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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The paper confirms the existence of a peroxide mechanism involved in oxidation of iron and manganeses by the most typical iron bacteria growing at neutral acidity of the medium. Oxidation of bivalent iron and manganese is accomplished by the simultaneous action of catalase and hydrogen peroxide produced in the respiratory chain in the course of oxidation of organic substances. Catalase performs the peroxidase function in these processes. The possibility of these biological reactions to occur and the necessary conditions have been studied in vitro. Possible variants of iron and manganese oxidation by iron bacteria are discussed, including the conditions for "symbiotic" oxidation of manganese by mixed cultures of microorganisms.
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PMID:[Mechanism of the oxidation of divalent iron and manganese by iron bacteria developing in a neutral acidic medium]. 3 22

The acid concentration and quantity, the pH and the peptic activity of the gastric juice were measured after stimulation with pentagastrin in 10 children with cystic fibrosis between the ages 2 and 12 years and in 20 healthy children of the same age group. Furthermore, the basal, maximal and peak volume outputs (BVO, MVO and PVO), the basal, maximal and peak acid outputs (BAO, MAO and PAO) and the basal, maximal and peak pepsin output (BPO, MPO and PPO) were determined. The statistical calculations were carried out with the help of partial hierarchical analysis of variance, comparison of regression curves, simple analysis of covariance and the t test. After stimulation with pentagastrin, the volume of the gastric juice, the acid quantity and the peptic activity were found to be dependent on age in healthy children as well as in children with cystic fibrosis. The maximal volume of secretion in children with cystic fibrosis is less than that of healthy children; however, the acid quantity and peptic activity show no significant difference in both groups. The volume of the gastric juice, acid quantity and peptic activity in basal and stimulated secretions, expressed in kilograms per body weight or surface area in square meters, are independent of age and show no significant difference between the two groups. In the two groups the curves for the three parameters differ significantly from one to another. There is a significant shift in the time course of the curves that depict the acid secretion and peptic activity. Contrary to the accepted views, the acid and enzyme secretions are not closely interrelated. Based on the acidity and peptic activity, the digestive capacity of the stomach is the same for healthy children and children with cystic fibrosis. In contrast to the pancreas, there is no impairment in the exocrine function of the stomach. The gastric secretions of children with cystic fibrosis are not completely the same as in healthy children.
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PMID:[The acidity and peptic activity of gastric juice in healthy children and in children suffering from cystic fibrosis (author's transl)]. 24 Nov 64

The inhibitory effect of indole-3-acetic acid, and of its peroxidase-mediated degradation products of an indole nature, on the oxidation rate of coniferyl alcohol catalyzed by cell wall peroxidases has been studied. The results show that the inhibitory effect of indole-3-acetic acid and indole-3-carbinol may be explained, in part, by their properties as peroxidase substrates. However, I50 values for a series of indole compounds not regarded as peroxidase substrates show a good correlation with the electron-donating or electron-withdrawing nature of the 3-substituents, as judged by the linearity of the Hammett rho sigma plot. These results suggest that although the properties of indole compounds as peroxidase substrates may be responsible, in part, for their inhibitory effects on the peroxidase-mediated oxidation of coniferyl alcohol, the inhibitory effect appears to be mainly determined by the acidity of the imino group of the indole nucleus.
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PMID:Hammett rho sigma correlation for the inhibition by indoles of coniferyl alcohol oxidation catalyzed by cell wall peroxidases. 128 5

Pasteurized milk was treated with microwaves for 2.5 minutes (2450 MHz, 650 W). Important chemical components (vitamin A, beta-carotin, vitamins B1, B2, C, E; activity of peroxidase, xanthinoxidase; content of fat and peroxides, percentage of solids, content of raw protein, content of all microorganisms and storage stability were examined. Ascorbic acid (reduction of 36%) and alpha-tocopherol (reduction of 17%) were influenced by microwave treatment, whereas other chemical parameters, odor and flavor remained unchanged. The content of microorganisms was reduced from about 10(4) to 10(2) per milliliter. Untreated milk had a content of 10(7) microorganisms per milliliter after 10 days storage at 8 degrees C and a taste of acidity, whereas in milk treated with microwaves only 10(4) microorganisms per ml were identified and no organoleptic changes could be observed after 14 days storage at 8 degrees C.
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PMID:[Chemical and microbiological studies of microwave-treated milk]. 208 Jun 42

