bluuebunny/crossref_metadata_2025 huggingface dataset:
Chief cells possess a receptor with high affinity for PACAP and VIP that stimulates pepsinogen release
Authors: Felley C. P. , Qian J. M. , Mantey S. , Pradhan T. , Jensen R. T.
Published: December 2017

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 38-amino acid peptide of the secretin-vasoactive intestinal peptide (VIP) family. To investigate whether PACAP alters chief cell function, we prepared isolated chief cells (> 90% pure) from guinea pig stomach. PACAP-38, PACAP-27, VIP, and secretin all caused a threefold increase in pepsinogen release. The dose-response curves of PACAP-38, PACAP-27, and VIP were biphasic, whereas with secretin it was not. The first phase comprised 40% of maximal release, and each of the three peptides (PACAP-38, PACAP-27, and VIP) were equipotent (EC50 0.1-0.3 nM). For the second phase, comprising 60% of maximal release, the relative potencies were PACAP-38 > PACAP-27 = VIP. 125I-labeled secretin, 125I-VIP, and 125I-PACAP-27 all demonstrated saturable binding to chief cells. Binding of both 125I-PACAP-27 and 125I-VIP was inhibited completely and with similar potencies by PACAP-38, PACAP-27, and VIP. Secretin had a > 500-fold lower affinity than PACAP-38 for displacing both 125I-PACAP-27 and 125I-VIP. With 125I-secretin, secretin was the most potent, and was 197 times more potent than PACAP-38, which was 6-8 times more potent than both PACAP-27 and VIP. We conclude that both PACAP-38 and PACAP-27 stimulate pepsinogen secretion from dispersed chief cells. In contrast to a number of other tissues, no evidence for a high-affinity receptor that interacted only with PACAP was found. PACAP and VIP interact with equal high affinity with a common receptor and with low affinity with the secretin receptor.
Osmolarity reduction transiently increases K+ conductance of confluent rat hepatocytes in primary culture
Authors: Wehner F. , Beetz G. , Rosin-Steiner S.
Published: December 2017

Rat hepatocytes in confluent primary cultures were impaled with conventional microelectrodes. Reducing extracellular osmolarity by 80 mosmol/l leads to a transient hyperpolarization of cell membranes (maximum after 5 min) from -40 +/- 4 to -51 +/- 2 mV (n = 7). This hyperpolarization is blocked by 1 mmol/l Ba2+ and 0.5 mmol/l quinine. In ion substitution experiments, increasing K+ 10-fold (from 2.7 to 27 mmol/l) depolarizes membrane voltage by 9 +/- 2 mV in normosmotic solutions. In hyposmotic solutions this depolarization is increased to 20 +/- 1 mV at the time of maximum hyperpolarization and decreases thereafter to 8 +/- 2 mV (n = 4). Cable analysis reveals a transient decrease of specific membrane resistance that exactly parallels the increase in membrane voltage response to high K+. In addition, electrical coupling between cells continuously decreases under hyposmotic conditions, indicating that intercellular communication is affected. Reducing Cl- 100-fold (from 116.5 to 1.2 mmol/l; HCO(3-)-free solutions) depolarizes hepatocytes by 24 +/- 3 mV under normosmotic conditions. In hyposmotic solutions, this effect is increased to 39 +/- 4 mV at maximum hyperpolarization and decreases again to 26 +/- 3 mV (n = 8). This transient increase in the voltage response to Cl- removal is abolished by 0.5 mmol/l quinine (n = 5) and 1 mmol/l Ba2+ (n = 5), suggesting that it is indirect via changes in K+ conductance. This concept is corroborated by ion substitution experiments (HCO(3-)-free conditions), which show that under hyposmotic conditions voltage response to high K+ is considerably decreased in low Cl- solutions.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of aging on intestinal lipid absorption
Authors: Holt P. R. , Balint J. A.
Published: December 2017

Because of the "graying" of the population there is increasing interest in age-related changes in organ physiology. Impairment of lipid absorption, if present, could lead to malnutrition in the elderly while increased uptake of cholesterol could contribute to the rise in serum cholesterol levels seen in older individuals. This review critically analyzes the available information on age-related changes in digestive and absorptive physiology of lipids. Overall, the data suggest that lipid digestion and absorption are, in general, well-preserved in aging. However, intercurrent illness or experimental stress may produce impairment in aging animals and humans that are not seen in younger controls. Areas deserving more detailed study are identified in this review and include intestinal motility, adaptation to stress, and assembly and transport of lipoproteins from enterocytes to lymph.
Bradykinin-induced mesenteric vasodilation is mediated by B2-subtype receptors and nitric oxide
Authors: Berguer R. , Hottenstein O. D. , Palen T. E. , Stewart J. M. , Jacobson E. D.
Published: December 2017

We investigated mechanisms mediating bradykinin (BK)-induced anterior mesenteric artery (AMA) vasodilation in anesthetized rats. The velocity of blood flowing (VBF) in the AMA was measured with pulsed Doppler velocimetry, and arterial pressure (BP) was measured with a pressure transducer. Drugs were infused through an intra-aortic catheter positioned proximal to the AMA origin. AMA conductance (C) was calculated from mean VBF/BP and expressed as percent of control C. BK infusion (10-1,000 ng.kg-1.min-1) increased C significantly (Cmax = 201 +/- 18%, ED50 = 100 ng.kg-1.min-1, P < 0.01 for all doses). A B2-subtype receptor antagonist, D-Arg,[Hyp3,Thi5.8,D-Phe7]BK, administered at 10(5) ng.kg-1.min-1 before or during BK infusion, inhibited the vasodilation by 73 +/- 7 and 103 +/- 7%, respectively. A nitric oxide (NO) synthesis inhibitor, NG-nitro-L-arginine, administered at 5.0 mg/kg 15 min before BK, inhibited the hyperemia by 61 +/- 8%. Neither a B1-receptor antagonist nor intrajejunal capsaicin inhibited BK-induced vasodilation. BK-evoked, dose-dependent, mesenteric vasodilation in rats appears to be mediated partly by B2-receptors and endogenous NO generation.
Reconstitution of intestinal Na(+)-phosphate cotransporter
Authors: Peerce B. E. , Cedilote M. , Seifert S. , Levine R. , Kiesling C. , Clarke R. D.
Published: December 2017

