bluuebunny/crossref_metadata_2025 huggingface dataset:
Prostacyclin inhibits pancreatic secretion
Authors: Konturek S. J. , Tasler J. , Jaworek J. , Cieszkowski M. , Pawlik W.
Published: December 2017

Prostacyclin (PGI2), the major product of arachidonate metabolism in the gastrointestinal tract, was shown to affect gastric blood flow and gastric secretion, but it is unknown whether it also affects pancreatic secretion. This study was designed to determine the influence of PGI2 on pancreatic secretion under basal conditions and in response to exogenous and endogenous stimulants. PGI2 alone given in graded intravenous doses caused a slight pancreatic bicarbonate and protein secretion in fasted dogs. When given during stimulated pancreatic secretion, PGI2 caused a potent inhibition of the bicarbonate and protein secretion induced by feeding a liver meal, by duodenal perfusion with hydrochloric acid or amino acid mixture, and by intravenous infusion of secretin or caerulein. The kinetic analysis showed that the interaction between PGI2 and secretin affecting bicarbonate secretion is of a mixed type (increased half-maximal dose response, decreased calculated maximal response). This indicates that PGI2 decreases both the total secretory capacity of the pancreas to secrete bicarbonate and reduces the sensitivity of the pancreatic secretory cells to secretin. Because PGI2 significantly reduced the arterial blood pressure, its inhibitory effects on pancreatic secretion could be due, at least in part, to the interference of the blood flow to the pancreas.
Effects of Ca2+ on ileal transport and electrically induced secretion
Authors: Hubel K. A. , Callanan D.
Published: December 2017

[Ca2+] affects nerves and target cells in stimulus-secretion coupling. In flux-chamber studies of full-thickness rabbit ileum, we determined the effects of 1) ethylene glycol bis-(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) 1.25 mM, 2) verapamil 0.1 mM and nifedipine 0.1 mM, and 3) trifluoperazine 0.1 mM on ion transport and its response to electrical field stimulation (EFS). EGTA increased JClm leads to s, JNam leads to s, Cl absorption and conductivity (G), and reduced Isc. In the absence of EGTA, EFS increased transmural PD and Isc and caused secretion of Na and Cl. EGTA prevented the responses to EFS, but the Isc responses to aminophylline and to glucose were normal. Verapamil reduced the response of Isc and Cl transport to EFS. Nifedipine reduced Isc but not the Isc response to EFS. Trifluoperazine reduced Isc and almost eliminated the Isc response to EFS. EFS did not increase the tissue concentration of cAMP. We conclude: 1) low extracellular [Ca2+] enhances net Cl absorption; 2) extracellular Ca2+ is required for the response of ion transport to EFS; 3) cAMP does not mediate Isc response to EFS; and 4) Isc response to EFS is blocked by trifluoperazine. The findings suggest that EFS stimulates secretion by increasing Ca entry into the epithelial cells, either directly or indirectly.
Gastric bicarbonate secretion: effect of topical and intravenous 16,16-dimethyl prostaglandin E2
Authors: Kauffman G. L. , Reeve J. J. , Grossman M. I.
Published: December 2017

These studies were designed to compare intravenous and topical 16,16-dimethyl prostaglandin E2 (dmPGE2) as stimulants of gastric mucosal HCO3- secretion. In six Heidenhain pouch (HP) dogs, basal acid secretion was inhibited by cimetidine. With 100 ml 0.15 M NaCl as the fluid circulating through the HP, intrapouch titration to pH 6.0 was performed with 0.5 M HCl as titrant. After measuring basal HCO-3 secretion for 30 min, dmPGE2 was given intravenously or the fluid circulating in the HP was replaced by one containing dmPGE2. Intravenous dmPGE2 at infusion rates of 0, 0.5, 1.0, and 2.0 microgram . kg-1 . h-1 produced alkaline secretion rates of 34 +/- 9, 52 +/- 20, 72 +/- 21, and 70 +/- 20 (SE) mu mol . h-1, respectively. Topical dmPGE2 at concentrations of 0, 0.05, 1.25, and 2.50 microgram . ml-1 produced alkaline secretion rates of 22 +/- 7, 74 +/- 16, 134 +/- 28, and 144 +/- 35 mu mol . h-1, respectively (P less than 0,05 for each concentration). Glucosamine output, as an index of mucus secretion, increased significantly with HCO-3 secretion. We conclude that intragastric titration is a valid method for recording HCO-3 secretion from an HP, that topical dmPGE2 stimulates HCO3- secretion more effectively than intravenous dmPGE2, and that topical dmPGE2 stimulates mucus secretion as well as HCO-3 secretion,
Inductive displacement gauge
Authors: Kingma Y. J. , Bowes K. L. , Kocylowski M. S. , Szmidt J.
Published: December 2017

Strain gauges are often used for the measurement of contractile activity of muscle tissue. In these cases the strain gauge is used as a force measuring device. Because of its stiffness, the strain-gauge-type transducer resists changes in length produced by contraction, and this could cause secondary effects. This paper describes an alternative method to evaluate contractions. Displacement rather than force is measured. The device offers very little resistance to motion and thus does not constrain the tissue. The sensitivity of the transducer is very high. An additional feature is the low cost of the transducer compared to strain-gauge devices.
Peptide secretory pathways in GI tract: cytochemical contributions to regulatory physiology of the gut
Authors: Larsson L. I.
Published: December 2017

