bluuebunny/crossref_metadata_2025 huggingface dataset:
Histamine augments colonic secretion in guinea pig distal colon
Authors: Wang Y. Z. , Cooke H. J. , Su H. C. , Fertel R.
Published: December 2017

We tested the hypothesis that the role of histamine in the control of intestinal secretion is mediated by prostaglandins (PGs). The effects of histamine on ion transport were examined in muscle-stripped sheets of mucosa/submucosa set up in flux chambers. Histamine evoked a transient concentration-dependent increase in short-circuit current (Isc) that was reduced by the Cl- transport inhibitor bumetanide. Histamine also caused the release of PGE2. The Isc response to histamine was reduced by indomethacin and piroxicam, which block PG formation, but not by nordihydroguaiaretic acid, which prevents production of lipoxygenase products. 2-Methylhistamine, but not dimaprit, evoked a concentration-dependent increase in Isc. The Isc response to histamine was reduced by the H1-blocker pyrilamine, but not by the H2-antagonist cimetidine. In addition to its direct effect, histamine augmented the responses of endogenously released neurotransmitters with and without indomethacin and hexamethonium. Tetrodotoxin (TTX) reduced the Isc response to 10(-3) M histamine. In the presence of TTX, exogenous histamine amplified the responses to PGs, vasoactive intestinal polypeptide, 2-chloroadenosine, bethanechol, and carbachol. These results suggest that histamine acts at H1-receptors on cells within the gut to mediate intestinal Cl- secretion in part by releasing PGs and by augmenting the actions of endogenously released neurotransmitters. Our results indicate that histamine has a role in the regulation of colonic transport function.
Circulating xanthine oxidase: potential mediator of ischemic injury
Authors: Yokoyama Y. , Beckman J. S. , Beckman T. K. , Wheat J. K. , Cash T. G. , Freeman B. A. , Parks D. A.
Published: December 2017

Reactive oxygen metabolites generated from the enzyme xanthine oxidase (XO) play an important role in the pathogenesis of ischemia-induced tissue injury. The observation that intracellular proteins such as aspartate transaminase (AST) and alcohol dehydrogenase (ADH) are released from the ischemic liver during reperfusion led us to postulate that XO could be released into the systemic circulation. Livers from fasted rats were extirpated, perfused with oxygenated Krebs-Henseleit buffer, and subjected to 2 h ischemia followed by 2 h reperfusion. Reperfusion increased AST in the perfusate from 1 +/- 1 to 830 +/- 280 U/l, whereas ADH increased from 0.3 +/- 0.1 to 95 +/- 26 U/l. Concomitantly, xanthine dehydrogenase (XDH) + XO activity in the perfusate increased from 0 to 4.1 +/- 1.0 mU/ml. A 64% decrease in endogenous tissue XDH + XO activity paralleled release of XDH + XO. The XDH + XO activity predicted to appear in the circulation after hepatic ischemia was sufficient, when supplied with substrate, to produce severe vascular endothelial injury in vitro, even in the presence of serum or whole blood. These results suggest that massive quantities of XDH and XO are released into the circulation after hepatic ischemia and that the resulting reactive oxygen metabolites could produce widespread tissue injury.
Human lower esophageal sphincter pressure response to increased intra-abdominal pressure
Authors: Mittal R. K. , Fisher M. , McCallum R. W. , Rochester D. F. , Dent J. , Sluss J.
Published: December 2017

We studied the effects of increased intra-abdominal pressure on the lower esophageal sphincter (LES) pressure in 15 healthy subjects. The role of the diaphragm in the genesis of LES pressure during increased intra-abdominal pressure was determined by measuring diaphragm electromyogram (EMG). The latter was recorded using bipolar intraesophageal platinum electrodes that were placed on the nonpressure sensing surface of the sleeve device. We also measured the LES pressure response to increased intra-abdominal pressure during inhibition of the smooth muscles of the LES by intravenous atropine (12 micrograms/kg). Straight-leg raising and abdominal compression were used to increase intra-abdominal pressure. Our results show that the increase in LES pressure during straight-leg raising is greater than the increase in gastric pressure. During abdominal compression, the rate of LES pressure increase is faster than that of the gastric pressure, suggesting an active contraction at the esophagogastric junction. The increase in LES pressure during periods of increased intra-abdominal pressure is associated with a tonic contraction of the crural diaphragm as demonstrated by EMG recording. Atropine inhibited the resting LES pressure by 50-70% in each subject but had no effect either on the peak LES pressure attained during increased intra-abdominal pressure or tonic crural diaphragm EMG. We conclude that 1) there is an active contraction at the esophagogastric junction during periods of increased intra-abdominal pressure and 2) tonic contraction of the crural diaphragm is a mechanism for this LES pressure response.
Circadian rhythms of biliary protein and lipid excretion in rats
Authors: Nakano A. , Tietz P. S. , LaRusso N. F.
Published: December 2017

