bluuebunny/crossref_metadata_2025 huggingface dataset:
Age-related differences in intestinal microvascular responses to low-flow states in adult and suckling rats
Authors: Gosche J. R. , Harris P. D. , Garrison R. N.
Published: December 2017

We used in vivo videomicroscopic techniques to compare the intestinal microvascular responses of 8- to 12-wk-old adult rats with those observed in 8- to 12-day-old suckling rats. Changes in intestinal microarteriolar diameters and blood flow were measured during hemorrhage (5 and 10 ml/kg), hypoxia (10% O2 breathing environment), and hypothermia (surface cooling to 34 degrees C and 31 degrees C). Intestinal blood flow (as measured by optical Doppler velocimetry) was decreased by a similar amount in both adult and suckling rats during all three periods of stress. Large arteriolar diameter changes were also similar in adult and suckling rats. In contrast, there were substantial differences in the responses of the small premucosal arterioles. These premucosal arterioles selectively dilated in adult rats, suggesting a redistribution of blood flow toward the mucosa during each of the three periods of stress. These same microvessels failed to dilate in the suckling rats during each of the three periods of stress, suggesting that the intestinal microvasculature in the immature rat lacks vasodilator mechanisms that are active in the adult rat. We propose that altered microvascular control could make the developing intestine prone to mucosal damage during periods of decreased perfusion.
Beta-adrenergic inhibition of electrical and mechanical activity in canine colon: role of cAMP
Authors: Smith T. K. , Ward S. M. , Zhang L. , Buxton I. L. , Gerthoffer W. T. , Sanders K. M. , Keef K. D.
Published: December 2017

The effects of beta-adrenergic receptor stimulation on the electrical and mechanical activity of canine colonic circular muscles were compared with forskolin (Fsk), a known stimulator of adenylate cyclase. The actions of isoproterenol (Iso) were mediated by beta 2-receptors. Iso and Fsk increased intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels in both the presence and absence of acetylcholine (ACh), whereas ACh (0.3 microM) alone reduced cAMP levels. These agents caused inhibition of spontaneous and ACh-induced contractions. Inhibition was associated with a reduction in the amplitude and duration of electrical slow waves recorded near the submucosal border. Near the myenteric border, Iso and Fsk hyperpolarized the membrane by up to 30 mV and changed the pattern of electrical rhythmicity. These effects were mimicked by 8-bromo-cAMP (1-3 mM). Contractile inhibition with Fsk and Iso was associated with a decrease in the amplitude and duration of Ca2+ transients measured with fura-2 fluorescence. cAMP (10-300 microM) reduced the Ca2+ sensitivity of the contractile apparatus in muscles permeabilized with staphylococcal alpha-toxin. The actions of Iso appear linked to cAMP. We hypothesize that cAMP produces relaxation both by modulation of membrane ionic channels with a consequent decline in the entry of Ca2+ as well as through a decrease in the sensitivity of the contractile apparatus to Ca2+.
Hepatic intracellular pH during the prereplicative period following partial hepatectomy
Authors: Le Couteur D. G. , Rivory L. P. , Pond S. M.
Published: December 2017

To investigate the hypothesis that the regenerating liver undergoes intracellular alkalinization during the prereplicative period, we measured intracellular pH (pHi) after partial hepatectomy in the rat. pHi was studied in livers from female Wistar rats perfused in situ with buffer containing HCO3-/CO2. The multiple indicator-dilution technique was used to determine pHi from the distribution volume of dimethyloxazolidine-2,4-dione (DMO). Perfusion conditions influenced pHi. There was a curvilinear relationship between pHi and flow rate and a linear relationship between pHi and temperature. Under equivalent perfusion conditions there were no significant differences between pHi in normal livers (7.27 +/- 0.02) and that following partial hepatectomy (7.27 +/- 0.03 at 0 h, 7.27 +/- 0.04 at 4 h, 7.28 +/- 0.03 at 8 h, and 7.31 +/- 0.02 at 24 h) or sham surgery (7.27 +/- 0.04 at 4 h, 7.33 +/- 0.08 at 24 h). Therefore intracellular alkalinization does not occur following partial hepatectomy and is unlikely to be a signal for regeneration.
Pancreatic acini possess endothelin receptors whose internalization is regulated by PLC-activating agents
Authors: Hildebrand P. , Mrozinski J. E. , Mantey S. A. , Patto R. J. , Jensen R. T.
Published: December 2017

Endothelin-1 (ET-1) and ET-3 mRNA have been found in the pancreas. We investigated the ability of ET-1, ET-2, and ET-3 to interact with and alter dispersed rat pancreatic acinar cell function. Radiolabeled ETs bound in a time- and temperature-dependent fashion, which was specific and saturable. Analysis demonstrated two classes of receptors, one class (ETA receptor) had a high affinity for ET-1 but a low affinity for ET-3, and the other class (ETB receptor) had equally high affinities for ET-1 and ET-3. No specific receptor for ET-2 was identified. Pancreatic secretagogues that activate phospholipase C (PLC) inhibited binding of 125I-labeled ET-1 (125I-ET-1) or 125I-ET-3, whereas agents that act through adenosine 3',5'-cyclic monophosphate (cAMP) did not. A23187 had no effect on 125I-ET-1 or 125I-ET-3 binding, whereas the phorbol ester 12-O-tetradecanoylphorbol 13-acetate reduced binding. The effect of cholecystokinin octapeptide (CCK-8) was mediated through its own receptor. Stripping of surface bound ligand studies demonstrated that both 125I-labeled ET-1 and 125I-labeled ET-3 were rapidly internalized. CCK-8 decreased the internalization but did not change the amount of surface bound ligand. Endothelins neither stimulate nor alter changes in enzyme secretion, intracellular calcium, cAMP, or [3H]inositol trisphosphate (IP3). This study demonstrates the presence of ETA and ETB receptors on rat pancreatic acini; occupation of both receptors resulted in rapid internalization, which is regulated by PLC-activating secretagogues. Occupation of either ET receptor did not alter intracellular calcium, cAMP, IP3, or stimulate amylase release.
Calcium-dependent regulation of cholecystokinin secretion and potassium currents in STC-1 cells
Authors: Mangel A. W. , Snow N. D. , Misukonis M. A. , Basavappa S. , Middleton J. P. , Fitz J. G. , Liddle R. A.
Published: December 2017

