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PubMedDate not supplied

Method to detect minimal amounts of calcium dissolved in acidic solutions.

The study describes the application of the Arsenazo III method for detection of minimal amounts of calcium 12.4-49.4 micromol/l in different acidic solutions (hydrochloric acid, oxalic acid, maleic acid, phosphoric acid, tartaric acid, citric acid, lactic acid and acetic acid) adjusted to pH 2.0, 2.3 and 3.0. A mixture of the respective calcium concentrations with distilled water served as control. The experiments were run with ten repeats in series. Assessment of intra- and interassay coefficient of variation, and lower limit of quantification revealed that depending on the acid used, the Arsenazo III method is a reliable tool to quantify minimal calcium contents in acidic solutions.

Arsenazo III↗
PubMed1994

GLUCOSE METABOLISM BY SEA RAVEN (HEMITRIPTERUS AMERICANUS) AND RAINBOW TROUT (ONCORHYNCHUS MYKISS) ERYTHROCYTES

The fate of extracellular glucose in blood isolated from sea raven (Hemitripterus americanus) and rainbow trout (Onchorhynchus mykiss) was determined. In blood from both species incubated in vitro at low physiological pH, the decrease in plasma glucose concentration was more than adequate to support oxygen consumption. Glucose disappearance could not be accounted for by increases in lactate, red blood cell (RBC) glucose or RBC glycogen concentrations. Rates of 14CO2 production from [6-14C]glucose over a 2 h incubation period were less than 1 % of metabolic rate. Only small amounts of label appeared in RBC protein, lipid or glycogen fractions relative to metabolic rates, but label accumulated in the intracellular acid-soluble fraction (presumably free glucose, glycolytic intermediates, amino acids, citric acid cycle intermediates, etc.) at rates consistent with oxygen consumption and glucose disappearance. The simplest explanation for the mismatch between 14CO2 production and the other estimates of metabolic rate is that incubation times were too short for equilibration to occur. A consequence is that studies of this nature cannot use 14CO2 production to elucidate rates of aerobic fuel utilization. By default, the data imply that glucose serves as a primary aerobic metabolic fuel for the RBCs, at least under some conditions.

Journal Article↗
PubMed2003

Improvement of physicochemical properties of N-4472. Part III. VC/N-4472 complex formation and self-association in aqueous solution.

To improve the aqueous solubility of a poorly water-soluble drug, N-[2-(3,5-di-tert-butyl-4-hydroxyphenethyl)-4,6-difluorophenyl]-N'-[4-(N-benzylpiperidyl)]urea (N-4472), organic acid/N-4472 evaporates were prepared by using succinic acid, L-tartaric acid, citric acid and L-ascorbic acid (VC). Among these evaporates, only the VC/N-4472 evaporate at a molar ratio of more than 2 (VC/N-4472) formed stable colloidal particles (with a mean particle size <or=100 nm) in aqueous solution. In particular, the evaporate prepared at the molar ratio of 5 (VC/N-4472) formed a clear solution comprising fine particles with a narrow particle size distribution of 8-15 nm. On the basis of surface tension measurement, zeta potential determination and static light scattering measurement, it was conceivable that both N-4472 and VC contributed to the formation of a surface-active complex in aqueous solution, while the colloidal particles could be interpreted as the self-association product of these complexes. According to the findings on (1)H-NMR and attenuated total reflectance Fourier transform infrared spectra, it was postulated that upon combining both components at a molar ratio of 2 (VC/N-4472), a 1 : 1 association complex of N-4472 and VC was formed, whereas the higher order complexes were assumed formed with use of a molar ratio of more than 2 (VC/N-4472). Furthermore, it was evidenced that all of these complexes were composed of amphiphilic structures comprising both hydrophobic N-4472 moiety and hydrophilic VC moiety, thereby properly accounting for surface-active property of these complexes.

Acids↗
PubMedDate not supplied

Stability constants for the complexation of various metals with a rhamnolipid biosurfactant.

