bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature dependence of high-affinity CCK receptor binding and CCK internalization in rat pancreatic acini
Authors: Williams J. A. , Bailey A. C. , Roach E.
Published: December 2017

125I-labeled cholecystokinin (CCK) binding and internalization were studied as a function of temperature in isolated rat pancreatic acini. At 37 degrees C, acini readily bound and degraded 125I-CCK. When labeled hormone binding was inhibited by increasing amounts of unlabeled CCK, competition-inhibition curves were biphasic, consistent with both high- (Kd, 18 pM) and low-affinity (Kd, 13 nM) binding sites. At 4 degrees C, acini bound only one-third as much 125I-CCK and degradation was essentially abolished. At 4 degrees C, CCK competition curves were consistent with a single class of low-affinity binding sites (Kd, 19 nM). Internalization of 125I-CCK was evaluated by three washing procedures utilizing acid, base, and trypsin. All were shown to remove membrane-bound 125I-CCK, and this finding was validated for trypsin by electron microscope autoradiography. After 1 h at 37 degrees C, washing showed 67% of bound 125I-CCK to be internalized and autoradiography showed 54% to be internalized. At 4 degrees C, internalization of bound CCK was greatly reduced but not abolished. When internalization of 125I-CCK was evaluated as a function of the medium concentration of CCK, both high- and low-affinity components were observed. These results suggest that high-affinity CCK binding and CCK internalization are separate temperature-sensitive processes. Moreover, internalization is not uniquely associated with high-affinity binding.
Digestive motor patterns and transit of luminal contents in canine ileum
Authors: Siegle M. L. , Ehrlein H. J.
Published: December 2017

In the present study ileal motor patterns caused by orally administered noncaloric and nutrient meals were investigated. Effects of nutrients were additionally elucidated by an ileal infusion of nutrients. Conscious dogs equipped with closely spaced extraluminal transducers were used. Motor patterns were quantified by a computerized method. Transit rates were measured fluoroscopically. Compared with the motor pattern caused by the noncaloric meal, the nutrient meal diminished the number of contractions from 11.7 to 5.9/min, reduced the incidence of contraction waves from 70.8 to 39.4%, shortened the length of contraction spread from 4.0 to 1.4 cm, and slowed the transit rate from 18.4 to 3.2 cm/min. Ileal infusion of nutrients induced a motor pattern similar to that of the nutrient meal. The transit rate correlated with the length of contraction spread (r = 0.75), the ratio between contraction waves and stationary contractions (r = 0.77), and the number of contractions (r = 0.69). The length of contraction spread was the most characteristic feature of motor patterns and the most important factor influencing transit.
Phosphorus nuclear magnetic resonance in isolated perfused rat pancreas
Authors: Matsumoto T. , Kanno T. , Seo Y. , Murakami M. , Watari H.
Published: December 2017

Phosphorus nuclear magnetic resonance spectroscopy was applied to measure phosphorus energy metabolites in isolated perfused rat pancreas. The gland was perfused with a modified Krebs-Henseleit solution at room temperature (25 degrees C). 31P resonances of creatine phosphate (PCr), ATP, ADP, inorganic phosphate (Pi), and phosphomonoesters (PMEs) were observed in all the preparations of pancreas. In different individual preparations, the resonance of PCr varied, but those of ATP were almost the same. The initial levels of PCr and ATP in individual preparations, however, remained almost unchanged during perfusion with the standard solution for 2 h. When the perfusion was stopped, the levels of ATP and PCr decreased, while the levels of PME and Pi increased. At that time, the Pi resonance shifted to a higher magnetic field, indicating that the tissue pH decreased. On reperfusion, the tissue levels of phosphorus compounds and the tissue pH were restored to their initial resting levels. Continuous infusion of 0.1 microM acetylcholine caused marked and sustained increases in the flow of pancreatic juice and protein output. During the stimulation the tissue levels of phosphorus compounds remained unchanged, while the tissue pH was decreased slightly (0.05 pH unit).
TRH analogue, RX 77368, injected into dorsal vagal complex stimulates gastric secretion in rats
Authors: Stephens R. L. , Ishikawa T. , Weiner H. , Novin D. , Tache Y.
Published: December 2017

Medullary sites inducing gastric acid secretion in response to microinjection of the stable analogue of thyrotropin-releasing hormone (TRH; RX 77368, pGlu-His-[3,3'-dimethyl]-Pro-NH2) were investigated in urethan-anesthetized rats. Gastric acid output was recorded every 2 min through a double gastric cannula constantly perfused with 0.9% saline solution maintained at pH 5.5 using an automatic titrator. Unilateral microinjection of RX 77368 (10-100 ng in 50-nl volume) into the dorsal vagal complex (DVC), the dorsal vagal nucleus and nucleus tractus solitarius, induced a significant dose-dependent stimulation of gastric acid secretion. The peak response occurred within 50 min and lasted over 1 h. Other medullary sites, including the lateral, dorsal, and parvocellular reticular nuclei; the medial longitudinal fasciculus; and the medial cuneate nucleus injected with RX 77368 (10-100 ng), were inactive. The TRH metabolites, TRH-OH and His-Pro diketopiperazine (100 ng), injected into the DVC did not influence gastric acid secretion. The stimulation of gastric acid secretion induced by DVC injection of TRH was abolished by vagotomy. These results demonstrate that 1) the DVC is an important site of action for TRH-induced stimulation of gastric acid secretion, 2) TRH action in the DVC is not secondary to the formation of TRH metabolites, and 3) the effect is expressed by vagal efferent pathways. These findings added to the high concentration of TRH-immunoreactivity and receptors in the DVC suggest a role for endogenous TRH in the regulation of vagal outflow to the stomach.
Visualization of amylase secretion from individual pancreatic acini
Authors: Bosco D. , Chanson M. , Bruzzone R. , Meda P.
Published: December 2017