To gain insight into the mechanisms by which hepatocytes release lipids and proteins into bile, we studied extended, steady-state secretion of bile, lipids, and lysosomal and canalicular membrane proteins in freely moving, unanesthetized rats with chronic bile fistulas. We found circadian rhythms of biliary secretion for all measured constituents. In the basal state (nocturnal feeding), two distinct secretory patterns emerged: type 1, characterized by a peak at midnight and a nadir at noon; and type 2, characterized by a peak at 8 A.M. and a nadir at 8 P.M. We observed parallel, type 1 circadian rhythms of excretion for bile, biliary lipids (bile acid, cholesterol, phospholipid), and a canalicular membrane enzyme (alkaline phosphodiesterase I). In contrast, a type 2 circadian rhythm was observed for the outputs of two lysosomal enzymes. Hepatic lysosomal enzyme concentrations and the number of pericanalicular lysosomes decreased (P less than 0.05) by 15 and 35%, respectively, at the nadir of their biliary output relative to the time of their peak outputs. In response to daytime feeding, major shifts in the circadian rhythms of excretion of biliary constituents occurred such that secretion of bile, lipids, and the canalicular membrane protein adopted a type 2-like rhythm, whereas the biliary secretion of the lysosomal proteins exhibited a type 1-like pattern. These results indicate that bile flow and biliary excretion of individual lipids and proteins exhibit distinct circadian rhythms that are altered by feeding. Secretory events at the canaliculus that depend on the transmembrane flux of bile acids, such as water and lipid movement or the solubilization of membrane proteins, display a common rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)
Propagation velocities and frequencies of contractions along canine small intestine
Authors: Siegle M. L. , Buhner S. , Schemann M. , Schmid H. R. , Ehrlein H. J.
Published: December 2017

This study was performed to clarify in detail the behavior of the propagation velocities and frequencies of contractions along the canine small intestine. In conscious dogs, duodenal, jejunal, and ileal contractions were recorded by multiple, closely spaced strain gauges and analyzed by a computerized method. During both the interdigestive and postprandial states, the propagation velocity increased from the duodenal bulb to the distal duodenum and declined aborally within the jejunum, reaching rather constant values in the ileum. The decrease was steepest in the proximal part of the jejunum. In contrast to the propagation velocities, the contraction frequencies were almost constant in the upper small intestine. In the ileum, the contraction frequencies were markedly lower than in the upper small intestine, indicating that the aboral decrease in frequency occurred in the distal parts of the jejunum. We conclude that both the propagation velocities and the frequencies of contractions decline aborally in a nonlinear fashion. However, the nonlinear patterns of the frequency and the propagation velocity gradients are different.
Ontogenetic development of transporter regulation in bullfrog intestine
Authors: Toloza E. M. , Diamond J. M.
Published: December 2017

Intestinal nutrient transporter activity is adapted to dietary substrate levels on three time scales: reversibly, within an adult individual, to rapid dietary changes; developmentally, to normal ontogenetic changes in diet; and evolutionarily, among carnivores, omnivores, and herbivores, to a species' natural diet. Does the capacity for rapid reversible adaptation itself vary adaptively during development? Substrate-dependent regulation would make functional sense in herbivorous/omnivorous tadpoles in which dietary substrate levels fluctuate unpredictably, but would serve no purpose in strictly carnivorous adult bullfrogs in which dietary protein is always high and carbohydrate is low. Hence, we fed premetamorphosis bullfrog tadpoles either boiled lettuce (high in carbohydrate, low in protein) or ground beef (high in protein, low in carbohydrate). Gut weight relative to body weight was higher in lettuce-fed tadpoles. Glucose uptake was greater and proline uptake slightly less in lettuce-fed than in beef-fed tadpoles. The resultant ratio of glucose uptake capacity to proline uptake capacity was nearly twice as high in lettuce-fed as in beef-fed tadpoles, corresponding to a much higher ratio of dietary carbohydrate to protein. Adult frogs have been shown to lack such regulation. Therefore, the regulatory capacity seen in tadpoles must become lost during amphibian metamorphosis.
Molecular characterization of bombesin receptors on rat pancreatic acinar AR42J cells
Authors: Singh P. , Draviam E. , Guo Y. S. , Kurosky A.
Published: December 2017

A biologically active, chemically defined, radioactive ligand was used for characterizing bombesin (BBS) receptors on rat pancreatic acinar cancer cells (AR42J). [Tyr4]BBS, iodinated with enzymobeads and fractionated by high-performance liquid chromatography, was monitored for biological activity as evidenced by gastrin release from perfused isolated rat stomach. The monoiodinated peptide peak was greater than 95% biologically active, with a specific activity of greater than 2,000 disintegrations.min-1.fmol-1. The maximum number of BBS receptors per cell were measured at 30 degrees C after 20-25 min of incubation; binding was submaximum at temperatures lower or higher than 30 degrees C. A single class of high-affinity binding sites (Kd = 1.77 +/- 0.21 nM) was identified for BBS on AR42J cells and nonspecific binding was less than 20-30% at all points. A total of 1.47 +/- 0.14 x 10(5) specific BBS binding sites per cell were measured that were specific for BBS and gastrin-releasing peptide (GRP) analogues. Iodinated GRP-(1-27) was cross-linked to BBS receptors on AR42J cells using several bifunctional cross-linking reagents followed by polyacrylamide gel electrophoresis of the solubilized receptor complex under reducing and nonreducing conditions. A densitometric analysis of the autoradiographs demonstrated the presence of an approximately 80- to 85-kDa molecular form of the receptor as a major component under both reducing and nonreducing conditions. These results indicated that the receptor molecule is a single subunit without multiple chains covalently attached by disulfide bonding.
Absorption and metabolism of [3H]arachidonic and [14C]linoleic acid in essential fatty acid-deficient rats
Authors: Hjelte L. , Melin T. , Nilsson A. , Strandvik B.
Published: December 2017

