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At least 1,135 records · Page 63Linked to original sources
PubMed1995

Mucus and alkali secretion in the rat duodenum: effects of indomethacin, N omega-nitro-L-arginine, and luminal acid.

BACKGROUND & AIMS: Duodenal mucus and bicarbonate secretion appear to play an essential role in the protection of the duodenum. The aim of this study was to examine duodenal bicarbonate and mucus secretion and the effects of cyclooxygenase inhibition, nitric oxide synthase inhibition, and luminal acid. METHODS: Duodenal mucus gel thickness was measured using microelectrodes during intravital microscopy in anesthetized rats. Bicarbonate secretion was measured using back-titration. RESULTS: A continuous layer of mucus with a mean thickness of 284 +/- 11 microns (n = 35) and a mean alkaline secretion of 0.18 +/- 0.01 mumol.cm-2.min-1 were found in untreated animals. Indomethacin decreased both mucus and bicarbonate secretion by about 35%. NO synthase inhibition with N omega-nitro-L-arginine reduced mucus secretion by about 21% but increased bicarbonate secretion by 39%. Exposure of the mucosal surface to 10 mmol/L HCI increased mucus secretion by 44% and bicarbonate secretion by 22%. CONCLUSIONS: The duodenal mucus layer is continuous. It can be easily removed, and new secretion can be followed. Duodenal mucus secretion is strongly stimulated by luminal acid and endogenous prostanoids and less markedly by NO, whereas bicarbonate secretion is stimulated by acid and endogenous prostanoids and inhibited by endogenous NO.

Acids↗
PubMed1977

Traumatic lesions of the duodenum.

Injuries of the duodenum are relatively uncommon on account of the organ's size and position. Since most of it is retroperitoneal, lesions involving it give rise to such subtle physical and radiological signs that the diagnosis is often overlooked in the early phase after injury. Twenty-six cases of duodenal injury are reviewed, 18 of which were due to penetrating wounds and the remaining 8 to blunt trauma. Anterior penetrating wounds were usually associated with other intraperitoneal lesions which caused more obvious physical signs and thus drew attention to the necessity for exploration. On the other hand, both blunt trauma and posterior stab wounds frequently caused isolated retroperitoneal duodenal lesions where the diagnosis was not evident on admission, but in which the insidious and progressive development of symptoms and signs drew attention to the need for laparotomy. Early repair combined with drainage of the retroperitoneal space resulted in a good result in 23 of 26 cases, 4 of whom, however, developed a temporary lateral duodenal fistula. Two of the 3 deaths were in patients who presented late and had associated pancreatic injuries while the third was due to an abdominal vascular injury.

Adolescent↗
PubMed1986

Biological activity of vitamin D metabolites and analogs: dose-response study of 45Ca transport in an isolated chick duodenum perfusion system.

We have previously reported that vascular perfusion of the normal vitamin D3-replete chick duodenum with physiological amounts of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] increases the unidirectional movement of 45Ca from the lumen to the venous effluent under conditions of normal (0.9 mM) Ca2+ concentrations in both the lumen and vascular perfusate [Endocrinology 115: 1476 1984)]. The purpose of the present study was to determine the dose responsivity of this perfused intestinal calcium transport system for 1,25(OH)2D3 and some structurally related congeners. The dose-response curve was biphasic for all compounds studied; for 1,25(OH)2D3 initial stimulation of transport was detected at only 30 pM [the plasma concentration of 1,25(OH)2D3 is normally 125 pM] while maximal stimulation was 154% above control at a concentration of 650 pM. Above 650 pM 1,25(OH)2D3 the stimulation fell off sharply and transport had returned to basal levels by 1.3 nM. The relative potency of the D homologs tested was respectively 1,25(OH)2D3: 10,000; 1-alpha-hydroxyvitamin D3: 400; 25-hydroxyvitamin D3: 200; 24R,25-dihydroxy-vitamin D3: 137; vitamin D3: 34; 5,6-trans-25-hydroxyvitamin D3: 3. These results establish the usefulness of the perfused intestinal calcium transport system to study the nongenomic actions of 1,25(OH)2D3 on intestinal calcium transport.

24,25-Dihydroxyvitamin D 3↗
PubMed1987

Co-existence of the enkephalinergic system and the melanotropinergic system in the rat duodenum shown by immunohistochemistry.

