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

The concentrations of calcium, magnesium, and zinc were measured by atomic absorption spectrometry. The concentrations of all three cations were found to be strongly correlated with one another and with acidity (pH). Analysis of the relative concentrations in prostatic fluid, split ejaculates, and whole seminal plasma confirmed an almost exclusively prostatic origin of these cations. Semen quality, as judged by motility, vitality, concentration, and morphology of spermatozoa, was inversely related to cation concentrations. Therefore, we recommend adoption of the measurement of seminal divalent cations as part of the routine andrologic examination.
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PMID:The cation composition of the seminal plasma and prostatic fluid and its correlation to semen quality. 2 90

The role of acidity in determining and restricting plant distribution and performance is discussed. In soils especially, a key effect of H+ ion concentration is on the solubility of potentially toxic heavy metals such as aluminum, managenese, zinc, iron, copper, and nickel. Al has been reported from many studies since the 1920's as the key determining toxic factor in acid soils. Some acid-tolerant species have been shown to be especially tolerant of Al, and mechanisms of tolerance have been suggested. Mn is also a commonly toxic factor at soil pH less than 5.0. Calcium has been shown to alleviate Mn toxicity. Low pH soils are also generally low in Ca, K, Na, and P; all essential major elements for plant growth. In lakes and marine situations acidic waters are uncommon as the waters are buffered. Calcium is again ameliorative of metal toxicities. The pH, redox, and valency state are critical in determining nutrient availability and metal speciation. Recent increases in the H+ ion content of precipitation have caused increased acidities of freshwater lakes in Scandinavia and eastern North America, which have depleted biota, including fish populations.
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PMID:Effect of H+ ion activity and Ca2+ on the toxicity of metals in the environment. 3 Dec 77

A comprehensive investigation of the interaction of Zn(II) and Co(II) with the dipeptide glycyl-L-tyrosine has been carried out. The carboxyl, amino, and tyrosyl pKa values, as well as the distribution of solution complexes, have been determined by analytical potentiometry. The amide pKa value was determined by relating the proton magnetic resonance (PMR) titration behavior of the tyrosyl alpha-hydrogen resonance to an H2-acidity function for concentrated solutions of aqueous base. Both metals behave in a qualitatively similar manner, yielding equivalent species as a function of pH. Both metals formed bis-peptide complexes, involving amino and peptide carbonyl coordination near pH = 8, with Zn(II) demonstrating a substantially higher affinity for the ligand. No evidence could be found for direct, metal-promoted phenolic dissociation, although the tyrosyl pKa value was sensitive to metal binding at other loci on the dipeptide molecule. At high pH, both systems ionized two additional protons. In the Co(II) system, these correspond to amide protons. However, it is not entirely clear whether the protons in the Zn(II) system originate from the peptide linkage or metal-bound water molecules.
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PMID:A comparative study of Zn(II) and Co(II) binding to glycyl-L-tyrosine, a pseudosubstrate for carboxypeptidase A. 3 45

Raman difference spectrophotometry reveals that CH3HgII binds quantitatively to N(1) of inosine at pH 8, substituting for the proton. When N(1) is saturated, binding occurs at a second site. Measurements of the 1-H nuclear magnetic resonance spectra of both inosine and of CH3Hg-II are in agreement with the N(1) binding and indicate that the second site for mercuriation is N(7). This second binding reaction is observed to increase the rate of exchange of the C(8) hydrogen with solvent, consistent with results observed for alkylation at N(7). Coordination of the electrophilic CH3Hg-II to N(7) increases the acidity of H(8), facilitating OHminus--catalyzed proton abstraction and reprotonation by themedium. For comparison, the reaction of CH3Hg-II with [8-2-H]inosine has been studied. Displacement of the N(1) hydrogen upon mercuriation of inosine causes a significant electron delocalization into the ring, increasing the basicity of N(7), and accounting for the synergic effect in metal binding observed originally by Simpson. In contrast, 1-methylinosine interacts only slightly with CH3Hg-II at pH 8. Coordination appears to be at N(7), since H(8) again is observed to exchange rapidly with solvent protons. In acidic solution, pH less than 2, binding to inosine is almost quantitative and exclusively to N(7). The behavior of CH3Hg-II is compared with that of Pt(II) and with Ni(II), Co(II), AND Zn(II). A brief comparison is made among ultraviolet absorption spectrophotometry, nuclear magnetic resonance (NMR), and Raman difference spectrophotometry for studying reactions of nucleosides and nucleotides.
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PMID:Heavy metal-nucleoside interactions. Binding of methylmercury(II) to inosine and catalysis of the isotopic exchange of the C-8 hydrogen studied by 1-H nuclear magnetic resonance and raman difference spectrophotometry. 23 79