The presence of toxic metals in natural environments presents a potential health hazard for humans. Metal contaminants in these environments are usually tightly bound to colloidal particles and organic matter. This represents a major constraint to their removal using currently available in situ remediation technologies. One technique that has shown potential for facilitated metal removal from soil is treatment with an anionic microbial surfactant, rhamnolipid. Successful application of rhamnolipid in metal removal requires knowledge of the rhamnolipid-metal complexation reaction. Therefore, our objective was to evaluate the biosurfactant complexation affinity for the most common natural soil and water cations and for various metal contaminants. The conditional stability constant (log K) for each of these metals was determined using an ion-exchange resin technique. Results show the measured stability constants follow the order (from strongest to weakest): Al3+ > Cu2+ > Pb2+ > Cd2+ > Zn2+ > Fe3+ > Hg2+ > Ca2+ > Co2+ > Ni2+ > Mn2+ > Mg2+ > K+. These data indicate that rhamnolipid will preferentially complex metal contaminants such as lead, cadmium, and mercury in the presence of common soil or water cations. The measured rhamnolipid-metal stability constants were found in most cases to be similar or higher than conditional stability constants reported in the literature for metal complexation with acetic acid, oxalic acid, citric acid, and fulvic acids. These results help delineate the conditions under which rhamnolipid may be successfully applied as a remediation agent in the removal of metal contaminants from soil, as well as surface waters, ground water, and wastestreams.

Environmental Pollutants↗
PubMed1976

Carnitine concentration in relation to enzyme activities and substrate utilization in human skeletal muscles.

The relationships between the carnitine concentration and enzyme activities representative of different metabolic pathways, glycogenolysis, glycolysis, beta-oxidation of fatty acids, citric acid cycle, and respiratory chain were studied in skeletal muscle tissue from 18 volunteering subjects. In addition, the in vitro incorporation rates of glucose-carbon and palmitate-carbon into different metabolites, and the concentration of glycogen, triglycerides, and phospholipids were determined in the same tissue specimen. The carnitine concentration correlated positively and statistically significantly with the activities of 3-OH-acyl-CoA dehydrogenase and citrate synthase, with the incorporation rate of palmitate-carbon into CO2, and the incorporation rate of glucose-carbon into lactate in the muscle tissue. The results indicate a coupling between the concentration of carnitine and the capacity for long-chained fatty acid oxidation in human skeletal muscles.

Adult↗
PubMed1976

The effects of ascorbic acid on diphtheria toxin and intoxicated HeLa cells.

Ascorbic acid (vitamin C) prevented diphtheria toxin from inhibiting the incorporation of [U-14C]-alanine into trichloroacetic acid precipitable material in HeLa cells. Ascorbic acid did not exhibit an effect on the adenosine diphosphate-ribosylation of amino acyl transferase II nor did it separate fragment A from fragment B in "nicked" toxin. A non-specific reducing agent, para-methylaminophenol sulfate, exhibited an effect on HeLa cells very similar to the results of ascorbic acid. Citric acid, a tricarboxylic acid, had no effect on HeLa cells.

Alanine↗
PubMed2000

[Physicochemical and microbiological evaluation of 3 commercial guava jams (Psidium guajava L.)].

Four different production batches were taken from each brand. Samples were purchased from retail markets in Maracay, Cagua and Turmero. (Venezuela). The average physical and chemical values were: vacuum = 38.81 cm Hg; pH = 3.28; titrable acidity (%citric acid) = 0.59%; degree Brix = 67.24; reducing sugars = 55.28%; total sugars = 62.28, and the color parameters a = +14.44, b = +8.77 and L = 17.09. Molds, yeast and aerobic plate counts were lower than 10 UFC/g; it reveals an excellent microbiological quality of the product. The studied jams degree Brix and acidity fulfil COVENIN (1) requirements for jam products, but not pH range. In agreement with variance analysis, there were highly significance differences between the samples and among the shares of each sample for all physical and chemical properties evaluated.

Analysis of Variance↗
PubMed2002

[On-line determination of transitional metal ions by low-pressure ion chromatography with chemiluminescence detection].

