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

We have studied the mechanism by which liver Golgi apparatus maintains the acidity of its contents, using a subcellular fraction from rat liver highly enriched in Golgi marker enzymes. Proton accumulation (measured by quenching of acridine-orange fluorescence) and anion-dependent ATPase were characterized and compared. Maximal ATPase and proton accumulation required ATP; GTP and other nucleotides gave 10% to 30% of maximal activity. Among anions, Cl- and Br- approximately doubled the activities; others were much less effective. Half-maximal increase of ATPase and H+ uptake required 55 mmol/L and 27 mmol/L Cl-, respectively. In predominantly chloride media, SCN- and NO3- markedly inhibited H+ uptake. Nitrate competitively inhibited both the chloride-dependent ATPase (apparent Ki 6 mmol/L) and proton uptake (apparent Ki 2 mmol/L). Nitrate and SCN- also inhibited uptake of 36Cl. Replacing K+ with Na+ had no effect on the initial rate of proton uptake but somewhat reduced the steady state attained. Replacement of K+ with NH4+ and choline reduced proton uptake without affecting ATPase. The ATPase and H+ uptake were supported equally well by Mg2+ or Mn2+. The ATPase was competitively inhibited by 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid (apparent Ki 39 mumol/L). Other agents inhibiting both H+ uptake and ATPase were N-ethylmaleimide, N,N'-dicyclohexylcarbodiimide, chlorpromazine, diethylstilbestrol, Zn2+, Co2+ and Cu2+. In the Cl- medium, accumulated protons were released by ionophores at the relative rates, monensin = nigericin greater than valinomycin greater than carbonyl cyanide mchlorophenylhydrazone; the last of these also reduced ATPase activity. In the absence of Cl-, monensin and valinomycin both stimulated the ATPase. These results show a close association between ATPase activity and acidification of liver Golgi vesicles. They support a role for Cl- that depends on its uptake as a counter ion for H+ and suggest that it may also stimulate proton transport by a more direct effect on a component of the transport system.
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PMID:Proton accumulation and ATPase activity in Golgi apparatus-enriched vesicles from rat liver. 184 95

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

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

The effects of low concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) on actively dividing cultures of Staphylococcus aureus, Micrococcus luteus, Micrococcus roseus, Serratia marcescens, Bacillus subtilis, Bacillus circulans, Bacillus megaterium, and Bacillus cereus were studied. Fresh cultures of each organism were incubated for 24 h at 25 degrees C on both nutrient agar and mineral salts glucose agar plates under atmospheres containing various low concentrations of NO in air (0 to 1.9 ppm [0 to 2.0 micrograms/g of air]), NO2 in air (0 to 5.5 ppm [0 to 8.8 micrograms/g of air]), or NO and NO2 in air. Bacteria grown under air only were used as controls. After incubation, the colonies that developed on the plates were counted. None of the bacteria tested was affected by NO or NO2 at the indicated concentrations while growing on nutrient agar. Serratia marcescens, B. circulans, B. subtilis, B. megaterium, and B. cereus grown on mineral salts glucose agar were not significantly affected by NO or NO2. Low concentrations (0 to 1.9 ppm) of NO were bacteriostatic to log-phase cultures of M. roseus, M. luteus, and Staphylococcus aureus grown on mineral salts glucose agar. Bacteriostatic activity over a 24-h interval was maximal at an initial NO concentration of 1 ppm. Appreciable amounts of NO2 were produced in 24 h at initial NO concentrations greater than 1 ppm. These results suggest that NO2 may reduce the bacteriostatic activity of NO. Low concentrations (0 to 5.5 ppm) of NO2 in air did not affect any of the bacteria tested. At these low concentrations, NO affected bacterial growth, although NO2, NO2-, and NO3- did not. In addition, it was determined that the bacteriostatic activity observed in this study was not due to an increase in the acidity of the medium.
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PMID:Effects of nitric oxide and nitrogen dioxide on bacterial growth. 635 44