To assess the secretion of individual rat pancreatic acini, we developed a reverse hemolytic plaque assay that allows for a direct visualization of amylase release. This release was detected around secreting cells by the presence of hemolytic plaques that resulted from the complement-mediated lysis of red blood cells bearing amylase-antiamylase complexes bound to protein A. Controls showed that these plaques reflected specifically the active secretion of amylase. Quantitation of hemolytic plaques showed that after a 30-min incubation approximately 50% of the acini secreted under basal conditions. Stimulation of amylase release by increasing concentrations of carbamylcholine resulted in a dose-dependent recruitment of secreting acini as well as in a time-dependent enhancement in the response of individual acini. Under all conditions, the wide distribution of hemolytic plaque sizes indicated large differences in the secretory output of individual acini. Thus, using a new method to directly visualize and quantitate amylase secretion, we have provided evidence for a functional heterogeneity of pancreatic acini.
Conversion of xanthine dehydrogenase to oxidase in ischemic rat intestine: a reevaluation
Authors: Parks D. A. , Williams T. K. , Beckman J. S.
Published: December 2017

Oxygen radicals derived from xanthine oxidase (XO) are important mediators of the cellular injury associated with reperfusion of ischemic intestine, stomach, liver, kidney, and pancreas. XO exists in nonischemic tissue predominantly as xanthine dehydrogenase (XDH) and converts to oxygen radical-producing XO with ischemia. Grinding intestine under liquid nitrogen and placing the powder in phosphate buffer (pH 7.0) containing thiol reductants and protease inhibitors adequately preserved total XDH + XO activity and the percentage in the oxidase form (%XO) for 24 h. Total activity in nonischemic intestine ranged from 374 nmol.min-1.g-1 in duodenum to 138 nmol.min-1.g-1 in ileum, while XO activity was approximately 19% of total activity throughout the entire small intestine. The rate of XDH conversion to XO during normothermic ischemia varied only slightly throughout the intestine, increasing 13% per hour to 34, 46, and 61% XO after 1, 2, and 3 h of ischemia, respectively. Our results contrast with previous reports where XDH conversion to XO occurred within 60 s ischemia but are consistent with physiological and morphological evidence of ischemic injury and provide further support for involvement of XO in intestinal injury associated with ischemia.
Characterization of receptors for calcitonin gene-related peptide on gastric smooth muscle cells
Authors: Maton P. N. , Sutliff V. E. , Zhou Z. C. , Collins S. M. , Gardner J. D. , Jensen R. T.
Published: December 2017

Rat calcitonin gene-related peptide (rat CGRP) and related peptides did not cause contraction of gastric smooth muscle cells; however, preincubation with rat CGRP or human CGRP inhibited smooth muscle contraction caused by carbachol. Rat CGRP and human CGRP were equipotent in opposing contraction with a half-maximal effect produced by 0.1 nM, but rat calcitonin-adjacent peptide (rat CAP) and human calcitonin had no effect. Rat CGRP caused an increase in cellular adenosine 3',5'-cyclic monophosphate (cAMP) of 60%, which was augmented to 155% with 1 mM isobutyl methylxanthine (IBMX). IBMX did not influence the sensitivity of the muscle cells to rat CGRP to increase cAMP, the half maximal effect being produced by 0.4 nM in the presence or absence of IBMX. Rat CGRP and human CGRP were equipotent for stimulating cAMP, but rat CAP and human calcitonin had no effect. Binding of 125I-CGRP was temperature dependent, saturable, reversible, and specific. Rat CGRP and human CGRP were equipotent at inhibiting binding of 125I-CGRP and rat CAP, and human calcitonin did not inhibit binding. For rat CGRP and human CGRP, the dose-response curves for binding of 125I-CGRP were broad, and both peptides accelerated the rate of dissociation of bound 125I-CGRP. Computer analysis of dose-response curves demonstrated two classes of binding sites for CGRP, one with a high affinity (Kd 3 nM) and another with low affinity (Kd 3,700 nM). Our results indicate that CGRP interacts with previously undescribed receptors on gastric smooth muscle cells to increase cellular cAMP and inhibit contraction.
Quinine decreases hepatocyte transmembrane potential and inhibits amino acid transport
Authors: Wondergem R. , Castillo L. B.
Published: December 2017

Effects of L-alanine, 2-(methylamino)isobutyric acid (MeAIB), and quinine on mouse hepatocyte transmembrane potential (Vm) are compared with effects of quinine on MeAIB transport into isolated mouse hepatocytes in primary monolayer culture. In liver slices, L-alanine (10 mM) decreased Vm 6 +/- 0.4 mV from control Vm (-37 +/- 0.2 mV). With L-alanine still present, Vm repolarized and stabilized at Vm of -2 +/- 0.5 mV greater than control Vm. Quinine (1 mM) decreased Vm reversibly by 7 +/- 0.9 mV. Depolarization was 11 +/- 1.5 mV when L-alanine and quinine were added together, but now Vm did not repolarize. Transient depolarization also resulted from addition of either L-alanine or MeAIB to isolated hepatocytes in primary culture. Moreover, quinine (1 mM) inhibited steady-state MeAIB uptake by 91%. Quinine decreased Vmax for MeAIB transport from 9.0 +/- 1.0 to 4.8 +/- 1.9 nmol MeAIB.mg protein-1.4 min-1, but it did not change Km of 0.60 mM. Quinine inhibition of MeAIB transport was reversible. Quinine also increased hepatocyte steady-state volume from 3.2 +/- 0.8 to 4.9 +/- 1.2 microliter/mg protein. Thus quinine may inhibit Na+-amino acid cotransport by blocking conductive K+ channels, thereby decreasing Vm and the transmembrane electrochemical Na+ gradient, and it may deplete the intracellular amino acid pool by disrupting hepatocyte volume regulation.
Ontogenesis of intestinal taurine transport: evidence for a beta-carrier in developing rat jejunum
Authors: Moyer M. S. , Goodrich A. L. , Rolfes M. M. , Suchy F. J.
Published: December 2017