Secretory and electrophysiological properties of STC-1 cells, a cholecystokinin-secreting cell line, were examined with a radioimmunoassay and patch-clamp recording techniques. Stimulation of cholecystokinin secretion was seen after exposure to agents anticipated to increase the level of intracellular calcium, including thapsigargin (8 microM), bombesin (50 nM), potassium-induced depolarization (50 mM), or after blockade of potassium channels with barium chloride (2 mM). The secretory effects of these agents were blocked by pretreatment with the calcium channel blocker diltiazem (1 microM). Whole cell patch-clamp recordings showed a hyperpolarizing shift in reversal potential after exposure to either thapsigargin (8 microM) or bombesin (50 nM) from a control value of -27 +/- 3 to -57 +/- 7 or -48 +/- 6 mV, respectively. This shift was in the direction of the reversal potential for potassium and was blocked by barium chloride (5 mM). Single-channel recordings from cell-attached membrane patches showed an inwardly rectifying potassium channel with channel open probability modulated by bombesin. These results indicate that in STC-1 cells a potassium current is increased by agents that stimulate CCK secretion, presumably by increasing the level of cytosolic calcium. STC-1 cells may serve as a model system to study the electrophysiological and secretory mechanisms involved in the release of cholecystokinin.
Importance of high-density lipoprotein-phosphatidylcholine in secretion of phospholipid and cholesterol in bile
Authors: Portal I. , Clerc T. , Sbarra V. , Portugal H. , Pauli A. M. , Lafont H. , Tuchweber B. , Yousef I. , Chanussot F.
Published: December 2017

The purpose of this work was to evaluate biliary phosphatidylcholine (PC) secretion after intravenous infusion of high density lipoprotein (HDL)-[3H]phosphatidylcholine (HDL-[3H]PC) in rats and to study the effect of infusion of dehydrocholic and cholic acids, which, respectively, inhibit and stimulate biliary secretion of PC. The data obtained in this study showed that, in the basal state, HDL-PC accounted for 38% of biliary PC. Dehydrocholic acid infusion caused only a "residual" secretion of HDL-PC in the bile; however, cholic acid infusion stimulated the secretion of HDL-PC as well as PC from intrahepatic microsomes. The low level of radioactivity of HDL-PC in intrahepatic compartments suggests that HDL-PC taken up by the liver is predestined for the bile secretion. The correlation between the kinetics of bile secretion of HDL-cholesterol and HDL-[3H]PC suggests the importance of HDL-PC in reverse transport of cholesterol to the liver and its transport to the bile. The differences between the effects of dehydrocholic acid and cholic acid infusions can be explained by the differences in bile salts binding to the surface of HDL.
Mucin secretion by T84 cells: stimulation by PKC, Ca2+, and a protein kinase activated by Ca2+ ionophore
Authors: Forstner G. , Zhang Y. , McCool D. , Forstner J.
Published: December 2017

T84 adenocarcinoma cells were stimulated to secrete mucin by the phorbol ester phorbol 12-myristate 13-acetate (PMA) and Ca2+ ionophores A23187 and ionomycin. In Ca(2+)-containing media, maximal stimulation by PMA was significantly inhibited by staurosporine, but maximal A23187-stimulated secretion was not affected. Downregulation of protein kinase C (PKC) reduced maximal PMA-stimulated secretion without affecting the response to A23187. Thus PKC activation is not required for maximal Ca(2+)-mediated mucin secretion. PMA stimulated secretion in low-Ca2+ media, with and without intracellular chelation of Ca2+ by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Surprisingly, Ca2+ ionophores also stimulated secretion under the same circumstances. Persistent A23187-stimulated secretion was strongly inhibited by the protein kinase inhibitors staurosporine and H-7. Secretion in Ca(2+)-containing media was also inhibited at submaximal levels of Ca(2+)-ionophore stimulation. These results indicate that PKC and Ca2+ stimulate mucin exocytosis independently. Ca2+ ionophores also stimulate secretion via a protein-kinase dependent pathway. Enhancement of protein kinase inhibition at lower Ca2+ concentrations suggests that the response could be mediated by a Ca2+ ionophore-induced depletion of an intracellular Ca2+ pool.
Intestinal adaptation during lactation in the mouse. II. Altered intestinal processing of a dietary protein
Authors: Harmatz P. R. , Carrington P. W. , Giovino-Barry V. , Hatz R. A. , Bloch K. J.
Published: December 2017