Numerous biologically active peptides are produced by specialized cells of the gastrointestinal tract. Most of these peptides are also produced outside the gut, and current evidence suggests that they not only regulate digestive events per se but also participate in many other regulatory mechanisms working as hormonal, paracrine, and neuronal messengers. The physiological functions of the gastrointestinal peptides are yet very incompletely known. Immunocytochemical tracing of the destinations of neuronal and paracrine cell processes may, together with available physiological and biochemical data, provide valuable clues to the sites of actions of many of the novel regulatory peptides. Moreover, immunocytochemistry has given evidence for the occurrence of multiple secretory peptides in certain endocrine cell types and suggested that certain peptides simultaneously may be secreted by multiple endocrine, paracrine, and neural cell types. This review emphasizes the continued need for concerted cytochemical, physiological, and biochemical studies of the sites of synthesis, secretion, and action of gastrointestinal regulatory peptides.
Histamine and cAMP as possible mediators of acetylcholine-induced acid secretion
Authors: Ekblad E. B.
Published: December 2017

Data are presented in support of the role of histamine and adenosine 3',5'-cyclic monophosphate (cAMP) as mediators of acetylcholine-induced acid secretion in frog gastric mucosa. These data also support the notion that acetylcholine-induced alkaline secretion is mediated by guanosine 3',5'-cyclic monophosphate (cGMP). Tissue cAMP and cGMP and rates of acid secretion and histamine release were measured in in vitro preparations of frog gastric mucosa that had been stimulated by acetylcholine. A transient increase in each variable was observed, the sequence of transient maxima being histamine release, cGMP, cAMP, and acid secretion. Atropine, an anticholnergic agent, eliminated all four transient increases, the variables remaining at resting levels. Metiamide, a H2-antagonist, modified the changes observed after acetylcholine stimulation. The acid secretion transience was abolished and the transient increase in tissue cAMP was greatly diminished, whereas the tissue of cGMP transience and histamine release transience remained unchanged. A model is proposed in which acetylcholine initiates two different processes, acid and alkaline secretions.
Subcellular distribution of PRibPP synthetase activity of rat intestinal mucosa
Authors: Yip L. C. , Yeh A. K. , Balis M. E.
Published: December 2017

5-Phosphoribosyl 1-pyrophosphate synthetase (PRibPP synthetase EC 2.7.6.1) isolated from rat intestinal mucosa was found to be membrane associated. The subcellular distribution of PRibPP synthetase activity seems to parallel that of gamma-glutamyl transpeptidase, indicating it to be in the brush border. The tip cells of rat intestinal mucosa were richer in PRibPP synthetase than the crypt cells. Chromatography of a Triton-solubilized particulate fraction unmasked a peak of hypoxanthine phosphoribosyltransferase activity that was not detectable before. The activity, too, was concentrated in the brush border. The coexistence of these two activities in the fraction of the bowl involved in absorption has led to the suggestin that the synthetase and phosphoribosyl-transferase are part of a coupled transport system.
Primary cultures of feline acinar cells: dissociation, culturing, and viral infection
Authors: Fritz M. E. , LaVeau P. , Nahmias A. J. , Weigel R. J. , Lee F.
Published: December 2017

A technique for dissociating and plating of feline parotid acinar cells by enzymatic dispersion with collagenase and trypsin is presented. Viability of the cultured cells was determined by: 1) estimating cellular growth with visual cell counts and by [3H]thymidine incorporation; 2) observing the lack of uptake of vital dyes by the cultured cells: 3) making light, phase contrast, and electron microscopic morphological examinations; and 4) determining the lack of amylase secretion without stimulation, and the evidence of amylase secretion in response to isoproterenol. The cultured feline parotid acinar cells were infected with feline rhinotracheitis virus, a member of the herpes group. Evidence for viral infection was morphological and by indirect fluorescent antibody studies. The viral infected cells also showed no amylase release without stimulation and demonstrated an initial response to a beta-adrenergic agonist by secretion of amylase, but repeated stimulation of the virally infected cells did not produce amylase secretion.
Permeability characteristics of colonic capillaries
Authors: Richardson P. D. , Granger D. N. , Mailman D. , Kvietys P. R.
Published: December 2017

Blood flow, lymph flow, lymph protein concentration (CL), lymph oncotic pressure, plasma protein concentration (CP), and plasma oncotic pressure were determined under steady-state conditions at venous pressures of 0, 10, 20, 30, and 40 mmHg in autoperfused segments of dog colon. Venous pressure elevation increased colonic vascular resistance, lymph flow, lymphatic protein flux, and the transcapillary oncotic pressure gradient, whereas the lymph-to-plasma protein concentration ratio (CL/CP) declined. The osmotic reflection coefficient (sigma d) was estimated using sigma d = 1-CL/CP when CL/CP is filtration independent (high lymph flows). For total protein sigma d = 0.85 +/- 0.02. Values of sigma d for plasma protein fractions with molecular radii ranging between 37 and 120 A increased as molecular radius increased. The results of this study suggest that 1) colonic capillaries selectively restrict macromolecules on the basis of molecular size, and 2) an increased lymph flow and transcapillary oncotic pressure gradient may play an important role in preventing interstitial edema subsequent to venous pressure elevation in the dog colon.
Longitudinal and circumferential spread of spike bursts in canine jejunum in vivo
Authors: Dusdieker N. S. , Summers R. W.
Published: December 2017