The rabbit intestinal brush-border membrane Na(+)-phosphate cotransporter was purified from sodium dodecyl sulfate (SDS)-brush-border membrane vesicles (BBMV) protein (SDS-treated Ca(2+)-precipitated BBMV) by a three-column chromatography protocol. The purification included a preparative scale chromatofocusing chromatography column over the pH range from 7.4 to 4 after solubilization in 3-[(3-cholamidopropyl)-diamethylammonia]-1-propanesulfonate (CHAPS), a chromatofocusing column over the pH range from 5.6 to 4 after solubilization in n-octyl glucoside, and gel filtration chromatography on a Sephacryl S-200 column. Verification of Na(+)-phosphate cotransporter purification involved substrate affinities, substrate stoichiometry, and inhibitor sensitivity after proteoliposome reconstitution and SDS-polyacrylamide gel electrophoresis (PAGE). After gel filtration Na(+)-dependent phosphate uptake was 3,300-fold enriched compared with the cell homogenate. A single 130-kDa polypeptide was visualized by SDS-PAGE under reducing conditions using silver stain. The coenrichment of this 130-kDa polypeptide and proteoliposome reconstituted Na(+)-dependent phosphate uptake suggest that the intestinal brush-border membrane Na(+)-phosphate cotransporter has been purified and proteoliposome reconstituted.
Cecal fermentations in rats fed oligosaccharides (inulin) are modulated by dietary calcium level
Authors: Remesy C. , Levrat M. A. , Gamet L. , Demigne C.
Published: December 2017

The influence of Ca on the fermentation of dietary oligosaccharides in the large intestine has been investigated in four groups of rats fed different semipurified diets: 1) fiber free, 3 g Ca/kg; 2) fiber free, 8 g Ca/kg; 3) 15% inulin, 3 g Ca/kg; or 4) 15% inulin, 8 g Ca/kg. The cecal fermentations were very low in rats fed the fiber-free diets and were not affected by the dietary Ca level. Rats fed the inulin diets had enlarged cecum with acidic fermentations, relatively rich in propionic acid. In this diet group rats adapted to the 3 g Ca/kg level had very acidic fermentations and depressed volatile fatty acid concentrations together with an accumulation of lactic acid (L and D isomers). Inulin diets brought about a rise in the crypt column height and in the activity of ornithine decarboxylase in cecal mucosa, especially in the 3 g Ca/kg diet group. There was considerable accumulation of insoluble Ca and Pi in the cecum of rats fed high-Ca diets. Inulin feeding increased the percentage of soluble Ca and Pi; Ca absorption from the cecum was also markedly higher in rats fed inulin and was influenced by the dietary Ca level. The concentrations of soluble bile acids were depressed in rats fed inulin diets, which enhanced the fecal excretion of bile acids. These effects were poorly altered by changes in the dietary Ca level. In vitro it appears that CaPi is effective in decreasing the solubility of bile salts, chiefly in acidic conditions. In conclusion there is in the large intestine a system of control of luminal pH, which involves the presence of insoluble Ca and Pi.(ABSTRACT TRUNCATED AT 250 WORDS)
Biological activity of metabolites of PGD2 on canine proximal colon
Authors: Rangachari P. K. , Betti P. A.
Published: December 2017

The responses of the canine colonic epithelium to the metabolites of prostaglandin D2 (PGD2) were compared with those elicited by the parent prostanoid. Dose-response relations to PGD2 showed three distinct patterns: 1) a dose-dependent decrease in short-circuit current (Isc) at lower concentrations followed by a dose-dependent increase at higher concentrations; 2) dose-dependent decreases, with no increase even at the highest concentrations tested; and 3) dose-dependent increases in Isc, with no decreases at any concentration. The colon responded differently to the two enzymatically derived metabolites 13,14-dihydro-15-keto-PGD2 (DK) and 11 beta-PGF2 alpha. The former consistently produced only dose-dependent decreases in Isc, while the latter elicited only dose-dependent increases. Pretreatment of tissues with 11 beta-PGF2 alpha altered the responses to PGD2 such that only decreases were noted. Conversely, pretreatment with DK caused PGD2 to elicit only increases in Isc. The nonenzymatically derived PGJ2 elicited responses comparable to those seen with PGD2. Pretreatment of tissues with indomethacin abolished responses to 11 beta-PGF2 alpha as well as its isomer, PGF2 alpha, suggesting the involvement of a cyclooxygenase product. Responses to PGE2 were, however, amplified. Cross-desensitization was noted between the two isomers. Tissues desensitized to either 11 beta-PGF2 alpha or PGF2 alpha were responsive to DK as well as PGE2; however, tissues desensitized to PGE2 were unresponsive to 11 beta-PGF2 alpha. Thus the canine colonic epithelium responds not only to PGD2 but also to its derived metabolites. Variability in the response to PGD2 between animals could stem from differences at the receptor level and/or differential production of these metabolites.
Retinol release by activated rat hepatic lipocytes: regulation by Kupffer cell-conditioned medium and PDGF
Authors: Friedman S. L. , Wei S. , Blaner W. S.
Published: December 2017