We previously demonstrated in lactating mice a six- to eightfold increase in the intestinal uptake of the dietary protein, ovalbumin (OVA), administered by gavage. In this study, we tested the possibility that alterations in intestinal morphology, transit time, reduced luminal proteolysis, and enhanced association with the intestinal surface might account for the increased uptake of the protein observed in lactating mice. We found that these animals had a significant increase in length, wet weight, and surface area of the small intestine. No change in the number of Peyer's patches was noted. Intestinal transit was assessed by gavage administration of 125I-OVA and 10 mg OVA and localization of the peak of radioactivity 15, 30, and 60 min after feeding. Although motility (distance traveled per unit time) was not different in lactating and control mice at 15 and 30 min, the fraction of the small intestine traversed by the peak of radioactivity was less in lactating mice. Digestion of 125I-OVA administered by gavage with 10 mg unlabeled OVA was examined by trichloroacetic acid precipitation and gel permeation of the resulting fragments. Lactating and control mice did not show differences in digestion of 125I-OVA by either measurement. The association of 125I-OVA with small intestinal segments, however, was enhanced in lactating mice, especially in the second and third segments of the small intestine. Thus several factors including an increase in length and surface area of the small intestine, prolonged contact of protein with the small intestinal absorptive surface, and enhanced association of the protein with the intestinal surface contribute to increased uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
Macrophage activation and leukocyte adhesion after liver transplantation
Authors: Marzi I. , Walcher F. , Buhren V.
Published: December 2017

Reperfusion injury involving oxygen radicals, leukocyte adhesion, and Kupffer cell activation has been suggested to contribute to the failure of transplanted livers. The aim of this study was to evaluate Kupffer cell activity, leukocyte adhesion, and the effect of the calcium channel blocker nisoldipine after rat liver transplantation by means of in vivo fluorescence microscopy to further investigate the mechanism of graft failure. Inclusion of 1.4 microM nisoldipine to the University of Wisconsin cold storage solution (UW) did not improve sinusoidal perfusion and vasoconstriction after transplantation compared with UW alone (82.7 +/- 1.0% vs. 79.2 +/- 1.7% perfused sinusoids; 7.3 +/- 0.1 vs. 8.0 +/- 0.2 microns diam of sinusoids; means +/- SE). Permanent as well as temporary adhesion of leukocytes rose from 9.4 +/- 0.8 and 10.2 +/- 0.5% in sham-operated controls to 19.1 +/- 2.2 and 19.2 +/- 0.5% after liver transplantation, respectively. Inclusion of the calcium channel blocker reduced permanent (9.1 +/- 0.8%; P < 0.05) and temporary adherent leukocytes (11.3 +/- 1.0%; P < 0.05). Phagocytosis of latex beads by Kupffer cells or other phagocytic cells as a function of activity rose after transplantation (e.g., periportal area: 509 +/- 44/mm2) compared with controls (316 +/- 22/mm2). This was significantly reduced by inclusion of nisoldipine to UW (322 +/- 32/mm2). The results of this study demonstrate activation of Kupffer cells and increase of leukocyte adhesion to the sinusoidal endothelial wall during reperfusion of transplanted livers. A calcium-dependent release of mediators by Kupffer cells that promote leukocyte adhesion is suggested as an underlying mechanism.
Cellular localization and hormonal regulation of pancreatic intrinsic factor secretion in dogs
Authors: Simpson K. W. , Alpers D. H. , De Wille J. , Swanson P. , Farmer S. , Sherding R. G.
Published: December 2017

Gastric mucosal cells are considered to be the principal site of intrinsic factor (IF) production in most mammals. Recent observations in dogs suggest that the pancreas is the major site of IF production in this species. The present study was undertaken to determine the cellular origins of canine pancreatic IF by combining in situ hybridization with immunocytochemistry and to examine the potential role of physiological pancreatic secretagogues, cholecystokinin octapeptide (CCK-8) and secretin, as mediators of canine pancreatic IF secretion. A human IF cDNA probe (J. Hewitt et al., Genomics 10: 432-440, 1991), validated for use in the dog, identified IF mRNA in parietal cells in the gastric fundus, gastric gland cells in the pyloric antrum, and in secretory duct cells of the pancreas. Immunocytochemistry using antibody against rat IF confirmed that these cells, as well as secretory ducts of salivary glands, synthesized an immunoreactive protein. In stimulated secretions of anesthetized dogs, mean 45-min outputs of IF, haptocorrin, and trypsinogen were 13-, 8-, and 16-fold greater during stimulation with CCK-8 than with secretin. No synergistic effects of combined stimulation were observed for IF or haptocorrin, although a synergistic effect was observed for trypsinogen. These findings demonstrate that IF is synthesized in the canine stomach, pancreas, and probably salivary glands and that CCK-8 mediates IF secretion from pancreatic duct cells.
Responses of the human esophagus to experimental intraluminal distension
Authors: Williams D. , Thompson D. G. , Heggie L. , Bancewicz J.
Published: December 2017

Contractile and propulsive forces generated in response to intraluminal distension of the human esophagus were measured in 30 volunteers with the use of a novel intraluminal catheter assembly. Distension was achieved by graded inflation of a balloon for periods of 30 s using volumes of air varying between 0 and 12 ml. In the lower esophagus, distension above a threshold volume of 5 (3-10) ml (median and interquartile range) induced a traction force together with contractile activity proximal to the balloon and quiescence distally. Proximal contractile activity and aboral traction force increased with increasing inflation volume, the magnitude of the response being additionally dependent on the site and the length of esophageal wall stimulated. Although the threshold for induction of motor responses was similar at different distension sites, the magnitude of both contractile and traction responses was higher in the distal than in the midesophagus. In the upper esophagus, the contractions induced proximal to the distension propagated aborally, whereas in the lower esophagus nonpropagating proximal contractions were induced. With the use of a dual balloon technique, it was possible to demonstrate that the distal quiescence represented a true descending inhibitory response since inflation of a proximal balloon suppressed the contractile response induced by a distal balloon. These results thus provide a description of the human esophageal response to distension against which responses in disease states can be compared.
Physiological and morphological properties of neurons in sphincter of Oddi region of the guinea pig
Authors: Wells D. G. , Mawe G. M.
Published: December 2017

