. Our data suggest that upregulation of the SR gene may contribute to secretin-induced hypercholeresis.
Secretion and distribution of rat intestinal surfactant-like particles after fat feeding
Authors: Yamagishi F. , Komoda T. , Alpers D. H.
Published: December 2017

Triacylglycerol feeding increases serum intestinal alkaline phosphatase (IAP) activity and leads to the appearance of an alkaline phosphatase-containing particle in the luminal washings over the apical surface of the rat enterocyte and in the blood (J. Clin. Invest. 84: 1355-1361, 1989). To examine the coordinate appearance of these particles and the enzyme and to follow their distribution in vivo after feeding, an enzyme-linked immunoabsorbent assay (ELISA) was developed, using antisera raised against the purified intact surfactant-like particle. Tissue compartments that were examined for phosphatase activity and particle content included isolated enterocytes, lamina propria, intestinal luminal washings, and serum. Alkaline phosphatase activity peaked earliest in the lamina propria (3 h), followed by the enterocyte and the luminal washings (5 h) and serum (7 h). Surfactant-like particle content peaked in the enterocyte and lamina propria at 3 h, followed by the serum (3-5 h) and the luminal washings (5 h). The buoyant density of the particle in the enterocyte (d = 1.08-1.09) and serum (d = 1.07-1.08) after fat feeding was similar to that of the isolated particle (d = 1.07-1.08). The density of particle proteins detected by ELISA in fasted serum was more diffuse and > 1.10, consistent with partial degradation of the particle and/or its proteins. These data confirm that the particle and its bound IAP are secreted from the enterocyte after triacylglycerol feeding and that they appear in compartments adjacent to both the basolateral (serum) and apical (luminal wash) surfaces of the enterocyte.(ABSTRACT TRUNCATED AT 250 WORDS)
Relaxation responses of the human proximal stomach to distension during fasting and after food
Authors: Ahluwalia N. K. , Thompson D. G. , Barlow J. , Troncon L. E. , Hollis S.
Published: December 2017

The responses of the human proximal stomach to distension were studied in 22 healthy volunteers using an intragastric polyethylene bag, inflated progressively in 30-ml steps until the limit of tolerated volume was reached. Three successive inflations were carried out during the fasting state followed by a fourth inflation after ingestion of 250 ml of either a nutrient meal or isosmolar saline. The first inflation showed an initial nonlinear pressure rise (slope of logged pressure vs. volume = 114.6 +/- 10.0 log mmHg/ml x 10(-5)), which was then followed by the development of a plateau phase, in which further distension did not increase intragastric pressure. The slopes of the subsequent fasting inflations were significantly lower than that of the first inflation (P < 0.01) but were similar to each other (slope 83.0 +/- 5.4 and 79.8 +/- 5.7 log mmHg/ml x 10(-5)), indicating that distension-induced gastric relaxation had occurred. After saline ingestion, responses to distension were similar to those during the fasted state. After the nutrient meal ingestion, however, the slope decreased to 60.3 +/- 7.7 log mmHg/ml x 10(-5) (P < 0.01 vs. saline), indicating nutrient-induced gastric relaxation. Our study demonstrates that the pressure-volume characteristics of the proximal stomach are modulated both by distension and by the presence of nutrients in the upper gut, which appear to operate independently.
Effect of aging on neurotensin-stimulated growth of rat small intestine
Authors: Evers B. M. , Izukura M. , Rajaraman S. , Parekh D. , Thakore K. , Yoshinaga K. , Uchida T. , Townsend C. M. , Thompson J. C.
Published: December 2017

The proliferative activity of gut mucosa is altered with aging; the potential for the aged gut to respond to trophic stimuli is not known. The purpose of this study was to determine whether there are age-related differences in the effects of the trophic gut peptide neurotensin (NT) on the structure and function of small bowel mucosa. NT (300 micrograms/kg) or saline (control) was injected subcutaneously at 8-h intervals for 5 days in rats of two age groups, young (2 mo) and aged (24 mo). On day 6, rats were killed, and the gut mucosa (proximal and distal small bowel) was scraped, weighed, and analyzed for DNA, RNA, and protein content and for disaccharidase (sucrase and maltase) activity. In a second experiment, the groups of rats and the protocol for NT administration were identical; however, when the rats were killed, the distal gut was removed for histological evaluation of crypt and villus length (mm) and density (no./cm gut segment) and bromodeoxyuridine immunohistochemistry. NT produced significant increases in mucosal growth (wt, DNA, RNA, and protein) in both age groups when compared with age-matched controls; the increase of growth measurements was the greatest in the small bowel mucosa of the aged rats. In addition, NT increased crypt density in both groups; only the aged group treated with NT demonstrated increases in crypt depth and villus height. Specific activities of sucrase and maltase did not change with NT treatment in either of the age groups. We conclude that the proliferative potential of small bowel mucosa is maintained with aging in response to administration of NT.(ABSTRACT TRUNCATED AT 250 WORDS)
Activin A: negative regulator of amylase secretion and cell proliferation in rat pancreatic acinar AR42J cells
Authors: Yasuda H. , Tanaka S. , Ohnishi H. , Mashima H. , Ogushi N. , Mine T. , Kojima I.
Published: December 2017

