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

Liver and kidney slices prepared 30min after intravenous injections of formaldehyde-treated 125I-labelled bovine serum albumin into mice degrade approx. 25-40% of the protein to a trichloroacetic acid-soluble form during 60min incubation at 37 degrees C. The presence of bicarbonate in Krebs-Ringer phosphate medium inhibited intracellular proteolysis, and similar results were obtained at pH5 or pH7 in kidney or liver slices. Cellular integrity was required to obtain substantial rates of proteolysis. This intralysosomal intracellular degradation of an exogenous protein was partially inhibited by inhibitors of oxidative ATP formation, such as cyanide, azide, 2,4-dinitrophenol and absence of oxygen. Arsenite and iodoacetamide were also effective inhibitors, but the effects of fluoride were variable. These results suggest that an energy requirement exists for intralysosomal proteolysis in intact cells and are consistent with the hypothesis that energy may be required to maintain intralysosomal acidity.
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PMID:An energy requirement for the degradation of intravenously injected 125I-labeled albumin in mouse liver and kidney slices. 66 41

Acid fog is complex and contains multiple stimuli that may be capable of inducing bronchoconstriction. These stimuli include sulfuric and niric acids, the principal inorganic acids present; sulfites, formed in the atmosphere as a reaction product of sulfur dioxide and water droplets; fog water itself, a hypoosmolar aerosol; the organic acid hydroxymethanesulfonate, the bisulfite adduct of formaldehyde; and gaseous pollutants, e.g., sulfur dioxide, oxides of nitrogen, ozone. Given this complexity, evaluation of the respiratory health effects of naturally occurring acid fog requires assessment of the bronchoconstrictor potency of each component stimulus and possible interactions among these stimuli. We summarize the results of three studies that involve characterization of the bronchoconstrictor potency of acid fog stimuli and/or their interaction in subjects with asthma. The results of the first study indicate that titratable acidity appears to be a more important stimulus to bronchoconstriction than is pH. The results of the second study demonstrate that sulfite species are capable of inducing bronchoconstriction, especially when inhaled at acid pH. The results of the third study suggest that acidity can potentiate hypoosmolar fog-induced bronchoconstriction.
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PMID:Potential bronchoconstrictor stimuli in acid fog. 253 89

The influence on the area and numerical density of nuclei was investigated in 5-mm-thick slices of guinea pig liver for different fixatives and variations in tissue processing: delay in fixation, air drying, degree of acidity of 10% formalin (= 4% formaldehyde), Bouin and mercury-formalin fixatives, acetone and ethanol dehydration and understretching and overstretching of the paraffin-embedded sections. Air drying (either forced or as a result of delayed fixation), the type of fixative and the degree of acidity affected the nuclear area. Regarding the latter, nuclear area was approximately 25% lower for pH less than or equal to 3 as compared with pH greater than 5. In comparison with the standard tissue processing used, the nuclear density was higher after all of the variations studied (air drying, acetone dehydration and fixation). These findings indicate that nuclear area, in contrast to other tissue components, is relatively insensitive to variations in tissue processing. However, it is essential to regularly measure the pH of the fixative: deviations from pH = 7 should be carefully avoided in order to keep nuclear area variations as a result of tissue processing within acceptable limits.
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PMID:The influence of fixatives and other variations in tissue processing on nuclear morphometric features. 266 81

Seven phages were fairly susceptible in vitro to the lethal effect of acidified whey, more so than the enteropathogenic Escherichia coli strains on which they were active. The low acidity that prevailed in the abomasum contents of calves shortly after a milk feed had little harmful effect on orally administered organisms of these phages; they flooded into the small intestine. The high acidity that prevailed later was lethal to orally administered phage organisms; few entered the small intestine. The lethal effect could be counteracted by giving CaCO3 in the feed. Low concentrations of phage-neutralizing antibodies were found in some serum samples from human beings, cattle and pigs. Antibodies to one of the seven phages were common in the human samples and antibodies to another, phage B44/1, were common in the cattle and pig samples and in bovine colostrum. Phage B44/1 antibodies in a sample of colostral whey were destroyed at pH 3.25 or less. Giving colostrum containing phage B44/1 antibodies with CaCO3 to a calf greatly reduced the numbers of orally administered phage B44/1 organisms in its alimentary tract. Antibodies to another phage were induced in the serum of a calf suffering from E. coli diarrhoea by treating it with that phage. The phages were as susceptible as the E. coli strains to the lethal action of formaldehyde and sodium hypochlorite. In contrast to the E. coli strains, they were almost completely resistant to phenol and chloroxylenol. The in vitro virulence of 21 phages varied according to the temperature at which tests were performed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Factors influencing the survival and multiplication of bacteriophages in calves and in their environment. 330 78

