bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of atropine on secretion from intact and transplanted pancreas in dog
Authors: Singer M. V. , Solomon T. E. , Grossman M. I.
Published: December 2017

In dogs with a fistula of the intact pancreas and a transplanted portion of pancreas, we studied the effect of atropine on the pancreatic secretory response to intravenous caerulein and to intestinal perfusion with tryptophan, both given with a secretin background. Atropine (50 micrograms . kg-1 given as an intravenous bolus injection followed by 20 micrograms . kg-1 . h-1 iv infusion) depressed bicarbonate and protein secretion from intact pancreas during stimulation by secretin alone (250 ng . kg-1 . h-1) but did not suppress the increment in bicarbonate secretion in response to caerulein or tryptophan given against the secretin background. In intact pancreas, atropine suppressed protein secretion in response to tryptophan but not in response to caerulein. Atropine had no significant effect on the secretion of bicarbonate and protein from transplanted pancreas in response to secretin, caerulein, or tryptophan. Thus, the only significant effect of atropine on bicarbonate and protein secretion from intact and transplanted pancreas in response to intravenous caerulein or intraduodenal tryptophan, both given against a background of secretin, was inhibition of the protein response to tryptophan in the intact pancreas. These findings are compatible with the hypothesis that pancreatic protein secretion in response to intraduodenal tryptophan is mediated in part by a cholinergic enteropancreatic reflex.
Effects of sulfation patterns on intestinal transport of bile salt sulfate esters
Authors: De Witt E. H. , Lack L.
Published: December 2017

The absorption of 14C-labeled 3 alpha-, the 7 alpha- and the 3 alpha,7 alpha-sulfate esters of taurochenodeoxycholate by guinea pig small intestine was studied using in vivo and in vitro preparations. In vivo ileal perfusions showed that sulfation markedly decreased uptake by the ileal bile salt transport system and that the position and number of the sulfate radicals affected the degree of transport inhibition. The following relationships were found: transport of taurochenodeoxycholate (TCDC) greater than TCDC-3-sulfate greater than TCDC-7 sulfate greater than TCDC-3,7-disulfate with a decrease of approximately 90% between each pair. In vitro, jejunal perfusions demonstrated that sulfation also decreased passive flux. By use of an everted gut sac technique, the ability of ileum to move the sulfated bile salts against a concentration gradient was measured. Under these conditions transport of TCDC-3-sulfate was minimal, and that of the 7-sulfate and 3,7-disulfate was not observed. In view of the reported increased levels of sulfated bile salts after total or partial biliary tract obstruction, our results support the concept of sulfation as an adaptive mechanism for enhancing fecal elimination of bile salts.
Effect of glucagon on bile cAMP secretion
Authors: Kaminski D. L. , Brown W. H. , Deshpande Y. G.
Published: December 2017

The effect of bile flow and adenosine 3',5'-cyclic monophosphate (cAMP) secretion of substances that alter cAMP metabolism in other systems was evaluated. The experiments were performed on awake dogs with chronic biliary and gastric fistulas and on anesthetized rabbits prepared with acute bile fistulas. In all experiments the enterohepatic circulation was maintained by intravenous bile salt administration. In dogs, glucagon increased bile flow and bile cAMP secretion with 4 micrograms . kg-1 . h-1 increasing bile flow from control values of 273 +/- 27 to 413 +/- 6 microliters/min, whereas bile cAMP concentration rose from 3.9 +/- 0.9 to 12.1 +/- 1.1 nmol/ml. Theophylline in dogs increased bile flow while cAMP secretion decreased. Evaluation of the effects of theophylline on glucagon-stimulated bile flow suggest that both agents act by the same mechanism; however, theophylline did not significantly alter glucagon-stimulated increases in bile cAMP. In rabbits, glucagon increased bile cAMP secretion while bile flow was not significantly changed. Hormonal production of increased systemic or hepatic cAMP can increase bile cAMP unassociated with changes in bile flow. Based on the measurement of cAMP in bile the increase in glucagon-stimulated bile flow produced by theophylline is not cAMP mediated.
Effects of diet calcium and 1,25-dihydroxyvitamin D3 on colon calcium active transport
Authors: Favus M. J. , Kathpalia S. C. , Coe F. L. , Mond A. E.
Published: December 2017

Unidirectional fluxes of calcium were studied in the absence of electrochemical gradients across rat descending colon segments in vitro. Dietary calcium restriction and 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]enhanced absorption by increasing the mucosal-to-serosal fluxes, whereas secretory (serosal-to-mucosal) fluxes were unchanged. Low-calcium diet also stimulated calcium uptake by everted gut sac segments of ascending as well as descending colon, whereas transverse colon was unresponsive. These results show that the colon is a target organ for 1,25-(OH)2D3 and demonstrate the participation of colon in the intestinal adaptation to calcium deprivation.
Use of plasma membrane vesicles
Authors: Sachs G. , Jackson R. J. , Rabon E. C.
Published: December 2017

A summary of current methodologies employed to obtain and characterize epithelial plasma membrane vesicles is presented. Particular emphasis is placed on techniques to evaluate such parameters as homogeneity, tightness, orientation, and the percentage of active vesicles in a given vesicular population. Examples of isotopic, osmotic, and various probe techniques useful for quantitation of transport events and associated electrical phenomena are illustrated. Finally, the unique problems intrinsic to purification and reconstitution of transport proteins are briefly discussed.
Carbon monoxide insensitivity of gastric acid secretion
Authors: Kidder G. W.
Published: December 2017