The immunohistochemical distribution of alpha-melanotropin (alpha-MSH) and Met-enkephalin (Met-ENK) immunoreactivities in the rat duodenum was examined by using immunofluorescence microscopy. Alternately staining of adjacent frozen serial sections with specific antisera directed to alpha-MSH or Met-ENK revealed that within a subpopulation of myenteric plexus perikarya alpha-MSH immunostaining co-exists with that of Met-ENK. Some myenteric plexus nerve fibres also contain both Met-ENK and alpha-MSH immunoreactivity. These findings might indicate that the genes encoding for the precursors of melanotropins (the pro-opiomelanocortin precursor) and enkephalin (the pro-enkephalin precursor) are generated from a common, large and single ancestor gene which remained conserved during evolution in the rat enteric nervous system.

Animals↗
PubMed1992

Pancreatic function following partial pancreatectomy and anastomosis of the pancreatic duct to the stomach or duodenum in dogs.

The effects of pancreatic duct anastomosis to stomach (stomach group) or duodenum (duodenal group) on pancreatic function were examined in dogs following two thirds pancreatectomy. Normal fasting blood glucose concentrations were maintained in both groups despite significant reductions in glucose tolerance in the stomach group, and reductions in fasting insulin and insulin peak response in both groups. Pancreatic exocrine function was significantly decreased in both groups, though plasma p-aminobenzoic acid (PABA) concentrations were generally higher in the duodenal group. A correlation was found between plasma trypsin-like immunoreactivity (TLI) and pancreatic weight. These results indicate that anastomosis of the pancreas to bowel can be undertaken with minimal postoperative complications and that the site of the anastomosis influences pancreatic function. They suggest that preservation of more than one third of the pancreas is required for optimal function. The complementary information provided by the PABA and TLI tests suggests their dual application will be clinically useful for the detection and characterisation of naturally occurring pancreatic diseases.

4-Aminobenzoic Acid↗
PubMed1979

Calcium containing lysosomes in the normal chick duodenum: a histochemical and analytical electron microscopic study.

Absorptive cells of the normal chick duodenum contain numerous supranuclear vesicular/vacuolar structures. By routine transmission electron microscopy, such structures are membrane bound and demonstrate a granular content. These vesicles appear to move laterally and eventually coalesce with the lateral plasma membrane (exocytosis). The granular contents are resistant to high temperature microincineration, thus revealing their mineral-containing nature. The granular vesicular matrix also stains intensely with osmium pyroantimonate EGTA chelation of pyroantimonate-stained vesicles selectively extracts the granules indicating a high concentration of calcium. X-ray microanalysis also demonstrates a significant intravesicular calcium localization. When tissues were incubated for the presence of acid phosphatase, the supranuclear vesicles were markedly positive for this lysosomal enzyme. A possible role for these calcium-containing lysosomes in the transcellular flux of calcium ions across the intestinal absorptive cell is discussed.

Acid Phosphatase↗
PubMed1984

Interaction between calcium and cadmium in the 1,25-dihydroxyvitamin D3 stimulated rat duodenum.

It has been suggested that calcium and cadmium compete for an intestinal transport system that is vitamin D dependent. To further test this hypothesis, the interaction between calcium and cadmium during transport in the duodenum of rat was investigated. Control rats maintained on a diet adequate in vitamin D, calcium, and phosphorus were compared to rats on the same diet administered 500 ng of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) 4 hr before transport measurement with everted sacs. Active transport of calcium was evident in control rats and was further stimulated by exogenous 1,25(OH)2D3. Added to mucosal bathing fluid 10 micron cadmium partially inhibited active calcium transport both in controls and in rats receiving 1,25(OH)2D3; 100 microM cadmium completely blocked active transport in both groups. Water transport was also inhibited by 10 and 100 microM cadmium. Cadmium uptake and transport were not affected by 1,25(OH)2D3. The accumulation of cadmium in mucosal tissue was significantly inhibited by 1 mM calcium, but there was no significant effect on uptake or transmural transport. The findings suggest that cadmium and calcium do not interact specifically at a 1,25(OH)2D3-dependent transport site. The interaction between calcium and cadmium in the duodenal mucosa could be related to the action of cadmium in blocking active transport processes.

Animals↗
PubMed1984

Effects of ciguatoxin and maitotoxin on isolated rat atria and rabbit duodenum.

