bluuebunny/crossref_metadata_2025 huggingface dataset:
Human duodenal mucosal brush border Na+/H+exchangers NHE2 and NHE3 alter net bicarbonate movement
Authors: Repishti Maltin , Hogan Daniel L. , Pratha Vijaya , Davydova Laura , Donowitz Mark , Tse C. M. , Isenberg Jon I.
Published: December 2017

The proximal duodenal mucosa secretes HCO[Formula: see text] that serves to protect the epithelium from injury. In isolated human duodenal enterocytes in vitro, multiple luminal membrane proteins are involved in acid/base transport. We postulated that one or more isoforms of the Na+/H+exchanger (NHE) family is located on the apical surface of human duodenal mucosal epithelial cells and thereby contributes to duodenal mucosal HCO[Formula: see text] transport. Duodenal biopsies were obtained from human volunteers, and the presence of NHE2 and NHE3 was determined by using previously characterized polyclonal antibodies (Ab 597 for NHE2 and Ab 1381 for NHE3). In addition, proximal duodenal mucosal HCO[Formula: see text] transport was measured in humans in vivo in response to luminal perfusion of graded doses of amiloride; 10−5–10−4M amiloride was used to inhibit NHE2 and 10−3M amiloride to inhibit NHE3. Both NHE2 and NHE3 were localized principally to the brush border of duodenal villus cells. Sequential doses of amiloride resulted in significant, step-wise increases in net duodenal HCO[Formula: see text] output. Inhibition of NHE2 with 10−5M and 10−4M amiloride significantly increased net HCO[Formula: see text] output. Moreover, there was an additional, equivalent increase ( P < 0.05) in duodenal HCO[Formula: see text] output with 10−3M amiloride, which inhibited NHE3. We conclude that 1) NHE2 and NHE3 are localized principally to the brush border of human duodenal villus epithelial cells; 2) sequential inhibition of NHE2 and NHE3 isoforms resulted in step-wise increases in net HCO[Formula: see text]output; 3) NHE2 and NHE3 participate in human duodenal villus cell HCO[Formula: see text] transport; and 4) the contribution of NHE-related transport events should be considered when studying duodenal HCO[Formula: see text] transport processes.
Effects of substance P on identified neurons of the rat dorsal motor nucleus of the vagus
Authors: Lewis Mark W. , Travagli R. Alberto
Published: December 2017

Previous evidence suggests that substance P (SP) activates subpopulations of neurons within the dorsal motor nucleus of the vagus (DMV). In this study we aimed at identifying these subpopulations in relation to their gastrointestinal projection organs or vagal branches and characterizing pharmacologically the SP response. Using whole cell patch-clamp recordings from identified gastrointestinal-projecting vagal motoneurons, we found that SP induced an inward current in all neuronal groups except for cecum-projecting cells. The lowest percentage of SP-responding neurons was found in fundus-projecting cells, where SP also had a concentration-response curve that was shifted to the left ( P < 0.05). Independently from the projections, the SP response was reduced by sendide and MEN 10,376 and mimicked by a combination of [Sar9-Met(O2)11]SP and α-neurokinin. SP and α-neurokinin also increased the frequency, but not the amplitude, of postsynaptic currents. In conclusion, we demonstrated that SP induces both pre- and postsynaptic effects on DMV neurons via activation of neurokinin NK1 and NK2 receptors. The magnitude of the SP response was correlated to the peripheral target organ.
Pre- and postsynaptic inhibition by nociceptin in guinea pig small intestinal myenteric plexus in vitro
Authors: Liu Sumei , Hu Hong-Zhen , Ren Jun , Gao Chuanyun , Gao Na , Lin Zhong , Xia Yun , Wood Jackie D.
Published: December 2017

Actions of nociceptin on electrical and synaptic behavior of morphologically and neurochemically identified neurons in the guinea pig duodenal myenteric plexus were studied with conventional techniques. Nociceptin hyperpolarized the membrane potential in 104 of 121 AH-type and 28 of 51 S-type neurons with an EC50 of 11.9 ± 1.2 nM. Increased K+ conductance accounted for the hyperpolarizing responses that were blocked by pertussis toxin and unaffected by naloxone. The selective opioid receptor-like (ORL)1 receptor antagonist [Phe1-psi(CH2-NH)-Gly2]nociceptin(1–13)-NH2suppressed the nociceptin-evoked responses while behaving like a partial agonist. The nonselective ORL1 antagonist naloxone benzoylhydrazone competitively suppressed nociceptin actions with a pA2 value of 5.8. Nociceptin acted at presynaptic inhibitory receptors to suppress fast excitatory nicotinic postsynaptic potentials in 25 of 30 neurons (EC50 = 22.5 ± 4.4 nM) and slow synaptic excitation in 38 of 45 neurons (EC50 = 15.1 ± 1.6 nM). Presynaptic inhibitory action of nociceptin was unaffected by naloxone and was antagonized by [Phe1-psi(CH2-NH)-Gly2]nociceptin(1–13)-NH2or naloxone benzoylhydrazone. The results suggest that nociceptin acts both pre- and postsynaptically by activating an ORL1receptor that is distinct from typical naloxone-sensitive opioid receptors.
Polyamine depletion arrests growth of IEC-6 and Caco-2 cells by different mechanisms
Authors: Ray Ramesh M. , McCormack Shirley A. , Johnson Leonard R.
Published: December 2017