[3H]arachidonic acid (20:4) and [14C]linoleic acid (18:2) were fed in a triolein emulsion to essential fatty acid-deficient (EFAD) rats and to age-matched controls. Tissues were analyzed for radioactivity of different lipid classes after 1, 2, and 4 h. As in earlier studies [Nilsson and Melin. Am. J. Physiol. 255 (Gastrointest. Liver Physiol. 19): G612-G618, 1988], control rats retained more [3H]20:4 than [14C]18:2 in all organs except adipose tissue. In EFAD rats, recovery of [14C]18:2 was increased in small intestine, liver, heart, and kidneys. In comparison to controls, EFAD rats retained much more [14C]18:2 in phospholipids of these organs. The increase in the incorporation of both 3H and 14C into phosphatidylethanolamine was particularly pronounced. Another striking feature was the drastic increase in the retention after 4 h of 14C in cardiolipin, which is specifically located in the inner mitochondrial membrane. In contrast, incorporation of both 3H and 14C into phosphatidylinositol was decreased or unchanged in EFAD rats. Although fecal fat excretion was increased there was no evidence for a malabsorption or an increased retention in intestinal triacyglycerol of the radioactive fatty acids in EFAD rats. The proportion of [14C]18:2 that had been converted to [14C]20:4 was generally low but increased significantly with time in the liver and intestine of EFAD rats.
[14C]urea and 58Co-EDTA as reference indicators in hepatic multiple indicator dilution studies
Authors: Pang K. S. , Barker F. , Schwab A. J. , Goresky C. A.
Published: December 2017

The space distribution and the processes underlying uptake of tracer substrate may be appraised by the multiple indicator dilution technique, after the simultaneous injection of noneliminated vascular (51Cr-labeled red blood cells), extracellular (125I-labeled albumin and [14C]sucrose for high and low molecular weight interstitial space, respectively), and cellular (3H2O) indicators and tracer substrate. When tracer substrates and/or their metabolites containing 14C or 3H labels are being studied, it becomes necessary to find substitutions for the similarly labeled noneliminated indicators. In red blood cell-perfused rat livers, 58Co-EDTA is found to be a good replacement for the low molecular weight interstitial reference; it has a space distribution indistinguishable from that for [14C]sucrose. [14C]urea and 3H2O, which distribute similarly in red blood cells, have similar outflow dilution profiles. With corrections for minor deviations in recovery [a ratio of 0.936 +/- 0.024 (SD)] and transit time [a ratio of 0.962 +/- 0.008 (SD)], the cellular water space can be closely approximated from the [14C]-urea curve. 58Co-EDTA and [14C]urea are reasonable substitutes for [14C]sucrose and 3H2O, respectively, in multiple indicator dilution liver perfusion studies for investigating transfer and removal characteristics of tracer substrates.
Intravenous amino acids stimulate human gallbladder emptying and hormone release
Authors: Nealon W. H. , Upp J. R. , Alexander R. W. , Gomez G. , Townsend C. M. , Thompson J. C.
Published: December 2017

Gallbladder stasis during prolonged total parenteral nutrition (TPN) has been documented. We have examined the effect of intravenous amino acid infusion on human gallbladder contraction and release of cholecystokinin (CCK). Five healthy adult volunteers were given amino acid infusions at different rates (65, 125, 240, and 600 mg.kg-1.h-1). The volume of the gallbladder was calculated by means of ultrasonographic measurements. Plasma samples were analyzed for CCK immunoreactivity. Gallbladder and hormone responses after intravenous amino acids were compared with responses after a fat meal, after a protein meal, and after ingestion of an oral amino acid mixture. We found that intravenous amino acids stimulated human gallbladder contraction in a dose-related manner. The mechanism of stimulation may be through the release of CCK although significant correlation was not demonstrated. The magnitude of response is similar to that seen after meal stimulation. To compare the delivery of amino acids during a standard meal and during each dose of intravenous amino acids, peripheral plasma levels of dietary amino acids were measured after a standard commercially prepared enteral supplement meal and after each dose of intravenous amino acids. Our lower doses of amino acid infused resulted in levels of circulating amino acid comparable to those after a meal. The induction of gallbladder contraction and release of CCK in human recipients of parenteral nutrition may be of value in some circumstances.
Maturation of the rat intestinal microvasculature from juvenile to early adult life
Authors: Unthank J. L. , Lash J. M. , Bohlen H. G.
Published: December 2017

The same region of intestinal ileum was compared in the same rats at 10 and 20 wk of age to determine if reported differences in vessel density between these ages were the result of changes in vessel numbers. The number and branching pattern of arterioles observed remained remarkably constant during the 10 wk between observations, and minimal enlargement of bowel mass occurred. No significant change in average maximum diameter of arterioles was observed. Although the total number of small arterioles did not change, vessels were gained and lost at an equal rate (7%) between 10 and 20 wk. There was no significant changes in means or frequency distributions of intercapillary distances in the radial or longitudinal bowel muscle layers. The results indicate that the intestinal microvascular branching pattern changes very little from juvenile to adult life. However, a slow turnover of small arterioles does occur, indicating an ongoing remodeling of the terminal vasculature during juvenile life.
Relation between small intestinal motor activity and transit in secretory diarrhea
Authors: Cowles V. E. , Sarna S. K.
Published: December 2017