Activin A, a member of the transforming growth factor-beta supergene family, exists in secretory granules of non-B-cells of rat pancreatic islet (H. Yasuda, K. Inoue, H. Shibata, T. Takeuchi, Y. Eto, Y. Hasegawa, N. Sekine, Y. Totsuka, T. Mine, E. Ogata, and I. Kojima. Endocrinology 133: 624-630, 1993). Because functions of exocrine pancreas are influenced by hormones in pancreatic islet, it is possible that activin A affects the function of pancreatic acinar cells. To examine this possibility, we studied the effects of activin A on amylase secretion and DNA synthesis in AR42J cells. In these cells, dexamethasone (Dx) induces increases in secretory organelles and secretion of amylase (C. D. Logsdon, J. Moessner, J. A. Williams, and I. D. Goldfine. J. Cell Biol. 100: 1200-1208 1985). Activin A did not change the rate of amylase release by itself nor affect the cholecystokinin-stimulated amylase release from Dx-treated differentiated AR42J cells. However, when activin A was added together with Dx, activin A inhibited Dx-induced increase in amylase content in a dose-dependent manner. In the presence of 1 nM activin A, the effect of Dx was abolished. In the absence of Dx, amylase content of the cells was also reduced by activin A in a dose-dependent manner. The maximum inhibitory effect was obtained by 10 nM activin A, and at this concentration amylase content became undetectable. In addition, activin A potently inhibited DNA synthesis as assessed by [3H]thymidine incorporation.(ABSTRACT TRUNCATED AT 250 WORDS)
Palmitate uptake by hepatocyte suspensions: effect of albumin
Authors: Burczynski F. J. , Cai Z. S.
Published: December 2017

The clearance ratio test has been used to determine whether hepatocytes isolated from female rat livers facilitate the dissociation rate of albumin-palmitate complexes. This test requires knowledge of the clearance rate and unbound palmitate fraction at two protein concentrations. The unbound fractions have been estimated using the heptane-water partition ratio method. These fractions were determined to deviate from the expected linear relationship because of radiolabeled impurities that were still present after purification of the [3H]palmitic acid. With the use of experimentally determined partition ratio values, the palmitate clearance ratios were statistically greater than those predicted by the diffusion-reaction model at albumin concentration combinations above 99 microM/49 microM. Experimental clearance rates also exceeded those predicted by the diffusion-reaction model, but only at albumin concentrations greater than 198 microM. These data support the proposal that hepatocytes facilitate the dissociation of albumin-palmitate complexes at high albumin concentrations.
Fibronectin in human gallbladder bile: cholesterol pronucleating and/or mucin "link" protein?
Authors: Miquel J. F. , Von Ritter C. , Del Pozo R. , Lange V. , Jungst D. , Paumgartner G.
Published: December 2017

Some biliary proteins (pronucleators) seem to be essential factors for cholesterol crystal formation and crystal growth in bile. A recent study suggests that fibronectin is such a pronucleator in bile. Fibronectin also seems to closely interact with intestinal mucin. Since biliary mucin plays an important role in gallstone formation, such an interaction in bile may be of relevance in cholesterol gallstone formation. To more clearly elucidate the role of fibronectin in cholesterol gallstone disease, we measured the concentration of fibronectin in native bile of cholesterol gallstone patients and checked its influence on the cholesterol nucleation time of model bile. We further looked for a molecular interaction between biliary fibronectin and gallbladder mucin. We found that fibronectin is present in gallbladder bile of gallstone patients in low concentrations (2.6 +/- 1.2 micrograms/ml). Bile fibronectin did not interact with gallbladder mucin. Moreover, in a wide range of concentrations fibronectin had no influence on the nucleation time of model bile. We conclude that fibronectin does not seem to play a major role in cholesterol gallstone disease.
Cholecystokinin rapidly activates mitogen-activated protein kinase in rat pancreatic acini
Authors: Duan R. D. , Williams J. A.
Published: December 2017

The existence and activation of mitogen-activated protein (MAP) kinase in isolated pancreatic acini have been demonstrated. Immunoblotting and immunoprecipitation revealed two forms of MAP kinase in pancreatic acini, with relative molecular masses of approximately 42 and 44 kDa. Both forms of MAP kinase were activated by cholecystokinin (CCK). The threshold concentration of CCK was approximately 3 pM, and the maximal effect occurred at 1 nM, which enhanced MAP kinase activity by 2.5-fold, as determined in polyacrylamide gel copolymerized with substrate myelin basic protein. Activation of MAP kinase by CCK was rapid, reaching a maximum within 5-10 min that subsequently declined. Bombesin and carbachol but not secretin or vasoactive intestinal peptide also activated MAP kinase. CCK-induced activation of MAP kinase may be mediated by protein kinase C, since 12-O-tetradecanoylphorbol 13-acetate (TPA) mimicked the effect of CCK and staurosporine concentration dependently inhibited the action of CCK. Treatment of acini with thapsigargin, ionomycin, or ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid did not influence MAP kinase, indicating that mobilization of intracellular calcium by CCK is not important in activation of acinar MAP kinase. CCK and TPA increased tyrosine phosphorylation of both 42- and 44-kDa forms. Genistein and tyrphostin 23, the inhibitors of tyrosine kinase, suppressed the activation of MAP kinase by CCK. In conclusion, MAP kinase in pancreatic acini is activated by agonists related to hydrolysis of phosphoinositide, via a mechanism involving protein kinase C and tyrosine kinase.
Transcriptional regulation of intestinal hydrolase biosynthesis during postnatal development in rats
Authors: Krasinski S. D. , Estrada G. , Yeh K. Y. , Yeh M. , Traber P. G. , Rings E. H. , Buller H. A. , Verhave M. , Montgomery R. K. , Grand R. J.
Published: December 2017

Lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) are intestine-specific microvillus membrane hydrolases whose specific activities demonstrate reciprocal regulation during development but whose mechanisms of regulation have not been fully defined. To investigate transcriptional control of these two proteins, the rat LPH and SI genes were cloned, and antisense probes for preprocessed mRNAs (pre-mRNAs) were developed from intron sequence. LPH mRNA, as measured by quantitative ribonuclease (RNase) protection assays, was abundant before weaning and decreased two- to fourfold during weaning, whereas SI mRNA was first detected 14 days after birth and increased rapidly to abundant levels by age 28 days. LPH and SI pre-mRNA levels paralleled those of their respective mRNAs. LPH transcriptional rate declined during weaning, whereas that of SI increased during this time as determined by RNase protection assays of pre-mRNAs and nuclear run-on assays. In the adult rat, LPH mRNA was restricted to the jejunum and proximal ileum, whereas SI mRNA was detected throughout the small intestine, a pattern regulated by transcriptional rate as confirmed by nuclear run-on assays. Lactase and sucrase specific activities correlated well with their respective protein and mRNA concentrations in all experiments. We conclude that gene transcription plays a major role in the developmental and horizontal regulation of LPH and SI biosynthesis and that these two genes are regulated differently in rat small intestine.
Effects of gender and pregnancy on hepatocellular uptake of palmitic acid: facilitation by albumin
Authors: Pond S. M. , Gordon R. A. , Wu Z. Y. , Weisiger R. A. , Bass L.
Published: December 2017

The human serum albumin (HSA)-dependent unbound clearance (Clu) of [3H]palmitic acid (PA) by hepatocyte suspensions isolated from immature and mature male and female and pregnant female rats was studied. The Clu values obtained experimentally were compared with the predictions of a noncompartmental diffusion-reaction (Bass-Pond) theory for the cellular uptake of protein-bound ligands. In all groups, as the concentration of HSA (Ca) was increased, there was a striking increase in Clu. These enhancement factors were predicted by the theory. Adult females had higher Clu values at high Ca values than males or immature females. Furthermore, at high Ca values, Clu in pregnant animals was twice as high as in the nonpregnant animals and four times as high as in the aged-matched males. The absolute values of Clu obtained experimentally in both pregnant and nonpregnant females exceeded the maximal predictions of the theory, using reasonable values of all of the parameters. Thus, according to current data on the physicochemical characteristics of the uptake system, the study demonstrates that some specialized process exists to facilitate hepatocellular uptake of fatty acid from albumin, and that it is potentiated by the female sex hormones.
Temporal-specific and spatial-specific patterns of neurotensin gene expression in the small bowel
Authors: Evers B. M. , Ehrenfried J. A. , Wang X. , Townsend C. M. , Thompson J. C.
Published: December 2017

Expression of the neurotensin/neuromedin N (NT/N) gene is developmentally regulated in a temporal- and spatial-specific pattern in the small bowel. The purpose of our study was to determine 1) whether the temporal expression of NT/N could be altered by ectopic placement of small bowel and 2) whether the spatial-specific expression of NT/N could be altered by different diets. We found that the relative temporal pattern of NT/N expression was unchanged in rat jejunal and ileal xenografts implanted into the flanks of athymic nude mice. To determine whether the spatial-specific pattern of NT/N expression could be altered by different luminal nutrients, 28-day-old rats were randomized to receive chow or chemically defined liquid diets for 60 days at which time the jejunoileum was divided into eight equal segments, and NT/N expression was analyzed. The normal pattern of increasing levels of NT/N mRNA along the jejunum-to-ileum axis was not altered by any of the liquid diets. In contrast to NT/N, we found that expression of sucrase-isomaltase varied greatly depending on both location and type of luminal nutrients. We conclude that the strict temporal- and spatial-specific pattern of NT/N expression is not affected by either location or luminal contents, thus suggesting an intrinsic program of NT/N gene expression. Furthermore, we speculate that the NT/N gene may provide a useful endocrine paradigm to investigate the factors regulating the establishment and maintenance of certain cell lineage-specific patterns along the cephalocaudal axis of the gut.
Cholinergic nerve-mediated excitation in the guinea pig choledochoduodenal junction activated by distension
Authors: Vogalis F. , Bywater R. R. , Taylor G. S.
Published: December 2017

