bluuebunny/crossref_metadata_2025 huggingface dataset:
Secretagogue-induced protein phosphorylation and chloride transport in Caco-2 cells
Authors: Burnham D. B. , Fondacaro J. D.
Published: December 2017

The effects of vasoactive intestinal polypeptide (VIP), 16,16-dimethyl prostaglandin E2 (DMPGE2) and dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) on protein phosphorylation were studied in relation to stimulation of chloride transport in cell suspensions of the human colon epithelial cell line Caco-2. In 36Cl-loaded cells, VIP and DMPGE2 within 1 min decreased cellular chloride content 35-40%, with half-maximal effects being elicited at 1.0 and 85 nM concentration, respectively. A similar effect on chloride content occurred after 10 min of treatment with 0.5 mM DBcAMP. For all three secretagogues, decreases in cellular chloride content were associated with increases in membrane permeability to chloride. DMPGE2 and VIP within 1 min, and DBcAMP within 10 min, increased the phosphorylation of an unidentified soluble protein of Mr = 42,000 and pI = 6.1, and of a protein of Mr = 20,200 and pI = 4.9 identified as myosin regulatory light chain. Between 10 and 30 min of stimulation, however, phosphorylation of the Mr = 42,000 protein and chloride transport activity remained elevated in DMPGE2- and DBcAMP-treated cells, whereas light chain phosphorylation returned to control level. No effect of secretagogues on phosphorylation was detected in the total particulate fraction or an integral membrane protein fraction. It is concluded that increased membrane permeability to chloride induced by cAMP-mediated secretagogues in Caco-2 is temporally associated with the increased phosphorylation of a Mr = 42,000 soluble protein.
Cholecystokinin-induced desensitization of pepsinogen secretion from chief cells
Authors: Cherner J. A. , Naik L. , Singh G.
Published: December 2017

When dispersed chief cells from guinea pig stomach were first incubated with cholecystokinin (CCK), washed, and then reincubated with CCK in fresh incubation solution, the stimulation of pepsinogen secretion and the rise in intracellular calcium concentration during the second incubation were reduced. CCK did not cause residual enzyme secretion but caused desensitization that was rapid, temperature dependent, dependent on extracellular calcium, reversible with time, and prevented but not reversed by CCK receptor antagonists. Cholecystokinin octapeptide (CCK-8) caused desensitization over the same range of concentrations that stimulate pepsinogen secretion, whereas the concentration of gastrin required to cause maximal desensitization was greater than that required to cause maximal stimulation of enzyme secretion. CCK-8 caused heterologous desensitization of pepsinogen secretion stimulated by agonists that interact with receptors to cause mobilization of cellular calcium and activation of protein kinase C or by agonists that bypass receptors to activate these mediators directly; however, CCK-8 did not induce desensitization of the stimulation caused by any secretagogue whose actions are mediated by adenosine 3',5'-cyclic monophosphate. Because CCK-8 caused greater desensitization of secretion stimulated by agonists that interact with receptors than by agonists that bypass receptors, it is likely that receptor modulation as well as a postreceptor action contribute to the ability of CCK to cause desensitization of pepsinogen secretion from chief cells.
Effect of chronic metabolic acidosis on net electrolyte transport in rat colon
Authors: Feldman G. M.
Published: December 2017

Rats fed NH4Cl (5 meq.100 g body wt-1.day-1) for one week developed chronic metabolic acidosis and had an arterial blood pH and plasma HCO3- concentration of 7.27 +2- 0.02 and 16.2 +/- 0.8 meq/l, respectively; control animals had values of 7.36 +/- 0.01 and 22.4 +/- 0.5 meq/l, respectively. Net electrolyte transport was measured in proximal and distal colonic segments by in situ perfusion. In proximal colon, chronic metabolic acidosis increased HCO3- absorption from 3.3 +/- 0.8 to 6.4 +/- 0.6 mu eq.min-1.g-1 but did not alter Na+ absorption. In distal colon, although Na+ transport was unaffected, chronic acidosis reduced HCO3- secretion from -6.9 +/- 0.8 to -4.4 +/- 0.7 mu eq.min-1.g-1 and increased voltage from -18.9 +/- 2.0 to -51.1 +/- 4.2 mV. To evaluate the dependence of these effects on altered arterial pH and HCO3- concentration, NaHCO3 was infused intravenously, raising pH and HCO3- concentration to 7.53 +/- 0.04 and 23.9 +/- 1.7 meq/l, respectively. Although acute correction of chronic metabolic acidosis reduced HCO3- absorption in proximal colon, it did not affect HCO3- secretion or voltage in the distal segment, suggesting that proximal and distal colon respond differently to chronic metabolic acidosis. These results also suggest that chronic metabolic acidosis alters the mechanisms of ion transport in distal colon.
Bombesin and nutrients stimulate release of CCK through distinct pathways in the rat
Authors: Cuber J. C. , Vilas F. , Charles N. , Bernard C. , Chayvialle J. A.
Published: December 2017

