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

Renal function was investigated in adult rainbow trout following acute and prolonged exposure to waterborne Ni in moderately hard Lake Ontario water (approximately 140 mgL(-1) as CaCO3). Fish were exposed for 36 days to a sublethal concentration of 442 microg Ni L(-1), followed by 96 h of exposure to 12,850 microg Ni L(-1) (approximately 33% of the 96 h LC50). Prolonged exposure markedly affected only the renal handling of Ni, with no substantial effect on the plasma concentration, urinary excretion rate (UER) or clearance ratio (CR) of Na+, Cl-, K+, Ca2+, Mg2+, inorganic phosphate (P(i)), glucose, lactate, total ammonia (T(amm)), protein and free amino acids (FAA). Glomerular filtration rate (GFR) was reduced by 75% over 96 h of acute Ni challenge in both fish previously exposed to Ni and naive fish, with no significant change in urine flow rate (UFR), suggesting a substantial reduction in water reabsorption to maintain urine flow and water balance. Renal Mg2+ handling was specifically impaired by acute Ni challenge, leading to a significantly increased UER(Mg2+) and significantly decreased plasma [Mg2+] only in naive fish. Previously-exposed fish were well-protected against Ni-induced Mg2+ antagonism, indicating true acclimation to Ni. Only in naive, acutely challenged fish was there an increased UER of titratable acidity (TA-HCO3), net acidic equivalents, P(i), T(amm) and K+. Again, all of these parameters were well-conserved in previously-exposed fish during acute Ni exposure, strongly suggesting that prolonged, sublethal exposure protected against acute Ni-induced respiratory toxicity.
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PMID:Renal function in the freshwater rainbow trout (Oncorhynchus mykiss) following acute and prolonged exposure to waterborne nickel. 1574 51

We analyzed the accumulation of inorganic and organic toxicants in tadpoles from nine populations of the common frog (Rana temporaria) at different altitudes of the Hohe Tauern National Park in Austria). Lead and cadmium concentrations in tadpoles increased with the acidity and metal-to-HCO3(-) ratio in the water exceeding those found in tadpoles from agricultural areas. Organochlorines (DDTs, polychlorinated biphenyls, lindane) and polyaromatic hydrocarbons were present in all of the populations, but only DDTs accumulated significantly compared with the concentrations in their diet.
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PMID:Accumulation of toxicants in tadpoles of the common frog (Rana temporaria) in high mountains. 1607 60

The binding of titanium(IV) to human serum transferrin in 50 mM Tris with 20 mM bicarbonate and 10 mM citrate at pH 7.4 was studied by UV/vis kinetics and by isothermal titration calorimetry. Ti(IV) citrate, [Ti(C6H4O7)3]8-, employed in this study was previously characterized and delivers the metal to transferrin rapidly, allowing the quantification of the intrinsic binding constants for Ti(IV) to the C- and N-sites of transferrin. The results after correcting for blood plasma conditions (pH 7.4, [HCO3-] = 27 mM) reveal that Ti(IV) binds with greater affinity (log K = 26.8 and 25.7) than Fe(III) (log K = 22.5 and 21.4) to transferrin, a finding not previously observed for other examined metal ions. The strength of metal binding to transferrin correlates with the Lewis acidity of the metal. Ti(IV) is more Lewis acidic than Fe(III) and is nearly the same size. The study also reveals that Ti(IV) binds more tightly to one site than the other, and this difference is due to both entropic and enthalpic contributions. The study has implications for the role of transferrin in the anticancer activity of Ti(IV) drugs and the serum binding of Ti(IV) ions released from implants or imaging reagents.
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PMID:Ti(IV) binds to human serum transferrin more tightly than does Fe(III). 1608 31

