bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies in vivo and in vitro on effects of PGE2 on colonic motility in rabbits
Authors: Burakoff R. , Percy W. H.
Published: December 2017

Prostaglandins (PG) of the E series are synthesized throughout the gastrointestinal tract, and their elevated levels have been reported in many diarrheal states, including inflammatory bowel disease. It is already known that PGE2 has region-specific and muscle layer-specific effects in different areas of the intestine. The aim of this study was to evaluate possible dose-related motor effects of PGE2 on rabbit proximal and distal colon both in vivo and in vitro. We found that, in the proximal colon in vivo, PGE2 caused inhibition of myoelectric and mechanical activity at low doses but at higher doses caused marked excitation. Under the same experimental conditions, PGE2 caused only excitation in the distal colon, a phenomenon associated with an increase in antegrade contractions and diarrhea. In vitro, PGE2 caused excitation of both proximal and distal colonic longitudinal muscle and relaxation of the circular muscle. Its actions, however, were much more pronounced in the distal region. It is concluded that PGE2 has profound effects on colonic motility that are concentration dependent and that differ with the region of the colon under study. Furthermore, the evidence also suggests that elevated PGE2 levels in disease states may play a significant role in abnormal colonic motility and may facilitate the onset of diarrhea.
TRH analogue microinjected into specific medullary nuclei stimulates gastric serotonin secretion in rats
Authors: Yang H. , Stephens R. L. , Tache Y.
Published: December 2017

Brain nuclei involved in vagal release of gastric serotonin (5-HT) were investigated in urethan-anesthetized rats acutely implanted with gastric cannula. Gastric secretions were collected every 10-15 min for 2 h, and measurement of serotonin 5-HT was performed by high-performance liquid chromatography (HPLC) with electrochemical detection and that of acid by titration. The stable thyrotropin-releasing hormone (TRH) analogue, RX 77368, microinjected into the dorsal vagal complex (DVC) (1.5-77 pmol/50 nl) induced a dose-related and long-lasting increase in gastric 5-HT and acid output. TRH (276 pmol) microinjected into the DVC also stimulated gastric 5-HT secretion. TRH action was abolished by vagotomy. RX 77368 (77 pmol) increased 5-HT release after microinjection into the raphe obscurus, raphe pallidus, and nucleus ambiguus, although the responses were significantly lower compared with that induced by DVC microinjection. No changes in gastric 5-HT release were observed when the peptide was microinjected into the lateral hypothalamus, hypoglossal, paramedian reticular, inferior olive, lateral paragigantocellular or spinal trigeminal nucleus. The potent gastric 5-HT release induced by TRH or TRH analogue into the DVC added to the presence of TRH receptors and TRH-LI nerve terminals in the DVC suggest a role of medullary TRH in the vagal regulation of gastric 5-HT release.
Role of polyamines in glucocorticoid effects on pancreatic acinar AR42J cell growth and differentiation
Authors: Logsdon C. D. , Alves F. , Rosewicz S.
Published: December 2017

We previously found that glucocorticoids inhibit growth and increase differentiation in rat pancreatic acinar AR42J cells. In the current study, we examined the role of polyamines in these effects. Treatment of AR42J cells with the ornithine decarboxylase (ODC) inhibitor difluoromethylornithine (DFMO) inhibited DNA synthesis. Thus polyamines are required for AR42J cell growth. However, we have previously shown that dexamethasone (Dex) increased AR42J cell ODC activity and mRNA levels. In the current study, we found that Dex treatment increased cellular putrescine levels. These increases in ODC and putrescine occurred during Dex-induced inhibition of DNA synthesis. Therefore, in AR42J cells, ODC activity and polyamine levels are not strictly growth related. To examine the requirement for glucocorticoid induction of ODC activity in glucocorticoid stimulation of differentiation, we examined the effects of DFMO on amylase gene expression and cholecystokinin binding. DFMO reduced cell amylase content while having little effect on mRNA levels in both Dex-treated and untreated cells. In contrast, DFMO had little effect on control CCK binding but inhibited the Dex-induced increase. Thus polyamines are necessary for growth and glucocorticoid-induced differentiation of AR42J cells; however, effects of glucocorticoids on AR42J cell growth and differentiation are not mediated by effects on ODC.
Postnatal changes in the substance P receptor on rabbit gastric smooth muscle
Authors: Hyman P. E. , Kimura S. , Tomomasa T. , Yuan Q. X. , Snape W. J. , McRoberts J. A.
Published: December 2017

We used radioligand binding to tissue homogenates and isometric contraction of muscle strips to characterize the substance P (SP) receptor on gastric smooth muscle from 1- (newborn) and 7-day-old and 4- and 11-wk-old (weanling) rabbits. Scatchard analysis for newborns was curvilinear, suggesting the presence of multiple binding sites. In newborns the dissociation constant (Kd) of high-affinity binding site was 2.2 +/- 0.3 nM, and the maximum binding (Bmax) was 0.57 +/- 0.06 pmol/mg DNA. The number of high-affinity binding sites decreased with age, disappearing by 11 wk. The Kd for the low-affinity site was more than two orders of magnitude greater than that of the high-affinity site. In competitive binding studies with [3H]SP, the order of potency for the neurokinins was SP much greater than neurokinin A (NKA) greater than neurokinin B (NKB), suggesting that the high-affinity binding sites were NK-1 receptors. [125I]NKA is also bound to newborn tissue homogenate with high affinity. With [125I]NKA the order was NKA greater than SP greater than NKB, suggesting that NK-2 receptors were also present. In contraction studies, atropine and tetrodotoxin had no effect on tachykinin-stimulated contraction, suggesting solely myogenic tachykinin effects on this tissue. In newborn rabbits, the potency and efficacy of SP and NKA were similar. The half-maximal effective dose (ED50) of SP was nearly two orders of magnitude less in newborn rabbits than in weanlings; the potency of NKA did not change.(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of opioid receptors on smooth muscle cells from guinea pig stomach
Authors: Zhang L. , Gu Z. F. , Pradhan T. , Jensen R. T. , Maton P. N.
Published: December 2017