This study demonstrates a new method for quantitatively analyzing individual intestinal spike bursts and establishes the distribution of spike burst spread under conditions of fasting and feeding in conscious healthy dogs. The dimensions and propagation lengths of individual jejunal spike bursts were determined by studying spike burst spread within slow-wave cycles. Electromyograms were recorded simultaneously from multiple closely spaced serosal electrodes in the jejunum (4 equally distant around the circumference and 16 along the long axis at 3-cm intervals). At least 75% of the time, spike bursts involved the entire cross-sectional circumference simultaneously. Greater than 50% of spike bursts during fasting or feeding spread distally 3-30 cm. The remainder were isolated or segmental spike bursts involving < 3 cm of jejunum. The lengths of propagative spike bursts increased with the time during phase II and reached a maximum of 30-40 cm during phase III. Fed activity showed a mixture of segmental and longer propagative spike bursts that varied little with time after feeding. Propagative spike bursts > 3 cm in length produced at least 85% of the total myoelectric burst activity regardless of the state of fasting or feeding and constitute the major form of intestinal motility in the canine jejunum.
Messenger role of calcium in function of pancreatic acinar cells
Authors: Schulz I.
Published: December 2017

Enzyme secretion from the exocrine pancreas is elicited by a) cholinergic stimulants, b) hormones belonging to the family of pancreozymin, c) some amphibian peptides such as bombesin, eledoisin, and physalaemin, and d) secretin and vasoactive intestinal polypeptide. Whereas the mechanism of the group d hormones in stimulating enzyme secretion involves adenosine 3',5'-cyclic monophosphate, the others seem to use a common pathway involving Ca2+ as intracellular messenger and probably guanosine 3',5'-cyclic monophosphate as modulator of their action. Their effects can be ascribed to two processes. One pathway involves release of Ca2+ from an intracellular store that is most likely located in the plasma membrane. This phase is independent of extracellular Ca2+ and leads to a rise of guanosine 3',5'-cyclic monophosphate. The other pathway is characterized by an increased permeability of the plasma membrane for Ca2+ and is necessary for sustained secretion. Both pathways lead to an increase cytosolic-free Ca2+ concentration. Ca2+ is either directly involved in fusion of zymogen granules with the luminal cell membrane or triggers events that lead to exocytosis. Furthermore, augmented cytosolic-free calcium concentration a) increased the plasma membrane permeability for Na+, Cl-, and K+, which leads to depolarization of the cell, and b) induces uncoupling of neighboring acinar cells.
Mucosal gastrin receptor. IV. Binding specificity
Authors: Takeuchi K. , Speir G. R. , Johnson L. R.
Published: December 2017

We used membrane preparations of rat oxyntic gland mucosa to test the binding of various gastrin analogues to the gastrin receptor. Using [125I]15-Leu G-17 as a marker, a concentration of 4 X 10(-9) M unlabeled G-17 inhibited binding 50%. The tetra-, penta-, and hexapeptides of gastrin caused similar 50% inhibitions of binding at concentrations of 1 X 10(-7) M, 3 X 10(-8) M, and 7 X 10(-9) M, respectively. The heptapeptide caused only slightly less inhibition than G-17, whereas the decapeptide was equivalent in potency. Neither the G-17 nor G-34 that had the active tetrapeptide removed caused 50% inhibition of binding. When compared to G-17, these analogues produced only a 25% inhibition of binding at concentrations of 10(-8) M. We also failed to inhibit binding more than 25% when we used an analogue that had the amide removed from the C-terminal phenylalanine. Atropine, metiamide, and mepyramine did not alter the binding of gastrin to receptor. The results of binding specificity approximate the changes in biological potency associated with these compounds. This study adds further support that the gastrin receptor in question is responsible for the physiological effects of the hormone.
Influence of vagus nerves on electrical activity of opossum small intestine
Authors: Gidda J. S. , Goyal R. K.
Published: December 2017

Experiments were performed in anesthetized opossums to study the nature of vagal control on the small bowel. Electrical activity was recorded in the duodenum, jejunum, and ileum with silver chloride electrodes. Slow waves and spike potentials were observed at all three sites. There was a decreasing frequency gradient of slow waves and the incidence of slow waves with spikes in the aboral direction. Vagotomy had no effect on the electrical activity. Vagal stimulation at threshold stimuli inhibited spike potentials in all three segments of small intestine, but slow waves were not affected. Vagal stimulation after sectioning of the gut proximal to the electrodes converted the response from inhibition to excitation. These studies suggest that a) vagus carries both excitatory and inhibitory influences to the small bowel; b) inhibitory influences are dominant in the intact opossum small intestine; and c) the nature of the response obtained with vagal stimulation may be explained on the basis of the paths taken by inhibitory and excitatory fibers.
Aspirin- and taurocholate-induced metabolic damage in mammalian gastric mucosa in vitro
Authors: Ohe K. , Hayashi K. , Shirakawa T. , Yamada K. , Kawasaki T. , Miyoshi A.
Published: December 2017

To clarify the mechanism of initiation of the hydrogen ion backdiffusion, the effects of aspirin and taurocholate, two representative gastric mucosal barrier breakers, on the potential difference, secretory activity, energy metabolism, and the hydrogen ion permeability of guinea pig gastric mucosa was studied in vitro. 1) The ATP content and energy charge of the gastric mucosa showed a statistically significant reduction when the potential difference decreased to one-half of that before addition. 2) The mucosal acid secretion was reduced by addition of the barrier breaker. 3) However, the hydrogen ion backdiffusion, as measured by titrating the acid appearing in the serosal solution, became detectable when the potential difference decreased to one-fourth of that before addition. It has been concluded, therefore, that the primary action of gastric mucosal barrier breakers is to damage the energy metabolism of the mucosal cells, and that the hydrogen ion backdiffusion takes place as the result of cellular death caused by the impairment of energy metabolism.
Effect of luminal distension on intestinal transcapillary fluid exchange
Authors: Granger D. N. , Kvietys P. R. , Mortillaro N. A. , Taylor A. E.
Published: December 2017