By the use of hyperbaric conditions, it is possible to obtain high CO/O2 while maintaining O2 tension at a level that is not in itself inhibitory of acid secretion in the isolated frog gastric mucosa. Free solution CO/O2 of up to 10:1 only inhibit acid secretion about 20%, less than expected. Considerations of O2 diffusion into a respiring tissue bounded by unstirred layers predict a CO/O2 at the terminal oxidase ranging from 12 to 64 under various conditions and positions in the tissue, with predicted inhibitions between 55 and 86%. The inhibition observed is light reversible, affects potential difference and resistance in a consistent manner but is never very large. In the absence of O2, the CO-cytochrome alpha 3 complex can be demonstrated spectrophotometrically. Among other possible explanations for these observations, it is suggested that this tissue may contain an inhibitor-insensitive oxidase for a portion of the cytochrome system directly involved in acid secretion.
Circadian rhythmicity in several small intestinal functions is independent of use of the intestine
Authors: Stevenson N. R. , Sitren H. S. , Furuya S.
Published: December 2017

Fifty milliliters of a liquid diet were administered daily to rats in three different ways: 1) orally, beginning at 0000 h; 2) by continuous intravenous infusion; and 3) by discontinuous intravenous infusion from 0000 to 1400 h. Animals were killed every 6 h over a 24-h period. Activity profiles as a function of time of day were determined for the following small intestinal parameters; monosaccharide transport; five disaccharidases; alkaline phosphatase; gamma-glutamyltransferase; leucylnaphthylamide hydrolyzing activity; villus height and width; and number of columnar cells lining a villus section. Circadian rhythmicity as previously reported was observed for all parameters in rats fed orally for 7 days but was not observed in any parameters in rats fed by continuous infusion for 9 days. Rats fed by discontinuous infusion for 10 days maintained circadian rhythmicity in the following functions: monosaccharide transport; disaccharidase activities; and columnar cell number. Thus, rhythmicity in these functions can exist without nutrient delivery to the alimentary tract and presumably arises from involvement of a neuro-endocrine component. The other activities tested appear to require the alimentary tract for the existence of circadian rhythmicity.
Role of fatty acid oxidation in mechanism of action of gastric secretagogues
Authors: Chacin J. , Martinez G. , Severin E.
Published: December 2017

The role of beta-oxidation in the mechanism of stimulation of acid secretion was examined in toad gastric mucosa in vitro. The incubation with 4-pentenoate selectively inhibited in a dose-dependent manner the rate of 14CO2 formation from [1-14C]octanoate. Pretreatment with 20 mM 4-pentenoate sharply reduced the respiratory and secretory responses to theophylline and histamine. Tracer studies showed a major utilization of exogenous octanoate over glucose and pyruvate by the in vitro toad gastric mucosa. Theophylline and histamine stimulated by 69% the rate of octanoate oxidation. Over 60% of the increments in oxygen uptake produced by theophylline and histamine accounted for the increments in octanoate oxidation, whereas glucose and pyruvate together accounted for less than 25%. Octanoate-dependent respiration was shown to correlate with octanoate oxidation under both inhibition with 4-pentenoate and stimulation with theophylline. Theophylline stimulated by 25% the rate of octanoate oxidation in Cl--free glucuronate-nutrient solutions. The present work provides further evidence for the primary role of fatty acid oxidation in the mechanism of acid secretion in amphibian.
Regulation of pancreatic acinar cell function by intracellular calcium
Authors: Williams J. A.
Published: December 2017

Enzyme secretion by the pancreatic acinar cell is regulated by the secretagogues acetylcholine (ACh) and cholecystokinin (CCK) that combine with specific membrane receptors and then induce a rise in cytoplasmic calcium. The evidence that Ca2+ mediates their actions is derived from studies demonstrating the dependence of enzyme secretion on both extracellular and intracellular Ca2+; the ability of these secretagogues to induce the release of bound or sequestered calcium; and the ability of the calcium ionophore A23187 to bypass the receptor, increase Ca2+ influx, and mimic ACh and CCK action. In contrast to many other secretory systems, however, the cellular Ca2+ that triggers secretion in response to ACh and CCK comes primarily from intracellular stores whose identity is not yet clearly established. In addition to stimulation of enzyme release, ACh and CCK have a number of other actions on pancreatic acinar cells including effects on memebrane transport and permeability, protein and lipid synthesis, and energy metabolism. At presnt, in addition to stimulating enzyme secretion, three actions of secretagogues have been clearly identified as being mediated by Ca2+: 1) stimulation of glucose transport; 2) membrane depolarization and its underlying increase in Na+ permeability; and 3) increased synthesis of cGMP. A model is presented in which intracellular Ca2+ functions as a regulatory mechanism to coordinate diverse but interrelated activities of the acinar cell.
Biphasic secretory response of exocrine pancreas to feeding
Authors: Itoh Z. , Honda R. , Hiwatashi K.
Published: December 2017