Taurine, a sulfur-containing beta-amino acid, may be conditionally essential during development. However, the existence of a carrier system for beta-amino acids has not been demonstrated in brush-border membrane vesicles (BBMV) from adult rat jejunum. We studied the uptake of [3H]taurine in BBMV prepared from the jejunum of developing and adult rats using a cation-precipitation technique. Uptake of 10 microM [3H]taurine by adult BBMV was slightly enhanced in the presence of an inwardly directed 100 mM Na+ gradient compared with a K+ gradient, and there was no intravesicular accumulation of isotope above the equilibrium concentration ("overshoot"). In contrast, taurine transport by BBMV from 10-day-old rat pups was markedly accelerated in the presence of a Na+ gradient compared with a K+ gradient and a twofold overshoot was observed. Na+-dependent taurine uptake was inhibited by the structural analogues hypotaurine and beta-alanine but not by alpha-alanine or glutamine, which are amino acids served by other transport systems. By computer analysis, Na+-dependent taurine uptake (2-1,000 microM) was saturable with an apparent Km of 74.80 +/- 11.87 microM and a Vmax of 53.55 +/- 2.76 pmol.mg protein-1.min-1. With increasing postnatal age, there was a marked decrease in the initial rate and peak intravesicular accumulation of taurine with disappearance of the overshoot by 21 days of age. We conclude 1) a Na+-dependent carrier mechanism for taurine transport is present in the brush-border membrane of suckling rat jejunum and 2) the activity of this carrier decreases after weaning.(ABSTRACT TRUNCATED AT 250 WORDS)
Restitution of barrier and transport function of porcine colon after acute mucosal injury
Authors: Argenzio R. A. , Henrikson C. K. , Liacos J. A.
Published: December 2017

Acute injury of the porcine colonic epithelium was induced in vivo with the bile salt, deoxycholate. A concentration of 15 mM for 30 min completely destroyed the surface epithelium and induced a marked increase in mucosal permeability to mannitol. The crypt epithelium however was not significantly affected. Within 8 min of recovery, the colonic surface was reepithelialized with flattened, migrating cells, and within 40 min, mucosal permeability to mannitol was normalized. In vitro studies showed that in these early stages of recovery, NaCl transport, short-circuit current, and resistance were markedly impaired, whereas the theophylline-induced secretory response remained intact. Recovery of absorptive function paralleled the transition from flattened to columnar surface epithelium and was complete within 2 h. Results suggest that 1) active migratory events play an important role in rapid restitution of an epithelial barrier, 2) active absorption of ions is much slower to recover, and 3) active secretory events are intact and probably originate in the crypt epithelium.
Release of secretin along the canine small intestine
Authors: Fried M. , Fink A. S. , DeSouza L. R. , Beglinger C. , Gyr K. , Meyer J. H.
Published: December 2017

The profile of secretin release along the entire canine small intestine was examined in this study. Four equal loops of the small gut, from the duodenal bulb to the ileocoecal valve, were isolated. In eight anesthetized dogs the four segments were perfused for 40 min each in random order with an acidified (pH 2.5) emulsion of 20 mM oleic acid. In four dogs control experiments were performed using 0.15 M saline. Secretin release in portal venous blood was measured by a sensitive radioimmunoassay. Although secretin was mainly released in the first quarter of the small intestine (310 pM X 40 min), large amounts of secretin, 33% of the total secretin release, were liberated in the second quarter of the small intestine (164 pM X 40 min). Minute amounts of secretin (23 pM X 40 min) were released in the third quarter, whereas perfusion of the last quarter of the small gut failed to release secretin. We conclude that the major portion of secretin is releasable in the first quarter of the small gut. High amounts of secretin can be liberated in the second quarter of intestine, an area that is probably never exposed to pH below 4.5 (the known threshold for secretin release by acid), but is still exposed to fatty acids (other releasers of secretin).
Regulatory signals for intestinal amino acid transporters and peptidases
Authors: Ferraris R. P. , Kwan W. W. , Diamond J.
Published: December 2017

Dietary protein ultimately regulates many processes involved in protein digestion, but it is often unclear whether proteins themselves, peptides, or amino acids (AAs) are the proximate regulatory signal. Hence we compared several processes involved in protein digestion in mice adapted to one of three rations, identical except for containing 54% of either casein, a partial hydrolysate of casein, or a free AA mixture simulating a complete hydrolysate of casein. We measured brush-border uptakes of seven AAs that variously serve as substrates for four AA transporters, and brush-border and cytosolic activities of four peptidases. The three rations yielded essentially the same AA uptake rates. Peptidase activities tended to be lower on the AA ration than on the protein ration. In other studies, all three rations yielded the same rates of brush-border peptide uptake; protein is only modestly more effective than AAs at inducing synthesis of pancreatic proteases; and, depending on the animal species, protein is either much less or much more effective than AAs at stimulating release of cholecystokinin and hence of pancreatic enzymes. Thus the regulators of each process involved in protein digestion are not necessarily that process's substrate. We call attention to other cases in which the functional significance of regulatory signals remains to be understood.
A simple method for chronic cannulation of the portal vein in intact unrestrained rats
Authors: Braillon A. , Brody M. J.
Published: December 2017

