bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of gastrointestinal responses to CCK-8 and associated with vomiting
Authors: Lang I. M. , Marvig J. , Sarna S. K.
Published: December 2017

The gastrointestinal motor and myoelectric responses associated with vomiting induced by apomorphine (APO) and activated by cholecystokinin octapeptide (CCK-8) were compared as well as the mechanisms of initiation of these responses. Twelve dogs were surgically implanted with strain-gauge force transducers or bipolar electrodes for chronic recording of contractile or electrical activity. The responses to CCK-8 were determined in the fasted state and compared with the gastrointestinal motor and myoelectric correlates of vomiting activated by APO. After recording control responses, the effects of the following agents on these responses were determined: atropine, domperidone, and proglumide. In addition, the effects of supradiaphragmatic vagotomy or splanchnicectomy were determined. We found that CCK-8 activated contractile and myoelectric responses in the absence of vomiting, which were similar in most respects to those found in association with vomiting. These responses included 1) the retrograde giant contraction (RGC) and 2) the post-RGC phasic contractions. These RGCs were similar with respect to their activation in an all-or-none fashion, magnitude, duration, and position in the small intestine. The myoelectric correlates of these motor responses were similar qualitatively and quantitatively. The responses activated by APO and CCK-8 differed with respect to their coordination at different levels of the gastrointestinal tract. Whether activated by CCK-8 or APO, atropine blocked the RGC but not the post-RGC contractions. Domperidone blocked all responses to APO but not to CCK-8, and splanchnicectomy did not affect responses to either agent. Vagotomy blocked all gastrointestinal responses to APO but not to CCK-8. These results indicated that CCK-8 activates the gastrointestinal motor and myoelectric correlates of vomiting by a peripheral mechanism that does not include dopamine receptors.
Thyroxine effect on exocrine pancreatic development in rats
Authors: Lu R. B. , Chaichanwatanakul K. , Lin C. H. , Lebenthal E. , Lee P. C.
Published: December 2017

Thyroxine and glucocorticoids both play important roles in regulating the development of mammalian tissues. The mechanisms by which they modulate the developmental process is not fully understood. Furthermore, the interaction between the effects of two hormones on the pancreas has not been studied in detail. To investigate these issues, we studied the effect of thyroxine and/or corticosterone on the development of the exocrine pancreas in normal and adrenalectomized rats. Daily injection of thyroxine (0.1 micrograms/g body wt) to pups starting at day 5 of age resulted in precocious increases of exocrine enzymes in the pancreata of these pups. Hypothyroid pups, induced by propylthiouracil, exhibited suppression of development of their pancreatic exocrine enzymes. Replacement of thyroxine or corticosterone alleviated the suppression of exocrine enzyme development in these pups. Rat pups, who underwent adrenalectomy at 5 days of age, had undetectable plasma corticosterone and exhibited similar suppression of pancreatic enzyme development. Injection of thyroxine or corticosterone alone to adrenalectomized pups led to normal development of exocrine pancreatic enzymes. When both thyroxine and corticosterone were given together to adrenalectomized pups, their pancreatic enzyme levels were found to increase to values above those of pups treated with thyroxine or corticosterone alone. We conclude that thyroxine has both direct and indirect modulatory roles in the development of the rat exocrine pancreas. Normal development of the exocrine pancreas depends on both intact adrenal and thyroid function in the rat.
Acid-base effects on ileal sodium chloride absorption in vitro
Authors: Vaccarezza S. G. , Charney A. N.
Published: December 2017

Previous work from this laboratory has shown that in the intact animal, ileal sodium chloride absorption is responsive to alterations in systemic acid-base balance. In vitro studies were undertaken to determine the nature of the active transport process affected. Paired, unstripped ileal tissues from Sprague-Dawley rats were mounted in modified Ussing chambers, and unidirectional 22Na and 36Cl fluxes were measured under short-circuited conditions (Isc). Acid-base effects were examined by changing either bathing solution partial pressure of CO2 (PCO2) or HCO3 concentration or by the addition of HCl or NaOH to a non-HCO3 N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer. When pH was decreased from 7.6 to 7.1, net sodium absorption increased twofold regardless of the means by which pH was changed. This increase was primarily accounted for by an increase in mucosal-to-serosal flux. Net chloride absorption was affected in a similar way, but the increase in absorption was primarily accounted for by an increase in mucosal-to-serosal flux only in the HEPES buffer. These changes were accompanied by reductions in Isc and residual flux. When all groups were considered, mucosal-to-serosal Na (JNam----s) and net Na (JNanet) fluxes correlated strongly with bathing solution pH (r = 0.84 and 0.94, respectively, P less than 0.01). These data indicate that an active ileal sodium chloride absorptive process is specifically responsive to changes in bathing solution pH. In addition, pH may affect ileal electrogenic chloride, HCO3, and/or H secretion.
Intestinal capillary filtration in acute and chronic portal hypertension
Authors: Korthuis R. J. , Kinden D. A. , Brimer G. E. , Slattery K. A. , Stogsdill P. , Granger D. N.
Published: December 2017

