bluuebunny/crossref_metadata_2025 huggingface dataset:
Arginine vasopressin metabolism in dogs. II. Modeling and system analysis.
Authors: Wilson K C , Weitzman R E , Fisher D A
Published: December 2017

System modeling and analysis methods were applied to interpret data regarding arginine vasopressin (AVP) metabolism in dogs. Based on this analysis a new nonlinear 3-pool model of AVP distribution and disposal was proposed and quantified; the model pools included the plasma, a receptor pool, and an extravascular nonreceptor pool. The receptor pool mediated a portion of the rapid flux of hormone between the plasma and the extravascular pool. Mathematical analysis indicated that the plasma AVP impulse response (bolus) data would be insufficient to uniquely estimate all the model constants, but additional plasma impulse data using 125I-labeled AVP, which does not bind to physiologic hormone receptors, would allow unique model quantification. Other required measurements were the urinary excretion of intact hormone, and plasma AVP degradation. The model was successfully fitted to the data from 10 dogs. The results suggest that, in the normal dogs studied, plasma contained 25% of the total AVP, 19% was bound to receptors, and the remaining 56% was in the extravascular pool. Eighty percent of the flux of AVP from the vascular compartment was mediated by the receptor pool; 98% of AVP degradation occurred in the extravascular pool; and urine excretion and plasma degradation made up the remainder.
Lactate metabolism in perfused rat lung.
Authors: Rhoades R A , Shaw M E , Eskew M L , Wali S
Published: December 2017

Glucose utilization and lactate metabolism were studied in isolated rat lungs perfused with a Krebs-Henseleit bicarbonate buffer, pH 7.4, containing either [U-14C]lactate, [U-14C]glucose, or [U-14C]alanine. Glucose uptake showed an apparent Km of 4.7 mM and a Vmax of 107 mumol-g dry wt-1-h-1. Lactate production under these conditions showed a Vmax of 82.9 mumol-g dry wt-1-h-1. At high circulating lactate level (7 mM), the perfused lung showed an increased capacity to utilize [U-14C]lactate with preferential incorporation into lung lipids. At equal molar concentration (5 mM) [U-14C]lactate was preferentially incorporated over [U-14C]glucose. Addition of 5 mM lactate to the perfusion medium did not affect lactate production. Perfused lungs from fasted rats showed higher lactate production, with increased amounts of [U-14C]alanine converted to lactate by the perfused lung, indicating lactate can also be derived from noncarbohydrate sources. These data show that under aerobic conditions the perfused lung can produce and utilize lactate simultaneously, and lactate can serve as a potential substrate for lung lipids.
Renal excretion of prostaglandins E2 and F2alpha in diabetes insipidus rats.
Authors: Dunn M J , Greely H P , Valtin H , Kintner L B , Beeuwkes R
Published: December 2017

On the assumption that the antagonism between prostaglandin E2 and vasopressin might represent a negative feedback system, we evaluated the hypothesis that vasopressin stimulates, in vivo, the renal production of prostaglandins. For these studies we used Brattleboro homozygous rats with diabetes insipidus and Long-Evans rats for controls, Brattleboro homozygotes show a substantial reduction in the renal excretion of prostaglandin E2 and prostaglandin F2alpha. Homozygotes excreted 39 +/- 5 ng/24 h prostaglandin E2 and 40 +/- 4 ng/24 h prostaglandin F2alpha, compared to 217 +/- 40 and 221 +/- 18 ng/24 h, respectively, in control rats (P less than 0.001). Therapy of homozygotes with vasopressin tannate in oil resulted in a prompt increase in the urinary excretion of prostaglandin E2 and prostaglandin F2alpha. 1-Desamino-D-arginine vasopressin, a nonpressor analogue of vasopressin, also enhanced the renal production of prostaglandin E2. We conclude that vasopressin (antidiuretic hormone) stimulates renal production and excretion of prostaglandin E2 and prostaglandin F2alpha in vivo. It is possible that this increment of prostaglandin synthesis serves a negative feedback function by modulating the action of vasopressin on the renal tubule.
Partial purification of dog angiotensinogen.
Authors: Morris B J , Moffat B , Reid I A
Published: December 2017

Dog angiotensinogen was purified 450-fold from the plasma of nephrectomized dogs by a simple four-step procedure involving precipitation between 1.5 and 2.3 M ammonium sulfate, gel filtration on Sephadex G-150, ion-exchange chromatography on DE-52 cellulose, and affinity chromatography on Concanavalin A-Sepharose. The purity of the final preparation was over 50%. The preparation of dog angiotensinogen had an apparent molecular weight of 80,000 determined by gel filtration on Sephadex G-100. Kinetic studies indicated that the Km of the reaction of dog renin with partially purified dog angiotensinogen (1,840 pmol/ml) was similar to that for the reaction with angiotensinogen in diluted dog plasma (1,820 pmol/ml). Thus the purification procedures employed did not alter the affinity of dog renin for the Leu10-Leu11 bond of dog angiotensinogen. Because the concentration of angiotensinogen in dog plasma is about 700 pmol/ml, a first order reaction with respect to substrate is indicated in vivo.
Effect of extracellular calcium on amylase release from dispersed pancreatic acini.
Authors: Gardner J D , Costenbader C L , Uhlemann E R
Published: December 2017

