bluuebunny/crossref_metadata_2025 huggingface dataset:
Antral volume and propulsion-retropulsion in response to upper intestinal nutrients in a canine model
Authors: Kumar D. , Ritman E. L. , Malagelada J. R.
Published: December 2017

We measured antral volumes and propulsion-retropulsion for individual peristaltic cycles using the dynamic spatial reconstructor in three female mongrel dogs. Our aim was to quantify the effect of intestinal perfusion of equicaloric, isotonic, and isomolar nutrients (maltose, 32.5 mg/100 ml; casein hydrolysate, 32.5 mg/100 ml; and oleic acid 15.5 mg/100 ml) at a rate of 10 ml/min in the upper small intestine on total antral volume and the propulsion-retropulsion function of the "antral pump." Isotonic saline was used as a control solution. Isotonic gastrografin (600 ml) was instilled intragastrically as a meal. A 6-channel perfused manometric assembly was used to record antral phasic pressure activity. Antral volume was significantly lower (P < 0.05) in response to fat perfusion compared with other nutrients or isotonic saline. The propulsion-retropulsion ratio was also significantly reduced (P < 0.05) in response to fat perfusion in the upper small intestine. Our study, therefore, indicates that the fraction of a liquid meal delivered to the antrum is determined, at least in part, by the upper small intestinal nutrients and also that the presence of fat in the small intestine alters the propulsion-retropulsion function of the antrum.
Portal transport of long acyl chain lipids: effect of phosphatidylcholine and low infusion rates
Authors: Mansbach C. M. , Dowell R. F.
Published: December 2017

The transport of absorbed long acyl chain lipids in the portal vein of rats has been shown to be 39% when the duodenal input rate is 135 mumol/h glyceryl trioleate (TO) [C. M. Mansbach II, R. F. Dowell, and D. Pritchett, Am. J. Physiol. 255 (Gastrointest. Liver Physiol. 18): G530-G539, 1991]. These calculations were based on a new experimental model in which portal flux is calculated from the knowledge of portal flow and the concentration of the lipids in excess in the portal vein vs. the carotid artery. To test this model, rats were infused for 6 h with a low rate of [3H]TO (27 mumol/h) with or without phosphatidylcholine (9 mumol/h) or with [3H]TO (135 mumol/h) plus phosphatidylcholine (9 mumol/h) or with [3H]TO (135 mumol/h) plus phosphatidylcholine (9 mumol/h). In all three cases, portal flux was expected to be less. Portal transport was 16.5% of the input rate in the low-dose group, 1.4% in the high-dose group given phosphatidylcholine, and 0.5% in the low-dose plus phosphatidylcholine group. There was no net transport of fatty acid in the portal vein in any of the three cases. These data show that portal lipid transport is dependent on the lipid load and that it is greatly reduced at high loads by including phosphatidylcholine in the lipid infusion.
Structural analysis of CGRP receptors on gastric smooth muscle and pancreatic acinar cells
Authors: Honda T. , Zhou Z. C. , Gu Z. F. , Kitsukawa Y. , Mrozinski J. E. , Jensen R. T.
Published: December 2017

Calcitonin gene-related peptide (CGRP) immunoreactivity is widely distributed in the central nervous system and gastrointestinal (GI) tract, and specific receptors have been described on many GI tissues. In the present study, we compared CGRP receptors on gastric smooth muscle cells with those on pancreatic acini from guinea pig with the use of chemical cross-linking techniques combined with various enzymatic digestions. 125I-labeled rat CGRP-I demonstrated temperature-dependent saturable binding to both acinar and gastric smooth muscle cell membranes. After binding, membranes were incubated with 1 mM disuccinimidyl suberate (DSS), solubilized with sodium dodecyl sulfate (SDS), and subjected to SDS-polyacrylamide gel electrophoresis. Cross-linked radioactivity was analyzed by autoradiography. A single broad radioactive band [molecular weight (M(r)) 57,000] was seen on cell membranes from both tissues and after cross-linking to intact cells. These bands were not altered by addition of dithiothreitol. This radioactive band was not detected without DSS present or with addition of 10 microM rCGRP-I. rCGRP-I inhibited cross-linking with half-maximal inhibition of 32 nM with membranes from both tissues, and there was a close correlation between its ability to inhibit binding and to inhibit cross-linking. Cross-linking was not inhibited by non-CGRP related peptides. With membranes from both tissues, N-glycanase digestion increased the mobility of the original band. Neuraminidase digestion only slightly increased the mobility of the original band; however, the subsequent addition of O-glycanase showed no additional effect on both membranes. Endoglycosidase H digestion had no effect in either tissue. The present results demonstrate that on both tissues the cell membrane receptor for CGRP is an N-linked sialoglycoprotein. The apparent M(r) of this sialoglycoprotein is 57,000, and this polypeptide does not contain disulfide-linked subunits or O-linked carbohydrates.
Effects of cholecystokinin on cytosolic calcium in pancreatic duct segments and ductal cells
Authors: Smith J. P. , Yelamarty R. V. , Kramer S. T. , Cheung J. Y.
Published: December 2017