Intracellular recordings and dye injections were used to investigate neurons located in ganglia of the sphincter of Oddi (SO) region in guinea pigs. Four types of neurons were encountered based on physiological properties. The two most abundant types, tonic and phasic, had similar membrane characteristics and morphologies but yet could be differentiated by their spiking characteristics. Tonic cells spiked throughout a depolarizing current pulse and were sometimes spontaneously active. Phasic cells fired only a single action potential at the onset of a current pulse regardless of stimulus amplitude or duration. Both tonic and phasic cells had Dogiel type I morphologies. They typically had a single long process and several very short processes emanating from the soma. NADPH diaphorase activity was demonstrated in cells with similar morphologies, indicating that nitric oxide may be an intrinsic transmitter in some of these cells. Cells with a prolonged afterhyperpolarization (AH cells), similar to the type 1/AH cells of the gut, were rarely encountered. This finding was consistent with the observation that very few calbindin D-immunoreactive neurons exist in this region. Action potentials could not be generated in the fourth type of neuron, called nonspiking neurons, even though they did receive synaptic input. Most tonic and phasic cells received at least one nicotinic fast excitatory postsynaptic potential (EPSP). In addition, both slow EPSPs and inhibitory postsynaptic potentials were observed. Most AH cells received only slow excitatory synaptic input.
Altered jejunal potassium (Rb+) transport in piglet rotavirus enteritis
Authors: Woodard J. P. , Chen W. , Keku E. O. , Liu S. C. , Lecce J. G. , Rhoads J. M.
Published: December 2017

To determine the mechanisms of K+ loss in viral diarrhea, K+ fluxes (estimated by tracer Rb+ flows) across piglet jejunum in Ussing chambers were determined. Normal jejunum was characterized by an indomethacin-sensitive short-circuit current and a small K+ secretory flow. Rotavirus-infected gut secreted K+ at high rates, probably resulting from increased prostaglandin generation because secretion was abolished by indomethacin. Tissues pretreated with indomethacin responded to 8-bromoadenosine 3',5'-cyclic monophosphate acid and 16,16-dimethyl-prostaglandin E2 with K+ secretion. The secretory response in rotavirus-infected jejunum was no greater than that in normal tissue. Serosal addition of Ca2+ ionophore A23187 caused K+ secretion in normal but not rotavirus-infected jejunum. To inhibit the basolateral uptake of K+ and reduce the driving force for secretion, ouabain was added to the bath. Ouabain unmasked a K+ absorptive process in normal intestine, which was not seen in rotavirus-infected tissue. K+ absorption was inhibited by 3-(cyanomethyl)-2-methyl-8-(phenyl-methoxy)imidazo (1,2 alpha)pyridine (Sch-28080) and omeprazole. We speculate that the high fecal K+ losses observed in human rotavirus enteritis might be caused by an imbalance between K+ secretion and an impaired apical K+ absorptive mechanism in the crypt-type epithelium.
Direct and indirect mechanosensory pathways from the colon to the inferior mesenteric ganglion
Authors: Parkman H. P. , Ma R. C. , Stapelfeldt W. H. , Szurszewski J. H.
Published: December 2017

The aims of these experiments were to determine in vitro whether colonic distension releases acetylcholine, vasoactive intestinal polypeptide (VIP), and substance P in the guinea pig inferior mesenteric ganglia (IMG) and whether cholinergic and peptidergic mechanosensory nerves projecting from the colon to the IMG receive cholinergic input from other enteric neurons. Colonic distension significantly increased the release of [3H]-acetylcholine, VIP-like immunoreactivity, and substance P-like immunoreactivity in the IMG. Nicotinic receptor blockade in the colon diminished the increase in [3H]acetylcholine release, abolished the increase in VIP-like immunoreactivity release during distension, but had no effect on the release of substance P-like immunoreactivity. Nicotinic receptor blockade in the colon also decreased fast mechanosensory input and significantly reduced by 54% the slow excitatory postsynaptic potential amplitude evoked by colonic distension. The data suggest that enteric cholinergic and VIP mechanosensory neurons that project from the colon to sympathetic neurons in the IMG receive peripheral cholinergic input from other enteric neurons. There was no evidence for enteric cholinergic input to the mechanosensory substance P pathway.
Transcriptional and posttranscriptional control in synthesis of growth marker polypeptides in mouse parotids
Authors: Lopez Solis R. O. , Gonzalez M. J. , Castillo L. , Pena y Lillo S. , Alliende C.
Published: December 2017

The chronic daily administration of isoproterenol provokes in mouse parotid glands the induction and progressive accumulation of a family of secretory polypeptides named polypeptides C, D, E, F, and G (polypeptides C-G). These polypeptides, which seem to be part of the family of proline-rich proteins, have been considered as molecular markers of the growth-in-size response in the mouse parotid acinar cells. In the present study, two pharmacological approaches were used to determine whether the induction and the postsecretory reappearance of polypeptides C-G may be distinguished from each other. First, actinomycin D, a transcriptional inhibitor, was found to interfere with the induction by isoproterenol but not with the postsecretory reappearance. Second, pilocarpine, a secretagogue that was found to be a very weak inducer of polypeptides C-G, was able to provoke secretion and then reappearance of the whole group of isoproterenol-induced polypeptides. Accordingly, these data suggest that the induction of polypeptides C-G is dependent on transcriptional activity and that it is unrelated to secretion stimulation. By contrast, the postsecretory reappearance of polypeptides C-G may occur even when transcriptional activity is inhibited and it would be related to the secretory activity.
Duodenal acid-induced inhibition of gastric motility and emptying in rats
Authors: Raybould H. E. , Holzer H. H.
Published: December 2017