An isolated, vascularly perfused duodenojejunum model was developed in the rat to investigate the mechanisms involved in the release of cholecystokinin (CCK) by vascular bombesin (BBS) and luminal nutrients (LN). Immunoreactive peptides released into the portal vein effluent were measured with three antisera that were relatively CCK specific, gastrin specific, and cross-reactive to both CCK and gastrin, respectively. Bombesin (10(-7) M) provoked a biphasic release of CCK, consisting of a transient rise (approximately 700% above basal) followed by a sustained response (approximately 250% above basal). Gastrin accounted for less than 25% of the total immunoreactivity as measured with the nonspecific antiserum. The two phases of the CCK response were related to the dose of BBS in the range 10(-10)-10(-6) M, with a half-maximal effect at 10(-8) M BBS. Tetrodotoxin (TTX, 10(-6) M) reduced the second phase only (by 80%), whereas hexamethonium (10(-4) M) and atropine (10(-5) M) left the two phases unaltered. LN induced a prompt and well-sustained release of CCK (approximately 250% above basal) that was not affected by arterial TTX or atropine. These results demonstrate that BBS stimulated the release of CCK through both a direct pathway and an indirect, noncholinergic mechanism, while the effect of LN did not appear to involve intramural nerves.
Neural mechanisms of pancreatic polypeptide release in conscious dogs
Authors: Hosotani R. , Chowdhury P. , Huang Y. S. , Rayford P. L.
Published: December 2017

L364,718, a potent and specific antagonist for peripheral cholecystokinin (CCK) receptors, was used to determine its effect on plasma levels of pancreatic polypeptide (PP) after administration of 2-deoxy-D-glucose (2-DG, a central vagal activator) and of bethanechol (a cholinergic receptor agonist). Six conscious dogs were used in this study. Intravenous injection of 2-DG (75 mg/kg) caused significant increases in plasma levels of PP and gastrin, but there was no significant rise in plasma levels of immunoreactive and bioactive CCK. Intravenous injection of L364,718 (20 nmol/kg) significantly inhibited the PP response stimulated by 2-DG injection by approximately 60% but did not affect gastrin. Plasma levels of PP were increased dose dependently by bethanechol infusion and were not altered significantly by injections of L364,718. The results indicate that L364,718 inhibits PP response stimulated by a central vagal activator (2-DG) but not by cholinergic receptor agonist (bethanechol). This study suggests that CCK might be involved in the neural control of PP release as a neurotransmitter but probably not as a final activator of PP cells in dogs.
Benzodiazepine analogues L365,260 and L364,718 as gastrin and pancreatic CCK receptor antagonists
Authors: Huang S. C. , Zhang L. , Chiang H. C. , Wank S. A. , Maton P. N. , Gardner J. D. , Jensen R. T.
Published: December 2017

We examined the ability of the recently described 3-(benzoylamino)benzodiazepine analogue L365,260 and the 3-(acylamino)benzodiazepine analogue L364,718 to distinguish gastrin from pancreatic cholecystokinin (CCK) receptors. Neither L365,260 nor L364,718 when present alone (1 microM) caused stimulation of amylase release from guinea pig pancreatic acini or caused contraction of smooth muscle cells from guinea pig stomach. Each analogue inhibited CCK-stimulated amylase release, gastrin-17-I-stimulated smooth muscle contraction, binding of 125I-Bolton-Hunter-cholecystokinin octapeptide (125I-BH-CCK-8) to pancreatic CCK receptors, and binding of 125I-gastrin-17-I to gastrin receptors on pancreatic acini. L365,260, (Ki, 7.3 +/- 0.8 nM) was 50-70 times more potent than L364,718 at inhibiting binding of 125I-gastrin to pancreatic acini or gastrin-stimulated smooth muscle contraction. In contrast, L364,718 (Ki, 4 +/- 1 nM) was 145-200 times more potent than L365,260 at inhibiting binding of 125I-BH-CCK-8 to pancreatic acini or CCK-stimulated amylase release. Neither L364,718 nor L365,260 distinguished between high- and low-affinity CCK binding sites. L365,260 and L364,718 did not inhibit binding of radiolabeled vasoactive intestinal peptide, secretin, bombesin, substance P, or N-methylscopolamine to pancreatic acini. These results demonstrate that, in contrast to other gastrin-CCK receptor antagonists described, L365,260 is a selective gastrin receptor antagonist having an 80-fold higher affinity for gastrin than pancreatic CCK receptor, whereas L364,718 has a 125-fold higher affinity for pancreatic CCK receptors. Because of the selectivity of these two antagonists the involvement of CCK and gastrin in various physiological processes can be differentiated even when both receptors occur on the same cell.
Neural isolation of the entire canine stomach in vivo: effects on motility
Authors: Van Lier Ribbink J. A. , Sarr M. G. , Tanaka M.
Published: December 2017

This study was designed to determine the effects of transection of all extrinsic and enteric neural continuity to the entire stomach on motility patterns of the stomach and small intestine. Five dogs were subjected to a model of orthotopic autotransplantation of the stomach to achieve an in vivo, "neurally isolated" stomach. Manometric catheters and serosal electrodes were implanted. A cyclic motor pattern occurred during fasting and was closely coordinated temporally with the migrating motor complex (MMC) in the small bowel. The period of the cyclic gastric motor activity did not differ from the period of the MMC in the small intestine [121 +/- 8 vs 124 +/- 10 (means +/- SE) min, P = 0.4], but the periods of both were greater than in control dogs (93 +/- 5 min, P less than 0.05). Tachygastria accounted for 36 +/- 13% of fasting myoelectric activity in the neurally isolated dogs and for less than 1% in control dogs. Plasma concentration of motilin was greatest during the phase III-like gastric motor activity; exogenous motilin induced premature phase III-like activity in the stomach and small intestine. Feeding abolished the cyclic motor activity in the stomach and decreased plasma motilin concentration. These data suggest that hormonal factors, and not extrinsic or intrinsic neural continuity to the stomach, may control both the initiation of a cyclic interdigestive gastric motor pattern and its temporal coordination with motor patterns in the small intestine.
Characteristics of glutamine transport in dog jejunal brush-border membrane vesicles
Authors: Bulus N. M. , Abumrad N. N. , Ghishan F. K.
Published: December 2017