The impact of acute and chronic portal hypertension on the dynamics of intestinal microvascular fluid exchange was examined in anesthetized, fasted, sham-operated control rats with normal portal pressures (CON), during acute elevations in portal pressure (APH) in control rats, and in rats in which chronic portal hypertension (CPH) was produced by calibrated stenosis of the portal vein 10 days prior to the experiments. Although intestinal blood flow and vascular resistance were not altered by APH in control rats, CPH was associated with an increased intestinal blood flow and reduced intestinal vascular resistance when compared with CON and APH. Intestinal capillary pressure and lymph flow were elevated in APH and CPH relative to control values. However, the increase in both variables was greater in CPH. The capillary filtration coefficient was elevated only in CPH. The transcapillary oncotic pressure gradient was not altered by APH or CPH. Interstitial fluid pressure was increased from -1.1 mmHg in CON to 3.9 mmHg during APH and to 5.0 mmHg in CPH. The results of this study indicate that chronic elevations in portal venous pressure produce larger increments in intestinal capillary pressure and filtration rate than do acute elevations in portal venous pressure of the same magnitude. However, the potential edemagenic effects of elevated capillary pressure in both acute and chronic portal hypertension are opposed by increases in lymph flow and interstitial fluid pressure.
Regulation of food intake and hepatic protein synthesis by recombinant-derived cytokines
Authors: Moldawer L. L. , Andersson C. , Gelin J. , Lundholm K. G.
Published: December 2017

During inflammation, activated monocytes and lymphocytes synthesize and release many soluble protein mediators, such as interleukin (IL) 1, tumor necrosis factor-alpha, and IL-2. It is presently unclear which cytokines, if any, contribute to the anorexia and hepatic protein changes frequently seen during inflammation. To evaluate their potential role, food intake and liver and plasma protein synthesis were determined in both endotoxin-sensitive C57Bl/6j mice and endotoxin-resistant C3H/HeJ mice given either crude secretory products of Staphylococcus albus-stimulated human blood monocytes or murine recombinant IL-1-alpha, human recombinant IL-1-alpha or -beta, human recombinant tumor necrosis factor-alpha, or human IL-2. When given intraperitoneally to healthy animals, 2,000 lymphocyte-activating factor U/day of secretory products of activated human blood monocytes or recombinant murine IL-1-alpha depressed spontaneous food intake by 42 and 53%, respectively. Human IL-1-alpha and -beta and human tumor necrosis factor-alpha produced smaller reductions in food intake. In contrast, human IL-2, when given in equimolar quantities, had no appreciable effect on food intake or body weight. Administration of crude secretory products of activated blood monocytes, recombinant IL-1, or tumor necrosis factor-alpha increased liver weight, protein, and RNA content. In addition, plasma protein synthesis was significantly increased, as were serum amyloid P concentrations. Administration of recombinant tumor necrosis factor-alpha resulted in IL-1 production by peritoneal adherent cells. However, IL-2 had no effect on any hepatic parameter.
Stimulation of acid secretion and phosphoinositol production by rat parietal cell muscarinic M2 receptors
Authors: Pfeiffer A. , Rochlitz H. , Herz A. , Paumgartner G.
Published: December 2017

The muscarinic receptor system involved in hydrogen ion production by enriched rat gastric parietal cells was investigated. Muscarinic receptor density determined by [N-methyl-3H]scopolamine binding was 8,100/cell. The receptor appeared to be of the M2 muscarinic receptor subtype, since it had a low affinity (Kd, 189 nM) for the M1 receptor antagonist pirenzepine compared with atropine (Kd, 0.74 nM). Receptor activation by carbachol rapidly augmented levels of polyphosphoinositides, indicating an activation of a phospholipase C. The dose-response relations for the increase in inositol phosphates closely paralleled the binding of carbachol to muscarinic receptors with a Km of 17 microM. The inositol phosphate response was antagonized by pirenzepine with a Ki of 177 nM. The stimulation of inositol phosphate levels by carbachol correlated well with the stimulation of [14C]aminopyrine uptake, determined as an index of acid secretion. The muscarinic agonists oxotremorine, pilocarpine, and bethanechol elicited partial increases in inositol phosphates at maximal drug concentrations, and these partial increases correlated with their ability to stimulate [14C]aminopyrine uptake. These data indicate that inositol polyphosphates may be a second messenger of M2 receptors stimulating acid secretion.
Motility of the pyloric sphincter studied by the inductograph method in conscious dogs
Authors: Ehrlein H. J.
Published: December 2017

The aim of the study is to evaluate the motility of the pyloric sphincter in conscious dogs by means of extraluminal transducers. For this purpose induction coils were chronically implanted in 12 dogs. After a meal the pylorus opened and closed in relation to the gastric waves. The mean changes in pyloric diameter were 5.4 +/- 1.0 mm. During phase I of the interdigestive state, the mean degree of pyloric opening was 39 +/- 18%. Gastric contractions occurring during phase II or phase III were accompanied with a marked increase in pyloric diameter; the degree of pyloric opening was 93 +/- 12%. Duodenal instillations of hydrochloric acid or oleic acid significantly diminished the pyloric diameter. Nutrients added to a viscous meal also diminished the pyloric opening significantly in comparison with an acaloric meal. Results suggest that the pyloric sphincter is involved in the control of gastric emptying. The inductograph is a useful technique to study pyloric activity without impediment of luminal flow in animals.
Changes in jejunal myoelectrical activity during exercise in fed untrained dogs
Authors: Kenney M. J. , Flatt A. , Summers R. W. , Brown C. K. , Gisolfi C. V.
Published: December 2017