In normal liver, lipocytes are the principal reservoir for retinoids, which are stored as retinyl esters. In liver injury, lipocytes activate into myofibroblast-like cells, which lack retinoid. We examined mechanisms of retinoid loss using a culture model in which lipocyte activation is provoked by exposure to Kupffer cell-conditioned medium (KCM) (S.L. Friedman and M. J. P. Arthur, J. Clin. Invest. 84: 1780-1785, 1989). In lipocytes exposed to KCM, there was approximately 11-fold more retinol in medium than in untreated cells, without release of retinyl esters. Both bile salt-dependent and -independent retinyl ester hydrolase was entirely intracellular, suggesting that the increase in retinol was due to intracellular hydrolysis; activity of bile salt-independent hydrolase was increased in KCM-treated lipocytes. Release of retinol was serum dependent and inhibited 40% by antibodies to platelet-derived growth factor (PDGF). The addition of 10 nM PDGF to serum-free KCM also induced retinol release. Lipocyte expression of mRNAs for cellular retinol-binding protein, retinoic acid receptor (RAR)-alpha, and RAR-beta was unchanged after exposure to KCM. In summary, activation of cultured lipocytes by KCM is accompanied by serum- and PDGF-dependent release of retinol; a similar mechanism may underlie retinoid loss by activated lipocytes in vivo.
Effects of selective zonal injury on bile acid-induced bile flow in the isolated rat liver
Authors: Monte M. J. , Badia M. D. , Palomero F. , el-Mir M. Y. , Alonso J. R. , Marin J. J.
Published: December 2017

The importance of acinar heterogeneity in ursodeoxycholic acid (UDCA)-induced bile flow was assessed in isolated rat livers that underwent restricted acinar damage by antegrade (A; 50 nmol) or retrograde (R; 500 nmol) digitonin infusion, as confirmed by histological evaluation. Stability of reduced (-40%) bile flow and perfusion flow (-25%) at constant pressure and potassium and lactate dehydrogenase release indicated similar viability of A and R preparations. They also showed similar abilities to secrete increasing doses of taurocholate (TC, maximal secretion rate approximately 105 nmol.min-1.g liver-1). TC-induced bile flow was not reduced by digitonin. In contrast, UDCA-induced choleresis was sensitive to zonal injury. Moreover, increases in bile flow and bicarbonate secretion observed under UDCA infusion (1.5 mumol/min) were lower in R than in A (-33 and -51%, respectively). No significant difference was observed in UDCA amidation or glucuronation between A and R preparations. With the use of single-pass perfusion on intact isolated livers that received 1 or 10 mumol UDCA, an early peak in bile acid output was observed to occur before the appearance of the major secretory peak. This was not found when 1 mumol of chenodeoxycholic acid bolus or trace amounts of [14C]TC were given. High-performance liquid chromatographic analysis of the early peak revealed it to be mainly due to unconjugated UDCA. This suggests the existence of a diffusional pathway for protonated bile acids and hence that the exist of lipophilic UDCA from bile during its way through the intra-acinar canaliculi across this pathway is also possible.(ABSTRACT TRUNCATED AT 250 WORDS)
Lateral hypothalamic lesions cause gastric injury by stimulating gastric contractility
Authors: Garrick T. , Grijalva C. V. , Trauner M.
Published: December 2017

Changes in gastric contractility following lateral hypothalamic (LH) lesions with and without bilateral cervical vagotomy were measured in urethan-anesthetized rats. LH lesions were induced with direct current passed through stereotaxically placed electrodes. Gastric contractility was recorded continuously for 4 h with acutely implanted strain gauge force transducers and analyzed by computer. LH lesions consistently stimulated gastric contractility and caused more gastric mucosal injury than control conditions. Vagotomy blocked both gastric mucosal injury and high-amplitude gastric contractions. In rats with LH lesions and exogenously infused intragastric hydrochloric acid, atropine methyl nitrate inhibited high-amplitude gastric contractions and gastric erosions. These findings indicate that LH lesions stimulate vagally mediated high-amplitude gastric contractions, which, in the presence of hydrochloric acid, cause gastric mucosal erosions.
Cholecystokinin receptors and PANC-1 human pancreatic cancer cells
Authors: Smith J. P. , Rickabaugh C. A. , McLaughlin P. J. , Zagon I. S.
Published: December 2017

The gastrointestinal peptide cholecystokinin (CCK) has been shown to stimulate growth of human pancreatic adenocarcinoma in vitro and in vivo, although CCK receptors have not been identified in pancreatic cancer cells. The purpose of this study was to characterize the CCK receptors in pancreatic cancer cells and to correlate the receptor binding studies with the trophic action of CCK agonists and antagonists. With the use of homogenates of PANC-1 human pancreatic cancer cell line grown in culture, the binding of 125I-labeled CCK octapeptide (125I-CCK-8) was examined under various conditions to characterize the CCK receptor. Specific and saturable binding of 125I-CCK-8 was detected in PANC-1 cells; data were consistent with a single binding site. Scatchard analysis yielded a binding affinity [dissociation constant (Kd)] of 2.8 nM and a binding capacity of 26 fmol/mg protein. Binding was dependent on protein concentration, time, temperature, the presence of protease inhibitors, and pH and was sensitive to Na+, K+, Mg2+, and ethylene glycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Competition experiments indicated that L-365,260, a selective CCK-B (gastrin) receptor antagonist, was the most potent displacer of 125I-CCK-8, and no significant displacement of binding was found with the selective CCK-A receptor antagonist. Growth of PANC-1 cells in culture was stimulated by CCK at a concentration consistent with the Kd, and CCK-stimulated growth was inhibited by the CCK-B receptor antagonist (L-365,260) not the CCK-A receptor antagonist (L-364,718).(ABSTRACT TRUNCATED AT 250 WORDS)
Nitric oxide generators and cGMP stimulate mucus secretion by rat gastric mucosal cells
Authors: Brown J. F. , Keates A. C. , Hanson P. J. , Whittle B. J.
Published: December 2017