In dispersed acini prepared from guinea pig pancreas, removing extracellular calcium did not alter the basal rate of amylase release but reduced the stimulation of enzyme release caused by cholecystokinin, carbachol, secretin, and vasoactive intestinal peptide as well as that caused by derivatives of cyclic nucleotides. In acini incubated in a calcium-free, EGTA-containing medium the increase in amylase release caused by each secretagogue tested did not change during the initial 10 min of incubation, decreased by approximately 65% during the subsequent 40 min, and remained constant thereafter. Removing extracellular calcium did not alter the maximally effective concentrations of cholecystokinin or vasoactive intestinal peptide but abolished the decrease in stimulated enzyme secretion seen with supramaximal concentrations of cholecystokinin. Incubating pancreatic acini with cholecystokinin or carbachol plus secretin or vasoactive intestinal peptide caused potentiation of amylase release, and removing extracellular calcium reduced the stimulation of enzyme release caused by the two secretagogues in combination but did not alter their potentiating interactions.
LIF and CNTF, which share the gp130 transduction system, stimulate hepatic lipid metabolism in rats
Authors: Nonogaki K. , Pan X. M. , Moser A. H. , Shigenaga J. , Staprans I. , Sakamoto N. , Grunfeld C. , Feingold K. R.
Published: December 2017

We determined the effects of leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF) on lipid metabolism in intact rats. Administration of LIF and CNTF increased serum triglycerides in a dose-dependent manner with peak values at 2 h. The effects of LIF and CNTF on serum cholesterol were very small, and serum glucose was unaffected. Both LIF and CNTF stimulated hepatic triglyceride secretion, hepatic de novo fatty acid synthesis, and lipolysis. Pretreatment with phenylisopropyl adenosine, which inhibits lipolysis, partially inhibited LIF- and CNTF-induced hypertriglyceridemia. Interleukin-4, which inhibits cytokine-induced hepatic fatty acid synthesis, also partially inhibited LIF- and CNTF-induced hypertriglyceridemia. These results indicate that both lipolysis and de novo fatty acid synthesis play a role in providing fatty acids for the increase in hepatic triglyceride secretion. Neither indomethacin nor adrenergic receptor antagonists affected the hypertriglyceridemia. The combination of LIF plus CNTF showed no additive effects consistent with the action of both cytokines through the gp130 transduction system. Thus LIF and CNTF have similar effects on lipid metabolism; they join a growing list of cytokines that stimulate hepatic triglyceride secretion and may mediate the changes in lipid metabolism that accompany the acute phase response.
Fetal bile salt metabolism: placental transfer of dihydroxy bile salts in sheep
Authors: Sewell R. B. , Hardy K. J. , Smallwood R. A. , Hoffman N. E.
Published: December 2017

The bidirectional placental transfer of sodium [11,12-di-3H]chenodeoxycholate and sodium [14C]deoxycholate was studied in conscious pregnant sheep near term. In fetal-to-maternal studies, radiolabeled bile salt was injected into the fetal portal vein, and the daily excretion of radiolabel in maternal hepatic bile was measured over 3-4 days. In maternal-to-fetal studies, the mother received daily injections of radiolabeled bile salt, and the accumulation of label in the fetal pool was measured after 6-9 days. Bile salts were transferred predominantly as the taurine conjugate. Transfer rates were 1) fetus to mother; chenodeoxycholate, 6.7 mumol/24 h and deoxycholate, less than 0.5 mumol/24 h and deoxycholate, 1.4 mumol/24 h. We conclude that, in sheep near term, deoxycholate derived from the mother slowly accumulates in the fetus, while the placenta acts as an excretory route for fetal chenodeoxycholate.
Somatostatin-14 and -28: clearance and potency on gastric function in dogs
Authors: Seal A. , Yamada T. , Debas H. , Hollinshead J. , Osadchey B. , Aponte G. , Walsh J.
Published: December 2017

To examine the significance of somatostatin-14 (S-14) and somatostatin-28 (S-28) in gastric physiology, we compared their relative potencies on acid secretion in the dog. On a molar infusion basis, S-14 and S-28 appeared to be equipotent, causing 50% inhibition of peptone meal-stimulated acid secretion at a dose of 400 pmol . kg-1 . h-1. However, comparison of the plasma half lives (t 1/2) of the two peptides revealed that S-28 disappeared at a much slower rate (t 1/2 = 2.84 +/- 0.15 min, mean +/- SE, n = 7) than S-14 (t 1/2 = 0.57 +/- 0.06 min). When acid-inhibitory effect was compared against increment in plasma concentrations produced by peptide infusion, S-14 was roughly 10-fold more potent than S-28. No alteration of gastrin response to peptone was observed at a dose of S-14 or S-28 that completely abolished acid secretion, suggesting that regulation of acid secretion is not mediated by gastrin inhibition. Thus, S-14 is a potent and possibly important physiological inhibitor of gastric acid secretion. Although circulating S-28 may have importance in regulation of some biological functions, it appears to play a less prominent role in regulation of gastric secretion.
Immunological regulation of epithelial function
Authors: Castro G. A.
Published: December 2017

The objective of this presentation is to develop a hypothesis through a survey of pertinent literature rather than to review an established area of physiology. The focal point is the mucosa of the small intestine. The major thesis is that lamina propria cells regulate functions of epithelial cells. Support for this comes from studies of the "immunophysiological" interplay that goes on in the mucosa and that has been amply revealed through investigations of host-parasite interactions. Immunological reactions in several intestinal helminth infections affect epithelial cell differentiation and development as well as secretory, absorptive, and digestive activities. Epithelial cells may be influenced indirectly as bystander cells during immunologically mediated inflammation or directly through their recruitment as effector components in immune reactions. Immune responses, by convention, are thought to be mediated by nonepithelial cells. Therefore, involvement of epithelial cells in effecting immunity or in responding to immunologically elicited signals implies a regulatory role for lamina propria cells in epithelial function. Confirmation of the capacity of epithelial cells to respond to the command of other cells with "memory" capabilities would imply the existence of a sensitive, locally organized, and highly specific adaptive mechanism in the host.
Metallothionein mRNA induction in mouse small bowel by oral cadmium and zinc
Authors: Ouellette A. J. , Aviles L. , Burnweit C. A. , Frederick D. , Malt R. A.
Published: December 2017

