bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased lymphocyte transport by lipid absorption in rat mesenteric lymphatics
Authors: Miura S. , Sekizuka E. , Nagata H. , Oshio C. , Minamitani H. , Suematsu M. , Suzuki M. , Hamada Y. , Kobayashi K. , Asakura H. , et al.
Published: December 2017

The effect of olive oil administration on lymphocyte transport through mesenteric lymphatics was examined to see the possible involvement of nutritional absorption in lymphocyte traffic from the intestinal mucosa. After the olive oil administration to rats, remarkable increase in lymphocyte flux was observed within 2 h in lymph samples collected from rats with lymphatic fistula. The use of a high-speed microscopic video system made it possible to analyze accurately the lymphocyte transport in rapid movement that could not be detected by any of the ordinary video systems. The direct observation of mesenteric collecting lymphatics by this system showed an increment of lymphocyte transport from the intestinal mucosa by lipid absorption in 2 h. The contraction frequency of intestinal collecting lymphatics was also enhanced by olive oil administration. The densitometric analysis on video image was applied to estimate the extent of lipid absorption. The combination of a high-speed video system and the densitometric analysis revealed that the increase in lymphocyte flux occurred before lipid absorption reached its maximum and also demonstrated that the lymphocyte transport returned to control levels under the maximal absorptive condition. The results suggest that the fat absorption could be an important factor influencing the lymphocyte transport in the lymphatic system of intestine.
Influence of motilin and cholecystokinin on sphincter of Oddi and duodenal mobility
Authors: Muller E. L. , Grace P. A. , Conter R. L. , Roslyn J. J. , Pitt H. A.
Published: December 2017

The sphincter of Oddi and the duodenum exhibit cyclical activity in phase with the migrating myoelectric complex. Both motilin and cholecystokinin have been shown to modulate gastrointestinal and sphincter of Oddi motility. However, previous studies have not monitored the effects of these hormones on simultaneously recorded sphincter of Oddi and duodenum pressures. The present investigation was undertaken, therefore, to determine the influence of both motilin and cholecystokinin on simultaneously recorded sphincter of Oddi and duodenal motility. In seven anesthetized prairie dogs, a triple-lumen, side-hole, pressure-monitored perfusion catheter was positioned with the proximal port in the sphincter of Oddi and the distal port in the duodenal lumen. Sphincter of Oddi and duodenal motility was recorded before and during 20-min infusions of motilin and cholecystokinin octapeptide (CCK-8) at 1, 10, and 100 ng.kg-1.min-1. Both hormones produced dose-related increases in sphincter of Oddi and duodenal motility. No response was observed with either hormone at 1 ng.kg-1.min-1. At 10 ng.kg-1.min-1, the duodenum was slightly more sensitive to motilin than to CCK-8, while the sphincter of Oddi was equally affected by both hormones. At 100 ng.kg-1.min-1, both hormones stimulated the sphincter of Oddi and the duodenum equally. These data indicate that in the prairie dog, both motilin and cholecystokinin stimulate sphincter of Oddi and duodenal motility.
Giant migrating contractions and their myoelectric correlates in the small intestine
Authors: Sarna S. K.
Published: December 2017

We investigated the characteristics of spontaneously and pharmacologically induced giant migrating contractions (GMC) in the small intestine of conscious dogs. Myoelectric and contractile activities were recorded from eight sites, 40-70 cm apart, by surgically implanted bipolar electrodes and strain-gauge transducers, respectively. In addition to the usual phasic contractions in the fasted state, we observed spontaneous GMCs that generally originated in the mid or distal small intestine and migrated caudad. These contractions occurred infrequently and irregularly. The amplitude and duration of these giant contractions were severalfold larger than those of usual phasic contractions during phase III activity. The giant contractions migrated caudad at a velocity of approximately 1 cm/s. These contractions were preceded and followed by a period of inhibition of spontaneous motor activity. Some dogs whined and showed restlessness when giant contractions originated in the mid to upper small intestine. Intravenous morphine at 20, 50, 100, and 200 micrograms.kg-1 .h-1 or gastric instillation of 100 ml of 60% vinegar solution also initiated GMCs whose characteristics were similar to those of spontaneous GMCs. The GMC in response to these stimuli originated at more proximal sites than the spontaneous giant contractions. The GMC in response to morphine infusions occurred repeatedly, but in response to vinegar they occurred only once as a burst of contractions. These agents did not induce GMCs in the fed state. In most cases, the upstroke of a giant contraction was associated with a brief burst of electrical response activity. In some cases the burst of response activity lasted for the entire duration of giant contractions.
Gradual reintroduction of oxygen reduces reperfusion injury in cat stomach
Authors: Perry M. A. , Wadhwa S. S.
Published: December 2017