Six experiments were conducted with male broiler chicks kept in battery brooders to investigate the effects of feeding diets high in copper on the integrity of the gizzard lining. Conventional and corn starch-soy basal diets were used. Slight improvements in body weight gain and/or feed efficiency were observed when the diets were supplemented with 250 p.p.m. copper as as CuSO4-5HSO, but higher levels (500 to 1000 p.p.m.) depressed growth and decreased feed efficiency. Little or no gizzard erosion was seen in birds fed the practical ration without added copper. Gizzard erosion was observed with 250 p.p.m. copper and the severity of the condition increased with higher levels. With the same level of copper supplementation, severity of gizzard erosion was greater when chicks were fed the corn starch-soy diet than when fed the practical diet. Adding 0.5 p.p.m. selenium to the practical diet containing 1000 p.p.m. copper slightly improved the appearance of the gizzard lining, although the subjective scoring index was significantly (P less than 0.05) lower in only one of two experiments. The addition of zinc, vitamin E, and vitamin B12 did not prevent the gizzard damage caused by high copper levels. Severity of gizzard erosion was significantly reduced by adding 0.35% cholic acid to the semipurified diet with 500 p.p.m. copper, but not to the practical diet with 100 p.p.m. copper. There was no correlation between acidity of the gizzard contents and severity of the erosion.
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PMID:Effect of high dietary copper on gizzard integrity of the chick. 93 76

No significant difference in lactic acid content was observed in dood residues removed from the occlusal grooves of rats receiving Purina lab chow or the 62% sucrose cariogenic diet. The incubation of rat saliva with Purina chow, with 62% sucrose diet, or with the 62% sucrose diet supplemented with carbamyl phosphate, egg shell meal, and the trace elements zinc, molybdenum, and chromium produced in 24 hours essentially the same pH surve. The terminaltitratable acidity observed in saliva incubated with the 62% unsupplemented diet, however, was significantly less than that produced in salivary mixtures containing either Purina chow or supplemented sucrose diets.
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PMID:Acidogenic potential of cariogenic and noncariogenic diets in the rat. 105 62

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

Numerous factors seem to affect zinc absorption. Gastric acid secretion has been demonstrated to facilitate iron absorption. The zinc tolerance test (ZTT with ZnSO4 220 mg p.o.) was performed in 11 healthy volunteers to study the effects of administering the acid secretion inhibitor cimetidine (1 g/day p.o. for 3 days) and to evaluate the influence of HCl gastric secretion on zinc absorption in physiological conditions. Zinc absorption was reduced after cimetidine administration (p less than 0.005), suggesting that gastric pH influences zinc absorption. To rule out any direct effect of the drug on zinc absorption in five other healthy adults we further evaluated zinc absorption by using a different H2 antagonist (ranitidine 300 mg/day for 3 days and 300 mg before the test). Cimetidine was also tested in these subjects at half the dosage administered to the first group of subjects. Gastric acidity was monitored at 60-min intervals throughout the test via a nasogastric tube. The areas under the plasma concentration curves for zinc were significantly reduced after ranitidine (p less than 0.01), but not after cimetidine administration. Gastric acid was also reduced after ranitidine, but not after cimetidine (500 mg) administration, suggesting that gastric acid secretion plays a role in the regulation of zinc absorption in man.
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PMID:Inhibition of gastric acid secretion reduces zinc absorption in man. 189 92

Zinc sulfadiazine (ZnSD) 50, 100, 200 mg/kg ig inhibited the formation of gastric ulcer induced by indomethacin, stress and pyloric ligation in rats respectively and showed dose-dependently. ZnSD 200 mg/kg ig accelerated the healing of gastric ulcer induced by acetic acid. ZnSD 25 mg/kg ig was effective in preventing ethanol-induced damage of rat gastric mucosa. The amount of gastric mucus glycoprotein in gastric tissues was increased by ZnSD. In general, ZnSD did not influence the volume of gastric juice and pepsin output, but ZnSD 200 mg/kg ig decreased gastric acidity. In vitro, ZnSD also influenced the neutralization of acid. It is suggested that antiulcer action of ZnSD may be related to its preservation of the gastric mucosal barrier and neutralization of acid.
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PMID:[Anti-gastric ulcer activity of zinc sulfadiazine in rats]. 213 Jun 5

This study evaluated the cytotoxic effects of three common restorative materials on early passage cultured cells derived from human gingiva (HG cells). Other early passage cultured cells derived from human dental pulp tissues (HP cells) and L cells established obtained from mouse subcutaneous tissues, were also examined. Cytotoxicity was assessed according to the uptake of neutral red and dye exclusion with nigrosin. The cytotoxicity was in the order of glass ionomer cement (highest), light cured composite resin and dental amalgam. HG cells were the least sensitive to the materials tested. Both filtration of extracts and addition of serum into the extract affected the cytotoxicity. Glass ionomer cement increased the acidity of the extract, but the two other materials did not. Dissolution of metal ions, aluminium, tin, copper, mercury and zinc occurred from the materials. The extract of the composite resin had a different absorbance. This study disclosed differences in the cellular reaction to the restorative materials. Thus, utilization of early passage cultured cells is necessary for biological evaluation of the dental materials in vitro.
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PMID:[Cytotoxic effects of restorative materials on early passage cultured cells derived from human gingiva (in vitro)]. 213 20


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