The present study characterizes glutamine transport across brush-border membrane vesicles (BBMV) prepared from dog jejunum. The purity of these vesicles was demonstrated by a 20-fold enrichment of leucine aminopeptidase, a marker for BBM. Glutamine uptake was found to occur into an osmotically active space with no membrane binding and to exhibit temperature and pH dependence (optimal uptake at pH 7-7.5). Glutamine uptake was driven by an inwardly directed Na+ gradient with a distinct overshoot not observed under K+ gradient. Lithium could not substitute for Na+ as a stimulator of glutamine uptake. Na+-dependent glutamine uptake was not inhibited by methylaminoisobutyric acid, a typical substrate for system A, and was found to be electrogenic and saturable with a Km of 0.97 +/- 0.58 mM and a Vmax of 3.93 +/- 0.99 nmol.mg protein-1.10 s-1. A Na+-glutamine coupling ratio of 1:1 could be demonstrated by a plot of Hill transformation. Na+-independent glutamine uptake was found to be electroneutral and saturable with a Km of 3.70 +/- 0.66 mM and a Vmax of 2.70 +/- 1.55 nmol.mg protein-1.10 s-1. Inhibition studies confirmed the presence of a Na+-dependent as well as a Na+-independent carrier for glutamine uptake. We conclude that glutamine uptake across dog BBMV occurs via two transport systems: a Na+-dependent high-affinity system similar to the neutral brush-border system and a Na+-independent lower-affinity system similar to system L.
Two calcium channels in basolateral membranes of rabbit ileal epithelial cells
Authors: Homaidan F. R. , Donowitz M. , Weiland G. A. , Sharp G. W.
Published: December 2017

The actions of three different types of calcium channel blockers on short-circuit current (Isc) in rabbit ileum were studied. These included the phenylalkylamines, verapamil and (l)-desmethoxyverapamil (D888); the dihydropyridines, nifedipine and nitrendipine; and the benzothiazepine, diltiazem. All of the drugs decreased Isc, a change associated with increased Na and Cl absorption. Verapamil and D888 had the largest effects. The dihydropyridine, BAY K 8644, a calcium channel activator, increased Isc and decreased Na and Cl absorption, effects not inhibited by tetrodotoxin. The phenylalkylamines had an additional effect on Isc in the presence of a maximally inhibitory concentration of the dihydropyridines, suggesting the possibility of two distinct calcium channels, one of which is the L-type voltage-activated, dihydropyridine- and phenylalkylamine-sensitive channel, and the other is a channel only sensitive to phenylalkylamines but not to dihydropyridines. [3H]nitrendipine and [3H]D888 binding to an enriched preparation of basolateral membranes from ileal epithelial cells was characterized. Each ligand bound specifically and saturably to an apparently single population of high-affinity sites with [3H]D888 having three times as many binding sites as [3H]nitrendipine. [3H]nitrendipine binding was partially inhibited by verapamil and D888 and was increased by diltiazem; whereas [3H]D888 binding was inhibited completely by verapamil but only partially by nitrendipine and diltiazem. These transport and binding studies suggest the presence of two types of Ca2+ channels in ileal epithelial cells, one of which interacts with the dihydropyridines, the phenylalkylamines, and the benzothiazepines at three different sites and the other channel that only binds the phenylalkylamines.
Induction of neurally mediated NaHCO3 secretion by luminal distension in rat ileum
Authors: Harris M. S. , Ramaswamy K. , Kennedy J. G.
Published: December 2017

Distension induces secretion in the intact intestine, but the mechanism of this secretory process remains unresolved. We sought to characterize the effect of intraluminal pressures below 20 cmH2O on water and electrolyte movements in the rat ileum and the subsequent effects of two cholinergic antagonists, hexamethonium and atropine. An increase in intraluminal pressure from 3.0 to 12.5 cmH2O led to inhibition of net H2O and Na absorption and stimulation of HCO3 secretion. However, there was no significant change in Cl absorption. Secretion occurred in the absence of changes in tissue wet weight, intercellular fluid accumulation, villus tip erosions, or mannitol flux. Alterations in fluid and electrolyte absorption were prevented by the intra-arterial administration of hexamethonium (10 mg/kg). Atropine (0.5 mg/kg) had no effect. Our studies demonstrate that distension induces the secretion of Na and HCO3 by the intact ileum. This secretory process may represent a neurally rather than passively mediated mechanism.
Relation between fasting antroduodenal motility and transpyloric fluid movements
Authors: Schindlbeck N. E. , Heinrich C. , Muller-Lissner S. A.
Published: December 2017

The effect of fasting antroduodenal motility on duodenogastric fluid movements was studied in 12 healthy volunteers. Antroduodenal motility was recorded using a multilumen manometry tube. Gastric emptying and secretion and the duodenogastric reflux of bile acids and marker were measured simultaneously by means of a marker dilution technique. Gastric emptying and acid secretion were higher in phase II than in phase I of the fasting motor activity cycle [median (range) 1.74 (1.2-4.2) ml/min vs. 0.90 (0.0-2.4) ml/min and 63.5 (6.4-115.0) vs. 37.9 (5.8-86.4) mumol/min, P less than 0.01]. The duodenogastric reflux rates of bile acids and marker were similar in all phases and showed large intra- and interindividual variations. There was no correlation between antroduodenal coordination during phase II motility and gastric emptying and duodenogastric reflux. It is concluded that the interdigestive motility pattern has moderate effects on fasting emptying of liquid gastric contents and on gastric secretion but no effects on duodenogastric reflux.
Processing of cholecystokinin by isolated liver cells
Authors: Gores G. J. , Kost L. J. , Miller L. J. , LaRusso N. F.
Published: December 2017