The electrical basis of propulsive contractions in the guinea pig choledochoduodenal junction (CDJ), which are triggered by distension, was investigated using intracellular microelectrode recording techniques. The isolated CDJ was placed in a continuously perfused tissue chamber at 37 degrees C. Membrane potential was recorded from smooth muscle cells in either the ampulla or in the upper CDJ (upper junction) regions, which were immobilized by pinning. Distension of the upper junction (20-30 s) by increasing intraductal hydrostatic pressure (mean elevation: 2.0 +/- 0.3 kPa, n = 13) triggered "transient depolarizations" (TDs: < 5 mV in amplitude and 2-5 s in duration) and action potentials in the circular muscle layer of the ampulla. The frequency of TDs in the ampulla was increased from 2.2 +/- 0.2 to 15.9 +/- 2.2 min-1 (n = 13) during distension. Simultaneous impalements of cells in the longitudinal and circular muscle layers in the ampulla revealed that subthreshold TDs in the circular layer were associated with an increased rate of action potential discharge in the longitudinal layer. Atropine (Atr; 1.4 x 10(-6) M) and tetrodotoxin (TTX; 3.1 x 10(-6) M blocked the distension-evoked increase in TD frequency, without affecting the frequency of ongoing TDs. The sulfated octapeptide of cholecystokinin (1-5 x 10(-8) M) increased the amplitude of TDs recorded in the circular muscle layer of the ampulla and increased action potential discharge rate. In separate recordings, radial stretch of the ampulla region increased the rate of discharge of action potentials in the smooth muscle of the upper junction.(ABSTRACT TRUNCATED AT 250 WORDS)
Influence of acid and angiogenesis on kinetics of gastric ulcer healing in rats: interaction with indomethacin
Authors: Schmassmann A. , Tarnawski A. , Peskar B. M. , Varga L. , Flogerzi B. , Halter F.
Published: December 2017

Indomethacin delays healing of experimental gastric ulcers. We investigated whether inhibition of gastric acid secretion by omeprazole or stimulation of angiogenesis by basic fibroblast growth factor (bFGF) may reverse this delay. Rats with gastric ulcers induced by cryoprobe were treated subcutaneously with either placebo, indomethacin (2 x 0.5 mg/kg), bFGF (2 x 100 micrograms/kg), omeprazole (1 x 40 mumol/kg), indomethacin plus omeprazole, or indomethacin plus bFGF given daily for 8, 10, 15, and 22 days. Ulcer size, epithelial cell proliferation, angiogenesis, and maturation of granulation tissue were sequentially quantified. Omeprazole significantly accelerated ulcer healing in an early phase (days 3-8). In contrast, bFGF accelerated healing in a late phase (days 10-15). Indomethacin significantly delayed ulcer healing in late phase and decreased prostaglandin generation, cell proliferation, angiogenesis, and maturation of granulation tissue. Despite stimulation of angiogenesis, bFGF did not reverse indomethacin-induced delay in ulcer healing. In contrast, omeprazole reversed indomethacin-induced effects on angiogenesis, cell proliferation, maturation of granulation tissue, and ulcer healing rate.
Downregulation of E. coli-induced TNF-alpha expression in perfused liver by hypoxia-reoxygenation
Authors: Wibbenmeyer L. A. , Lechner A. J. , Munoz C. F. , Matuschak G. M.
Published: December 2017

We tested the hypothesis that reducing the hepatic O2 supply by 30 min of constant-flow hypoxia (PO2, approximately 45 Torr) following gram-negative bacteremia downregulates tumor necrosis factor-alpha (TNF-alpha) in buffer-perfused rat lives (total n = 44). Eight groups were studied after intraportal 10(9) viable E. coli serotype 055:B5 (EC) or 0.9% NaCl (NS) at t = 0:1) normoxic EC; 2) normoxic NS controls; 3) EC+hypoxia (H)-reoxygenation (R) in which H began 30 min after EC followed by 120 min of R; and 4) NS+H/R. To assess the role of cyclooxygenase vs. xanthine oxidase activation, the effects of 10(-5) M indomethacin (Indo) in 5) Indo+EC+H/R and 6) Indo+NS+H/R were compared with allopurinol (Allo) in 7) Allo+EC+H/R and 8) Allo+NS+H/R groups. Bacterial clearance, bioactive and antigenic TNF-alpha, and hepatic O2 uptake and performance were serially assessed, as was prostaglandin (PG) E2 at baseline and peak hypoxia in EC-challenged groups. Intrahepatic bacterial killing and TNF-alpha mRNA were determined at t = 180 min. Bioactive venous TNF-alpha did not increase in normoxic NS controls (6 +/- 3 U/ml at t = 180 min; mean +/- SE), whereas levels rose in NS4H/R by 180 min (111 +/- 34 U/ml; P < 0.01) without increases in TNF-alpha mRNA. In contrast, EC-induced increases in TNF-alpha transcripts during normoxia were attenuated in EC+H/R, as were protein levels (57 +/- 20 U/ml; P < 0.05), despite similar bacterial clearance. Neither Indo-mediated reductions in PGE2 nor allopurinol increased TNF-alpha after EC+H/R.(ABSTRACT TRUNCATED AT 250 WORDS)
Cholestasis is associated with preproenkephalin mRNA expression in the adult rat liver
Authors: Bergasa N. V. , Sabol S. L. , Young W. S. , Kleiner D. E. , Jones E. A.
Published: December 2017