Seven female dogs (15-20 kg) were instrumented with seven bipolar electrodes sutured at 3-cm intervals to the serosal surface of the proximal jejunum and were exercised at different intensities and durations on a motor-driven treadmill. Slow-wave frequency increased (P less than 0.05) from preexercise control during prolonged (90 min) exercise and during recovery after short-term exercise (30 min) at 70% heart rate reserve (HRR). These changes were associated with an increase in core temperature. Spike-burst frequency (SBF) increased (P less than 0.05) with moderate exercise (50% HRR), but the magnitude was small. When exercise was extended beyond 30 min and during all recovery periods, SBF decreased significantly. Exercise produced migrating myoelectrical complexes in three experiments and less dramatic pattern changes characterized as "clustered contractions" (regular spike bursts preceded and followed by the absence of spike bursts) in at least nine other experiments. We conclude that exercise does alter jejunal myoelectrical activity, but myoelectrical patterns may be more important in explaining exercise-induced gastrointestinal symptoms than changes in spike-burst frequency or duration.
Dissociation of fluid secretion and energy supply in rat mandibular gland by high dose of ACh
Authors: Murakami M. , Seo Y. , Watari H.
Published: December 2017

The effects of a high dose of acetylcholine (ACh) on oxygen consumption (VO2) and changes in phosphorus energy metabolites during secretion were studied in isolated perfused mandibular gland of rats at 24 degrees C. Sugar phosphates (SP), Pi, phosphocreatine (PCr), and ATP were identified by phosphorus-31 nuclear magnetic resonance spectroscopy. One micromole ACh induced a tachyphylactic secretory response, a persistently elevated VO2, and decreased PCr and ATP; 1 mM ACh caused an initial burst of secretion that was followed by suppression of secretion and a rapid increase in the VO2 to the same level as that with 1 microM ACh. These findings indicate a dissociation between secretion and VO2. During stimulation with 1 mM ACh, the level of PCr first decreased and then partially recovered, but the level of ATP continued to decrease and the levels of Pi and SP increased markedly. These findings suggest compartmentalization of creatine phosphokinase (CPK) systems and the possibility that a high concentration of ACh interferes with the transport of PCr between one CPK system near adenosinetriphosphatase and another system near mitochondria in acinar cells.
Effects of cholecystokinin octapeptide on contractile motility of guinea pig common bile duct
Authors: Takahashi T. , Kusunoki M. , Kantoh M. , Yamamura T. , Utsunomiya J.
Published: December 2017

Cholecystokinin octapeptide (CCK-8)-induced contraction and [3H]acetylcholine ([3H]-ACh) release from the longitudinal muscle strip of the guinea pig common bile duct were studied by a standard organ bath method and superfusion system. CCK-8 (10(-7) M) caused a biphasic contraction, a rapid phasic contraction followed by a fading tonic contraction. Hexamethonium, propranolol, and phentolamine had no effects on CCK-8-evoked contraction. Atropine or tetrodotoxin significantly reduced CCK-8-evoked initial phasic contraction and produced a rightward shift of the dose-response curve for CCK-8 (10(-10)-3 x 10(-7) M). CCK-8 provoked a significant [3H]ACh release in a dose-dependent manner, which was almost completely abolished by tetrodotoxin or Ca2+-free medium. These results suggest that CCK-8 receptors are present not only on the smooth muscle cells but also on the intramural cholinergic nerve cell bodies of the guinea pig common bile duct.
Gastric H+-K+-ATPase in situ: relation to secretory state
Authors: Hersey S. J. , Steiner L. , Matheravidathu S. , Sachs G.
Published: December 2017

Isolated gastric glands from rabbit were used to measure the gastric H+-K+-adenosinetriphosphatase (ATPase) and its partial reaction, a K+ p-nitrophenyl phosphatase (pNPPase), in situ. Measurement of the enzyme activities required permeabilization of the cells with digitonin and the use of several ATPase inhibitors to reduce nonspecific activity. The enzyme activities were identified as the H+-K+-ATPase according to the following criteria: dependence on K+, association with parietal cells, insensitivity to ouabain and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and inhibition by the specific inhibitors omeprazole and Sch 28080. K+-stimulated ATPase, but not K+-pNPPase, was enhanced by K+ ionophores, valinomycin and nigericin, with nigericin resulting in the greatest activity. Comparison of tissues that were preincubated to establish resting and stimulated states showed that prestimulation results in an increase in K+-stimulated ATPase activity with no change in the total activity. With the use of a two-step assay procedure, it could be shown that stimulation also results in an increase in the omeprazole-sensitive maximal ATPase activity. These results indicate that the major effects of stimulation are to enhance KCl activation of the enzyme and to increase the number of active enzyme molecules.
Effects of intraluminal nutrients on intestinal myoelectric activity in rabbits
Authors: Bouyssou T. , Pairet M. , Candau M. , Ruckebusch Y.
Published: December 2017

In the unanesthetized rabbit, intraluminal infusions of D- and L-methionine, L-tryptophan, D-glucose, D-xylose, and lactulose had a biphasic effect on small intestinal myoelectric activity. A phase of enhanced activity was followed by a phase of inhibition. The excitatory phase was mimicked by saline solutions equiosmolar to the test solutions. The subsequent inhibition was does dependent and significantly (P less than 0.01) longer for the passively absorbed D-methionine than for the L-stereoisomer. The inhibitory action of 10 mM D-glucose, 10 mM L-methionine, and 5 mM L-tryptophan was blocked by propranolol on the jejunum and by phenoxybenzamine on the ileum. We conclude that the initial excitatory phase induced by luminal amino acids and sugars may be dependent on an action on osmoreceptors, whereas the subsequent inhibitory phase may involve the sympathetic noradrenergic system.
Immunoneutralization of somatostatin and neurotensin: effect on gastric acid secretion
Authors: Seal A. , Liu E. , Buchan A. , Brown J.
Published: December 2017

