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Query: HUMANGGP:036187 (gut)
 73,132 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Stripped duodenal mucosa of rabbits was mounted in Ussing chambers containing a Ringer solution gassed with 100% O2. The disappearance of acid or alkali from the mucosal solution of short-circuited tissue was measured with a pH stat while the serosal pH was kept at 7.4. The duodenum rapidly disposed of both acid and alkali; neither property was altered by gassing with N2 while iodoacetate was in the perfusing solutions. Prevention of release of CO2 from the mucosal chamber obliterated the early rapid phase of acid disposal by the mucosa while a similar maneuver in the serosal chamber increased the appearance of serosal acid without altering the rate of acid disposal. Gut sacs of rabbit duodenum in vitro and in vivo showed a positive correlation between acid disposal and the rate of luminal CO2 production. While acid disposal progressively decreased with time for the in vitro gut sacs, the in vivo gut sac showed no fatigue in this respect. Luminal acidification in the Ussing chamber was associated with a profound reduction in short-circuit current (Isc), partially reversible by elevation of the mucosal pH but not by luminal glucose. Our data suggest that acid disposal occurs in part by intraluminal neutralization and in part by diffusion into the mucosa.
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PMID:Mechanisms of disposal of acid and alkali in rabbit duodenum. 0 19

The ability of the gut to inactivate various amines by oxidative deamination was tested with a 130-fold purified amine oxidase preparation from dog small intestine. Of 34 amines tested, putrescine, benzylamine, cadaverine, and serotonin were the most favourable substrates. Histamine was inactivated rapidly by this enzyme preparation, too. Histamine derivatives methylated at the imidazole nucleus were also deaminated, whereas Nalpha-methylhistamine was only a poor substrate and Nalpha, Nalpha-dimethylhistamine was not a substrate at all. Using a second procedure for the purification of amine oxidases from gut, the separation of a soluble monoamine oxidase from diamine oxidase was achieved by gel filtration on Sephadex G-200. The diamine oxidase deaminated putrescine (Km = 1.3 x 10(-4)M) and histamine (Km = 6.6 x 10(-5)M), but not serotonin, and was inhibited by aminoguanidine, but not by pargyline. The soluble monoamine oxidase inactivated serotonin (Km = 4.5 x 10(-4)M), but not histamine and putrescine and was inhibited by pargyline, but not by aminoguanidine. It was concluded that in dog small intestine (as well as in rabbit small intestine) only diamine oxidase was capable of inactivating histamine by oxidative deamination.
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PMID:Oxidative deamination of biogenic amines by intestinal amine oxidases: histamine is specifically inactivated by diamine oxidase. 0 28

From all mammals investigated so far only in rabbits diamine oxidase could not be detected in any tissue except the gut. Thus this species was chosen for studying the physiological and pathophysiological function of this enzyme in the gastrointestinal tract. By gel filtration on Sephadex G 50 and G 200 the enzyme was purified 100-fold, separated from a soluble monoamine oxidase, and the properties of the two enzymes were determined. Diamine oxidase from rabbit small intestine deaminated putrecine (Km = 1.3 times 10(-4) M, pH-optimum 6.4-6.9) and histamine (Km = 8 times 10(-5) M, pH-optimum 7.5), but not serotonin, and was inhibited by aminoguanidine, but not by pargyline. Soluble monoamine oxidase from rabbit small intestine catabolized serotonin (Km = 1.8 times 10(-4) M, pH-optimum 8.8) but not putrescine and histamine, and was inhibited by pargyline, but not by aminoguanidine. Based on its properties in vitro intestinal diamine oxidase could inactivate the vasoactive biogenic amine histamine in vivo. To confirm this hypothesis, in rabbits the small intestine was damaged severely by inducing total intestinal ischemia, which occurs as mesenteric infarction also in human subjects and is accompanied by histamine release. Treatment with aminoguanidine and ischemia killed the animals 3-times faster than ischemia alone, which supported our hypothesis on a protective role of intestinal diamine oxidase against histamine.
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PMID:Diamine oxydase in rabbit small intestine: separations from a soluble monoamine oxidase, properties and pathophysiological significance in intestinal ischemia. 0 54

