Effect of exogenous activation of kininogenesis on the functional morphology of the gastric fundal glands in experimental conditions

The experiments on Wistar rats have shown that activation of kinin-forming system with intraperitoneal kallikrein injection was accompanied by phase changes of enzyme activity responsible for acid, mucus and protein production in fundal gland cells of the stomach.     

Stomach remodeling-associated changes of H+/K+-ATPase beta subunit expression in Xenopus laevis and H+/K+-ATPase-dependent acid secretion in tadpole stomach

Through subtractive hybridization, H+/K+-ATPase beta subunit mRNA, highly expressed in the larval stomach of Xenopus laevis, was isolated. In situ hybridization demonstrated that the H+/K+-ATPase beta subunit mRNA was exclusively expressed in manicotto gland cells of the larval stomach, not in any other cell. Northern blot analysis showed that metamorphosis-associated changes of the H+/K+-ATPase beta subunit mRNA expression in the stomach were characterized by high expression in tadpoles, a considerably lower expression in metamorphosing tadpoles, and a re-increase of expression in froglets. Further in situ hybridization showed that the decrease of expression correlated with the degeneration of larval type epithelium in the manicotto gland, while the re-increase correlated with the differentiation of oxynticopeptic cells of the adult type stomach. Moreover, the H+/K+-ATPase beta subunit mRNA was expressed in adult epithelial primordia. Such changes were found in thyroid hormone-induced precocious metamorphosis. Based on studies using this ATPase as well as xP1 and PgC (pepsinogen C) as molecular markers, this study discusses a probable cell lineage involved in metamorphosis-associated stomach remodeling. The pH of luminal contents of the larval stomach was found to be lower than 2. In addition, the pH of an isolated stomach changed from 7.2 to lower than 4 after incubation in Ringer's solution, suggesting acid production from the larval stomach. This is the first demonstration of the H+/K+-ATPase-mediated acid production and secretion in the larval stomach of Xenopus laevis.     

Effect of adrenalectomy on the gastric juice secretion evoked by food or histamine in dogs

Comparison was made of the effect of total adrenalectomy on the gastric secretion in chronic experiments on dogs with the Pavlov's stomach and Basov's fistula. A decrease of the maximal secretion level of gastric juice was associated with the alteration of the organ hemodynamics. A tendency to reduction of the acid production in the stomach was revealed. Essential differences were noted in the character of proteolytic enzymes secretion with different agents stimulating the secretion. Specific nature of the gastric secretory system for each stimulant, and different effects of adrenalectomy on the secretion induced by these stimulants was shown.     

Immunocytochemical and in situ hybridization studies of gastrin after cisplatin treatment.

Cisplatin treatment (9 mg/kg) causes bloating of the stomach, an increase in gastric acid, and ulceration in rats. Gastrin, a gut peptide, plays an important role in regulating gastric acid production. To study the role of gastrin in this increased gastric acid production after cisplatin treatment, male Wistar rats (100-150 g) were treated with cisplatin (9 mg/kg) in five divided doses over 5 consecutive days. The rats were sacrificed 1, 6, 10, or 15 days after the last treatment. As measured by immunocytochemistry, in situ hybridization, Northern blot, and dot-blot techniques, gastrin was found to be below detectable limits just 1 day after cisplatin treatment. However, 10-15 days after the last injection, the levels for both gastrin and its mRNA gradually recovered to normal. Northern blot studies showed that decreased somatostatin mRNA parallels the changes of gastrin and its mRNA. These results suggest that after cisplatin treatment the increased gastric acid production in rat stomach is independent of gastrin. This decrease of gastrin production is not under the influence of somatostatin, which also decreased after cisplatin treatment.     