Although the gastrointestinal peptide cholecystokinin (CCK) has been shown to increase bicarbonate and water secretion and potentiate the effects of secretin on pancreatic ducts, CCK receptors have not been identified on pancreatic ductal epithelium. The effects of CCK octapeptide (CCK-8) on cytosolic calcium were evaluated on microscopically dissected rat pancreatic duct segments and single rat duct cells from the established ARIP cell line. By use of fluorescence microscopy in fura-2-loaded duct segments or single cells, intracellular calcium concentration was measured in response to CCK-8 (4 x 10(-12)-4 x 10(-8) M). CCK-8 significantly increased cytosolic calcium up to 50-fold over baseline. The greatest increase occurred with the highest concentration of CCK-8 (4 x 10(-8) M). Oscillations were observed in experiments performed in buffer containing 0.68 mM physiological calcium. In another series of experiments performed in the presence of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid to deplete extracellular calcium, CCK-8 treatment still resulted in significant increases in cytosolic calcium; however, oscillations were abolished. Since cytosolic calcium increased in the absence of extracellular calcium, the initial calcium rise most likely was from cytosolic stores. Our findings of CCK-8-stimulated increases in cytosolic calcium in microdissected pancreatic ducts suggest the presence of CCK receptors, a characteristic that was not lost in cultured pancreatic ductal cells. In addition, in ARIP cells, the CCK-8-induced increase in cytosolic calcium was abolished by pretreatment with the selective CCK-B receptor antagonist L-365,260 but not by the CCK-A receptor antagonist L-364,718.
Potassium conductance in rabbit esophageal epithelium
Authors: Khalbuss W. E. , Alkiek R. , Marousis C. G. , Orlando R. C.
Published: December 2017

K+ conductance in apical and basolateral cell membranes of rabbit esophageal epithelial cells was investigated within intact epithelium by impalement with conventional microelectrodes from luminal or serosal sides. Under steady-state conditions, K+ conductance was demonstrated in basolateral, but not apical, membranes by showing 1) membrane depolarization upon exposure to either solutions high in K+ (20-65 mM) or containing Ba2+, tetraethylammonium, or quinine, and 2) a resistance ratio that increased on exposure to high K+ solution and decreased on exposure to Ba2+, quinine, and tetraethylammonium. From exposures to high K+, the apparent K+ transference number and electromotive force generated at the basolateral membrane were calculated and found to be 0.42 +/- 0.01 and -83 +/- 3 mV, respectively. Furthermore, basolateral K+ conductance was shown to be important for maintaining resting net transepithelial Na+ absorption in that high K+ or barium inhibited the transepithelial potential difference and short-circuit current of Ussing-chambered epithelia. We conclude that under steady-state conditions the basolateral, but not apical, membranes of esophageal epithelial cells contain a K(+)-conductive pathway and that this pathway is important for active sodium absorption.
Trefoil peptides: a newly recognized family of epithelial mucin-associated molecules
Authors: Poulsom R. , Wright N. A.
Published: December 2017

Members of the trefoil family of peptides are generally small stable secreted molecules, structurally related by the presence of one, or up to six, compact 6-cysteine motifs. Several trefoil peptides are expressed in mammalian gut and Xenopus gut and skin, often in association with mucins. Chronic ulcerative conditions of the gut, such as Crohn's disease, result in the growth of glandular structures of the ulcer-associated cell lineage (UACL) that secrete epidermal growth factor/urogastrone, transforming growth factor-alpha, and at least three trefoil peptides [pS2, human spasmolytic polypeptide (hSP), and intestinal trefoil factor (hITF/hP1.B)]. Neuroendocrine and goblet cells near the UACL are "recruited" into expressing pS2 and hSP, but the purpose of this concerted expression is unclear. A role in mucosal healing has been proposed. Biological functions of trefoil peptides have been difficult to establish. Pancreatic spasmolytic polypeptide of porcine origin inhibits gastric acid secretion and smooth muscle contraction and is a growth factor for some cultured cells, but pS2, once thought to be breast cancer specific, is not a mitogen. Recombinant trefoil peptides have allowed localization of binding sites and will allow structure-activity relationships to be studied, once the functions are clear.
Nitric oxide synthase induction and intestinal epithelial cell viability in rats
Authors: Tepperman B. L. , Brown J. F. , Whittle B. J.
Published: December 2017

The present study determined the presence of constitutive and inducible nitric oxide (NO) synthase activities in intestinal isolated epithelial cells and the effects of NO induction on intestinal epithelial cell viability. Epithelial cells were isolated from rat proximal small intestine by dispersion using citrate and EDTA. Constitutive NO synthase activity, determined by [14C]arginine conversion to citrulline that was inhibited by in vitro incubation with the arginine analogue NG-monomethyl-L-arginine (L-NMMA; 300 microM) or ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA; 1 mM), was observed in these cells. Administration of Escherichia coli lipopolysaccharide (LPS; 3 mg/kg iv) significantly augmented NO synthase activity (determined 4 h later), which was inhibited in vitro by incubation with L-NMMA but not by EGTA. The highest level of constitutive and inducible NO synthase activity occurred in intestinal villus cells, and the lowest was in crypt cells. Induction of NO synthase activity was associated with a decrease in cellular viability as assessed by a decrease in trypan blue exclusion. Dexamethasone pretreatment (1 mg/kg iv 2 h before LPS administration) significantly reduced both induction of NO synthase activity and the reduction in cellular viability. Likewise concurrent administration of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (10 mg/kg sc) ameliorated the reduction in cell viability induced by LPS administration, an effect abolished by pretreatment with the NO substrate L-arginine (350 mg/kg sc). Whereas constitutively formed NO may have a physiological role in these cells, the results in this study suggest that induction of NO synthase in epithelial cells may represent a mechanism of local intestinal damage.
Characterization of univectorial polyamine transport in duodenal crypt cell line
Authors: Scemama J. L. , Grabie V. , Seidel E. R.
Published: December 2017