The effect of nitric oxide (NO) donors on the release of mucus from a suspension of isolated gastric cells was investigated by using an enzyme-linked immunosorbent assay for rat gastric mucin. Isosorbide dinitrate (ISDN, 0.1-2 mM) produced a dose-related stimulation of mucus secretion, without affecting the viability of the isolated cells as determined by trypan blue exclusion or acid phosphatase release. In a comparable concentration range to that stimulating mucus release, ISDN elevated the guanosine 3',5'-cyclic monophosphate (cGMP) content of cell suspensions enriched with mucous cells. The nitrosothiol S-nitroso-N-acetylpenicillamine (0.3 mM), which spontaneously liberates NO, likewise stimulated mucus release, and this action was blocked by 10 microM oxyhemoglobin, which scavenges NO. Nitroprusside (1 mM), dibutyryl cGMP (0.01-1 mM), and the cGMP phosphodiesterase inhibitor M & B 22948 (0.1 mM) also increased mucus release. Thus generators of NO stimulate mucus secretion by rat gastric mucosal cells, which may reflect the elevation of intracellular cGMP. These findings, along with the presence of NO synthase in the gastric epithelial cells, suggest an effector role for NO in mediation of gastric mucus release.
Cerebral metabolic and histological effects of thioacetamide-induced liver failure
Authors: Peeling J. , Shoemaker L. , Gauthier T. , Benarroch A. , Sutherland G. R. , Minuk G. Y.
Published: December 2017

Acute liver failure was induced in rats by successive administrations of thioacetamide over 3 days. At progressing stages of hepatic encephalopathy (HE), brains were fixed with microwave irradiation for analysis of metabolite levels or with formaldehyde for histopathological analysis. Metabolite levels were determined using 1H-nuclear magnetic resonance spectroscopy of perchloric acid extracts of the frontal cortex, parietal or occipital cortex, hippocampus, striatum, brain stem, and cerebellum. After thioacetamide treatment, thioacetamide and its metabolites were detected in the brains at levels that did not correlate with the stage of HE. No changes were observed in the levels of N-acetylaspartate, alanine, gamma-aminobutyric acid, aspartate, or inositol in any brain region after thioacetamide treatment. HE was accompanied by elevated glutamine, glucose, and lactate throughout the brain. At all stages of HE, taurine was decreased in the neocortex and hippocampus, and glutamate and choline compounds were decreased in the frontal cortex. None of the metabolite changes showed progression with the stage of HE. Progressing HE was accompanied by increasing neuronal injury in layer III of the neocortex, in the Purkinje cells of the cerebellum, and in the hippocampus, particularly in the CA4 sector. The similarity of this distribution of injury to that associated with excitotoxic injury suggests that metabolic abnormalities after acute hepatic failure may give rise to adverse effects at excitatory (glutamatergic) neuronal receptors, leading to neuronal injury and clinical symptoms of progressing encephalopathy in this model. However, neuronal injury and the presence of thioacetamide and its metabolites in the brain raise questions about the validity of thioacetamide-induced liver failure as a model for clinical HE.
Quantitative relationship between liquid bolus flow and laryngeal closure during deglutition
Authors: Maddock D. J. , Gilbert R. J.
Published: December 2017

We employed digital image analysis to assess the relative movements of the hyoid, larynx, and bolus as a function of liquid bolus volume (2-15 ml), and synchronized these measurements with intrapharyngeal manometry. Comparisons were performed of bolus head and tail movement in relation to the timing of hyoid movement, contact between the arytenoid and epiglottic cartilages, and intrabolus pressures. Bolus head movement in the distal pharynx, as determined from flow plots, was relatively rapid. Initial bolus tail movement in the distal pharynx was delayed proportional to bolus volume, and once initiated, was slower than bolus head movement. Laryngeal exposure time, defined as the interval between bolus head arrival and tail departure at the hypopharyngeal recording sensor, increased as a function of bolus volume. The time interval between the initial anterior hyoid movement and bolus arrival at the larynx, determined by concurrent plotting of hyoid excursion and bolus head position, was constant despite increasing bolus volume. Similarly, the interval between epiglottic-arytenoid contact and bolus arrival was constant despite increased bolus volume. The early phase of intrabolus pressure was temporally associated with posterior movement of the tongue base and varied as a function of bolus volume, whereas late intrabolus pressure was temporally associated with initial pharyngeal wall movement and was not significantly volume dependent. These data indicate that the temporal relationship between laryngeal closure and bolus head flow remains constant despite changes of laryngeal exposure time to the bolus as a function of volume.
Sex differences in intracellular fatty acid transport: role of cytoplasmic binding proteins
Authors: Luxon B. A. , Weisiger R. A.
Published: December 2017

Female liver clears long-chain fatty acids from plasma more rapidly than male liver, and yet the basis for this sex difference is poorly understood. We tested the hypothesis that cytosolic fatty acid binding protein (FABP), which is more concentrated in female liver, may enhance fatty acid utilization by increasing the rate of transport through the cytoplasm. We modified the technique of fluorescence recovery after laser photobleaching to measure the cytoplasmic diffusion rate of the fluorescent long-chain fatty acid 12-N-methyl-(7-nitrobenz-2-oxa-1,3-diazol)aminostearate (NBD-stearate) in cultured hepatocytes from female and male rats. NBD-stearate was used because its hepatic handling is similar to natural fatty acids. After uptake, NBD-stearate distributed uniformly in the cytoplasm but was excluded from the nucleus. Intracellular transport occurred by diffusion with no detectable convective flux. The cytoplasmic diffusion rate at 37 degrees C was 65% greater in female cells than in male cells (mean +/- SE, 5.03 +/- 0.37 vs. 3.05 +/- 0.21 x 10(-9) cm2/s respectively; P < 0.001) and was two to three orders of magnitude slower than for either unbound NBD-stearate or FABP in water. A correspondingly greater fraction of cellular NBD-stearate was found in the aqueous cytosol in females (35.1 +/- 7.0 vs. 18.2 +/- 2.7%), suggesting that FABP reduces binding of NBD-stearate to immobile cytoplasmic membranes. These data indicate that intracellular transport of NBD-stearate, a typical amphipathic molecule, is slowed by binding to cytoplasmic membranes. The primary function of soluble binding proteins such as FABP may be to enhance the diffusive fluxes of their ligands by reducing membrane binding. If cytoplasmic transport of rapidly metabolized fatty acids such as palmitate is similarly slow, substantial concentration gradients could develop within the cytoplasm of hepatocytes at steady state. By catalyzing these diffusive fluxes, FABP may regulate fatty acid metabolism.
Role of endothelial adhesion molecules in NSAID-induced gastric mucosal injury
Authors: Wallace J. L. , McKnight W. , Miyasaka M. , Tamatani T. , Paulson J. , Anderson D. C. , Granger D. N. , Kubes P.
Published: December 2017