Recent studies have shown that oxygen-derived free radicals are responsible for a major portion of ischemia-reperfusion injury in the stomach. The oxygen radicals are produced during reperfusion when oxygen delivery to the tissue increases. In the present study we investigate the effect on mucosal injury of regulating the rate of reintroduction of oxygen to the stomach after ischemia. Local gastric ischemia was achieved by reducing celiac artery pressure to 30 mm Hg for 1 h. Ischemic injury was assessed by measuring the loss of 51Cr-labeled red blood cells across the gastric mucosa. Mucosal blood loss was negligible before and during the ischemia period but increased to 0.178 ml.min.-1.100 g-1 during reperfusion. When blood flow to the stomach was gradually returned to normal after ischemia by increasing celiac artery pressure by 10 mmHg every 10 min, the mucosal blood loss was reduced to 0.013 ml.min.-1.100 g-1. If the stomach was vascularly perfused with low PO2 (34 mmHg) blood for 1 h after ischemia before being returned to normal arterial perfusion, the mucosal blood loss was also reduced to 0.063 ml.min.-1.100 g-1. When the stomach was made hypoxemic for 1 h rather than ischemic by perfusing the vasculature with low PO2 (29 mmHg) blood then reperfused with normoxic blood, there was very little mucosal bleeding (0.014 ml.min.-1.100 g-1). The data indicate that gastric mucosal bleeding after ischemia is reduced if the tissue is returned slowly to a normal PO2. These findings support the concept that reperfusion injury is due largely to the production of oxygen radicals.(ABSTRACT TRUNCATED AT 250 WORDS)
Receptors for insulin-like growth factors I and II in rat gastrointestinal epithelium
Authors: Laburthe M. , Rouyer-Fessard C. , Gammeltoft S.
Published: December 2017

Distinct receptors for insulin-like growth factors (IGFs) have been characterized in rat intestinal epithelium using 125I-labeled IGF-I and 125I-labeled IGF-II. In jejunal epithelial plasma membranes, IGF-I receptors were observed with a dissociation constant (Kd) of 7.2 nM and a binding capacity of 0.56 pmol/mg protein. Distinct IGF-II receptors were also found with a Kd of 9.5 nM and a binding capacity of 2.61 pmol/mg protein. For IGF-I receptors the following order of affinity was observed: IGF-I greater than IGF-II greater than insulin greater than proinsulin. IGF-II receptors recognize IGF-II with a 20-fold higher affinity than IGF-I and display no cross-reactivity with insulin and proinsulin. Affinity labeling of intestinal membranes also discriminates between the two types of receptors, revealing a radioligand-receptor complex of relative molecular weight (Mr) 130,000 using 125I-IGF-I and 250,000 for 125I-IGF-II under reducing conditions. Separation of proliferative crypt cells from mature villus cells in the small intestine makes it possible to show that a gradient of IGF receptors is present along the crypt-villus axis. 125I-IGF-I and 125I-IGF-II binding is 4.0- and 1.8-fold higher in crypt cells than in villus cells, respectively. Specific 125I-IGF binding is detectable throughout the gastrointestinal tract. The level of IGF binding is similar in stomach, small intestine, and cecum, but higher values are observed in colon.
Electrical behavior of myenteric neurons in guinea pig distal colon
Authors: Wade P. R. , Wood J. D.
Published: December 2017

Intracellular recording was used in vitro to analyze electrophysiological properties of neurons in myenteric ganglia of guinea pig distal colon. The neurons were classified into six types based on their electrical behavior. Type 1 colonic neurons discharged action potentials throughout depolarizing current pulses and were otherwise similar to S/type 1 neurons found in the guinea pig small bowel. The second type had passive and active electrical properties similar to those of AH/type 2 myenteric neurons of the small intestine. These cells discharged only a single spike at the onset of depolarizing current pulses, and the spikes were followed by long-lasting hyperpolarizing afterpotentials. Excitability of the type 2 neurons was enhanced in the presence of elevated Mg2+ and reduced Ca2+, and the spikes were unaffected by tetrodotoxin. Type 3 colonic neurons showed fast synaptic potentials but did not generate action potentials. The majority of neurons were referred to as type 2 colonic neurons. Type 4 neurons discharged single action potentials only at the onset of depolarizing current pulses, and the spikes were not followed by prolonged hyperpolarizing afterpotentials. Unlike type 2 neurons, excitability remained unchanged in the presence of reduced extracellular Ca2+ and elevated Mg2+. Action potentials of type 4 neurons were suppressed or abolished by tetrodotoxin. A group of spontaneously active neurons was classified as type 5 colonic neurons. Type 6 cells were inexcitable and assumed to be glial cells.
Role of pancreatic enzymes on release of cholecystokinin-pancreozymin in response to fat
Authors: Watanabe S. , Lee K. Y. , Chang T. M. , Berger-Ornstein L. , Chey W. Y.
Published: December 2017

In dogs prepared with either pancreatic duct ligation (PDL) or chronic pancreatic fistula (PF), we investigated the effect of pancreatic enzymes on release of cholecystokinin (CCK) in response to corn oil in the upper small intestine. In control dogs without PDL, intraduodenal administration of corn oil (Lipomul containing 15 mmol of triglyceride) resulted in a marked and sharp increase in plasma CCK concentration during the 1st h, which then decreased during the following 1.5 h. In PDL dogs, on the other hand, no immediate increase occurred during the 1st 45 min after which a modest but gradual increase occurred in plasma CCK concentration during the following 2 h. Likewise, plasma CCK concentration increased significantly when Lipomul predigested with pancreatic enzymes or oleic acid was administered to PDL dogs. The increase was comparable to the response to Lipomul alone in control dogs. The infusion of Lipomul resulted in similar responses of plasma CCK in PF dogs as were found in PDL dogs when pancreatic juice was diverted to the exterior from the duodenum. The increases in plasma CCK paralleled the pancreatic protein secretion, and a significant correlation was found between plasma CCK concentration and the protein output. The present observations indicate that release of endogenous CCK by fat from the upper small intestine depends on an adequate digestion of neutral fat by pancreatic enzymes. Thus pancreatic enzymes play an important role on release of CCK in response to a neutral fat.
Physiological measurement of luminal stirring in perfused rat jejunum
Authors: Anderson B. W. , Levine A. S. , Levitt D. G. , Kneip J. M. , Levitt M. D.
Published: December 2017