By means of a newly developed device, secretory response of the exocrine pancreas to feeding was continuously recorded for 24 h in conscious dogs. It was then found that the postprandial secretory pattern of the pancreas was biphasic. The first peak of secretion, rich in enzymes, occurred 2.3 +/- 0.11 h after feeding and its secretory volume was 25.3 +/- 3.10 ml/h. After the first peak, pancreatic secretion decreased slightly, but started to increase again. At 10.8 +/- 0.31 h after feeding, the second peak of secretion occurred and this was 40.5 +/- 2.93 ml/h, significantly higher than the first peak secretion and the greatest in 1 day. The second peak secretion did not contain a higher concentration of enzymes, but was rich in bicarbonate. Approximately 16 h after feeding, pancreatic secretion returned to the basal level, which continued until the next meal. That water and bicarbonate secretion of the pancreas is the greatest at about the 11th postprandial h had never been reported before. The physiological role of the pancreatic secretion at that time is more likely to be related to the neutralization of acid entering from the stomach than to the digestion of food.
Effect of atropine, ouabain, antimycin A, and A23187 on "trigger Ca2+ pool" in exocrine pancreas
Authors: Stolze H. , Schulz I.
Published: December 2017

45Ca2+ fluxes have been analyzed in dispersed acinar cells prepared from rat pancreas. Sudden addition of carbamylcholine (CCh) to 45Ca2+-preloaded acinar cells at quasi-steady state for 45Ca2+ resulted in a quick 45Ca2+ release followed by a slower 45Ca2+ reuptake with net accumulation of 45Ca2+. Subsequent sudden addition of atropine caused a further transient increase in cellular 45Ca2+ followed by a slow decrease to a steady-state value. 45Ca2+ release could not be evoked a second time by pancreozymin when prestimulated with CCh. However, if CCh stimulation was abolished by an interposed step of atropine, restimulation by cholecystokinin-pancreozymin was possible. Addition of A23187 or antimycin A to cells induced a fast decrease in cellular 45Ca2+. This effect was not additive to the CCh effect. In ouabain-pretreated cells, the CCh-induced sudden loss of cellular 45Ca2+ was blocked by 60%. The following slow reuptake of 45Ca2+ was blocked completely. Subsequent addition of atropine caused a fast uptake of cellular 45Ca2+ with no secondary decline. The data are consistent with the following model: acetylcholine releases Ca2+ from a cellular "trigger pool" into the cytosol located in or near the cell membrane. Then Ca2+ is extruded from the cell via Ca2+ pumps partly by a Na+-dependent Ca2+ transport system (quick phase of 45Ca2+ release). Subsequently, due to increased Ca2+ permeability of the plasma membrane as induced by acetylcholine, Ca2+ influx occurs and Ca2+ is taken up from the cytosol into intracellular Ca2+ pools (slow 45Ca2+ reuptake phase). Atropine causes refilling of the trigger Ca2+ pool and return of the increased Ca2+ permeability of the plasma membrane back to the unstimulated state.
Effect of chemically defined diets on antral and serum gastrin levels in rats
Authors: Sircar B. , Johnson L. R. , Lichtenberger L. M.
Published: December 2017

When rats were fed isocaloric amounts of chemically defined diets with variable amounts of protein (8-60%) or fat (0-30%) over a 10-day period, their serum and antral gastrin concentrations were, respectively, 60 and 40% lower than the levels of chow-fed rats. It was also determined that neither the low bulk content of these diets nor their inability to adequately buffer the gastric pH contributed to this response. The time course of this dietary-induced reduction in gastrin levels was investigated and it was found that the serum hormone levels were significantly reduced as early as 1-2 h after chow-fed rats were placed on these chemically defined diets. Antral gastrin levels were maintained at normal levels for 4-5 days after rats started consuming these synthetic diets and fell thereafter. With all of the chemically defined diets tested, the gastrin secretory response to a meal was significantly reduced. It therefore appears that synthetic diets lack some undefined food constituent present in chow that is required for the normal postprandial release of gastrin or, alternatively, that they contain an inhibitory factor which blocks the normal secretory response.
Calcium ATPase and intestinal calcium transport in uremic rats
Authors: Schiffl H. , Binswanger U.
Published: December 2017

Calcium ATPase, an enzyme involved in intestinal calcium transport, was measured in homogenates of duodenal mucosal scrapings of normal and uremic rats. The effects of calcium deprivation and treatment with 1 alpha,25-dihydroxycholecalciferol [1,25-(OH)2D3] were investigated as well. Uremia decreased the enzyme activity and impaired the rise after calcium deprivation as observed in intact rats. The 1,25-(OH)2D3 treatment increased the enzyme activity in uremic animals and resulted in an identical response to calcium deprivation as observed in intact rats; parathyroidectomy abolished this effect. A striking correlation between everted duodenal gut sac calcium transport and calcium ATPase activity could be demonstrated for all groups of rats studied. It is concluded that the calcium ATPase activity is linked to the production of 1,25-(OH)2D3 as well as to an additional factor, probably parathyroid hormone. The close relationship between enzyme activity and in vitro calcium transport, even during constant physiological supplementation with 1,25-(OH)2D3, suggests an autonomous role of the calcium ATPase activity for mediation of calcium transport in the duodenum in addition to the well-known mechanisms related to vitamin D and its metabolites.
Intrinsic control of colonic blood flow and oxygenation
Authors: Kvietys P. R. , Miller T. , Granger D. N.
Published: December 2017