Our objective in this study was to correlate small intestinal motor activity with transit time in the fed state under normal conditions and in the secretory state induced by cholera toxin. In the control state, transit time was strongly and inversely correlated with the mean distance of propagation and to a lesser degree with frequency and total duration of all contractions. By contrast, transit time was not correlated with total amplitude and area of all contractions. When contractions were separated into propagating and nonpropagating contractions, there was a highly significant inverse correlation between transit time and all parameters of propagating contractions but no relation with any parameter of nonpropagating contractions. Similar results were obtained during the secretory state induced by cholera toxin. The control data were used to develop a mathematical model to predict transit time from contractile parameters and was validated using the data obtained in the secretory state. Our findings demonstrate that transit through the small intestine in the normal and secretory states is strongly related to the parameters of propagating contractions but not to parameters of nonpropagating contractions.
Potent bombesin receptor antagonists distinguish receptor subtypes
Authors: von Schrenck T. , Wang L. H. , Coy D. H. , Villanueva M. L. , Mantey S. , Jensen R. T.
Published: December 2017

To determine whether newly described bombesin (BN) receptor antagonists distinguish subtypes of BN receptors, we investigated their abilities to interact with BN receptors on esophageal muscle or pancreatic acinar tissue. For inhibition of binding of 125I-[Tyr4]BN to rat pancreatic tissue, the relative potencies were [D-Phe6]BN-(6-13)ethyl ester (5 nM) greater than Ac-gastrin-releasing peptide (GRP)-(20-26)ethyl ester (17 nM) greater than [D-Phe6,Cpa,14, psi 13-14]BN-(6-14) (40 nM) greater than [Leu14, psi 13-14]BN (0.43 microM) greater than [Tyr4,D-Phe12]BN = [D-Pro4, D-Trp7,9,10]substance P (SP)-4-11 (13 microM) greater than [Leu14, psi 9,10]BN (32 microM) greater than [D-Arg1,D-Trp7,9,Leu11]SP (70 microM). Each antagonist also inhibited binding of 125I-[Tyr4]BN or 125I-Bolton-Hunter-neuromedin B to rat esophageal tissue, and the potency of each antagonist for each tracer was similar. In comparison to rat pancreas, [D-Phe6]BN-(6-13)ethyl ester, Ac-GRP-(20-26)ethyl ester, [D-Phe6,Cpa14, psi 13-14]BN-(6-14), [Leu14, psi 13-14]BN, and [Leu14, psi 9,10]BN had a 10,000-, 2,940-, 1,425-, 122-, and 4-fold, respectively, weaker affinity for BN receptors. In contrast [Tyr4,D-Phe12]BN, [D-Pro4,D-Trp7,9,10]SP-4-11, and [D-Arg1,D-Trp7,9,Leu11]SP had a 4-, 4-, and 9-fold, respectively, higher affinity compared with pancreatic tissue. Comparison of the activity of each peptide at inhibiting the ability of equipotent concentrations of BN or neuromedin B to stimulate contraction of rat esophageal muscle demonstrated that each peptide had the same relative potencies as for inhibiting binding.(ABSTRACT TRUNCATED AT 250 WORDS)
Validation of tonometric measurement of gut intramural pH during endotoxemia and mesenteric occlusion in pigs
Authors: Antonsson J. B. , Boyle C. C. , Kruithoff K. L. , Wang H. L. , Sacristan E. , Rothschild H. R. , Fink M. P.
Published: December 2017

Tonometry is a minimally invasive method for estimating gastrointestinal intramural pH (pHi). Tissue pH is calculated by using the Henderson-Hasselbalch equation and measurements of arterial [HCO-3] and CO2 tension (PCO3) of saline contained in a Silastic balloon within the lumen of the gut. The validity of the method rests on two key assumptions: 1) PCO2 in saline in the tonometer balloon is similar to tissue PCO2 and 2) tissue and arterial [HCO-3] are similar. To validate this method, ileal pHi measured directly with a microelectrode was compared with pHi estimated tonometrically in four groups of anesthetized pigs. Group I (n = 4) were controls. In group II (n = 4), intestinal tissue acidosis was induced by total occlusion of the superior mesenteric artery (SMA). In group III (n = 5), acidosis was induced by partial occlusion of the SMA. In group IV (n = 4), tissue acidosis was induced by endotoxemia. Agreement was excellent between direct and tonometric measurements in groups I and IV and less good in groups II and III. Weighted mean correlation coefficients (rw) for the two measurement methods were 0.743 and 0.9447 in groups II and IV, respectively. Correlation coefficients for the individual animals in group III were more variable than the other groups and ranged from 0.547 to 0.990. The tonometric method for measuring GI pHi is invalid under conditions of zero flow and leads to error under conditions of low flow. However, the method is reliable in the setting of tissue acidosis induced by endotoxemia.
Fate of dietary glutathione: disposition in the gastrointestinal tract
Authors: Hagen T. M. , Wierzbicka G. T. , Bowman B. B. , Aw T. Y. , Jones D. P.
Published: December 2017

Studies were performed in rats that had been fasted 24 h, fed a glutathione (GSH)-free semisynthetic diet (AIN-76), and fed the same diet supplemented with GSH. The results from the fasted rats and those fed GSH-free diet showed that the duodenum and jejunum contained 0.2-0.5 mumol of GSH/gram wet wt of luminal contents. The GSH contents of biliary juice was sufficient to maintain this amount of GSH in the intestinal lumen. Other analyses showed that cell sloughing, bacterial GSH content, and GSH secretion by epithelial cells of the jejunum were not sufficient to account for this content. GSH concentrations following consumption of a GSH-supplemented diet (5-50 mg/g AIN-76) showed a rapid increase in all regions of the small intestine and indicated that removal occurred primarily in the jejunum. However, the combined activities of brush-border gamma-glutamyltransferase and GSH uptake systems were not sufficient to remove all of the ingested GSH. Results from in situ vascular perfusions of small intestine showed that the upper jejunum is a principal site of GSH absorption. Measurements of the GSH-to-glutathione disulfide (GSSG) ratio in the lumen after ingestion of GSSG (5 mg/g diet) indicated that the upper small intestine also has a mechanism for reducing GSSG to GSH. The results therefore indicate that GSH is present in the lumen of the small intestine of rat under most if not all conditions. Although the physiological importance of luminal GSH remains unclear, it could potentially be used to detoxify reactive electrophiles in the diet or be absorbed for intracellular detoxication reactions.
Lipid binding to gastric mucin: protective effect against oxygen radicals
Authors: Gong D. H. , Turner B. , Bhaskar K. R. , Lamont J. T.
Published: December 2017