Gastric mucosal cells of the rat glandular stomach were studied by light and electron microscopic procedures by use of lectins in the development of acute gastric mucosal lesions. Effects of the H2-receptor antagonist sofalcone (2'carboxymethoxy-4,4'-bis 3-methyl-2) and truncal vagotomy with pyloroplasty on lectin binding sites and distribution were also investigated. Biotinylated lectins in combination with ABC (avidin-biotinyl peroxidase complex) method were used for light and horseradish peroxidase (HRP)-labeled lectins for electron microscopic studies. Gastric mucosal cells showed the specific binding pattern for each lectin by light microscopy. Especially, binding sites and distribution of peanut agglutinin (PNA) were characteristic after induction of stress, truncal vagotomy, and administration of each drug. Staining and distribution increased in the gastric mucosa upward and downward after that. In electron microscopic studies, PNA strongly stained the membranes of the intracellular secretory canaliculi of a parietal cell. These results suggested that alternation of binding sites and distribution was regulated by change of gastric mucosal blood flow and of acidity in the parietal cells. Therefore, increase of glycoconjugate distribution is supposed to be a possibility of cytoprotective effect for a change of environment in the parietal cells.
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PMID:Alternation of gastric mucosal glycoprotein (lectin-binding pattern) in gastric mucosa in stress. A light and electron microscopic study. 221 34

The antimicrobial ability of the lactoperoxidase system was increased by the addition of larger amounts of the thiocyanate and hydrogen peroxide at levels above those suggested by other authors. Results of laboratory and field trials revealed that the potentialized system was able to preserve poor-quality raw milk for longer periods of time, at "tropical" temperatures, than when used as recommended previously. It was possible to preserve some milks at 20 degrees C for more than one day, without diminishing their overall quality. At 36 degrees C, the milks did not show acidity development for about 10 hours. Tests conducted under real collection and transportation conditions validated these findings. It was therefore proved that the system can be used practically and that its bactericidal/bacteriostatic effect on the spoilage flora of milk can be increased in order to overcome the particularly adverse conditions of milk handling in the tropics.
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PMID:Potentialization of the lactoperoxidase system for preservation of raw milk in the tropics. 343 17

Although previous workers have established that the pH of the phagocytic vacuole of the polymorphonuclear (PMN) leukocyte changes from neutral to acid, the time course of conversion has not been investigated. The present experiments were initiated to study pH changes immediately after phagocytosis. Peritoneal exudates were induced in rats; 4 h later, yeast stained with pH indicators was injected intraperitoneally, and the exudate was retrieved at 30-s intervals and examined by light microscopy. Results revealed that (a) within 3 min, pH dropped to approximately 6.5, as indicated by the change in color of neutral red-stained yeast; (b) within 7-15 min, pH dropped progressively to approximately 4.0, as indicated by color change in bromcresol green-stained yeast; (c) pH did not fall below 4, since no color change was observed up to 24 h when bromphenol blue-stained yeast was used. The finding that intravacuolar acidity increases rapidly after phagocytosis is undoubtedly important with respect to PMN leukocyte function in killing and digesting microorganisms, for many PMN leukocyte granule enzymes (i.e., peroxidase and lysosomal enzymes) are activated at acid pH ( approximately 4.5). It follows that temporal changes in pH and maximal pH depression should be considered in studies of intraleukocytic microbicidal mechanisms, since a defect in these factors could result in impaired PMN leukocyte function.
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PMID:Temporal changes in pH within the phagocytic vacuole of the polymorphonuclear neutrophilic leukocyte. 411 90