A number of recent studies have demonstrated that neutrophil adherence to the vascular endothelium is a critical early event in the pathogenesis of gastric mucosal injury induced by nonsteroidal anti-inflammatory drugs (NSAIDs). Although a role in this process for the leukocyte adhesion molecule, CD11/CD18, has been demonstrated, the involvement of endothelial adhesion molecules has not previously been examined. Therefore, using monoclonal antibodies directed against a number of endothelial adhesion molecules (ICAM-1, P-selectin, E-selectin), we studied the role of these molecules in the production of mucosal injury after indomethacin administration and in indomethacin-induced leukocyte adherence. As previously shown in the rabbit, anti-CD18 markedly reduced (by 75%) the severity of damage induced by indomethacin in the rat. Moreover, this antibody completely prevented indomethacin-induced leukocyte adherence. Similarly, anti-ICAM-1 significantly attenuated (by 74%) the severity of indomethacin-induced gastric injury while also markedly reducing leukocyte adherence (by 83%). Anti-P-selectin and anti-E-selectin produced only small (approximately 35%), but statistically significant, reductions of mucosal injury, but only anti-P-selectin significantly affected indomethacin-induced leukocyte adherence (by approximately 50%). These results demonstrate that indomethacin-induced leukocyte adherence and mucosal injury are dependent on the expression of CD18 and ICAM-1. P-selectin also appears to play a small, but important, role in these processes, whereas the role of E-selectin remains equivocal. These studies support the hypothesis that interactions at the leukocyte-endothelium interface are critical in the pathogenesis of NSAID-induced mucosal injury, and this interface may represent a rational target for therapies aimed at preventing this form of injury.
Relationship between tumor necrosis factor-alpha and neutrophils in endotoxin-induced liver injury
Authors: Hewett J. A. , Jean P. A. , Kunkel S. L. , Roth R. A.
Published: December 2017

Tumor necrosis factor-alpha (TNF-alpha) and blood neutrophils (polymorphonuclear leukocytes; PMNs) have been implicated in the pathogenesis of endotoxin (lipopolysaccharide, LPS) hepatotoxicity. However, the mechanism by which these factors mediate liver injury during LPS exposure is uncertain. The objective of this study was to test the hypothesis that TNF-alpha contributes to LPS hepatotoxicity by an indirect, PMN-dependent mechanism. Pretreatment of rats with an antiserum to TNF-alpha afforded protection against liver injury 6 h after LPS exposure. Pretreatment with pentoxifylline (100 mg/kg i.v.), which attenuated the increase in circulating TNF-alpha concentration 1.5 h after administration of LPS, also afforded protection against liver injury. Neither antiserum to TNF-alpha nor pentoxifylline affected hepatic PMN accumulation 1.5 h after LPS exposure. Depletion of circulating PMNs, which protects against LPS hepatotoxicity, enhanced circulating TNF-alpha concentration compared with control rats 1.5 h after LPS exposure. These results suggest that TNF-alpha contributes to liver injury after LPS exposure, but in the absence of circulating PMNs it is insufficient for full manifestation of liver injury. TNF-alpha apparently contributes to the pathogenesis of LPS-induced liver injury by an indirect, PMN-dependent mechanism.
Characterization of galanin receptor in canine small intestinal circular muscle synaptosomes
Authors: Chen C. K. , McDonald T. J. , Daniel E. E.
Published: December 2017

We used 125I-galanin (porcine) as ligand to study the galanin receptors in circular muscle and deep muscular plexus from canine small intestine. Specific binding sites were found in both nerve and muscle membranes. On synaptosomal membranes, the equilibrium binding study showed a high-affinity (dissociation constant, Kd = 1.1 +/- 0.13 nM; maximum binding capacity, Bmax = 244 +/- 2.1 fmol/mg) binding site. The specific binding of 125I-galanin to nerve membrane was inhibited by galanin or NH2-terminal galanin fragments but not by the COOH-terminal fragment. Computer analysis suggested a two-site model (inhibitor constants, Ki1 = 0.02 +/- 0.005 nM and Ki2 = 1.05 +/- 0.3 nM) for competition by galanin-(1-29). Kinetic and competition studies using guanosine 5'-O-(3-thiotriphosphate) or pertussis toxin (PTX) suggested that the high-affinity binding site involved a PTX-sensitive G protein which acted to slow dissociation of bound galanin from the receptor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the galanin receptor complex revealed a radioactive band at 50 kDa. We conclude that, in canine small intestine, galanin may act as an inhibitory neuromodulator by a PTX-sensitive G protein-coupled interaction of galanin and its specific receptor on enteric nerve synaptosomes
5-HT1A and 5-HT4 receptors mediate inhibition and facilitation of fast synaptic transmission in enteric neurons
Authors: Pan H. , Galligan J. J.
Published: December 2017