Gastric mucus forms a viscous gel overlying the gastric mucosa and is thought to protect the underlying mucosa from noxious agents such as acid, proteases, and bile salts. A common property of mucin, the principal glycoprotein in mucous secretions, is its ability to bind lipids. The purpose of this study was to determine if lipids bound to gastric mucin protect the mucin from oxygen radical attack. Pig gastric mucin, partially purified by Sepharose 4B gel chromatography, was found to contain large amounts of free fatty acids and cholesterol as well as lesser amounts of sphingomyelin and phospholipids. Purified mucin obtained by density-gradient ultracentrifugation in a CsCl gradient contained only trace amounts of fatty acids but no other lipids. Exposure to the oxygen radical-generating system iron/ascorbate caused a marked reduction in viscosity of purified mucin but did not affect partially purified mucin, suggesting that bound lipids shielded the mucin from attack by oxygen radicals. Using discontinuous sucrose-gradient ultracentrifugation in the presence of liposomes containing [3H]palmitic acid, we demonstrated that mucin is capable of binding fatty acids. We also observed a striking increase in solution viscosity of gastric mucin at low pH, a feature that might contribute to the ability of mucin to form a protective diffusion barrier for the underlying epithelium.
Characterization of sustained [Ca2+]i increase in pancreatic acinar cells and its relation to amylase secretion
Authors: Tsunoda Y. , Stuenkel E. L. , Williams J. A.
Published: December 2017

The sustained increase in cytosolic free Ca2+ concentration ([Ca2+]i) during maximal stimulation of rat pancreatic acini with carbamylcholine (10(-5) M) was investigated in individual acinar cells by microspectrofluorometric analysis of fura-2. After the large initial [Ca2+]i increase from intracellular stores, [Ca2+]i remained significantly elevated as long as the stimulus was applied. The amplitude of this plateau was dependent on the median Ca2+ concentration ([Ca2+]o) being 45-50 nM above prestimulation in medium with 1 mM [Ca2+]o increasing to 90 nM at 10 mM [Ca2+]o. This Ca2+ plateau was completely blocked by 2.5 mM Ni2+ and 0.25 mM La3+ but was unaffected by elevated K+ or the Ca2+ channel blocker D 600. Mn2+ was able to enter the cytosol after the cell stimulation as indicated by intracellular quenching of fura-2, indicating that acinar cells possess a Mn2(+)-permeable Ca2+ channel. Elimination of [Ca2+]o or addition of Ni2+ and Mn2+ to the medium reduced the level of sustained amylase secretion in a reversible manner under superfusion conditions. Increasing [Ca2+]i above the normal level by increasing [Ca2+]o had no effect on amylase secretion. The process for sustained Ca2+ entry was pH sensitive; decreasing extracellular pH (pHo) to 6.5-6.8 during the cell stimulation resulted in a reduction of the sustained [Ca2+]i plateau level and a decrease in sustained amylase secretion. By contrast, increasing pHo to 8.0 enhanced the level of the sustained [Ca2+]i in a Ni2(+)-sensitive manner but did not increase amylase release. Changes in cytosolic pH had only minimal effects on the sustained [Ca2+]i plateau. The results demonstrate a receptor-mediated Ca2+ entry mechanism, which results in a small increase in [Ca2+]i important in the maintenance of sustained amylase release.
Influence of anesthesia, postanesthetic state, and restraint on superior mesenteric arterial flow in normal rats
Authors: Colombato L. A. , Sabba C. , Polio J. , Groszmann R. J.
Published: December 2017

To exclude possible confounding effects of anesthesia on splanchnic hemodynamics, two different awake postanesthetic models (PAM), restrained and unrestrained, have been used. However critical analysis of the splanchnic hemodynamic state in these models is not available. We conducted experiments using chronically implanted pulsed-Doppler flow probes on the superior mesenteric artery (SMA) in ketamine-anesthetized and in postanesthetic restrained and unrestrained normal rats. Baseline values of mean SMA flow were compared with those under anesthesia (30 min), PAM (restrained or unrestrained at 90 and 150 min), and reanesthesia. Sham-anesthetized unrestrained animals provided control values. The same animals (n = 7) underwent the restrained, unrestrained, and control experiments at least 5 days apart. Ketamine anesthesia did not significantly alter mean SMA flow (89 +/- 9% of baseline) compared with sham-anesthetized controls (99 +/- 9%). Mean SMA flow in both PAM, restrained and unrestrained, had a significant (P less than 0.05) decrease at 90 min (78 +/- 8 and 83 +/- 12%) and at 150 min (68 +/- 14 and 78 +/- 14%) when compared with baseline and control. Reanesthesia returned SMA flows to baseline values (91 +/- 16%). The variability of mean SMA flow was significantly increased in both PAM. Maximum variability was observed in the restrained model (69 +/- 32%). These results indicate 1) that ketamine anesthesia does not significantly alter SMA flow and 2) that both the restrained and unrestrained PAM exhibit significant alterations of the splanchnic circulation for at least 2 h after complete recovery from anesthesia. Thus, in the absence of critical evaluation, results of splanchnic hemodynamic studies with these models should be questioned.(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of binding sites for VIP-related peptides and activation of adenylate cyclase in developing pancreas
Authors: Le Meuth V. , Farjaudon N. , Bawab W. , Chastre E. , Rosselin G. , Guilloteau P. , Gespach C.
Published: December 2017