As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the physical and surface properties of the synthetic carbonate fluoroapatite and mineral francolite retained for this work have been carefully examined. The average particle size of the powdered samples, determined by laser granulometry, is around 30 microm. Their specific surface areas, measured according to the N(2) BET method, are 8.8+/-0.1 and 13.9+/-0.1 m(2).g(-1), respectively, for the synthetic and the mineral compound. The solubility of both solids has been studied under undersaturation initial conditions. The synthetic compound has a solubility product of 10(-103+/-2), but the mineral francolite, which is highly substituted and poorly crystalline, is more soluble and dissolves incongruently. The amphoteric properties of the hydrous carbonate fluoroapatites surfaces have also been investigated through zeta-potential measurements and potentiometric titrations in KNO(3) medium at 25 degrees C. The experimental data have been interpreted using the computer program FITEQL 3.2, applying either the nonelectrostatic or the constant capacitance model. For both solids, the values of the surface acidity constants determined with the two models are very close, suggesting a weak contribution of the electrostatic interactions. Moreover, the more acidic surface of the synthetic compound compared to that of the mineral one is assigned to the differences in crystallinity and chemical composition between the two solids.
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PMID:Surface characterization of synthetic and mineral carbonate fluoroapatites. 1629 Jun 19

Gliclazide is the most commonly used sulfonylurea derivative for NIDDM therapy. Due to its prolonged therapy, there is always a likelihood of its use with other drugs. On the other hand antacids are commonly prescribed to encounter gastric acidity etc. Present paper deals with the in vitro availability studies of gliclazide in presence of antacids. These studies were carried out in simulated gastric juice and in buffer of pH 7.4 at body and accelerated temperature. The antacids used in these studies were aluminum hydroxide, aluminum trisilicate, magnesium oxide, magnesium trisilicate, sodium bicarbonate, calcium carbonate, magaldrate and simethicone (2,4-dimethoxypoly-siloxane). It has been found that in case of magnesium oxide, magnesium trisilicate and sodium bicarbonate, availability of gliclazide was enhanced while in rest of the antacids retarded the availability of gliclazide.
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PMID:In vitro availability of gliclazide in presence of antacids. 1641 65

The in vitro availability studies of glibenclamide in presence of commonly used antacids are present in this paper. Glibenclamide is used for the treatment of Non-Insulin dependent diabetes mellitus. It is a sulfonylurea derivative. Antacids are prescribed to encounter gastric acidity etc. These studies were carried out in simulated gastric juice and in buffer of pH 7.4 at 37 and 48 degrees C. Aluminum hydroxide, aluminum trisilicate, magnesium oxide, magnesium trisilicate, sodium bicarbonate, calcium carbonate, magaldrate and simethicone (2,4-dimethoxypolysiloxane) antacids were used in these studies. It has been observed that in case of magnesium oxide, magnesium trisilicate and sodium bicarbonate, availability of glibenclamide was enhanced while in rest of the antacids retarded the availability of glibenclamide.
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PMID:In vitro availability of glibenclamide in presence of antacids. 1641 96

Generally recognised as save compounds (G.R.A.S) are attractive substitutes to synthetic chemicals in postharvest control diseases. They meet safety requirements, are cheap and able to be integrated with other disease control technologies. Among G.R.A.S compounds, carbonic acid salts have been investigated on carrots, bell pepper, melons, sweet cherries and their efficacy was also evaluated when combined with biological control agents. Moreover, the possibility to use sodium carbonate and sodium bicarbonate to prevent P. digitatum an P. italicum spread on Citrus fruit was studied since the begin of the 20th century. We explored the possibility to extend the use of carbonate-bicarbonate salts on loquat fruit in order to control the pathogens and to extend postharvest life. Loquat is a very perishable fruit, susceptible to decay, mechanical damage, moisture and nutritional losses during its postharvest life. We tested the combined effect of temperature and sodium or potassium carbonate-bicarbonate and ammonium carbonate. The fruit was dipped in the salt solutions at variable concentrations (0.5, 1 and 2% w/v) at 25 or 45 degrees C for two minutes and than stored under shelf life conditions (25 degrees C and 70% RH). Decay, weight loss, pH, titrable acidity and sugar content were detected after twelve days. Preliminary data show that the combined treatments were effective in decay control depending on salts. Best results were obtained with 2% potassium and sodium carbonate solution at 25 degrees C. Weight losses were related to treatment temperature and salts concentrations whereas, no differences were detected in the chemical parameters compared to the control.
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PMID:Carbonic acid salts at 25 or 45 degrees C to control loquat decay under shelf life conditions. 1663 1