Induction of metallothionein mRNA was investigated in organs of mice receiving oral zinc and cadmium. The low molecular weight, heat stability, and 30% cysteine content of metallothionein facilitated its detection in cell-free translation products analyzed by Sephadex G-50 chromatography and by gel electrophoresis. Native and heat-denatured [35S]cysteine-labeled polypeptides directed by poly(A)+ mRNA from organs of mice exposed orally to 3 mg CdCl2 or 15 mg ZnCl2 were compared with those of control mice. Although parenteral administration of CdCl2 (30 micrograms) did not elicit a measurable metallothionein mRNA accumulation in gut, oral administration of this metal induced intestinal metallothionein mRNA to high levels; translatable metallothionein mRNA was not detected in control organs. Five hours after oral CD or Zn, metallothionein constituted 12-17% of [35S]cysteine directed into protein by gut mRNA, and metallothionein mRNA was induced to similar levels in liver, kidney, and spleen of the same mice. After oral Zn, metallothionein mRNA levels in proximal jejunum were twice those in other regions of intestine. Metallothionein mRNA accumulates rapidly in small bowel after oral Zn and Cd; simultaneous induction in other mouse organs indicates a systemic response.
Effects of high-fat diet on glucose metabolism in isolated pancreatic acini of rats
Authors: Bazin R. , Lavau M.
Published: December 2017

The purpose of the present study was to document the metabolism of glucose and its responsiveness to insulin in isolated pancreatic acini from rats fed either a low- or high-fat diet. The different steps investigated were labeled glucose oxidation, lactate production, hexokinase activity, and glucose transport, which was assessed by using both 3-O-methylglucose and 2-deoxyglucose. The acinar capacity to metabolize glucose (sum of CO2 plus lactate) was decreased by 50% by feeding the rats a high-fat diet. The impairment of glucose metabolism could not be explained by a defect in the glucose phosphorylation step because hexokinase activity was not changed in isolated acini from rats fed a high-fat diet. The effect of a high-fat diet was entirely accounted for by a reduction in the glucose transport rate that was achieved through a decrease in glucose transport Vmax with no change in Km. We could not detect any effect of insulin on glucose metabolism or 2-deoxyglucose uptake, whatever the diet composition. This work establishes that a high-fat diet, known to markedly alter pancreatic exocrine enzymes, also induces a large decrease in acinar glycolytic flux, raising the question of the relation between these two sets of adaptive changes.
Autoregulation of intestinal capillary filtration rate
Authors: Granger D. N. , Mortillaro N. A. , Perry M. A. , Kvietys P. R.
Published: December 2017

To determine whether intestinal capillary filtration rate, capillary pressure, or both are autoregulated in the cat ileum, the following parameters were measured under isovolumetric conditions: lymph flow, capillary pressure, capillary filtration coefficient, and lymph and plasma oncotic pressures. Superior mesenteric arterial pressure was reduced in 25-mmHg steps from 125 to 25 mmHg. As arterial pressure was reduced, lymph flow, capillary pressure, and the transcapillary oncotic pressure gradient decreased while the capillary filtration coefficient increased. Over the arterial pressure range of 75-125 mmHg, capillary pressure decreased in a fashion expected from a rigid system; however, capillary pressure was slightly autoregulated at lower arterial pressures. Lymph flow fell proportionately more than capillary pressure over the entire arterial pressure range. The results of this study indicate that intestinal capillary pressure and capillary filtration rate are poorly autoregulated in the cat when arterial pressure is reduced. Changes in interstitial fluid pressure play a major role in preventing interstitial dehydration in the cat ileum when arterial pressure is reduced.
A new method for estimating intestinal capillary pressure
Authors: Granger D. N. , Perry M. A. , Kvietys P. R. , Taylor A. E.
Published: December 2017

The purpose of this study was to compare the venous occlusion method for measuring capillary pressure with the stop-flow isovolumetric method in the cat small intestine. Venous occlusion pressures were determined from the inflection point of the venous pressure tracing after sudden occlusion of the venous outflow cannula. Venous occlusion pressure was highly correlated (r = 0.98, P less than 0.01) with stop-flow capillary pressure. This finding indicates that the major sites of fluid filtration and vascular capacitance reside at the same segment of the intestinal microcirculation. The venous occlusion method is a relatively simple technique for measuring whole-organ capillary pressure that is not constrained by the technical difficulties associated with volumetric/gravimetric techniques.
Scanning electron microscopy of the stomach during modifications of acid secretion
Authors: Wood L. R. , Dubois A.
Published: December 2017

Acute stimulation of gastric acid secretion as well as intragastric instillation of physiological concentrations and volumes of HCl caused marked changes in the appearance of surface epithelial cells of the stomach. These changes could represent a damage of the gastric surface epithelial cells of the stomach. Pretreatment with the histamine H2-receptor-blocking drug cimetidine tended to reduce this damage, although the difference was not significant. In contrast, it was completely abolished by an analogue of prostaglandin E2. These observations suggest that gastric epithelial cells may be damaged under physiological conditions and that quick repair is needed to prevent ulceration of the gastric mucosa. Alternatively, endogenous release of prostaglandin under certain undefined conditions could prevent this damage.
Effects of in vivo cholinergic stimulation of rat exocrine pancreas
Authors: Adler G. , Gerhards G. , Schick J. , Rohr G. , Kern H. F.
Published: December 2017