On the basis of opioid-stimulated contraction of dispersed gastric smooth muscle cells it has been suggested that these cells possess opioid receptors of three subtypes: kappa (kappa), mu (mu), and delta (delta). We have used selective peptidase-resistant radioligands, agonists and antagonists, to examine receptor subtypes on dispersed gastric smooth muscle cells from guinea pigs prepared by collagenase digestion. The kappa-agonist U-50488H, the mu-agonist [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAGO), and the delta-agonist [D-Pen2,Pen5]enkephalin (DPDPE) each caused muscle contraction. The concentrations required to caused half-maximal contraction were U50488H (6 pM) greater than DAGO (13 pM) greater than DPDPE (6 nM). The abilities of these agonists to inhibit binding of [3H]U-69593 (kappa-preferring) by 50% were U50488H (43 nM) greater than DAGO (43 microM) greater than DPDPE (200 microM). Their abilities to inhibit binding of [3H]naloxone (mu-preferring) by 50% were DAGO (0.2 microM) greater than U50488H (10 microM) greater than DPDPE (greater than 100 microM). No binding could be detected with the delta-selective ligand [3H]DPDPE. The kappa-preferring antagonist Mr2266 (10 nM) preferentially inhibited contraction stimulated by the kappa-agonist U50488H, and naltrexone (10 nM) (mu-selective antagonist) preferentially inhibited contraction stimulated by the mu-agonist DAGO. ICI 174864 (200 microM; delta-selective antagonist) had no effect on contraction stimulated by mu-, kappa-, or delta-agonists. Contraction stimulated by the delta-agonist DPDPE was inhibited by both kappa- and mu-receptor antagonists. Studies on the effect of the antagonists on binding of [3H]naloxone and [3H]U69593 also provided evidence for kappa- and mu-sites but nor for delta-sites.(ABSTRACT TRUNCATED AT 250 WORDS)
Abdominal surgery-induced delayed gastric emptying in rats: role of CRF and sensory neurons
Authors: Barquist E. , Zinner M. , Rivier J. , Tache Y.
Published: December 2017

The role of peripheral corticotropin-releasing factor (CRF) and afferent pathways in mediating abdominal surgery-induced delayed gastric emptying was investigated using an intravenous injection of the competitive CRF antagonist alpha-helical CRF9-41 and capsaicin pretreatment in adult fasted rats. Gastric emptying of a non-caloric solution was measured by the phenol red method. Intravenous CRF (0.13 nmol) inhibited by 65% gastric emptying. CRF effect was completely reversed by simultaneous intravenous injection of alpha-helical CRF9-41 (13 nmol). Abdominal surgery under enflurane anesthesia inhibited gastric emptying by 60% measured 3 h postoperatively. Enflurane anesthesia alone had no effect on gastric emptying 3 h after exposure. Abdominal surgery-induced delay of gastric emptying was reversed by 46, 60, and 100% by capsaicin pretreatment (125 mg/kg, -3 wk), intravenous injection of alpha-helical CRF9-41 (13 nmol), and combined pretreatments with capsaicin and CRF antagonist, respectively. Capsaicin and alpha-helical CRF9-41 given alone or in combination did not influence gastric emptying. These results indicate that peripheral CRF receptors along with capsaicin-sensitive afferent neurons contribute to somatovisceral stress (abdominal surgery)-induced delayed gastric emptying.
Gastric inhibitory polypeptide stimulates pancreatic lipase and colipase synthesis in rats
Authors: Duan R. D. , Erlanson-Albertsson C.
Published: December 2017

Effects of short-term infusion and long-term injection of gastric inhibitory polypeptide (GIP) on changes in pancreatic lipase and colipase contents in rats were studied, and mRNAs encoding for lipase and colipase were determined by Northern blot hybridization with specific cDNA probes. GIP infused at a dose of 3 micrograms/h for 24 h significantly increased the pancreatic lipase content by 34% (P less than 0.05) but had no significant effect on colipase and amylase contents. No change in mRNAs encoding for these proteins was found after infusion of GIP for 24 h. Injection of GIP (5-60 micrograms/kg) three times a day for 5 days dose dependently increased the contents of lipase and colipase, with the increase in colipase being more prominent. Injection of GIP for 5 days at a dose of 30 micrograms.kg-1.day-1 increased colipase and lipase contents by 52 and 25%, and their corresponding mRNAs by 60 and 160%, respectively. The amylase mRNA was not changed by injection of GIP. It is concluded that GIP has a specific stimulatory effect on the synthesis of pancreatic lipase and colipase at both pretranslational and translational levels.
Mechanism of regulation of calcium-pumping activity in chick intestine
Authors: Takito J. , Shinki T. , Tanaka H. , Suda T.
Published: December 2017

The role of the calcium pump in the stimulation of intestinal calcium transport activity by 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] was examined in chicks. The in situ intestinal absorption of calcium increased approximately threefold in the duodenum, jejunum, and ileum 6 h after a single injection of 625 ng of 1 alpha,25(OH)2D3 into vitamin D-deficient chicks. The same treatment also increased approximately twofold the rate of ATP-dependent calcium uptake by the basolateral membrane vesicles (BL) isolated from those three sites. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that a Mg(2+)-dependent calcium-stimulated phosphorylated intermediate with an apparent molecular mass of 105 kDa appeared in the BL. The 1 alpha,25(OH)2D3 treatment gave no change in the levels of the intermediate. Pretreatment of the BL with alkaline phosphatase decreased the calcium uptake by the BL isolated from 1 alpha,25(OH)2D3-treated chicks, but it had little effect on the uptake by the BL from vitamin D-deficient chicks. These results suggest that at an early stage of the 1 alpha,25(OH)2D3-induced intestinal calcium transport process, the vitamin regulates the calcium-pumping activity of chick intestinal BL by phosphorylation and dephosphorylation but not by a stoichiometric change in the pump.
Ultrasonic crystal measurement of blood volume changes in liver and spleen
Authors: Greenway C. V. , Rothe C. F.
Published: December 2017