The polyamines spermidine and spermine and their precursor, putrescine, are required for the growth and proliferation of eukaryotic cells. This study compares and contrasts growth arrest caused by polyamine depletion in the untransformed IEC-6 cell line with that in the p53-mutated colon cancer Caco-2 cell line. Cells were grown in the presence or absence of α-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase, the first rate-limiting enzyme in the synthesis of polyamines. Depletion of polyamines inhibited the growth of both cell lines equally and over the same time frame. However, whereas IEC-6 cells were arrested in the G1 phase of the cell cycle, there was no accumulation of Caco-2 cells in any particular phase. In IEC-6 cells, growth arrest was accompanied by elevated levels of p53 and p21Waf1/Cip1 (p21). There were no changes in p53 levels in Caco-2 cells. Levels of p21 increased in Caco-2 cells on day 2 without any effect on cell cycle progression. The amount of cyclin-dependent kinase (Cdk)2 protein was unchanged by polyamine depletion in both cell lines. However, the activity of Cdk2 was significantly inhibited by DFMO in IEC-6 cells. These data suggest that in the untransformed IEC-6 cells the regulation of Cdk2 activity and progression through the cell cycle are p53- and p21 dependent. Growth arrest in the p53-mutated Caco-2 line after polyamine depletion occurs by a different, yet unknown, mechanism.
IV. GABAB receptors in the brain-gastroesophageal axis
Authors: Blackshaw L. Ashley
Published: December 2017

GABAB receptors are inhibitory G protein-coupled receptors that are commonly associated with presynaptic inhibition of transmitter release in the central nervous system. In the brain-gastroesophageal axis, a role has recently been demonstrated for GABAB receptors on extrinsic afferent endings within the stomach and esophagus, where they reduce mechanosensitivity. This action is compounded by inhibition of communication centrally from these afferents in the brain stem and within central circuits. There is a final peripheral action on the motor pathway where GABAB receptors reduce output of acetylcholine from vagal preganglionic motoneurons. These potent, multiple actions of GABAB receptors may have therapeutic benefit by reducing the triggering of transient lower esophageal relaxations, which are the major cause of gastroesophageal reflux. An important clinical application is therefore emerging for this recent discovery.
Downregulation of nuclear sex steroid receptor activity correlates with severity of alcoholic liver injury
Authors: Eagon Patricia K. , Elm Mary S. , Tadic Stasa D. , Nanji Amin A.
Published: December 2017

Chronic ethanol ingestion in rats and humans results in significant alterations in sex steroid levels and expression of sex hormone-dependent phenotype. In this study, we used the intragastric feeding model in male rats to determine hepatic sex hormone receptor activity under circumstances of chronic ethanol exposure and differing degrees of liver injury induced by type of dietary fat. Pathological analysis and quantitation of hepatic androgen receptor (AR) and estrogen receptor (ER) activity, serum sex hormones, and sex hormone-responsive protein and mRNA expression were performed. The activity of the physiologically relevant nuclear form of both AR and ER was significantly decreased with ethanol and correlated inversely with the severity of liver injury. Serum testosterone levels, as well as expression of an androgen-dependent hepatic mRNA, were decreased by ethanol and progressive liver injury. Serum estradiol increased with liver injury. We postulate that these changes in receptor activity may be due to the oxidative stress, reduced cellular energy, and/or altered cytokine milieu known to occur in this model.
Interrelationship between colonic muscularis mucosae activity and changes in transmucosal potential difference
Authors: Percy W. H. , Brunz J. T. , Burgers R. E. , Fromm T. H. , Merkwan C. L. , van Dis J.
Published: December 2017

This in vitro study investigated the relationship between rabbit colonic muscularis mucosae motor activity and changes in transmucosal potential difference. Spontaneous muscle contractions and potential difference oscillations occurred independently and were not neurally driven. ACh and histamine directly stimulated the muscularis mucosae, but their mucosal effects were largely indirect, suggesting that muscularis mucosae contractions promote epithelial secretion. 1,1-Dimethyl-4-phenyl-piperazinium iodide and vasoactive intestinal polypeptide induced large potential difference changes but small muscularis mucosae contractions, demonstrating mucosal secretion without significant muscle activity. Lowered intraluminal pH directly stimulated the muscle, whereas a bile salt-lipid mixture evoked TTX- and atropine-sensitive increases in its contractile activity. Increased intraluminal pressure and hypertonic luminal perfusion did not elicit muscularis mucosae excitation. Thus under basal conditions muscle and mucosal activities are independent, but evoked muscularis mucosae contractions can stimulate epithelial secretion. In response to specific luminal stimuli, muscularis mucosae motor activity is increased via the activation of cholinergic nerves. These data suggest that muscularis mucosae and mucosal functions are physiologically linked and that their activities can be coordinated by multiple mechanisms.
Molecular characterization and organ distribution of type A and B cholecystokinin receptors in cynomolgus monkey
Authors: Holicky Eileen L. , Hadac Elizabeth M. , Ding Xi-Qin , Miller Laurence J.
Published: December 2017

Differences in the molecular structure or organ distribution of receptors can limit the usefulness of a given species for drug studies. In this work, we have studied cholecystokinin (CCK) receptors in cynomolgus monkey, an animal model useful for preclinical testing. The type A CCK receptor cDNA was cloned and predicted to encode a 428 amino acid peptide that was 98% identical to the human receptor. Only 2 of the 10 residues that were distinct from the human receptor were not present in other cloned CCK receptor species. A Chinese hamster ovary cell line that stably expressed this receptor was developed. The cynomolgus receptor expressed in this environment was functionally indistinguishable from the human receptor, binding CCK with high affinity [inhibition constant ( K I) = 1.8 ± 0.5 nM] and exhibiting a potent intracellular calcium signaling response to this hormone (EC50 = 6.6 ± 2.1 pM). Like the human type A CCK receptor, this receptor was expressed prominently in monkey gallbladder and stomach and was expressed in low levels in brain and pancreas. The type B CCK receptor cDNA was cloned from stomach and brain (450 residue receptor that is 96% identical to the human receptor), where it was highly expressed yet was undetectable in gallbladder or pancreas. This work confirms the relevance of the cynomolgus species for preclinical testing of drugs acting on the type A CCK receptor.
Pancreatic phospholipase A2from the small intestine is a secretin-releasing factor in rats
Authors: Li James P. , Chang Ta-Min , Wagner David , Chey William Y.
Published: December 2017