Cell lines producing monoclonal antibodies to somatostatin and neurotensin, designated S-10 and NT-C5, respectively, have recently been generated. The purpose of the present immunoneutralization study in urethan-anesthetized gastric fistula rats is 1) to examine the ability of these antibodies to block the inhibitory effect of their target peptides on meal-stimulated gastric acid secretion and 2) to use these antibodies as probes to determine whether somatostatin and/or neurotensin are involved in the inhibition of gastric acid secretion produced by intraduodenal, intra-ileal, and intracolonic fat infusions. The results demonstrate that both S-10 and NT-C5 successfully bound exogenous somatostatin and neurotensin in vivo. S-10 but not NT-C5 prevented the inhibition of gastric acid secretion produced by intraduodenal fat. NT-C5 but not S-10 prevented the inhibition of gastric acid secretion produced by intra-ileal fat. Neither S-10 nor NT-C5 prevented the inhibition of gastric acid secretion produced by intracolonic fat. We conclude that somatostatin is associated with proximal and neurotensin with distal small bowel intestinal fat-induced inhibition of gastric acid secretion.
Synaptic behavior of myenteric neurons in guinea pig distal colon
Authors: Wade P. R. , Wood J. D.
Published: December 2017

Intracellular recording methods were used in vitro to analyze the synaptic behavior of neurons in myenteric ganglia of guinea pig distal colon. Fast excitatory postsynaptic potentials (EPSPs) were observed in a variety of types of colonic neurons. Both spontaneous and stimulus-evoked EPSPs were abolished or suppressed by addition of hexamethonium, tetrodotoxin, or elevation of Mg2+ and reduction of Ca2+ in the bathing medium. Individual neurons usually received inputs from several fiber tracts and multiple EPSPs were sometimes evoked by electrical stimulation of single-fiber tracts. Stimulus-evoked fast EPSPs were always of greater amplitude, longer duration, and longer decay time than were spontaneous fast EPSPs in the same neurons. No rundown of the fast EPSPs occurred during prolonged stimulation at frequencies up to 10 Hz. Repetitive stimulation evoked slow depolarizing potentials (slow EPSPs) in 25% of the neurons. Characteristics of the slow EPSPs were 1) slow rise times, 2) duration in the seconds time domain, 3) enhanced excitability, 4) increased input resistance, and 5) reduction of hyperpolarizing after-potentials. In general, the variety of synaptic potentials and the properties of the events were the same as found in myenteric neurons of the guinea pig small bowel. Compared with synaptic behavior of small intestinal myenteric neurons, the notable differences were absence of the rundown phenomenon for fast EPSPs in the colonic neurons and a greater incidence of spontaneously occurring fast EPSPs.
Effect of pH on chloride absorption in the flounder intestine
Authors: Charney A. N. , Scheide J. I. , Ingrassia P. M. , Zadunaisky J. A.
Published: December 2017

Chloride absorption in the small intestine of the winter flounder, Pseudopleuronectes americanus, is reported to be sensitive to ambient pH. We studied this sensitivity in isolated stripped intestinal mucosa mounted in modified Ussing chambers. Unidirectional 36Cl fluxes (JClm----s, JCls----m) were measured under short-circuited conditions in bathing solutions containing various combinations of HCO3- (0-20 mM), partial pressure of CO2 (0-36 mmHg), and pH (6.77-7.85). We found that JClm----s, net 36Cl flux (JClnet), and short-circuit current (Isc) increased and JCls----m decreased predominately in response to increases in bathing solution pH. There was a linear relationship between pH and both JClnet (r = 0.92, P less than 0.01) and Isc (r = 0.96, P less than 0.005) between pH 6.77 and 7.74. The pH effect was completely reversible, did not require either CO2 or HCO3-, and was not affected by the presence of mucosal barium at 1 mM. Mucosal bumetanide (0.1 mM) completely inhibited the pH effect. These data suggest that the process by which Cl- is absorbed in the flounder intestine is sensitive to pH. The data do not indicate whether pH affects Na+-K+-2Cl- cotransport or a Cl- transport pathway in series with this process. The direction of Cl- absorption in response to pH contrasts with inverse relation of pH and Cl- absorption in mammalian small intestine.
Local control of mesenteric blood flow by the renin-angiotensin system
Authors: Suvannapura A. , Levens N. R.
Published: December 2017

The purpose of this study is to determine whether locally acting angiotensin II (ANG II) plays a direct role in the control of mesenteric blood flow after volume depletion in the anesthetized dog. Infusion of the ANG II receptor antagonist saralasin into the mesenteric artery at doses between 0.05 and 0.1 microgram.kg-1.min-1 attenuated the reduction in renal blood flow produced by intrarenal injection of ANG II. In contrast, infusion of saralasin at 0.01 microgram.kg-1.min-1 did not affect the change in renal blood flow produced by ANG II, indicating that at this dosage the antagonist did not leave the mesenteric circulation in pharmacologically significant quantities. ANG II produced a dose-dependent decrease in splanchnic blood flow when injected into the mesenteric artery. Simultaneous infusion of 0.01 microgram.kg-1.min-1 saralasin into the mesenteric artery blocked the action of up to 1 ng ANG II by 80%. Infusion of saralasin at 0.01 microgram.kg-1.min-1 into the mesenteric artery of hemorrhaged animals increased mesenteric blood flow without significantly affecting renal blood flow, blood pressure, or plasma renin activity. These data demonstrate that saralasin can be localized to the mesenteric circulation at a dose capable of inhibiting angiotensin action and that endogenous ANG II plays a direct, physiologically important local role in controlling splanchnic resistance after volume depletion.
Inhibitory opioid receptors in canine pylorus
Authors: Allescher H. D. , Ahmad S. , Daniel E. E. , Dent J. , Kostolanska F. , Fox J. E.
Published: December 2017