Two methods of measurement of splenic and hepatic vascular capacitance responses were compared in cats anesthetized with pentobarbital. For the spleen, measurements using ultrasonic crystals were compared with recordings of splenic weight. The cube of the relative change in thickness at one point on the longitudinal axis of the spleen was closely correlated with the overall change in spleen weight. For the liver, measurements by ultrasonic crystals were compared with plethysmographic recordings of liver volume. Individual measurements of cubed relative thickness did not correlate well with plethysmographic volume, and two sets of crystals on the same liver lobe gave different estimates of relative liver volume. However, averaged measurements for a group of animals showed similar means by the two methods. We conclude that ultrasonic crystals, when appropriately attached, can reliably monitor changes in splenic volume, but that for the liver, the variability in thickness responses at different sites on different livers is high. Unless a large number of observations are made, the results will be unreliable.
Regulation of brush-border enzyme activities and enterocyte migration rates in mouse small intestine
Authors: Ferraris R. P. , Villenas S. A. , Diamond J.
Published: December 2017

We adapted the Weiser method, previously used to fractionate enterocytes of rat and rabbit intestine, to the much smaller intestine of mice. By histological, morphometric, enzymatic, histochemical, and immunocytochemical evidence, the method succeeded in removing mouse enterocytes sequentially along the crypt-villus axis while preserving cell viability and minimizing mixing among cell fractions. Activities of three brush-border enzymes [alkaline phosphatase (AP), sucrase, and gamma-glutamyl transpeptidase (GGP)] varied simultaneously with dietary substrate level, intestinal region, and position along the crypt-villus axis. All three enzymes proved to be stimulated by dietary substrate: sucrase by dietary sucrose, AP and GGP by dietary protein. We also studied cell migration rates and life-times by autoradiography and by our modified Weiser method. By both methods, injected [3H]thymidine after short times was virtually confined to crypt cells, whereas after 40-48 h it was distributed from the crypt over the whole villus except for the villus tip. Villus height decreased twofold from duodenum to ileum, parallel to the regional decrease in cell migration rates because the cell lifetime of 68 h was independent of region. When we varied dietary carbohydrate and protein levels reciprocally while maintaining protein above the maintenance level, both cell migration rate and cell lifetime proved independent of diet.
Hepatic uptake of 3,5,3'-triiodothyronine: electrochemical driving forces
Authors: Weisiger R. A. , Luxon B. A. , Cavalieri R. R.
Published: December 2017

We used the multiple indicator dilution technique to assess the electrochemical forces driving uptake of 3,5,3'-triiodo-L-thyronine (T3) across the basolateral plasma membrane in the single-pass perfused rat liver. With the use of 4 g/dl albumin solutions, the influx and efflux clearances were 0.020 +/- 0.005 and 0.0049 +/- 0.0017 (SE) ml.s-1.g liver-1, respectively, indicating that the total T3 concentration at equilibrium should be about four times greater in cytoplasm than in plasma. However, when the influx and efflux clearances were divided by the unbound (free) T3 concentration in the perfusate and cytosol, they were not different (3.76 +/- 0.26 vs. 4.30 +/- 0.38 ml.s-1.g liver-1), indicating that the uptake process does not generate a gradient of unbound T3 across the plasma membrane. To further test whether T3 uptake is driven by the electrical potential difference across the plasma membrane, liver cells were depolarized by isosmotic replacement of perfusate chloride with gluconate. There was no effect on uptake or efflux. To test whether uptake is coupled to influx of sodium, perfusate sodium was replaced with choline. Although there was a modest decline in both the influx and efflux clearances, there was no change in their ratio, as would be expected for sodium-coupled active transport. These results indicate that uptake of T3 across the basolateral hepatocyte membrane occurs by passive diffusion. We found no evidence to support concentrative, active transport by either electrogenic or sodium-coupled mechanisms.
Role of chloride ions in lower esophageal sphincter tone and relaxation
Authors: Saha J. K. , Sengupta J. N. , Goyal R. K.
Published: December 2017

Studies were performed in strips of opossum lower esophageal sphincter (LES) muscle in vitro. External Cl(-)-free Krebs solution (0[Cl-]o) inhibited resting tone. Treatment with the Cl- channel blocker diphenylamine-2-carboxylate (DPC, 0.3-100 microM) caused a concentration-dependent relaxation of LES muscle, as did treatment with 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS, 1 microM-3 mM), a Cl(-)-HCO3- exchange blocker, and bumetanide (0.3-100 microM), a blocker of the Na(+)-K(+)-2Cl- cotransport. DIDS and bumetanide are also known to cause Cl- channel block. The calculated pD2 and Emax values for DPC, DIDS, and bumetanide were 5.24 +/- 0.28 (n = 5), 3.38 +/- 0.16 (n = 5), and 4.49 +/- 0.23 M (n = 5), and 78.80 +/- 5.38, 74.80 +/- 6.54, and 83.70 +/- 10.20%, respectively. The neuronal Cl- channel activators gamma-aminobutyric acid and glycine had no effect on the resting tone. DPC, DIDS, and bumetanide appear to have acted directly on smooth muscle rather than indirectly through the release of inhibitory neurotransmitters because LES relaxation by these agents was not influenced by tetrodotoxin (10 microM), which blocks action potentials in nerves, or by omega-conotoxin (1 microM), which inhibits the release of neurotransmitters from nerve terminals. LES muscle relaxed by exposure to 0[Cl-]o, DPC, DIDS, and bumetanide contracted with the addition of carbachol (30 microM); muscle so treated was resistant to the inhibitory neurotransmitter-mediated relaxation ordinarily induced by electrical field stimulation (EFS, 0.12-32 Hz). This effect was not nonselective, as the EFS-resistant muscle relaxed fully with isoproterenol (0.1-100 microM). HCO(3-)-free Krebs in the nominal absence of CO2 did not affect the resting tone and its relaxation. The Ca2+ channel blocker nifedipine decreased resting tone but did not antagonize the relaxation of carbachol-contracted muscle induced by either EFS or isoproterenol. These studies suggest that Cl- may play an important role in LES tone and relaxation due to inhibitory neurotransmitter released from intramural nerves.
Neurohormonal mechanism of pancreatic exocrine secretion stimulated by sodium oleate and L-tryptophan in dogs
Authors: Jo Y. H. , Lee Y. L. , Lee K. Y. , Chang T. M. , Chey W. Y.
Published: December 2017