The mechanism by which acid in the duodenum inhibits proximal gastric motor function and delays emptying was investigated in urethan-anesthetized and awake rats. Gastric motility inhibited by duodenal acid (0.2 N HCl) in urethan-anesthetized rats was attenuated by 68 and 54%, respectively, by functional ablation of the vagal or spinal sensory innervation with capsaicin. 5-Hydroxytryptamine3 receptor blockade with zacopride (0.2 mg/kg ip) or cholecystokinin (CCK)-A-type receptor blockade with MK-329 (1 mg/kg ip) had no effect on the motility response to acid. In awake rats with chronically implanted gastric and duodenal cannulas, perfusion of the duodenum with acid (0.1 and 0.2 N HCl) inhibited gastric emptying of a nonnutrient liquid (38 and 59%, respectively). Blockade of CCK-A-type receptors reduced by 30% inhibition of gastric emptying induced by 0.1 N HCl. However, functional ablation of the vagal or spinal sensory innervation, 5-hydroxytryptamine3 receptor blockade, or immunoneutralization of secretin by systemic administration of a polyclonal antibody (no. 7842, 1 ml ip) had no effect on acid-induced (0.1 N HCl) inhibition of gastric emptying. Perfusion of the duodenum with 0.2 N HCl but not 0.1 N HCl inhibited proximal gastric motility in awake rats. These results suggest that 1) a duodenal acid load inhibits gastric emptying in part by a mechanism involving CCK and 2) decreased proximal gastric motility plays a minor role in inhibition of gastric emptying in response to acid.
Gastrointestinal transit is not impaired by regional loss of myenteric neurons in rat jejunum
Authors: Luck M. S. , White J. C. , Bass P.
Published: December 2017

Chronic absence of myenteric neurons from a 5-cm segment of rat jejunum causes alterations in myoelectric activity. Spike potentials characteristic of phase III activity of the migrating motor complex (MMC) are present; however, the number of propagating spike potentials through the myenterically denervated region is reduced. The objective of this study was to examine the effect of the regional loss of myenteric neurons on gastrointestinal transit of a solid marker in the fasted rat. The rate of gastric emptying was not affected by the absence of the myenteric plexus in a 5-cm segment of the jejunum. However, 15 days after either myenteric denervation or vehicle treatment of a segment of jejunum, a more cephalad distribution and decreased rate of intestinal propulsion of the solid marker was observed in the small intestine. This delay in small intestinal transit observed at 15 days was not seen at 48 and 120 days. The decrease in transit at 15 days can be attributed to the handling of the bowel during the surgical procedure. The mouth-to-cecum transit time (MCT) was also not affected by chronic absence of the myenteric plexus. Furthermore, the MCT indicated that bacterial overgrowth, a common manifestation when gut motility is disrupted, did not occur in the small intestine after the experimental destruction of the myenteric plexus. The results of this study indicate that the regional loss of the myenteric plexus does not impair gastrointestinal transit in the fasted rat.(ABSTRACT TRUNCATED AT 250 WORDS)
Opposing gastric motor responses to TRH and substance P on their microinjection into nucleus raphe obscurus of rats
Authors: Krowicki Z. K. , Hornby P. J.
Published: December 2017

Little is known about the functional role of putative neurotransmitters in the nucleus raphe obscurus (NRO) in the control of gastric motor function, although thyrotropin-releasing hormone (TRH) and substance P (SP) have been detected in the cell bodies and/or fibers of this nucleus. Therefore, we investigated the effects of microinjection of these peptides (in a volume of 60 nl) into the caudal NRO of alpha-chloralose-anesthetized rats while recording intragastric pressure, pyloric and greater curvature motility, and blood pressure. L-Glutamate (30 nmol) was first microinjected into the NRO to identify the "gastric" region of the NRO and elicited significant increases in intragastric pressure as well as pyloric and greater curvature motility in all 16 animals. TRH (2-45 pmol, n = 16) microinjected into the same sites increased intragastric pressure as well as pyloric and greater curvature motility, and these effects were abolished by bilateral cervical vagotomy and atropine (0.5-1.0 mg/kg iv) but not by spinal cord transection. Microinjection of SP (45-405 pmol, n = 15) into the same sites decreased intragastric pressure; however, the inhibitory effect of SP on pyloric and greater curvature motility did not attain statistical significance. The effect of SP on intragastric pressure was completely abolished by bilateral vagotomy but not by systemic administration of atropine (1 mg/kg) or spinal cord transection. Microinjections of 45 pmol TRH and 405 pmol SP just outside of the NRO did not result in changes in gastric function. No overall significant changes in blood pressure were noted after microinjection of L-glutamate, TRH, or SP into the gastric region of the NRO. We conclude that both TRH and SP affect gastric motor function in the caudal NRO via a vagally mediated pathway; TRH apparently activates vagal cholinergic pathways, but the mechanism of SP-evoked gastric motor inhibition remains to be further investigated.
TRH in dorsal vagal complex mediates acid response to excitation of raphe pallidus neurons in rats
Authors: Yang H. , Ohning G. , Tache Y.
Published: December 2017