Poor stirring of intestinal contents yields a preepithelial diffusion barrier that is thought to be the rate-limiting step in absorption of many compounds. In many previous studies, the resistance of this barrier is equal to an unstirred water layer of 300-800 micron. Using three probes, CO, glucose, and [14C]warfarin, we measured the preepithelial resistance in a 30-cm segment in rats that were 1) conscious, 2) anesthetized with pentobarbital sodium, or 3) anesthetized and laparotomized. Measurements with each of the probes showed that the maximal preepithelial resistance in conscious rats was equivalent to an unstirred layer of only approximately 100 micron. Anesthesia roughly doubled this resistance, and anesthesia and laparotomy caused a sixfold increase (unstirred layer of approximately 600 micron). We conclude that the luminal stirring is much more efficient than previously has been appreciated. The very thick jejunal unstirred layers reported previously (300-800 micron) reflect the results of studies performed under nonphysiological conditions or studies employing inappropriate techniques to measure luminal stirring.
Hepatocyte cotransport of taurocholate and bilirubin glucuronides: role of microtubules
Authors: Crawford J. M. , Gollan J. L.
Published: December 2017

Modulation of bile pigment excretion by bile salts has been attributed to modification of canalicular membrane transport or a physical interaction in bile. Based on the observation that a microtubule-dependent pathway is involved in the hepatocellular transport of bile salts, we investigated the possibility that bilirubin glucuronides are associated with bile salts during intracellular transport. Experiments were conducted in intact rats (basal) or after overnight biliary diversion and intravenous reinfusion of taurocholate (depleted/reinfused). All rats were pretreated with intravenous low-dose colchicine or its inactive isomer lumicolchicine. Biliary excretion of radiolabeled bilirubin glucuronides derived from tracer [14C]bilirubin-[3H]bilirubin monoglucuronide (co-injected iv) was unchanged in basal rats but was consistently delayed in depleted/reinfused rats. This was accompanied by a significant shift toward bilirubin diglucuronide formation from both substrates. In basal Gunn rats, with deficient bilirubin glucuronidation, biliary excretion of intravenous [14C]bilirubin monoglucuronide-[3H] bilirubin diglucuronide was unaffected by colchicine but was retarded in depleted/reinfused Gunn rats. Colchicine had no effect on the rate of bilirubin glucuronidation in vitro in rat liver microsomes. We conclude that a portion of the bilirubin glucuronides generated endogenously in hepatocytes or taken up directly from plasma may be cotransported with bile salts to the bile canalicular membrane via a microtubule-dependent (vesicular?) mechanism.
Antropyloroduodenal activity during gastric emptying of liquid meals in humans
Authors: Dooley C. P. , Valenzuela J. E.
Published: December 2017

The present study examines the possible roles of the pylorus and the proximal duodenum in the gastric emptying of two liquid meals in six healthy volunteers. Gastric emptying of a saline meal (150 mM) and an acid meal (120 mM hydrochloric acid) were measured by the double-sampling dye dilution technique while antroduodenal motility was monitored with a continuously perfused catheter system. Pyloric region pressures were measured with a Dent sleeve. The acid meal (t1/2 = 13.5 +/- 1.8 min) emptied significantly (P less than 0.01) slower than the saline meal (t1/2 = 3.5 +/- 0.7 min). This slowing in the emptying of the acid meal was associated with significant (P less than 0.05) increments in tonic pyloric activity and phasic contractions of the proximal duodenum. Thus the gastric emptying of liquid meals is a complex process involving all components of the gastroduodenal region.
Gastric mucosal ornithine decarboxylase: localization and stimulation by gastrin
Authors: Johnson L. R. , Tseng C. C. , Tipnis U. R. , Haddox M. K.
Published: December 2017

Gastrin injection and refeeding fasted rats are effective trophic stimuli for the oxyntic gland mucosa of the stomach. Neither stimulus increases detectable ornithine decarboxylase (ODC) activity in the tissue. Difluoromethylornithine (DFMO), a potent inhibitor of ODC, blocks the mucosal growth response, indicating that ODC activity is necessary for growth. Elevated levels of spermidine and spermine are detectable in the mucosa after gastrin administration. Using a highly specific, polyclonal antiserum to ODC, we determined that the enzyme is present in oxyntic gland mucosa confined to a narrow band of cells at the base of the gastric pits and openings of the glands. In antral mucosa, ODC is present throughout the lower 20% of the mucosa, which consists of the necks and pyloric glands. Using antiserum dilution techniques, we show that gastrin administration increases immunoreactive ODC in the oxyntic gland area but not in the antral mucosa, where it has no trophic effect. Elevated cellular content of ODC is apparent within 2 h after injection of gastrin, peaks at 4 h, and declines to basal levels by 12 h. Gastrin-stimulated increase in ODC is confined to the narrow band of cells in which low levels of the enzyme protein were detected in control animals. The decarboxylating activity detectable in oxyntic gland mucosal extracts is not inhibited by administration of DFMO or cycloheximide, each of which inhibits ODC activity in other tissues. Addition of unlabeled lysine to the decarboxylation assay reaction of oxyntic gland mucosa extract inhibits the decarboxylation of radiolabeled ornithine substrate. Thus it is likely that the stomach possesses nonspecific decarboxylase activity, which accounts for most of the measured activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of membrane potential and cellular ATP on glutathione efflux from isolated rat hepatocytes
Authors: Fernandez-Checa J. C. , Ren C. , Aw T. Y. , Ookhtens M. , Kaplowitz N.
Published: December 2017

