Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitrosamines are carcinogenic compounds synthetized from amines and nitrites or nitrates, if nitrates in the reaction medium may be reduced to nitrites. Nitrosation is determined in the digestive tract of several species of laboratory animals. Two physiochemical factors appear to determine in vitro nitrosamine formation: the type of amine and the medium pH. The property of secondary amines to nitrosate is inversely related to amine basicity (checked in vivo), and it increases with the medium acidity. In vitro studies show that different types of bacteria can, even at neutral pH, catalyze nitroamine formation from their precursors. However, the role of digestive tract microbial flora in nitrosamine synthesis in the gut cannot be affirmed due to lack of in vivo studies.
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PMID:[Formation of nitrosamines in the digestive tract]. 2 20

In regularly dialyzed patients in basal gastric juice and after stimulation with pentagastrin the volume of titrable acidity, urea and ammonia were assessed. It was revealed that in relation to the plasma urea concentration in basal juice the mean urea and ammonia concentration is roughly half and in stimulation juice roughly one third. The urea concentration in gastric juice is negatively correlated to the ammonia concentration. Urea excretion into the stomach depends on the plasma urea level and on the secretory gastric activity. The decisive factor of gastric secretion is probably parietal cell secretion. From the results ensues that gastric juice of dialyzed patients contains a quantitatively significant amount of urea and ammonia. Ammonia due to its neutralizing action distorts the examination of gastric acidity assessed by titration. The findings call for a revision of hitherto known data concerning gastric secretion of uraemic patients.
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PMID:Urea and ammonia excretion into gastric juice in regularly dialyzed patients and patients after renal transplantation. I. Dialyzed patients. 35 87

As part of a study of transcriptional regulation by viral proteins, we examined whether an acidic region from a regulatory protein of an RNA virus could function as a trans-activator. The NH2-terminal highly acidic domain I of the phosphoprotein (P) of vesicular stomatitis virus (VSV) was fused to the DNA-binding domain of the yeast trans-activator, GAL4. In transient transfection assays, the resulting chimeric protein failed to activate transcription of a reporter CAT gene. However, mutation of basic amino acid residues located at positions 6 and 8 or the alteration of eight amino acids within the acidic domain to eight different amino acids converted the chimeric protein into a transcriptional activator comparable to wild-type GAL4. When subjected to SDS-polyacrylamide gel electrophoresis, the P proteins containing trans-activation-positive mutations in domain I showed an altered mobility, suggesting that these mutations may have caused a conformational change that is critical for trans-activation. Since the acidity of P domain I is not sufficient to activate transcription, additional features of this region must play an important role in GAL4-mediated trans-activation. None of the trans-activation-positive mutants supported VSV RNA transcription in vitro. These results suggest that the amino acid residues within P domain I that can be made to function in the trans-activation of DNA-dependent RNA transcription are distinct from those involved in VSV RNA-dependent RNA transcription.
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PMID:Alteration of specific amino acid residues in the acidic domain I of VSV phosphoprotein (P) converts a GAL4-P(I) hybrid into a transcriptional activator. 165 11

Annular denuder-filter pack sampling systems were used to make indoor and outdoor measurements of aerosol strong H+, SO4(2-), NH4+, NO3- and NO2-, and the gaseous pollutants SO2, HNO3, HONO and NH3 during summer and winter periods in Boston, Massachusetts. Outdoor levels of SO2, HNO3, H+ and SO4(2-) exceeded their indoor concentrations during both seasons. Winter indoor/outdoor ratios were lower than during the summer, probably due to lower air exchange rates during the winter period. During both monitoring periods, indoor/outdoor ratios of aerosol strong H+ were 40-50 percent of the indoor/outdoor SO4(2-) ratio. Since aerosol strong acidity is typically associated with SO4(2-), this finding is indicative of neutralization of the acidic aerosol by the higher indoor NH3 levels. Geometric mean indoor/outdoor NH3 ratios of 3.5 and 23 respectively were measured for the summer and winter sampling periods. For HONO, NH3, NH4+ and NO2-, indoor concentrations were significantly higher than ambient levels. Indoor levels of NO3- were slightly less than outdoor concentrations.
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PMID:Indoor and outdoor concentrations of inorganic acidic aerosols and gases. 205 63