The direct effects of luminal distension pressure on intestinal transcapillary fluid exchange were studied in isolated autoperfused cat ileum preparations. Intestinal lymph flow, lymphatic pressure, lymph-to-plasma protein concentration ratio (L/P), blood flow, and perfusion pressures were allowed to reach a steady state at different luminal distension pressures (0–40 mmHg). Luminal distension was induced using a nonabsorbable silicone solution, thereby eliminating an influence of net water absorption. At a venous outflow pressure of 0 mmHg, lymph flow and lymphatic pressure increased, whereas blood flow and L/P decreased as luminal pressure was increased. The relationship between lymph flow, blood flow, and venous pressure was acquired at luminal pressures of 0 and 20 mmHg. When luminal pressure was 0, lymph flow increased and blood flow decreased progressively with venous pressure elevation; however, when luminal pressure was 20 mmHg, lymph flow and blood flow were unaffected until pressure exceeded 20 mmHg. The results of this study indicate that luminal pressure elevation enhances transcapillary fluid exchange and imposes a “waterfall” effect on the intestinal vasculature.
Effect of sodium taurocholate on secretion by amphibian gastric mucosa in vitro
Authors: Rees W. D. , Garner A. , Vivian K. H. , Turnberg L. A.
Published: December 2017

Effects of sodium taurocholate on the electrical and secretory activity of amphibian gastric mucosa have been studied in vitro. Exposure of the luminal surface of fundic mucosa to high concentrations (5 X 10(-2) M) at low pH (2.0 and 3.0) produced a marked fall in potential difference and electrical resistance. At lower concentrations (10(-3) to 10(-4) M) and higher pH (7.4), taurocholate did not alter the electrical properties but significantly increased net acidification from 1.39 +/- 0.27 to 2.01 +/- 0.18 mueq . cm-2 . h-1 (means +/- SE; P less than 0.01). Pretreatment of fundic mucosa with cimetidine resulted in net alkaline secretion (0.27 +/- 0.07 mueq . cm-2 . h-1), and addition of taurocholate (10(-4) M) to the luminal surface at pH 7.4 converted net alkalinization to net acidification (0.94 +/- 0.28 mueq . cm-2 . h-1). This response was not inhibited by atropine (10(-5) M) or somatostatin (10(-6) M) but exhibited marked tachyphylaxis. Taurocholate (10(-4) M) inhibited alkaline secretion in thiocyanate-treated fundic mucosa (0.63 +/- 0.04 to 0.14 +/- 0.09 mueq . cm-2 . h-1; P less than 0.001) and in spontaneously alkaline-secreting antral mucosa (0.36 +/- 0.12 to 0.09 +/- 0.06 mueq . cm-2 . h-1; P less than 0.05), but acidification did not occur. Apparent stimulation of acid secretion and simultaneous inhibition of alkaline secretion of sodium taurocholate may play a role in the pathogenesis of mucosal damage by bile.
K+ selectivity and HCl secretion in Xenopus and their relation to cAMP and Ba2+
Authors: Takeguchi N. , Nishimura Y. , Morii M. , Horikoshi I. , Inoue S.
Published: December 2017

Doses of 1, 5, and 10 mM adenosine 3',5'-cyclic monophosphate (cAMP) applied to previously resting Xenopus gastric mucosae initiated a dose-dependent acid secretory response. Increases in the K+ concentration of the submucosal solution. [K+sm], resulted in higher acid secretory rates and concomitant lower transmucosal resistances at the indicated cAMP concentration. The transmucosal potential difference, PD, had a liner slope against log [K+sm] over the range of 20-80 mM K+sm. Values of the slope (K+ selectivity, -PD/log[K+sm]) were less than 26 mV/log for resting mucosae, and in the range of 29-58 mV/log for both spontaneously secreting and cAMP-stimulated mucosae. These values were dose dependent on the cAmP concentration. In the presence of 10 mM Ba2+ together with cAMP, the K+ selectivity and the H+ secretory rate decreased compared with the case of cAMP only.
Effect of metabolic acidosis on intestinal absorption of calcium and phosphorus
Authors: Gafter U. , Kraut J. A. , Lee D. B. N. , Silis V. , Walling M. W. , Kurokawa K. , Haussler M. R. , Coburn J. W.
Published: December 2017

Page G480: U. Gafter, J. A. Kraut, D. B. N. Lee, V. Silis, M. W. Walling, K. Kurokawa, M. R. Haussler, and J. W. Coburn. “Effect of metabolic acidosis on intestinal absorption of calcium and phosphorus.” Page G480: M. W. Walling deceased 30 November 1979.
Relation between small intestinal motility and circulation
Authors: Walus K. M. , Jacobson E. D.
Published: December 2017