Ciguatoxin and maitotoxin, extracted from a species of moray-eel, Gymnothorax javanicus, and from a wild dinoflagellate, Gambierdiscus toxicus, were tested on rat atria and rabbit duodenum. Biphasic inotropic and chronotropic responses with excitatory and inhibitory components were observed. The effects of agents such as reserpine, propranolol, phentolamine, atropine and manganese ions were investigated. We conclude that, at the dosage levels used, ciguatoxin acts mainly at the nerve endings, while maitotoxin exerts prominent toxic effects on muscles.

Animals↗
PubMed1986

Stimulation of HCO3- secretion by the prostaglandin E2 analog enprostil: studies in human stomach and rat duodenum.

This study investigated the action of enprostil, a synthetic analog of PGE2, on gastric HCO3- secretion in humans and on duodenal HCO3- secretion in the anesthetized rat. A previously validated 2-component model was used to calculate gastric HCO3- and H+ secretion in 10 human subjects. Compared to placebo, a single 70 micrograms oral dose of enprostil increased basal gastric HCO3- secretion from 1810 +/- 340 to 3190 +/- 890 mumol/hr (P less than 0.05). In addition, enprostil reduced basal gastric H+ secretion from 5240 +/- 1140 to 1680 +/- 530 mumol/hr (P less than 0.02). Enprostil also increased HCO3- secretion and reduced H+ secretion during intravenous pentagastrin infusion. In the rat, duodenal HCO3- secretion was measured by direct titration in situ using perfused segments of duodenum just distal to the Brunner gland area and devoid of pancreatic and biliary secretions. Addition of enprostil (10 micrograms/ml) to the duodenal bathing solution increased duodenal HCO3- secretion from 6.3 +/- 1.3 to 15.1 +/- 2.0 mumol/cm X hr (P less than 0.01, n = 6). The stimulatory action of enprostil on duodenal HCO3- secretion at 10 micrograms/ml was comparable in magnitude and duration to that of 10 micrograms/ml natural PGE2. In summary, the PGE2 analog enprostil stimulated gastroduodenal HCO3- secretion, effects which may be beneficial in protection of the gastroduodenal mucosa against luminal acid.

Adult↗
PubMed1986

Localization of Met-enkephalin-Arg6-Gly7-Leu8 immunoreactivity in rat duodenum.

The distribution of Met-enkephalin-Arg6-Gly7-Leu8 (Met-ENK-Arg6-Gly7-Leu8) in the rat duodenum was determined using specific antibodies against Met-ENK-Arg6-Gly7-Leu8 and the immunofluorescence microscope technique. Met-ENK-Arg6-Gly7-Leu8 immunoreactive perikarya have been detected in the myenteric plexus. These neuronal cell bodies were large in diameter and round in shape. Met-ENK-Arg6-Gly7-Leu8 immunostained nerve fibres were noted in both the circular muscle layer and, more abundantly, in interconnecting myenteric plexus nerve fibre bundles. These findings might indicate that Met-ENK-Arg6-Gly7-Leu8 has important physiological roles as neurotransmitter and/or neuromodulator in the human and mammalian gastrointestinal tract.

Animals↗
PubMed1982

The molecular nature of vascularly released cholecystokinin from the isolated perfused porcine duodenum.

Using sequence-specific radioimmunoassays, the quantities and molecular nature of cholecystokinin (CCK) have been determined in extracts of porcine duodenal mucosa and in the vascular perfusate from the isolated porcine duodenum. The basal concentration of CCK in the perfusate was 84 pM equiv. CCK-8 (mean; range: 32-173 pM, n = 5). After intraluminal stimulation with amino acids, acidified fat emulsions and hydrochloric acid, the concentrations increased 2--5-fold. Both in the basal and stimulated state the concentrations of the related hormone, gastrin, were below 5 pM equiv. gastrin-17. CCK in the perfusate was concentrated by affinity-chromatography using antibodies directed against the bioactive C-terminus. Subsequent gel chromatography revealed a form with a size like or slightly larger than the C-terminal dodecapeptide (CCK-12), a predominant form resembling the C-terminal octapeptide (CCK-8), and a form resembling the C terminal tetrapeptide (CCK-4). The duodenal mucosa contained in addition CCK-33, -39 and CCK-peptides with further N-terminal extensions. The results suggest that small CCK peptides are the principal circulating forms, while CCK-33 and larger forms are biosynthetic precursors.

Amino Acid Sequence↗
PubMed1983

Contribution of the antrum and duodenum to circulating forms of gastrin in the dog.