A secretin-releasing activity exists in the upper small intestine and pancreatic juice in the rat and the dog. Group I pancreatic phospholipase A2(PLA2) in canine pancreatic juice and porcine pancreatic PLA2stimulate the release of secretin from both STC-1 cells and a secretin-producing cell (S cell)-enriched preparation isolated from rat duodenal mucosa. We investigated the distribution and release of pancreatic PLA2-like immunoreactivity in the gastrointestinal tract and the role of PLA2on the release of secretin and pancreatic exocrine secretion in response to duodenal acidification in anesthetized rats. PLA2-like immunoreactivity was detected in the mucosa throughout the gastrointestinal tract. High concentrations of PLA2were found in both the small intestine and the pancreas. Duodenal acidification significantly increased the release of PLA2from the upper small intestine (385% over basal secretion). Intravenous infusion of an anti-PLA2serum (anti-PLA2) dose-dependently inhibited the release of secretin and pancreatic exocrine secretion in response to duodenal acid perfusion. Preincubation of the concentrate of intestinal acid perfusate (10-fold) from donor rats with the anti-PLA2significantly suppressed its stimulation of secretin release and pancreatic exocrine secretion in recipient rats. We conclude that pancreatic PLA2also functions as a secretin-releasing factor in the small intestine that mediates acid-stimulated release of secretin in rats.
Gap junctions in gastrointestinal muscle contain multiple connexins
Authors: Wang Y. F. , Daniel E. E.
Published: December 2017

In the canine gastrointestinal tract, the roles that gap junctions play in pacemaking and neurotransmission are unclear. Using antibodies to connexin (Cx)43, Cx45, and Cx40, we determined the distribution of these connexins. Cx43 was present in all locations where structural gap junctions occur. Cx40 was also widely distributed in the circular muscle of the lower esophageal sphincter (LES), stomach, and ileum. Cx45 was sparsely distributed in circular muscle of the LES. In the interstitial cells of Cajal (ICC) networks of myenteric plexus, in the deep muscular and submuscular plexuses, sparse Cx45 and Cx40 immunoreactivity was present. In colon, immunoreactivity was found only in the myenteric and submuscular plexus and nearby circular muscle cells. No immunoreactivity was found in sites lacking structural gap junctions (longitudinal muscle, inner circular muscle of the intestine, and most circular muscle of the colon). Studies of colocalization of connexins suggested that in the ICC networks, some colocalization of Cx43 with Cx40 and/or Cx45 occurred. Thus gap junctions in canine intestine may be heterotypic or heteromeric and have different conductance properties in different regions based on different connexin compositions.
Enteral feeding decreases gut apoptosis, permeability, and lung inflammation during murine endotoxemia
Authors: Alscher Kurt T. , Phang P. Terry , McDonald Treena E. , Walley Keith R.
Published: December 2017

We tested the hypothesis that endotoxemia and fasting are associated with increased gut apoptotic activity, gut permeability, and inflammation in a distant organ. Fed or fasted CD-1 mice were studied 6 h after intraperitoneal injection of either saline (sham) or endotoxin (4 mg/kg of 0111:B4 Escherichia coli lipopolysaccharide). We found that endotoxin increased gut caspase-3 and -6 activity by 4.9 ± 0.6- and 4.5 ± 0.5-fold, respectively ( P < 0.001), and increased terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) staining of mucosal cells ( P< 0.05). Feeding decreased caspase-3 activity by 40% ( P< 0.05) and decreased endotoxin-induced TUNEL staining ( P< 0.05). Endotoxin increased gut poly(ADP-ribose) polymerase activity by 15% ( P < 0.05). Endotoxin increased gut permeability by 44% ( P < 0.05), an effect reduced 36% by feeding ( P < 0.05). Similarly, endotoxin increased pulmonary neutrophil infiltration (6.0 ± 1.0-fold, P< 0.001) and increased lung interleukin (IL)-6 (5.9 ± 0.1-fold, P < 0.001) and macrophage inflammatory protein (MIP)-2 expression (290 ± 40-fold, P < 0.001), whereas feeding decreased this effect by 43% for neutrophils, 40% for IL-6 ( P < 0.05), and 35% for MIP-2 ( P < 0.05). Thus endotoxin increases gut apoptotic activity, gut permeability, and pulmonary inflammation. Enteral feeding may decrease the distant organ inflammation by reducing gut apoptosis, thereby maintaining gut mucosal function during endotoxemia.
Mice with combined disruption ofGpx1andGpx2genes have colitis
Authors: Esworthy R. Steven , Aranda Richard , Martín Martín G. , Doroshow James H. , Binder Scott W. , Chu Fong-Fong
Published: December 2017