A simple new method is described for chronic cannulation of the portal vein in rats. A Silastic catheter (0.64 mm OD) with an internal metallic leader is directly inserted in the junction of the two small ileal veins. The catheter is advanced into the mesenteric vein to the portal vein. Then the leader is removed and the catheter tunneled out the back of the neck. This method allows for the measurement of portal vein pressure, direct injection of substances in the portal vein, or blood samples for at least 1 wk in intact unrestrained rats. Validation included the presence of elevated portal vein pressure in portal hypertensive rats compared with normal rats and the absence of clot development in the portal vein. This method should help provide a better understanding of hepatic physiology and pharmacology in normal and disease states.
Protein digestion in human and rat small intestine: role of new neutral endopeptidases
Authors: Guan D. , Yoshioka M. , Erickson R. H. , Heizer W. , Kim Y. S.
Published: December 2017

Two new phosphoramidon-insensitive neutral endopeptidases were identified and partially characterized in the brush-border membrane of rat and human intestine using N-CBZ-L-Ala-L-Arg-L-Arg-4-methoxy-beta-naphthylamide (Z-Ala-Arg-Arg-MNA) and azocasein or alpha-casein as substrates. Activities in the brush-border membrane of both rat and human intestine were maximum at neutral to alkaline pH, were inhibited by metal chelating and thiol reagents, and were insensitive to phosphoramidon. The results also indicate that these endopeptidases are distinct from pancreatic proteases. The biochemical properties of the enzyme hydrolyzing Z-Ala-Arg-Arg-MNA were shown to be different from that hydrolyzing azocasein or alpha-casein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration revealed that several native intact protein substrates were rapidly degraded to small molecular weight peptides and amino acids when incubated with rat or human brush-border membrane preparations. During in vivo intestinal perfusion in rats, 11% of the total administered alpha-casein was hydrolyzed and absorbed by the intestine. The results suggest that phosphoramidon-insensitive endopeptidases in the intestinal brush-border membrane may be of nutritional and physiological importance in protein digestion.
Patch-clamp study of single-channel and whole-cell K+ currents in guinea pig pancreatic acinar cells
Authors: Suzuki K. , Petersen O. H.
Published: December 2017

K+ channels in the plasma membrane of isolated guinea pig pancreatic acini were studied by patch-clamp single-channel and whole-cell current recording techniques. Three types of K+-permeable pores were found in excised patch experiments: Ca2+-activated nonselective cation channels with a unit conductance of approximately 25 pS that could be inhibited by ATP acting on the membrane inside, and two kinds of Ca2+- and voltage-activated K+-selective channels with unit conductances (in symmetrical K+-rich solutions) of about 200 and 30 pS, respectively. In intact cells, pentagastrin activation of currents through the 30 pS K+-selective pores was demonstrated. In these experiments pentagastrin was added to the bath solution and had no direct contact with the electrically isolated membrane area from which the single-channel currents were recorded, suggesting that the activation is mediated via an intracellular messenger system. Pentagastrin stimulation of voltage-gated K+ currents was also observed in whole-cell recording experiments. Results from these experiments suggest that in the stimulated condition the membrane electrical properties were dominated by the 30 pS K+-selective channels.
CNS regulation of gastric and autonomic functions in dogs by gastrin-releasing peptide
Authors: Lenz H. J.
Published: December 2017

The central nervous system effects of canine gastrin-releasing peptide (GRP) were studied on gastric acid secretion, emptying, blood flow, and the autonomic nervous system in conscious dogs. GRP injected into the third cerebral ventricle significantly (P less than 0.01) increased plasma epinephrine but not norepinephrine concentrations. GRP (0.1-1.0 nmol/kg) significantly decreased gastric acid secretion stimulated by an 8% peptone meal, delayed gastric emptying of the liquid peptone meal, and increased left gastric artery flow. Ganglionic blockade, truncal vagotomy, or adrenalectomy did not abolish the inhibitory effect of GRP on gastric acid secretion. However, ganglionic blockade or vagotomy abolished the GRP-induced inhibition of gastric emptying, and ganglionic blockade or adrenalectomy abolished the GRP-induced increases in left gastric artery flow and plasma epinephrine concentrations. An intravenous infusion of epinephrine that produced similar plasma concentrations of epinephrine that were observed after cerebroventricular injection of GRP mimicked the increase in left gastric artery flow induced by GRP. It is concluded that 1) GRP acts within the central nervous system to activate the sympathoadrenal axis, 2) GRP inhibits gastric emptying of a liquid meal by a vagally dependent mechanism and enhances left gastric artery flow by the release of epinephrine from the adrenal medulla, and 3) the pathway(s) that mediate the GRP-induced inhibition of gastric acid in the dog remain unknown.
Canine gallbladder cyclic motor activity
Authors: Matsumoto T. , Sarna S. K. , Condon R. E. , Dodds W. J. , Mochinaga N.
Published: December 2017