total glutathione (GSH) efflux was studied in isolated rat hepatocyte suspensions at repleted GSH content (45-55 nmol/10(6) cells). The increase in concentrations of medium K+ in place of Na+ caused a parallel fall in membrane potential and total GSH efflux. Ouabain (1 mM) and replacement of Na+ with choline caused a gradual fall in membrane potential and GSH efflux. Hyperpolarization of hepatocytes with lipophilic anions, thiocyanate, and nitrate was associated with significantly increased efflux. Total GSH efflux was inhibited by increasing concentrations of fructose, antimycin A, and carbonyl cyanide p-trifluoromethoxyphenylhydrazone, and there was a direct relationship between the rate of efflux and cellular ATP. Changes in total GSH efflux were paralleled by changes in GSH determined by high-performance liquid chromatography. Vanadate markedly inhibited efflux but caused only a modest decrease in cellular ATP. Fructose, antimycin A, and vanadate did not affect membrane potential or cell volume under the conditions at which efflux was inhibited. These results suggest independent requirements for both membrane potential and ATP in the transport of GSH.
[3H]saxitoxin as a marker for canine deep muscular plexus neurons
Authors: Ahmad S. , Allescher H. D. , Manaka H. , Manaka Y. , Daniel E. E.
Published: December 2017

The objectives of this study are 1) to examine the potential of [3H]saxitoxin binding as a marker for the neuronal membranes in canine small intestinal muscle membrane preparations, 2) to develop a synaptosomal preparation from deep muscular plexus, and 3) to partially characterize [3H]saxitoxin binding to this fraction. A purified synaptosomal fraction, relatively low in the smooth muscle plasma membrane marker enzyme 5'-nucleotidase but enriched in [3H]saxitoxin binding (2,592 fmol/mg), was obtained on sucrose density gradient. Vasoactive intestinal peptide immunoreactivity was also highest (51.82 pmol/mg protein) in this fraction. The binding was rapid at 20 degrees C with quick and complete dissociation after the addition of excess unlabeled tetrodotoxin (TTX). Scatchard analysis of the saturation binding data revealed a single population of binding sites (Bmax = 5,705 fmol/mg protein). The affinity constants calculated from the kinetic and saturation data were in close agreement (Kd = 0.26 and 0.69 nM, respectively). TTX competed for the binding (Ki = 2.1 nM), whereas veratridine and guanidinium hydrochloride did not. Monovalent and divalent cations had differential effects on the binding.
Esophageal responses to transient and sustained esophageal distension
Authors: Paterson W. G. , Rattan S. , Goyal R. K.
Published: December 2017

With the use of intraluminal manometry in alpha-chloralose-anesthetized opossums, distal esophageal and lower esophageal sphincter responses to prolonged midesophageal balloon distension were compared with those evoked by single transient distensions, vagal efferent stimulation, and swallowing. Balloon inflation caused sphincteric relaxation that recovered during small volume but persisted during large volume-prolonged distension. The esophageal body was either quiescent or exhibited nonperistaltic contractions during prolonged distension. Balloon deflation induced non-peristaltic esophageal and sphincteric contractions as well as further sphincter relaxation. Responses to prolonged large and small volume balloon distension resembled those evoked by high- and low-frequency vagal efferent stimulation, respectively. However, vagal-stimulated "on" contractions were not seen with balloon distension, and atropine did not modify excitatory responses occurring during or after prolonged distension. Although transient distension induced peristaltic esophageal contractions, the peristaltic velocity was faster than swallow-induced peristalsis. With transient distension, atropine prolonged the latency to contraction in the mid but not the distal smooth muscle segment and thus increased peristaltic velocity. These studies demonstrate that 1) esophageal distension evokes a wide spectrum of lower esophageal sphincter and esophageal body response, and 2) cholinergic neurons play a minimal role in distension-induced responses of the distal esophageal circular muscle below the distending balloon.
Culture behavior of healthy bovine gallbladder muscularis smooth muscle cells
Authors: Sas D. , Miller L. J.
Published: December 2017

In contrast to the extensive experience culturing vascular smooth muscle cells, little is known about the culture behavior of gastrointestinal smooth muscle cells. In this work, we have studied smooth muscle cells from bovine gallbladder muscularis in culture. Properties reflecting their state of differentiation, including cellular morphology, multicellular arrangements, intermediate filament protein expression, and content of contractile proteins, were studied after dispersed cell preparations were placed into short- and long-term culture on a variety of substrates. Immunocytochemical analysis of intact healthy gallbladder wall demonstrated that the muscularis smooth muscle cells express actin and the intermediate filament protein desmin, while being vimentin-negative. In this tissue they are, however, surrounded by sheets of vimentin-positive fibroblasts. Optimal microdissection of mucosa and serosa from the muscularis therefore still produced a combination of smooth muscle cells and fibroblasts; however, multiple strategies for enriching the yield and purity of muscularis smooth muscle cells for culture were partially successful. Like vascular smooth muscle cells in culture, these visceral smooth muscle cells rapidly underwent morphological dedifferentiation, losing their contactile phenotype. By 5 days in culture, the desmin-positive muscle cells took on a spread, fibroblast-like morphology, likely representing modulation to a proliferative, dedifferentiated state. After long-term culture, the muscle cells were observed to regain some markers of differentiation, but they were never observed to attain complete morphological and functional redifferentiation.
Pancreatic growth after partial resection of normal and enlarged pancreas in rats fed soya flour
Authors: Oates P. S. , Morgan R. G.
Published: December 2017