In a denervated autoperfused dog colon preparation, arterial perfusion pressure, venous outflow pressure, blood flow, and arteriovenous O2 difference were measured during graded arterial pressure alterations, arterial occlusion, venous pressure elevation, venous occlusion, and local intra-arterial infusion of adenosine. As perfusion pressure was reduced from 100 to 30 mmHg, colonic blood flow decreased and arteriovenous O2 difference increased. Although blood flow was not autoregulated O2 delivery was maintained within 10% of control between 70 to 100 mmHg and then decreased with further reduction in perfusion pressure. Arterial occlusion (15, 30, and 60 s) resulted in a postocclusion reactive hyperemia; the magnitude of the hyperemia was directly related to the duration of occlusion. Venous occlusion resulted in a postocclusion reactive hypoemia. Elevation of venous pressure from 0 to 20 mmHg increased vascular resistance, O2 extraction, and the capillary filtration coefficient, but decreased O2 delivery. Infusion of adenosine decreased vascular resistance and O2 extraction, but increased O2 delivery. These data suggest that both metabolic and myogenic mechanisms are involved in the control of colonic blood flow and oxygenation.
Effect of external ions on 45Ca efflux from cat intestinal muscle
Authors: Curtis B. A. , Kreulen D. , Prosser C. L.
Published: December 2017

The surface-bound Ca of isolated circular smooth muscle of cat small intestine can be removed by substitution of LiCl for NaCl in Krebs solution. This substitution removed surface-bound Ca (45Ca) and allowed us to study transmembrane 45Ca efflux. Neither the resting membrane potential nor contractility changed when Li was substituted for Na. Li removed the same extracellular 45Ca store as did ethylene glycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid. The resting transmembrane 45Ca efflux was inhibited by La3+ and was unchanged in Li, tris(hydroxymethyl)aminomethane, arginine, and sucrose Krebs solution. The extra 45Ca efflux observed upon electrical stimulation was no greater in Na-Krebs than Li-Krebs, but during response to acetylcholine the extra 45Ca efflux was greater in Na-Krebs than Li-Krebs. We conclude that the surface-bound Ca is sensitive to external Na and that the transmembrane Ca efflux is not completely dependent on external Na.
Use of a model of small bowel mucosa to predict passive absorption
Authors: Levitt D. G. , Bond J. H. , Levitt M. D.
Published: December 2017

The purpose of this study was to determine if the observed rate of passive absorption of inert gases from the canine small bowel could be predicted by the use of an anatomical model of the mucosa and measurements of villus blood flow and the diffusive barrier to absorption. Villus blood flow was measured with microspheres and the diffusive barrier separating bulk luminal contents and blood was estimated from CO absorption. The model predicts initial uptake of the inert gases (H2, He, CH4, and 133Xe) in blood at the villus tip, subsequent countercurrent exchange in the villus, and longitudinal diffusion of the gases down the villus to a subvillus blood flow. Observed absorption rates for each of these four gases were reasonably accurately predicted by the model at both basal villus blood flow and at low villus blood flow induced by hypotension. We suggest that this model can be used to predict passive absorption kinetics over a range of villus blood flows and to predict the influence of a variety of parameters on the rate of passive absorption of diffusible substances.
Mechanism of glucagon-induced intestinal secretion
Authors: Granger D. N. , Kvietys P. R. , Wilborn W. H. , Mortillaro N. A. , Taylor A. E.
Published: December 2017

The effects of local intra-arterial glucagon infusion on transcapilary, lymphatic, and transmucosal fluid and protein fluxes were studied in autoperfused segments of cat ileum. The glucagon infusions resulted in a significant increase in intestinal blood flow, lymph flow, capillary filtration coefficient, capillary pressure, interstitial volume, and interstitial fluid pressure. Precapillary resistance and the pre-to-postcapillary resistance ratio decreased during the glucagon infusion. The transcapillary oncotic pressure gradient and the osmotic reflection coefficient were reduced, suggesting that capillary permeability is significantly increased with glucagon. Ultrastructural analysis of tissue samples acquired during the infusion of higher doses of glucagon indicates disruption of the mucosal membrane. An glucagon indicates disruption of the mucosal membrane. An alteration in mucosal structure is supported by the appearance of plasma proteins in the secreted fluid. The results of this study indicate that glucagon-induced intestinal secretion results from an alteration in capillary fluid balance, i.e., an increased capillary pressure and permeability.
Human upper esophageal sphincter pressure profile
Authors: Gerhardt D. , Hewett J. , Moeschberger M. , Shuck T. , Winship D.
Published: December 2017

The pressure profile of the upper esophageal sphincter was characterized in nine normal subjects. Directionally oriented intraluminal pressures were recorded, at 0.5-cm intervals over a 6-cm segment that encompassed the sphincter, by a high-fidelity low-compliance recording system. The peak resting pressure was directed posteriorly, and the lowest pressures were recorded from the lateral orientations. Significant axial asymmetry was observed with peak posterior pressure 0.55 cm more distal than the anterior pressure. Calculations of variability of pressures recorded at each interval showed the peak pressure to be the most reproducible measurement for each subject. Isotonic saline and acid infusions into the esophagus distal to the sphincter resulted in increased sphincteric peak resting pressure (acid greater than saline). There was axial lengthening of the sphincteric pressure zone with infusion of acid and saline, but this observed increase in length was not significant except at the 50 mmHg level. Pressure profiles recorded during 0.5-cm station pull-throughs were virtually identical to those obtained by a rapid continuous pull-through technique.
Electrical arrhythmias in gastric antrum of the dog
Authors: Gullikson G. W. , Okuda H. , Shimizu M. , Bass P.
Published: December 2017