Role of endogenous nitric oxide in mucosal defense of inflamed rat stomach following iodoacetamide treatment

Nitric oxide (NO) plays a role in regulating the mucosal integrity of the stomach. However, its part in the mucosal defense of the inflamed stomach remains unclear. In the present study, we examined the effects of various NO synthase (NOS) inhibitors on gastric ulcerogenic and acid secretory responses following daily exposure of the stomach to iodoacetamide and investigated the role of each NOS isozyme in gastric protection from subchronic mucosal irritation. Gastric mucosal irritation was induced in rats by addition of 0.1% iodoacetamide to drinking water, and the gastric mucosa was examined on the 6th day. L-NAME (a nonselective NOS inhibitor: 20 mg/kg) or aminoguanidine (a selective iNOS inhibitor: 20 mg/kg) was given s.c. twice 24 h and 3 h before the termination of iodoacetamide treatment. Giving iodoacetamide in drinking water for 5 days produced minimal damage in the stomach with an increase in myeloperoxidase (MPO) activity and lipid peroxidation. Iodoacetamide treatment up-regulated the expression of iNOS mRNA and NO production in the stomach, without affecting nNOS expression. Both L-NAME and aminoguanidine markedly aggravated gastric lesions induced by iodoacetamide treatment, with a further enhancement in MPO activity and lipid peroxidation. Basal acid secretion as determined in pylorous-ligated stomachs was decreased following iodoacetamide treatment, but the response was significantly restored by both L-NAME and aminoguanidine. These results suggest that endogenous NO derived from both cNOS and iNOS is involved in mucosal defense of the inflamed stomach, partly by decreasing acid secretion, and contributes to maintaining mucosal integrity under such conditions.     

Maize meal, non-esterified linoleic acid, and endemic cancer of the esophagus--preliminary findings.

Endemic cancer of the esophagus has shown a positive association with the consumption of maize meal. It has been postulated that this association is due to the conversion, in the stomach mucosa, of the linoleic acid contained in maize meal to prostaglandin E2. The proportion of non-esterified linoleic acid available in the stomach may therefore be an important factor. Samples of commercially prepared maize flour, cooked and uncooked, and other maize-based foods were analysed for total and free content of various fatty acids using gas-liquid chromatography. High levels of non-esterified fatty acids (11 to 42% of contained fatty acids) were found both in maize meal and in foods prepared from it. In food prepared from maize meal, 49 mg to 363 mg non-esterified linoleic acid per 100-g sample was found. High levels of non-esterified linoleic acid in the diet, causing raised intragastric production of prostaglandin E2 and profoundly affecting the normal pH and fluid content of the esophagus, may create a predisposition to esophageal carcinogenesis.     

Glycosphingolipid patterns of the gastrointestinal tract and feces of germ-free and conventional rats

Acid and non-acid glycosphingolipids of stomach, small and large intestine, and stimulated feces of germ-free and conventional rats of the same stain have been isolated and characterized. The glycosphingolipid patterns of the intestinal organs were chemically and immunologically very similar between the two groups of rats and relatively unaffected by the presence of an intestinal microbial flora. The major exception was the presence of hematoside with N-glycoloylneuraminic acid (NeuGc) (NeuGc alpha 2----3Gal beta 1----4Glc beta 1----1Cer) in the stomach of conventional rats not found in the stomach of germ-free animals. Glycosphingolipids of stimulated feces of germ-free animals were derived from epithelial cells mainly of the small intestine and showed no signs of degradation. Glycosphingolipids of feces of conventional rats completely retained the pattern of blood group A-, B-, and H-active glycolipids as found in sterile feces but contained less of hematoside and more of lactosylceramide. This effect was probably due to degradation by bacteria, as demonstrated in vitro with the production of lactosylceramide after treatment of the isolated acid glycolipids of sterile feces with neuraminidase from Clostridium perfringens. The amount of total non-acid glycosphingolipids per dry weight was similar for stomach, was 50% higher for small intestine, and 300% higher for large intestine of germ-free animals compared to conventional animals. Due to the presence of large amounts of mucins the dry sterile feces contained 12% less non-acid glycolipids than conventional feces. However, calculated per rat per day the germ-free animal excreted more of non-acid glycosphingolipids (1.8 and 1.2 mg, respectively).     

The contribution of Jan Evagelista Purkyn? to knowledge of the morphology and function of the gastric mucosa

Histological studies of the gastric mucosa led Purkyn? to the discovery of the cell as a fundamental structural unit of an organ (1837). This study led Purkyn? to draw conclusions about the physiological role of the gastric mucosa in protein digestion. These conclusions included the activation of pepsinogen, the buffering role of saliva and bile, and the production of hydrochloric acid. Purkyn? was thus the first to provide a general concept of the role of the stomach in food digestion.     