HPLC-purified 125I-labeled vasoactive intestinal peptide (VIP) bound in a specific, saturable, and reversible manner to pancreatic plasma membranes isolated from newborn calves, from milk-fed calves at 28 and 119 days, and from weaned calves at 119 days. A series of VIP analogues, including pituitary adenylate cyclase-activating polypeptide (PACAP), displaced 125I-VIP binding and activated adenylate cyclase in the same order of relative potency: PACAP-38 greater than helodermin greater than VIP, PACAP-27 greater than PHM (human peptide with NH2-terminal histidine and COOH-terminal methionine amide). At maximally effective concentrations, these five peptides produced the same two- to threefold increase of adenylate cyclase activity in pancreatic membranes from newborn and 28-day-old calves, and fourfold in ruminant or preruminant animals at 119 days. The activation constant for PACAP-38 ranged from 0.1 to 0.34 nM throughout the postnatal development. Helospectin I and II were three times less potent than VIP in inhibiting 125I-VIP binding. At concentrations up to 0.1 microM, secretin, rat and human growth hormone-releasing factors, glucagon, oxyntomodulin, the truncated form of glucagon-like peptide-1 lacking the 6 NH2-terminal amino acid sequence (TGLP-1), GLP-2, gastric inhibitory peptide, gastrin, CCK, and insulin had no effect on binding. Scatchard plots from 28- and 119-day-old calves were compatible with the presence of two classes of 125I-VIP binding sites: one with a high affinity for VIP and a low binding capacity (Kd = 0.11-0.4 nM, Bmax = 66-174 fmol/mg protein) and the other with a low affinity and high binding capacity. At birth, only one class of binding sites was observed (Kd = 0.4 nM, Bmax = 858 fmol/mg protein). The covalently cross-linked PACAP-preferring 125I-VIP binding site is a glycoprotein of 55 kDa with higher sensitivity to PACAP vs. helodermin and VIP. Our results suggest that calf pancreatic functions might be regulated at an early stage of postnatal development by PACAP receptors linked to cAMP generation.
Microcirculatory changes in sodium taurocholate-induced pancreatitis in rats
Authors: Kusterer K. , Enghofer M. , Zendler S. , Blochle C. , Usadel K. H.
Published: December 2017

Using an in vivo microscopy technique, we studied the microcirculatory changes in sodium taurocholate-induced pancreatitis in rats. With a computerized image analyzer system, blood flow, vascular permeability changes, and capillary densities were measured. Intraductal infusion of 0.4 ml saline had only minor effects on the microcirculation. Various concentrations and volumes of sodium taurocholate solutions were infused into the pancreatic duct. Sodium taurocholate (0.4 ml, 4%) led to increased vascular permeability preceding stasis within 232 +/- 47 s, followed by hemorrhagic necrosis in the head of the pancreas. In the corpus close to the tail of the pancreas capillary blood flow was maintained. In conclusion, this study shows that the microcirculation of the pancreas can be excellently investigated with in vivo microscopy. With this method, tremendous distribution disturbances of the microcirculation in the pancreas can be seen in the course of acute pancreatitis. Vascular permeability changes and stasis of the microcirculation represent the primary microcirculatory events in acute pancreatitis induced by sodium taurocholate in the areas where hemorrhagic necrosis occurs.
Glutamate and GABA-mediated synaptic currents in neurons of the rat dorsal motor nucleus of the vagus
Authors: Travagli R. A. , Gillis R. A. , Rossiter C. D. , Vicini S.
Published: December 2017

We report the presence of excitatory and inhibitory spontaneous and evoked synaptic currents in the dorsal motor nucleus of the vagus (DMV) in the rat upon vagal and perivagal stimulation. Whole cell current-clamp recordings from anatomically identified DMV neurons in rat brain stem slices show that these neurons are capable of sustained slow-frequency action potential firing probably because of the presence of pacemaker current. Spontaneously occurring, tetrodotoxin-resistant miniature inhibitory and excitatory synaptic potentials were observed. Stimulation of the vagus mostly induced antidromic action potentials in DMV neurons. However, careful positioning of the stimulating electrode in the tissue surrounding the recording neuron, and sometimes in the vagus itself, was capable of evoking orthodromic-evoked mixed inhibitory-excitatory postsynaptic potentials, and eventually, action potentials. Whole cell voltage-clamp recordings of the synaptic currents corresponding to these synaptic potentials in the presence of pharmacological antagonists of the neurotransmitters gamma-aminobutyric acid (GABA), glutamate, and glycine receptor subtypes indicate that the inhibitory synaptic currents are mediated by GABA-activated Cl- channels, while the excitatory synaptic currents are due to activation of ionotropic glutamate receptors of the N-methyl-D-aspartic acid (NMDA) and non-NMDA subtypes.
Quantification of motor pathways to the pelvic floor in humans
Authors: Herdmann J. , Bielefeldt K. , Enck P.
Published: December 2017