The toxic action of nitrates and nitrites has often been summarized by methemoglobinemia and nitrosation of amines inducing carcinogenic effects; these two impacts are spectacular, but they hide varying more or less insidious actions recently studied and perceived. In the NO3/NO2 couple, it is accepted that especially nitrite ion lays down a toxicological problem, probably because of its particular chemical reactivity: nitrite ion, which is the base of nitrous acid HNO2 (pKa = 3.36) can react with many functional groups from dietary or endogenous origin; it is also a reducing agent, only oxidable by chemical oxidants or adequate enzyme systems; at the same time it is an oxidant for many reduced substrates. These different possibilities explain the chemical complexity of these compounds and almost their reactivity in biological various media with toxicological implications (modification of the redox state). In man, the presence of nitrates in the digestive tract may result in nitrite formation, because nitrate-reductase from bacterial or enterocyte origin; more particularly in stomach, nitrites are characterized by a great instability imputable to the low pH of gastric juice and to secreted factors which accelerate phenomena; at the same time, nitrates and nutrites exercise opposite effects on gastric secretion (volume, acidity, pepsin) and on gastric mucosal irrigation: while nitrates increase these different parameters, nitrites reduce secretory activity but correlations between secretion and irrigation show that nitrates induce a deep modification of hydric compartment whereas nitrites rather react through cellular anoxy. In intestine, nitrates and chiefly nitrites are very quickly absorbed by a passive mechanism and they are characterized by an extrahepatic cycle; nitrates and nitrites are also eliminated in large quantities by kidneys, and nitrates have a very high diuretic effect: these NO3- ions move Cl- ions, inducing a Na+ waste, a decrease in extracellular space and an alkalosis; this diuretic action of ionic origin is moreover increased by a rise in glomerular blood flow facilitating filtration; these compounds therefore present vasomotor effects, probably by an action on catecholamines whose metabolism is modified. Last, nitrates are suspected to be responsible for reproduction troubles, thyroid dysfunction, perturbances of vitamins availability and nutritional effects. Most of the impacts of nitrates and nitrites are now well known, but their cellular of molecular action is not clear, and as a result there is a suspicion in regard to these products very widely present in food.
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PMID:[Toxicologic and nutritional aspects of nitrates and nitrites]. 702 May 46

A large number of studies have indicated associations between particulate air pollution and adverse health outcomes. Wintertime air pollution in particular has been associated with increased mortality. Identification of causal constituents of inhalable particulate matter has been elusive, although one candidate has been the acidity of the aerosol. Here we report measurements of acidic aerosol species made for approximately 1.5 years in Erfurt, Germany, and Sokolov, Czech Republic. In both locations, the burning of high-sulfur coal is the primary source of ambient air pollution. Twenty-four-hour average measurements were made for PM10, [particulate matter with an aerodynamic diameter (da) < or = 10 microns], as well as fine particle (da < 2.5 microns) H+ and SO4(2-) for the entire study. Additionally, separate day and night measurements of fine particle H+, SO4(2-), NO3-, and NH4+ and the gases, SO2, HNO3, HONO, and NH3 were collected with an annular denuder/filter pack system over a 7-month (late winter-summer) period with additional measurements during pollution episodes the following winter. At both sites, 24-hr SO2 (mean concentrations of 52 micrograms/m3, with peak levels of > 585 micrograms/m3) and PM10 (mean concentration 60 micrograms m3) concentrations were quite high. However, aerosol SO4(2-) concentrations (mean concentration of approximately 10 micrograms/m3) were not as great as expected given the high SO2 concentrations, and acidity was very low (mean concentration of < 1 microgram/m3, with peak levels of only 7 micrograms/m3). Low acidity is likely to be the result of NH3 neutralization and slow conversion of SO2 to SO4(2-).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Measurement of acidic aerosol species in eastern Europe: implications for air pollution epidemiology. 765 78

A pH dependent reduction in growth, pigment, ATP content, O2- evolution, carbon fixation, photosynthetic electron transport system, nutrient uptake (NO3- and NH4+), nitrate reductase, and ATPase activities and increase in K+ efflux of Chlorella vulgaris was noticed following supplementation of Cu and Ni to the culture medium. PS II was found to be more sensitive to both pH and metals than PS I. Though, nitrate reductase (NR) was more sensitive to both pH and metals, the ATPase was however, more sensitive to metals but less sensitive to acidic pH. Acid pH was found to inhibit the nutrient (NO3- and NH4+) uptake and nitrate reductase in a non-competitive manner. The inhibition produced by the test metals alone was of non-competitive type for NO3- uptake, nitrate reductase and ATPase and competitive for NH4+ uptake. Acidity not only inhibited the metabolic variables directly but also through facilitated uptake of metals and increased membrane permeability. A very low sensitivity of ATPase to acidic pH seems to be responsible for the survival of algae in acid environment.
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PMID:Effect of Cu and Ni on growth, mineral uptake, photosynthesis and enzyme activities of Chlorella vulgaris at different pH values. 802 20