The role of thyrotropin-releasing hormone (TRH) in the dorsal vagal complex (DVC) in the acid response to excitation of raphe pallidus neurons was investigated in urethan-anesthetized rats with gastric fistula. Kainic acid (0.19 microgram/30 nl) microinjected into the raphe pallidus stimulated gastric acid secretion. The response was prevented by vagotomy. A specific polyclonal TRH antibody, 8964, was raised and characterized (50% inhibitory dose for TRH was 80 pg/ml at an antibody final dilution of 1:10(5)). The TRH antibody injected intracisternally blocked the acid response to intracisternal TRH, but not that of the TRH analogue RX-77368. The TRH antibody (0.33, 0.65, or 1.3 micrograms.100 nl-1.site-1) microinjected bilaterally into the DVC prevented dose dependently by 31, 60, and 76%, respectively, the increase in acid secretion induced by kainic acid injected into the raphe pallidus. The TRH antibody (1.3 microgram/site) microinjected into medullary sites outside of the DVC had no effect. These data indicate that excitation of raphe pallidus neurons induces a vagal-dependent stimulation of gastric acid secretion that is mediated by endogenous TRH in the DVC. TRH neurons in the raphe pallidus projecting to the DVC may have a physiological relevance in the vagal regulation of gastric function.
Characterization of bumetanide transport in isolated skate hepatocytes
Authors: Blumrich M. , Petzinger E. , Boyer J. L.
Published: December 2017

The uptake of [3H]bumetanide was studied in isolated skate hepatocytes in an albumin-free elasmobranch Ringer solution and compared with the uptake of bile acids in the presence of other cholephilic organic anions. [3H]bumetanide uptake was energy dependent, temperature sensitive, and exhibited saturation kinetics. In contrast to taurocholate and cholate, which are transported only by Na(+)-independent mechanisms, removal of Na+ reduced the maximal uptake rate (Vmax) for bumetanide from 404 +/- 80 to 230 +/- 47 pmol.mg-1 x min-1 without a change in the apparent Michaelis constant (Km). The apparent Km for the Na(+)-dependent portion of bumetanide uptake was 58 +/- 24 microM, and Vmax was 151 +/- 38 pmol.min-1 x mg-1. Taurocholate (100 and 200 microM) inhibited Na(+)-independent bumetanide transport competitively but was a noncompetitive inhibitor for Na(+)-dependent bumetanide uptake. Furosemide (100 microM) and two bumetanide analogues, PF-3034 (500 microM) and PF-2203 (500 microM), preferentially inhibited the Na(+)-dependent bumetanide uptake system, whereas cholate (100 microM) and probenecid (100 microM) preferentially inhibited Na(+)-independent bumetanide transport. The sulfhydryl (SH) reagents N-ethylmaleimide, 2,2'-dithio-bis(5-nitropyridine), and p-chloromercuribenzenesulfonic acid (PCMBS) inhibited both bile acid and bumetanide uptake. Dithiothreitol (500 microM) completely reversed the PCMBS-induced inhibition of bumetanide uptake. These results indicate that bumetanide is transported into hepatocytes of the small skate, Raja erinacea, by both Na(+)-dependent and Na(+)-independent mechanisms; the latter is shared by bile acids and probably sulfobromophthalein and other organic anions. Their uptake requires free SH groups.
Cotransport of 2-methyl-aminoisobutyric acid and chloride in rabbit small intestine
Authors: Munck L. K.
Published: December 2017

This article examines the nature of the Cl- dependence of the rabbit intestinal imino acid carrier using 2-methyl-aminoisobutyric acid (MeAIB) as substrate for measuring influx across the luminal membrane of rabbit distal ileum. Reduction of mucosal Cl- concentration from 140 to 6 mM successively increased the concentration at which MeAIB influx is half-maximal from 3.6 +/- 0.2 (SD) to 21.0 +/- 3.7 mM. Maximal influx of MeAIB was unchanged. Measured at 70 mM Cl-, MeAIB induced a Cl- influx across the brush-border membrane (delta JClmc) of 5.01 +/- 0.65 mumol.cm-2 x h-1 (SE, n = 16; 45%), and an identical Cl(-)-independent influx of leucine induced a delta JClmc of 1.82 +/- 0.52 mumol.cm-2 x h-1 (SE, n = 12; 16%) (P < 0.001). At 24 mM Cl-, delta JClmc induced by leucine did not differ significantly from zero, whereas the effect of MeAIB was maintained. The ratio between Na+ influx across brush-border membrane (delta JNamc) and the Na(+)-dependent flux measured at 140 mM Cl- was 2.4 +/- 0.7 (n = 8) for MeAIB, 1.4 +/- 0.4 (n = 10) for leucine, and 1.1 +/- 0.2 (n = 13) for D-glucose. The Hill coefficient of Na+ activation (+/- SD) in distal ileum was 0.82 +/- 0.19 for leucine and 1.14 +/- 0.03 for D-glucose. A Hill coefficient of 1.60 +/- 0.05 was obtained for D-glucose in the jejunum. Concentrations of MeAIB and D-glucose, chosen to given equal delta JNamc, induced a 40 and 21% increment of JClmc (P < 0.05), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of vagotomy on ornithine decarboxylase activity in rat duodenal mucosa
Authors: Tanaka J. , Fujimoto K. , Sakata T. , Fujimoto T. , Tsunada S. , Iwakiri R. , Yamaguchi M. , Okabe Y. , Yoshimatsu H.
Published: December 2017

The aim of this study was to determine whether the circadian rhythm of ornithine decarboxylase (ODC) activity in rat small intestine is controlled by factors other than luminal nutrients. ODC activity in duodenal and jejunal mucosa of rats fed ad libitum was measured at four time points (0500, 1100, 1700, 2300 h; light period: 0800-2000 h). ODC activity in the jejunum increased in the dark period, which is when rats normally eat. In contrast, ODC activity in the duodenum began to increase at 1700 h, which is when rats do not normally eat, as indicated by the recorded feeding pattern. The increase in ODC activity in the duodenum at 1700 h, but not at other time points, was abolished by subdiaphragmatic vagotomy, whereas vagotomy had no effect on the feeding pattern of rats. Subdiaphragmatic vagotomy had no effect on ODC activity in the jejunum. ODC activity in the duodenum increased following glycoprivation of the central nervous system induced by infusion of 2-deoxyglucose into the third cerebroventricle. These results indicate that the increase in duodenal ODC activity at 1700 h is due to a signal from the upper brain structure through the vagal nerve and not to luminal nutrient factors.
Autoregulation of histamine synthesis through H3 receptors in isolated fundic mucosal cells
Authors: Hollande F. , Bali J. P. , Magous R.
Published: December 2017