Antral electrical arrhythmias were investigated in 32 unanesthetized chronic dog preparations implanted with serosal electrodes and transducers. Five of these animals underwent surgical removal of the duodenal cap and the adjacent hypomuscular segment. In the intact dogs two distinct types of arrhythmias of the basic electric rhythm (BER) were observed. During phase I (basal activity) arrhythmias were recorded in 17 of 32 dogs. In 9 of the 32 dogs, arrhythmias were present in more than 10% of recorded phase I activity. These arrhythmias included tachygastria as well as mixed gastric rhythms. A second type of arrhythmia consisting of premature and delayed BER occurred in all dogs during phase III (burst activity). In all five dogs, duodenal cap removal produced a marked increase in antral arrhythmias as well as the disruption of normal interdigestive motor and electrical patterns. The changes in terminal antral electrical rhythmicity after surgery may be due to an interaction with the higher frequency duodenal pacemaker tissue. Antral frequencies of 15-18 cycles/min in two of five dogs several days after cap removal were evidence of a duodenal influence. Antral arrhythmias may be present during both normal and pathophysiological states. Their importance is as an indicator of the functional status of the antral smooth muscle and its responsiveness to normal physiological and pharmacologic stimuli.
Effect of hydrocortisone on pancreatic growth in rats
Authors: Morisset J. , Jolicoeur L.
Published: December 2017

This study was undertaken to determine the effects of hydrocortisone on pancreatic size and composition in suckling, recently weaned, growing, and adult rats. The data demonstrate that hydrocortisone 1) is associated with hyperplasia and hypertrophy of the pancreas in suckling rats, 2) suppressed DNA synthesis in recently weaned rats, but maintained the hypertrphic effect, 3) increased protein and pancreatic hydrolase concentrations in growing and adult rats, and 4) preferentially promoted synthesis of amylase over chymotrypsin only during the suckling period. These experiments suggest that growth of the pancreas may be partly under control of glucocorticoids only during the suckling period, whereas hypertrophy of the pancreatic tissue can be obtained at all ages by these hormones.
Gastric emptying of ordinary food: effect of antrum on particle size
Authors: Meyer J. H.
Published: December 2017

The lack of reliably quantitative methods has delayed understanding how the stomach empties and processes foods. Rapid refinement of gamma cameras has prompted the development of several methods for labeling of ordinary foods with radionuclides. These methods allow rapid labeling with tightly adherent nuclides and are safe for studies both in animals and humans. Nuclide-labeled foods have also permitted detailed analyses of gastric emptying in animals prepared with chronic duodenal fistulas. Early results indicate that the stomach retains foods until these are fragmented into particles smaller than 0.5 mm in diameter, and that this sieving is achieved in the antral region of the stomach. The speed of fragmentation of foods into particles of this size as well as the speed of emptying appear to be closely regulated by chemoceptive mechanisms in the small intestine, which can inhibit these processes. Thus, chemical composition of the meal regulates gastric emptying as well as the physical nature of the food, which determines how easily it can be fragmented by the stomach.
pH dependence of micellar diffusion and dissociation
Authors: Shiau Y. F. , Levine G. M.
Published: December 2017

A simplified model system was used to examine the effect of pH on the diffusion and dissociation of mixed micelles across an interphase. Diffusion of radioactively labeled taurocholate and oleic acid from a micellar solution into a phosphate buffer of varying pH (5.0-8.0) was measured. The proportion of bile salt and fatty acid as monomers and aggregates in both solutions was determined by ultrafiltration. Results indicate that all of the oleic acid existed as aggregates in the micellar solution, whereas taurocholate was in equilibrium between aggregate and monomer forms. Between pH 5.0 and 7.0, oleic acid and taurocholate diffusion was inversely related to pH and due to the differences in aggregate but not monomer diffusion. Fatty acid diffusion across the interface was always less than taurocholate diffusion, because taurocholate monomers could also diffuse across the interphase. Calculation of the proportion of taurocholate diffusion from aggregate and monomers based on micellar composition was similar to measured values at pH greater than or equal to 6.5, indicating a lack of micelle dissociation. However, at pH less than or equal to 6 measured values for bile salt monomers exceeded calculations, indicating that a low pH microclimate favors dissociation of micelles. A hypothesis is advanced to explain these events occurring in a disequilibrium area adjacent to the epithelial cell membrane.
Effect of hydrophobic surfactant (Pluronic L-81) on lymphatic lipid transport in the rat
Authors: Tso P. , Balint J. A. , Rodgers J. B.
Published: December 2017