We investigated whether the gallbladder has cyclic motor activity similar to that of the stomach, lower esophageal sphincter, and sphincter of Oddi in the fasted state. We found that the canine gallbladder infundibulum exhibited a cyclic burst of short duration (69 +/- 3 s) contractions that were closely associated with phase III activity of the antrum. The cyclic motor activity was sometimes less prominent or absent in the body and the fundus of the gallbladder. The mean period of gallbladder cyclic motor activity was not significantly different from the mean period of phase III activity in the stomach and the duodenum. The cyclic bursts of gallbladder contractions lasted for 21 +/- 2 min. The gallbladder cyclic motor activity started at about the same time as the antral phase III activity, and both of these activities started approximately 12 min earlier than the duodenal phase III activity. In addition to the aforementioned cyclic bursts of contractions, the gallbladder sometimes exhibited long duration (6.4 +/- 0.6 min) contractions that occurred irregularly and unpredictably during the duodenal migrating motor complex cycle. We conclude that during fasting the canine gallbladder has a cyclic motor activity that is temporally related to phase III activity of the stomach and the duodenum. The role of short duration phasic contractions during cyclic motor activity may be to periodically stir gallbladder contents, whereas the long duration contractions may partially empty the gallbladder in the fasted state.
Cholecystokinin receptors on gallbladder muscle and pancreatic acinar cells: a comparative study
Authors: von Schrenck T. , Moran T. H. , Heinz-Erian P. , Gardner J. D. , Jensen R. T.
Published: December 2017

To compare receptors for cholecystokinin (CCK) in pancreas and gallbladder, we measured binding of 125I-Bolton-Hunter-labeled CCK-8 (125I-BH-CCK-8) to tissue sections from guinea pig gallbladder and pancreas under identical conditions. In both tissues, binding had similar time-, temperature-, and pH dependence, was reversible, saturable and inhibited only by CCK related peptides or CCK receptor antagonists. Autoradiography localized 125I-BH-CCK-8 binding to the smooth muscle layer in the gallbladder. Binding of 125I-BH-CCK-8 to gallbladder sections was inhibited by various agonists with the following potencies (IC50):CCK-8 (0.4 nM) greater than des(SO3)CCK-8 (0.07 microM) greater than gastrin-17-I (1.7 +/- 0.3 microM) and by various receptor antagonists with the following potencies: L364,718 (1.5 nM) greater than CR 1409 (0.19 microM) greater than asperlicin = CBZ-CCK-(27-32)-NH2 (1 microM) greater than Bt2cGMP (120 microM). Similar potencies were found for the agonists and antagonists for pancreas sections. Inhibition of binding of 125I-BH-CCK-8 by 11 different analogues of proglumide gave similar potencies for both pancreas and gallbladder. The potencies of agonists in stimulating and antagonists in inhibiting CCK-stimulated contraction or amylase release correlated closely with their abilities to inhibit 125I-BH-CCK-8 binding to gallbladder or pancreas sections or acini, respectively. The present results demonstrate and characterize a method that can be used to compare the CCK receptors in guinea pig gallbladder and pancreas under identical conditions. Moreover, this study demonstrates that gallbladder and pancreatic CCK receptors have similar affinities for the various agonists and antagonists tested and, therefore, provides no evidence that they represent different subtypes of CCK receptors that can be distinguished pharmacologically.
Gastrin secretion by gastrinoma cells in long-term culture
Authors: Elouaer-Blanc L. , Sobhani I. , Ruszniewski P. , Duet M. , Lehy T. , Mignon M. , Bonfils S. , Lewin M. J.
Published: December 2017

Gastrinoma cells from surgical specimens of a primary pancreatic tumor and an hepatic metastasis in two patients with a Zollinger-Ellison syndrome were grown and subcultured for 7 mo. Cultured cells displayed a strong reactivity to heptadecapeptide gastrin antibody and maintained an ultrastructural appearance resembling that of the original tumor cells with the presence of secretory granules of variable size and electron density. Cultured cells also showed the ability to secrete immunoreactive gastrin, and this secretion was further concentration-dependently stimulated by secretin (10(-10)-10(-6) M), carbachol (10(-6) M), and bombesin (10(-10)-10(-6) M). The latter peptide was the more potent stimulant with a maximal effect at 10(-9) M (460 +/- 20% of basal release; P less than 0.05). This stimulation occurred in the absence of extracellular Ca2+ and was potentiated by the addition of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP; 10(-3) M) into the culture medium. The somatostatin analogue, somatostatin-(201-995), did not alter basal gastrin release but inhibited secretin, carbachol, and bombesin stimulation. Moreover, DBcAMP (10(-3) M) and Ca2+ (1-3 mM) stimulated gastrin release; Ca2+ ionophore A23187 (6 micrograms/ml) enhanced gastrin response to Ca2+ in the early time intervals of incubation. Furthermore the phorbol ester derivative, 12-O-tetradecanoyl phorbol-13-acetate, dramatically stimulated gastrin release (10 times the basal value). We conclude that gastrinoma cells can be cultured over an extended period with maintenance of their capacity to secrete gastrin in response to various hormones and mediators.(ABSTRACT TRUNCATED AT 250 WORDS)
Absorption and metabolism of orally fed arachidonic and linoleic acid in the rat
Authors: Nilsson A. , Melin T.
Published: December 2017