Migration of melamine and formaldehyde into food-simulating solvents from cups made of melamine resin was studied under various conditions. Little migration of melamine was observed in any unused cups kept at 60 degrees C for 30 min, room temperature (26 degrees C) for 1 h or cooled at -20 degrees C for several days. Migration of both compounds was strongly affected by heating and acidity. The highest migration of melamine into 4% acetic acid used as a food-simulating solvent was 42.9 +/- 7.2 ppm when the migration test was repeated seven times at 95 degrees C for 30 min. In this time, the migration of formaldehyde was 14.2 +/- 0.6 ppm into the solvent. The molecular ratio of the migration amount of formaldehyde to melamine decreased according to the formula Y = 9.15X-0.813 over seven repetitions of the test, and was maintained at about 1.6 between the 10th and 20th repetitions. The inner surface of the cups became tarnished during the repetition of the test and their roughness increased from 1 micron before the test to 2.5-5 microns after 20 repetitions of the test. Migration of melamine from the cups being used at a cafeteria was 0.4 +/- 0.5 ppm, but that of formaldehyde was undetectable when the cups were kept at 60 degrees C for 30 min with 4% acetic acid.
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PMID:Migration of melamine and formaldehyde from tableware made of melamine resin. 395 95

A new method specific for the determination of subpicomole quantities of tryptophan has been developed by elaboration of the Pictet-Spengler reaction. It permitted reproducible quantitation of tryptophan in less than 1 microliter of plasma ultrafiltrate or 1 mg of brain tissue. Samples deproteinized by trichloroacetic acid were boiled for 15 min with formaldehyde and potassium ferricyanide at controlled acidity, where tryptophan was converted to a single new product identified as 9-hydroxymethyl-beta-carboline. It was quantitated by either direct spectrofluorometry or a reversed-phase HPLC system developed for beta-carbolines. Under our conditions, peptides containing N-terminal tryptophan such as Trp-Leu and delta sleep-inducing peptide gave N-(9-hydroxymethyl-beta-carboline-3-carbonyl) peptides which retained all amino acid residues except tryptophan.
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PMID:Picomole analyses of tryptophan by derivatization to 9-hydroxymethyl-beta-carboline. 662 80

We evaluated the GMD passive sampler for its suitability to measure six aldehydes over a 7-d period in population exposure studies. The six target aldehydes were formaldehyde, acetaldehyde, acrolein, crotonaldehyde, glyoxal, and methylglyoxal. The GMD sampler contains a silica gel-impregnated cellulose pad coated with 2,4-dinitrophenylhydrazine (DNPH) hydrochloride. This agent reacts with formaldehyde to form a hydrazone that is quantified with a high-performance liquid chromatograph. The GMD sampler was tested for background contamination and aldehyde recoveries after 0, 1, and 7 d of storage. Results indicated that the GMD monitor, as currently manufactured, is suitable for shorter-term sampling (up to 24 h) of formaldehyde and acetaldehyde. It is however not acceptable for sampling of acetaldehyde, acrolein, crotonaldehyde, glyoxal, and methylglyoxal over a 7-d exposure period due to the chemical reactions on the silica gel-impregnated cellulose pad. Glyoxal- and methylglyoxal-DNPH derivatives formed on the cellulose and Teflon-coated glass fiber pads that had been prepared with glycerol under acidic and oxidative conditions. Acrolein- and crotonaldehyde-DNPH derivatives diminish through the reverse reaction of the DNPH derivatives to form free aldehydes under acidic conditions. We showed that the unknown reaction products of acrolein and crotonaldehyde derivatives were not pyrazolines but probably resulted from E/Zisomerization. These conversion reactions are favored in acidic conditions present in either the derivatization solution or the collection medium. The most consistent recovery was obtained on glass fiber pads. In particular, recoveries of crotonaldehyde- and acrolein-DNPH derivatives were increased through the use of a pH 4 buffered derivatization solution. These chemical instability problems were overcome by using a pH 4 buffer (citric acid/sodium citrate) and an alternative hygroscopic agent (1,3-butanediol) in the DNPH derivatization solution. Results with DNPH derivatives from these spiking experiments were further confirmed with gas-phase spiking experiments. We determined the optimal acidity, buffer solution, and concentrations of the buffer solution and 1,3-butanediol for the DNPH derivatization solution. This new formulation of the DNPH derivatization solution can be used for collection of the six target aldehydes over a 7-d sampling period.
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PMID:Evaluation of media and derivatization chemistry for six aldehydes in a passive sampler. 1141 36