The effect of chronic feeding (3-4 wk) of the hydrophobic surfactant, Pluronic L-81, on the lymphatic transport of triglyceride and cholesterol was studied in rats with thoracic duct fistula. A lipid emulsion containing [3H]triolein (13.3 mM), [14C]cholesterol (2.6 mM), phosphatidylcholine (2.9 mM), sodium taurocholate (19 mM), with 0.17 mg/ml (experimental) or without Pluronic L-81 (L-81) added (control) was infused at the rate of 3 ml/h. Lymph triglyceride and cholesterol outputs were greatly impaired in the experimental rats compared to the control rats. The phospholipid output compared to the control was also reduced but to a lesser extent in the experimental rats. Comparable recovery of radioactive 3H-labeled lipid and [14C]cholesterol from the intestinal lumen of control and experimental rats showed that digestion and absorption were not impaired in the experimental rats. The distribution of mucosal 3H radioactivity in various lipid fractions showed no impairment in reesterification. The greatly depressed lymphatic lipid transport was associated with marked accumulation of absorbed lipid in enterocytes, suggesting that Pluronic L-81 interferes with lipoprotein assembly and/or exit of lipoproteins from the mucosal cells. The animals fed chronically for 4-6 wk regained their ability to transport lipid 24 h after termination of L-81 feeding. The effect of this agent, therefore, is readily reversible.
Effects of ethionine on digestive enzyme synthesis and discharge by mouse pancreas
Authors: Gilliland L. , Steer M. L.
Published: December 2017

The earliest changes noted during the evolution of pancreatitis induced by feeding mice a choline-deficient ethionine-supplemented (CDE) diet are an increase in the number of zymogen granules in pancreatic acinar cells and an increase in digestive enzyme content of the pancreas. We have studied the processes of protein and digestive enzyme synthesis and discharge at varying times after institution of the CDE diet, a choline-deficient diet (CD), and a diet containing ethionine but not choline-deficient (E). Both the CDE and E diets increased digestive enzyme content within 12 h of their institution. Both the CDE and E diets reduced the rate of protein and amylase synthesis and caused a marked reduction in the rate of protein and amylase discharge from the pancreas. These changes were greatest and were noted earliest in the CDE diet group. A marked reduction in secretagogue-induced in vivo and in vitro amylase discharge followed ingestion of either the CDE or E diet. These studies indicate that the increased pancreatic content of digestive enzymes noted after ingestion of the CDE and E diets results from an ethionine-induced decrease in the rat of digestive enzyme discharge. This phenomenon is enhanced by simultaneous choline deficiency. Subsequent intrapancreatic activation of zymogens may couple these changes in enzyme content to the development of hemorrhagic pancreatitis.
Secretion of H+ and K+ by bullfrog gastric mucosa: characterization of K+ transport pathway
Authors: Sen P. C. , Tague L. L. , Ray T. K.
Published: December 2017

The transport of K+ and H+ (both expressed as mueq/h) by in vitro chambered bullfrog (Rana catesbeiana) gastric mucosa have been studied under a variety of conditions such as anoxia, addition of p-chloromercuribenzene sulfonic acid (PCMBS) into the secretory solution, inclusion of ouabain in the nutrient solution, addition of thiocyanate (SCN-) into the mucosal solution, and replacement of nutrient chloride (Cl-) with sulfate (SO4(2-)), or gluconate (Gl). Anoxia reversibly reduced the H+ transport close to zero within 15 min and gradually reduces the K+ transport throughout the 2-h period of anoxia. The presence of 2.5 X 10(-4) M mucosal PCMBS in the histamine-stimulated mucosa increases the K+ transport, which is promptly reduced by changing the gas phase to 95% N2-5% CO2. Addition of ouabain to the nutrient solution of the histamine-stimulated mucosa with PCMBS on the mucosal side significantly (P < 0.05) reduces the K+ transport within 60 min. Addition of SCN- to the mucosal solution of a histamine-stimulated mucosa with regular nutrient or O, K+ nutrient and 10, K+ mucosal solution reduces the H+ transport to near zero within 60 min. This SCN- inhibition can be reversed by elevating secretory K+. Substitution of nutrient Cl- with SO4(2-) or Gl in the histamine-stimulated mucosa reversibly inhibits H+ transport and reduces K+ transport to a low level (0.7 +/- 0.05). Our data suggest that the K+ transport across the apical membranes of gastric cells is to a large extent a passive carrier-mediated process, and the transport of both K+ and Cl- are coupled at the apical membrane.
Liver extract and its free amino acids equally stimulate gastric acid secretion
Authors: Feldman E. J. , Grossman M. I.
Published: December 2017

Using intragastric titration in dogs with gastric fistulas, dose-response studies were carried out with liver extract and with a mixture of amino acids that matched the free amino acids found in liver extract. All solutions were adjusted to pH 7.0 and osmolality to 290 mosmol x kg-1. Doses are expressed as the sum of the concentrations of all free amino acids. At each dose studied (free amino acid concentration: 2.8, 5.6, 11, 23, and 45 mM), acid secretion in response to the free amino acid mixture was not significantly different from that of liver extract. The peak response to both liver extract and the free amino acid mixture occurred with the 23-mM dose and represented about 60% of the maximal response to histamine. The serum concentrations of gastrin after liver extract and the amino acid mixture were not significantly different. It is concluded that in dogs with gastric fistula, gastric acid secretion and release of gastrin were not significantly different in response to liver extract and to a mixture of amino acids that simulated the free amino acid content of liver extract.
Patterns of movement of liquids and solids through canine jejunum
Authors: Sarr M. G. , Kelly K. A.
Published: December 2017