High levels of polyamines have been identified in the lumen of the intestines. Luminal polyamines are involved in normal mucosal growth and may be the primary source of extracellular polyamines for tumors grown in animals undergoing polyamine antimetabolite therapy. The vectorial movement of polyamines across an in vitro model of the gut was studied in epithelial cells grown in culture. IEC-6 cells were plated on either plastic or raised inserts. Cells grown on plastic were employed to define the kinetic constants for putrescine and spermidine uptake. Eadie-Hofstee plot analysis of putrescine uptake was characteristic of a single class of transporter with a Michaelis constant (Km) of 4.85 +/- 0.57 microM and a maximal velocity (Vmax) of 627 +/- 85 pmol x 15 min-1 x 10(6) cells-1. The plot for spermidine uptake was curvilinear and representative of the interaction of spermidine with two sites: Km 1 and 2 are 0.26 +/- 0.13 and 2.1 +/- 0.77 microM; Vmax 1 and 2 are 177 +/- 50 and 429.5 +/- 70 pmol x 15 min-1 x 10(6) cells-1, respectively. Calmodulin antagonism blocked the uptake of putrescine and the low-affinity but not high-affinity spermidine uptake system. Seven-day postconfluent cells grown on plastic inserts were used to study the vectorial movement of polyamines in a polarized epithelium. The apical membrane domain expressed two sites with similar kinetic constants to those observed when cells were grown on plastic. In contrast, however, the basolateral membrane did not transport polyamines. Spermidine uptake through this membrane was only a fraction of that in the apical membrane and was completely nonspecific.(ABSTRACT TRUNCATED AT 250 WORDS)
Leukotriene B4 and C4 production in isolated rat gastric mucosal cells
Authors: Huber W. , Trautmann M. , Becker I. , Schenck U. , Peskar B. M. , Schepp W.
Published: December 2017

Dispersed rat gastric mucosal cells (F0) were separated into five fractions (F1-F5) by counterflow elutriation, with F1 representing the smallest and F5 the largest cell diameters. In F0-F5, leukotriene B4 (LTB4) release in response to 10(-5) M calcium ionophore A-23187 was 7.68 +/- 1.26, 51.6 +/- 10.8, 72.4 +/- 10.4, 7.1 +/- 0.7, 5.7 +/- 0.6, and 11.6 +/- 3.4 pg.10(6) cells-1 x 30 min-1. In the identical fractions, sulfidopeptide release in response to A-23187 was 200.6 +/- 20.5, 1,116.0 +/- 166.6, 1,309.4 +/- 163.2, 189.8 +/- 25.8, 108.0 +/- 18.0, and 158.4 +/- 54.0 pg.10(6) cells-1 x 30 min-1. High-pressure liquid chromatography verified the radioimmunologically determined LTB4 and identified LTC4 as the only sulfidopeptide LT released. LT release from F2 cells in response to A-23187 was time and dose dependent, reaching maximal stimulation at 10(-5) M A-23187. This response was blocked by the dual inhibitor of cyclooxygenase and lipoxygenases, BW755C (2 x 10(-5)-2 x 10(-4) M), by the selective 5-lipoxygenase inhibitor L-651,392 (10(-7)-10(-5) M), and by MK-886 (10(-9)-10(-7) M), which blocks translocation of 5-lipoxygenase. The postreceptor stimuli dibutyryl adenosine 3',5'-cyclic monophosphate, forskolin, 12-O-tetradecanoyl-phorbol-13-acetate, and oleyl-acetyl-glycerol failed to induce LT release. However, 10(-4) M arachidonic acid increased basal LT release up to eightfold and increased A-23187-stimulated LT release by an additional 30%.(ABSTRACT TRUNCATED AT 250 WORDS)
A nitric oxide and prostaglandin-dependent component of NANC off-contractions in cat colon
Authors: Venkova K. , Krier J.
Published: December 2017

The actions of NO synthase inhibitors and indomethacin, a cyclooxygenase inhibitor, on the nonadrenergic noncholinergic (NANC) mechanical responses of cat distal colon were studied in vitro using muscle strips orientated in the axis of the longitudinal muscle layer with pelvic nerves attached. Electrical field stimulation (EFS) or pelvic nerve stimulation (PNS) caused inhibition of spontaneous contractions followed by off-contractions. Indomethacin (10-30 microM) caused concentration-dependent reductions in amplitude and duration of EFS- and PNS-evoked off-contractions but not latency. The NO synthase inhibitors, N omega-nitro-L-arginine (L-NNA), N omega-nitro-L-arginine methyl ester (L-NAME) and NG-monomethyl-L-arginine (L-NMMA) (each at 100 microM) significantly reduced latency, amplitude, and duration of off-contractions evoked by EFS and PNS. This inhibition was partially reversed by L-arginine (120 microM) but not by D-arginine. Incubation of colonic strips with alpha-chymotrypsin (2 U/ml) decreased latency, amplitude, and duration of NANC off-contractions. L-NNA reduced amplitude, duration, and latency of off-contractions in preparations pretreated with alpha-chymotrypsin. Hydroquinone (10-30 microM), a generator of superoxide anions, caused significant depression of amplitude, duration, and latency of off-contractions which was completely reversed by superoxide dismutase (200 U/ml). These data suggest that the components of NANC off-contractions evoked by EFS and PNS involve peptides, NO, and prostaglandins.
Role of nitric oxide in neurally induced pancreatic exocrine secretion in pigs
Authors: Holst J. J. , Rasmussen T. N. , Schmidt P.
Published: December 2017