The separation and determination of five transitional metal ions, Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ by low-pressure ion chromatography with chemiluminescence detection were investigated for the first time. The separation was carried out on a C3 ion chromatographic column by using a step gradient elution with the mobile phase of oxalic acid-citric acid solution. The five transitional metal ions could be separated simultaneously. Luminol-H2O2-Mn+ system was used as the flow injection chemiluminescence analytical system. Under the optimum conditions with 0.5 mmol.L-1 luminol, 0.05 mol.L-1 H2O2 and 0.020 mol.L-1 NaOH, the linear ranges (mg.L-1) for Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ were 0.001-0.1, 0.1-6, 0.06-4, 0.03-5 and 0.025-1 respectively; the detection limit (microgram.L-1) for Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ were 0.85, 85, 42, 21 and 20. The present method is simple, rapid, accurate and has been successfully applied to detect Co2+ in vitamin B12 and Co2+, Cu2+, Mn2+, Fe2+ and Cr3+ in human hair sample with satisfactory results, which were in good agreement with those from atomic absorption spectrometry.

Chromatography, Ion Exchange↗
PubMed1992

[Effects of pH on the endocrine system and metabolism].

Changes in extra- and intracellular pH affect metabolic states and hormone responses. In general, alkalosis stimulates and acidosis inhibits glycolysis although the relationship is not a simple one. 6-phosphofructo-1-kinase, a rate limiting enzyme in glycolysis, seems to be activated directly by a rise in pH. Alkalosis stimulates the production of pyruvic acid and lactic acid. Citric acid cycle is stimulated in alkalosis and hexose monophosphate shunt pathway is facilitated in acidosis. Acid-base disorders affect the insulin secretion and insulin action. In acidosis, insulin action in the target tissues is reduced. Other hormones, including parathormone, renin-angiotensin-aldosterone system, and adrenocorticotropine, respond to the changes in pH.

Acid-Base Imbalance↗
PubMed1991

Pharmacokinetics of a novel dopamine DA1 receptor agonist, E4101, and an improvement of its bioavailability in dogs.

Pharmacokinetic parameters of E4101,(-)-(3R,4R)-3-(2-chloro-3-hydroxyphenyl)- 4-(3,4-dihydroxyphenyl)-pyrrolidine hydrochloride, in plasma were determined in conscious beagles. E4101 was extracted from plasma using a Bond Elute C18 cartridge and determined by HPLC connected to a reverse phase ODS column and an electrochemical detector. After an i.v. administration of 1 mg/kg, the plasma level of E4101 decreased according to the three compartment model. The half lives of the alpha, beta and gamma phases were 1.3, 8.1 and 27 min, respectively. The mean residence time (MRT) and total clearance were 14.5 min and 78 ml/min/kg, respectively. When 3 mg/kg of E4101 were administered orally under fasting, E4101 in plasma reached the peak (Cmax: 22.4 ng/ml) 45 min after administration. The bioavailability was 3.6%. When 3 mg/kg of E4101 in combination with 15 mg/kg of ascorbic acid was orally administered in capsule, the area under concentration curve (AUC) was increased 7-fold compared with that in a matched control study. A combination with 15 mg/kg of tartaric acid, citric acid, L-aspartic acid or L-cysteine also increased the AUC, byt they were less effective than ascorbic acid. When 10 mg/kg of E4101 in combination with 25 mg/kg of ascorbic acid as a sustained-release dosage form using oily somisolid matrix orally administered to non-fasted beagles, the duration of effective plasma concentration (2 ng/ml plasma in i.d. administration) was 8.4 +/- 1.0 hr (mean +/- SE, n-4). The Cmax was 16.2 +/- 2.5 ng/ml.

Animals↗
PubMed1990

Feeding trial in pigs with a diet containing sodium n-butyrate.

Pigs weighing 7 to 102 kg were fed a diet containing 0.17% sodium n-butyrate. The diet increased the average daily body mass gain of pigs by 23.5%. Due to its dietetic effect, feed consumption increased by 8.9%. However, owing to the higher feed conversion, specific feed utilization was reduced by 11.8%. The experimental diet markedly reduced the percentile proportion of coliform bacteria in the ileum as compared to Lactobacillus ssp.: it decreased the coliform count and increased the counts of Lactobacillus spp. The diet increased the length of ileal microvilli and the depth of caecal crypts. It raised the concentration of immunoreactive insulin in the blood plasma. The feed supplemented with sodium butyrate did not alter adversely the clinical indices tested. It reduced feed costs by 9% and increased the returns from sales by 13%. As the additive is normally produced by microbial fermentation in the large intestine, it is not alien to the body. Sodium butyrate exerted its favourable effect in 3.6- to 24.2-fold lower concentrations than the organic acids (citric acid, fumaric acid, propionic acid) used earlier. With respect to its favourable biological and economic effect, sodium n-butyrate can be recommended for use in pig feeding as a growth promoter.