Although hepatic uptake of cholecystokinin (CCK) has been demonstrated, the liver cell involved and the mechanism of uptake remain unclear. We have used dispersed rat hepatocytes, Kupffer cells, and hepatic endothelial cells to characterize uptake and metabolism of radiolabeled CCK peptides. Only rat hepatocytes showed significant uptake of 125I-labeled cholecystokinin octapeptide (125I-CCK-8). Peptide specificity of uptake by hepatocytes was similar to that seen in the isolated perfused rat liver, with extraction of 125I-CCK-8 being sevenfold greater than that of 125I-CCK-33. Uptake was saturable, as 10(-4) M CCK-4 inhibited uptake of 125I-CCK-8 by 85%. Uptake was rapid, temperature dependent, and extensive and was decreased by metabolic inhibition, a proteolytic enzyme (trypsin), organic anions (sulfobromophthalein and taurocholic acid), and an inhibitor of anion transport 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. In addition, uptake was dependent on extracellular anions but not on extracellular sodium, calcium, or magnesium. After uptake, hepatocytes released radiolabel in a time- and temperature-dependent manner, predominantly in metabolized forms. Thus the hepatocyte is the liver cell that extracts CCK by an active, anion-dependent process. The characteristics of the uptake process resemble those described for organic anions and small, cyclic peptides and suggest that small, linear peptides may undergo hepatocyte extraction by a similar mechanism.
Induction of gastric and duodenal mucosal ornithine decarboxylase during stress
Authors: Wang J. Y. , Johnson L. R.
Published: December 2017

The purpose of this study was to determine whether gastric and duodenal mucosal ornithine decarboxylase (ODC) activity increased during a period of ulcer-producing stress and whether changes in enzyme activity altered the severity of damage. Rats were fasted for 22 h, placed in a restraint cage, and immersed in water to the xiphoid process for different times lasting from 2 to 8 h. After 6 h, stress slightly increased gastric mucosal ODC and caused a sevenfold increase in duodenal mucosal ODC activity. Macroscopic ulcers developed in the oxyntic gland mucosa but not duodenal mucosa. Interestingly, however, after 6 h microscopic inspection showed an absence of most villi from the duodenum. DNA, RNA, and protein content of both tissues decreased over the time rats were exposed to stress. DL-alpha-Difluoromethylornithine (DFMO, a specific ODC inhibitor) prevented the increase in ODC in both tissues and increased the loss of DNA and RNA from duodenal mucosa. The degree of damage was not altered by DFMO in either tissue in response to 6 h of stress. These results show that 1) stress causes microscopic damage to the duodenum, 2) stress increases ODC in both gastric and duodenal mucosa, and 3) the inhibition of ODC during 6 h of stress does not alter the severity of damage.
Ursodeoxycholate-induced changes in hepatic Na+-H+ exchange and biliary HCO3- excretion
Authors: Anwer M. S. , Hondalus M. K. , Atkinson J. M.
Published: December 2017

Ursodeoxycholate (UDC)-induced HCO3- -rich choleresis may be due to activation of sinusoidal Na+-H+ exchange followed by an increase in intracellular pH (pHi) and HCO3- excretion via canalicular Cl- -HCO3- exchange. To test this hypothesis, we studied the effect of UDC and tauroursodeoxycholate (TUDC) on net H+ efflux from perfused rat livers and pHi in isolated hepatocytes in the presence and absence of amiloride. UDC-induced increases in biliary HCO3- concentration and excretion were inhibited by amiloride. However, these increases were temporally associated with an initial decline in H+ efflux and pHi followed by a gradual recovery toward base line. The initial decline in H+ efflux was associated with a rapid uptake of UDC. Amiloride inhibited only the recovery phases of H+ efflux and pHi. TUDC increased amiloride-sensitive H+ efflux without affecting biliary [HCO3-] and decreased pHi in the presence but not in the absence of amiloride. Amiloride decreased TUDC-induced choleresis and HCO3- excretion most likely by decreasing TUDC excretion. TUDC decreased biliary [Cl-] and increased hepatic O2 uptake more than UDC. We conclude that a rapid influx of UDC in the protonated form decreases pHi and net H+ efflux initially. The recovery phase is due to Na+-H+ exchange activated by decreased pHi and possibly by UDC and increased cellular respiration. TUDC indirectly stimulates Na+-H+ exchange most likely by increasing cellular respiration. UDC-induced HCO3- -rich choleresis, which is observed at a time when both net H+ efflux and pHi are less than control values, is unlikely to be due to a direct activation of Na+-H+ exchange.
Effects of the CCK receptor antagonist L364,718 on pancreatic growth in adult and developing animals
Authors: Zucker K. A. , Adrian T. E. , Bilchik A. J. , Modlin I. M.
Published: December 2017