In the present investigation, we have studied the effect of atropine on the pancreatic secretion stimulated by intraduodenal administration of either sodium oleate or exogenous cholecystokinin (CCK). In four dogs prepared with gastric and Thomas duodenal cannulas, pancreatic juice was collected for measurement of volume, bicarbonate, and protein output, and peripheral venous blood samples were obtained for radioimmunoassay of both secretin and CCK. Volume, bicarbonate, and protein output of the pancreatic juice increased significantly in response to sodium oleate (1-4 mmol/h) in a dose-dependent manner. The increase in pancreatic secretion paralleled the increments in both plasma CCK and secretin. Atropine given intravenously suppressed completely both pancreatic secretion and release of CCK stimulated by sodium oleate, whereas the release of secretin was not affected. Pancreatic secretion was significantly increased in a dose-dependent manner by exogenous CCK octapeptide (CCK-8) at 16, 32, and 64 micrograms (14, 28, and 56 pmol).kg-1.h-1. Atropine inhibited protein output only partially, but it did not influence bicarbonate output. In five additional dogs, the effect of atropine on L-tryptophan-stimulated pancreatic secretion was studied. Interestingly, atropine failed to influence the CCK release and pancreatic secretion of volume and bicarbonate, except for protein secretion, which was significantly inhibited. It was shown previously that atropine inhibited significantly the pancreatic secretion of bicarbonate stimulated by secretin in physiological doses. Thus we conclude that the inhibition by atropine of the pancreatic exocrine secretion stimulated by sodium oleate is mediated by both suppression of CCK release and inhibition of action of secretin on the exocrine pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of erythromycin in the dog upper gastrointestinal tract
Authors: Holle G. E. , Steinbach E. , Forth W.
Published: December 2017

The effects of erythromycin on motor and electrical behavior of the antrum, pylorus, and duodenum were determined in chronically instrumented, awake dogs. Erythromycin infusion resulted in an abrupt, powerful increase in motility. The motility index increased 18-fold in the antrum, 15-fold in the pylorus, and 8-fold in the duodenum. Bradyarrhythmia with a 30% decrease in slow-wave frequency occurred in all animals. Retrograde giant contractions in association with retching and vomiting occurred in 88% of the dogs. Neostigmine was less potent than erythromycin in increasing motility. Hexamethonium given intra-arterially during erythromycin infusion abolished motility for 7.2 +/- 2.9 min and intra-arterial atropine did so for 51 +/- 25 min. Hexamethonium or atropine restored the electrical slow-wave frequency. The results provide evidence that erythromycin action involves cholinergic pathways including ganglionic transmission.
Role of EDRF in splanchnic blood flow of normal and chronic portal hypertensive rats
Authors: Iwata F. , Joh T. , Kawai T. , Itoh M.
Published: December 2017

The role of endogenous endothelium-derived relaxing factor (EDRF) in splanchnic blood flow was assessed in normal and portal vein-stenosed rats (PSRs). Specific and maximal inhibition of EDRF was achieved by intravenous administration of NG-nitro-L-arginine (L-NOARG) as a 1.75 mumol/kg bolus, followed by constant infusion of 1.75 mumol/kg for 20 min. Pretreatment with L-arginine (175 mumol/kg iv) completely blocked both hypertension and the reduction in blood flow induced by L-NOARG. Pretreatment with D-arginine (175 mumol/kg iv) and prazosin (500 micrograms/kg iv) did not attenuate the pressor effect of L-NOARG. These results indicate that L-NOARG selectively blocks EDRF. The blood flow to the stomach, duodenum, jejunum, ileum, cecum, and colon in control rats was 81.1 +/- 8.7, 199.1 +/- 21.9, 153.3 +/- 20.0, 68.6 +/- 10.6, 79.4 +/- 11.8, and 59.3 +/- 7.8 ml.min-1.100 g-1, respectively, and in PSRs was 141.4 +/- 10.8, 244.0 +/- 10.4, 208.3 +/- 9.8, 126.8 +/- 13.0, 166.9 +/- 16.5, and 94.8 +/- 4.7 ml.min-1.100 g-1, respectively. Blood flow was measured using the radioactive microsphere method. L-NOARG significantly reduced blood flow to the stomach, duodenum, jejunum, ileum, cecum, and colon in control rats by 47, 44, 48, 55, 40, and 41%, respectively, and in PSRs by 30, 27, 36, 33, 28, and 23%, respectively. The magnitude of blood flow reduction in PSRs was lower than in normal rats. These results indicate that EDRF plays an important role in control of the splanchnic circulation, but its effect on the hyperdynamic circulation observed in PSRs is insignificant.
Regulation of gene expression in gastric epithelial cell populations of fetal, neonatal, and adult transgenic mice
Authors: Roth K. A. , Cohn S. M. , Rubin D. C. , Trahair J. F. , Neutra M. R. , Gordon J. I.
Published: December 2017