Glutathione peroxidase (GPX)-1 and gastrointestinal (GI) epithelium-specific GPX (GPX-GI), encoded by Gpx1 and Gpx2, provide most GPX activity in GI epithelium. Although homozygous mice deficient in either the Gpx1 or Gpx2 gene appeared to be normal under standard housing conditions, homozygous mice deficient in both genes, double-knockout (KO) mice, had symptoms and pathology consistent with inflammatory bowel disease. These symptoms included a high incidence of perianal ulceration, growth retardation that started around weaning, and hypothermia that resembled that observed in calorie-restricted mice, even though the double-KO mice in our study were allowed to eat ad libitum. The growth retardation and hypothermia were components of cachexia, which is fatal in a high percentage of mice. Histological examination revealed that the double-KO mice had a high incidence of mucosal inflammation in the ileum and colon but not in the jejunum. Elevated levels of myeloperoxidase activity and lipid hydroperoxides were also detected in colon mucosa of these homozygous double-KO mice. These results suggest that GPX is essential for the prevention of the inflammatory response in intestinal mucosa.
Local longitudinal muscle shortening of the human esophagus from high-frequency ultrasonography
Authors: Nicosia Mark A. , Brasseur James G. , Liu Ji-Bin , Miller Larry S.
Published: December 2017

We analyzed local longitudinal shortening by combining concurrent ultrasonography and manometry with basic principles of mechanics. We applied the law of mass conservation to quantify local axial shortening of the esophageal wall from ultrasonically measured cross-sectional area concurrently with measured intraluminal pressure, from which correlations between local contraction of longitudinal and circular muscle are inferred. Two clear phases of local longitudinal shortening were observed during bolus transport. During luminal filling by bolus fluid, the muscle layer distends and the muscle thickness decreases in the absence of circular or longitudinal muscle contraction. This is followed by local contraction, first in longitudinal muscle, then in circular muscle. Maximal longitudinal shortening occurs nearly coincidently with peak intraluminal pressure. Longitudinal muscle contraction begins before and ends after circular muscle contraction. Larger longitudinal shortening is correlated with higher pressure amplitude, suggesting that circumferential contractile forces are enhanced by longitudinal muscle shortening. We conclude that a peristaltic wave of longitudinal muscle contraction envelops the wave of circular muscle contraction as it passes through the middle esophagus, with peak longitudinal contraction aligned with peak circular muscular contraction. Our results suggest that the coordination of the two waves may be a physiological response to the mechanical influence of longitudinal shortening, which increases contractile force while reducing average muscle fiber tension by increasing circular muscle fiber density locally near the bolus tail.
HGF upregulates and modifies subcellular distribution of proteins in colon cancer cell enterocytic differentiation
Authors: Kermorgant Stéphanie , Dessirier Valérie , Lewin Miguel J. M. , Lehy Thérèse
Published: December 2017

Hepatocyte growth factor (HGF) and its receptor, c-Met, are involved in cell transformation. To study their role in intestinal cell differentiation, we used Caco-2 colon cancer cells, which differentiate spontaneously into enterocytes during culture. Cells grown continuously in the presence of HGF reached confluence more quickly than control cells. Markers of enterocytic differentiation, such as alkaline phosphatase and sucrase-isomaltase activities, adhesion molecules, and structural proteins such as E-cadherin, villin, and F-actin were upregulated by HGF throughout the 35 days of culture, and actin fibers were reorganized. HGF also stimulated expression and tyrosine phosphorylation of c-Met and Gab-1 as well as protein kinase C (PKC)-α expression. PKC-α has been shown to be involved in intestinal differentiation. We therefore investigated the possibility that increases in PKC-α protein levels were responsible for the HGF-promoted events. We did this by incubating cells with Gö-6976, an inhibitor of PKC-α and -β1, concomitantly with HGF. This inhibitor abolished the HGF-induced increase in villin levels before, but not after, confluence. Thus HGF accelerates Caco-2 cell differentiation and stimulates the metabolic and structural events accompanying this process. These HGF-promoted events may be mediated partly by Gab-1, and the effects of HGF on villin before confluence seem to involve PKC.
l-Histidine decarboxylase decreases its own transcription through downregulation of ERK activity
Authors: Colucci Rocchina , Fleming John V. , Xavier Ramnik , Wang Timothy C.
Published: December 2017

A poorly defined negative feedback loop decreases transcription of thel-histidine decarboxylase (HDC) gene. To help understand this regulation, we have studied the effect of HDC protein expression on HDC gene transcription in transfected AGS-B cells. Expression of the rat HDC protein inhibited HDC promoter activity in a dose-dependent fashion. The region of the HDC promoter mediating this inhibitory effect corresponded to a previously defined gastrin and extracellular signal-related kinase (ERK)-1 response element. Overexpression of the HDC protein reduced nuclear factor binding in this region. Experiments employing specific histamine receptor agonists indicated that the inhibitory effect was not dependent on histamine production, and studies with the HDC inhibitor α-fluoromethylhistidine revealed that inhibition was unrelated to enzyme activity. Instead, an enzymatically inactive region at the amino terminal of the HDC enzyme (residues 1–271) was shown to mediate inhibition. Fluorescent chimeras containing this domain were not targeted to the nucleus, arguing against specific inhibition of the HDC transcription machinery. Instead, we found that overexpression of HDC protein decreased ERK protein levels and ERK activity and that the inhibitory effect of HDC protein could be overcome by overexpression of ERK1. These data suggest a novel feedback-inhibitory role for amino terminal sequences of the HDC protein.
Intragastric pH regulates conversion from net acid to net alkaline secretion by the rat stomach
Authors: Coskun Tamer , Chu Shaoyou , Montrose Marshall H.
Published: December 2017