Although exogenous administration of cholecystokinin (CCK) or dietary manipulation to increase circulating CCK have previously been shown to promote pancreatic growth, the role of CCK in controlling normal pancreatic development remains unclear. A potent CCK receptor antagonist, L364,718, was administered to rats, guinea pigs, and hamsters to block the effect of endogenous CCK. Animals were given continuous infusions of L364,718 (25 nmol.kg-1.h-1), CCK octapeptide [(CCK-8) 200 pmol.kg-1.h-1], or both CCK-8 and L364,718 for 14 and 28 days. Adult (4-mo-old) and young (4-wk-old) animals were used. CCK-8 and L364,718 were administered via separate, subcutaneously implanted mini-osmotic pumps. Infusions of CCK-8 alone for 28 days resulted in a 21.7% increase in wet pancreatic weight in 4-wk-old rats and a 22.7% increase in 4-wk-old guinea pigs (both P less than 0.001 compared with controls). Similar increases were found in DNA, RNA, and total protein contents. Coadministration of L364,718 totally blocked the trophic effects of exogenously infused CCK-8 in rats and guinea pigs. Administration of L364,718 alone in hamsters, guinea pigs, and rats for 14 and 28 days failed to alter the normal growth of the pancreas gland as measured by these parameters. Although elevated levels of CCK appear to promote a potent trophic response in the growing pancreas, this regulatory peptide does not appear to be an essential trophic factor for the normal growth of the exocrine pancreas in these animals.
Effects of hydrochloric acid on duodenal and jejunal mucosal permeability in the rat
Authors: Nylander O. , Kvietys P. , Granger D. N.
Published: December 2017

The effects of various concentrations of hydrochloric acid (1, 5, 10, and 100 mM) on mucosal permeability and acid disappearance (H+-dis) in duodenum and jejunum were studied in anesthetized rats. Mucosal permeability was assessed by measuring blood-to-lumen clearance of 51Cr-labeled EDTA (ED-Cl). Luminal alkalinization (LA) and H+-dis were determined by backtitration. ED-Cl was stable during saline perfusion and was not affected by changes in intestinal blood flow. Basal ED-Cl was four times higher in duodenum than in jejunum. Mucosal permeability of both duodenum and jejunum was not altered by 1 mM HCl. However, 5 mM HCl induced a 3.3-fold increase (P less than 0.001) in ED-Cl in jejunum but was without effect in duodenum. A 15-fold increase in ED-Cl was obtained in jejunum and a doubling (P less than 0.001) in ED-Cl was observed in duodenum when HCl concentration was increased to 10 mM HCl. One hundred millimolar HCl induced large increases of ED-Cl in both segments. The twofold increase of ED-Cl in response to 10 mM HCl in duodenum was completely reversible, whereas ED-Cl in jejunum was three to four times higher (P less than 0.05) than preacid levels 60 min after cessation of acid perfusion. The net increase in jejunal ED-Cl obtained after acid exposure was closely correlated (r = 0.99) with the net increase in LA, indicating leakage of interstitial fluid into the luminal solution. LA (saline perfusion) and H+-dis (HCl perfusion) were significantly higher in duodenum than in jejunum.(ABSTRACT TRUNCATED AT 250 WORDS)
Computerized curve fitting in the analysis of hydrogen gas clearance curves
Authors: Livingston E. H. , Reedy T. , Leung F. W. , Guth P. H.
Published: December 2017

Hydrogen gas clearance curves obtained from the rat gastric corpus were digitized into a computer and then analyzed by three methods: 1) linear regression of log-transformed data, 2) direct curve fitting with a modified Gauss-Newton nonlinear regression algorithm, and 3) Zierler's height-over-area algorithm. For linear regression of log-transformed data, if the initial base-line estimate was inaccurate or normal amounts of experimental noise were present, the log-transformed data was skewed, leading to deviation of the regression line and incorrect estimation of blood flow. By utilization of the direct-fit routine, the initial estimate of the parameters or experimental noise had little influence on the blood flow determination because of iterative improvement of the parameters. In a study of isoproterenol-stimulated gastric blood flow, Zierler's algorithm underestimated the blood flow estimate. We conclude that analysis of hydrogen gas clearance curves by linear regression of log-transformed data or by Zierler's algorithm may potentially introduce errors in blood flow estimates that may be avoided by analysis with a direct-fitting, nonlinear regression algorithm.
Deoxycholate-stimulated release of peptide YY from the isolated perfused rabbit left colon
Authors: Ballantyne G. H. , Longo W. E. , Savoca P. E. , Adrian T. E. , Vukasin A. P. , Bilchik A. J. , Sussman J. , Modlin I. M.
Published: December 2017

The purpose of this study was 1) to measure the effect of graded concentrations of oleic acid and deoxycholic acid (DCA) on the release of peptide YY (PYY) and enteroglucagon and 2) to test whether DCA-stimulated release of PYY was neurally mediated by blocking neuronal conduction with tetrodotoxin. Studies were performed in isolated left colons from New Zealand White rabbits. Oleic acid in concentrations from 0.22 to 22 mM suspended in 10 mM DCA significantly stimulated release of PYY (P less than 0.01) but resulted in no graded response (Bartlett's test, P = 0.15). Similarly, oleic acid (2.2 mM) suspended with ursodeoxycholic acid (10 mM) produced no increased release of PYY above that achieved by ursodeoxycholic acid alone. In contrast, oleic acid (2.2 and 22 mM suspended with 10 mM DCA) produced a graded release of enteroglucagon during the stimulated period. Deoxycholic acid caused a concentration-dependent release of PYY (1, 3.3, 10, and 25 mM) during the stimulated period. Deoxycholic acid (1 and 10 mM) did not significantly increase enteroglucagon release. Tetrodotoxin blockade had no effect on release of PYY stimulated by 10 mM DCA. Because PYY and enteroglucagon are both found in colonic endocrine cells, these results suggest that the release of PYY and enteroglucagon are mediated by specific secretagogues and not simply caused by noxious effects of the agonists. Also, this study has demonstrated that DCA-stimulated release of PYY is not dependent on neuronally mediated mechanisms.
Opening mechanisms of the human upper esophageal sphincter
Authors: Cook I. J. , Dodds W. J. , Dantas R. O. , Massey B. , Kern M. K. , Lang I. M. , Brasseur J. G. , Hogan W. J.
Published: December 2017