Pancreatic growth was studied after partial resection of the normal-sized pancreas in rats fed heated soya flour (HSF) or the enlarged gland in rats fed raw soya flour (RSF). Resection involved the removal of the splenic and gastric segments and in both the normal and enlarged gland this represents a loss of approximately 55% of total pancreatic mass. After partial resection animals were either continued on these preresected diets or changed to the alternative diets. For at least the first 8 days after resection, in all conditions studied, there was a significant increase in DNA synthesis in the pancreas, involving both parenchymal and nonparenchymal cells as shown by autoradiography. The increased cell turnover was not associated with any increase in total DNA content of the gland, indicating that the increase paralleled cell loss in response to injury caused by the surgery. By 160 days after resection of the normal pancreas, RSF feeding caused both hypertrophy and hyperplasia of the remnant, but after partial resection of the enlarged gland, growth was limited to hypertrophy. These results suggest that the pancreas has a limited capacity for additional growth after that initially caused by RSF.
Action of the cholecystokinin antagonist L364,718 on gastric emptying in the rat
Authors: Green T. , Dimaline R. , Peikin S. , Dockray G. J.
Published: December 2017

Cholecystokinin (CCK) is a potent inhibitor of gastric emptying. We have examined the effects of a novel potent peripheral CCK receptor antagonist (L364,718) on the action of endogenous and exogenous CCK octapeptide (CCK-8) on gastric emptying in the rat. In conscious gastric fistula rats, the recovery of liquid test meals of 3.0 ml (containing phenol red as a dilution marker) was determined over periods up to 8 min. Compared with saline, gastric emptying of solutions of peptone (4.5%), 50 mM HCl, and hyperosmolal saline was significantly delayed. The emptying of saline was also delayed by intravenous infusion of CCK-8 (400 pmol.kg-1.h-1). The CCK antagonist L364,718 reversed the effect of peptone in a dose-dependent manner and inhibited the response to exogenous CCK, but the emptying of physiological saline, 50 mM HCl, or hyperosmolal saline remained unchanged. A protease inhibitor (FOY-305) that is thought to release endogenous CCK by inhibiting negative feedback control by luminal proteases also delayed emptying, and this response was inhibited by L364,718. We conclude that CCK has a physiological role in the mediation of the effect of proteins on gastric emptying in the rat.
Biliary secretion of organic anions in the dog: association with defined lipid particles
Authors: Tazuma S. , Barnhart R. L. , Reeve L. E. , Tokumo H. , Holzbach R. T.
Published: December 2017

Organic anions have recently been found to partition in vitro into various biliary lipid particulate species according to their relative hydrophobicities. To establish the physiological relevance of these observations, we intravenously injected various radiolabeled organic anions and assessed the distributions of parent compounds and their metabolites to lipid particles in canine bile. Partitioning into various biliary lipid particles was determined by gel permeation chromatography. Relative hydrophobicities of the various organic anions and their radiolabeled conjugates were determined by reverse-phase high-pressure liquid chromatography. A strong positive correlation (P less than 0.001) was found between percent vesicular association and degree of hydrophobicity for a given organic anion and/or its more polar conjugate. We conclude that 1) the hydrophobic-hydrophilic balance of organic anions is a key factor governing their partitioning to lipid particles secreted in bile; 2) the present study agrees well with our previously published in vitro observations; and 3) other chemical constituents, e.g., proteins, mucin, etc., appear to have little or no effect on organic anion transport in bile.
Primary culture of secretagogue-responsive parietal cells from rabbit gastric mucosa
Authors: Chew C. S. , Ljungstrom M. , Smolka A. , Brown M. R.
Published: December 2017

A new procedure for isolation and primary culture of gastric parietal cells is described. Parietal cells from rabbit gastric mucosa are enriched to greater than 95% purity by combining a Nycodenz gradient separation with centrifugal elutriation. Cells are plated on the basement membrane matrix, Matrigel, and maintained in culture for at least 1 wk. Parietal cells cultured in this manner remain differentiated, cross-react with monoclonal H+-K+-ATPase antibodies, and respond to histamine, gastrin, and cholinergic stimulation with increased acid production as measured by accumulation of the weak base, [14C]aminopyrine. When stimulated, cultured cells undergo ultrastructural changes in which intracellular canaliculi expand and numerous microvilli are observed. These ultrastructural changes are similar to those previously found to occur in vivo and in acutely isolated parietal cells. Morphological transformations in living cells can also be observed with differential interference contrast optics in the light microscope. After histamine stimulation, intracellular canaliculi gradually expand to form large vacuolar spaces. When the H2 receptor antagonist, cimetidine, is added to histamine-stimulated cells, these vacuoles gradually disappear. The ability to maintain hormonally responsive parietal cells in primary culture should make it possible to study direct, long-term effects of a variety of agonists and antagonists on parietal cell secretory-related activity. These cultured cells should also prove to be useful for the study of calcium transients, ion fluxes, and intracellular pH as related to acid secretion in single cells, particularly since morphological transformations can be used to monitor "physiological" responses at the same time within the same cell.
Evidence for a chloride conductance in secretory membrane of parietal cells
Authors: Perez A. , Blissard D. , Sachs G. , Hersey S. J.
Published: December 2017