Effects of muscular activity on local blood flow have been delineated in other muscular organs but are part of a complex relationship in the small intestine. Some of our inability to provide a clear picture of the circulatory events surrounding intestinal motility relates to the variety of imprecise techniques that have been used to explore the relationship. Distension of the gut impedes blood flow through the intestinal wall, especially in the mucosa. Stimulation of motility evokes more variable responses in the intestinal circulation, including increases in blood flow; however, the circulatory response reflects mostly the nature of the intervention used to activate motility. Many motor stimuli in the gut have intrinsic vasoactive properties. Spontaneous motor events seem to have only small effects on total blood flow to the small intestine. Reduction in blood flow to the gut evokes initial increases in motility followed by inhibition of motor activity. Products of metabolism in the intestine influence both motor and vascular reactivity. More sensitive methods need to be developed to separate the types of intestinal motor activity, to localize mechanical events in specific sites in the wall of the gut, to better record electrical correlates of motility, and to measure local tissue blood flow. These technical developments will permit delineation of the linkage between motor and vascular events and should identify the regulatory factors.
Variation in canine exocrine pancreatic secretory activity during the interdigestive state
Authors: Itoh Z. , Takahashi I. , Nakaya M. , Suzuki T.
Published: December 2017

Interdigestive changes in pancreatic volume flow, gastric motor activity, and intraduodenal pH were monitored automatically in eight dogs. As a result, two different periods of pancreatic secretion were found to occur alternately during the interdigestive state: one a secretory period (2.2 +/- 0.32 ml/10 min with high protein and low bicarbonate concentration) and the other a nonsecretory period. The secretory period corresponded to the interdigestive phase II and III contraction period in the stomach, and the nonsecretory period coincided with the motor quiescent period in the stomach. However, another secretory period was identified during the interdigestive state; it occurred when the intraduodenal pH went below 7.0, and no typical interdigestive contractions were observed in the stomach. The secretory rate was 3.7 +/- 0.33 ml/10 min and was low in protein and high in bicarbonate concentration. The present study demonstrates that basal pancreatic secretory activity is never uniform but fluctuates with motor events in the stomach. However, its control mechanism remains unknown at present.
Reversal of cholera toxin-induced secretion in rat ileum by luminal berberine
Authors: Swabb E. A. , Tai Y. H. , Jordan L.
Published: December 2017

The effect of luminal berberine hydrochloride concentration on cholera toxin-induced water and electrolyte secretion and on normal water and electrolyte transport was determined in vivo in the cannulated, perfused rat ileum using [14C]polyethylene glycol as a nonabsorbable marker. Berberine reduced the cholera toxin-induced secretion of water, Na, Cl, and calculated residual ion (primarily HCO3) in a concentration-dependent manner. The effect of berberine on cholera toxin-induced ileal secretion was evident 60-80 min after exposure and was reversed 60–80 min after removal of berberine from the perfusate. Mild changes in mucosal histology (villous tip edema) due to cholera toxin were also reversed by berberine. Berberine did not significantly alter normal ileal water and electrolyte transport.
Inhibition of human pancreatic lipase-colipase activity by mixed bile salt-phospholipid micelles
Authors: Patton J. S. , Carey M. C.
Published: December 2017

Mixed dihydroxy bile salt-phosphatidylcholine (PC) micelles can inhibit the hydrolysis of gum arabic-stabilized long-chain triglyceride emulsions by 10(-8) to 10(-9) M concentrations of human pancreatic lipase and colipase. Trypsin treatment of this colipase preparation did not reverse the inhibition, suggesting that procolipase, as a possible contaminant, was not the inhibitory factor. Human biliary phospholipid-cholesterol liposomes, isolated by gel filtration and redissolved in bile salt solutions, inhibited lipolysis to the same degree as solutions of bile salt containing purified PC. The degree of inhibition depended principally on the species of bile salt present (e.g., taurochenodeoxycholate greater than taurodeoxycholate greater than tauroursodeoxycholate greater than taurocholate). In the absence of bile salt, PC (0.4 mM) liposomes alone were not inhibitory over the physiological time range studied. Bile salt solutions of phosphatidylethanolamine or sphingomyelin also inhibited lipase activity, whereas those containing oleyl alcohol, oleyl aldehyde, oleic acid, and lyso-PC did not. PC molecules were found to partition between the triglyceride emulsion interface and the bulk aqueous phase. Full reversal of inhibition occurred in the presence of phospholipase A2, which hydrolyzed the phospholipids to lysolecithin and fatty acids. Mixed bile salt-phospholipid micelles caused marked decrease in the binding of lipase and colipase to the triglyceride substrate and displaced the proteins into the aqueous phase. The results taken together suggest that colipase binds to certain bile salt-PC associations independent of whether the aggregates are located at the surface of a triglyceride particle as a monolayer or in the bulk aqueous phase as mixed micelles.
Gut immunophysiology: a gastroenterologist's view with emphasis on pathophysiology
Authors: Dobbins W. O.
Published: December 2017

This review is a brief survey of our knowledge of the immune functions of the gastrointestinal tract. The mucosal immunologic system is present at all epithelial surfaces that are in direct contact with the external environment, is largely independent of the systemic immune response, and is governed by antigenic stimuli at epithelial surfaces. The plasma cell population responsive to these antigens is found just below the epithelium, and the antibodies produced are transported to the epithelial surface by a unique process. Finally, the antibodies secreted are able to function even in the presence of proteolytic enzymes. Brief reviews of immunophysiology and immunomorphology of the gastrointestinal immune system are enclosed. The immune response of the gut is discussed in relation to immune regulation by helper and suppressor systems. Even though secretory immunity may be considered "old hat," several new aspects of this system are emphasized along with an overview of the system. The clinical manifestations and pathophysiology of the two major adult immunodeficiency syndromes are reviewed in order to emphasize normal immunophysiology. There is a brief discussion of food allergy. Future directions that may be appropriate for research in both systemic and mucosal immunology are discussed in the final section.
Effect of fasting and refeeding on pancreatic enzymes and secretagogue responsiveness in rats
Authors: Lee P. C. , Brooks S. , Lebenthal E.
Published: December 2017