Red wine-dependent reduction of nitrite to nitric oxide in the stomach

Nitrite may be a source for nitric oxide (*NO), particularly in highly acidic environments, such as the stomach. Diet products contribute also with reductants that dramatically increase the production of *NO from nitrite. Red wine has been attributed health promoting properties largely on basis of the reductive antioxidant properties of its polyphenolic fraction. We show in vitro that wine, wine anthocyanin fraction and wine catechol (caffeic acid) dose- and pH-dependently promote the formation of *NO when mixed with nitrite, as measured electrochemically. The production of *NO promoted by wine from nitrite was substantiated in vivo in healthy volunteers by measuring *NO in the air expelled from the stomach, following consumption of wine, as measured by chemiluminescence. Mechanistically, the reaction involves the univalent reduction of nitrite, as suggested by the formation of *NO and by the appearance of EPR spectra assigned to wine phenolic radicals. Ascorbic and caffeic acids cooperate in the reduction of nitrite to *NO. Moreover, reduction of nitrite is critically dependent on the phenolic structure and nitro-derivatives of phenols are also formed, as suggested by caffeic acid UV spectral modifications. The reduction of nitrite may reveal previously unrecognized physiologic effects of red wine in connection with *NO bioactivity.     

Cyclopamine inhibition of the sonic hedgehog pathway in the stomach requires concomitant acid inhibition

The Shh pathway has been implicated in gastric carcinogenesis, and inhibition of this pathway has been shown to inhibit tumour growth in gastric cell lines. Assessing the in vivo efficacy of Shh pathway antagonists in blocking Shh signaling in the stomach is important for clinical trial design, but has not been previously investigated. We investigated the in vivo efficacy of a Shh antagonist, cyclopamine, in correlation to the secondary effects induced by this treatment on gastrin levels and acid secretion. Gastrin has been shown to induce Shh production, processing and activity, which is believed to be mediated by acid secretion. We tested this hypothesis and showed that hypergastrinaemia induces Shh production in vivo, and confirmed that this effect on Shh is mediated by acid secretion. We showed that cyclopamine treatment induces both hypergastrinaemia and Shh, and does not inhibit Gli-1. Inhibition of the effect of hypergastrinaemia on the Shh pathway, in cyclopamine-treated mice, was demonstrated by use of lansoprazole which concomitantly inhibited Gli-1, and did not increase Shh production. Therefore, this evidence suggests that hypergastrinaemia, via increased acid secretion, may increase expression of Shh and that Shh antagonists may require concomitant acid inhibition to successfully inhibit a pathway known to be up-regulated in gastric carcinogenesis.     

NMDA inhibits oxotremorine-induced acid secretion via the NO-dependent cyclic GMP system in rat stomach

The mechanism of N-methyl-D-aspartate (NMDA) inhibits oxotremorine-induced acid secretion was examined in rat stomach, in relation to the cyclic GMP system. NMDA (10(-7) M) did not affect the spontaneous acid secretion from the everted preparations of isolated rat stomach, but inhibited the acid secretion stimulated by oxotremorine, and this effect of NMDA was antagonized by 2-amino-5-phosphonovaleric acid (AP-5), (+/-)3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) or N(G)-nitro-L-arginine (L-NNA). NMDA also elevated the cyclic GMP content of mucosal slices from rat stomach, and this effect of NMDA was antagonized by L-NNA. These results indicate that NMDA receptors are present in the rat stomach and regulate the gastric acid secretion. The mechanism underlying the effect of NMDA inhibits oxotremorine-induced acid secretion may be mediated by the NO-dependent cyclic GMP system.     