Cholestatic liver disease is associated with clinical and experimental findings consistent with increased opioidergic neuromodulation, increased plasma total opioid activity, and elevated plasma enkephalin concentrations. In contrast to the normal adult rat liver, preproenkephalin mRNA was detected by Northern blotting in livers of adult rats with cholestasis due to bile duct resection and not in the sham-resected controls. Preprodynorphin mRNA was not detected in livers of either group, while preproopiomelanocortin mRNA was found in very low levels in both groups. Preproenkephalin mRNA was not expressed in the livers of rats with acute hepatocellular necrosis induced by thioacetamide. Hybridization histochemistry of cholestatic livers demonstrated the presence of preproenkephalin mRNA primarily over cells in the periportal areas, some of which appeared to be proliferating bile ductular cells. Immunohistochemical staining of cholestatic liver indicated the production of at least Met-enkephalin in association with preproenkephalin gene expression. These findings suggest that the liver itself, by synthesizing enkephalins, contributes directly to the abnormalities of the opioid system reported in cholestasis.
Relationship between surface electrogastrography and antropyloric pressures
Authors: Sun W. M. , Smout A. , Malbert C. , Edelbroek M. A. , Jones K. , Dent J. , Horowitz M.
Published: December 2017

The cutaneous electrogastrogram (EGG) and intraluminal antropyloroduodenal pressures were recorded in 12 healthy volunteers for 30-min periods during phase II of the interdigestive motor complex, during intraduodenal infusion of 10% triglyceride, and after intravenous erythromycin (3 mg/kg). During phase II, the frequency of the EGG was relatively constant in each individual, with a median frequency of 0.046 Hz [2.8 counts per minute (cpm)]. EGG frequency was greater (P < 0.05) than the median rate of antral pressure waves (1.8 cpm). The suppression of antral pressure waves (P < 0.05) and stimulation of isolated pyloric pressure waves (IPPWs) (P < 0.05) produced by triglyceride infusion were not associated with changes in EGG frequency compared with phase II. The frequency of the EGG and the rate of IPPWs were comparable. After erythromycin, EGG frequency was 0.03 Hz (1.8 cpm), less than during both phase II and triglyceride infusion (P < 0.05) and almost identical to the rate of antral pressure waves. Pressure waves were nearly always associated with an EGG signal. In contrast, the temporal relationship between the EGG signal and pressure waves was variable. During triglyceride infusion (r = 0.83, P < 0.001) and after erythromycin (r = 0.83, P < 0.001) there was a close (approximately 1:1) relationship between the rate of pressure waves and EGG frequency. However, there was no significant relationship (r = 0.32, not significant) between the number of pressure waves and EGG frequency frequency during pase II.(ABSTRACT TRUNCATED AT 250 WORDS)
Medullary TRH is involved in gastric protection induced by low dose of kainic acid into the raphe pallidus
Authors: Kaneko H. , Yang H. , Ohning G. , Tache Y.
Published: December 2017

The gastroprotective effect of kainic acid microinjected into the raphe pallidus (Rpa) at a dose subthreshold to increase acid secretion was investigated in urethan-anesthetized rats. Kainic acid (25 pg/30 nl) microinjected into the Rpa inhibited by 65.8% gastric damage induced by intragastric ethanol (60%). No protection was observed when kainic acid was injected outside of the Rpa. The cytoprotective effect was completely abolished by thyrotropin-releasing hormone (TRH) antibody microinjected bilaterally (1.3 micrograms/site) into the dorsal motor nucleus of the vagus (DMN), indomethacin (5 mg/kg ip), and atropine (0.3 mg/kg sc). Microinjection of TRH antibody outside of the DMN or of control antibody into the DMN did not modify the protective action induced by kainic acid into the Rpa. The TRH antibody microinjected alone into the DMN did not alter the severity of the ethanol-induced gastric lesions. These data indicate that excitation of Rpa neurons by a low dose of kainic acid results in cytoprotection against ethanol lesions. Furthermore, this cytoprotection occurs as a result of TRH action in the DMN and activation of muscarinic and prostaglandin pathways.
Disruption of colonic electrolyte transport in experimental colitis
Authors: Bell C. J. , Gall D. G. , Wallace J. L.
Published: December 2017