Our goals in this study were to evaluate the mechanisms operative in swallow-associated opening of the upper esophageal sphincter (UES) and to determine the dynamics of fluid flow across the sphincter. For this purpose, we obtained concurrent videofluorographic and manometric studies of 2- to 30-ml barium swallows in 15 normal subjects. We found that the resting UES high-pressure zone corresponded closely with the location of the cricopharyngeus. The findings indicated that manometric UES relaxation and anterior hyoid traction on the larynx invariably preceded UES opening. With graded increases in bolus volume, progressive increases occurred in UES diameter, cross-sectional area, flow duration, and transsphincteric flow rate. Intrabolus pressure upstream to the UES and within the UES at its opening during transsphincteric flow of barium remained within a narrow physiological range of less than 10 mmHg up to a bolus volume of 10 ml. With increases in bolus volume, anterior hyoid movement, UES relaxation, and UES opening occurred sooner in the swallow sequence to accommodate the early entry of large boluses into the pharynx. We conclude that during swallowing 1) normal UES opening involves sphincter relaxation, anterior laryngeal traction, and intrabolus pressure, 2) volume-dependent adaptive changes in UES dimension accommodate large bolus volumes and flow rates with minimal requirement for increases in upstream, or intrasphincteric, intrabolus pressure or UES opening duration, and 3) volume-dependent changes in UES dimensions as well as timing of UES relaxation and opening indicate a sensory feedback mechanism that modulates some components of the swallow response generated by the brain stem swallow centers.
Pressor responses in conscious rats with chronic portal venous hypertension
Authors: Battarbee H. D. , Farrar G. E. , Spears R. P.
Published: December 2017

Heart rate, mean arterial pressure (MAP), and vascular conductance responses to graded phenylephrine (PE) infusions were compared in conscious, unrestrained portal vein-stenosed (PS), and sham-operated (SO) rats chronically instrumented for pulsed Doppler flowmetry. Ten days after stenosis, MAP was lower in PS than in SO, and PS heart rates were higher. Pressor sensitivity to PE was attenuated 70%, and bradycardic responses to increases in MAP were 47% greater in PS. Abdominal aorta vascular bed conductance sensitivity was reduced 84%, and renal artery sensitivity was reduced 29% in PS compared with SO, whereas the superior mesenteric artery conductance response was unaffected by portal vein stenosis. After ganglionic blockade, the heart rate of PS remained greater than that of SO, and comparisons of renal artery, abdominal aorta, and superior mesenteric artery vascular conductances revealed no significant differences in neurogenic vascular tone. Differences between PS and SO pressor responses were abolished by ganglionic blockade, as were differences in vascular bed conductance responses. These findings suggest that a greater bradycardic response and greater baroreflex-mediated withdrawal of sympathetic tone from skeletal muscle and renal vascular beds were responsible for the decreased pressor sensitivity observed in PS animals.
Effect of epidermal growth factor on the ontogenic response of rat gastric mucosa to H+
Authors: Tepperman B. L. , Soper B. D.
Published: December 2017

Epidermal growth factor (EGF) plays an important role in the development of the neonatal intestinal tract and affects the integrity of adult stomach. This study examined the effects of EGF on the development of mucosal responses to luminal H+ in rats of various ages. Mucosal response to luminal acid (300 mN) was measured in rats between 10 and 60 days after birth. Permeability changes were expressed as H+ loss and Na+, K+, and protein appearance in the luminal instillate. Losses of H+ and luminal appearances of Na+, K+, and protein were greater in animals older than 20 days of age compared with younger rats. Mucosal permeability responses to 300 mN HCl were reduced by enteral or parenteral treatment with EGF (5-50 or 10-100 micrograms/kg sc) in rats 20 days of age and older. EGF did not consistently affect ion and protein fluxes in 10- and 15-day-old rats treated with HCl. Likewise EGF did not stimulate gastric HCO3- secretion in any of the age groups examined. Injection of 8-day-old rats with corticosterone acetate (250 mg/kg) did not affect ion or protein fluxes in EGF-treated 10-day-old rats. However steroid treatment did result in a reduction in Na+ and K+ fluxes in 15-day-old rats receiving EGF. EGF was detected in salivary and duodenal tissue of rats and in the maternal milk of rat dams.(ABSTRACT TRUNCATED AT 250 WORDS)
Differential modulation of Ca2(+)-activated K+ channels by substance P
Authors: Mayer E. A. , Loo D. D. , Kodner A. , Reddy S. N.
Published: December 2017

Substance P released from motoneurons or primary afferent nerves innervating the gut is an excitatory noncholinergic regulator of gastrointestinal motility and has been shown to stimulate contractions in longitudinal colonic muscle. By using the patch-clamp technique on single myocytes from the longitudinal muscle of the rabbit colon, we have studied the action of the peptide on membrane conductances. In cell-attached patches, addition of the peptide to the bath activates a large conductance Ca2(+)-activated K+ channel. At peptide concentrations (10(-12) M) that did not result in cell contraction, K+ channels were activated in a synchronized, cyclical fashion. The activation did not occur in the presence of nifedipine (10(-6) M), a blocker of dihydropyridine-sensitive Ca2+ channels. The activation was also absent when the cells were depolarized in 126 mM KCl-Ringer solution. In contrast, at a concentration of the peptide (10(-7) M) that resulted in cell contraction, there was a transient activation of K+ channels, followed by a prolonged inhibition. Nifedipine (10(-6) M) did not block the K+ channel activation by this concentration of the peptide. Removal of bath Ca2+ abolished activation of the K+ channels by both the high and low concentrations of substance P. These results indicate that substance P exerts its effect via two different membrane pathways for extracellular Ca2+.
Albumin enhances unidirectional fluxes of fatty acid across a lipid-water interface: theory and experiments
Authors: Weisiger R. A. , Pond S. M. , Bass L.
Published: December 2017