This study concerns the inhibitory effects of acid pH and nickel on growth, nutrient (NO3- and NH4+) uptake, carbon fixation, O2 evolution, electron transport chain and enzyme (nitrate reductase and ATPase) activities of acid tolerant and wild-type strains of Chlorella vulgaris. Though a general reduction in all these variables was noticed with decreasing pH, the tolerant strain was found to be metabolically more active than the wild-type. A reduced cation (NH4+, Na+, K+ and Ca2+) uptake, coupled with a facilitated influx of anions (NH4+, PO4(3-) and HCO3-), suggested the development of a positive membrane potential in acid tolerant Chlorella. Nevertheless, a tremendous increase in ATPase activity at decreasing pH revealed the involvement of superactive ATPase in exporting H+ ions and keeping the internal pH neutral. A difference in Na+ and K+ efflux of the two strains at decreasing pH suggests there is a difference in membrane permeability. The low toxicity of Ni in the acid tolerant strain may be due to the low Ni uptake brought about by a change in membrane potential as well as in permeability. Hence, the development of superactive ATPase and a change in both membrane potential and permeability not only offers protection against acidity, but also co-tolerance to metals.
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PMID:Effect of nickel on certain physiological and biochemical behaviors of an acid tolerant Chlorella vulgaris. 814 21

The quality of tomato fruit and juice (Lycopersicon esculentum L. cv. VF M82-1-8) grown in an aerohydroponic system in a greenhouse was affected by the level of Cl- and NO3-, and by the osmotic potential (OP) of the nutrient solutions. The total suspended solids (degrees Brix) in the fresh juice increased from approximately 4.0 in the nonsaline solutions (OP approximately -0.05 MPa) to approximately 5.6-5.8 in the saline solutions (OP approximately -0.45 MPa). Juice acidity was similarly affected by the Cl-, NO3- and OP levels in the nutrient solutions. Less affected, the ascorbic acid content of juice, was lowest (approximately 8-9 mg/100 cc) in the high-NO(3-) -nonsaline solution treatments, and was between 10 and 12 mg/100 cc at OP levels greater than approximately -0.2 MPa. NO3- in the juice was high (approximately 60 mg/L) under low OP conditions (approximately -0.05 to -0.1 MPa), especially when combined with high NO3- levels, and lower (between 8 and 30 mg/L) in plants exposed to saline conditions (low OP). Fruit puffiness (boxiness) was reduced markedly by salinity and was not considerably affected by the NO3-/Cl- ratio, while fruit firmness was influenced by both factors.
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PMID:The quality of tomato for canning as affected by combined chloride, nitrate and osmotic potential of the nutrient solution. 850 35

Twenty-four-hour samples of PM10 (mass of particles with aerodynamic diameter < or = 10 microm), PM2.5, (mass of particles with aerodynamic diameter < or = 2.5 microm), particle strong acidity (H+), sulfate (SO42-), nitrate (NO3-), ammonia (NH3), nitrous acid (HONO), and sulfur dioxide were collected inside and outside of 281 homes during winter and summer periods. Measurements were also conducted during summer periods at a regional site. A total of 58 homes of nonsmokers were sampled during the summer periods and 223 homes were sampled during the winter periods. Seventy-four of the homes sampled during the winter reported the use of a kerosene heater. All homes sampled in the summer were located in southwest Virginia. All but 20 homes sampled in the winter were also located in southwest Virginia; the remainder of the homes were located in Connecticut. For homes without tobacco combustion, the regional air monitoring site (Vinton, VA) appeared to provide a reasonable estimate of concentrations of PM2.5 and SO42- during summer months outside and inside homes within the region, even when a substantial number of the homes used air conditioning. Average indoor/outdoor ratios for PM2.5 and SO42- during the summer period were 1.03 +/- 0.71 and 0.74 +/- 0.53, respectively. The indoor/outdoor mean ratio for sulfate suggests that on average approximately 75% of the fine aerosol indoors during the summer is associated with outdoor sources. Kerosene heater use during the winter months, in the absence of tobacco combustion, results in substantial increases in indoor concentrations of PM2.5, SO42-, and possibly H+, as compared to homes without kerosene heaters. During their use, we estimated that kerosene heaters added, on average, approximately 40 microg/m3 of PM2.5 and 15 microg/m3 of SO42- to background residential levels of 18 and 2 microg/m3, respectively. Results from using sulfuric acid-doped Teflon (E.I. Du Pont de Nemours & Co., Wilmington, DE) filters in homes with kerosene heaters suggest that acid particle concentrations may be substantially higher than those measured because of acid neutralization by ammonia. During the summer and winter periods indoor concentrations of ammonia are an order of magnitude higher indoors than outdoors and appear to result in lower indoor acid particle concentrations. Nitrous acid levels are higher indoors than outdoors during both winter and summer and are substantially higher in homes with unvented combustion sources.
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PMID:Indoor, outdoor, and regional summer and winter concentrations of PM10, PM2.5, SO4(2)-, H+, NH4+, NO3-, NH3, and nitrous acid in homes with and without kerosene space heaters. 1006 53


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