Formation of NO, enzymatically catalyzed by NO synthases in both endothelial cells and autonomic nerves, seems to explain some noncholinergic nonadrenergic tissue reactions. We studied the possible role of NO in vagally induced pancreatic exocrine secretion using isolated perfused porcine pancreas (n = 11) with intact vagus nerve (VN) supply. Electrical stimulation of the VN (8 Hz, 10 mA) and infusions of vasoactive intestinal polypeptide (VIP, 2 x 10(-9) M) were carried out before and after addition to the perfusate of the NO synthase inhibitors N omega-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) or NG-nitro-L-arginine (L-NNA, 10(-5) M) with and without further addition of L-arginine (10(-3) M). We also studied the effects of L-arginine alone and of sodium nitroprusside (10(-4) M). In all experiments VN and VIP caused a profuse exocrine secretion (43 +/- 7 and 44 +/- 11 times basal secretion). The inhibitors increased vascular resistance approximately twofold but had no effect on the vascular relaxation caused by VIP and VN. The exocrine fluid response to VN was reduced to 19 +/- 5 and 4.7 +/- 1.8% (L-NAME and L-NNA), and response to VIP was reduced to 54 +/- 12 and 35 +/- 13%. Protein and bicarbonate outputs largely paralleled flow rate. Addition of L-arginine (no effects alone) to L-NAME restored the responses to VN (to 100 +/- 21% of controls) and increased VIP responses (to 65 +/- 11%).(ABSTRACT TRUNCATED AT 250 WORDS)
Nitric oxide synthesis inhibition increases epithelial permeability via mast cells
Authors: Kanwar S. , Wallace J. L. , Befus D. , Kubes P.
Published: December 2017

In this study, we assessed the involvement of mast cells and mast cell-derived mediators in the enhanced epithelial permeability associated with nitric oxide synthesis inhibition. Permeability of the small bowel was assessed by measuring the clearance of a small marker (51Cr-labeled EDTA) from blood to lumen in the presence of the nitric oxide synthesis inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). L-NAME caused a very rapid (10 min) increase in epithelial permeability, reaching peak values (sixfold increase) within 20 min. Two mast cell stabilizers, doxantrazole and lodoxamide, greatly attenuated the rise in mucosal permeability. Rat mast cell protease II activity (marker of mucosal mast cell degranulation) was increased significantly only in the plasma of L-NAME-treated animals. Chronic dexamethasone administration depleted rats of mucosal mast cells and also prevented the L-NAME-induced rise in mucosal permeability. The increase in epithelial permeability was mediated by a number of mediators: platelet-activating factor caused the early rise in epithelial permeability, and histamine caused the later increase in epithelial permeability. Superoxide dismutase attenuated the L-NAME-induced rise in epithelial permeability, suggesting an important and continuous role for superoxide. Transepithelial flux of 51Cr-EDTA across rat intestinal epithelial cell monolayers did not increase in the presence of L-NAME, suggesting that inhibition of nitric oxide does not directly cause epithelial permeability alterations, whereas the in vivo data implicate a potential role for the mast cell. In conclusion, nitric oxide synthesis inhibition activates mast cells in the mucosa and consequently increases epithelial permeability.
Gastric epithelial damage induced by local ischemia-reperfusion with or without exogenous acid
Authors: Kawai T. , Joh T. , Iwata F. , Itoh M.
Published: December 2017

We evaluated the damage to the gastric epithelium produced by local ischemia-reperfusion (IR) with or without luminal perfusion with 0.1 N HCl. Local gastric ischemia was induced by clamping the left gastric artery. Use of radioactive microsphere technique revealed a significant reduction in blood flow induced only in the corpus (67% reduction). Because no measurable gross lesion was observed in this model, the blood-to-lumen clearance of 51Cr-labeled EDTA (51Cr-EDTA) served as an index of epithelial damage. In the absence of exogenous acid, the histological damage was minimum and could not be quantified. However, a significant increase in 51Cr-EDTA clearance was observed shortly after reperfusion in a manner that depended on the duration of ischemia. This increase in clearance reached a maximum approximately 10 min after reperfusion and returned rapidly toward control levels within 40-50 min after reperfusion. In the presence of exogenous acid, EDTA clearance increased significantly during ischemia, increased further during reperfusion, and did not recover for at least 60 min after reperfusion. The acid infused after reperfusion (no acid before reperfusion) did not significantly aggravate the mucosal damage that followed reperfusion. However, the acid infused before reperfusion (no acid after reperfusion) showed an effect on EDTA clearance similar to that induced by continuous acid perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)
Expression and characterization of a functional rat liver Na+ bile acid cotransport system in COS-7 cells
Authors: Boyer J. L. , Ng O. C. , Ananthanarayanan M. , Hofmann A. F. , Schteingart C. D. , Hagenbuch B. , Stieger B. , Meier P. J.
Published: December 2017

A cDNA for the rat liver sodium-dependent bile acid cotransporter was expressed in COS-7 cells to study the functional properties of the translated protein in a mammalian cell line. A 1.2-kb insert was ligated into a pMAMneo vector and transiently transfected using electroporation. After optimal conditions were established, the transiently transfected COS cells were screened with fluorescent-conjugated labeled bile acids for evidence of expression of the cotransporter after 48 h. The uptake of [3H]taurocholate ([3H]TC) was then determined in cells transfected with or without the bile acid insert. Progressive uptake of [3H]TC (0.45 microM) was observed for 30 min in the presence of sodium. In contrast, no uptake of [3H]TC was observed in the absence of sodium, in nontransfected COS cells, or in COS cells transfected with the empty plasmid. Kinetic studies revealed a Michaelis constant (Km) of 29 microM, essentially identical to the Km of this cotransporter described in intact rat hepatocytes and membrane vesicles. Uptake of [3H]TC (5.0 microM) at 5 min (n = 3-6) was inhibited by 100 microM taurochenodeoxycholic acid (81%), tauroursodeoxycholic acid (77%), cholic acid (55%), chenodeoxycholic acid (74%), and ursodeoxycholic acid (56%) but not by 100 microM taurodehydrocholate, 1 mM probenecid, or 100 microM bilirubin. In contrast, bumetanide (500 microM) inhibited [3H]TC uptake by 52%. These studies indicate that the isolated cDNA codes for a physiological bile acid transporter present in rat hepatocytes and that posttranslational factors present in mammalian cells may not be as important in defining properties of this cotransport system.
Localization of amiloride-sensitive Na+ channels in intestinal epithelia
Authors: Carey H. V. , Hayden U. L. , Spicer S. S. , Schulte B. A. , Benos D. J.
Published: December 2017