Little is known about lineage relationships and differentiation programs of various epithelial cells present in mouse gastric units. We have previously used rat liver fatty acid binding protein/human growth hormone (L-FABP/hGH) transgenes to define epithelial cell lineages relationships in the small intestine of fetal and adult mice and to examine regulation of their terminal differentiation programs along the crypt-to-villus and duodenal-to-ileal axes. We have now used these transgenes to explore similar issues in the stomach. Immunocytochemical studies of fetal and adult transgenic L-FABP/hGH animals and their normal littermates revealed that the intact endogenous mouse L-FABP gene (Fabpl) is not expressed in gastric epithelium. Nucleotides-596 to +21 of the rat L-FABP gene direct "inappropriate" expression of hGH in the gastric epithelium as early as fetal day 15. From 1 to 13 mo, L-FABP-596 to +21/hGH expression occurs only in surface mucous cells of zymogenic and mucous gastric units; the reporter is not detectable in the enteroendocrine, parietal and chief cell populations of zymogenic glands. Electron microscopic immunocytochemistry revealed that hGH is directed to apical secretory granules in surface and pit mucous cells expressing the transgene. hGH levels vary widely among surface mucous cells both within single pits and between gastric units in a given animal. The heterogeneity noted in reporter expression suggests that there are marked differences in the regulatory environments of individual cells of a single type within a given gastric unit. This raises the possibility that cell differentiation programs in the stomach may not be as tightly coupled to cellular translocation as in the small intestine. Finally, the lack of expression of L-FABP-596 to +21/hGH in gastrin- and serotonin-immunoreactive cells of the stomach contrasts with its efficient expression in comparable cell types located in the duodenum; providing a model system for examining differential regulation of gene expression in terminally differentiated cell types represented in both gastric and intestinal epithelium.
Preservation and propagation of cyclic myoelectric activity after feeding in rat small intestine
Authors: Zenilman M. E. , Parodi J. E. , Becker J. M.
Published: December 2017

The cyclic nature and distal propagation of the fasting migrating motor complex (MMC) of the small intestine have been well described. The fate of the MMC after feeding, however, has not been elucidated. We used time series analysis with fast Fourier transforms (FFT) to study myoelectric cycling before and after feeding. Ten rats were chronically prepared with bipolar electrodes secured to the duodenum and proximal jejunum. Spikeburst frequency was recorded before and after feeding simple nutrients. During fasting, cyclic activity occurred at the MMC frequency. Although after feeding this periodicity appeared disrupted, FFT analysis showed persistent cycling at the fasted (MMC) rate. Digital filtering of data at the MMC frequency isolated cycling from background noise during both fasted and fed states and showed a depression in the amplitude of the waveform after feeding. Root-mean-square analysis of the waveform confirmed statistically significant depression of amplitude by 47-57%. The waveform propagated from the duodenum to the jejunum during both the fasted and fed state at an unchanged rate. We conclude that factors controlling myoelectric cycling during the fasted state persist after feeding, allowing continued net abroad propulsion of food.
Intestinal uptake and lymphatic absorption of beta-carotene in ferrets: a model for human beta-carotene metabolism
Authors: Wang X. D. , Krinsky N. I. , Marini R. P. , Tang G. , Yu J. , Hurley R. , Fox J. G. , Russell R. M.
Published: December 2017

To determine the appropriateness of the ferret as a model for human beta-carotene (beta-C) metabolism, we have perfused both 15,15'-beta-[14C]C and unlabeled beta-C through the upper 30-cm portion of the small intestine of ferrets in vivo. The effluents of a mesenteric lymph duct cannulation and a common bile duct cannulation, as well as portal vein blood periodically sampled via an indwelling catheter, were collected. Ten percent (9.5 +/- 0.06%) of the total administered beta-C was taken up by the intestine after a 4-h perfusion. Of the radioactivity taken up, 68.6 +/- 6.5% remained in the intestinal mucosa, 3.2 +/- 0.2% was recovered in the lymph, and 28.2 +/- 6.5% (calculated) was absorbed via the portal system. The total uptake/absorption of beta-C was 12.9 +/- 6.8 nmol.h-1.30 cm intestine-1. Large amounts of unchanged beta-C and relatively small amounts of both beta-apo-12'-carotenal and beta-apo-10'-carotenal were isolated in the intestinal mucosa after a 4-h perfusion with beta-C. Considerable amounts of metabolites more polar than retinol were formed and comprised 35% of the total radioactivity recovered in the intestinal mucosa. Polar metabolites were absorbed mostly into the portal venous system, whereas retinol and retinyl esters were absorbed mainly into the mesenteric lymph. Of the total absorbed radioactivity in lymph, 10 +/- 1.0% appeared as unchanged beta-C, with peak absorption occurring at 3 h after beginning the perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)
Galanin-induced alteration of electrolyte transport in the rat intestine
Authors: Kiyohara T. , Okuno M. , Ishikawa H. , Nakanishi T. , Shinomura Y. , Yanaihara C. , Matsuzawa Y.
Published: December 2017