The motor innervation of the pelvic floor plays a major role in defecation disorders such as fecal incontinence. It consists of central motor pathways and peripheral nerve fibers. Transcranial magnetoelectric stimulation of the brain and magnetoelectric stimulation of the lumbosacral motor roots were performed in 10 healthy volunteers. Motor evoked potentials were recorded from the external anal sphincter. This procedure allowed differentiation between a predominantly central and a solely peripheral component of the motor innervation of the external and sphincter. To compare these recordings with well-established data, motor evoked potentials were also recorded from the anterior tibial muscle. The central motor conduction time was 20.9 +/- 2.4 ms to the external anal sphincter and 14.8 +/- 2.3 ms to the anterior tibial muscles. Central motor conduction velocities were 40.7 +/- 5.2 and 55.5 +/- 7.6 m/s, respectively. This showed that conduction in the central fibers to the external anal sphincter was significantly slower than in those to the anterior tibial muscle. We conclude 1) that magnetoelectric stimulation allows differentiation between central and peripheral portions of the motor innervation of the pelvic floor, and 2) that central motor pathways innervating the pelvic floor differ significantly in their physiological properties from those innervating limb muscles.
Intracellular pathways for contraction in gastroesophageal smooth muscle cells
Authors: Hillemeier C. , Bitar K. N. , Marshall J. M. , Biancani P.
Published: December 2017

Intracellular pathways utilized for contraction in response to acetylcholine (ACh), inositol 1,4,5-trisphosphate (IP3), and KCl were examined in isolated circular smooth cells from the esophagus, lower esophageal sphincter (LES), and fundus. In physiological nutrient salt solution (PSS) intact muscle cells isolated from these three tissues responded in a similar dose-dependent manner to ACh. In all tissues the contractile response to ACh was maximal at 30 s. Contraction of smooth muscle cells from LES and fundus did not change after incubation in Ca(2+)-free medium, but contraction of esophageal cells was abolished. KCl-induced contraction of all three cell types was also abolished after incubation in Ca(2+)-free medium. After permeabilization with saponin in cytosolic (low Ca2+) salt solution, muscle cells from LES and fundus contracted in a dose-dependent manner in response to IP3, whereas cells from esophagus did not contract. Contraction of permeabilized LES and fundic cells in response to ACh was the same as that of intact muscle cells. Response to IP3 was more rapid than response to ACh; it reached 85% of maximum by 5 s and peaked at 15 s. Calmodulin antagonists W-7 and CGS 9343B blocked contraction in response to ACh in intact cells from LES and fundus but had no effect on ACh-induced contraction in esophageal cells. These antagonists blocked IP3-induced contraction in permeabilized cells from LES and fundus. KCl-induced contraction in intact cells from all three tissues was not blocked by either W-7 or CGS 9343B. These data suggest that calmodulin antagonists block contraction mediated by release of intracellular Ca2+ induced by ACh or IP3.(ABSTRACT TRUNCATED AT 250 WORDS)
Reduced glutathione protects cultured gastric mucosal cells from suckling rats against acid
Authors: Mutoh H. , Ota S. , Hiraishi H. , Ivey K. J. , Terano A. , Sugimoto T.
Published: December 2017

We examined the role of reduced glutathione as a defense mechanism against acid-induced gastric mucosal cell damage in vitro. Cellular stores of reduced glutathione were depleted by reaction with diethyl maleate (DEM) or 1-chloro-2,4-dinitrobenzene (CDNB) and increased by reaction with L-cysteine. Depletion of cellular glutathione by reaction with DEM or CDNB potentiated gastric mucosal cell lysis by acid. Increase of cellular glutathione by L-cysteine decreased cell lysis by acid. Altering the cellular reduced-to-oxidized glutathione ratio by tert-butyl hydroperoxide or diamide increased cellular susceptibility to acid. Reduced glutathione is essential for glutathione peroxidase to catalyze hydrogen peroxide. We further studied whether oxygen free radicals were involved in the pathogenesis of acid-induced gastric mucosal injury in vitro. Neither superoxide dismutase, catalase, nor dimethyl sulfoxide decreased acid-induced gastric mucosal cell damage. We conclude that reduced glutathione plays an important role as a defense mechanism against acid-induced injury in cultured rat gastric mucosal cells. Production of oxygen radical in response to acid exposure may occur intracellularly, since exogenous oxygen radical scavengers, which do not gain access to the interior of cells, had no protective effect. Reduced glutathione might protect gastric mucosal cells by mechanisms other than the elimination of oxygen free radicals.
Pancreatic gene expression is altered during acute experimental pancreatitis in the rat
Authors: Iovanna J. L. , Keim V. , Michel R. , Dagorn J. C.
Published: December 2017

We investigated pancreatic gene expression in the rat in response to taurocholate-induced acute pancreatitis. Concentrations of transcripts encoding pancreatic protein showed noncoordinated alterations. Contents in amylase, trypsinogen I, chymotrypsinogen B, elastase 1, and procarboxypeptidase A mRNAs decreased by greater than 50% during the acute phase (days 0-2), whereas actin and lithostathine mRNAs increased 5 and 0.6 times, respectively, and pancreatitis-associated protein (PAP) mRNA increased greater than 200 times, indicating redirection of the pattern of gene expression. Synthesis of pancreatic proteins was also altered in a noncoordinated manner. During the acute phase, it decreased more for trypsinogen I and chymotrypsinogen B than for amylase and lipase, whereas synthesis of the PAP increased dramatically. For amylase and chymotrypsinogen B, we compared the patterns of changes in mRNA concentrations, rates of synthesis, and pancreatic contents. Changes in enzyme contents and synthetic rates were temporally correlated during the acute phase. On the contrary, changes in mRNA concentrations and enzyme synthesis were not coordinated, suggesting that control of synthesis partly occurred at the posttranscriptional level. It was concluded that induction of pancreatitis is accompanied by transcriptional and posttranscriptional modifications resulting in rapid and massive rearrangement of the pattern of pancreatic protein gene expression.
Gastrin potentiates histamine-stimulated aminopyrine accumulation in isolated rat parietal cells
Authors: Cabero J. L. , Li Z. Q. , Mardh S.
Published: December 2017