Gastrin release was stimulated in four anaesthetized dogs with meat extract and acetylcholine. The different forms of gastrin were analyzed in antral and duodenal mucosa and in blood from antral, duodenal and peripheral veins by use of radioimmunoassay with a region-specific antibody, Sephadex gel filtration, and SDS-gel electrophoresis. The duodenum contributed less than 4% of antral gastrin to circulating gastrin. The molecular forms of antral and duodenal gastrins were similar. On the basis of the electrophoretic results and the properties of the antibody, gastrin in the antral and duodenal veins consisted of a minor fraction of G 17 and a predominant fraction of C-terminal fragments of smaller molecular size. This fraction was even more marked in the peripheral venous circulation. In the peripheral blood, however, not only smaller forms of gastrin were present but also an increasing ratio of big gastrin immunoreactivity. Thus, there is active postsecretory processing of gastrin in the circulation of the anaesthetized dog.

Animals↗
PubMed1988

Effect of different calcium modulators on motilin-induced contractions of the rabbit duodenum. Comparison with acetylcholine.

Motilin and acetylcholine (ACh) have a direct contractile effect on rabbit small intestinal smooth muscle. To explore the role of calcium influx in these contractions, we studied the effect of extracellular calcium concentration and of calcium antagonists on the response of longitudinal muscle preparations from rabbit duodenum. Motilin- (10(-7) M) and ACh- (10(-4) M)-induced contractions were abolished in Ca2+-depleted medium. ACh (10(-4) M) or motilin (10(-8) and 10(-7) M) increased the contractile response to added Ca2+ to 130 +/- 6%, 129 +/- 10% and 145 +/- 5% of the maximal response to Ca2+ added alone (10 mM in a cumulative concentration response curve). The sensitivity to Ca2+ was greater in the presence of ACh and motilin (EC50 = 1.0 and 1.1 mM Ca2+) than in the absence of any agonist (1.7 mM). In cumulative concentration response (CCR) curves for motilin and ACh, pD2'-values were 7.0 and 6.6 for diltiazem, 8.4 and 7.8 for verapamil (two calcium entry blockers), 5.6 and 5.2 for TMB-8 (an inhibitor of intracellular calcium), 5.3 and 5.2 for TFP (a calmodulin-antagonist). All CCR-curves showed metactoid-like action of the antagonistic drugs. We conclude that ACh and motilin cause calcium to enter the smooth muscle cell. They are probably operating via separate channels, and use a mechanism which differs from K+-induced influx. Intracellular calcium stores appear to play a minor role in these contractions.

Acetylcholine↗
PubMed1990

The amino acid sequence of chymodenin, a hormone-like peptide from porcine duodenum, is identical to cytochrome C-oxidase, peptide VII.

The amino acid sequence of chymodenin, a hormone-like peptide from porcine duodenum is reported. The molecule is known to rapidly alter the proportions of digestive enzymes secreted by the rabbit pancreas in vivo and in vitro, by selection of the specific intra-pancreatic source from which the preset mixture of digestive enzymes is secreted. The sequence is identical to that of cytochrome C-oxidase peptide VII (cCoVII) from bovine heart, with the exception of a substitution of threonine for alanine at position 6 and a second substitution of alanine for threonine at position 71. Disulfide bridges link positions 29-64 and 39-53. cCoVII-chymodenin has a pentapeptide (-Ala-Glu-Gly-Thr-Phe-) near the carboxy-terminus which is immediately preceded by an -Arg-Arg- sequence in the porcine and bovine sequences of cCoVII. This peptide is identical to a pentapeptide found close to the amino terminus of the hormones gastric inhibitory peptide (GIP) and glucagon-like peptide I. The identity to cCoVII means chymodenin as isolated is itself unlikely to be a gastrointestinal hormone. However, the partial commonality of sequence with the glucagon-secretin family immediately adjacent to a pro-hormone-like activation site, and the specific actions on the exocrine pancreas, means that the molecule probably mimics the natural actions of an as-yet uncharacterized member of the glucagon family, which exerts a unique action on exocrine pancreatic secretion.

Amino Acid Sequence↗
PubMed1982

Thyroxine-stimulated synthesis of microvillus membrane glycoproteins during culture of chick embryonic duodenum.