Fasting reduced amylase and increased lipase concentrations but did not affect trypsinogen concentrations in the adult rat pancreas. Fasting also decreased the pancreatic contents of trypsinogen and amylase. A decrease in the responsiveness of dispersed pancreatic acini to carbachol was evident after 3 days of fasting but only at high concentrations of secretagogues. Acini regained their responsiveness, and enzyme concentrations returned to normal after refeeding. Serum insulin levels of fasted rats decreased to one-fourth of control levels but rose to normal 24 h after refeeding. Insulin or glucose given alone prevented the increase in lipase after fasting. Both insulin and glucose were needed to maintain the acinar response to secretagogues in fasted rats. Although cholecystokinin restored the protein and trypsinogen content in fasted rats, it did not correct the relative changes in the exocrine enzymes. There are therefore reversible changes in the exocrine pancreas after fasting. Insulin, glucose, and cholecystokinin seem to regulate these changes.
Effect of tryptophan on transport properties of newborn rabbit jejunum
Authors: Cooke H. J. , Cooke A. R.
Published: December 2017

The effect of tryptophan on sodium and chloride fluxes was determined simultaneously on paired flat-sheet preparations of newborn rabbit jejunum under short-circuit conditions. In the absence of amino acids, the newborn rabbit jejunum actively absorbed sodium, and possibly bicarbonate, whereas chloride appeared to be distributed passively across the jejunum. Tryptophan (2 mM) caused an increment in short-circuit current (Isc) that was due to an increase in net active sodium flux and had no significant effect on tissue conductance. At a 10 mM concentration, tryptophan initially increased Isc, although not to as large a degree as phenylalanine or alanine, and then caused a progressive decline that reached a plateau around 60 min. The reduction in Isc was attributed primarily to abolition of sodium absorption and stimulation of chloride secretion. Tryptophan reduced the unidirectional fluxes of sodium, increased those of chloride, and decreased total tissue conductance. These results suggest that 10 mM tryptophan initially causes a predicted increase in sodium absorption, followed by an inhibition of sodium absorption and stimulation of chloride secretion. The mechanism of action of tryptophan resulting in changes in ion fluxes is unknown.
Ionic requirements for H+ secretion and membrane elaboration in frog oxyntic cells
Authors: Logsdon C. D. , Machen T. E.
Published: December 2017

We have tested whether the ions K+, Na+, or Cl- are required for either initiation or maintenance of secretory parameters of amphibian oxyntic cells. In vitro mucosal preparations were washed repeatedly in Ringer solution lacking the ion in question either before (i.e., resting tissues) or after addition of stimulants. Electrophysiology, H+ secretion, and morphology (morphometric analysis of oxyntic cells) were monitored. Na+ or K+. Stimulation of resting tissues in Na+ or K+-free solutions elicited no H+ secretion; there was only a small increase (approximately twofold) in secretory surface density (Sv) (during control Sv increased sixfold). The Na+-free effects were partially reversed by high [K+]. In secreting tissues, Na+ or K+-free solutions caused H+ secretion to decrease to zero. Gastric glands from these mucosae appeared "occluded": the gland lumen was filled with apposed apical projections of oxyntic cells. Cl-. Stimulation after Cl- removal initiated low levels of H+ secretion. Morphologically the cells either appeared normally stimulated (Sv increased eightfold) or, more rarely, took on the occluded appearance. Cl- removal from stimulated mucosae decreased H+ secretion approximately 50%, but the cells were normally elaborate. We conclude that K+ is required for the initiation of H+ secretion and the stimulated morphology change; the effects of Na+ removal are due to effects on internal [K+]; Cl- is not required. The occurrence of occluded morphology under conditions of inhibited H+ and H2O secretion indicates a role for water flow in the maintenance of stimulated morphology.
[14C]erythritol clearance and canalicular bile acid-independent flow in the baboon
Authors: Strasberg S. M. , Ilson R. G. , Petrunka C. N.
Published: December 2017

The use of [14C]erythritol for the quantitative assessment of hepatic bile formation has been studied in baboons using sodium taurocholate to generate canalicular bile flow. It has been found that increments in [14C]erythritol clearance are equal to taurocholate-induced increments in bile flow, but there was no change in [14C]erythritol clearance when bile flow was increased by secretin. No evidence was found to support the view that bile acids affect bile acid-independent bile flow.
Stimulation of ammonia production from glutamine by intraluminal glucose in small intestine of dogs
Authors: Weber F. L. , Veach G. , Friedman D. W.
Published: December 2017