[3H]arachidonic [( 3H]20:4) and [14C]linoleic acid [14C]18:2) were fed to rats in Intralipid or cream. Later (30-240 min) the stomach, small intestine, plasma, and liver were analyzed for radioactivity in different lipid classes. [3H]20:4 and [14C]18:2 were emptied from the stomach and absorbed by the intestine at similar rates. The [3H]20:4:[14C]18:2 ratio of the lipids in the small intestinal wall increased, however, with time. This was due to a higher retention of [3H]20:4 than [14C]18:2 in intestinal phospholipids. In contrast, more of the [14C]18:2 was in triacylglycerol of the small intestine and plasma. The highest 3H:14C ratios were found in phosphatidylethanolamine and phosphatidylinositol. The 3H:14C ratio of intestinal phosphatidylcholine varied with the type of fat vehicle used, being highest in the Intralipid experiments. After feeding Intralipid (30-60 min), significantly more of the plasma [3H]20:4 than plasma [14C]18:2 was in diacylglycerol, the 3H:14C ratio of which was much higher than that of plasma free fatty acids. [3H]20:4 and [14C]18:2 of chyle triacylglycerol are thus metabolized differently.
Manometric investigation of high-amplitude propagated contractile activity of the human colon
Authors: Bassotti G. , Gaburri M.
Published: December 2017

The motor activity of colonic segments proximal to the rectosigmoid junction are poorly understood. We investigated colonic peristalsis (high-amplitude propagated contractions; HAPCs) in 20 healthy volunteers by means of a colonoscopically positioned manometric probe and low-compliance infusion system. In all, 110 HAPCs were recorded from the ascending, transverse, descending, and sigmoid colon, and their features and daily distribution were analyzed and characterized. Mean frequency was 6.1 +/- 0.9 (SE) per subject per 24 h, mean amplitude was 110.37 +/- 6.3 mmHg, mean duration was 14.15 +/- 0.8 s, and mean propagation velocity was 1.11 +/- 0.1 cm/s. There were no significant differences among colonic segments. Diurnal changes of HAPCs were also noted, with a maximum frequency after meals and after awakening in the morning, and a minimum recorded in the late afternoon and during the night. These HAPCs may represent the manometric equivalent of mass movements.
Patterns of fast synaptic cholinergic activation of neurons in the celiac ganglia of cats
Authors: Niel J. P. , Clerc N. , Jule Y.
Published: December 2017

Fast nicotinic transmission was studied in vitro in neurons of isolated cat celiac ganglia. In the absence of nerve stimulation, neurons could be classified into three types: silent neurons, synaptically activated neurons, and spontaneously discharging neurons. In all three types, fast synaptic activation could be obtained in single neurons by stimulating with a single pulse both the splanchnic nerves or one of the peripheral nerves connected to the ganglia. During repetitive nerve stimulation, a gradual depression of the central and peripheral fast nicotinic activation occurred, which was not affected by phentolamine plus propranolol, domperidone, atropine, or naloxone. Repetitive nerve stimulation was followed by a long lasting discharge of excitatory postsynaptic potentials and action potentials that decreased gradually with time. This discharge, which was probably due to presynaptic or prejunctional facilitation of acetylcholine release from cholinergic terminals, was reduced by the application of phentolamine plus propranolol, domperidone, or atropine and increased with naloxone. The existence of the mechanisms described in this study reflects the complexity of the integrative processes at work in neurons of the cat celiac ganglia that involve fast synaptic cholinergic activation.
Characteristics of chloride ion influx in Amphiuma small intestine
Authors: White J. F.
Published: December 2017

Net Cl- absorption by Amphiuma small intestine is electrogenic but associated with the secretion of HCO3-. To define the mechanisms of Cl- entry into the enterocytes the initial rate of uptake of 36Cl into isolated segments of small intestine was measured. Luminal extracellular space was measured using [3H]inulin. Cl- influx was saturable with a Km of 5.3 mM. When the mucosal medium Cl- concentration was 20 mM influx was linear for 5 min. Cl- influx in 5 min (JiCl) was not reduced by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid added to the serosal medium, although the Cl- current was abolished. Hence the luminal membrane was the barrier to Cl- uptake. Monovalent anions blocked Cl- influx in the order I- = SCN- = NO3- greater than Br- greater than F-. Anoxia and dinitrophenol reduced JiCl 33 and 71%, respectively. Substitution of medium Na+ with choline or N-methyl glucamine reduced JiCl 60-70%. Removal of medium K+ reduced influx 51%. After medium Na+ and K+ were both replaced influx was stimulated upon reexposure to (Na+ + K+); Na+ alone did not stimulate. JiCl was reduced 34% by furosemide. Neither amiloride nor SITS in the mucosal medium altered influx. JiCl was reduced by replacement of the HCO3- -CO2 buffer with either phosphate or N-2-hydroxyethyl-piperazine-N'-2-ethanesulfonic acid and by exposure to acetazolamide. Theophylline reduced influx 60%, whereas the Ca ionophore A23187 reduced net Cl- absorption and lowered JiCl by 17%. Norepinephrine (10(-5) M) in the serosal bathing medium stimulated Cl- influx 51%. These results indicate that Cl- influx into the intestinal mucosa occurs by a Na+- and, possibly, K+-dependent pathway. Cl- entry is under adrenergic influence.
Involvement of substance P in noncholinergic excitation of rabbit colonic muscle
Authors: Koelbel C. B. , Mayer E. A. , Reeve J. R. , Snape W. J. , Patel A. , Ho F. J.
Published: December 2017