Effects of rat and porcine galanin on rat intestinal ion transport were examined in vitro. In the rat distal colon, a sustained increase in short-circuit current (Isc) was produced by the serosal addition of rat galanin at a concentration as low as 10(-9) M, and a maximal increment was observed at 10(-7) M. Porcine galanin was approximately 100 times less potent than rat galanin. In the rat jejunum, rat galanin produced only a slight and transient decrease in basal Isc. The response to rat galanin was not influenced by atropine, hexamethonium, or amiloride, but was virtually abolished by tetrodotoxin or furosemide. Rat galanin did not significantly influence the increase in Isc elicited by electrical field stimulation in the rat colon and jejunum. Transmural unidirectional 22Na and 36Cl fluxes in the rat colonic mucosa were measured under short-circuited conditions, and rat galanin significantly decreased net sodium and net chloride absorption. These findings suggest that galanin acts as a secretory modulator in the rat colon via noncholinergic neural transmission.
Antibodies to tumor necrosis factor-alpha inhibit liver regeneration after partial hepatectomy
Authors: Akerman P. , Cote P. , Yang S. Q. , McClain C. , Nelson S. , Bagby G. J. , Diehl A. M.
Published: December 2017

Certain cytokines that are produced in liver may act as growth factors to facilitate wound healing and, hence, may influence liver regeneration. However, this hypothesis has not been directly tested. To determine whether the cytokine response evoked by partial hepatectomy (PH) modulates the process of liver regeneration, adult male rats were injected intraperitoneally with either goat polyclonal antibodies to rat tumor necrosis factor (TNF; 15 micrograms/g body wt) or an equal amount of goat anti-rat immunoglobulin G 1 h before PH. Animals were killed at 12, 24, 48, or 72 h post-PH, 1 h after injection with [3H]thymidine. Serum TNF levels were measured with the L929 cytotoxicity assay, titers of antibody to TNF were determined by enzyme-linked immunoabsorbent assay, and interleukin-6 (IL-6) concentrations were measured by B9 cell bioassay. Liver regeneration was assessed by [3H]thymidine incorporation into hepatic DNA and by immunohistochemical evidence of proliferating cell nuclear antigen (PCNA) expression. Antibodies to TNF were detected in treated rats but not in controls. Titers were highest at 12 h and progressively fell. Although TNF was never detected in serum, treatment with anti-TNF pre-PH significantly inhibited increases in serum IL-6 concentration post-PH. Anti-TNF pretreatment also inhibited [3H]thymidine incorporation into DNA, as well as expression of PCNA by both hepatocytes and liver nonparenchymal cells. These data indicate that TNF positively modulates liver regeneration after PH.
Sphincter of Oddi regulates flow by acting as a variable resistor to flow
Authors: Liu Y. F. , Saccone G. T. , Thune A. , Baker R. A. , Harvey J. R. , Toouli J.
Published: December 2017

Two models of transsphincteric flow and a model evaluating pumping activity were established in the anesthetized Australian brush-tailed possum to determine whether the sphincter of Oddi (SO) acts as a resistor or as a pump. A simple model of transsphincteric flow (inflow only) demonstrated that at physiological common bile duct (CBD) pressure, 9.5 +/- 0.3 cmH2O (n = 7), transsphincteric flow occurred between SO pressure waves (n = 10). A second more complex transsphincteric flow model was established that permitted simultaneous measurements of inflow, outflow, CBD pressure, SO basal pressure, SO contraction frequency, and amplitude. At physiological CBD pressure, inflow always equaled outflow (157.0 +/- 11.2 and 156.4 +/- 11.4 microliters/min, respectively; n = 7). The SO displayed regular contractions superimposed on a basal pressure of 1.1 +/- 0.4 mmHg. Contraction amplitude was 12.6 +/- 3.0 mmHg and the frequency was 3.6 +/- 0.4 contractions/min (n = 7). Pressure waves recorded in the CBD corresponded to the SO contractions and reflected SO activity. Transsphincteric flow occurred between SO contractions and was obstructed by these contractions. Stimulation of SO activity (basal pressure and contraction frequency) with intra-arterial injections of motilin (200 ng/kg) or erythromycin (200 micrograms/kg) abolished transsphincteric flow. Reduction in SO contraction frequency to 72.7 +/- 7.2% (P < 0.01, paired t test) after administration of Cisapride (2 mg/kg iv) increased transsphincteric flow to 147.6 +/- 12.3% (n = 7, P < 0.05, paired t test). In six possums, possible SO pumping action was evaluated. A manometer was connected to the CBD, and a second manometer was connected to the duodenum surrounding the papilla.(ABSTRACT TRUNCATED AT 250 WORDS)
Structural requirements of peptide YY for biological activity at enteric sites
Authors: Yoshinaga K. , Mochizuki T. , Yanaihara N. , Oshima K. , Izukura M. , Kogire M. , Sumi S. , Gomez G. , Uchida T. , Thompson J. C. , et al.
Published: December 2017

Peptide YY (PYY) is a colonic hormone consisting of 36 amino acids that is a potent inhibitor of pancreatic exocrine, gastric acid, and insulin secretion. The objective of the present experiments was to characterize the structural requirements of PYY for inhibition of pancreatic exocrine, gastric acid, and insulin secretion, using conscious dogs prepared with gastric and pancreatic fistulas. Intravenous administration of PYY-(1-36), PYY-(3-36), or PYY-(4-36) (400 pmol.kg-1 x h-1) inhibited cholecystokinin-8-stimulated (25 pmol.kg-1 x h-1) pancreatic exocrine secretion (P < 0.05); however, PYY-(1-10), PYY-(1-20), PYY-(6-36), PYY-(10-36), PYY-(13-36), PYY-(24-36), and PYY-(27-36) did not inhibit pancreatic exocrine secretion. Intravenous administration of PYY-(1-36), PYY-(3-36), or PYY-(4-36) (200, 400, 800 pmol.kg-1 x h-1) inhibited pentagastrin (0.5 microgram.kg-1 x h-1)-stimulated gastric acid secretion (P < 0.05), as well as 2-deoxy-D-glucose-stimulated insulin release (75 mg/kg) in a dose-related manner. PYY-(6-36), PYY-(13-36), and [Leu31, Pro34] neuropeptide Y did not inhibit either gastric acid secretion or insulin release. In the gastric acid and insulin secretion bioassays, PYY-(1-36) was significantly more potent than PYY-(3-36) and PYY-(4-36); however, in the pancreatic exocrine secretion bioassay, the inhibitory effects of PYY-(3-36) and PYY-(1-36) did not differ significantly. PYY-(4-36) was less potent than PYY-(1-36) on pancreatic exocrine secretion.(ABSTRACT TRUNCATED AT 250 WORDS)
Patterns of electrical activity and neural responses in canine proximal duodenum
Authors: Bayguinov O. , Vogalis F. , Morris B. , Sanders K. M.
Published: December 2017