In 18 anesthetized dogs, antroduodenal and pyloric motility was monitored in vivo by a sleeve and perfused side-hole manometric assembly and by antral and duodenal serosal strain gauges. Close intra-arterial injection to the pylorus of dynorphin-(1-13) (Dyn) for kappa-receptors, [D-Pen2,5]enkephalin (DPen2,5-Enk) for delta-receptors, and [N-Me-Phe3-D-Pro4]morphiceptin (PL017) and [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAGO) for mu-receptors showed no excitatory effect in the pylorus. When pyloric motor activity was increased by duodenal field stimulation 3-5 cm aboaad from the pylorus, Dyn greater than DPen2,5-Enk greater than DAGO produced a dose-dependent inhibition of the pyloric motor activity. Naloxone (200 micrograms/kg iv and 20 micrograms ia) had no effect on the pyloric excitation due to duodenal field stimulation, but it reduced the inhibitory response of intra-arterially injected opioids. In addition, opioid binding ([3H]diprenorphine) in microsomal and mitochondrial fractions from the inner circular muscle ring of the pylorus showed a distribution similar to the neuronal marker [3H]saxitoxin but no correlation to the plasma membrane marker 5'-nucleotidase. These results suggest the existence of inhibitory opioid receptors (kappa- and delta-receptors) on excitatory neurons in the intestinal neuronal pathway, which activates the canine pylorus.
Role of terminal fucose residues in clearance of human glycosylated alpha-amylase
Authors: Tollefsen S. E. , Rosenblum J. L.
Published: December 2017

Human glycosylated alpha-amylase contains a single biantennary N-linked oligosaccharide that terminates with the structure Fuc alpha 1,3(Gal beta 1,4)GlcNAc. To examine the role of terminal fucose in the clearance of alpha-amylase, we used lectin affinity chromatography to isolate an alpha-amylase fraction that contains two terminal fucoses (one in each branch of the oligosaccharide) and a fraction from which both terminal fucoses have been enzymatically removed. In the rat, the rate of clearance of the radioiodinated fraction with terminal fucoses is rapid (t1/2 = 12 min) and is slowed by mannosylated but not galactosylated bovine serum albumin. The rate of clearance of the radioiodinated alpha-amylase fraction with no terminal fucoses is also rapid (t1/2 = 9.5 min), but the clearance is now slowed by galactosylated bovine serum albumin. These findings indicate that the fucosylated and defucosylated alpha-amylase fractions are recognized by different carbohydrate-specific receptors. We conclude therefore that terminal fucose is the recognition marker that effects the physiological clearance of this glycoprotein.
Characteristics of canine lower esophageal sphincter: a new electrophysiological tool
Authors: Allescher H. D. , Berezin I. , Jury J. , Daniel E. E.
Published: December 2017

The canine lower esophageal sphincter (LES) was evaluated as a model for investigation of the electrophysiology of nonadrenergic noncholinergic neurotransmission. The LES contained a dense collection of gap junctions and a moderate number of nerves located at the periphery of muscle bundles, which are often associated with interstitial cells of Cajal. These cells make gap junctions with one another and with smooth muscle cells. The nerve varicosities contained many large dense cored vesicles. In vitro the LES produced spontaneous active tone and relaxed to field stimulation that was blocked by tetrodotoxin (TTX). Increase of stimulus duration or frequency produced a partially TTX-insensitive sphincter relaxation. Basal tone and nerve-mediated relaxation were unaffected by cholinergic, histaminergic, or adrenergic antagonists. Acetylcholine, carbachol, or histamine caused TTX-insensitive contractions mediated by M2- and H1-receptors, respectively. Vasoactive intestinal peptide (10(-6) M) and isoproterenol (10(-6) M) relaxed the LES to the same extent as field stimulation. In the double sucrose gap this tissue regularly produced inhibitory junction potentials when field stimulated. The canine LES has appropriate morphological and pharmacological properties for the electrophysiological study of nonadrenergic noncholinergic neural responses, their mechanisms, and mediators.
Quantitative measurement of feline colonic transit
Authors: Krevsky B. , Somers M. B. , Maurer A. H. , Malmud L. S. , Knight L. C. , Fisher R. S.
Published: December 2017

Colonic transit scintigraphy, a method for quantitatively evaluating the movement of the fecal stream in vivo, was employed to evaluate colonic transit in the cat. Scintigraphy was performed in duplicate in five cats and repeated four times in one cat. After instillation of an 111In marker into the cecum through a surgically implanted silicone cecostomy tube, colonic movement of the instillate was quantitated for 24 h using gamma scintigraphy. Antegrade and retrograde motion of radionuclide was observed. The cecum and ascending colon emptied rapidly, with a half-emptying time of 1.68 +/- 0.56 h (mean +/- SE). After 24 h, 25.1 +/- 5.2% of the activity remained in the transverse colon. The progression of the geometric center was initially rapid, followed later by a delayed phase. Geometric center reproducibility was found to be high when analyzed using simple linear regression (slope = 0.92; r = 0.73; P less than 0.01). Atropine (0.1 mg/kg im) was found to delay cecum and ascending colon emptying and delay progression of the geometric center. These results demonstrate both 1) the ability of colonic transit scintigraphy to detect changes in transit induced by pharmacological manipulation and 2) the fact that muscarinic blockade inhibits antegrade transit of the fecal stream. We conclude that feline colonic transit may be studied in a quantitative and reproducible manner with colonic transit scintigraphy.
Hepatic efflux of glutathione by the perfused rat liver: role of membrane potential difference
Authors: Wright T. L. , Fitz J. G. , Boyer T. D.
Published: December 2017