Our aim was to determine whether interdigestive and digestive motor patterns influence the transit of liquids and solids through the jejunum. In six dogs, a 75-cm segment of jejunum was isolated from the intestinal stream, but myoneural continuity between the segment and the proximal bowel was maintained via a bridge of tunica muscularis. Recording electrodes were implanted on the segment. After recovery, the transit of liquids alone, solids alone, and liquids and solids given together were measured during phases I, II, and III of the interdigestive myoelectric complex and also 30 and 120 min after feeding. During fasting, transit of liquids was most rapid during phase III, slowest in phase I, and intermediate during phase II. After feeding, transit resembled that of phase II of fasting. Transit of spheres was slower, although the patterns of transit resembled those of liquids during fasting and after feeding. Transit of liquids was unaffected by spheres, but transit of spheres was speeded by liquids. We concluded that changes in interdigestive and digestive motor patterns exerted a marked effect on the pattern of transit of both liquids and solids through the jejunal segment.
Passage of proteins through membranes—old assumptions and new perspectives
Authors: Rothman S. S.
Published: December 2017

Page G391: S. S. Rothman. “Passage of proteins through membranes—old assumptions and new perspectives.” Page G391: left column, lines 4–5 should read: This is not merely a convenience, but an assumption central to the scientific endeavor. Page G394: left column, lines 29–34 should read: If we were to prevent or diminish the movement of fluid away from the site of secretion, enzyme secretion should continue unabated if it is accounted for by an exocytosislike process, and as a consequence the concentration of enzyme in the duct system should rise over time.
Mechanisms of intestinal fat absorption
Authors: Shiau Y. F.
Published: December 2017

Even though most of the major controversies regarding intestinal fat absorption have been resolved over the past three decades, our concepts of fat digestion and absorption continue to be modified, and new concepts have emerged. The purpose of this review is to summarize advances in our understanding of fat digestion and absorption since the topic was last reviewed by Johnston in 1968. The discussion will emphasize 1) the role of colipase and its interactions with lipase, bile salt micelle, and triglyceride substrate; 2) the importance of the unstirred water layer in fat absorption; 3) micellar formation and dissociation; 4) the role of fatty acid binding protein; 5) factors influencing the reesterification mechanisms in the intestine; and 6) intestinal contribution to lipoprotein and apoprotein production. The importance of these new concepts and the remaining gaps in our understanding of these complex digestive and absorptive processes are discussed.
Uptake and esterification of plant sterols by rat small intestine
Authors: Bhattacharyya A. K.
Published: December 2017

The commonly found plant sterols, beta-sitosterol, campesterol, and stigmasterol, differ structurally from cholesterol only in side chains but are absorbed in much smaller amounts than cholesterol. Because intestinal mucosal cell uptake and esterification are important steps in absorption, these were studied in vivo after feeding the sterols and in vitro using everted sacs of rat small intestine. The studies showed that campesterol uptake was significantly higher than that of beta-sitosterol, whereas stigmasterol uptake was extremely low throughout the intestine. The total intestinal content of campesterol was 2.223 mg/g or about 14% of the dose fed as compared with 1.496 mg/g or 7.4% for beta-sitosterol and only 0.392 mg/g or 2.3% for stigmasterol. Intestinal tissue concentration of esterified campesterol was higher than that of beta-sitosterol, whereas that of esterified stigmasterol was extremely low. The results suggest that campesterol absorption would be higher than that of beta-sitosterol; stigmasterol probably would not be absorbed in any significant amount because of its negligible uptake due to its inability to partition out of the mixed micelles. It appears that the structure of the side chain of a sterol is an important determinant for uptake and esterification, and probably absorption, in the small intestine.
Effects of sulfobromophthalein excretion on biliary lipid secretion in humans and dogs
Authors: Shafter E. A. , Preshaw R. M.
Published: December 2017

The effect of sulfobromophthalein (BSP) on biliary lipid secretion was investigated in 12 cholecystectomized subjects, using a duodenal marker-perfusion technique. A 1-h basal period was followed by intravenous BSP infusion over 3 h, achieving the maximal excretory rate (Tm). The calculated Tm was not different from the measured maximal output. At BSP Tm, bile salt secretion was unchanged, but phospholipid, cholesterol, and bilirubin secretion were markedly reduced. Biliary lipid composition changed accordingly, higher molar percent bile salts but lower phospholipid and cholesterol. In six cholecystectomized dogs with chronic duodenal fistulas, bile was collected directly from the common duct while bile salt secretion was maintained by intravenous taurocholic acid infusion. After a 2-h control period, sufficient BSP was added to create either maximal (Tm) or submaximal conditions. BSP did not alter bile salt secretion but caused a dose-related decrease in phospholipid and cholesterol secretion. Bilirubin excretion was also reduced, whereas bile flow increased. Thus, BSP is hydrocholeretic but decreases phospholipid, cholesterol, and bilirubin secretion in both humans and dogs. The effect on biliary lipid composition is probably through a physical interaction with biliary micelles.
Periodic contractions of the canine gallbladder during the interdigestive state
Authors: Itoh Z. , Takahashi I.
Published: December 2017

Interdigestive contractile activity of the gallbladder, the stomach, and the duodenum was measured by means of chronically implanted force transducers in five conscious dogs. During the interdigestive state, contractions of the gallbladder were identified to be closely associated with the initial period of phase II of the interdigestive migrating contractions (IMC) in the duodenum. The mean contractile force of the gallbladder during this phase was 6.5 +/- 0.77 g, which corresponded to approximately 80% of the force of the postprandial contractions. When the duodenum exhibited phase II contractions, the gallbladder had already returned to the resting level. Intravenous infusion of synthetic motilin induced IMC in the stomach and duodenum and during the initial period of motor response of the duodenum reproduced contractions in the gallbladder that were identical to the natural contractions as to their period and pattern. We cannot yet ascribe the interdigestive contractions observed in the gallbladder to the direct action of motilin, but the present study clearly indicates that the gallbladder contracts even in the interdigestive state, and the contractions are associated with the phase II contractions in the duodenum.
Transport and metabolism of water-soluble vitamins in intestine
Authors: Rose R. C.
Published: December 2017