The actions of 5-hydroxtryptamine (5-HT)1A and 5-HT4 receptor agonists on fast excitatory postsynaptic potentials (EPSPs) in myenteric neurons of guinea pig ileum were studied in vitro. Intracellular electrophysiological methods were used to record EPSPs. 5-HT (0.1 microM), 5-carboxamidotryptamine (0.001-0.1 microM), 8-hydroxydipropylaminotetralin (0.003-0.3 microM), and 5-methoxytryptamine (5-MeOT; 0.3 microM) inhibited EPSPs. Agonist inhibition of EPSPs was blocked by the 5-HT1A receptor antagonists, spiperone and NAN-190. In the presence of NAN-190 (0.3 microM), 5-HT (0.001-0.1 microM) increased EPSP amplitude. 5-MeOT (0.001-0.1 microM), renzapride (0.01-0.3 microM), cisapride (0.01-1 microM), and BIMU 8 (0.003-0.1 microM) increased EPSP amplitude but did not change the membrane potential of any neuron. EPSP potentiation induced by each agonist was blocked by the 5-HT3/5-HT4 receptor antagonist, tropisetron (1 microM), but not by the 5-HT3 receptor antagonist, ondansetron (1 microM). Potentiation of fast EPSPs by 5-HT (0.1 microM) desensitized, whereas renzapride (0.1 microM) responses did not. Desensitization induced by BIMU 8 was variable. These data indicate that enteric 5-HT1A and 5-HT4 receptors function to inhibit and facilitate transmitter release, respectively. 5-HT4-mediated facilitation of ganglionic neurotransmission could contribute to the prokinetic effects of cisapride and renzapride.
Contractile mechanisms of action of gastroprokinetic agents: cisapride, metoclopramide, and domperidone
Authors: Orihata M. , Sarna S. K.
Published: December 2017

We investigated the contractile mechanisms of action of three putative gastroprokinetic agents (cisapride, metoclopramide, and domperidone) on the linear phase of gastroduodenal emptying of solid meals in six healthy conscious dogs. The spatial and temporal parameters of gastric, pyloric, and duodenal contractions during the entire period of gastroduodenal emptying, during the 60-min period of drug infusion (ti), and during the postdrug infusion period (tpi) were analyzed by a computer method. Cisapride accelerated the total gastroduodenal emptying time (tfull), metoclopramide had no significant effect, and domperidone delayed the tfull. None of the drugs had a significant effect on gastroduodenal emptying during ti. Both cisapride and metoclopramide enhanced the rate of gastroduodenal emptying during tpi. Cisapride enhanced pyloric and duodenal motor activity but had no significant effect on antropyloroduodenal coordination during tfull and ti. During tpi, cisapride significantly enhanced both the pyloric and duodenal motor activity and antropyloroduodenal coordination. Metoclopramide exhibited only a few significant effects on the frequency, amplitude, duration, and area under contractions in the antrum, pylorus, and duodenum, but it enhanced antropyloroduodenal coordination during tfull and tpi. Domperidone decreased the frequency of corporeal, pyloric, and duodenal contractions and deteriorated antropyloroduodenal coordination by decreasing the frequency of contractions propagating from the antrum or the pylorus to the duodenum. Cisapride and metoclopramide, but not domperidone, increased the mean distance of propagation of duodenal contractions during tfull, ti, and tpi. We conclude that cisapride is more effective in accelerating gastroduodenal emptying because it stimulates the largest number of parameters of gastropyloroduodenal contractions that enhance gastric emptying. Most enhancement of gastric emptying rate with both cisapride and metoclopramide occurs during tpi.
Hepatic removal of two fractions of indocyanine green after bolus injection in anesthetized pigs
Authors: Ott P. , Keiding S. , Johnsen A. H. , Bass L.
Published: December 2017

In the anesthetized pig, we studied the kinetics after intravenous bolus injection of two fractions of indocyanine green (ICG): the genuine ICGg (95-99% of total) and a degradation product, ICGdp (1-5%). Plasma concentrations were followed in the carotid artery and a hepatic vein. ICGg disappearance curves (n = 7) were biexponential with rate constants alpha = 0.189 +/- 0.021 min-1 and beta = 0.0356 +/- 0.0061 min-1. The hepatic extraction fraction was constant with time. A detailed mathematical analysis showed this to be in disagreement with the conventional assumption that the biexponential plasma disappearance curve is a result of backflux from the liver storage to plasma. In contrast, our observations were predicted by an alternative model assuming temporary extrahepatic, extravasal redistribution during first-order, one-way hepatic uptake. Nevertheless, when a large bolus of sulfobromophthalein (BSP) was injected 20 min after ICG, a net backflux of ICG could be demonstrated, presumably due to countertransport. Thus a sufficient description of ICGg kinetics must include the complex kinetic behavior of the hepatic membrane carrier involved. Mass spectrometry suggested that ICGdp is formed by two ICGg molecules. Plasma elimination of ICGdp was slower (alpha = 0.0094 +/- 0.0007 min-1). Analysis of the bile after bolus injection (n = 2) of ICGdp revealed two possible metabolites of ICGdp that were not found in urine. Since BSP injection did not alter the ICGdp disappearance curve, ICGdp is probably not taken up by the same hepatic membrane carrier as ICGg.
Vasomotion induces regular major oscillations in jejunal mucosal tissue oxygenation
Authors: Hasibeder W. , Germann R. , Sparr H. , Haisjackl M. , Friesenecker B. , Luz G. , Pernthaler H. , Pfaller K. , Maurer H. , Ennemoser O.
Published: December 2017