A fluorescence-quench method using acridine orange as the probe was employed to monitor acid formation in situ by detergent-permeabilized gastric glands. In KCl medium, the addition of ATP to the permeabilized glands resulted in a rapid decrease in fluorescence and addition of valinomycin resulted in a second phase of fluorescence quench. The fluorescence was restored by addition of the H+-K+-ATPase inhibitor, Sch 28080. An ATP-dependent fluorescence quench was observed also in K2SO4 or K+-isethionate medium; however, valinomycin was ineffective in the Cl-free media. The ATP-dependent quench could be reversed or prevented by the electrogenic protonophore, tetrachlorosalicylanilide (TCS), in KCl medium but not in Cl-free media. The results with TCS are interpreted as demonstrating a large Cl- conductance in the secretory membrane, whereas the results with valinomycin indicate that resting membranes lack a K+ conductance. The data suggest that a complex KCl pathway that may demonstrate a Cl- conductance is used to activate acid secretion.
Emergence of Na+-glucose cotransport in an epithelial secretory cell line sensitive to cholera toxin
Authors: Nath S. K. , Rautureau M. , Heyman M. , Reggio H. , L'Helgoualc'h A. , Desjeux J. F.
Published: December 2017

Epithelial properties and effects of cholera toxin (CT) and glucose were investigated in human rectal tumor cell line HRT-18. Addition of 10(-3) M dibutyryl adenosine 3',5'-cyclic monophosphate (DbcAMP), 10(-8) M vasoactive intestinal peptide, 10(-5) M epinephrine, and 10(-5) M forskolin to the serosal side and of 3.5 micrograms/ml CT to the mucosal side and of 2 micrograms/ml A23187 to both the serosal and mucosal sides raised short-circuit current (Isc). This rise was reversed by serosal addition of 5 x 10(-5) M bumetanide or 10(-4) M ouabain. In filters treated with CT, Isc and net chloride flux (JClnet) increased after 60 min from 0.05 +/- 0.008 and -0.04 in the Ringer to 0.32 +/- 0.05 and -0.33 mueq.h-1.cm-2, respectively. Addition of 10(-2) M glucose further raised Isc by stimulating net sodium flux (JNanet) (0.70 +/- 0.08 and + 0.58 mueq.h-1.cm-2, respectively). This additional augmentation of Isc was reversed by 0.5 mM phlorizin and was mimicked by 3-O-methyl-D-glucose. When the filters were stimulated by cAMP for 15 min, Isc was also enhanced by addition of glucose. In untreated filters, Isc, JNanet, and JClnet did not differ significantly before and after addition of glucose. It is concluded that HRT-18 cells in basal state do not display absorptive properties but secretory properties stimulated by CT. However they exhibit Na+-glucose cotransport once stimulated by either CT or cAMP.
Inhibition of gastric emptying by glucose depends on length of intestine exposed to nutrient
Authors: Lin H. C. , Doty J. E. , Reedy T. J. , Meyer J. H.
Published: December 2017

Nutrients inhibit gastric emptying in a dose-related fashion. We postulated that load-dependent gastric emptying results from the saturation of mucosal absorptive mechanisms, so that a longer length of the small intestine is exposed to unabsorbed nutrients as more nutrient enters the intestine to participate in this negative feedback. To test this idea, we limited exposure of 0.25 to 1.0 M glucose meals to various lengths of duodenum and jejunum in 17 dogs. The effects of these limited perfusions were then compared with experiments in which the whole gut (ALL) was exposed to the nutrient. Maximal inhibition was seen with 1.0 M meal and was similar with perfusions of 150 cm and ALL. By contrast, even with the 1.0 M load, no inhibition of gastric emptying was seen when glucose meal was confined to the first 15 cm of the proximal duodenum. Only 50-60% of maximal inhibition was observed during confinement of 1.0 M meal to the proximal 65 cm. We concluded that glucose sensors are present in both the proximal and the distal gut and the inhibition was related to the length of the small intestine exposed to glucose.
Quantitation of metabolites of isolated chicken enterocytes using NMR spectroscopy
Authors: Quirk P. G. , King G. F. , Campbell I. D. , Boyd C. A.
Published: December 2017

Isolated enterocytes prepared from chicken small intestine were studied by proton nuclear magnetic resonance (NMR). Perchloric acid extracts of cells were prepared from duodenum, jejunum, and ileum, and concentrations of 19 different metabolites were determined after the virtually complete assignment of all peaks in the aliphatic region of the spectrum. High concentrations of serine ethanolamine phosphodiester (SEP), creatine, taurine, and acidic amino acids were found in all segment extracts. Relatively high concentrations of SEP (approximately 12 mM) and acidic amino acids (approximately 3.5 mM) were found in the ileum, whereas creatine (3 mM) and lactate (6.5 mM) were found at higher concentrations in jejunum. Taurine (approximately 8 mM), choline (0.5 mM), and betaine (approximately 0.5 mM) were evenly distributed throughout the segments. Fasting (40 h) led to substantial increases in the concentrations of pyruvate, succinate, SEP, and taurine, while neutral hydrophobic amino acid concentrations fell appreciably. The significance of the findings is discussed, and the possible contributions of SEP, taurine, and choline to membrane lipid homeostasis are considered.
Inhibition of gastric and pancreatic secretion in dogs by CGRP: role of somatostatin
Authors: Helton W. S. , Mulholland M. M. , Bunnett N. W. , Debas H. T.
Published: December 2017