Neurokinins have been implicated as noncholinergic excitatory neurotransmitters in the mammalian gastrointestinal tract. To characterize the myogenic and neurogenic response of colonic muscle to neurokinins we studied the mechanical response of muscle strips from proximal and distal colon and the release of [3H]acetylcholine in response to substance P (SP), neurokinin A (NKA) and neurokinin B (NKB). All neurokinins caused a dose-dependent inotropic response. SP was 80 times more potent in distal compared with proximal longitudinal muscle. The rank order of potencies in proximal longitudinal muscle was NKA greater than SP = NKB and in distal muscle NKA = SP = NKB. Desensitization to SP or pretreatment with a SP antagonist inhibited the mechanical response to SP and the atropine-resistant inotropic off response to electrical stimulation. Only longitudinal muscle from distal colon had an atropine- and hexamethonium-sensitive inotropic component to SP. In contrast, all three peptides were equipotent in releasing [3H]acetylcholine from longitudinal muscle strips preincubated with [3H]choline. These results suggest the following: 1) SP is a potent agonist of rabbit colon with a proximal distal gradient in biological potency; 2) the myogenic response of the distal colon appears to be mediated through a NK-1 receptor; and 3) SP is a major mediator of the noncholinergic component of the off response in distal longitudinal muscle.
Mechanisms contributing to gastric motility changes induced by PAF-acether and endotoxin in rats
Authors: Esplugues J. V. , Whittle B. J.
Published: December 2017

Platelet-activating factor (PAF) may be involved in the pathophysiology of gastrointestinal damage and motility changes. The effects of PAF in inducing gastric contractions in vivo have now been determined in pentobarbital sodium-anesthetized rats. Local intra-arterial infusion of PAF (5-50 ng.kg-1.min-1 for 10 min) induced a maintained rise in intragastric pressure followed by a further postinfusion increase. Inhibitors of eicosanoid biosynthesis had no effect on these gastric motility changes. However, pretreatment with cimetidine or methysergide decreased by 50% the initial increase in intragastric pressure, whereas mepyramine, adrenergic alpha- and beta-receptor blockade, atropine, hexamethonium, or vagotomy had no effect. During the local infusion of tetrodotoxin, the initial increase in intragastric pressure was not maintained, and the postinfusion increase was abolished. With these inhibitors and antagonists, there was no consistent correlation between the extent of PAF-induced mucosal damage and increase in intragastric pressure. Tetrodotoxin had no effect on the changes in intragastric pressure induced by the thromboxane mimetic U-46619. Administration of Escherichia coli and Salmonella typhosa endotoxin (50 mg/kg iv) also increased intragastric pressure, which peaked after 10 min and slowly declined thereafter. These effects were inhibited by the specific PAF-receptor antagonist L652,731, suggesting that the endogenous release of PAF may contribute to the endotoxin-induced increases in gastric motility. The present study suggests that PAF initially acts directly on smooth muscle and through histamine and serotonin release with a secondary motility response due to activation of nonadrenergic noncholinergic, neuronal activity.
Regulation of bombesin receptors on pancreatic acini by cholecystokinin
Authors: Younes M. , Wank S. A. , Vinayek R. , Jensen R. T. , Gardner J. D.
Published: December 2017

When guinea pig pancreatic acini are first incubated with the COOH-terminal octapeptide of cholecystokinin (CCK-8), washed, and then reincubated with 125I-[Tyr4]bombesin (125I-[Tyr4]BN) there is a significant decrease in binding of 125I-[Tyr4]BN compared with that observed with pancreatic acini that have been first incubated with no additions. The CCK-8-induced decrease in binding is maximal after 90 min of first incubation is abolished by reducing the temperature of the first incubation from 37 to 4 degrees C or by adding L364,718 to the first incubation and cannot be reproduced by first incubating acini with A23187, 8-bromoadenosine 3',5'-cyclic monophosphate (8Br-cAMP), 8-bromoadenosine 3',5'-cyclic monophosphate (8Br-cGMP), or 12-O-tetradecanoylphorbol 13-acetate. 125I-[Tyr4]BN interacts with a single class of receptors on pancreatic acini, and first incubating acini with CCK-8 decreases the affinity of BN receptors for BN with no change in the maximal binding capacity. CCK-8 does not alter the rate at which bound 125I-[Tyr4]BN dissociates from pancreatic acini; therefore, CCK-8 must alter the rate at which the radiolabeled BN analogue associates with its receptor. Pancreatic acini possess two classes of CCK receptors: one has a high affinity for CCK-8; the other has a low affinity for CCK-8. The dose-response curve for CCK-8-induced inhibition of binding of 125I-[Tyr4]BN appears to to reflect occupation of low-affinity CCK receptors by CCK-8.(ABSTRACT TRUNCATED AT 250 WORDS)
Immunological regulation of colonic ion transport
Authors: Russell D. A. , Castro G. A.
Published: December 2017

Challenge of distal colonic epithelium from Trichinella spiralis-infected guinea pigs with parasite-derived antigen elevated short-circuit current (Isc) for approximately 60 min. The maximum elevation (delta Isc) was approximately 250 microA/cm2 at 5 min after the addition of trichinella antigen. The antigen-induced alterations in Isc were of greater magnitude and duration than those evoked in jejunum. Colonic electrical resistance was transiently reduced after exposure to antigen. There was no significant effect of antigen on electrical parameters of colon from nonimmunized (uninfected) guinea pigs. The antihistamine pyrilamine (10(-5) M) and the prostaglandin synthesis inhibitor indomethacin (10(-6) M) reduced the colonic Isc response to antigen by 40% when used in combination but had insignificant effects when used singly. In contrast, the jejunal Isc response to antigen was totally eliminated by the combined use of those inhibitors. Antigenic stimulation of sensitized colon released histamine and prostaglandin E2 (PGE2). However, the histamine released was only about one-tenth that stimulated by antigen in the jejunum, and PGE2 released was only one-tenth of that stimulated by bradykinin in the colon. PGE2 was not released after antigenic stimulation of jejunum. The antigen-induced colonic delta Isc was reduced approximately 50% by either furosemide or tetrodotoxin. Although histamine- and indomethacin-sensitive factors contribute greatly to the mediation of the antigen-induced delta Isc in jejunum, these autacoids contribute to a lesser extent to the antigen-induced delta Isc in guinea pig colon.
Linkage between somatostatin and acid secretion: evidence from use of pertussis toxin
Authors: Schubert M. L. , Hightower J. , Makhlouf G. M.
Published: December 2017