Peptide and cholinergic secretagogues both produce biphasic dose-response curves for pancreatic enzyme secretion in vitro: supraoptimal doses result in submaximal secretory responses. We compared the effects of maximal and supramaximal doses of a cholinergic agent (carbachol) on rat exocrine pancreas in vivo. In conscious rats, volume and enzyme output were measured from the cannulated pancreatic duct during infusion of carbachol for 3 h. Infusion of 5 X 10(-7) mol . kg-1 . h-1 carbachol caused optimal stimulation, whereas a supraoptimal dose (5 X 10(-6) mol . kg-1 . h-1) resulted in submaximal response. Similar results were achieved when discharge of amylase and protein synthesis was determined in vitro after carbachol in vivo. Supraoptimal doses of carbachol increased serum amylase and enhanced acinar cell lysosomal activity in the Golgi area. The latter appeared to induce fusion of zymogen granules, which resulted in cytoplasmic vacuoles. The in vivo results corroborate in vitro findings of a biphasic dose-response relationship for carbachol and demonstrate destructive effects of supraoptimal concentrations on target cells.
Intestinal absorption of glandular kallikrein in the rat
Authors: Overlack A. , Scicli A. G. , Carretero O. A.
Published: December 2017

We studied the possibility of intestinal absorption of glandular kallikrein in unanesthetized rats after administration of 5 mg of active or phenylmethylsulfonyl fluoride-inactivated pig pancreatic kallikrein (PPK). Immunoreactive PPK was measured in plasma and urine by radioimmunoassay using an antiserum to PPK that does not cross-react with rat glandular kallikrein. In addition, we studied the effect of intestinally administered active PPK on the intestinal blood flow distribution. Although immunoreactive PPK could not be detected (less than 10 ng/ml) in plasma after active PPK was administered, very small amounts were found in urine (20–40 ng/3 h). In the urine most of the PPK was in active form because over 75% could be bound to aprotinin-Sepharose. After inactive PPK was administered, immunoreactive PPK was detectable in the plasma of all rats, and urinary excretion was higher than after administration of active PPK. Blood flow distribution to the small intestine as a percentage of cardiac output was significantly greater 30 min after intestinal application of active PPK (5 mg) than after administration of the vehicle alone (1 ml of 0.9% saline). These results suggest that active and inactive PPK is absorbed from the gut in very small amounts. The finding of higher amounts of immunoreactive PPK in plasma and urine after inactive PPK was administered is probably due to the fact that the inactive form of the enzyme is not bound by the plasma inhibitors. These small amounts of kallikrein absorbed appear to have some effect on intestinal blood flow distribution.
Altered jejunal macromolecular barrier induced by alpha-dihydroxy deconjugated bile salts
Authors: Teichberg S. , McGarvey E. , Bayne M. A. , Lifshitz F.
Published: December 2017

The effect of deconjugated bile salt hydroxy group position and numbers on the ability of these agents to alter the normal lumen-to-blood jejunal barrier to intact protein penetration was analyzed. Only in vivo jejunal perfusion with 0.5 mM alpha-dihydroxy deconjugated bile salts chenodeoxycholate and deoxycholate led to increased penetration of the 40,000-molecular-weight protein horseradish peroxidase (HRP). This increased absorption of HRP with 0.5 mM chenodeoxycholate and deoxycholate was detectable biochemically, as well as by light and electron microscopic cytochemistry, and occurred in the absence of demonstrable histological or ultrastructural damage to the epithelium. Conjugation of chenodeoxycholate with glycine, epimerization of chenodeoxycholate from 7 alpha-hydroxy to 7 beta-hydroxy as in ursodeoxycholate, or addition of a third hydroxyl group as in cholate all eliminated the increase in jejunal HRP penetration and led to HRP absorption levels like those in bile salt-free preparations. The effect of chenodeoxycholate and deoxycholate on HRP absorption was paralleled by their production of net jejunal water secretion. The observations suggest that the naturally occurring alpha-dihydroxy bile salts may lead to an increase in intact antigen or toxin absorption during bacterial stasis syndromes.
Differential transit of liquids and solid residue through the human ileum
Authors: Kerlin P. , Phillips S.
Published: December 2017

We determined transit of liquids and the solid residue of a mixed meal through the ileocecal region of six healthy men. A multilumen polyvinyl tube was passed from above into a 20-cm segment of terminal ileum, and flow of liquid was assessed by indicator dilution techniques. Three test meals were eaten in random order at 5-hourly intervals. Meal A contained baked beans and polyethylene glycol (PEG 4000). Recovery of PEG 4000 from the ileum served to mark transit of the liquid phase, whereas arrival of solid residue (beans) in the cecum was heralded by a signal of H2 in the breath. PEG 4000 appeared promptly in ileal aspirates, peaking at 1-1.75 h postprandially. Breath H2 excretion was first detected at 1.5-2.5 h after meal A and always peaked later than PEG 4000. When meals shown to be unassociated with generation of breath hydrogen (meals B and C) followed meal A, an augmentation of hydrogen excretion was noted in the early postprandial period. The total volume calculated to pass from ileum to cecum over 24 h was 1,790 +/- 234 ml (range, 1,180-2,515 ml). Ileal flow increased promptly and significantly after each meal (P less than 0.005) and remained high for 3 h or more. These results confirm that, in healthy humans, about 2 liters of chyme pass from ileum to colon each 24 h and ileal flow increases postprandially. They also suggest that the liquid and solid phases of a mixed meal are separate in the ileocecal region.
Cell site and time course of DNA synthesis in pancreas after caerulein and secretin
Authors: Solomon T. E. , Vanier M. , Morisset J.
Published: December 2017