The coexistence of calcitonin gene-related peptide (CGRP) and somatostatin (SS) within the stomach and pancreas and the potent inhibitory effects of both peptides on exocrine secretions from these organs suggest that they are functionally related. To assess the potential role of SS in the mediation of CGRP action, the effects of intravenous human CGRP (64, 132, and 264 pmol.kg-1.h-1) and somatostatin-14 (SS-14; 100, 400, and 800 pmol.kg-1.h-1) on plasma levels of SS immunoreactivity (SS-IR) and on pentagastrin-stimulated gastric and pancreatic secretion were compared in conscious dogs. CGRP caused significant inhibition of gastric acid (85-102%), pancreatic protein (63-86%), and pancreatic bicarbonate (74-89%) outputs and a simultaneous dose-related rise (40-102 fmol/ml) in plasma SS-IR. Cessation of CGRP infusion resulted in prompt return of plasma SS-IR to basal levels and an increase in gastric and pancreatic secretion. Although CGRP is a potent releasor of SS into the circulation, its inhibitory action on gastric acid secretion cannot be explained solely by a rise in plasma SS-IR. In the pancreas, in contrast to the stomach, inhibition appears to be more closely related to a rise in circulating level of SS-IR.
Distribution and function of enteric GAL-IR nerves in dogs: comparison with VIP
Authors: Gonda T. , Daniel E. E. , McDonald T. J. , Fox J. E. , Brooks B. D. , Oki M.
Published: December 2017

The distribution of nerves containing galanin-immunoreactive (GAL-IR) material was compared to the distribution of neurons containing vasoactive intestinal polypeptide (VIP) immunoreactivity in the canine gastrointestinal tract. The actions of intra-arterially administered galanin and VIP on motility in the gastric antrum and corpus and the intestines were also studied. All sphincter muscles contained galanin- and VIP-immunoreactive nerve profiles. VIP-immunoreactive nerve profiles were present in all layers of the stomach, small intestine, and colon. GAL-IR nerve somata were common in the submucous plexus of ileum and colon and in the myenteric plexus of the terminal antrum, as were nerve processes in various layers. In the small intestine, galanin inhibited contractile responses to field stimulation of intrinsic nerves and also reduced the contractions after nerve blockade with tetrodotoxin (TTX). VIP often enhanced field-stimulated contractions at low doses but inhibited these and the contractions after TTX at higher doses. In the stomach and colon, both peptides inhibited responses to field stimulation; whether these effects were due to actions on smooth muscle was not tested. The distribution and actions of galanin in gut are consistent with the hypothesis that it acts at smooth muscle sites and possibly at prejunctional sites.
Inward-rectifying potassium channels in rat hepatocytes
Authors: Henderson R. M. , Graf J. , Boyer J. L.
Published: December 2017

The patch-clamp technique has been used to investigate single-channel and whole cell conductances in freshly isolated rat hepatocytes. Whole cell experiments, with high (144 mM) intracellular and extracellular potassium as the principal conductive species, show some variation between cells in the current-voltage relationship (mean whole-cell conductance at physiological potentials being 2.7 nS). This may suggest functional heterogeneity of cells. The most common finding is that the current-voltage relationship shows inward rectification. This is reflected in cell-attached single-channel recordings in which channels displaying strong inward rectification and K+ selectivity are seen. The channels show a mean inward conductance (with 144 mM potassium in the pipette) of 44 pS and an outward conductance of 23 pS. The open probability is not voltage dependent, and the channels do not exhibit calcium dependence. The channels are quite different from others described in hepatocytes, but they show marked similarities to channels recently described in renal epithelial cells. Current-voltage relationships in the whole cell mode exhibit an increase in slope conductance at large hyperpolarizing and depolarizing potentials.
Immunological localization of an 80-kDa phosphoprotein to the apical membrane of gastric parietal cells
Authors: Hanzel D. K. , Urushidani T. , Usinger W. R. , Smolka A. , Forte J. G.
Published: December 2017

Monoclonal antibodies were raised against an 80-kDa phosphoprotein (80K) that is phosphorylated upon stimulation of gastric acid secretion and that copurifies with the acid-forming H+-K+-ATPase isolated from stimulated tissue. These antibodies were used to demonstrate that in the gastric mucosa 80K is limited to parietal cells and not found in surface, mucous neck, or chief cells. 80K was also found in other transporting epithelia, including intestine and kidney, but was not found in brain, liver, red blood cells, or colon. Immunohistological localization of 80K in resting glands revealed a fine network, projecting from the gland lumen and anastomosing throughout the parietal cell. This network is quite similar to the staining pattern for F-actin contained in microvilli that line the apical membrane of parietal cells. Stimulation of acid secretion rearranges 80K to a more rugose pattern filling the entire cell. In stimulated cells the distribution pattern of 80K is indistinguishable from that stained with antibodies against the H+-K+-ATPase. These data strongly suggest that 80K is an apical membrane protein of the parietal cell.
Effect of adenine on liver nucleotide after fructose loading by 31P-NMR
Authors: Thoma W. J. , Ugurbil K.
Published: December 2017