The time course of disturbances of distal colonic electrolyte transport during experimental colitis in rats was compared with changes in the severity of inflammation and epithelial disruption. Colitis was induced by intracolonic administration of trinitrobenzenesulfonic acid (TNBS). At time points from 1 day to 8 wk thereafter, Na+ and Cl- transport was studied under short-circuited conditions in Ussing chambers, three indexes of tissue inflammation were measured, and histology was performed. Net absorption of Na+ and Cl- was abolished at 1 and 4 days after induction of colitis, but recovered to control levels by 1 wk. All unidirectional electrolyte fluxes were elevated at 1 day and fell significantly, generally to control levels, by 4 days. The indexes of inflammation, tissue myeloperoxidase, and synthetic capacities for prostaglandin E2 and leukotriene B4 were all significantly elevated from 1 day to 2 wk post-TNBS. At 1 and 4 days, there was widespread epithelial necrosis, and reepithelialization was consistently seen by 2 wk. In additional studies, 2 wk post-TNBS, the short-circuit current response to 3-isobutyl-1-methylxanthine was reduced compared with controls. These data suggest that abolition of electrolyte absorption early in this experimental colitis was largely attributable to epithelial damage. Despite demonstrable tissue inflammation 2 wk post-TNBS, basal electrolyte transport was not impaired, while the colitic epithelium was hyporesponsive to a Cl- secretagogue. The data also suggest that gross barrier function was restored prior to reepithelialization.
Regulation and localization of the insulin-like growth factor system in small bowel during altered nutrient status
Authors: Winesett D. E. , Ulshen M. H. , Hoyt E. C. , Mohapatra N. K. , Fuller C. R. , Lund P. K.
Published: December 2017

Insulin-like growth factor-I (IGF-I) may regulate small bowel growth. Analyses here in ad libitum-fed, fasted, and refed rats demonstrate that during fasting and refeeding changes in jejunal mass correlate with changes in serum IGF-I and jejunal IGF-I mRNAs. These data indicate that circulating and locally expressed IGF-I contribute to nutrient regulation of jejunal mass. During refeeding, jejunal IGF binding protein 3 (IGFBP-3) mRNA abundance was reduced relative to that of IGF-I, possibly amplifying enterotrophic actions of IGF-I. Localization of IGFBP-3 to subepithelial cells in lamina propria of jejunum indicates that IGFBP-3 derived from lamina propria may modulate IGF-I action on adjacent epithelium. Ileum differed from jejunum in that refeeding did not increase bowel mass or IGF-I mRNA to ad libitum values. Differences in exposure to luminal nutrient may underlie distinct responses of the two segments. Rats fed elemental diet intravenously showed reduced jejunal mass but not reduced jejunal IGF-I mRNA compared with rats fed oral elemental diet. Elemental nutrient given intravenously or orally therefore does not differ in effects on jejunal IGF-I expression. Complex luminal nutrient may, however, regulate jejunal IGF-I expression.
Prolonged ambulatory canine colonic motility
Authors: Scott S. M. , Pilot M. A. , Barnett T. G. , Williams N. S.
Published: December 2017

Canine gastrointestinal motility is studied at present in animals confined to a small cage or sling. The aims of this study were to record colonic activity over a 24-h period in eight dogs by an ambulatory method. Motility signals from implanted strain gauges were processed and stored via a portable battery-operated amplifier and digital recorder housed in a jacket. Ambulant interdigestive activity was the same as observed in laboratory experiments, with migrating colonic motor complexes (CMCs) and infrequent giant contractions (GCs). Feeding caused a multiphasic alteration in motility for 582.1 +/- 18.1 min (mean +/- SE). There were four distinct phases. During the "early" (0-2 h) postprandial period, phase 1 (mean duration: 55.1 +/- 4.0 min), which was distinguished by CMCs of high frequency and elevated amplitude in the proximal colon, and phase 2 (78.2 +/- 6.2 min), which had CMC characteristics similar to those in the interdigestive period, occurred. Phase 3 (218.8 +/- 13.6 min), a further period of increased motility, and phase 4 (339.1 +/- 14.0 min), characterized by low-amplitude long-duration CMCs, occurred during the "late" (2 h onward) postprandial response. With the exception of phase 3, postprandial phases were not always present following food intake, and their expression was markedly influenced by variations in meal time and by defecation immediately following feeding. Spontaneous defecation was characterized by a variety of motor profiles, with a GC accompanying two-thirds of episodes. We conclude that a more complete picture of canine colonic motility has been documented because of the development of the ambulatory system.
Distension-induced electrogenic Cl- secretion is mediated via VIP-ergic neurons in rat rectal colon
Authors: Schulzke J. D. , Riecken E. O. , Fromm M.
Published: December 2017