Pancreatic weight, [3H]-thymidine incorporation into DNA, labeling indices, and total DNA and RNA content were measured in rats treated with vehicle or 1 microgram/kg caerulein, 100 micrograms/kg secretin, or a combination of these peptides injected every 8 h for 1-5 days. Incorporation of [3H]thymidine into DNA increased 12-fold after 2 days of treatment with the combination of peptides. DNA content increased after 3 days and reached a level 1.8 times control after 5 days. Autoradiography showed that two cell types, acinar and an unidentified type, were the sites of increased DNA synthesis. Different patterns of labeling were seen in the two populations: acinar cell labeling indices were increased at 1 and 2 days (20-fold) and then fell; nonacinar cells showed an increase only after 2 days and maintained this increase after 5 days. Potentiation (greater than additive effects) was found when caerulein and secretin were injected together for all measurements except RNA content. These data indicate that DNA synthesis in two cell populations is affected by secretin and caerulein and support the occurrence of potentiation between secretin and caerulein for trophic effects on the exocrine pancreas.
Permeability of pancreatic capillaries to small molecules
Authors: Kvietys P. R. , Perry M. A. , Granger D. N.
Published: December 2017

The permeability of capillaries in the isolated, blood-perfused canine pancreas was studied with the double-indicator dilution technique. The permeability-surface area products (PS) for inulin and beta-lactoglobulin A were determined at different plasma flows (attained by pump perfusion). The PS for inulin increased with increasing plasma flow, while the PS for beta-lactoglobulin A was relatively independent of plasma flow. At the highest plasma flow acquired, PS for inulin and beta-lactoglobulin A were approximately 23 and 3.5 ml X min-1 X 100 g-1, respectively. The ratio of the PS values for these two solutes was greater than the ratio of their free diffusion coefficients, indicating restricted diffusion of beta-lactoglobulin A relative to inulin. The degree of restriction was consistent with a maximum equivalent pore radius of 67 A for pancreatic capillaries. An ultrastructural analysis revealed that ductal as well as acinar and islet capillaries were fenestrated. The permeability characteristics of fenestrated pancreatic capillaries are similar to those previously reported for the small intestine.
Intracellular bile acid transport in rat liver as visualized by electron microscope autoradiography using a bile acid analogue
Authors: Suchy F. J. , Balistreri W. F. , Hung J. , Miller P. , Garfield S. A.
Published: December 2017

The role of hepatocyte organelles in the intracellular transport and secretion of conjugated bile acids has not been defined. Therefore we studied the transport and observed the subcellular localization of the bile acid analogue 125I-cholylglycyltyrosine by electron microscope autoradiography to further understand the possible compartmentation of bile acids within the hepatocyte. 125I-cholylglycyltyrosine, which retains a net negative charge, exhibited transport properties similar to native bile acids. After portal vein injection, the compound was recovered intact from bile, and the pattern of excretion paralleled that of [14C]cholylglycine. In addition, cholylglycyltyrosine uptake by isolated hepatocytes was sodium dependent. For autoradiography the analogue was injected into the portal vein, and the liver was perfusion fixed after 30 or 300 s. Light microscope autoradiography performed 30 s after isotope injection demonstrated a steep periportal-to-centrilobular gradient for 125I-cholylglycyltyrosine uptake. At 30 s quantitative grain analysis of electron microscope autoradiographs showed predominant labeling of the plasma membrane and the smooth endoplasmic reticulum (SER). The grain distribution over the region of the plasma membrane decreased from 15% at 30 s to 7% by 300 s and was associated with a sevenfold increase in labeling of the Golgi apparatus and a sixfold increase in labeling of the pericanalicular region. Grain distribution over the SER at 300 s was the same as that noted at 30 s. The hypothesis is presented that bile acids move from the sinusoidal plasma membrane to bile via a pathway that includes the SER and Golgi apparatus.
Calcium-calmodulin-stimulated protein kinase in developing pancreas
Authors: Gorelick F. S. , Chang A. , Jamieson J. D.
Published: December 2017

To implicate the Ca2+-calmodulin-dependent protein kinase (CDPK) in the secretory response of pancreatic acinar cells to postnatal neurohumoral stimulation, we examined enzymatic protein kinase activity during pancreatic development. CDPK was investigated by measuring the phosphorylation of endogenous proteins and an exogenous substrate, synapsin I. Ca2+-calmodulin (CaM)-stimulated phosphorylation of endogenous proteins as well as synapsin I progressively increased in pancreatic supernatants from rats of increasing age. When compared with embryonic pancreas (1 day before birth), Ca2+-CaM-stimulated protein kinase activity increased two- and sixfold in neonatal (1 day after birth) and adult pancreas (60 days after birth), respectively, when normalized to protein content. To further characterize CDPK activity, soluble fractions prepared from embryonic, neonatal, and adult pancreas were separated by gel filtration chromatography. CDPK activities from embryonic and neonatal pancreas were contained in fractions of relative molecular weights (Mr) less than 200,000. In contrast, kinase activity from adult pancreas was predominantly comprised of a Mr approximately 550,000 species that coeluted with a type II CDPK. Increasing amounts of a Mr = 51,000 CaM-binding protein as a function of increasing age were consistent with the developmental appearance of the CaM-binding subunit of type II Ca2+-CaM-stimulated protein kinase. CaM levels increased in parallel with total Ca2+-CaM-stimulated protein kinase activity. Coordinate enhancement of type II CDPK activity and secretagogue responsiveness during pancreatic maturation may suggest a role for this enzyme in the secretory process.
A carrier-mediated, Na+ gradient-dependent transport for biotin in human intestinal brush-border membrane vesicles
Authors: Said H. M. , Redha R. , Nylander W.
Published: December 2017