Reactions of cis-diamminedichloroplatinum(II) with phosphonoformic acid (PFA), phosphonoacetic acid (PAA), and methylenediphosphonic acid (MDP) yield various phosphonatoplatinum(II) chelates which were characterized by phosphorus-31 NMR spectroscopy. The P-31 resonances for the chelates appear at 6-12 ppm downfield as compared to the uncomplexed ligands. All complexes exhibit monoprotic acidic behavior in the pH range 2-10. The chemical shift-pH profiles yielded acidity constants, 1.0 x 10(-4), 1.5 x 10(-4), and 1.3 x 10(-6) M-1, for the PFA, PAA, and MDP chelates. In addition to the monomeric chelate, MDP formed a bridged diplatinum(II,II) complex when it reacted with cis-Pt (NH3)2(H2O)2(2)+. The P-31 resonance for this binuclear complex appears at 22 ppm downfield from the unreacted ligand. Rate data for the complexation reactions of the phosphonate ligands with the dichloroplatinum complex are consistent with a mechanism in which a monodentate complex is formed initially through rate-limiting aquation process of the platinum complex, followed by a rapid chelation. For the PFA and PAA complexes, initial binding sites are the carboxylato oxygens. Implications of the various binding modes of the phosphonates in relationship to their antiviral activities are discussed.
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PMID:Phosphonato complexes of platinum(II): kinetics of formation and phosphorus-31 NMR characterization studies. 215 Aug 56

We have purified an acidic octapeptide from the neural ganglion of the protochordate Ciona intestinalis by a three-step procedure including C18 Sep-Pak fractionation, MonoQ ion-exchange chromatography, and C4 reversed-phase high-performance liquid chromatography. The purification was monitored by an immunoassay specific for the alpha-carboxyamidated COOH terminus common to the mammalian brain-gut hormones, cholecystokinin and gastrin. Automated Edman degradation revealed the sequence Asn-Tyr-Tyr-Gly-Trp-Met-Asp-Phe. In accordance with the high acidity of the peptide, amino acid analysis after cleavage with aminopeptidase M showed that both tyrosyl residues are sulfated. Hence, the structure is Asn-Tyr(SO3)-Tyr(SO3)-Gly-Trp-Met-Asp-Phe-NH2, as also confirmed by identity with the synthetic disulfated peptide in different chromatographic systems. The occurrence of two consecutively sulfated tyrosyl residues after a neutral residue challenges present concepts of consensus sites for tyrosyl sulfation. We conclude that the structure of the peptide, named cionin, suits that of a common ancestor for cholecystokinin and gastrin.
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PMID:Cionin: a disulfotyrosyl hybrid of cholecystokinin and gastrin from the neural ganglion of the protochordate Ciona intestinalis. 230 39

Ammonia production increases in several models of renal hypertrophy in vivo. The present study was designed to determine whether ammonia can directly modulate the growth of renal cells in the absence of a change in extracellular acidity. In serum-free media NH4Cl (0-20 mM) caused JTC cells and a primary culture of rabbit proximal tubule cells to hypertrophy (increase in cell protein content) in a dose-dependent fashion without a change in DNA synthesis. Studies in JTC cells revealed that the cell protein content increased as a result of both an increase in protein synthesis and a decrease in protein degradation. Total cell RNA content and ribosome number increased after NH4Cl exposure and the cell content of the lysosomal enzymes cathepsin B and L decreased. Inhibition of the Na+/H+ antiporter with amiloride did not prevent the hypertrophic response induced by NH4Cl. The results indicate that ammonia is an important modulator of renal cell growth and that hypertrophy can occur in the absence of functioning Na+/H+ antiport activity.
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PMID:Induction of hypertrophy in cultured proximal tubule cells by extracellular NH4Cl. 248 Mar 66