Distension of rat rectal colon causes electrogenic Cl- secretion via the plexus submucosus Meissner. This study aimed to identify the neurotransmitter(s) of this reflex pathway. Distension was applied to partially stripped rat rectal colon in Ussing chambers. Baseline short-circuit current (Isc) increased and then slowly declined again within 30 min. The increase in Isc 10 min after distension (delta Isc10) was 1.8 +/- 0.3 mumol.h-1.cm-2. Atropine (1 microM) did not alter delta Isc10. Thus cholinergic neurons with muscarinic synapses were not involved. Tissues were then desensitized to vasoactive intestinal peptide (VIP) or substance P. This required continuous infusion of VIP or substance P into the chamber; otherwise, desensitization was only temporary due to rapid degradation of VIP or substance P. During substance P desensitization, distension still induced a secretory response (delta Isc10 not significant vs. control), whereas during VIP desensitization distension no longer had an effect. Furthermore, a polyclonal anti-VIP antiserum blocked 81% and the VIP antagonist [p-Cl-D-Phe6,Leu17]VIP blocked 89% of the distension-induced delta Isc10, supporting the results of the desensitization experiments. To localize the site of VIP action, tetrodotoxin (TTX) was used. The TTX effect on Isc during VIP stimulation was not different from its effect on baseline Isc. This is in accord with the concept that the VIP receptors are mainly located on the enterocytes. We conclude that VIP, but not substance P or acetylcholine (via muscarinic receptors), acts as a neurotransmitter in the distension-induced reflex pathway, causing Cl- secretion in rat rectal colon.
Ryanodine-induced calcium release from hepatic microsomes and permeabilized hepatocytes
Authors: Lilly L. B. , Gollan J. L.
Published: December 2017

Inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] is a second messenger that releases Ca2+ from hepatocyte microsomes. The toxic alkaloid ryanodine modulates Ca2+ release via a receptor (RyR) identified in a variety of cell systems, but its regulation and functional significance in liver are undefined. Similarly, the role in hepatocyte Ca2+ regulation of adenosine 5'-cyclic diphosphate-ribose (cADPR), which is the putative endogenous ligand for RyR in other cell systems, has not been defined. Utilizing microsomes and permeabilized cells, we have investigated Ca2+ regulation in hepatocytes and, in particular, effects of ryanodine, cADPR, and other putative modulators on Ca2+ release and compared these with Ins(1,4,5)P3-induced Ca2+ release. Ryanodine at > or = 50 microM released 20% of microsomal Ca2+, and, in contrast to Ins(1,4,5)P3, no potentiation was observed with guanosine 5'-triphosphate and polyethylene glycol. Ins(1,4,5)P3-induced Ca2+ release was demonstrable after maximal ryanodine-induced Ca2+ release, suggesting that distinct Ca2+ stores are involved. cADPR (5 microM) did not induce Ca2+ release, alone or in combination with calmodulin or hepatic cytosol, nor did it influence ryanodine-induced release, in microsomes or permeabilized hepatocytes (in which ryanodine released 25% of the sequestered Ca2+). Ryanodine-induced Ca2+ release in microsomes was not influenced by 20 mM caffeine, which itself did not mobilize Ca2+, but was prevented by 500 microM tetracaine, which was shown to induce Ca2+ release. We conclude that ryanodine is capable of mobilizing Ca2+ in the hepatocyte from microsomal stores that are distinct from those that can be regulated by Ins(1,4,5)P3 but that cADPR has no such effect. These data suggest that cADPR does not serve as the endogenous ligand for RyR in liver cells or that the site of action of ryanodine in hepatocyte microsomes is distinct from that in other cell types.
Gastric emptying of oil and aqueous meal components in pancreatic insufficiency: effects of posture and on appetite
Authors: Carney B. I. , Jones K. L. , Horowitz M. , Sun W. M. , Penagini R. , Meyer J. H.
Published: December 2017

The aims of this study were to evaluate the effects of posture on gastric emptying, intragastric distribution, and satiation after a meal containing oil and aqueous phases in patients with exocrine pancreatic insufficiency. Five patients with cystic fibrosis (CF) consumed 60 ml 99mTc-labeled (V)-thiocyanate olive oil and 290 ml 113mIn-labeled diethylenetriaminepentaacetic acid soup while sitting and while lying in the left lateral decubitus position. Hunger and fullness before and after the meal were recorded. Results were compared with those obtained in 11 normal volunteers. In both postures emptying of oil was faster (P < 0.01) in CF patients. Emptying of the aqueous phase was faster (P < 0.01) in CF patients in the decubitus position. In normal subjects there was no overall difference in emptying of oil between the two postures, whereas emptying of the aqueous phase was delayed (P < 0.01) in the decubitus position. In CF patients emptying of oil was faster (P < 0.01) in the decubitus position, and emptying of the aqueous phase was only slightly faster (P < 0.05) in the sitting position. For both postures there was greater retention (P < 0.05) of oil in the proximal stomach in normal subjects than CF patients. Hunger decreased (P < 0.05) after the meal in the control subjects, but there was no change in CF patients. These results indicate that in CF patients with pancreatic exocrine insufficiency 1) gastric emptying of nonhomogenized fat is faster than normal, 2) gravity affects gastric emptying of oil, and 3) effects of a fatty meal on hunger are reduced.
Dual effect of deferoxamine on free radical formation and reoxygenation injury in isolated hepatocytes
Authors: Caraceni P. , Van Thiel D. H. , Borle A. B.
Published: December 2017