The patterns of electrical activity and neural inputs to the proximal duodenum between the pyloric sphincter and the sphincter of Oddi were studied in muscles of the dog. Smooth muscle cells in the most proximal region were electrically quiescent, but slow waves were recorded in all regions distal to the first few millimeters. Electrical activity was recorded from circular muscle cells near the myenteric and submucosal surfaces of the circular layer, and slow wave activity was similar in both regions. The nature of neural inputs was also characterized. With electrical field stimulation, responses in cells near the submucosal surface were predominantly excitatory junction potentials (EJPs); near the myenteric border responses were either inhibitory junction potentials (IJPs) or biphasic responses (i.e., small EJPs followed by IJPs). EJPs were blocked by atropine. IJPs were nonadrenergic and noncholinergic (NANC), and several experiments suggested that nitric oxide (NO), or a NO-releasing compound, serves as the inhibitory neurotransmitter in this region. Exogenous NO caused hyperpolarization of membrane potential. IJPs and the hyperpolarization response to NO were sensitive to apamin. These data describe the myogenic mechanisms and neurogenic apparatus that appear to regulate motility in the most proximal region of the duodenum.
Myogenic mechanism for peristalsis in opossum smooth muscle esophagus
Authors: Helm J. F. , Bro S. L. , Dodds W. J. , Sarna S. K. , Hoffmann R. G.
Published: December 2017

We studied the propagation of phasic contractions initiated by tetraethylammonium (TEA, 1-10 mM), high K+ concentration (10-30 mM), and bethanechol (10(-6) to 10(-2) M) in a whole organ in vitro preparation of the opossum smooth muscle esophagus. TEA initiated phasic contractions that began at all sites along the smooth muscle esophagus and propagated in both directions with a velocity similar to that of primary peristalsis. Blockade of neural transmission by tetrodotoxin (TTX, 10(-7) M) did not prevent contraction propagation. Although a majority of contractions initiated by TEA did not propagate the full length of the esophageal specimen, with the addition of TTX most contractions initiated by TEA did propagate the full specimen length in either direction. High K+ concentration and bethanechol elicited propagated contractions similar to those initiated by TEA. We conclude that 1) a myogenic mechanism exists for propagation of contractions along the smooth muscle esophagus and 2) intramural inhibitory nerves modulate the extent of myogenic propagation in the ascending as well as descending direction. We suggest that esophageal peristalsis may occur by myogenic propagation of contractions that are normally initiated in the proximal smooth muscle esophagus by excitatory nerves. Intramural inhibitory nerves may inhibit retrograde propagation as well as mediate descending inhibition in advance of the peristaltic wave.
Induction of epithelial arachidonate 12-lipoxygenase at active sites of inflammatory bowel disease
Authors: Shannon V. R. , Stenson W. F. , Holtzman M. J.
Published: December 2017

To determine if epithelial lipoxygenases are regulated by mucosal inflammation, we examined the distribution of arachidonate 12-lipoxygenase in healthy colonic tissue and in involved and uninvolved sections of colon with inflammatory bowel disease. Immunohistochemistry of formaldehyde-fixed, paraffin-embedded intestinal tissue using two anti-12-lipoxygenase antibodies and indirect biotin-avidin-peroxidase detection demonstrated that, in contrast to tissue from normal colon (n = 8), in which 12-lipoxygenase antigen was undetectable in mucosal epithelial cells, the mucosal and glandular epithelium of inflamed colon in ulcerative colitis (n = 4) or Crohn's disease (n = 4) exhibited markedly positive immunostaining with anti-12-lipoxygenase antibodies. Immunoblotting of whole cell extracts with anti-12-lipoxygenase antibodies showed immunoperoxidase staining of a single protein band that comigrated with purified 12-lipoxygenase (in relative molecular weight: M(r) = 72,000) in mucosal samples from inflamed colon from subjects with ulcerative colitis or Crohn's disease but no comparable band in samples from uninvolved sections of the same colons or from colons of subjects without inflammatory bowel disease. Assays of 12-lipoxygenase activity indicated a corresponding increase in enzymatic activity in the same mucosal samples. The increased levels of 12-lipoxygenase antigen in the mucosal and glandular epithelial cells in regions of colon affected by inflammatory bowel disease, the corresponding increases in 12-lipoxygenase activity, and the absence of detectable 12-lipoxygenase antigen or enzymatic activity in the same cell types in noninflamed colonic tissue all suggest that epithelial cell 12-lipoxygenase is induced by local mediators of colonic inflammation.
ATP-sensitive potassium transport by pancreatic secretory granule membrane
Authors: Gasser K. W. , Holda J. R.
Published: December 2017