Histamine plays an important role in the control of gastric acid secretion by activating H2 receptors located on parietal cells. In gastric mucosa, histamine is stored both in mast cells and in enterochromaffin-like cells, especially in rodents. It has been proposed that histamine may regulate its own synthesis and/or release through receptors pharmacologically distinct from H1- and H2-receptor subtypes. In this article, we studied the regulation by histamine of histidine decarboxylase (HDC) activity (enzyme responsible for the formation of histamine by decarboxylation of L-histidine) in a fraction of isolated rabbit gastric mucosal cells enriched in mucous and endocrine cells. Histamine and (R)-alpha-methylhistamine (H3 receptor agonist) dose dependently inhibited HDC activity with the same potency (mean effective concn: 32.2 +/- 0.7 and 50.5 +/- 3.1 pM, respectively) and efficacy (35 and 36% inhibition, respectively). In contrast, the H2 agonist dimaprit was devoid of effect. The H3 antagonist thioperamide was found to decrease the histamine- or (R)-alpha-methylhistamine-induced inhibition of HDC activity (mean ineffective concn = 28.3 +/- 1.8 and 9.87 +/- 0.8 nM, respectively), whereas H1 (promethazine) and H2 (ranitidine) antagonists were unable to affect HDC activity. Moreover, high concentrations of thioperamide (1-10 microns) increased histamine release from these cells. All these results allowed us to conclude that, in gastric mucosa, histamine downregulates its own synthesis (and perhaps release) through the stimulation of autoreceptors with pharmacological characteristics of H3 receptors. However, the relationship between histamine synthesis and release remains unclear and needs further investigation.
Regenerative potential of abdominal vagal nerves in rats
Authors: Nanobashvili J. D. , Stacher G. , Windberger U. , Dudczak R. , Liegl C. , Gorgadze V. , Losert U. , Heinzl H. , Neumayer C.
Published: December 2017

After truncal vagotomy, impaired gastric emptying may represent a serious complication. This led us to study the feasibility of a reinnervation of the antrum by microsurgical vagorrhaphy and vagoplasty. Sixty-four rats were randomly assigned to undergo either 1) no operation (control), 2) laparotomy and vagal dissection (sham operation), 3) truncal abdominal vagotomy with nerve segment resection, 4) truncal vagotomy followed by vagorrhaphy, or 5) vagal resection extending to the nerve of Latarjet followed by grafting of the gap using the resected vagal segment (vagoplasty). Six months after surgery, vagal regeneration was assessed by morphometry of the anterior vagus and the antral wall and by recording the gastric emptying of a radiolabeled meal, the contractile response to electrical stimulation of the cervical vagi, and basal and insulin-stimulated acid secretion. After truncal vagotomy, there was a marked degeneration of vagal fibers and no evidence of spontaneous reinnervation. After vagorrhaphy, a recovery of gastric secretory and motor functions as well as morphological data indicated vagal regeneration. After vagoplasty, a partial recovery of gastric motor functions and the morphological appearance suggested a partial vagal reinnervation.
Mechanism of riboflavine uptake by Caco-2 human intestinal epithelial cells
Authors: Said H. M. , Ma T. Y.
Published: December 2017

The cellular and molecular regulation of intestinal absorption of the water-soluble vitamin riboflavine (RF) is poorly understood. The availability of a suitable in vitro cultured system that possesses the transport characteristics of the native intestinal absorptive cells would provide a powerful means to address this issue. In this study, we examined RF uptake by the human-derived cultured Caco-2 intestinal epithelial cells. RF uptake was Na+ and pH independent and occurred without metabolic alterations of the transported RF. Initial rate of RF uptake was temperature dependent and saturable as a function of concentration at 37 degrees C but not at 4 degrees C (apparent Michaelis constant = 0.30 +/- 0.03 microM, maximal velocity = 209.90 +/- 24.40 pmol.mg protein-1.3 min-1). Unlabeled RF, lumiflavine, 8-amino-riboflavine, isoriboflavine, and lumichrome in the incubation solution caused significant inhibition of RF uptake. RF uptake was also energy dependent and was sensitive to the inhibitory effect of sulfhydryl group reagents. The membrane transport inhibitor amiloride, but not 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, 4-acetamide-4'-isothiocyanostilbene-2,2'-disulfonic acid, furosemide, or probenecid, inhibited RF uptake in a competitive (inhibitory constant = 0.48 mM) and reversible manner. Growing Caco-2 monolayers in a RF-deficient and oversupplemented media caused significant up- and downregulation of RF uptake, respectively. These results demonstrate the existence of a carrier-mediated system for RF uptake by Caco-2 cells and provide new information regarding amiloride sensitivity, involvement of sulfhydryl groups, and up- and downregulation by the substrate level and clarify the controversy regarding the role of Na+ in the uptake process.(ABSTRACT TRUNCATED AT 250 WORDS).
Inhibition of nitric oxide synthase activity in dispersed gastric muscle cells by protein kinase C
Authors: Murthy K. S. , Jin J. G. , Makhlouf G. M.
Published: December 2017