Our previous report showed gastric mucosal surface pH was determined by alkali secretion at intragastric luminal pH 3 but by acid secretion at intragastric pH 5. Here, we question whether regulation of mucosal surface pH is due to the effect of luminal pH on net acid/base secretions of the whole stomach. Anesthetized rats with a gastric cannula were used, the stomach lumen was perfused with weakly buffered saline, and gastric secretion was detected in the gastric effluent with 1) a flow-through pH electrode and 2) a fluorescent pH-sensitive dye (Cl-NERF). During pH 5 luminal perfusion, both pH sensors reported the gastric effluent was acidic (pH 4.79). After perfusion was stopped transiently (stop-flow), net acid accumulation was observed in the effluent when perfusion was restarted (peak change to pH 4.1–4.3). During pH 3 luminal perfusion, both pH sensors reported gastric effluent was close to perfusate pH (3.0–3.1), but net alkali accumulation was detected at both pH sensors after stop-flow (peak pH 3.3). Buffering capacity of gastric effluents was used to calculate net acid/alkaline secretions. Omeprazole blocked acid secretion during pH 5 perfusion and amplified net alkali secretion during pH 3 perfusion. Pentagastrin elicited net acid secretion under both luminal pH conditions, an effect antagonized by somatostatin. We conclude that in the basal condition, the rat stomach was acid secretory at luminal pH 5 but alkaline secretory at luminal pH 3.
Cloning and gastrointestinal expression of rat hephaestin: relationship to other iron transport proteins
Authors: Frazer David M. , Vulpe Christopher D. , McKie Andrew T. , Wilkins Sarah J. , Trinder Deborah , Cleghorn Geoffrey J. , Anderson Gregory J.
Published: December 2017

The membrane-bound ceruloplasmin homolog hephaestin plays a critical role in intestinal iron absorption. The aims of this study were to clone the rat hephaestin gene and to examine its expression in the gastrointestinal tract in relation to other genes encoding iron transport proteins. The rat hephaestin gene was isolated from intestinal mRNA and was found to encode a protein 96% identical to mouse hephaestin. Analysis by ribonuclease protection assay and Western blotting showed that hephaestin was expressed at high levels throughout the small intestine and colon. Immunofluorescence localized the hephaestin protein to the mature villus enterocytes with little or no expression in the crypts. Variations in iron status had a small but nonsignificant effect on hephaestin expression in the duodenum. The high sequence conservation between rat and mouse hephaestin is consistent with this protein playing a central role in intestinal iron absorption, although its precise function remains to be determined.
Role of gut flora on intestinal group II phospholipase A2activity and intestinal injury in shock
Authors: Rozenfeld Ranna A. , Liu Xueli , Deplaen Isabelle , Hsueh Wei
Published: December 2017

We previously showed that group II phospholipase A2(PLA2-II), a secretory, bactericidal, and proinflammatory protein in intestinal crypts, is upregulated after lipopolysaccharide (LPS) and platelet-activating factor (PAF) challenge. Here we examined whether germ-free environment (GF) or antibiotic treatment (ABX) affects the pathophysiological responses and intestinal PLA2-II activity after PAF (1.5 μg/kg) or LPS (8 mg/kg) injection. We found that LPS and PAF induced hypotension and mild intestinal injury in conventionally fed (CN) rats; these changes were milder in ABX rats, whereas GF rats showed no intestinal injury. PLA2-II enzyme activity was detected in normal rat small intestine; the basal level was not diminished in ABX or GF rats. PAF and LPS caused an increase in PLA2-II activity, which was abrogated in GF and ABX rats. Recolonization of GF rats by enteral contamination restituted their PLA2-II response to PAF and LPS and susceptibility to bowel injury. We conclude that PAF- and LPS-induced increases in PLA2-II activity are dependent on gut bacteria, and ABX and GF rats are less susceptible to LPS-induced injury than CN rats.
Mechanisms of reflexes induced by esophageal distension
Authors: Lang Ivan M. , Medda Bidyut K. , Shaker Reza
Published: December 2017

We investigated the mechanisms of esophageal distension-induced reflexes in decerebrate cats. Slow air esophageal distension activated esophago-upper esophageal sphincter (UES) contractile reflex (EUCR) and secondary peristalsis (2P). Rapid air distension activated esophago-UES relaxation reflex (EURR), esophago-glottal closure reflex (EGCR), esophago-hyoid distraction reflex (EHDR), and esophago-esophagus contraction reflex (EECR). Longitudinal esophageal stretch did not activate these reflexes. Magnitude and timing of EUCR were related to 2P but not injected air volume. Cervical esophagus transection did not affect the threshold of any reflex. Bolus diversion prevented swallow-related esophageal peristalsis. Lidocaine or capsaicin esophageal perfusion, esophageal mucosal layer removal, or intravenous baclofen blocked or inhibited EURR, EGCR, EHDR, and EECR but not EUCR or 2P. Thoracic vagotomy blocked all reflexes. These six reflexes can be activated by esophageal distension, and they occur in two sets depending on inflation rate rather than volume. EUCR was independent of 2P, but 2P activated EUCR; therefore, EUCR may help prevent reflux during peristalsis. All esophageal peristalsis may be secondary to esophageal stimulation in the cat. EURR, EHDR, EGCR, and EECR may contribute to belching and are probably mediated by capsaicin-sensitive, rapidly adapting mucosal mechanoreceptors. GABA-B receptors also inhibit these reflexes. EUCR and 2P are probably mediated by slowly adapting muscular mechanoreceptors. All six reflexes are mediated by vagal afferent fibers.
Myogenic NOS and endogenous NO production are defective in colon from dystrophic (mdx) mice
Authors: Mulè Flavia , Vannucchi Maria Giuliana , Corsani Letizia , Serio Rosa , Faussone-Pellegrini Maria Simonetta
Published: December 2017