Development of gastric acid secretion in pigs from birth to thirty six days of age: the response to pentagastrin

The development of the gastric acid secretory response to pentagastrin was studied using 56 Large White x Landrace pigs, 0-36 days of age, 1.1-13.3 kg body-weight, obtained from 12 litters. Gastric acid secretory capacity was measured using a gastric perfusion technique and intravenous infusion of pentagastrin at dose rates of 2, 4 and 8 micrograms/h per kg. Significant positive linear correlations were found between stomach weight and age, and between stomach weight and body-weight during the 36 day period. The stomach weight to body-weight ratio increased for the first 3 days of age and then decreased during the following 33 days. Basal acid secretion was detected in all unsuckled pigs (n = 9), 2- to 8-h old. Maximal acid outputs in response to pentagastrin in these pigs were 0.16 +/- 0.02 mmol/kg body-weight and 0.034 +/- 0.001 mmol/g stomach weight. For the 56 pigs, significant linear correlations were found between maximal acid output and age, maximal acid output and body-weight, and maximal acid output and stomach weight. There was a significant linear increase in maximal acid output per unit stomach weight during the first 7 days of age, but during the subsequent 29 days the pattern of increase in gastric secretory capacity was slower and curvilinear. In the oldest nine pigs, 24-36 days of age, maximal acid outputs were 0.974 +/- 0.058 mmol/kg body-weight and 0.234 +/- 0.016 mmol/g stomach weight which represents a six to seven-fold increase compared with those determined in pigs at birth. Comparison of gastric acid secretory capacity determined under anaesthesia with that in conscious pigs showed that anaesthesia appeared to suppress basal output but had no effect on pentagastrin stimulated output. Comparison of response to histalog (betazole HCl) and pentagastrin indicated that newborn pigs were more sensitive to histalog but in pigs 9-38 days of age, there were no significant differences in responsiveness to the two secretagogues. These results show that gastric sensitivity to pentagastrin increases rapidly in the first week of life, that the stomach of the newborn pig is more sensitive to histalog than pentagastrin and that studies of the effect of pentagastrin on acid secretion, done under anaesthesia, are comparable to those in the conscious pig.     

Nucleases activity in different segments of the human digestive tube compared to the incidence of carcinomas (histochemical study)

Summary The alkaline and acid DNase and RNase activity was histochemically investigated in biopsies from the human digestive tube. Activity of these enzymes in the mucosal epithelium in different segments of the digestive tube was compared to the statistical incidence of malignant tumors deriving from this tissue (carcinomas). It was found that the alkaline and acid nucleases activity was very intense in small intestine precisely in this segment where the incidence of carcinomas was low, whereas the low activity of these enzymes in the stomach and large intestine corresponded to the high incidence of carcinomas. This observation confirmed our previously elaborated hypothesis, according to which the low activity of nucleases in normal tissues appeared to be a predisposing factor for malignant transformation.It could be also supposed that the nucleases constitute some kind of double barrier mechanism protecting the genetical stability of the cell against foreign nucleic acid incorporation or production; alkaline nucleases being an extracellular and acid nucleases an intracellular barrier.     

The identification of the antimicrobial factors of the stomach contents of sucking rabbits

1. A procedure for the extraction and purification of antimicrobial factors from the stomach contents of sucking rabbits is described. 2. The fatty acid composition of the hydrogenated ;rabbit stomach oil' is given. 3. The most active factors isolated were identified as free n-decanoic acid and n-octanoic acid. 4. The antimicrobial activities of some fatty acids and that of ;rabbit stomach oil' are compared.     

The transfer of radiolabelled n-6 essential fatty acids by the mammary system of the tree-shrew (Tupia tana)

The fatty acid content of tree-shrew milk has been determined from analysis of the stomach content of infants immediately after suckling. Comparison of the n-6 fatty acid composition of the stomach contents, liver and brain demonstrate a striking increment in the ratio of arachidonic to linoleic acid. Feeding radioactively labelled linoleic acid to the mother 24 hr prior to suckling showed that 12-20% was transferred to the milk. Evidence from the appearance of the radioactivity administered as linoleic acid into arachidonic acid indicates that this species is able to desaturate linoleic acid.     