Glutathione (GSH) is released into hepatic sinusoids by a carrier-mediated process. The importance of transmembrane potential difference (PD) as a driving force for hepatic efflux of GSH from isolated perfused rat liver was investigated. The membrane PD was measured using intracellular microelectrodes as PD was altered over the physiological range by ion substitution in the perfusate. The effect of a change in membrane PD on the rate of efflux of GSH into the perfusate was determined. Because GSH carries a net negative charge at physiological values of pH, we predicted that hyperpolarization of cells would increase efflux, whereas depolarization would decrease efflux. Three different manipulations were used to depolarize the hepatocyte membrane to a similar degree, and variable effects on GSH efflux were observed. Substitution of Cl with gluconate in the perfusate depolarized the hepatocyte but had no effect on GSH efflux, whereas substitution of Na with choline in the perfusate increased GSH efflux to 110% of basal values. Perfusion with K+ inhibited GSH efflux by 21%. The latter two manipulations were associated with evidence of hepatic injury. Hyperpolarization of the hepatocyte also had variable effects on GSH efflux. Substitution of Cl with nitrate in the perfusate transiently increased the membrane PD and decreased GSH efflux, whereas perfusion with glucagon caused a sustained increase in membrane PD but did not alter GSH efflux rates. None of the latter manipulations was associated with hepatic injury and thus no consistent relationship between membrane PD and sinusoidal efflux of GSH was demonstrated. We conclude that in the isolated perfused rat liver, efflux of GSH is not driven directly by membrane PD.
Role of Ca2+ in bombesin-stimulated release of gastrin and somatostatin from isolated perfused rat stomach
Authors: Guo Y. S. , Thompson J. C. , Singh P.
Published: December 2017

The role of calcium (Ca2+) in bombesin (BBS)-stimulated release of gastrin and somatostatin-like immunoreactivity (SLI) was examined in isolated perfused rat stomachs obtained from male rats fasted overnight. The stomachs were perfused via the celiac artery. BBS (1 nM) was perfused alone for 10 min or in combination with various Ca2+ antagonists, including 1) different doses of divalent cationic Ca2+ chelator (EGTA), 2) Ca2+ channel blockers (nifedipine, verapamil), and 3) calmodulin (Ca2+ binding protein) antagonist [trifluoperazine (TFP)]. The effluent was collected for measurement of gastrin and SLI. EGTA at doses of 2 or 5 mM blocked the BBS-mediated release of both gastrin and SLI. After removal of a low dose of EGTA from the perfusate, the release of both gastrin and SLI rebounded. On removal of a high dose of EGTA, however, SLI release remained depressed, but gastrin rebounded even more significantly. In the absence of BBS, the rebound of gastrin release was less dramatic, indicating that reexposure to Ca2+ partially contributed to the rebound phenomenon. Nifedipine (0.1-10 microM) markedly decreased BBS-stimulated release of gastrin and SLI in a dose-dependent fashion; the inhibitory effect of nifedipine on SLI release was significantly stronger than on gastrin release. Verapamil (10 microM) depressed BBS-induced SLI release but not gastrin release. TFP (50 or 100 microM) also resulted in inhibition of bombesin-elicited release of gastrin and SLI in a dose-related manner.(ABSTRACT TRUNCATED AT 250 WORDS)
Radiographic analysis of the effect of dietary fibers on rat colonic transit time
Authors: Lupton J. R. , Meacher M. M.
Published: December 2017

The effect of different fiber sources on colonic transit time was charted using serial radiographs. Sixty male Sprague-Dawley rats, 10 rats per group, were provided with either a fiber-free control diet or the control diet uniformly diluted to provide 8% dietary fiber from guar, pectin, cellulose, wheat bran, or oat bran. At surgery, radiopaque markers were inserted at defined distances in the mesentary closest to the large bowel. Three weeks postsurgery, the animals were intubated with 0.5 ml of a radiopaque marker, and radiographs were taken at 15-min intervals. Of the two poorly fermented fibers, cellulose was as slow as and wheat bran was faster than the fiber-free controls at five out of the six bowel segments measured. The fermentable fibers (pectin, guar, and oat bran) were fast through some bowel segments and slow through others. This study provides in vivo data on colonic transit time and shows that neither 24-h fecal weight nor total transit time is a good predictor of the rate of transit through particular gut segments.
Corelease of amidated and glycine-extended antral gastrins after a meal
Authors: Hilsted L. , Hansen C. P.
Published: December 2017