Previous studies have shown that the quantity of ammonia derived from the small intestinal metabolism of arterial glutamine was equal to ammonia released by the colon. Little is known, however, about processes that may alter small intestinal glutamine metabolism. The purpose of this study was to evaluate the effect of intraluminal, nonnitrogenous compounds on ammonia release into mesenteric venous blood and glutamine uptake from arterial blood by in situ intestinal segments in anesthetized, fasted dogs. In paired luminal perfusion studies, either 50 mM glucose, 3-O-methylglucose, or 3-hydroxybutyric acid was compared with a control perfusate containing 50 mM mannitol. In the jejunum, glucose perfusion significantly increased ammonia release into mesenteric venous blood by 21 +/- 5 nmol.min-1.g intestine-1 or 32 +/- 7% and glutamine uptake from arterial blood by 21 +/- 3 nmol.min-1.g intestine-1. Perfusion of ileum with glucose also significantly increased ammonia release by 8 +/- 1 nmol.min-1.g intestine-1 or 12 +/- 2% and glutamine uptake by 11 +/- 4 nmol.min-1.g intestine-1, although the increments were less than in the jejunum. Perfusion of the jejunum with 3-hydroxybutyric acid or nonmetabolizable 3-O-methylglucose caused no increase in ammonia release, even though glucose, 3-hydroxybutyric acid, and 3-O-methylglucose were absorbed at similar rates and there were similar increments in water absorption. The results indicated that glucose absorbed from the lumen of both the jejunum and ileum stimulated glutamine uptake from arterial blood and ammonia release into mesenteric venous blood. These effects were quantitatively greater in the jejunum. Stimulation of intestinal glutamine metabolism was probably related to cellular metabolism of glucose and could not be attributed to a stimulation of solute or water absorption.
Evidence for electrogenic Na-Cl symport in the in vitro frog stomach
Authors: Carrasquer G. , Chu T. C. , Rehm W. S. , Schwartz M.
Published: December 2017

The transmucosal potential difference (PD) response to step changes in Na+ (choline or Mg2+ for Na+) in the nutrient fluid was studied. Decreasing the Na+ concentration in the nutrient fluid decreased the positivity of the nutrient side, and increasing the Na+ concentration increased the positivity. This effect is anomalous because it is opposite to that of a simple Na+ conductive pathway but right for a choline or Mg2+ conductive pathway. The lack of linearity of delta PD versus the log of the choline concentration ruled out a choline conductive pathway. An approximate linear relation was obtained for Na+. The anomalous PD response for Na+ was reduced but not abolished in 1) K+-free bathing fluids and 2) 10(-3) M ouabain in nutrient fluid. Changing the Cl- concentration in nutrient fluid gave normal PD responses, which were reduced in the absence of Na+. These results are attributed to a passive electrogenic Na-Cl symport. Theoretical considerations, for p Na+ and q Cl- transported per cycle (with q greater than p), predict an anomalous delta PD for Na+ concentration changes and a normal delta PD for Cl- concentration changes.
Validity of iodoantipyrine clearance for measuring gastrointestinal tissue blood flow
Authors: Dugas M. C. , Wechsler R. L.
Published: December 2017

Simultaneous determinations of 1) the clearance (mF) of 4-iodoantipyrine (IAP) and tritiated water, 2) the mF of IAP and total circulating tissue blood volume, 3) the mF of IAP and either 15- or 25-micrometers-diam-microsphere-measured flow, and 4) 15- and 25-micrometers-diam-microsphere-measured flow were made on tissues from dog gastrointestinal tracts. Results show the mF of IAP equals or exceeds that of tritiated water in all tissue layers, and tissue blood volume does not affect the measurement of the IAP mF. Perfusion of the gastrointestinal wall exhibits macroscopic heterogeneity due to differences in perfusion of the three tissue layers, but an effect of microscopic heterogeneity on tissue mF assessment was not apparent. Composite total-wall IAP mF was not significantly different from 25-micrometers-microsphere total-wall flow and was identical to this flow when colonic locations were omitted. Comparisons of 15-micrometers-microsphere flow to IAP mF and to 25-micrometers-microsphere flow both indicated shunting of 15-micrometers-microspheres. Such shunting occurred predominantly through submucosal and muscle layers. It is concluded that IAP clearance accurately measures blood flow in gastrointestinal tissue.
Conjugation is rate limiting in hepatic transport of ursodeoxycholate in the rat
Authors: Zouboulis-Vafiadis I. , Dumont M. , Erlinger S.
Published: December 2017

It has been reported that biliary secretion is the limiting step in the hepatic transport of bile acids by the hepatocyte from plasma to canalicular bile. The aim of the present study was to examine the role of conjugation in the transport process using ursodeoxycholate (UDCA) and tauroursodeoxycholate (TUDCA), two bile acid with low liver toxicity. Rats were given constant intravenous infusions of cholate (C), taurocholate (TC), UDCA, or TUDCA at progressively increasing rates. The biliary maximum secretory rate (SRm), in nmol . min-1 . 100 g body wt-1, for TC (1,835.2 +/- 135.5, mean +/- SE) was not significantly different from that of C (1,749.4 +/- 85.6). In contrast, the SRm for TUDCA (5,909.4 +/- 304.4) was approximately sevenfold that of UDCA (802.1 +/- 134.2), the difference being statistically significant (P less than 0.001). The SRm of UDCA in the presence of a taurine infusion (1,367 +/- 84.4) was higher than that of UDCA infused alone but still much lower than that of TUDCA. Phenobarbital sodium pretreatment did not increase SRm of UDCA alone or in the presence of a taurine infusion. These results suggest that in the rat 1) conjugation is the rate-limiting step in the overall transport of UDCA (and perhaps other bile acids) by the liver, and 2) the conjugation process itself is limiting, rather than the availability of taurine. They support the view that, although not mandatory for secretion into bile, conjugation of bile acids confers a biological advantage, possibly by increasing the solubility of the bile acid.
Comparison of methods for analyzing gastric isotope emptying
Authors: Dugas M. C. , Schade R. R. , Lhotsky D. , Van Thiel D.
Published: December 2017