The effect of albumin concentration on the unidirectional fluxes of [3H]oleate across a lipid-water interface was measured by using a new model system consisting of a lipid phase (n-decane) separated from a stirred buffer phase by a planar interface. Albumin (0.15 mM) enhanced the flux of oleate from the lipid phase more than 30-fold. A similar increase in the oleate flux into the lipid was seen when the aqueous oleate and albumin concentrations were increased while keeping the unbound oleate concentration fixed. The ratio of the unidirectional fluxes was constant over the range of albumin concentrations investigated (1-100 microM). Analysis using rigorous rate theory indicated that the permeability of the interfacial surface was flux-limiting at high albumin, whereas diffusion across the unstirred water layer was flux-limiting at low albumin. The observed kinetic patterns are similar to results previously reported in cellular transport systems and attributed to specialized mechanisms for cellular uptake from the albumin-bound pool.
Platelet-activating factor-induced microvascular dysfunction: role of adherent leukocytes
Authors: Kubes P. , Suzuki M. , Granger D. N.
Published: December 2017

Platelet-activating factor (PAF) has been implicated in the pathogenesis of intestinal mucosal injury associated with endotoxemia, inflammation, allergic reactions, and ischemia-reperfusion. Although it is generally held that PAF initiates mucosal injury by enhancing transcapillary fluid and protein exchange, the effects of PAF on the intestinal microvasculature have not been defined to date. In this study we examined the influence of local intrarterial infusions of PAF (4, 20, and 40 ng/min) on intestinal transcapillary, lymphatic, and transmucosal water and protein fluxes. All of these parameters were increased by each of the concentrations of PAF. PAF caused a large rise in venous hematocrit without a corresponding increase in venous plasma protein concentration and a 14- to 37-fold increase in vascular protein flux. Local intra-arterial infusion of PAF promoted leukocyte adherence to mesenteric venular endothelium, a process that is inhibited by the monoclonal antibody, MoAb IB4. PAF-induced increments in intestinal lymph flow, venous hematocrit, and vascular protein flux were greatly attenuated in animals treated with MoAb IB4. The results of this study indicate that PAF promotes the filtration of fluid and protein across intestinal capillaries. These microvascular effects of PAF are mediated, in part, by adherent leukocytes.
Calcium uptake by brush-border and basolateral membrane vesicles in chick duodenum
Authors: Takito J. , Shinki T. , Sasaki T. , Suda T.
Published: December 2017

Calcium uptake was compared between duodenal brush-border membrane vesicles (BBMV) and basolateral membrane vesicles (BLMV) isolated from vitamin D-deficient chicks and those injected with 625 ng of 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3]. The uptake by BBMV in the 1 alpha,25-(OH)2D3-treated birds attained a maximum (280% of the control) at 12 h and was maintained at an elevated level (210%) at 24 h after the injection of the vitamin. In contrast, ATP-dependent calcium uptake by BLMV reached a maximum (185% of the control) at 6 h and decreased to the control level at 24 h. The kinetic analysis revealed that 1 alpha,25(OH)2D3 increased Vmax values without any changes in apparent Km values in both BBMV and BLMV. The activity of ATP-dependent calcium uptake was localized exclusively in the basolateral membrane, and the activity was inhibited by vanadate (IC50, 1 microM), but not by oligomycin, theophylline, calmodulin, trifluoperazine, or calbindin D28K. These results indicate that calcium transport through both the brush-border and basolateral membranes is involved in the 1 alpha,25(OH)2D3-dependent intestinal calcium absorption. The initiation of calcium absorption by 1 alpha,25(OH)2D3 appears to be due to an increase in the rate of calcium efflux at the basolateral membrane rather than the rate at the brush-border membrane.
Mechanical properties of isolated human esophageal smooth muscle
Authors: Tottrup A. , Forman A. , Uldbjerg N. , Funch-Jensen P. , Andersson K. E.
Published: December 2017

Isolated smooth muscle strips from the human esophagus representing both the longitudinal and circular layers of the esophagogastric junction and the esophageal body were prepared. The strips were mounted in organ baths, and resting length was defined. By repeatedly increasing the length of the strips with 20% of resting length and recording values of resting and active tensions, length-tension relations for each muscle type were constructed. Only circular strips from the esophagogastric junction developed active, resting tension, disclosed by replacing the normal Ca2(+)-containing Krebs solution with Ca2(+)-free medium. Carbachol (10(-6) M) was used for submaximal activation of the contractile apparatus. At lengths between 180 and 260% of resting length, all strips reached optimum length (LO) where further elongation gave no further increase in active tension development. Repeated stimulations with carbachol was possible at a length of 200% of LO without affecting reproducibility. Determination of different collagen components revealed no differences between muscle types.
Somatostatin regulates duodenal cholecystokinin and somatostatin messenger RNA
Authors: Kanayama S. , Liddle R. A.
Published: December 2017