Glycine-extended gastrin, the immediate precursor of bioactive (i.e., carboxyamidated) gastrin, was recently identified in antral tissue and in peripheral blood. Studies on pituitary cell lines have shown that although only bioactive peptides are released along the regulated pathway, i.e., stored at high concentrations in secretory granules and released upon appropriate stimulation, the release of precursors is constitutive, i.e., secreted continuously without secretagogue stimulation. To determine whether the secretion of glycine-extended gastrin from the antral G-cell is regulated, meal-induced release was examined. In anesthetized pigs (n = 8) the antral veins were catheterized and blood was collected continuously before and after intragastric instillation of meat extract. Surgical biopsies of antral mucosa were obtained from six animals. Glycine-extended and amidated gastrins were measured and characterized by radioimmunoanalysis and chromatography. The results demonstrate that glycine-extended gastrin is released in a regulated manner from antral G-cells and furthermore the component pattern is identical in mucosa and blood.
Intestinal microvascular exchange during lipid absorption
Authors: Granger D. N. , Korthuis R. J. , Kvietys P. R. , Tso P.
Published: December 2017

The forces and membrane coefficients governing transcapillary and lymphatic fluid fluxes were measured in the cat jejunum before and during perfusion of the gut lumen with oleic acid (5 mM) solubilized with taurocholic acid (10 mM). Net transmucosal fluid flux, lymph flow, capillary pressure (Pc), blood flow, capillary filtration coefficient (Kf,c), and lymph and plasma oncotic pressures were measured under absorptive and nonabsorptive conditions. Interstitial fluid pressure was calculated for the two conditions from measured parameters. Stimulation of lipid absorption resulted in a fivefold increase in lymph flow, a threefold increase in Kf,c, a doubling of blood flow, a 2.5 mmHg increase in Pc, and a 1.0 mmHg reduction in interstitial (lymph) oncotic pressure. Lipid absorption was associated with a 3.6 mmHg increase in interstitial fluid pressure. During lipid absorption, approximately 35% of the absorbed fluid is removed from the mucosal interstitium by lymphatics while capillaries remove the remaining 65%. The results of this study indicate that the effects of lipid absorption on microvascular and lymphatic fluid dynamics are quantitatively different than those produced by glucose absorption. These differences can be largely explained by lipid absorption-induced increases in blood flow and microvascular permeability.
Internalization and cellular processing of cholecystokinin in rat pancreatic acinar cells
Authors: Izzo R. S. , Pellecchia C. , Praissman M.
Published: December 2017

To evaluate the internalization of cholecystokinin, monoiodinated imidoester of cholecystokinin octapeptide [125I-(IE)-CCK-8] was bound to dispersed pancreatic acinar cells, and surface-bound and internalized radioligand were differentiated by treating with an acidified glycine buffer. The amount of internalized radioligand was four- and sevenfold greater at 24 and 37 degrees C than at 4 degrees C between 5 and 60 min of association. Specific binding of radioligand to cell surface receptors was not significantly different at these temperatures. Chloroquine, a lysosomotropic agent that blocks intracellular proteolysis, significantly increased the amount of CCK-8 internalized by 18 and 16% at 30 and 60 min of binding, respectively, compared with control. Dithiothreitol (DTT), a sulfhydryl reducing agent, also augmented the amount of CCK-8 radioligand internalized by 25 and 29% at 30 and 60 min, respectively. The effect of chloroquine and DTT on the processing of internalized radioligand was also considered after an initial 60 min of binding of radioligand to acinar cells. After 180 min of processing, the amount of radioligand internalized was significantly greater in the presence of chloroquine compared with controls, whereas the amount of radioligand declined in acinar cells treated with DTT. Internalized and released radioactivity from acinar cells was rebound to pancreatic membrane homogenates to determine the amount of intact radioligand during intracellular processing. Chloroquine significantly increased the amount of intact 125I-(IE)-CCK-8 radioligand in released and internalized radioactivity while DTT increased the amount of intact radioligand only in internalized samples. This study shows that pancreatic acinar cells rapidly internalize large amounts of CCK-8 and that chloroquine and DTT inhibit intracellular degradation.
Reflex sympathetic activation in humans is accompanied by inhibition of gastric HCO3- secretion
Authors: Sjovall H. , Forssell H. , Haggendal J. , Olbe L.
Published: December 2017

The study was performed to determine whether the sympathetic nervous system contributes to the reflex control of gastric HCO3- secretion in humans. Gastric HCO3- secretion was registered by a computerized technique based on measurements of pH and PCO2 in gastric effluent. To minimize formation of CO2 in the stomach, subjects were pretreated with the H2-receptor blocker ranitidine. Compensations were made for HCO3- of nongastric origin. As indicators of cardiovascular sympathetic activity, we measured heart rate, forearm vascular resistance, and plasma catecholamine concentrations. In one series of experiments, peripheral sympathetic activity was enhanced by the application of a negative pressure around the lower part of the body (lower body negative pressure, LBNP), at a rate sufficient to induce a slight decrease in systemic arterial pressure. In another series of experiments, peripheral sympathetic activity was inhibited by elevation of the legs, a procedure that simulates volume loading by redistributing blood volume toward the central circulation. LBNP at -20 mmHg decreased systolic pressure and pulse pressure and significantly increased heart rate, forearm vascular resistance, and plasma catecholamine levels. All these effects were observed in the first 15-min period of LBNP and were well maintained throughout the 45-min observation period. LBNP also inhibited basal gastric HCO3- secretion rate in seven of eight individuals, but this response was slower in onset with a latency of at least 15 min. Elevation of the legs increased pulse pressure and decreased forearm vascular resistance. Catecholamines were not measured in these experiments. Gastric HCO3- secretion tended to increase, but the magnitude of the response was highly variable.(ABSTRACT TRUNCATED AT 250 WORDS)
Sex differences in membrane potential in the intact perfused rat liver
Authors: Weisiger R. A. , Fitz J. G.
Published: December 2017