The mucosa of the small intestine has some unique microcirculatory features that may result in significant tissue oxygenation changes even under physiological conditions. To prove this hypothesis we investigated mucosal and serosal oxygenation in an autoperfused, innervated jejunal segment in pigs. Eight animals (30-40 kg) were anesthetized, paralyzed, and normoventilated. A small segment of the jejunal mucosa and serosa was exposed by a midline laparotomy and an antimesenteric incision. Mucosal and serosal oxygen tensions were measured using Clark-type surface oxygen electrodes. Mucosal hemoglobin saturation and concentration were determined by tissue reflectance spectrophotometry. Systemic hemodynamics, mesenteric-venous acid base, and blood gas variables, as well as systemic acid-base and blood gas variables and jejunal electromyogenic potentials, were recorded. Measurements were performed after a rest period at 0, 30, 60, and 90 min. All animals remained hemodynamically stable. At time 0 the jejunal oxygen extraction ratio was 0.33 +/- 0.05, the mean serosal PO2 was 60.25 +/- 7.69, the mean mucosal PO2 was 25.47 +/- 4.41 mmHg, and the mean mucosal hemoglobin saturation was 46.36 +/- 6.22%. Mean values did not change with time. In contrast to serosal PO2, mucosal PO2, mucosal hemoglobin oxygen saturation, and hemoglobin concentration showed rhythmic oscillations with a frequency of 3.4-5 cycles/min that were unrelated to systemic hemodynamic parameters, respiratory frequency, and intestinal peristalsis. From this we concluded that the jejunal mucosa demonstrates significant, regular changes in oxygenation parameters that are locally mediated. We speculate that the physiological basis for this phenomenon is the countercurrent arrangement of microvessels in conjunction with vasomotion.(ABSTRACT TRUNCATED AT 250 WORDS)
Use of isografts to study proliferation and differentiation programs of mouse stomach epithelia
Authors: Rubin D. C. , Swietlicki E. , Gordon J. I.
Published: December 2017

A new model system has been developed for studying the factors that regulate the proliferation and differentiation programs of the principal cell lineages present in the mouse stomach epithelium. When embryonic day 14 (E14) stomachs from C57Bl/6 mice are implanted under the subcutaneous fascia of young adult male CBY/B6 nude mouse recipients, they are rapidly vascularized and begin to grow at rates comparable to the intact stomach of a similarly aged animal. Single- and multilabel immunohistochemical studies, conducted in the intact stomach of E14 to postnatal day 42 (P42) C57Bl/6 mice and in P7, P14, P28, and P42 C57Bl/6 isografts, suggest that the apparently undifferentiated glandular epithelium of E14 stomach already has encoded positional information that permits it to establish regional differences in cell populations even in the absence of exposure to normal luminal contents. Regional differentiation is manifested by the establishment of distinct zones, each composed of gastric units with zone-specific cell lineages. This axial patterning evolves at a rate similar to that of the intact stomach, even though the E14 isograft is placed in the hormonal environment of an adult host and therefore cannot be programmed by normal developmental changes in endocrine status. Moreover, patterning is maintained in isografts despite continuous renewal of its epithelial cell lineages. Although isografts apparently possess autonomously functioning temporal and spatial programs, perturbations were noted in the proliferation and/or differentiation programs of certain lineages, e.g., the rate of accumulation of endocrine cell subpopulations is reduced in these grafts.(ABSTRACT TRUNCATED AT 250 WORDS)
Pentagastrin enhances gastric mucosal defenses in vivo: luminal acid-dependent and independent effects
Authors: Nishizaki Y. , Guth P. H. , Kim G. , Wayland H. , Kaunitz J. D.
Published: December 2017

Stimulation of acid secretion is associated with enhanced resistance of the gastric mucosa to damage by luminal acid. We studied the mechanism by which gastric mucosal defenses are modulated in a system in which mucus gel thickness, intracellular pH (pHi), gastric mucosal blood flow, and acid secretion can be measured simultaneously in vivo, using a recently developed microfluorometric technique. Intravenous infusion of pentagastrin in a dose associated with maximal acid secretion increased mucus gel thickness, pHi, and mucosal blood flow during superfusion with a neutral solution. Subsequent superfusion with an acidic buffer (pH 1.7) further increased blood flow to nearly three times basal. During superfusion with luminal acid, pHi fell more slowly and recovered toward baseline more quickly in pentagastrin-infused rats than in controls. Pretreatment with the H2-receptor antagonist cimetidine abolished the increased blood flow associated with pentagastrin, impairing pHi homeostasis, although cimetidine increased mucus gel thickness in the absence of pentagastrin. We conclude that gastric defense mechanisms at the preendothelial and postepithelial levels are enhanced during acid secretion as part of a histamine-dependent homeostatic mechanism that balances gastric protective mechanisms with acid secretion. The net result of these enhanced defenses is the preservation of gastric surface cell pHi despite the presence of a large proton gradient between lumen and blood.
Differential production of TNF by Kupffer cells after phagocytosis of E. coli and C. albicans
Authors: Olynyk J. K. , Matuschak G. M. , Lechner A. J. , Britton R. S. , Tredway T. L. , O'Neill R. , Bacon B. R.
Published: December 2017