A value of k(H) = 1.5 x 10(-)(3) M(-)(1) s(-)(1) has been determined for the generation of simple p-quinone methide by the acid-catalyzed cleavage of 4-hydroxybenzyl alcohol in water at 25 degrees C and I = 1.0 (NaClO(4)). This was combined with k(s) = 5.8 x 10(6) s(-)(1) for the reverse addition of solvent water to the 4-hydroxybenzyl carbocation [J. Am. Chem. Soc. 2002, 124, 6349-6356] to give pK(R) = -9.6 as the Lewis acidity constant of O-protonated p-quinone methide. Values of pK(R) = 2.3 for the Lewis acidity constant of neutral p-quinone methide and pK(add) = -7.6 for the overall addition of solvent water to p-quinone methide to form 4-hydroxybenzyl alcohol are also reported. The thermodynamic driving force for transfer of the elements of water from formaldehyde hydrate to p-quinone methide to form formaldehyde and p-(hydroxymethyl)phenol (4-hydroxybenzyl alcohol) is determined as 6 kcal/mol. This relatively small driving force represents the balance between the much stronger chemical bonds to oxygen at the reactant formaldehyde hydrate than at the product p-(hydroxymethyl)phenol and the large stabilization of product arising from the aromatization that accompanies solvent addition to p-quinone methide. The Marcus intrinsic barrier for nucleophilic addition of solvent water to the "extended" carbonyl group at p-quinone methide is estimated to be 4.5 kcal/mol larger than that for the addition of water to the simple carbonyl group of formaldehyde. O-Alkylation of p-quinone methide to give the 4-methoxybenzyl carbocation and of formaldehyde to give a simple oxocarbenium ion results in very little change in the relative Marcus intrinsic barriers for the addition of solvent water to these electrophiles.
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PMID:Substituent effects on carbocation stability: the pK(R) for p-quinone methide. 1286 76

The oxidation of the terpenes alpha- and beta-pinene, limonene and Delta(3)-carene by hydroxyl radicals has been investigated in a fast-flow reactor coupled to a liquid nitrogen trap for collecting the carbonyl compounds. Identification of the products was performed via 2,4-dinitrophenylhydrazone (DNPH) derivatization of the carbonyls to form the mono- and di-DNPH derivatives, which were analysed by high-performance liquid chromatographic (HPLC)-DAD (diode array detector) and HPLC-mass spectrometry (HPLC-MS). Both electrospray ionization [ESI(-)] and atmospheric pressure chemical ionization [APCI(-)] were suitable for the detection of the DNPH derivatives of formaldehyde, acetaldehyde, myrtanal, campholene aldehyde, perillaldehyde, acetone, nopinone, trans-4-hydroxynopinone and 4-acetyl-1-methylcyclohexene. Also the mono-DNPH derivatives of the dicarbonyl compounds pinonaldehyde, endolim and caronaldehyde could be identified. The MS(2) spectra generated in the ion trap of the mass spectrometer allowed us to distinguish between aldehydes and ketones on the basis of the characteristic fragment ion m/ z 163 for the aldehydes. For the quantitative analysis of the mono-DNPH derivatives, ESI(-) in combination with single ion monitoring (SIM) detection showed the lowest detection limits. For the quantification of the dicarbonyl compounds, the acid-sensitive di-DNPH derivatives had to be formed by keeping the acidity in the acid-catalysed derivatization reaction at about 1.7 mM H(2)SO(4). Detection of these dicarbonyl compounds can only be performed by APCI(-) with somewhat lesser sensitivity than by HPLC-DAD.
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PMID:Study of the carbonyl products of terpene/OH radical reactions: detection of the 2,4-DNPH derivatives by HPLC-MS. 1511 1

Dimethoxymethane was synthesized from the direct oxidation of methanol with high conversion and selectivity over specially designed bifunctional V(2)O(5)/TiO2 catalysts with redox and enhanced acidic character, in which the surface acidity played an essential role for inhibiting the formation of formaldehyde through the enhanced condensation reaction of formaldehyde with methanol to produce dimethoxymethane.
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PMID:Selective oxidation of methanol to dimethoxymethane under mild conditions over V2O5/TiO2 with enhanced surface acidity. 1752 Jan 26


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