The aim of the present study was to evaluate whether alterations in the distribution and/or function of nitric oxide synthase (NOS) could be involved in the development of the spontaneous mechanical tone observed in colon from dystrophic ( mdx) mice. By recording the intraluminal pressure of isolated colon from normal mice, we showed that Nω-nitro- l-arginine methyl ester (l-NAME) increased the tone, even in the presence of tetrodotoxin. The effect was prevented by l-arginine, nifedipine, or Ca2+-free solution. In colon from mdx mice, l-NAME was ineffective. Immunohistochemistry revealed that the presence and distribution of neuronal (nNOS), endothelial, and inducible NOS isoforms in smooth muscle cells and neurons of colon from mdx mice were the same as in controls. However, the expression of myogenic nNOS was markedly reduced in mdx mice. We conclude that there is a myogenic NOS in mouse colon that can tonically produce nitric oxide to limit influx of Ca2+through L-type voltage-dependent channels and modulate the mechanical tone. This mechanism appears to be defective in mdx mice.
Capsaicin vanilloid receptor-1 mediates substance P release in experimental pancreatitis
Authors: Nathan Jaimie D. , Patel Akash A. , McVey Douglas C. , Thomas Jean E. , Prpic Veronica , Vigna Steven R. , Liddle Rodger A.
Published: December 2017

We examined whether the capsaicin vanilloid receptor-1 (VR1) mediates substance P (SP) release from primary sensory neurons in experimental pancreatitis. Pancreatitis was achieved by 12 hourly injections of caerulein (50 μg/kg ip) in mice. One group received capsazepine (100 μmol/kg sc), a competitive VR1 antagonist, at 4-h intervals. Neurokinin-1 receptor (NK1R) internalization in acinar cells, used as an index of endogenous SP release, was assessed by immunocytochemical quantification of NK1R endocytosis. The severity of pancreatitis was assessed by measurements of serum amylase, pancreatic myeloperoxidase (MPO) activity, and histological grading. Caerulein administration caused significant elevations in serum amylase and pancreatic MPO activity, produced histological evidence of pancreatitis, and caused a dramatic increase in NK1R endocytosis. Capsazepine treatment significantly reduced the level of NK1R endocytosis, and this was associated with similar reductions in pancreatic MPO activity and histological severity of pancreatitis. These results demonstrate that repeated caerulein stimulation causes experimental pancreatitis that is mediated in part by stimulation of VR1 on primary sensory neurons, resulting in endogenous SP release.
Increased severity of alcoholic liver injury in female rats: role of oxidative stress, endotoxin, and chemokines
Authors: Nanji Amin A. , Jokelainen Kalle , Fotouhinia Maryam , Rahemtulla Amir , Thomas Peter , Tipoe George L. , Su Grace L. , Dannenberg Andrew J.
Published: December 2017

Alcoholic liver injury is more severe and rapidly developing in women than men. To evaluate the reason(s) for these gender-related differences, we determined whether pathogenic mechanisms important in alcoholic liver injury in male rats were further upregulated in female rats. Male and age-matched female rats (7/group) were fed ethanol and a diet containing fish oil for 4 wk by intragastric infusion. Dextrose isocalorically replaced ethanol in control rats. We analyzed liver histopathology, lipid peroxidation, cytochrome P-450 (CYP)2E1 activity, nonheme iron, endotoxin, nuclear factor-κB (NF-κB) activation, and mRNA levels of cyclooxygenase-1 (COX-1) and COX-2, tumor necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2). Alcohol-induced liver injury was more severe in female vs. male rats. Female rats had higher endotoxin, lipid peroxidation, and nonheme iron levels and increased NF-κB activation and upregulation of the chemokines MCP-1 and MIP-2. CYP2E1 activity and TNF-α and COX-2 levels were similar in male and female rats. Remarkably, female rats fed fish oil and dextrose also showed necrosis and inflammation. Our findings in ethanol-fed rats suggest that increased endotoxemia and lipid peroxidation in females stimulate NF-κB activation and chemokine production, enhancing liver injury. TNF-α and COX-2 upregulation are probably important in causing liver injury but do not explain gender-related differences.
Molecular characterization of volume-sensitive SKCachannels in human liver cell lines
Authors: Roman Richard , Feranchak Andrew P. , Troetsch Marlyn , Dunkelberg Jeffrey C. , Kilic Gordon , Schlenker Thorsten , Schaack Jerome , Fitz J. Gregory
Published: December 2017

In human liver, Ca2+-dependent changes in membrane K+permeability play a central role in coordinating functional interactions between membrane transport, metabolism, and cell volume. On the basis of the observation that K+conductance is partially sensitive to the bee venom toxin apamin, we aimed to assess whether small-conductance Ca2+-sensitive K+(SKCa) channels are expressed endogenously and contribute to volume-sensitive K+efflux and cell volume regulation. We isolated a full-length 2,140-bp cDNA (hSK2) highly homologous to rat brain rSK2 cDNA, including the putative apamin-sensitive pore domain, from a human liver cDNA library. Identical cDNAs were isolated from primary human hepatocytes, human HuH-7 hepatoma cells, and human Mz-ChA-1 cholangiocarcinoma cells. Transduction of Chinese hamster ovary cells with a recombinant adenovirus encoding the hSK2-green fluorescent protein fusion construct resulted in expression of functional apamin-sensitive K+channels. In Mz-ChA-1 cells, hypotonic (15% less sodium glutamate) exposure increased K+current density (1.9 ± 0.2 to 37.5 ± 7.1 pA/pF; P < 0.001). Apamin (10–100 nM) inhibited K+current activation and cell volume recovery from swelling. Apamin-sensitive SKCachannels are functionally expressed in liver and biliary epithelia and likely contribute to volume-sensitive changes in membrane K+permeability. Accordingly, the hSK2 protein is a potential target for pharmacological modulation of liver transport and metabolism through effects on membrane K+permeability.
Endothelin receptor blockers reduce I/R-induced intestinal mucosal injury: role of blood flow
Authors: Oktar Berna K. , Gülpinar M. Ali , Bozkurt Ayhan , Ghandour Salah , Çetinel Şule , Moini Hadi , Yeğen Berrak Ç. , Bilsel Serpil , Granger D. Neil , Kurtel Hizir
Published: December 2017