The effects of low concentrations (10 and 100 microM) and high concentrations (1, 10, and 20 mM) of deferoxamine (DFO) on superoxide (O2-.) formation, lipid peroxidation, and cell injury were studied in freshly isolated perfused rat hepatocytes during a 2-h reoxygenation period after 2.5 h of anoxia. O2-. production was measured by lucigenin-enhanced chemiluminescence, lipid peroxidation by malondialdehyde (MDA) formation, and cell injury by lactate dehydrogenase (LDH) release. On reoxygenation and in the absence of DFO, O2-. generation increased 11-fold, MDA increased 3.7-fold, and LDH release practically doubled. Low concentrations of DFO had no effect on O2-. generation but decreased MDA and LDH release from 44 to 75%. High concentrations of DFO significantly depressed O2-. formation, with very little additional effect on MDA or LDH release. These experiments illustrate in a biological system the dual effect of DFO: 1) at low Concentrations, DFO acts as a specific iron chelator and inhibits lipid peroxidation and cell injury without preventing O2-. formation, and 2) at high concentrations, DFO acts as a nonspecific scavenger of oxygen free radicals such as O2-.
Mechanism of action of somatostatin on the canine ileal circular muscle
Authors: Jimenez M. , Vergara P. , Christinck F. , Daniel E. E.
Published: December 2017

The aim of this study was to investigate the mechanism of action of somatostatin on the circular muscle of the isolated canine ileum using the microelectrode technique. The membrane potential from circular muscle cells was recorded in two preparations: 1) whole thickness circular and longitudinal muscle (with intact myenteric and deep muscular plexuses, n = 13) and 2) isolated circular muscle (with only deep muscular plexus, n = 9). In this preparation, inhibitory junction potentials (IJPs), elicited after field stimulation, are mediated by a nitric oxide-related (NO-R) compound. Somatostatin (10(-6) M) transiently (2-5 min) depolarized the circular muscle cells in both whole thickness (3.6 +/- 1.0 mV, P < 0.01) and isolated circular muscle preparations (8.0 +/- 0.8 mV, P < 0.01). Somatostatin did not reduce either the amplitude or duration of the IJP in the isolated circular muscle but reduced slow-wave amplitude. In contrast, a reduction (20-50%) in the amplitude of the IJP was observed in the whole thickness preparation, and there was little effect on slow-wave amplitude. Somatostatin did not affect the induced slow wave observed in the whole thickness preparation after field stimulation. Apamin significantly reduced the amplitude of the IJP in both preparations. Somatostatin (10(-6) M) did not modify the apamin-resistant IJP. A reduction in the slow-wave amplitude was observed in the isolated circular muscle preparation.(ABSTRACT TRUNCATED AT 250 WORDS)
Differential projection of cholinergic and nitroxidergic neurons in the myenteric plexus of guinea pig stomach
Authors: Schemann M. , Schaaf C.
Published: December 2017

The aim of this study was to investigate the organization of myenteric circuits in the guinea pig stomach. Intracellular neurobiotin injections followed by choline acetyltransferase (ChAT) immunohistochemistry and NADPH-diaphorase reaction were used to identify projections of cholinergic and nitroxidergic neurons. Neurons were classified as motor neurons based on varicose endings in the muscle or the occurrence of retraction bulbs, as nonmotor neurons if varicose endings terminated onto other ganglion cells, or as multitargeted neurons. ChAT-positive cells are composed of 64% motor, 27% nonmotor, and 9% multitargeted neurons. The percentages for NADPH-reactive motor, nonmotor, and multitargeted neurons were 57, 39, and 4%, respectively. The majority of ChAT-positive motor (81%) and nonmotor neurons (85%) had ascending projections. In contrast, the majority of NADPH-reactive motor (86%) and nonmotor neurons (86%) had descending projections. Cell bodies of ascending neurons were smaller in size than the descending neurons. The results indicate that ChAT- and NADPH-neurons in the stomach have preferred projections, the former being primarily ascending, the latter mainly descending neurons. This suggests the existence of a basic circuit for polarized reflexes in the myenteric plexus of the stomach, which might mediate descending relaxation and ascending excitation.
Effects of nitric oxide inhibition on duodenal function in rat: involvement of neural mechanisms
Authors: Hallgren A. , Flemstrom G. , Sababi M. , Nylander O.
Published: December 2017

This study examines the integrative response of several duodenal functions to nitric oxide synthase inhibition. Effects of the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) were studied in anesthetized rats, using in situ duodenal perfusion. L-NAME increased bicarbonate secretion, permeability, and fluid secretion and induced motility. Injection of L-arginine abolished L-NAME-induced motility and lowered the secretion of bicarbonate and fluid. Pretreatment with the nicotinic receptor antagonist hexamethonium prevented the rise in bicarbonate secretion and motility in response to L-NAME but did not affect the increase in mucosal permeability. Atropine diminished the L-NAME-induced increases in permeability, motility, and fluid secretion. The adrenolytic drug guanethidine did not alter the responses to the inhibitor. These results suggest that nitric oxide inhibits duodenal motility and bicarbonate secretion by suppressing a stimulatory, nicotinic receptor-dependent, neural mechanism. The L-NAME-induced contractions involve both a cholinergic, atropine-sensitive pathway and nonadrenergic, noncholinergic neural transmission. Muscarinic receptors also mediate part of the L-NAME-induced increases in mucosal permeability and fluid secretion.