Polyclonal antibodies raised against purified bovine renal papillary amiloride-sensitive Na+ channels were used to localize Na(+)-channel proteins in mouse and piglet small intestine. Immunostaining using the avidin-biotin-peroxidase technique revealed epithelial Na(+)-channel epitopes localized to apical regions of villus enterocytes in jejunal tissues of both species. Anti-Na(+)-channel antibodies also stained apical borders of villus enterocytes in piglet ileum and apical borders of surface cells in the piglet distal colon. On immunoblots of jejunal, colonic, and renal tissues the anti-Na(+)-channel antibodies recognized one to three polypeptides of apparent molecular masses similar to those found in bovine renal epithelial Na(+)-channel protein (the 55-65, 110-116, and 150-kDa subunits). The antibodies also recognized a polypeptide in the 40- to 45-kDa range in mouse intestine, which is comparable to the 35- to 40-kDa subunit of a renal Na+ channel. The results demonstrate that epitopes comparable to those present in renal amiloride-sensitive Na+ channels are found in apical regions of absorptive epithelial cells in the mammalian small and large intestine.
Endothelin-1 induces direct constriction of hepatic sinusoids
Authors: Zhang J. X. , Pegoli W. , Clemens M. G.
Published: December 2017

We studied the hepatic microvascular response to endothelin (ET) and the possible role of Ito cells (fat-storing cells) acting as pericytes in this response using isolated rat livers under high-power intravital microscopy. Livers were perfused in a modified pressure-controlled system with Krebs buffer plus rat erythrocytes (RBC, 10%), and sinusoids at the site of Ito cells were observed under a x 100 objective (total magnification x 2,533) before and during infusion of ET-1 (10(-9 M) alone, sodium nitroprusside (NP, 10(-5) M). plus ET-1, or phenylephrine (PE, 10(-7) M). Both ET-1 and PE decreased portal flow (25 and 51%) and increased inflow pressure (28 and 43%), respectively. PE had no effect on any sinusoidal parameters except that it decreased measured sinusoidal RBC velocity (P < 0.05); ET-1 decreased sinusoidal diameter by 25% and increased the calculated sinusoidal pressure gradient and resistance by 116 and 350%, respectively, but did not alter RBC velocity. NP significantly inhibited changes induced by ET-1. These results demonstrate that ET-1 induces a specific sinusoidal constriction that disrupts normal acinar flow dynamics, and the sinusoidal constriction colocalizes with Ito cells, suggesting that the constriction may be mediated at least in part by ET-1 action on Ito cells, which can be inhibited by a nitric oxide donor.
Sildenafil (Viagra) attenuates ischemic cardiomyopathy and improves left ventricular function in mice
Authors: Salloum Fadi N. , Abbate Antonio , Das Anindita , Houser Jon-Erik , Mudrick Colin A. , Qureshi Ian Z. , Hoke Nicholas N. , Roy Sion K. , Brown William R. , Prabhakar Shashi , Kukreja Rakesh C.
Published: December 2017

We tested the hypothesis that chronic treatment with sildenafil attenuates myocardial infarction (MI)-induced heart failure. Sildenafil has potent protective effects against necrosis and apoptosis following ischemia-reperfusion in the intact heart and cardiomyocytes. ICR mice underwent MI by left anterior descending coronary artery ligation and were treated with sildenafil (0.71 mg/kg bid) or saline for 4 wk. Infarct size (IS) was measured 24 h postinfarction, and apoptosis was measured by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. Left ventricular end-diastolic diameter (LVEDD) and fractional shortening (FS) were measured by echocardiography. Sildenafil reduced IS (40.0 ± 4.6%) compared with that in saline (69.6 ± 4.1%, P < 0.05). NG-nitro-l-arginine methyl ester, a nitric oxide synthase (NOS) inhibitor (15 mg/kg bid), blocked the protective effect of sildenafil (IS, 60.2 ± 1.6%, P < 0.05 vs. sildenafil). Western blot analysis revealed a significant increase in endothelial NOS/inducible NOS proteins 24 h post-MI after treatment with sildenafil versus saline. Apoptosis decreased from 2.4 ± 0.3% with saline to 1.2 ± 0.1% with sildenafil ( P < 0.05) on day 7 and from 2.0 ± 0.2% with saline to 1.2 ± 0.1% with sildenafil on day 28 ( P < 0.05), which was associated with an early increase in the Bcl-2-to-Bax ratio. LVEDD increased from baseline value of 3.6 ± 0.1 to 5.2 ± 0.2 and to 5.5 ± 0.1 mm on days 7 and 28, respectively, with saline ( P < 0.05) but was attenuated to 4.4 ± 0.2 and 4.4 ± 0.1 mm following sildenafil treatment on days 7 and 28, respectively ( P > 0.05 vs. baseline). FS significantly improved post-MI with sildenafil. A marked decline in cardiac hypertrophy was observed with sildenafil, which paralleled a reduction in pulmonary edema. Survival rate was lower with saline (36%) compared with sildenafil (93%, P < 0.05). Sildenafil attenuates ischemic cardiomyopathy in mice by limiting necrosis and apoptosis and by preserving left ventricular function possibly through a nitric oxide-dependent pathway.
Kinetics of mitochondrial flavoprotein and pyridine nucleotide in perfused heart
Authors: Chance B. , Salkovitz I. A. , Kovach A. G. B.
Published: December 2017