Double hydrophilic block copolymers PEG-b-PEI-linear with different PEI block lengths have been examined for CaCO3 mineralization at the air/water interface. The results demonstrated that either PEI length or the solution acidity had a significant influence on the morphogenesis of vaterite crystals at the air/water interface. A possible mechanism for the stratification of CaCO3 vaterite crystals has been proposed. Increasing either PEI length or the initial pH value of the solution will decrease the density of the PEG block anchored on the binding interface and result in exposing more space as binding interface to solution and favoring the subnucleation and stratification growth on the polymer-CaCO3 interface. In contrast, higher density of PEG blocks will stabilize the growing crystals more efficiently and inhibit subnucleation on the polymer-CaCO3 interface, and thus prevent the formation of stratified structures. This study provides an example that it is possible to access morphogenesis of calcium carbonate structures by a combination of a block copolymer with the air/water interface.
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PMID:Double hydrophilic block copolymer controlled growth and self-assembly of CaCO3 multilayered structures at the air/water interface. 1680 Jun 67

Tea is a widely consumed beverage. However, recent studies revealed that there were an increasing number of cases of tea products exceeding the former maximum permissible concentration (MPC) in China for Pb (2 mg kg(-1)). Tea Pb contamination is an issue affecting trade and consumer confidence. Root uptake of Pb could contribute significantly to Pb accumulation in tea leaves due to the strong acidity of many tea garden soils. We conducted pot and field experiments to evaluate the effect of liming on Pb uptake by tea plants on two highly acidic soils (pH3.6). Additions of CaCO(3) significantly increased soil pH by up to 1 unit and decreased soil extractable Pb by up to 32%. Liming resulted in a decrease in the proportion of Pb in the exchangeable and carbonate-bound fractions, with a concurrent increase in the fractions bound to Fe/Mn oxides and residues. Liming significantly decreased Pb concentrations of fine roots, stems and new shoots of tea plants in the pot experiment. In the field experiments, the effect of liming was not significant during the first year following CaCO(3) application, but became significant during the second and third years and Pb concentration in the new shoots was decreased by approximately 20-50%, indicating that liming of acidic tea garden soils is an effective way to reduce Pb contamination of tea. The study also reveals a distinct seasonal variation, with Pb concentration in the new shoots following the order of spring>autumn>summer.
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PMID:Effect of liming and seasonal variation on lead concentration of tea plant (Camellia sinensis (L.) O. Kuntze). 1684 90

Sodium oxide (NaOx) impregnated Engelhard Titanosilicate-10 (ETS-10) molecular sieve catalysts were prepared to enhance the basicity associated with ETS-10 and subsequently investigated for the cycloaddition of carbon dioxide to propylene oxide to produce propylene carbonate. For dry NaOx-modified ETS-10 catalysts that contained no adsorbed water, a maximum yield of propylene carbonate was achieved at a loading of 2.0 excess NaOx species per unit cell. However, the greatest enhancements in the rate of reaction were observed when small amounts of water were adsorbed onto the unmodified ETS-10 catalyst immediately prior to reaction. Surface-bound water appears to enhance the surface Bronsted acidity of the unmodified ETS-10 catalyst via the formation of surface -OH groups at lower water loadings, producing a surface of better-tuned acid-base bifunctional characteristics for the cycloaddition reaction. At levels of hydration greater than 12.5% by mass, the yield of propylene carbonate was further enhanced, but at a smaller rate than that observed at lower rehydration levels, which is more indicative of an enhanced transport effect. Adsorption microcalorimetry of carbon dioxide indicated that, at loadings less than 2.0 NaOx per unit cell, the total uptake of the CO2 adsorption sites required for the reaction were less than in the parent ETS-10 material. However, at higher levels of NaOx occlusion, where the total uptake and strength of the adsorption sites exceeded those observed for the as-received ETS-10 material, the cycloaddition activity of this catalyst suffered due to the reduced pore volume and surface area. It appears that precise tuning of both the surface acidity and basicity is crucial in creating an effective acid-base bifunctional ETS-10 catalyst for the cycloaddition reaction investigated.
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PMID:Effect of water and alkali modifications on ETS-10 for the cycloaddition of CO2 to propylene oxide. 1685 Dec 25


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