Electrolyte transport pathways in the pancreatic secretory granules may contribute to acini fluid production after fusion with the apical membrane. A component of this granule transport is a K(+)-selective pathway that has been measured indirectly by ionophore-induced lysis of the isolated secretory granules when suspended in a KCl solution. This granule membrane K+ transport was shown to be inhibited by physiological levels of ATP in a dose-dependent manner and was not reversed by ADP. The sulfonylurea tolbutamide (0.5 mM), a recognized inhibitor of ATP-sensitive K+ channels, also reduced the ionophore-dependent lysis by 46%. The ATP sensitivity of the K+ transport was influenced by pH (increased ATP sensitivity with decreasing pH) and KCl concentration (increased ATP sensitivity with increasing KCl). In addition, preincubation with phospholipase A2 (8.3 x 10(-10) g/ml) or lysophospholipids (6.7 x 10(-7) g/ml) produced a significant decrease in the granule K+ transport. However, it is not likely that this inhibition is due to a change in membrane fluidity, because fluidization with arachidonic acid or octanol did not have a comparable effect. The results then support a granule-associated K+ transport in pancreatic acinar cells and suggest that it is ATP and lysophospholipid sensitive.
Neural modulation of canine duodenal bile acid delivery in the interdigestive and postprandial periods
Authors: Scott R. B. , Tan D. T.
Published: December 2017

The neural modulation of gallbladder filling-emptying and duodenal delivery of canine hepatic biliary output was studied in conscious dogs using transient cold blockade or transection of the cervical vagosympathetic nerves previously isolated in skin loops on either side of the neck. Gallbladder filling-emptying was defined as the algebraic difference between a steady-state rate of hepatic secretion [established by a continuous intravenous infusion of [14C]taurocholic acid (TCA)] and the duodenal rate of delivery of [14C]TCA (measured by duodenal marker perfusion). Duodenal motility was recorded manometrically. Experiments in the fasted and fed state were performed under control conditions, during cold blockade, and after transection of the cervical vagosympathetic nerves. Under control conditions: 1) during fasting, the majority of hepatic [14C]TCA output was stored in the gallbladder during the first half of the migrating myoelectric complex (MMC). An increased rate of duodenal delivery and partial gallbladder emptying occurred before phase III of the MMC. 2) Feeding induced an immediate increase in duodenal bile acid delivery and gallbladder emptying. After cold blockade or transection: 1) partial gallbladder emptying before phase III of the MMC was abolished. 2) The immediate postprandial increase in duodenal bile acid delivery and gallbladder emptying was abolished even when the animal received a continuous duodenal infusion of the duodenal aspirate of another fed animal (to control for the effect of impaired gastric emptying after cold blockade). In addition, cold blockade significantly reduced the effect of an exogenous infusion of cholecystokinin octapeptide on gallbladder emptying. These results suggest that neurons in the canine cervical vagosympathetic nerves play a major role in the regulation of rhythmic partial emptying of the gallbladder in the interdigestive period, coordinate a cephalic phase of postprandial gallbladder emptying, and are important in mediating the effects of cholecystokinin on the gallbladder during the gastric and enteric phases of postprandial gallbladder emptying.
Intracellular free Mg2+ with pH changes in cultured epithelial cells
Authors: Quamme G. A.
Published: December 2017

Intracellular pH (pHi) alters cytosolic concentrations of electrolytes, including Ca2+ and Na+. The present studies determined the effect of pHi on intracellular free Mg2+ activity in two epithelial cell lines: one possessing absorptive and secretory functions (Caco-2 intestinal cells) and the second, an absorptive kidney cell line derived from the opossum kidney (OK).pHi and spatial H+ distribution were assessed by 2',7'-bis(carboxyethyl)-5(6')-carboxyfluorescein after an NH4+ pulse to provide rapid changes in pHi. [Mg2+]i, [Ca2+]i, and [Na+]i were measured by fluorescence techniques. [Mg2+]i and spatial Mg2+ distribution within single cells were not changed with rapid alkalinization and acidification procedures in both intestinal and renal cell lines. Alkalinization results in significant increases in [Ca2+]i and [Na+]i that return to basal levels after acidification in both Caco-2 and OK cell lines. These studies indicate that [Mg2+]i is not altered with changes in pHi and suggest that [Mg2+]i is maintained by means not related to pHi in these epithelial cells.
Effect of aging and bolus variables on pharyngeal and upper esophageal sphincter motor function
Authors: Shaker R. , Ren J. , Podvrsan B. , Dodds W. J. , Hogan W. J. , Kern M. , Hoffmann R. , Hintz J.
Published: December 2017

Effect of aging, bolus volume, temperature, and consistency on the pharyngeal peristalsis, as well as the effect of aging on the upper esophageal sphincter (UES) resting pressure and its response to esophageal distension by air and balloon, were studied in 14 young and 12 healthy elderly volunteers. In both age groups there was no significant volume or temperature effect on amplitude, duration, or velocity of the pharyngeal peristalsis. Compared with water swallows, mashed potato swallows resulted in a significant increase in the amplitude and duration of the hypopharyngeal peristaltic pressure wave (P < 0.05). For water swallows, the amplitude and duration of the peristaltic pressure wave in the hypopharynx were significantly increased in the elderly compared with the young group (P < 0.01). UES resting pressure in the elderly measured 43 +/- 5 (SE) mmHg and was significantly less than that of the young (71 +/- 8 mmHg; P < 0.01). Magnitude of the UES pressure decrease because of esophageal distension by air, as well as magnitude of its pressure increase because of esophageal balloon distension, was similar among young and elderly. 1) Contrary to common expectations, the parameters of the pharyngeal peristaltic pressure wave do not deteriorate in the elderly in their seventh and eighth decade. 2) Compared with the young, hypopharyngeal pressure wave amplitude and duration are significantly increased in the elderly. This increase could be caused by an adaptation response to a pharyngeal outflow compromise. 3) Pharyngeal peristaltic pressure wave amplitude and duration, but not its velocity, are modulated by the bolus consistency. This modulatory mechanism is preserved in the elderly. 4) Although UES resting pressure is significantly decreased in the elderly, its pressure response to esophageal distension by air and balloon is preserved.