Page 207: B. Chance, I. A. Salkovitz, and A. G. B. Kovach. "Kinetics of mitochondrial flavoprotein and pyridine nucleotide in perfused heart." Page 207: in line 3 of the abstract, the volume identification should read "Am. J. Physiol. 223." Page 217, column 2, line 7 of the acknowledgment should continue "and also by grants from the John A. Hartford Foundation, Inc."
Regional vascular volume and extravascular accumulation of labeled protein during plasma volume expansion
Authors: Studer et al. R. K.
Published: December 2017

Page 699: R. K. Studer et al. "Regional vascular volume and extravascular accumulation of labeled protein during plasma volume expansion." Page 703: column 1, line 40, "23 ± 4" should read, "23 x 10–3," Column 2, line 1, "1,909" should read, "1.909"; lines 4 and 5, "31.8/64 = 0.497" should read, ".0318/64 = 0.497 x 10–3"; line 6, "10" should read, "10 x 10–3"; line 8, "290" should read, "0.290," and "4.83" should read, ".00483"; lines 10 and 11, "4.83/10 = 0.483" should read, "0.00483/10 = 0.483 x 10–3."
Norepinephrine vascoconstrictor escape in isolated meseneric arteries
Authors: Ross G
Published: December 2017

When isolated superfused cat mesentric arterial rings were exposed to norepinephrine(NE) 10'-6 g/ml, force initially increased but subsequently declined despite continuedadministration of NE. Phasic contractions occurred in 48% of the vessels. Norepinephrine concentrations just above threshold induced tonic contractions without escape. When NE was administered after brief exposure of the arterial rings to low-calcium solutions, peak force development and escape were both reduced and phasic contractions were abolished. Escape did not occur in potassium-depolarized vessels. The peak response was increased and escape was reduced by substituting sodium in the Krebs solution by lithium and by substituting chloride with iodide or perchlorate. Substitution of chloride by isethionate reduced the peak NE resonse and abolished escape. Propanolol was without effect. It is suggested that escape from NE vasoconstriction in mesenteric arteries is due to fading of propagated activity.
Sequential changes in intrarenal hemodynamics during saline infusion in the dog
Authors: Velasquez MT , Notargiacomo AV , Cohn JN
Published: December 2017

Intrarenal blood flow and volume (indicator-dilution technique), kidney volume (mercury-in-rubber resistance gage), intr-renal venous pressure, filtration fraction, and sodium excretion were determined dequentially before and during a l-h infusion of isotonicsaline 80 ml/kg in anesthetized dogs. The cortical fraction of renal blood flow roseduring the first 20 min of infusion from an average of 70 to 77%, butreturned nearly to control levels during the last 20 min of infusion because ofa low rise in noncortical flow. During the first 20 min a 23% increase in cortical blood volume accounted for one-third of the 8.5% increase in kidney volume, whereasin the last 20 min cortical blood volume had fallen nearly to control values and kidneyvolume was increased by 17.2%. Intrarenal resistances calculated from intrarenalpressure and flow indicated persistent cortical prevenous dilatation, progressive cortical venous constriction, and only a slight late reduction in noncortical resistance.These data indicate that hemodynamics are shanging continuously during saline infusion and the natriuresis probably is multifactorial.
Acetylcholine and norepinephrine interactions on cardiac lipids and hemodynamics
Authors: Glaviano VV , Goldberg J , Pindok MT
Published: December 2017

In open-chest dogs anesthized with sodium pentobarbital, acetylcholine (ACh, 5 times 10'-5M) infused into the left circumflex coronary artery caused an increase in coronary flow and a decrease in myocardial O'2 extraction ratio (P less than .01) anduptake (P less than .05). Heart rate and mean arterial pressure were not altered,although left ventricular dP/dt declined from 2,037 plus or minus 205 to 1,873 plus or minus 194 mmHg/s (P less than .02). Intracoronary administration of norepinephrine (NE, 2.4 times 10'-6M) caused an increase in myocardial O'2 uptake (P less than .02); simultaneous infusion of both NE and ACh caused a decline in O'2 extraction ratio (P less than .01) and uptake (P less than 0.5). Myocardial adenylatecyclase activity in response to ACh was not altered significantly from a control levelof 188 plus or minus 22 pmol of '14C-labeled cyclic AMP/mg protein per 10 min. Norepinephrine alone elevated adenylate cyclase activity to 401 plus or minus 45 pmol ['14C]cyclic AMP/mg protein per 10 min (P less than .01). However, with simultaneous infusion of both NE and ACh, adenylate cyclase returned to control levels. Although ACh alone did not alter myocardial hormone-sensitive lipaseactivity, NE elevated lipolytic activity from 8.1 plus or minus .7 to 13.2 plus or minus 1.8 mueq free fatty acid (FTA)/g per 30 min (P less than .05). The administration of both ACh and NE returned lipase activity to nearly control levels. Myocardial uptake of FFA increased significantly during ACh infusion alone (P less than 0.5) and during NE infusion alone (P less than 905). However, when NE and AChwere administered together, a decline in FFA uptake was observed (P less than .02).These data indicate that the effects of ACh on cardiac metabolism are minimal, withthe decline in myocardial O'2 uptake of ACh primarily reflecting the decrease in contractility. On the other hand, antagonism of ACh on NE-stimulated myocardial lipid metabolism appears to involve activity of the adenylate cyclase system.
Basis for late expiratory spinal inhibition of phrenic nerve discharge
Authors: Zielinski AT , Gebber GL
Published: December 2017