The effect of three polyene macrolides, candicidin, amphotericin B and nystatin on the absorption of [3H] cholesterol was studied in the rat by using the in situ gut loop perfusion technique. Chronic treatment with candicidin and its presence at various concentrations in the gut loop perfusion experiments inhibited [3H] cholesterol absorption although a smaller effect was also obtained with amphotericin B and nystatin at higher concentrations. A similar but much less pronounced action of candicidin was also observed on the absorption of [3H] corticosterone and [14C] phenytoin.
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PMID:The effect of some polyene macrolides on absorption from the small intestine in the rat. 0 50

Subjects deficient in lactase may experience bloating, cramps and diarrhoea after ingesting milk, due to the unhydrolysed and poorly-absorbed lactose. The diarrhoea may result from an osmotic effect of the lactose itself or its poorly-absorbed acidic products of fermentation (Weijers, van de Kamer & others, 1961; Christopher & Bayless, 1971), possibly together with an alteration of sodium and water absorption due to the lowered colonic pH (Rousseau & Sladen, 1971). Laxation by lactulose (1-4-beta-galactosidofructose) may operate through an analogous mechanism. The drug is a synthetic dissaccharide which, in oral doses of 10-20 g, relieves chronic constipation (Wesselius-de Casparis, Braadbaart & others, 1968). It is neither hydrolysed by intestinal dissaccharidase (Dahlqvist & Gryboski, 1965) nor absorbed in the gut, but it is converted in the colon mainly to lactic and acetic acids by various bacteria including Lactobacillus acidophilus. Apart from the increased osmotic effect, the pH in the proximal colon falls markedly (Bown, Gibson & others, 1974), and larger doses may reduce stool pH. Weijers & others (1961) inferred that the acidic products formed from lactose in the colon stimulate propulsion, and K.S. Liem (Philips-Duphar) suggested to us that lactulose may relieve constipation partly by stimulation of propulsion due to the lowered pH. The experiments described below support this view.
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PMID:Intestinal pH and propulsion: an explanation of diarrhoea in lactase deficiency and laxation by lactulose. 0 91

The absorption of acetazolamide suspensions from in situ rat gastric and intestinal loop segments was studied. In 1 hr, 66.2 and 64.3% remained unabsorbed from the rat stomach and intestine, respectively. Although 1% (w/v) reduced glutathione and 1% (w/v) (24 mM) edetate disodium had no effect on gastric absorption, drug absorption from the rat intestine (1 hr) was increased 1.5 and 2 times, respectively. It was hypothesized that the relatively poor intestinal absorption was due primarily to the formation of a pH-dependent (pH 4.5-10), nonabsorbable complex between acetazolamide and carbonic anhydrase present in the gut and that reduced glutathione acted as an inhibitor to promote intestinal absorption. Equilibrium dialysis studies showed that reduced glutathion could reduce the fraction of drug bound to human carbonic anhydrase B by one-half when present in a molar ratio 10 times that of acetazolamide; edetate disodium had no effect on the in vitro binding. It was, therefore, assumed that edetate disodium promoted an increase in intestinal absorption by altering the permeability of intestinal epithelium. Based upon present experimentation, however, the alteration of intestinal epithelium by reduced glutathione cannot be ruled out.
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PMID:Effect of edetate disodium and reduced glutathione on absorption of acetazolamide from GI tract of rats. 0 73