The gastrointestinal peptides, cholecystokinin (CCK) and somatostatin, are produced by discrete endocrine cells in the mucosa of the small intestine. Although somatostatin may inhibit CCK secretion, the mechanism by which this occurs is unknown. The present study was designed to determine the effect of somatostatin on intestinal CCK and somatostatin mRNA levels. Rats, prepared with indwelling intraduodenal and jugular cannulas, were first fed an elemental diet that did not stimulate CCK release. Next, as a means of stimulating CCK secretion, soybean trypsin inhibitor was added to the diet and perfused intraduodenally at 50 mg/h for 24 h. Trypsin inhibitor caused an 11-fold increase in plasma CCK levels and a 2.4-fold increase in duodenal CCK mRNA levels. Simultaneous intravenous infusion of somatostatin-14 (1-100 micrograms.kg-1.h-1) reduced trypsin inhibitor-stimulated CCK levels by 50% and lowered trypsin inhibitor-stimulated CCK mRNA levels by 58%. Somatostatin infusion also reduced intestinal somatostatin mRNA levels stimulated by trypsin inhibitor but did not affect basal somatostatin mRNA levels. Duodenal CCK and somatostatin peptide concentrations did not change under any of the experimental conditions. These studies demonstrate that somatostatin reduces duodenal CCK mRNA levels stimulated by diet and suggest that somatostatin itself inhibits duodenal somatostatin gene expression.
Inhibition of intestinal degradation of somatostatin by rat milk
Authors: Rao R. K. , Koldovsky O. , Davis T. P.
Published: December 2017

In vitro degradation of 125I-labeled somatostatin-14 (Tyr11) [I-SS-14(Tyr11)] by luminal flushings of rat gastrointestinal segments was studied to characterize the fate of somatostatin in the gastrointestinal lumen. In addition, we evaluated the effect of rat milk as a potential inhibitor of luminal degradation of 125I-SS-14(Tyr11). Degradation of 125I-SS-14(Tyr11) was not detected in stomach flushings from either suckling or weanling rats. Luminal flushings from the small intestine degraded 125I-SS-14(Tyr11), with a gradient increase of activity from duodenum to midjejunum (degradation in suckling rat midjejunum and ileum was about five times lower than that in weanling rat). Degradation of 125I-SS-14(Tyr11) by luminal flushings of suckling rat midjejunum was dose dependently inhibited by rat milk casein and soluble fractions. Inhibitory activity of rat milk soluble fraction was heat labile and several times more potent than that of casein fraction. Casein fraction appeared to be stable at 100 degrees C for up to 30 min of exposure. These studies suggest that somatostatin is stable in the gastric lumen and that milk protects somatostatin from intestinal luminal proteolysis, indicating a possible physiological significance of milk-borne SS-14 for the suckling rat gastrointestinal tract.
Tachykinins as transmitters of ascending contractile component of the peristaltic reflex
Authors: Grider J. R.
Published: December 2017

Pages G709-G714: J. R. Grider. “Tachykinins as transmitters of ascending contractile component of the peristaltic reflex.” Page G711: Fig. 1 should appear as follows:
Effect of histamine on the basolateral K+ conductance of frog stomach oxyntic cells and surface epithelial cells
Authors: Debellis L. , Curci S. , Fromter E.
Published: December 2017

The transepithelial potential difference (Vt) and resistance (Rt) and the basolateral cell membrane potential (Vs) of oxyntic cells (OC) and surface epithelial cells (SEC) were measured in isolated stomachs of Rana esculenta. At rest, Vs of OC and SEC was virtually identical [-66.3 +/- 4.5 (SD) (n = 10) and -67.3 +/- 5.9 mV (n = 9)] and both cells responded to increasing serosal K+ concentration from 4 to 13 mmol/l with virtually the same depolarization (delta Vs,K) of +16.2 +/- 2.0 and +16.0 +/- 2.9 mV, respectively, while Vt declined by approximately half as much. Histamine (0.1 mmol/l) reduced Vt and Rt and increased the voltage divider ratio in both cell types, indicating a fall in basolateral membrane resistance. In the OC, this increase was neither associated with a significant alteration of Vs nor with a change in delta Vs,K. In the SEC, however, histamine markedly increased Vs to -75.5 +/- 7.3 mV (n = 9) as well as delta Vs,K to +18.5 +/- 2.6 mV, which was paralleled by an increase in delta Vt,K from 9.8 +/- 3.9 to +12.8 +/- 4.2 mV. The data indicate that 1) both OC and SEC respond to histamine, 2) both OC and SEC contain a basolateral K+ conductance that increases under histamine (in OC probably, in parallel with other ion conductances), and 3) in Rana esculenta the SEC contribute substantially to Vt.
Structural and functional characteristics of muscle from diabetic rodent small intestine
Authors: Nowak T. V. , Harrington B. , Weisbruch J. P. , Kalbfleisch J. H.
Published: December 2017

After 30 days of streptozotocin-induced diabetes, the small intestine from untreated diabetic, insulin-treated diabetic, and nondiabetic rodents was excised in toto and measured. Despite a net loss in body weight, the diabetic animals showed a near twofold increase in small intestinal weight. This was characterized by a 148% increase in mucosal mass as well as a 39% increase in intestinal smooth muscle mass (P less than 0.05, respectively). The diabetic intestine was significantly longer and had a greater diameter and surface area. Diabetes significantly increased mucosal mass per unit surface area but produced an insignificant decrease in smooth muscle mass per unit surface area. Insulin treatment of the diabetic animals prevented the increase in total mucosal mass and mucosal mass per unit surface area. Insulin treatment also prevented the increase in smooth muscle mass, but reduced smooth muscle mass per unit surface area to a level significantly less than that found in nondiabetic intestine. In vitro dose-response studies of circular and longitudinal small intestinal muscle from the diabetic animals showed normal tension development and sensitivity to both bethanechol chloride and physostigmine. These observations show that the diabetic state produces alterations in not only mucosal but also smooth muscle mass in the small intestine. However, despite these morphological changes, diabetic intestinal smooth muscle retains its sensitivity to cholinergic stimulation and its capacity for tension generation.