The relationship between spinal inhibition of phrenic nerve activity and thoratic expiratory motoneuronal discharge was studied in chloralose-anesthetized and unanesthetized decerebrate cats. The amplitude of the phrenic nerve response elicited by singleshocks applied to descending tracts in the second cervical spinal segment progressively fell during the late expiratory phase of the central respiratory cycle. The depression resulted, at least in part, from active spinal inhibition since the spina-to-phrenic evoked response was smaller in late expiration than after C'1 spinal transection. Inhibition of the spinal-to-phrenic evoked was time-locked to the spontaneousburst of activity recorded from the eigth internal intercostal nerve. The degree of inhibition of the spinal-to-phenic evoked discharge was directly related to theamplitude of spontaneously occurring internal intercostal nerve activity. A similiarrelationship was observed when internal intercostal nerve activity and spinal inhibitionof phrenic discharge were evoked by stimulation of the superior laryngeal nerve. It is concluded htat late expiratory spinal inhibition of phrenic discharge was dependent on those neural events responsible for the activation of thoracic expiratory motoneurons.
NE and ACh responses of intrapulmonary vessels from dog, swine, sheep, and man
Authors: Joiner PD , Kadowitz PJ , Hughes JP , Hyman AL
Published: December 2017

The effects of norepinephrine (NE) and acetylcholine (ACh) on isometric force generation were studied in isolated helical strips of intrapulmonary arteries (IPA) and veins (IPV) (3-5 mm diam) from lungs of dog, sheep, swine, and man. Cummalative dose-effect relationships (10-minus8-10-minus 4 M) were determined. All strips contracted in a dose-related fashion when exposed to NE but responses of sheep and swineIPV were weak. Acetylcholine relaxed canine IPA and contracted human IPA, CANINEIPV, and sheep IPV in a dose-related manner. Sheep IPA and swine IPA and IPV were unresponsive to ACh. Human IPV were relaxed by ACh but this effect wasreversed at the highest concentration (10 minus 4 M) tested. All vascular stripscontracted well in a potassium-rich (127 mM) bathing medium. It is concluded thatintrapulmonary lobar vessels from man, dog, swine, and sheep are responsive to autonomicneurohormones but that quantitative as well as qualitative differences exist.
Renin secretion from rat renal cortical cell suspensions
Authors: Lyons HJ , Chruchhill PC
Published: December 2017

Renin secretion of rat renal cortical cell suspensions was studied as a functionof variations in the composition of the suspension media. Renin secretion was determined by incubating samples of the suspension media with rat renin substrate and measuringthe angiotensin I generated by radioimmunoassay. Increasing the medium sodium concentration (50-144 meq/liter) linearly decreased the rate of renin secretion. This relationship was unaffected by adding ouabain (10 minus 3 M) to the suspensions. The addition of furosemide (from 10 minus 5 to 10 minus 3 M) stimulated renin secretion. Considered with previous observations, these results suggest that renin secretionis controlled by some function of sodium on the lumenal boder of the macula densa cells.
Glycerokinase in mammalian adipose tissue: stimulation by lipogenic substances
Authors: Persico PA , Cerchio M , Jeffay H
Published: December 2017

A connecting link between carbohydrate and fat metabolism in adipose tissue is theconcentration of alpha-glycerophosphate derived predominantly from the glycolysis ofglucose entering the fat cell. However, several investigators have reported the presence of a glycerol specific kinase in the epidiymal fat-pad of the rat and obob mouse.This enzyme's presence in other mammalian adipose tissue could contribute to the alpha-glycerophosphate pool and thus affect both carbohydrate and fat metabolism within the fat cell. Glycerokinase was demonstrated in isolated fat cells obtained from the subcutaneous, perirenal, epididymal, and dorsal intrascapular brown fat depots of the adultmale rat. It was found to be particularly sensitive to in vivo lipogenic stimuli in both the subcutaneous and the brown adipose tissue and concluded that insulin is involved in adipose glycerokinase stimulation. Therefore, the main function of glycerokinase in normal adipose tissue may be to augment the anabolic action of insulin. It isfurther suggested that deviation from the normal control of this lipogenic enzyme couldlead to a gradual accumulation of fat and eventual obesity.
Changes in cortical impedance and EEG activity induced by profound hypotension
Authors: Gamache FW  , dold GM , Myers RE
Published: December 2017

Fourteen late juvenile monkeys were subjected to a single 30-min episodes of markedhypotension using an infusion of trimethaphan. Afterward, blood pressure was rapidly restored to and maintained at preinsult levels with an intravenous drip of phenylephrine (.02 mg/ml). The respiratory gas tensions and pH of the arterial blood weremaintained within normal limits at all times. During the 30-min episodes, the cortical electrical impedence increased by a mean of 27% while the EEG frequencies and amplitudes decreased by 47 and 30%, respectively. The impedance and EEG activity generally altered at the same time but inversely to one another, although, on restoration of blood pressure, the impedance recovered within minutes while the EEG activity returned to normal only after 1 h. The impedance values and EEG activity of those animals that eventually died began to diverge significantly from the values of theanimals that were to survive at about 2.5 h after restoration of blood pressure.
Adipose tissue blood flow and cellularity in the growing rabbit
Authors: Digirolamo M , Esposito J
Published: December 2017