Gastric Pepsin in an Anuran Larva

Larval stomach development was studied in the obligate carnivorous larva of the frog Lepidobatrachus laevis . Pepsin producing cells of the larval stomach were identified using rabbit anti-porcine pepsin and immunohistochemical techniques. Pepsin production was detected at a very early stage of development (stage 24: during opercular development) when the larvae were first competent for feeding. Peptic activity in isolated larval stomachs was demonstrated in a microassay using acid denatured hemoglobin at pH 1.7. The total activity per stomach increased 5,400 fold through the beginning of metamorphosis and the specific activity increased 345 fold through the same period. Electrophoretic analysis of the larval pepsinogens, using a caseinolytic assay revealed the presence of one major pepsinogen at stage 24; two additional isozymes were observed during later larval development. The molecular weight of the isopepsinogens was 34,800.     

L-type amino acids stimulate gastric acid secretion by activation of the calcium-sensing receptor in parietal cells

Parietal cells are the primary acid secretory cells of the stomach. We have previously shown that activation of the calcium-sensing receptor (CaSR) by divalent (Ca(2+)) or trivalent (Gd(3+)) ions stimulates acid production in the absence of secretagogues by increasing H(+),K(+)-ATPase activity. When overexpressed in HEK-293 cells, the CaSR can be allosterically activated by L-amino acids in the presence of physiological concentrations of extracellular Ca(2+) (Ca(o)(2+); 1.5-2.5 mM). To determine whether the endogenously expressed parietal cell CaSR is allosterically activated by L-amino acids, we examined the effect of the amino acids L-phenylalanine (L-Phe), L-tryptophan, and L-leucine on acid secretion. In ex vivo whole stomach preparations, exposure to L-Phe resulted in gastric luminal pH significantly lower than controls. Studies using D-Phe (inactive isomer) failed to elicit a response on gastric pH. H(+)-K(+)-ATPase activity was monitored by measuring the intracellular pH (pH(i)) of individual parietal cells in isolated rat gastric glands and calculating the rate of H(+) extrusion. We demonstrated that increasing Ca(o)(2+) in the absence of secretagogues caused a dose-dependent increase in H(+) extrusion. These effects were amplified by the addition of amino acids at various Ca(o)(2+) concentrations. Blocking the histamine-2 receptor with cimetidine or inhibiting system L-amino acid transport with 2-amino-2-norbornane-carboxylic acid did not affect the rate of H(+) extrusion in the presence of L-Phe. These data support the conclusion that amino acids, in conjunction with a physiological Ca(o)(2+) concentration, can induce acid secretion independent of hormonal stimulation via allosteric activation of the stomach CaSR.     

The role of Na K ATPase in thiamine and lipoic acid interrelations during their absorption in the gastrointestinal tract of mice

35S-lipoic acid (20 mumol/kg) with different doses of thiamine or 35S-thiamine (50 mumol/kg) with unlabelled lipoic acid where administrated to the white mice stomach. It was established that absorption and entrance of both lipoic acid and thiamine when they were in 1:5 quantities in organs and tissues were maximal. The activity of Na+, K-ATPase determined in stomach, duodenum and small intestine was the maximal too.     

The development of the stomach in Clarias lazera and the intestinal absorption of protein macromolecules

Summary The development of the stomach of the teleost, Clarias lazera, during the early posthatching period, is described, and the developing stomach is compared with that of adult Clarias.The stomach develops in two distinct parts: the corpus, which differentiates first, and the pylorus. The corpus contains a mucous surface epithelium, arranged in folds, and a tubular gland system containing only one type of gland cell, to which the secretion of pepsinogen and HCl is attributed. The pyloric region does not contain tubular glands.From the ultrastructure of the gland cells, the ³H-thymidine labeling index, and the onset of acid production (as determined with pH indicators) it is concluded that a functional stomach is present in juveniles with a standard length of ± 11 mm (approximately 12 days after fertilization at 23–24° C).The ultrastructure of the intestinal epithelium has also been studied. The intestine consists of three segments, similar to those described for stomachless teleosts and a number of fish larvae. In larvae as well as in juveniles, the enterocytes of the second segment show pinocytosis of horseradish peroxidase, although in the juveniles the stomach has already developed. This second segment has the same relative length in all studied larvae and juveniles and is also present in adult Clarias.It is therefore concluded that the capacity to absorb protein macromolecules is not specifically related to the absence of a functional stomach in this teleost species.