Livers from 125- to 150-g rats were perfused and the effect of fructose metabolism on liver energetics was observed using 31P nuclear magnetic resonance (NMR). Livers were exposed to fructose in a nonrecirculating manner for approximately 15 min and monitored for recovery for 30 min. At concentrations ranging from 1 to 25 mM, fructose exposure led to depletion of the nucleoside triphosphate level. Subsequently, the nucleoside triphosphate level recovered fully at a fructose concentration of 1 mM; however, recovery was only 65% of the initial values if the fructose concentration was 10 mM and 55% if the concentration was 25 mM. Adenine was found to protect nucleoside triphosphate levels against the adverse effects of fructose by blocking the deamination of AMP. In the presence of adenine, AMP accumulation was observed in the NMR spectra upon exposure of the liver to fructose.
Postprandial gastric blood flow in conscious dogs
Authors: Kato M. , Naruse S. , Takagi T. , Shionoya S.
Published: December 2017

Left gastric arterial blood flow was measured with an electromagnetic flowmeter in conscious dogs. Immediately after the ingestion of 300 g of meat or milk, gastric blood flow increased to 250-270% of the control but declined to preprandial levels in 10 min despite the presence of milk in the stomach. Gastric distension with a 300-ml balloon evoked a response of approximately 50% of that of milk, but continuous distension failed to maintain gastric hyperemia. The initial peak response to milk and distension was reduced by hexamethonium (-58 and -62%, respectively) and oxethazaine (-43 and -29%, respectively) but not by phenoxybenzamine, propranolol, or atropine. Thus the initial response was induced by both the contact of food with the mucosa and the distension of the stomach partly via the activation of neural reflexes. Gastric blood flow after the peak was dependent on the type of food and its route of administration; it was elevated by 30% after a meat meal, remained close to fasting levels after oral administration of milk, and fell below fasting levels (-17%) after intragastric administration of milk. An intraduodenal infusion of milk, but not water, reduced gastric blood flow below the control (-26%). Pentagastrin, which caused approximately 50% of the maximal acid secretion, increased gastric blood flow by only 10%.
Differences in jejunal and ileal response to E. coli enterotoxin: possible mechanisms
Authors: Cohen M. B. , Thompson M. R. , Giannella R. A.
Published: December 2017

Escherichia coli, which produce heat-stable enterotoxin (STa), cause intestinal fluid secretion as a mechanism of diarrhea. To determine the factors that modulate the intestinal secretory response, we first compared the time course of the STa-induced secretion in ligated in situ loops of rat jejunum and ileum. We found that the jejunal secretory response was brief (less than or equal to 30 min) while the ileal response to STa was sustained (greater than or equal to 3 h). We then compared the modification of purified STa that occurred in jejunum and ileum and found a close correlation between the continued presence of unmodified, authentic STa and continued fluid secretion in the ligated-loop model. At both sites alteration of STa was demonstrated by high-performance liquid chromatography profile and brush-border membrane binding activity. However, in the jejunum, the modification of STa was qualitatively different and quantitatively much greater. We conclude that the degree to which STa is inactivated or removed from the intestine correlates with the secretory response observed. Inactivation of STa may be a mechanism by which the host limits its secretory response.
Inhibition of antral gastrin cells by peptide histidine isoleucine
Authors: Wolfe M. M. , Mailliard M. E. , Dunn B. M. , Green E. P. , Karnik P. S.
Published: December 2017

The present studies were directed to determine whether peptide histidine isoleucine (PHI), like its structural analogues secretin and gastric inhibitory peptide, inhibits antral gastrin. In separate experiments, the effects of PHI on medium gastrin concentrations, the incorporation of [35S]methionine into newly synthesized gastrin, and steady-state gastrin mRNA were determined. The inclusion of PHI in the incubation medium decreased medium gastrin levels at all concentrations examined, an effect that was not altered by the addition of 10(-6) M tetrodotoxin to the medium. PHI also inhibited the incorporation of [35S]methionine into newly synthesized gastrin in a concentration-dependent manner. Steady-state levels of gastrin mRNA were determined by dot-blot hybridization, using a 32P-labeled gastrin cRNA probe. PHI inhibited gastrin mRNA levels in a concentration-dependent manner; in contrast, no effect on the levels of actin and ubiquitin mRNA could be detected, indicating specificity of PHI on gastrin mRNA. The results of these studies indicate that PHI may exert a physiological inhibitory effect on antral gastrin cells and that this inhibition may occur at several steps along the biosynthetic pathway.
Spatial and temporal patterns of human jejunal contractions
Authors: Sarna S. K. , Soergel K. H. , Harig J. M. , Loo F. D. , Wood C. M. , Donahue K. M. , Ryan R. P. , Arndorfer R. C.
Published: December 2017

We recorded human jejunal motor activity by a 12-lumen manometric tube with recording sites 2 cm apart. The contractile activity in the fasted and the fed state was analyzed by computer to define the spatial and temporal patterns of contractions. Mean duration and area of single contractions during phase III activity were not different from those during phase II activity. By contrast, the frequency and amplitude of contractions, their propagation distance, and the percentage of contractions that propagated for greater than or equal to 2 cm were significantly greater during phase III than during phase II activity. The mean frequency and percentage of propagated contractions in the fed state were intermediate between those during phase II and phase III activity. Mean propagation distance of postprandial contractions was not different from that of phase II contractions. Most contractions in the fed state were uncoordinated at adjacent recording sites. Occasionally, large-amplitude and long-duration contractions, called individual migrating contractions, propagated over long distances and frequently over the entire 22-cm study segment. We conclude that there are some significant differences between the spatial and temporal patterns of contractions between the fed state and phase II and phase III activity. The largely disorganized phasic contractions in the fed state may cause mostly mixing of the ingested meal and its slow distal propagation, whereas the infrequent individual migrating contractions may rapidly propel intestinal contents over longer distances.