It has been suggested that endogenously formed N-nitroso compounds are involved in the aetiology of gastric cancer. In the model of gastric carcinogenesis postulated by Correa, gastric atrophy is an important early stage in the progression to carcinoma which results in the loss of stomach acidity, and colonization of the stomach by bacteria. As a consequence of the metabolic activity of these bacteria intragastric nitrite (a precursor to N-nitroso compounds) and possibly carcinogenic N-nitroso compounds become elevated, which may hasten the progression to carcinoma. Vitamin C has been shown to be an effective inhibitor of acid-catalysed N-nitroso compound formation, in vivo and in vitro, and this has been attributed to its relatively rapid reaction with nitrite in contrast to the slower rates of reaction of nitrite with secondary amines. However, N-nitroso compound formation in the achlorhydric stomach must proceed by mechanisms which operate at neutral pH values. One potential mechanism involves the enzymatic catalysis of N-nitrosation by a subpopulation of the bacteria colonizing the achlorhydric stomach which catalyse these reactions and in particular denitrifying organisms. In this study, we examined the effect of vitamin C on the formation of N-nitrosomorpholine from morpholine and nitrite when mediated by cells of an actively N-nitrosating denitrifying bacterium (Pseudomonas aeruginosa, BM1030) at neutral pH. Despite the fact that vitamin C ordinarily shows little reactivity towards nitrite at neutral pH it did prove to be a potent inhibitor of bacterial N-nitrosamine formation. This study provides some justification for the use of vitamin C as an inhibitor of endogenous N-nitrosation regardless of gastric pH.
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PMID:The inhibition of bacterially mediated N-nitrosation by vitamin C: relevance to the inhibition of endogenous N-nitrosation in the achlorhydric stomach. 249 12

Atmospheric gaseous pollutants (NO2, SO2, NH3, HNO3) and related ionic species in water-soluble fine particulates and rainwater were monitored from September 1986 to January 1987 with the aim of estimating the acid deposition over a rural area near Rome. A wet-only rain collector and an annular denuder-filter pack sampling system for gases and aerosols were employed to avoid chemical artifact formation. A comparison of the wet and dry deposition rates indicates that atmospheric removal by precipitation was the dominant sink for sulfate and nitrate at the sampling site. Ion balance analysis showed that the main compounds present in aerosols were (NH4)2SO4 and NH4NO3, since the ammonium neutralization factor approached 100% and the acidity content was very low. The marked enrichment of H+, SO4(2-) and NO3- in precipitation compared with NH4+ could be explained by assuming either that SO2 and NO2 are oxidized in cloud droplets or that acidic sulfate and nitrate are scavenged directly in-cloud or below-cloud.
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PMID:Characterization of a rural area in terms of dry and wet deposition. 285 79

Mineralocorticoid plays a role in urinary acidification and acid-base balance, but the response of the inner medulla to aldosterone has not been elucidated. A model of selective aldosterone deficiency (SAD) with hyperkalemia and hyperchloremic metabolic acidosis was employed to assess segmental acidification by measuring in situ pH, titratable acidity (TA) and total ammonia (Am). Hydrogen ion secretion was also examined as a function of the increment in in situ PCO2 in the collecting duct during bicarbonate loading. SAD rats were compared to ADX controls that received adrenalectomy and chronic replacement of gluco- and mineralocorticoid and to rats with chronic metabolic acidosis induced by oral NH4Cl (CMA). Both fractional and absolute delivery of Am to the loop of Henle was lower in SAD vs. CMA rats (1.34 to 3.63 mM, P less than 0.01). Delivery of Am to the base and tip collecting duct (BCD and TCD) was also markedly lower in SAD (1.50 vs. 0.52 and 1.77 vs. 0.47 mM, respectively, P less than 0.01). Net addition of Am and net acid between BCD and TCD, observed in CMA rats, was not observed in SAD despite equivalent degrees of systemic metabolic acidosis. Similarly, the concentration gradient favoring transfer of NH3 between loop of Henle and CD was reduced in SAD. During bicarbonate loading the increment in PCO2 at BCD, TCD and in final urine was significantly lower in SAD rats than in adrenal intact bicarbonate-loaded rats. Therefore, the acidification defect in this model of SAD appears to be a result of a decrease in ammonia production and delivery to the loop of Henle, impaired transfer from loop to collecting duct and reduction in the rate of H+ secretion by the collecting duct.
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PMID:Effect of selective aldosterone deficiency on acidification in nephron segments of the rat inner medulla. 318 58


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