Resting blood flow was measured in isolated, innervated, epigastric fat-pads of 27 male rabbits during growth in the 1st yr of life and found to vary widely in range (7.6-28.1 ml/100 g tissue per min). Definition of adipose tissue composition and of fat-cell size and number made it possible to explain the wide range of flow and to identify two types of relationships between adipose blood flow and tissue constituents. Expressed in the usual manner (ml/100 g tissue per min), adipose blood flow declined with increasing adiposity of the fat depots, and a negative correlation was found between flow and fat-cell volume (r equals -.571, P less than .01). In contrast, when blood flow was expressed on the basis of fat-cell number (ml/108 fat cells/min), a positive and highly significant correlation was found between blood flow per fat cell and fat-cell volume (r equals .842, P less than .001). In the rabbit tissue the relationship of blood flow to fat-cell number and size was more predictable than the usual expression of flow in terms of tissue wet weight. Food deprivation for 18-24 h did not significantly alter these relationships. The results indicate that changes in adipose tissue composition and cellularity, resulting from growth and from accumulation of lipid in enlarging adipocytes, are important determinants of blood flow regulation to adipose tissue.
Neural inhibition of insulin secretion from the isolated canine pancreas
Authors: Miller RE
Published: December 2017

By using an isolated in situ, cross-perfused pancreas preparation, direct neural effects on the immunoreactive insulin secretion rate (ISR) were separated from blood-borne influences. Blood from a large, anesthetized "support" dog was perfused through the pancreas of a small, anesthetized "pancreas" dog. Both splanchnic nerves of the pancreas dog were cut above the diaphragm and stimulated simultaneously (10 Hz, 0.1-ms pulses, 5-15 mA) for three 10-min periods, twice before and once during a pancreatic arterial phentolamine infusion (10 or 20 mug/min). Splanchnic nerve section caused a transient increase whereas stimulation caused a decrease in ISR. Phentolamine infusion blocked this decrease. In control experiments, an epinephrine infusion (25 or 50 mug/kg per min) was made into the systemic circulation of the pancreas dog instead of the first and second neural stimulations. No decrease in ISR occurred. Later neural stimulation (in the absence of phentolamine) was accompanied by a decrease in the ISR in three of four dogs. Conclusions: the ISR can be inhibited by direct neural imput to the pancreas, and this inhibition is mediated by alpha-adrenergic receptors.
Permeability limitation in estimation of local brain blood flow with [14C]antipyrine
Authors: Eckman WW , Phair RD , Fenstermacher JD , Patlak CS , Kennedy C , Sokoloff L
Published: December 2017

Influence of capillary permeability on local cerebral blood flow (LCBF) estimated by the autoradiograhpic diffusible-indicator method was analyzed by computer simulation. Its influence increases with increasing flow. With normal perfusion rates in gray matter, capillary permeability coefficient x surface area (PS value) must exceed 0.12 cm3-s(-1)-g(-1) for estimated LCBF to attain 95% of true values in all structures. In white matter, with its lower perfusion rates, the PS value must exceed 0.035 cm3-s(-1)-g(-1) for equivalent accuracy. [14C]antipyrine, widely used in the LCBF technique, has a PS value below these values and leads to undersestimation of LCBF. Experimental studies in cats in which LCBF was measured with either [14C]antipyrine or the freely diffusible, radioactive gas, [131I]trifluoroiodomethane, demonstrated consistently lower estimates of LCBF with [14C]antipyrine than with the gas; the deviations in the various cerebral structures approximated those predicted by the theoretical analyses. These results suggest that the uptake of [14C]antipyrine by cerebral tissues is diffusion limited as well as flow limited, and it therefore is not an ideal tracer for the autoradiographic LCBF technique.
Stimulated amino acid imbalance and histidine transport in rat brain slices
Authors: Lutz J , Tews JK , Harper AE
Published: December 2017

Histidine concentration in the brain decreases rapidly when rats are fed a low protein diet in which an amino acid imbalance is created by addition of an amino acid mixture devoid of histidine. Competition for histidine transport into the brain was suggested as an explanation for this effect. Therefore, animo acid mixtures simulating composition of plasma from rats fed basal or histidine-imbalanced diets were added to media to evaluate their effects on uptake of histidine by brain slices during a 60-min incubation period. At the concentrations actually found in plasma, the unbalanced mixture decreased histidine uptake significantly more than did the basal mixture. Two distinct inhibition patterns were observed with different groups of amino acids: a linear decrease in histidine uptake with a mixture of the small neutral, hydroxyl, basic, and acidic amino acids, and a hyperbolic decrease with a mixture of large neutral amino acids, and a hyperbolic decrease with a mixture of large neutral amino acids. Inhibition of histidine transport by the complete mixtures reflected these two effects. Plasma patterns and concentrations of competitive amino acids as well as the concentration of histidine appear to be factors involved in decreasing histidine transport into the brain.
Catecholamine effects on cyclic AMP levels and ion secretion in rabbit ileal mucosa
Authors: Field M , Sheerin HE , Henderson A , Smith PL
Published: December 2017

Effects of catecholamines on cyclic AMP (cAMP) levels and ion fluxes were examined in isolated rabbit ileal mucosa. The base-line cAMP level was unaffected by epinephrine (Epi), norepinephrine (Norepi), and isoproterenol. The theophylline-augmented cAMP level was decreased slightly be Epi in one series of experiments but not in another. Propranolol did not enhance this effect. The increase in cAMP level produced by cholera toxin was almost completely reversed by addition of Epi or Norepi. This reversal was prevented by phenoxybenzamine. Epi also partially reversed the increase in cAMP level produced by prostaglandin E1. Effects of Epi on ion fluxes were determined following addition of secretagogues. Epi significantly decreased theophylline-induced but not cAMP or cholera toxin-induced Cl secretion. A decrease in short-circuit current was nonetheless observed in the latter two instances. The observed discrepancies between alpha-adrenergic effects on cAMP levels and ion fluxes suggest the following possibilities: 1) ion transport-related cAMP is only a small fraction of total mucosal cAMP; 2) cAMP-induced active ion secretion is only slowly reversible, or 3) effects of alpha-adrenergic stimuli on ion transport are not due to inhibition of cAMP accumulation.