The present study examined whether NO synthase (NOS) activity in gastric muscle cells was inhibited by protein kinase C (PKC). Vasoactive intestinal peptide (VIP) increased L-[3H]citrulline production (a coproduct and index of NO synthesis) in muscle strips (81.9 +/- 11.6%) and dispersed muscle cells (80.9 +/- 4.6%) of rabbit stomach. Cholecystokinin octapeptide (CCK-8), carbachol, and phorbol 12-myristate 13-acetate (PMA) inhibited VIP-induced L-[3H]citrulline production in muscle cells and muscle strips; the inhibition was reversed by pretreatment with the PKC inhibitor, calphostin C. The Ca(2+)-mobilizing agents, CCK-8, acetylcholine, ionomycin, and KCl, all of which increased PKC activity in dispersed muscle cells, did not increase L-[3H]citrulline production. After treatment of the cells with calphostin C, all four agents stimulated L-[3H]citrulline production, although to a lesser extent than VIP (approximately 50%). VIP-induced relaxation of basal but not carbachol-stimulated tension was accompanied by increase in L-[3H]citrulline production and was inhibited by the NOS inhibitor NG-nitro-L-arginine (L-NNA). Preincubation of carbachol-treated muscle strips with calphostin C restored the ability of VIP to stimulate L-[3H]citrulline production and the ability of L-NNA to inhibit VIP-induced relaxation. We conclude that 1) VIP-stimulated NOS activity is inhibited by agents that increase PKC activity in gastric smooth muscle cells, and 2) agents that increase both cytosolic free Ca2+ concentration and PKC activity stimulate NOS activity only when PKC activity is suppressed.
Serosal and cutaneous recordings of gastric myoelectrical activity in patients with gastroparesis
Authors: Chen J. D. , Schirmer B. D. , McCallum R. W.
Published: December 2017

The aims of this study were to 1) investigate gastric myoelectrical activity in patients with gastroparesis, 2) validate the cutaneous electrogastrogram (EGG) in tracking the frequency change of the gastric slow wave, and 3) investigate the effect of electrical stimulation on gastric myoelectrical activity. Gastric myoelectrical activity was recorded in 12 patients with documented gastroparesis using serosal electrodes for > 200 min in each subject. All recordings were made at least 4 days after surgery. Each session consisted of a 30-min recording in the fasting state and a 30-min recording after a test meal. The test meal (liquid or mixed) was selected according to patient's tolerance. Electrical stimulation was performed in three subjects via the serosal electrodes at a frequency of 3 cycles/min. Gastric myoelectrical activity was recorded using serosal electrodes in each session. The serosal recording showed slow waves of 2.5 to 4.0 cycles/min in all 12 subjects. Absence of spikes was noted in 11 of the 12 subjects. The simultaneous serosal and cutaneous recording of gastric myoelectrical activity showed that the frequency of the EGG was exactly the same as that of the serosal recording. Liquid meals resulted in a significant decrease in slow-wave frequency (Student's t test, P = 0.006), and the EGG accurately reflected this change. Electrical stimulation had no effect on the frequency of the gastric slow wave and did not induce spikes.(ABSTRACT TRUNCATED AT 250 WORDS)
Oxidative stress induces S-thiolation of specific proteins in cultured gastric mucosal cells
Authors: Rokutan K. , Johnston R. B. , Kawai K.
Published: December 2017

Oxidative stress induces the formation of protein-mixed disulfides with low-molecular-weight thiols, especially glutathione. We analyzed this process, termed S-thiolation, in cultured gastric mucosal cells from guinea pigs by gel electrophoresis and autoradiography after radiolabeling of the intracellular glutathione pool with 35S. Hydrogen peroxide (H2O2) or diamide initiated rapid and reversible S-thiolation of specific proteins with molecular masses of 42, 30, 29, 28, and 22 kDa. Diamide caused particularly prominent S-thiolation of the 42 kDa protein. This protein was identified as actin by immunoblot analysis and actin-myosin precipitation. Fluorescence microscopy revealed that diamide caused a disappearance of normal stress fibers and a concomitant increase in actin polymerization in association with contraction of the cells. These morphological changes were completely reversible within minutes. With cells depleted of glutathione by incubation with DL-buthionine-[S,R]-sulfoximine, diamide caused severe contraction and rounding, and the cells detached from the culture plates. S-thiolation of actin could help protect gastric mucosal cells against irreversible organization of microfilaments by preserving microfilament dynamics under oxidative stress.
Oxygen free radical formation by rat hepatocytes during postanoxic reoxygenation: scavenging effect of albumin
Authors: Caraceni P. , Gasbarrini A. , Van Thiel D. H. , Borle A. B.
Published: December 2017

Free radical formation and reoxygenation injury were studied in rat hepatocytes perfused with Krebs-Henseleit bicarbonate buffer containing 1% or no albumin. After 2, 2.5, or 3 h of anoxia followed by 1 h reoxygenation in the absence of albumin, free radical formation assessed by low-level chemiluminescence and cell injury measured by lactate dehydrogenase (LDH) release and by trypan blue uptake increased proportionately. Chemiluminescence increased 4- to 7-fold, LDH release and trypan blue uptake increased 1.5- to 2-fold, compared with the end of anoxia. With 1% albumin, there was no increase in free radical formation during reoxygenation, and LDH release returned to control levels. There was a linear relation between the increase in chemiluminescence and the rise in LDH release (r2 = 0.83) and the increase in trypan blue uptake (r2 = 0.80), suggesting that free radical formation during reoxygenation is responsible for the cell injury. These experiments demonstrate that freshly isolated hepatocytes produce oxygen free radicals detectable by low-level chemiluminescence and that reoxygenation injury occurs after a relatively short period of anoxia (2-3 h). Albumin acts as a free radical scavenger, suppresses the release of reactive oxygen species, and significantly reduces reoxygenation injury.