The gastric emptying of 99mTc-sulfur colloid, ingested in a nutrient liquid test meal, was followed by gamma camera for normals, diabetics, and diabetics receiving intravenous metoclopramide. Gastric emptying patterns of 99mTc by these groups present as normal, slow, and rapid on simple graphic inspection. Half times of indicator emptying were computed from inspection and from least-squares linear regressions of log(base e) residue versus time for the total postpeak curve and for the remainder of the 15-min postpeak curve. In addition, the percent of 99mTc residue leaving at, and the area under, the residue curve until 6, 12, 24, and 60 min postpeak and the indicator mean transit time (MTT) were computed. Standard half-time determinations revealed no significant differences among the three groups, despite obvious visual differences among them. In contrast, the mean transit time of the rapid group was significantly less than that of the slow (P less than 0.01) and normal (P less than 0.05) groups. However, no statistical difference was noted between the slow and the normal emptiers (P greater than 0.1) using the MTT measure. The percent of particles leaving the stomach and the area under the residue curves demonstrated significant differences among the three groups, reflecting the obvious visual perceptions gained from simple curve inspection. Because the percent of indicator particles leaving the stomach region at a given time reflects a single time, it was concluded that the residue area represents the most reliable, objective, and quantifiable parameter for testing of significant differences.
Localization of ouabain-binding sites in frog gastric mucosa
Authors: Helander H. F. , Durbin R. P.
Published: December 2017

Autoradiography at the light microscopic level was used to localize sites of [3H]ouabain binding in isolated stimulated frog gastric mucosa. Silver grains denoting binding were located near basal and lateral surfaces in both oxyntic and surface epithelial cells. Binding to oxyntic cells occurred well before inhibition of acid secretion, consistent with the view that inhibition by this drug is indirect, and subsequent to inactivation of oxyntic cell Na+-K+-ATPase and the resulting depression of cellular K+. The presence of Na+-K+-ATPase in surface cells, as shown by binding of labeled ouabain, suggests a role for that transport enzyme in electrical activity and secretion of alkali by these cells.
Food, duodenal extracts, and enzyme secretion by the pancreas
Authors: Tseng H. C. , Grendell J. H. , Rothman S. S.
Published: December 2017

Previous studies have reported that injection of duodenal extracts from rats fed different meals into the celiac artery of recipient rats elicited the secretion of related pancreatic enzymes. We have been unable to reproduce the enzyme-specific increases in the average output of particular enzymes that were observed but did find changes similar in direction, although not magnitude, to those reported previously. The outputs of amylase and trypsinogen were compared by plotting individual data points and performing a regression analysis on them. The injection of duodenal extracts from lactalbumin hydrolysate-fed rats led to trypsinogen secretion being favored over that of amylase and vice versa for extracts from rats fed a glucose meal. In addition, it was found that cholecystokinin-pancreozymin produced a dramatic nonparallel transport of these two enzymes with amylase secretion being augmented to a greater degree than trypsinogen secretion. The relation between their outputs was curvilinear, i.e., the amylase dominance of secretion became more pronounced as overall enzyme output (not dose of hormone) increased. Thus, this nonparallel secretion does not seem to be the results of a discontinuous switch in the character of enzyme secretion produced by the hormone but a graded effect reflecting the magnitude of the response.
Stimulation of pepsinogen release from isolated gastric glands by cholecystokininlike peptides
Authors: Hersey S. J. , May D. , Schyberg D.
Published: December 2017

Gastric glands isolated from rabbit stomach were employed to study the regulation of pepsinogen secretion by peptide hormones. Cholecystokinin octapeptide (CCK-OP) stimulated pepsinogen secretion with an ED50 of about 1 nM. Caerulein was as effective as CCK-OP but less potent (ED50, 10 nM). Gastrin (HG-17) was found to be a weak stimulus, being only about 20% as effective as CCK-OP or caerulein. Sulfation of CCK-OP and caerulein was found to be important for potency but did not alter efficacy. Peptide stimulation of pepsinogen secretion was unaffected by cimetidine, atropine, or propranolol. Combinations of peptides resulted in less-than-additive responses, as did the combination of peptides with carbachol. In contrast, combination of peptides with isoproterenol resulted in additive responses. Accumulation of the weak base aminopyrine was used to measure acid formation by the gastric glands. The peptides gastrin, CCK-OP, and caerulein were found to be equally effective in stimulating acid formation. The peptide stimulation of pepsinogen secretion was inhibited by dibutyryl cGMP, whereas stimulation of acid formation was not inhibited by the cyclic nucleotide. The results indicate that gastric glands contain at least two peptide receptors distinguishable by sensitivity to dibutyryl cGMP. The peptide receptor associated with pepsinogen secretion appears to be selective for CCK relative to gastrin.
Gastric mucosal barrier: hydrophobic lining to the lumen of the stomach
Authors: Hills B. A. , Butler B. D. , Lichtenberger L. M.
Published: December 2017

The contact angle subtended between a droplet of aqueous fluid and nonwettable surfaces provides a direct estimation of their degree of hydrophobicity. The mean contact angle recorded in dogs at the oxyntic mucosal surface was 85.2 degrees, a value characteristic of acid-resistant substances such as polyethylene. This indicates that the mucosal surface of the stomach has a hydrophobic lining that may be attributed to the surface-active phospholipids known to be present in both the gastric mucosa and juice. Barrier breakers such as bile and aspirin were found virtually to eliminate the hydrophobicity. Hydrophobicity was found to be different in the esophagus, antrum, proximal and distal duodenum, and the colon but consistent with their resistance to acid attack. Endogenous surfactants are discussed for their capability to provide a cohesive and strongly adsorbed protective monolayer--a physical model for the gastric mucosal barrier compatible with the major properties of the gastric lining and many features of ulcerogenesis, including the protection afforded by prostaglandins.