Tumor necrosis factor (TNF) of hepatic origin is thought to play a pivotal role early in the genesis of the septic shock syndrome, regardless of microbial etiology. To determine if production of TNF by Kupffer cells varies with microbial taxonomic class, we measured TNF secretory responses in primary cultures of rat Kupffer cells to numerically equivalent gram-negative bacterial or fungal phagocytic challenges. After a 30-min exposure to media, latex beads, soluble Escherichia coli lipopolysaccharide (LPS; serotype 055:B5), live or Formalin-fixed E. coli (serotype 055:B5), live or Formalin-fixed yeast-phase Candida albicans, or live hyphal-phase Candida, samples of culture supernatant were assessed at 30, 60, 120, and 240 min and at 24 h for TNF bioactivity by L929 cell cytotoxicity. Compared with media and latex bead controls, TNF levels progressively increased for up to 240 min after either LPS and equivalently in live E. coli or Formalin-fixed E. coli groups (P < 0.05). Formalin-fixed yeast-phase and live extracellular hyphal-phase C. albicans failed to stimulate production of TNF at any time point (6.9 +/- 0.7 and 8.7 +/- 0.4 U/ml, respectively, at t = 240 min; P < 0.05 vs. E. coli). In contrast, internalization of live yeast-phase C. albicans with subsequent hyphal formation and growth within Kupffer cells was accompanied by a rise in supernatant TNF levels (14.5 +/- 1.8 U/ml at t = 240 min).(ABSTRACT TRUNCATED AT 250 WORDS)
Direct measurement of free Ca in organelles of gastric epithelial cells
Authors: Hofer A. M. , Machen T. E.
Published: December 2017

When loaded as the acetoxymethyl ester (AM) derivative, the fluorescent probe mag-fura 2 accumulates in both the cytoplasm and the subcellular compartments. The relatively high dissociation constant of this dye for Ca (53 microM) permits the measurement of changes in the free concentration of this ion in a variety of organelles where Ca concentration ([Ca]) is high. To characterize Ca stores in gastric cells, we used digitonin to permeabilize cells within isolated rabbit gastric glands loaded with mag-fura 2-AM. This allowed cytosolic dye to leak out, leaving only compartmentalized dye behind. It appears that mag-fura 2 monitors [Ca] changes in several ATP-dependent Ca-sequestering pools; an inositol 1,4,5-trisphosphate (IP3)-releasable and thapsigargin-sensitive store (which probably includes the endoplasmic reticulum), a pool that is released by the mitochondrial inhibitors oligomycin+azide, valinomycin, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone, and ruthenium red (and therefore likely represents mitochondria), and a residual pool that was resistant to release by mitochondrial inhibitors and thapsigargin. Ca sequestration into all pools was sensitive to changes in [ATP], indicating that treatments that reduce cellular [ATP] will cause certain organelles to lose their Ca to the cytoplasm. Caffeine and ryanodine, which mobilize Ca from internal stores in many cell types, induced Ca sequestration into an IP3-insensitive store of gastric cells, and caffeine caused a reduction in cytoplasmic [Ca] (as measured with fura 2). We also show that the quantitation of free [Ca] in a given pool is complicated by a nonlinearity in the relationship between the mag-fura 2 ratio and [Ca]. This effect is likely a consequence of monitoring the fluorescence from multiple pools simultaneously. However, this limitation does not detract from the ability of this method to yield important qualitative information about the nature and number of Ca stores within single gastric cells.
Corelease of neuropeptides from capsaicin-sensitive afferents dilates submucosal arterioles in guinea pig ileum
Authors: Vanner S.
Published: December 2017

Extrinsic sensory afferent nerves projecting to the guinea pig intestinal submucosal arterioles contain both substance P (SP) and calcitonin gene-related peptide (CGRP); selective stimulation of these nerves causes vasodilation. However, it is not known whether either or both of these neuropeptides may be responsible for this neurogenic vasodilation. To examine this question, the actions of selective SP and CGRP antagonists on vasodilations evoked by SP, CGRP, and selective stimulation of extrinsic sensory afferents with capsaicin were measured in isolated submucosal arteriolar preparations with videomicroscopy. The SP receptor antagonist CP-96,345 (200 nM) abolished the vasodilation produced by half-maximal concentration (EC50) of SP and was without effect on the vasodilation produced by EC50 concentration of CGRP. Conversely, the CGRP receptor antagonist, CGRP-(8--37) (1 microM) abolished the vasodilation to CGRP but did not alter the SP-induced vasodilation. Neither antagonist altered the muscarinic vasodilation or nerve-evoked sympathetic vasoconstriction. Maximum inhibition of the capsaicin-induced vasodilation by CP-96,345 (600 nM) was 67%, and maximum inhibition of this response by CGRP-(8--37) (2 microM) was 53%. Complete inhibition of the capsaicin-induced vasodilation occurred when both antagonists were present. It is concluded that the vasodilation in response to activation of extrinsic sensory afferents innervating submucosal arterioles is due to the corelease of SP and CGRP.
Secretin: a physiological regulator of gastric emptying and acid output in dogs
Authors: Jin H. O. , Lee K. Y. , Chang T. M. , Chey W. Y. , Dubois A.
Published: December 2017

Secretin has been known to inhibit gastric acid secretion in several species. However, the physiological role of secretin on the postprandial acid output and gastric emptying in an intact stomach remains controversial. In the present study, we reinvestigated the role of secretin in physiological dose range and endogenous secretin on gastric acid secretion and emptying in the stomach without influencing intragastric luminal pH in dogs. In seven conscious dogs with gastric cannulas, a 4% amino acid meal was administered intragastrically, and three different doses of secretin and an antisecretin serum were infused intravenously in each dog on separate days. Gastric emptying and net acid output were measured using a dye dilution technique, and plasma secretin and gastrin were determined by specific radioimmunoassays. After the meal, gastric emptying was exponential: acid output peaked at 25 min, and plasma concentrations of gastrin and secretin peaked at 15 and 60 min, respectively. Intravenous infusion of secretin at 1.25, 2.5, and 5.0 pmol.kg-1.h-1 dose dependently increased plasma levels of the peptide and suppressed postprandial plasma gastrin response and gastric acid output and emptying of the meal. Immunoneutralization of circulating secretin with a rabbit antisecretin serum abolished the postprandial rise of plasma secretin and significantly increased plasma gastrin, and augmented gastric emptying as well as acid output. It is concluded that, in dogs, secretin plays a physiological role in the regulation of gastric emptying and acid output after a liquid amino acid meal and that these effects may be mediated in part by suppression of the release of gastrin.