The effect of thyroxine on biosynthesis of microvillus membrane glycoproteins has been investigated in organ culture of 18-day-old chick embryonic duodenum. Explants incorporate [3H]leucine and [3H]glucosamine continuously, and overall incorporation is enhanced by 10 nM thyroxine during 48 h of labeling; this increase in radioactivity is associated with vesicles released from the microvilli. Light microscope autoradiography, pulse labeling of brush border fragments, and pulse chase experiments reveal that [3H]glucosamine is incorporated into brush border at an increasing rate during culture, and that newly synthesized glycoproteins are discharged into the medium along with brush border enzymes (alkaline phosphatase and maltase). These results suggest that thyroxine stimulates biosynthesis of microvillus membrane glycoproteins, in addition to stimulating vesiculation of the membrane. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 3H-labeled vesicles and brush border fragments show that [3H]leucine and [3H]glucosamine are incorporated into proteins of high molecular weight. Two protein bands are identified as alkaline phosphatase and maltase. Thyroxine stimulates glycosylation of these enzymes, but does not change protein patterns. Radioactivity assay of alkaline phosphatase- and maltase-active gel slices suggests that thyroxine stimulation of these enzyme activities during culture is not correlated with de novo synthesis of these proteins.

Animals↗
PubMed1992

Investigation of a role for reduction in ferric iron uptake by mouse duodenum.

59Fe uptake rates by mouse duodenal fragments incubated in vitro were markedly reduced by non-permeable reagents, ferricyanide (oxidising agent) and ferrozine (Fe2+ chelator), in the medium; ferrocyanide had no effect. Reduction of Fe3+, as reflected by an increase in ferrozine-(Fe2+)-chelatable iron, was observed in the presence of the tissue fragments. The generation of Fe2+ occurred linearly with time, was independent of the medium ferrozine concentration, and was not due to release of reducing factors from the duodenal fragments. Fe(3+)-reducing activity was mainly present on the mucosal surface and was localised primarily to the proximal region of the small intestine. Changes in Fe3+ reduction rates closely parallelled the changes in duodenal 59Fe uptake, when metabolic inhibitors or modulators of membrane potential were included in the medium. The enhancement in duodenal mucosal 59Fe uptake in chronic hypoxic and iron-deficient mice parallelled the changes in the tissue reduction of medium Fe3+. Moreover, the rates of reduction were quantitatively similar to rates of uptake. These observations indicate that a sequential reduction and uptake process operates for Fe3+ uptake in mouse duodenum.

Animals↗
PubMed1993

Structural changes of duodenum brush border in lung cancer patients treated with cisplatin plus etoposide.

The effects of cisplatin plus etoposide chemotherapy (PE) on the structure of proximal intestine villi and brush border were investigated in 10 patients with lung cancer. The day before starting chemotherapy (time 1); 8 days after its initiation (time 2), and one month after the 3rd course of PE (time 3) they underwent esophagogastroduodenoscopy and three biopsies were taken from the descending duodenum. Intestinal villi were examined by light microscopy; brush border by transmission electron microscopy. No significant histological changes of villous pattern were observed at times 2 and 3. The height of microvilli was reduced in seven patients at time 2 (P < 0.05). Microvilli abnormalities (i.e. rarefaction and/or heterogeneity in their height) were present in nine patients at time 2 (P < 0.05). Brush border appearance at time 3 did not differ from that at time 1. PE chemotherapy seems to have short-term toxic effects on small intestine brush border, but does not cause chronic enteropathy.

Adult↗
PubMedDate not supplied

Alpha-neo-endorphin coexists with dynorphin-A(1-8) within intramurally lying perikarya of rat duodenum.

By the use of the immunofluorescent microscopic staining technique, adjacent serial sections through the rat duodenum were alternately stained with specific antisera directed to the opioid peptides alpha-neo-endorphin and dynorphin-A(1-8). alpha-Neo-endorphin immunoreactivity has been revealed exclusively within perikarya lying intramurally in the longitudinal muscle layer. These alpha-neo-endorphin and dynorphin-A(1-8) immunoreactive perikarya were large in diameter, round in shape, contained a large and round nucleus, and were recognized only occasionally there. alpha-Neo-endorphin immunoreactivity was coexistent with dynorphin-A(1-8)-positive material within these perikarya. Since no alpha-neo-endorphin material was detected within duodenal nerve fibres and terminals, it might be concluded that this peptide is further enzymatically cleaved to the opioid pentapeptide Leu-enkephalin during its axonal transport from intramural perikarya to nerve terminals and during its storage there.

Animals↗