The electrical potential difference across the plasma membrane was compared in paired livers from male and female rats perfused single-pass with Krebs-bicarbonate buffer. Variability in the membrane potential measured for different cells within the same liver was small (SD = 1.3 mV). The mean membrane potential was 5.1 mV more negative for male livers than for female livers (-30.3 +/- 0.6 vs. -25.2 +/- 1.0 mV, P less than 0.001), and the male liver had a more negative membrane potential than the female liver in all nine pairs studied. No correlation between membrane potential and perfusion rate was seen. Variability among female livers was more than twice as great (range -19.6 to -30.0 mV) as for male livers (range -26.7 to -31.9 mV). These results suggest that hepatic membrane potential may be modulated by sex hormone levels, which are more variable in female animals. Because the hepatic uptake of bile acids such as taurocholate and organic anions such as bilirubin may involve net movement of electrical charge across the plasma membrane, the current results may explain previously reported sex differences in the uptake of these and other electrogenically transported molecules.
Sites of action of protein kinase C on secretory activity in rat parietal cells
Authors: Hatt J. F. , Hanson P. J.
Published: December 2017

Sites at which the calcium-sensitive phospholipid-dependent protein kinase, protein kinase C, may influence acid secretion have been investigated in rat isolated parietal cells. In both crude and enriched preparations of parietal cells incubated in a medium containing 100 mM K+, the activators of protein kinase C, 12-O-tetradecanoylphorbol 13-acetate (TPA) and 1-oleoyl-2-acetyl-glycerol (OAG), produced a dose-dependent stimulation [half-maximally effective concentration (EC50) values of 1 nM and 70 microM, respectively] of aminopyrine accumulation, an index of the sequestration of acid in the cell. In a medium containing 4.5 mM K+, and with no added secretagogues, TPA and OAG did not affect aminopyrine accumulation. Histamine-stimulated aminopyrine accumulation was inhibited by TPA [half-maximally effective inhibitory concentration (IC50) of 2.9 nM]. TPA reduced the histamine-stimulation of the adenosine 3',5'-cyclic monophosphate (cAMP) content of parietal cells (47% inhibition at 100 nM TPA) but also inhibited aminopyrine accumulation at or distal to cAMP-dependent protein kinase. Activators of protein kinase C can produce multiple effects on secretory activity in the rat parietal cell.
Saturated fatty acid diet prevents radiation-associated decline in intestinal uptake
Authors: Thomson A. B. , Keelan M. , Lam T. , Cheeseman C. I. , Walker K. , Clandinin M. T.
Published: December 2017

Adult female Sprague-Dawley rats were fed isocaloric semipurified diets containing a high content of either polyunsaturated (P) or saturated (S) fatty acids; these diets were nutritionally adequate, providing for all known essential nutrient requirements. On day 3 after beginning S or P, one group of animals was exposed to a single 6-Gy dose of abdominal radiation, and the other half was sham irradiated. S or P diets were continued for a further 14 days. Brush-border membrane purification and sucrase-specific activities were unaffected by diet or by abdominal irradiation. In rats fed P, irradiation was associated with an increase in jejunal brush-border membrane total phospholipid and the ratio of phospholipid to cholesterol; these changes were not observed in animals fed S. In irradiated rats, ileal brush-border membrane phospholipid per cholesterol was high in animals fed S compared with P. In irradiated animals fed P, there was reduced jejunal and ileal uptake of several medium- and long-chain saturated and unsaturated fatty acids and cholesterol, and the ileal uptake of higher concentrations of glucose was reduced in irradiated animals fed P. In contrast, lipid uptake was similar in control and irradiated animals fed S except for cholesterol uptake, which was reduced. Ileal uptake of higher concentrations of glucose was increased in irradiated animals fed S. Quantitative autoradiography failed to demonstrate any change in the distribution of leucine or lysine transport sites along the villus 1 or 2 wk after abdominal irradiation or in response to feeding S or P. Also, these differences in transport achieved by feeding S to radiated animals were not explained by variations in the animals' food consumption or intestinal mucosal surface area. Thus the use of short-term feeding with a saturated fatty acid diet in the prevention of acute irradiation damage to the intestine warrants further investigation in humans.
Age and cortisone alter host responsiveness to cholera toxin in the developing gut
Authors: Chu S. H. , Ely I. G. , Walker W. A.
Published: December 2017

To assess the influence of immaturity on the responsiveness of enterocytes to specific pathogens, a dose-response curve for cholera toxin (CT)-induced fluid secretion was determined in the proximal small intestine of rats at 2 and 4 wk of age. The suckling rat was approximately 50 times more sensitive to CT in triggering the secretory response than the weaned rat, when estimated by the medium-effective dose (ED50, 0.8 vs. 38.9 nM). Cortisone, known to promote enterocyte maturation, when injected into suckling rats, decreased host sensitivity approximately 1,000 times. Neither age nor cortisone decreased the receptor binding of 125I-labeled CT to intestinal microvillus membranes. In contrast, cortisone treatment caused a threefold increase in receptor density from 14.5 to 43.0 pmol/mg protein. The enzyme responsible for the sodium pump, Na+-K+-ATPase, showed a threefold increase in activity both after weaning and after a cortisone treatment. These data indicate that the immature gut exhibited an increased host sensitivity to CT stimulation that was not correlated with initial receptor binding but was related to a lowered Na+-K+-ATPase activity, suggesting that an underdeveloped sodium pump may be partially responsible for the high incidence of secretory diarrhea in neonates.