The aim of the present study was to assess the role of endothelin (ET) in ischemia-reperfusion (I/R)-induced mucosal injury. Mucosal permeability (51Cr-EDTA clearance) and tissue myeloperoxidase (MPO) activity were significantly increased after 30 min of ischemia followed by 30 min of reperfusion. The I/R-induced increases in mucosal permeability and polymorphonuclear leukocyte (PMN) infiltration were significantly attenuated by pretreatments with ETA (BQ-485) and/or ETB (BQ-788) receptor antagonists. Monoclonal antibody (MAb) directed against intercellular adhesion molecule-1 (ICAM-1; MAb 1A29) and superoxide dismutase (SOD) pretreatments significantly attenuated the increased mucosal permeability and PMN infiltration in a similar manner as with ET receptor antagonists. Superior mesenteric artery blood flow was significantly reduced during the reperfusion period. Both ET receptor antagonists caused a significant rise in blood flow compared with an untreated I/R group. In conclusion, our data suggest that ETA and/or ETB receptors, ICAM-1, and superoxide play an important role in I/R-induced mucosal dysfunction and PMN infiltration. Furthermore, ET is involved in the pathogenesis of postreperfusion-induced damage and beneficial effects of ET receptor antagonism are related to an improvement of disturbed blood flow during the reperfusion period.
Opposing central and peripheral effects of atropine on parasympathetic cardiac control
Authors: Katona P. G. , Lipson D. , Dauchot P. J.
Published: December 2017

Cardiac vagal efferent (CVE) activity was recorded from fine strands of the cervical vagus of chloralose-urethane-anesthetized dogs weighing an average of 14.6 kg. In spontaneously breathing animals atropine sulfate in doses of 0.003-1.5 mg significantly increased CVE activity even when the activity was corrected for changes in blood pressure. A 50% average increase (P less than 0.001) in mean activity was observed at a dose of 0.15 mg. The increase was not abolished by vagotomy as long as the animals were allowed to breathe spontaneously. The peripheral effect of atropine was characterized by the relationship between CVE activity and measured heart period changes. A 50% peripheral blockade was achieved at a dose of 0.06 mg; a dose of 1.0 mg produced essentially complete (greater than 90%) blockade. The results quantitatively demonstrate that atropine exerts a powerful central stimulating effect on CVE activity while simultaneously blocking vagal heart rate effects at the periphery.
Mechanism of action of isoproterenol on venous return
Authors: Green J. F.
Published: December 2017

The systemic vascular effects of isoproterenol infused in a dose of 1 mug-kg-1-min-1 was studied in 10 anesthetized dogs. A right heart bypass preparation allowed the separation of venous return into splanchnic and extrasplanchnic flows. Each channel was drained by gravity into an external reservoir. Venous return was then pumped into the pulmonary artery. During the infusion of isoproterenol, the pump was set at sufficient speed to maintain a constant level of blood in the external reservoir. Venous resistances and compliances of both channels were calculated from transient and steady-state volume shifts that occurred after rapid drops in splanchnic and then extrasplanchnic venous pressures. Isoproterenol affected both arterial and venous systems. Venous return increased from 1.62+/-0.11 to 2.40+/-0.19 liter/min (P less than 0.001) while arterial pressure fell from 97.5+/-3.8 to 70.2+/-5.9 mmHg (P less than 0.01). The compliances of the splanchnic and extrasplanchnic channels did not change significantly from their control values of 0.025+/-0.004 and 0.024+/-0.002 liter/mmHg. The venous resistance of the extrasplanchnic channel also did not change from its control value of 5.0 mmHg-liter-1-min-1; however, the splanchnic venous resistance decreased from 16.3+/-3.2 to 9.4+/-2.8 mmHg-liter-1-min-1 (P less than 0.001). The effective splanchnic back pressure, estimated by measuring the level to which hepatic venous pressure had to be raised to cause a change in portal pressure, decreased from 3.9 to 3.0 mmHg (P less than 0.01).
Function of lateral reticular nucleus in central cardiovascular regulation in the cat
Authors: Thomas M. R. , Ulrichsen R. F. , Calaresu F. R.
Published: December 2017

The role of the lateral reticular nucleus (LRN) in central cardiovascular regulation was investigated in cats. In 15 cerebellectomized and nine intact chloralosed cats stimulation of 115 histologically verified sites in the LRN elicited increases in arterial pressure and heart rate; the latter was abolished by propranolol but not by bilateral cervical vagotomy. The pressor response was significantly greater in intact animals. Electrical activity was recorded from the right inferior cardiac nerve (ICN) during stimulation fo the LRN and of a vasomotor region in the posteromedial hypothalamus (PMH). Stimulation of sites in the LRN and in the PMH, on both sides, elicited a response in the right ICN that was consistently abolished during baroreceptor excitation. Medullary transection 3 mm rostral to the LRN did not abolish the ICN response to LRN stimulation. The conclusions are drawn that stimulation of the LRN elicits cardiovascular responses probably due to excitation of groups of neurons in this nucleus located in a descending sympathetic pathway originating in the PMH and that these responses can be inhibited by excitation of baroreceptors. In view of the known functional connections of the LRN with the somatomotor system it is suggested that this nucleus may play a major role in somatosympathetic reflexes.
Carbon monoxide uptake and elimination in fetal and maternal sheep
Authors: Longo L. D. , Hill E. P.
Published: December 2017