Pertussis toxin was used to examine the functional linkage between somatostatin and acid secretion and the mode of action of somatostatin at the cellular level in the isolated luminally perfused mouse stomach. Pretreatment of the stomach with pertussis toxin (125-1,250 ng/ml) for 60 min 1) caused a significant twofold increase in histamine-stimulated acid secretion (from 42 +/- 7 to 82 +/- 12 nmol/min; P less than 0.01) but not pentagastrin-stimulated secretion and 2) blocked the inhibitory effect of somatostatin on basal and histamine-stimulated acid secretion but not on pentagastrin-stimulated acid secretion. The ability of pertussis toxin to reverse selectively the inhibitory effect of somatostatin on histamine-stimulated acid secretion is consistent with the ability of pertussis toxin to inactivate a guanine nucleotide binding protein, which couples somatostatin receptors to inhibition of adenylate cyclase; histamine, but not gastrin, stimulates acid secretion via activation of adenylate cyclase. Secretagogue-stimulated acid secretion was accompanied by a parallel increase in somatostatin secretion that is largely determined by luminal acidity. The augmentation of histamine-stimulated acid secretion after treatment with pertussis toxin implied that the concomitant increase in somatostatin secretion is coupled to acid secretion and acts to attenuate it. The results confirm the role of gastric somatostatin as a paracrine regulator of acid secretion.
A cholecystokinin releasing peptide mediates feedback regulation of pancreatic secretion
Authors: Lu L. , Louie D. , Owyang C.
Published: December 2017

Diversion of bile pancreatic juice from the duodenum in rats stimulates cholecystokinin (CCK) release and pancreatic enzyme secretion. Intraduodenal perfusion of trypsin inhibits the release of CCK and pancreatic enzyme secretion. We hypothesized that the increased pancreatic enzyme secretion after pancreatic juice diversion is mediated by a trypsin-sensitive peptide secreted by the small intestine that stimulates release of CCK. To test this hypothesis, rats were surgically prepared with bile-pancreatic cannula and intestinal fistulas. Diversion of bile-pancreatic juice stimulated amylase output fivefold above basal and increased plasma CCK from a basal of 0.5 +/- 0.05 pM to 14 +/- 5 pM. Rapid perfusion (3 ml/min) of the duodenum with phosphate-buffered saline reversed the increase in amylase output and lowered the plasma CCK to 1.2 +/- 0.2. Administration of intestinal perfusate (3 ml/min) collected from a donor rat into the duodenum of a recipient rat with diversion of bile pancreatic juice increased amylase output threefold above basal and increased plasma CCK. The stimulatory activity of the intestinal perfusate was inactivated by treatment with trypsin but not by amylase or lipase. In addition, boiling did not alter the stimulatory activity of the intestinal perfusate. Perfusion of intestinal perfusate from donor rats pretreated with atropine did not stimulate amylase output and CCK release in recipient rats. By use of molecular membrane exclusion filters, stimulatory activity was retained (between 1,000 and 5,000). These results indicate that feedback regulation of pancreatic enzyme secretion is mediated by a CCK releasing peptide whose secretion from the duodenum is cholinergically mediated. This peptide is trypsin sensitive and has a molecular weight between 1,000 and 5,000.
Amino acid transport across the hen colon: interactions between leucine and lysine
Authors: Munck B. G.
Published: December 2017

Several neutral amino acids such as leucine added on the mucosal side stimulate the mucosal-to-serosal flux (Jm----s) of cationic amino acids such as lysine. We show here in the colon of the NaCl-loaded hen that this is a result of interactions at the basolateral membrane. The hen colon was used because it tolerates prolonged incubation and has a relatively short tip of villus-to-muscularis mucosa distance. Two models have been proposed for the interpretation of the effect of mucosal-side addition of leucine on Jm----s of lysine: 1) one of an allosteric effect of cytoplasmic leucine on lysine efflux across the basolateral membrane; and 2) one of asymmetric heteroexchange of leucine from outside the basolateral membrane for cytoplasmic lysine. These two models were tested by measurements of influx across the brush-border membrane, of Jm----s and serosal-to-mucosal flux, and of steady state epithelial uptake of leucine and lysine. The data favor the model of allosteric interaction and are inconsistent with the model of asymmetric heteroexchange.
Migrating myoelectric complex demonstrated in four avian species
Authors: Clench M. H. , Pineiro-Carrero V. M. , Mathias J. R.
Published: December 2017

The migrating myoelectric complex (MMC) is demonstrated in four avian species: three gallinaceous birds (Gallus, Phasianus, Coturnix) and an owl (Strix). The complex in birds is strikingly similar to the MMC that is known in mammalian species. It has the same basic pattern of quiescence, followed by a period of irregular spike activity, then a period of intense regular spike activity, and finally a return to quiescence. The frequency and duration of avian MMCs are similar to those of mammals, but the propagation velocity and slow-wave frequency are slower. Granivorous birds (Gallus, Phasianus) and carnivores (Strix) exhibit the same basic motility patterns whether in the fed or fasted states. Interspecific differences occur, however, in the details of frequency, propagation velocity, duration, and slow-wave frequency. The closely related galliforms (chickens, pheasants) are more similar to each other in MMC characteristics than either is to the more distantly related owls.