Transport of biotin across human intestinal brush-border membrane (BBM) was examined using brush-border membrane vesicle (BBMV) technique. Uptake of biotin by BBMV is mostly the result of transport of the substrate into an active intravesicular space with little binding to membrane surfaces. The transport of biotin was carrier mediated and was 1) Na+ (but not K+) gradient dependent with a distinct "over-shoot" phenomenon, 2) saturable as a function of concentration in the presence of a Na+ (but not a K+) gradient with an apparent Km and Vmax for the Na+ gradient-dependent system of 5.26 microM and 13.47 pmol.mg protein-1.20 s-1, respectively, and 3) inhibited by structural analogues and related compounds. Unlike the electrogenic transport of D-glucose, transport of the anionic biotin in the presence of a Na+ gradient (out greater than in) was not affected by imposing a relatively positive intravesicular electrical potential, suggesting that biotin transport is most likely an electroneutral process. These results demonstrate the existence of a carrier-mediated system for biotin transport in human BBM and show that the transport process is Na+ gradient dependent and electrically silent. It is suggested that biotin transport across the BBM is driven by a Na+ gradient most probably through a biotin-Na+ cotransport system.
Temporal changes in mechanical properties of rat jejunal smooth muscle after myenteric plexus ablation
Authors: Herman J. R. , Bass P.
Published: December 2017

We determined length-stress properties and active tension development of rat jejunal longitudinal and circular muscle at various times after myenteric neuron ablation. Myenteric neurons were destroyed by serosal application of benzalkonium chloride. Active tension generation in response to both carbachol and barium was depressed in both muscle layers up to 7 days after treatment, at which times the responses were normal. At 15 days, circular muscle responses were still comparable to control, but longitudinal muscle responses were significantly increased. Length-stress parameters of circular muscle were minimally affected, while those of longitudinal muscle were significantly altered 15 and 30 days after treatment. These alterations include changes in resting stress and increased active stress generation at both times. Our results suggest that 1) normal myenteric innervation is necessary for normal contractile activity in rat jejunal smooth muscle and 2) changes in cellular or tissue morphology or alterations in intracellular calcium homeostasis, as seen in other tissue, may occur after myenteric plexus ablation.
Electrophysiological analysis of responses to intrinsic nerves in circular muscle of opossum esophageal muscle
Authors: Serio R. , Daniel E. E.
Published: December 2017

The nerve-mediated responses to electrical field stimulation (EFS) along the opossum esophageal circular smooth muscle were studied with the sucrose-gap recording technique. Strips from 1-2, 4-5, 7-8, and 10-11 cm above the lower esophageal sphincter were stimulated with short-train (300 ms) and long-train (3 s) durations at 29 degrees C. The response always consisted of a hyperpolarization [inhibitory junction potentials (IJP)] followed by an "off depolarization" often associated with spike potentials and mechanical contraction. Proximal to distal differences in the characteristics of the evoked responses were found, i.e., increasing amplitude, duration and time to peak hyperpolarization of the IJP, increasing latency, and amplitude of the off depolarization. Neither atropine, scopolamine, physostigmine, nor guanethidine altered these characteristics substantially. Circular strips of muscularis externa, studied in the organ bath at 37 degrees C using 10-s EFS trains at 5-40 pps, produced off contractions, enhanced by physostigmine and reduced by atropine. High-frequency stimulation occasionally initiated small persistent intrastimulus ("on") responses; some were sensitive to cholinergic agents, but there was no gradient in the delay in their onset. Atropine-insensitive and tetrodotoxin-potentiated transient on responses were occasionally detected. We conclude that only the noncholinergic, nonadrenergic innervation provides a functional intrinsic innervation directly to the opossum esophagus circular smooth muscle when nerves are activated by EFS.
Is there a role for leukotrienes as mediators of ethanol-induced gastric mucosal damage?
Authors: Wallace J. L. , Beck P. L. , Morris G. P.
Published: December 2017

The role of leukotriene (LT) C4 as a mediator of ethanol-induced gastric mucosal damage was investigated. Rats were pretreated with a number of compounds, including inhibitors of leukotriene biosynthesis [4-bromo-2,7-dimethoxy-3H-phenothiazin-3-one (L651,392), 3-amino-[m-(trifluoromethyl)-phenyl]-2-pyrazoline hydrochloride (BW755c), and dexamethasone] and agents that have previously been shown to reduce ethanol-induced damage [prostaglandin E2, 2-decarboxy-2-hydroxymethyl-15-deoxy-16RS-hydroxy-16- methyl prostaglandin E1 (Rioprostil), FPL52694] prior to oral administration of absolute ethanol. Ethanol administration resulted in a fourfold increase in LTC4 synthesis. LTC4 synthesis could be reduced significantly by pretreatment with L651,392 or dexamethasone without altering the susceptibility of the gastric mucosa to ethanol-induced damage. LTC4 release from hemorrhagic tissue was not significantly increased above that from samples of nonhemorrhagic tissue from the same stomachs. Furthermore, changes in LTB4 synthesis paralleled the changes in LTC4 synthesis observed after ethanol administration. The effects of ethanol on gastric eicosanoid synthesis were further examined using an ex vivo gastric chamber preparation that allowed for application of ethanol to only one side of the stomach. Such treatment resulted in significant increases in LTC4 synthesis on both sides of the stomach (compared with controls), although the increase on the challenged side was significantly greater than that on the nonchallenged side. These studies, thus, confirm that ethanol can stimulate gastric leukotriene synthesis independent of the production of hemorrhagic damage. Inhibition of LTC4 synthesis does not confer protection to the mucosa, suggesting that LTC4 does not play an important role in the etiology of ethanol-induced gastric damage.
Distinct activation of Na+-H+ exchange by gastrin and CCK peptide in acini from guinea pig
Authors: Bastie M. J. , Delvaux M. , Dufresne M. , Saunier-Blache J. S. , Vaysse N. , Ribet A.
Published: December 2017