We studied the relation of carboxyhemoglobin concentration in the fetus, [HbCOf], to that of the pregnant mother, [HbCOm], and inspired CO concentrations in unanesthetized sheep. We exposed ewes with catheters chronically implanted in maternal and fetal blood vessels to varying inspired CO concentrations. At 30 parts per million (ppm) CO, [HbCOm] increased from base-line levels of about 1.1% to about 4.6% over a course of 8-10 h. [HbCOf] increased more slowly from base-line values of 1.8% to steady-state values of 7.4% by 36-48 h. At 50 ppm, steady-state [HbCOm] = 7.2% and [HbCOf] = 11.3%. At 100 ppm, steady-state [HbCOm] = 12.2%, [HbCOf] = 19.8%. The increase in [HbCOm] resembled a simple exponential process with a half-time of 1.5 h. The time for [HbCOf] to reach half its final value was 5 h. The decay curve for CO elimination showed similar reactions, with fetal washout occurring slower than in the mother. Elevated [HbCOf] significantly decreased the PO2 values in the fetal descending aorta and inferior vena cava. These decreases in PO2 values can cause hypoxia and fetal death.
Androgen-mediated sensitivity in platelet aggregation
Authors: Johnson M. , Ramey E. , Ramwell P. W.
Published: December 2017

Platelet responsiveness to an aggregating stimulus (ADP) was greater (X10) in male than in female rats. Castration reduced aggregability in males (X4) and increased it in females (X3). Pretreatment with testosterone (1 mg/kg, sc) enhanced platelet aggregability in both sexes and restored the diminished responsivity observed in castrated males. Incubation of platelets with testosterone (1-10 ng/ml) potentiated rat (18.0 +/- 1.5%) and guinea pig (40.0 +/- 5.0%) aggregability when compared with vehicle-treated platelets. Estradiol (1 mg/kg, sc) in vivo or estradiol, progesterone, and deoxycorticosterone (1 microng/ml) in vitro had the opposite effect and decreased aggregability. The rank order of effectiveness of androgens in vitro was dihydrotestosterone, testosterone, methyltestosterone, androstendione, and androsterone, which correlates with their androgenicity. The effect of androgens was antagonized in vitro by the antiandrogen (Flutamide) and by estradiol. These data suggest that gonadal steroids may play a role in regulating platelet function in the rat and guinea pig.
Effect of arterial carbon dioxide on cerebral blood flow in ducks
Authors: Grubb B. , Mills C. D. , Colacino J. M. , Schmidt-Nielsen K.
Published: December 2017

The purpose of this study was to determine the effect of arterial PCO2 on blood flow to the avian brain. Cerebral blood flow was measured on curarized, artificially ventilated Pekin ducks by the rate at which intra-arterially injected xenon-133 was cleared from the duck's brain. A two-component clearance curve resulted: the blood flow calculated from the fast and slow components was similar to the blood flow to mammalian grey and white matter, respectively. Hypercapnia markedly increased the fast component of blood flow, whereas hypocapnia had no effect on this component. These effects were not due to changes in blood pressure, which was independent of arterial PCO2. Blood flow calculated from the slow component was independent of arterial PCO2. We conclude that the lack of response to hypocapnia may contribute to the exceptional tolerance of birds to high altitude by maintaining normal cerebral blood flow.
Function of human platelets during extracorporeal circulation
Authors: Hennessy V. L. , Hicks R. E. , Niewiarowski S. , Edmunds L. H. , Colman R. W.
Published: December 2017

The interaction between human platelets and nonbiologic surfaces was studied during in vitro recirculation of 500 ml of fresh, heparinized human blood in four different perfusion circuits. Circuits differed in surface area (0.1 m2 or 0.9 m2) and in surface composition. No important differences were observed between standard silicone-rubber and filler-free, silicone-rubber surfaces. Platelet counts decreased to 85% of control in 0.1- m2 circuits, but retained normal sensitivity to aggregating agents and released only small amounts of platelet factor 4 (PF4). In contrast, platelet counts in 0.9-m2 circuits decreased to 20% of control within 2 min and platelet sensitivity was depressed out of proportion to the fall in platelet count. Plasma PF4 progressively increased and platelet PF4 content progressively decreased during 6 h of recirculation. The results indicate that human platelets may exist in three conditions during extracorporeal circulation. Some platelets are unaltered, some are less sensitive to aggregating agents, and others have undergone extensive release. The ratio of blood volume to surface area appears to be an important determinant of platelet-surface interaction.
Contractile stimuli in collecting lymph vessels
Authors: Hargens A. R. , Zweifach B. W.
Published: December 2017

Contractility was investigated in collecting lymph vessels of rat and guinea pig mesentery. Lymphatic diameter and micropressure were simultaneously recorded under normal conditions and during micromanipulation of intralymphatic pressure. Spontaneous activity involved characteristic changes in intralymphatic pressure coincident with opening and closure of upstream and downstream valves. Contractions were irregular but still predictable by noting the trend of intraluminal pressure as it approached a threshold level. Mechanical obstruction upstream of lymph vessels reduced lymph pressure and contraction frequency. Microinjection or withdrawal of fluid caused contraction frequency. Microinjection or withdrawal of fluid caused contraction frequency to rise and fall, respectively. Contraction rate was not affected by the level of general anesthesia. Lymphatic wall tension, as calculated from pressure-radius variables, correlated well with contraction frequency, suggesting a myogenic origin for the contractile mechanism. However, lymphatic smooth muscle may be inherently unstable since some contractility persists despite an absence of pressure stimuli.