1. Patients with chronic Chagas' disease have abnormally low gastric acid secretion and increased gastrin release both during fasting and after different stimuli. Regardless of the relationship between intragastric acidity and gastrin secretion, it is uncertain whether hypergastrinemia in Chagas' disease is caused by an increased population of antral gastrin (G) cells (hyperplasia) or by enhanced cell activity (hyperfunction). 2. We therefore estimated G cell number in antral biopsies from 16 chagasic patients and 13 control subjects using a peroxidase-anti-peroxidase immunohistochemical technique. All subjects underwent a gastric secretion test to determine peak acid output following intravenous pentagastrin instillation. 3. Antral G cell number in Chagas' disease patients was not significantly different from that observed in the control group (number of cells/mm2, median and (range): 128 (44-284) vs 138 (65-285)). 4. In chagasic patients, peak acid output was significantly lower than in controls (mmol/h, median and (range): 9.819 (3.024-21.564) vs 17.490 (9.423-25.848)). 5. These results suggest that the increase in gastrin release associated with reduced gastric acid secretion in Chagas' disease is mediated by antral G cell hyperfunction rather than by hyperplasia.
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PMID:Antral gastrin cell population in patients with chagasic megaesophagus and megacolon. 808 Dec 89

The presence of vacuolar H(+)-ATPase (V-ATPase) on exocytotic granules in eosinophils and the role of this enzyme in exocytosis were explored in this study. Antibody against 116-kd subunit of V-ATPase positively stained eosinophil granules in immunofluorescence analysis. When eosinophil lysate was extracted immunomagnetically with the same antibody, the extracted fraction contained a considerable amount of eosinophil peroxidase, a marker of eosinophil-specific granules, which indicates that V-ATPase was present on the membranes of eosinophil exsosomal granules. The pH of the eosinophil granules, measured fluorometrically with acridine orange as a delta pH-sensitive dye, was estimated to be 5.1. The acidity of the eosinophil granules was perturbed by bafilomycin A1, a potent selective inhibitor of V-ATPase, which indicates that the low pH of these granules is maintained by V-ATPase activity. BafilomycinA1 and NH4Cl, both of which raise the intragranular pH to neutral, inhibited the eosinophil peroxidase exocytosis induced by platelet-activating factor. These agents did not, however, affect the changes in cytosolic free calcium concentration [Ca2+]i induced by platelet-activating factor. These observations suggest that bafilomycin A1 inhibited a delta pH-requiring step in eosinophil exocytosis that was preceded by the [Ca2+]i transient in the signal transduction pathway, and, hence, the findings suggest the pivotal role of V-ATPase in maintaining intragranular pH and its function of eosinophil exosomal granules.
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PMID:The role of vacuolar H(+)-ATPase in the control of intragranular pH and exocytosis in eosinophils. 894 Dec 14

The lactoperoxidase system is a naturally occurring antimicrobial system found in milk, with lactoperoxidase, thiocyanate and hydrogen peroxide as its components. The keeping quality of milk pasteurized at 72 degrees C for 15 s was found to be better than that of milk heated at 80 degrees C for 15 s. This agrees with previous findings and is usually attributed to heat shocking of spores. However, complete deactivation of lactoperoxidase occurred at 80 degrees C-15 s, whereas at 72 degrees C-15 s residual lactoperoxidase activity was approximately 70%, which may provide an alternative explanation. Higher levels of hypothiocyanite (the major antimicrobial agent produced by the lactoperoxidase system) were also detected in milk processed at 72 than at 80 degrees C, which supports the theory that the lactoperoxidase system has a role in the keeping quality of pasteurized milk. Of all the methods evaluated, titratable acidity and alcohol stability gave the most consistent estimates of keeping quality, while dissolved oxygen was a good indication of the onset of spoilage. Lactoperoxidase activity decreased with temperature more rapidly between 70 and 80 degrees C than is usual for an enzyme over a 10 deg C range.
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PMID:Contribution of the lactoperoxidase system to the keeping quality of pasteurized milk. 1019 75


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