The effect of cholecystokinin (CCK)-gastrin family peptides (caerulein, unsulfated gastrin-17, and pentagastrin) and secretin in activating amiloride-sensitive 22Na uptake were investigated in guinea pig pancreatic acini. Secretin had no effect, but CCK-gastrin peptides stimulated the amiloride-sensitive 22Na uptake. The effect of caerulein was inhibited by dibutyryl guanosine 3',5'-cyclic monophosphate (cGMP) and asperlicin, indicating that activation of the Na+-H+ antiport caused by caerulein is mediated by CCK receptors. The effect of gastrin was dibutyryl cGMP and asperlicin insensitive, whereas the effect of pentagastrin was inhibited by the CCK antagonists but with a low affinity, indicating that the effect of gastrin and that of pentagastrin was CCK receptor independent. The calcium ionophore A23187 caused an increase in amiloride-sensitive 22Na uptake. However, the effect of caerulein, which increased internal calcium concentration, was not modified after depletion of intracellular calcium, and that of CCK-gastrin family peptides was not dependent on external calcium concentration. Activation of amiloride-sensitive 22Na uptake was also induced by 12-O-tetradecanoylphorbol 13-acetate and 1-oleoyl-2-acetyl-glycerol. Activation of protein kinase c may be involved in the mechanism of caerulein or gastrin in activating the Na+-H+ exchange.
Active calcium transport by intestinal endoplasmic reticulum during maturation
Authors: Ghishan F. K. , Arab N.
Published: December 2017

Calcium uptake by intestinal endoplasmic reticulum was determined during maturation in the rat. Calcium uptake was enhanced severalfold by the presence of ATP in suckling, weanling, and adolescent rats. Uptake values were higher during early life and decreased gradually with age. Calcium uptake represented transport into the intravesicular space of the microsomes as evident by marked decrease in the uptake of 0 degrees C compared with values at 25 degrees C and by rapid release of intravesicular calcium by the ionophore A23187. Calcium uptake was dependent on magnesium and media pH and was inhibited by vanadate. Sodium oxalate enhanced calcium uptake. Oligomycin and sodium azide did not inhibit calcium uptake by microsomes, suggesting that calcium uptake represents a property of the microsomes rather than mitochondrial uptake. Initial rate uptake was linear up to 30 s. Maximal uptake occurred at pH 7.2. Kinetic studies revealed a high-affinity, high-capacity system in microsomes from suckling rats (Vmax 2.26 +/- 0.2 nmol.mg protein-1.15 s-1 and Km 0.56 +/- 0.01 microM) compared with a low-capacity system in microsomes from adolescent rats (Vmax 0.72 +/- 0.1 nmol.mg protein-1.15 s-1 and Km 0.69 +/- 0.02 microM). These findings suggest that the endoplasmic reticulum of the enterocyte may play a major role in regulating intestinal cytosolic calcium homeostasis during early development.
Secretagogues activate chloride transport pathways in pancreatic zymogen granules
Authors: Gasser K. W. , DiDomenico J. , Hopfer U.
Published: December 2017

The membrane permeability of pancreatic zymogen granules was evaluated in vitro with granules isolated from rats in different secretory states: 1) untreated, 2) pretreated with a muscarinic antagonist, 3) pretreated with a muscarinic and an adrenergic antagonist, 4) pretreated as in 3 and then stimulated with the secretagogue cholecystokinin 4 min before death, and 5) pretreated as in 3 and then stimulated with the secretagogue secretin 4 min before death. Granules isolated from untreated rats had variable ionic permeabilities but in general possessed both chloride conductance and electroneutral exchange pathways with low permeabilities to alkali metal ions. In contrast, granules from animals pretreated with secretory antagonists had very low ion permeabilities to both inorganic anions, such as chloride, and alkali metal ions. Injection of the peptide secretagogues cholecystokinin or secretin resulted in a relatively fast (within 4 min) activation or induction of high chloride permeabilities through both chloride conductance and chloride/hydroxide (or chloride/bicarbonate) exchange pathways. In addition, the secretagogues increased the cation permeability of the granule membrane, which exhibited a distinct potassium selectivity. Chloride conductance has been postulated to play a major role in fluid secretion coupled to exocytosis of macromolecules [R. C. DeLisle and U. Hopfer, Am. J. Physiol. 250 (Gastrointest. Liver Physiol. 13): G489-G496, 1986]. These results demonstrate that granules may actively participate in the secretory process and suggest that some of the physiological targets in the cascade of events leading to secretion are anion and cation transporters in the zymogen granule membrane.
Neonatal and maternal prostaglandin in the ontogenic response of rat gastric mucosa to H+
Authors: Thorn C. E. , Tepperman B. L.
Published: December 2017