An overview of intestinal absorption of water-soluble vitamins is presented. Evidence relating to absorption of ascorbic acid by the "sodium-gradient" hypothesis and folic acid by the "acidic microclimate" hypothesis is discussed. Over the last decade, vitamin absorption by the intestine has been attributed in large part to simple diffusion. Recently, however, this view has been changing as information continues to be gathered which suggests the participation of membrane-bound "carriers" in transport and the involvement of cellular enzymes in metabolism of the vitamins during absorption. The circumstances that make vitamin absorption difficult to investigate are described. A brief look toward the future stresses the types of information that will be helpful to acquire, identifies some technological advances that will promote progress, and discusses potential application of the results to health care. Some reasons are given for confusion that has prevailed in descriptions of vitamin absorption during the last decade; suggestions are made that might help investigators to correct this situation.
Mechanism of action of SCN in isolated gastric glands
Authors: Hersey S. J. , Chew C. S. , Campbell L. , Hopkins E.
Published: December 2017

Isolated gastric glands were used to study the mechanism of acid secretory inhibition by thiocyanate (SCN). It was found that SCN does not act as a competitive antagonist of histamine nor does SCN prevent the increase in cellular cAMP associated with histamine stimulation. SCN modifies but does not prevent the expansion of parietal cell canaliculi, indicating that this characteristic morphological transition does not require the actual formation of hydrochloric acid. Low doses (less than 5 mM) of SCN were found to inhibit aminopyrine accumulation, an index of acid formation, but do not inhibit either resting or stimulated respiration. Higher doses (greater than 10 mM) of SCN produce significant inhibition of stimulated but not resting respiration. These results indicate that SCN has two actions, i.e., inhibition of acid formation that requires low doses and inhibition of oxidative metabolism that requires higher doses. Incubation of glands in high-K+ (108 mM) medium leads to formation of an acid gradient in the absence of other secretagogues. The gradient was found to be transient, and its formation does not require oxidative metabolism, indicating that continued proton pumping is not required. Low doses of SCN were found to be more effective in dissipating the high-K+-induced gradient than a similar gradient induced by histamine stimulation. These results support the hypothesis that SCN inhibits acid secretion by increasing the rate of proton-gradient dissipation rather than interfering with a proton-pump mechanism.
Effects of methylprednisolone on electrolyte transport by in vitro rat ileum
Authors: Tai Y. H. , Decker R. A. , Marnane W. G. , Charney A. N. , Donowitz M.
Published: December 2017

Administration of the glucocorticoid methylprednisolone (MP) (30 mg/kg body wt for 3 days) to rats increased intestinal mucosal guanylate cyclase and Na-K-ATPase activities, short-circuit current (Isc), electrical potential difference (PD), net Na absorption, and net Cl secretion and reversed HCO3 transport from secretion to absorption. In the MP-treated animals, removal of HCO3 from both the mucosal and serosal bathing solutions increased Cl secretion but did not alter the Isc, PD, and net Na flux. Removal of Cl abolished the MP-induced increase in Isc but did not affect the MP-induced changes in net Na and HCO3 fluxes. At 6 h, after a single dose of MP, stimulation of guanylate cyclase activity was already maximal, whereas Na-K-ATPase activity was not detectably altered. The changes in intestinal transport properties present 6 h after MP treatment and associated with the increased guanylate cyclase activity were an increase in Isc and PD and a reversal of net Cl absorption to net secretion. These results suggest that an initial response to MP administration is a persistent increase in intestinal guanylate cyclase activity that mediates an electrogenic Cl secretory process, then is followed by a superimposed effect of increased Na-K-ATPase activity that mediates an increase in net Na absorption.
Measurement of portal–systemic shunting in the rat by using gamma-labeled microspheres
Authors: Chojkier M. , Groszmann R. J.
Published: December 2017

A method for determining the extent of portal-systemic shunting (PSS) is described and evaluated in lightly anesthetized (ketamine) rats. This method relies on the intrasplenic injection of 15-micrometers gamma-labeled spheres and the subsequent measurement of liver and lung radioactivities. After the splenic injection of the microspheres, a fraction of microspheres shunting the hepatic sinusoidal bed will be entrapped in the lungs. Thus, the ratio, lung/(lung + liver) radioactivities, will indicate the degree of PSS. The percent of PSS was determined in normal (n = 13; 1.2 +/- 0.3%), in cirrhotic (n = 9; 15.0 +/- 4.5%; P less than 0.01), and in portal vein-ligated animals (n = 14; 95.0 +/- 0.9%; P less than 0.001 for normal and cirrhotic). In addition, PSS was sequentially quantitated (n = 3) before (3.0%) and after (89%) partial portal vein ligation. The variability of PSS found in cirrhotic rats (0.7-41.0%) is in agreement with the reported data for PSS in patients. This technique, which is simple, rapid, and reproducible, allows the quantitation of PSS in small laboratory animals.