The anatomy of the pharynx of Caenorhabditis elegans has been reconstructed from electron micrographs of serial sections. The pharynx is used for pumping food into the gut, and is composed of 34 muscle cells, 9 marginal cells, 9 epithelial cells, 5 gland cells and 20 neurones. Three regions of specialization in the cuticle lining of the pharyngeal lumen may aid in the accumulation of food particles. A basement membrane isolates the pharynx from the rest of the animal, making the pharyngeal nervous system a nearly self-contained unit which is composed primarily of five classes of motor neurones and six classes of interneurones. Three other classes have also been described, which by their morphology appear to be neurosecretory and motor, motor and interneuronal, and lastly one pair that only innervates three of the marginal cells. Some classes of neurone have free endings just under the cuticle lining the lumen of the pharynx, suggesting that these are mechano- or proprio-receptive endings. The connectivity of these neurones has been described at the level of individual synaptic regions, and after combining this information with video taped observations of the pharynx pumping, some interpretations of how these neurones function have been offered.
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PMID:The pharynx of Caenorhabditis elegans. 0 5

1. The enzyme beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) from the gut contents of active Achatina achatina exists in two molecular forms, beta-glucosidase C (mol.wt. about 82000) and D (mol.wt. about 41000). 2. Only the lower-molecular-weight species was found in the gut contents of aestivating snails or in extracts from their digestive glands and washed gut walls. 3. On re-activation of some aestivating snails, betion of ATP and Mg2+ to the isolated gut contents or to extracts from washed gut walls led to the formation of higher-molecular-weight forms of the enzyme, beta-glucosidase A (mol.wt. about 329000) and beta-glucosidase B (mol.wt. about 165000). 5. All these forms of the enzyme have similar pH optimum (pH 5.0-5.6). 6. The Michaelis constants (Km) and heat stability of the enzyme increased with increasing molecular complexity.
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PMID:The beta-glucosidase in the gut contents of the snail Achatina achatina. 0 70

Somatostatin, a growth hormone release-inhibiting factor, isolated originally from the hypothalamus, has been shown to have widespread effects on brain and endocrine and exocrine pancreatic and gut function. Furthermore, it has a widespread distribution in the CNS, gut and C cells of the thyroid -- cells which probably migrated originally from the neural crest during development. While the pharmacological effects of somatostatin are diffuse, its physiological role is at present unknown, but in view of its concentration in synaptosomal fractions of neural tissue, it may have a neurotransmitter or a synaptic modulator function.
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PMID:Somatostatin, 1976. 0 97

In order to investigate the source of free amino acids found in the gut lumen during absorption of dipeptides, as well as evaluating the role of brush border peptidases in the mucosal hydrolysis of dipeptides during absorption, rates of dipeptide disappearance and appearance of hydrolytic products were measured during perfusion of rat jejunum and ileum in vivo with buffered and unbuffered 10 mM solutions of glycl-L-phenylalanine (Gly-Phe) and L-phenylalanyl-glycine (Phe-Gly). Mucosal brush border peptidase activity was then measured in the perfused segments in vitro at luminal pH and at two substrate concentrations. In addition cytosol peptidase activity in the perfused segments was measured at pH 7-4 and at 10 mM substrate concentrations. In the jejunum, there was a relationship between rates of free phenylalanine appearance in vivo (Phe-Gly greater than Gly-Phe) and rates of brush border (Phe-Gly greater than Gly-Phe) rather than cytosol (Gly-Phe greater than Phe-Gly) peptidase activities. No constant relationship between free phenylalanine appearance and hydrolysis of the dipeptides by either brush border or cytosol peptidases was observed in the ileal studies. These findings suggest that, in the jejunum, hydrolytic products originate from the surface of the cell whereas, in the ileum, hydrolytic products originate from both the intracellular compartment as well as from the surface of the mucosal cell. In the jejunum, in vitro rates of brush border hydrolysis of Gly-Phe were always less than in vivo disappearance rates, whereas rates of Phe-Gly brush border hydrolysis always exceeded luminal disappearance rates. These data imply that Gly-Phe is predominantly transported intact and hydrolysed by cytosol peptidases, In contrast, brush border peptidases play an importnat role in the mucosal hydrolysis of Phe-Gly.
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PMID:Relationships between mucosal hydrolysis and transport of two phenylalanine dipeptides. 1 68


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