We have previously demonstrated that neonatal rat stomach is less susceptible to luminal H+ when compared with the adult. In the present study we investigate the role of endogenous prostaglandins (PG) in the ontogeny of gastric permeability responses to H+. Responses to luminal instillation of 250 mN HCl were measured in rats at 10, 15, 20, and 25 days after birth. Mucosal responses were measured in terms of loss of H+ and appearance of Na+, K+, and protein in the luminal instillate. Indomethacin (IM; 8 mg/kg sc) administration to rat pups reduced mucosal levels of prostaglandin E2 (PGE2) and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha). In response to intraluminal HCl, the reduction of mucosal PG did not significantly affect transmucosal fluxes of ions and protein when compared with control pups. IM was also given to lactating dams on days just prior to the pups being 10, 15, 20, and 25 days old. IM treatment significantly reduced the content of PGE2 and 6-keto-PGF1 alpha in maternal milk. Permeability responses in pups from IM-treated dams were increased over pups from control dams. This effect was not observed in 25-day-old rats. Treatment of pups from IM-injected dams with PGE2 but not PGI2 partially restored the permeability responses to luminal H+ to levels observed in pups from control dams.(ABSTRACT TRUNCATED AT 250 WORDS)
Histamine or adenosine blockade alters intestinal blood flow autoregulation in swine
Authors: Buckley N. M. , Diamant S. , Frasier I. D. , Owusu K.
Published: December 2017

The possible role of histamine or adenosine in intestinal blood flow autoregulation in 1-mo-old swine was examined by obtaining pressure-flow relationships before and during intestinal histamine H1- or adenosine-receptor blockade in two groups of fasting animals under anesthesia with pentobarbital sodium (30 mg/kg). Changes in abdominal and thoracic aortic pressures and in superior mesenteric and left renal arterial flows were recorded during controlled aortic compression above the celiac artery. After control intestinal and renal pressure-flow relationships were obtained, a test dose of agonist (0.1 microgram histamine or 0.2 microgram adenosine/kg body wt) was given into the superior mesenteric artery. Then an intra-arterial infusion of blocking agent was started (0.1 mg.kg-1.min-1 chlorpheniramine or 10 mumol/min theophylline). Degree of blockade was assessed with doses of agonist given before and after a second set of intestinal and renal pressure-flow relationships was obtained. Complete blockade of intestinal vascular histamine H1-receptors with chlorpheniramine abolished, and incomplete blockade of adenosine-receptors with theophylline attenuated, intestinal blood flow autoregulation. Renal blood flow autoregulation remained at its control level. These results indicate that both histamine and adenosine are among the physiological vasodilators contributing to intestinal blood flow autoregulation when arterial pressure is decreased in young swine.
Motilin receptors on isolated gastric smooth muscle cells
Authors: Louie D. S. , Owyang C.
Published: December 2017

Motilin has a stimulating effect on gastrointestinal motility. The mechanism of its action is not known. Direct and neuronal effects have been postulated. To determine if receptors are present on smooth muscle cells we investigated the effect of synthetic porcine motilin and its interaction with acetylcholine on isolated guinea pig gastric smooth muscle cells. Motilin elicited a dose-dependent contraction of gastric smooth muscle cells. Minimal (8.3 +/- 1.3%) and maximal (33.9 +/- 2.4%) responses were observed at 10(-12) and 10(-6) M, respectively. The ED50 of motilin was 10(-9) M. Acetylcholine also elicited a dose-response muscle contraction with a maximal response observed at 10(-7) M. Atropine (10(-7) M) completely inhibited the maximal response to acetylcholine but did not have any effect on the contractile response to motilin. In addition, dibutyryl guanosine 3',5'-cyclic monophosphate (10(-3) M) and substance P antagonist, spantide (10(-4) M), also did not inhibit the action of motilin. Acetylcholine (10(-11) M) shifted the dose-response curve of motilin to the left by 1.5 log units. The maximal response to the combination of motilin (10(-6) M) and acetylcholine (10(-11) M) was 32 +/- 3.2%, which was similar to the maximal response to motilin alone. It is concluded that distinct motilin and muscarinic receptors are present on guinea pig gastric smooth muscle cells. The interaction between motilin and acetylcholine is additive and not potentiative.
Human pancreatic secretion during phase II antral motility of the interdigestive cycle
Authors: Layer P. , Chan A. T. , Go V. L. , DiMagno E. P.
Published: December 2017

We determined if changes in the irregular motor activity of phase II, the dominant motility phase in awake fasting humans, are associated with fluctuations in pancreatic secretion by intubating the upper gastrointestinal tract of 15 healthy humans and recording antral and duodenal motility and obtaining duodenal samples for one or two interdigestive motility cycles. Antral phase II activity was graded as having low, intermediate, or high frequency of contractions and related to duodenal trypsin output and plasma concentrations of motilin and human pancreatic polypeptide (HPP), a marker of vagal cholinergic tone. Low, intermediate, and high phase II motor activities were significantly associated with trypsin outputs (U/10 min; mean +/- SE) of 576 +/- 137, 1,441 +/- 225, and 3,621 +/- 521, respectively (P less than 0.001). Plasma motilin levels did not vary with the grades of phase II motility (P greater than 0.1), but levels of plasma HPP and the grades of phase II motility were positively correlated (P less than 0.001). The close correlation among motility, pancreatic secretion, and plasma HPP during phase II suggests that vagal cholinergic pathways are involved in the common regulatory mechanism controlling phase II interdigestive motility and pancreatic secretion.