Rat gastric mucosal cells, containing 25-35% parietal cells, were obtained by a modified isolation procedure involving protease, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and mechanical treatments. Parietal cell responsiveness to secretagogues was assessed by the accumulation of the weak base [14C]aminopyrine in intracellular acidic compartments. Histamine, without phosphodiesterase inhibitors, dose dependently stimulated aminopyrine accumulation with an effective concentration producing 50% of maximal response of 13 microM and a maximal effective dose of 100 microM. Pentagastrin and rat gastrin-17 alone were ineffective but potentiated dose dependently the action of 100 microM histamine. The mean potentiating effect varied from 32 to 70% for 100 nM pentagastrin and from 36 to 95% for 100 nM rat gastrin-17. Pentagastrin (100 nM) also potentiated the effect of 1 mM dibutyryladenosine 3',5'-cyclic monophosphate (cAMP) by 44%, but it did not increase further the stimulation by carbachol. The potentiating effect of pentagastrin on histamine- and dibutyryl cAMP-stimulated aminopyrine accumulation was also observed after enrichment of parietal cells to 65-85%. The endogenous histamine was insufficient to stimulate acid production. Therefore gastrin appears to have a direct action also in rat parietal cells.
Oxygen metabolites stimulate mucous glycoprotein secretion from cultured rat gastric mucous cells
Authors: Hiraishi H. , Terano A. , Ota S. , Mutoh H. , Sugimoto T. , Razandi M. , Ivey K. J.
Published: December 2017

The aims of this study were to investigate the interaction between oxygen radicals and mucus secretion from cultured rat gastric mucous cells, and to assess the role of prostaglandin production in the modulation of mucus secretion in vitro. Xanthine oxidase in the presence of hypoxanthine caused a dose-dependent increase in the presence of hypoxanthine caused a dose-dependent increase of mucus secretion, as assessed by release of [3H]glucosamine from prelabeled cells, whereas xanthine oxidase or hypoxanthine alone did not. Xanthine oxidase (10 mU/ml) increased release of [3H]glucosamine by 57 +/- 6% compared with control values (P less than 0.001). Catalase (3,000 U/ml) inhibited xanthine oxidase-induced mucus secretion by 69 +/- 9% (P less than 0.01), whereas superoxide dismutase did not. Pretreatment with deferoxamine, an inhibitor of hydroxyl radical generation through chelating ferric ion, diminished oxygen radical-induced mucus release to control values. Xanthine oxidase dose dependently stimulated prostaglandin E2 (PGE2) production, which was blocked by catalase but not by superoxide dismutase. However, oxygen radical stimulation of mucus secretion was not inhibited by the addition of indomethacin. Moreover, PGE2, exogenously administered, did not significantly accelerate mucus secretion. Stimulation of mucus secretion by oxygen radicals was not accompanied by increased 51Cr release or by leakage of intracellular lactate dehydrogenase. These results suggest that oxygen species, particularly hydroxyl radical, stimulate mucous glycoprotein secretion from cultured rat gastric mucous cells. However, it seems unlikely that prostaglandin production mediates the oxygen species-induced stimulation of mucus secretion.
Pancreatic microvascular permeability in caerulein-induced acute pancreatitis
Authors: Sweiry J. H. , Mann G. E.
Published: December 2017

Microvascular permeability was studied in the isolated perfused rat pancreas using a rapid multiple indicator-dilution technique. Capillary extractions, permeability-surface area products (PS), and extravascular volumes of distribution (EVV) were determined for 22Na+, 51Cr-labeled EDTA, [57Co]-cyanocobalamin (B12), and 125I-labeled insulin at various perfusion flows. Permeability to albumin was negligible. PS for Na+ and EDTA increased with increasing flow, whereas PS for cyanocobalamin and insulin approached diffusion-limited exchange at flows greater than 3 ml.min-1.g-1. Permeability coefficients for Na+, EDTA, B12, and insulin were 36, 22, 11, and 3.48 x 10(-5) cm/s, respectively, and the permeability ratio for B12/insulin (3.16) indicated restricted diffusion to insulin. In the presence of unlabeled B12 and insulin EVV (0.15-0.19 ml/g) for EDTA, B12 and insulin approximated the interstitial volume. Caerulein-induced pancreatitis or treatment with the synthetic protease inhibitor camostate had no significant effects on permeability. In caerulein-treated rats, EVV for B12 was elevated (0.17 +/- 0.01 vs. 0.28 +/- 0.06; P less than 0.01), reflecting the interstitial edema associated with this model of pancreatitis. Permeability of the rat pancreatic microvasculature is similar to that of other fenestrated tissues, but it is 10- to 20-fold greater than that of continuous capillaries. Contrary to previous assumptions, permeability does not appear to be increased after induction of acute interstitial pancreatitis.