Animal Feed↗
PubMed1978

[Reaction kinetic studies on the formation of n-nitrosoephedrine in vitro and in vivo (author's transl)].

N-Nitrosoephedrine was synthesized at a high yield (greater than 90%). The influence of pH on the reaction process (ephedrine sulfate + nitrous acid in hydrochloric acid) was investigated and the pH-optimum determined. Furthermore the influence of coffee, ascorbic acid, citric acid, cyclamate/saccharin (10:1), smoke condensate of cigarettes, glucose and ethanol on the reaction process was also determined. The tests with animals (rats) showed that N-nitrosoephedrine could be detected in serum after the oral application of ephedrine sulfate and sodium nitrite.

Animals↗
PubMed1979

[Late development of human dental enamel].

Planes of longitudinal fractures of human dental enamel observed in scanning electron microscopy showed morphological variations related to age. This late maturation was observed along the enamel sheaths which disappeared in the subsurface and decreased in the rest of the structure. The destructions produced by demineralizing substances (phosphoric acid, citric acid, EDTA) were always more severe in enamel of older teeth when compared to younger samples. A pretreatment of the fragments with a urea solution increased the acid effects only in young enamel. It is suggested that the late maturation of enamel consists in a reduction of matrix components.

Acid Etching, Dental↗
PubMed1978

Evaluation of the co-immobilized hexokinase/glucose-6-phosphate dehydrogenase method for glucose, as adapted to the Technicon SMAC.

We assessed the analytical performance of the co-immobilized hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) method for D-glucose analysis on the Technicon SMAC. The enzyme-containing coils were usable for one month, or 12 000 tests. Bilirubin, hemoglobin, lipemia, creatinine, uric acid, citric acid, and ascorbic acid did not interfere. Results with this method were compared to those by the National Glucose Reference Method. The upper limits of the total error estimate (a combination of random and systematic errors) were 76, 74, and 125 mg/liter at concentrations of 500, 1200, and 3000 mg/liter, respectively. The error estimates were less than allowable errors based on medical usefulness; thus the method was judged to perform acceptably with respect to the Reference Method. We also present performance data for the routine SMAC glucose oxidase (EC 1.1.3.4)/Peroxidase (EC 1.11.1.7) 3-methyl-2-benzothianolinone hydrazone-N,N-dimethylaniline method, the direct hexokinase method with the Du Pont aca, and the glucose oxidase oxygen-rate method with the Beckman Glucose Analyzer.

Autoanalysis↗
PubMed1995

Standardized method for high-resolution 1H-NMR of cerebrospinal fluid.

This study describes a standardized method for recording single-pulse 1H-nuclear magnetic resonance (1H-NMR) spectra from cerebrospinal fluid (CSF). Quantitative data for alanine, valine, threonine, and lactic acid correlated well with data obtained with conventional techniques. The pH of the samples is important for the reproducibility of the chemical shift of resonances, and should be standardized to improve recognition and assignment of resonances. A database of resonances from various metabolites is presented. Fifty compounds could be identified in CSF, 15 of which had not been observed earlier in NMR studies of CSF. We describe for the first time in the literature, to our knowledge, 3-hydroxyisovaleric acid as a regular component of many CSF samples. As examples of the diagnostic power of the technique, spectra are shown of CSF from patients with three different inborn errors of metabolism. We found high concentrations of N-acetylaspartic acid, citric acid, and succinic acid in CSF from a patient with Canavan disease. This is indirect evidence for the existence of a carrier mechanism that is shared by these di- and tricarboxylic acids.

Adult↗
PubMed2003

Effects of tooth-conditioning agents on bond strength of a resin-modified glass-ionomer sealant to enamel.

OBJECTIVES: The purpose of this study was to evaluate the effects of tooth-conditioning agents on bond strength of resin-modified glass-ionomer sealant (Fuji III LC) to bovine enamel as well as on dissolution of calcium ions from the bovine enamel surfaces. METHODS: The enamel surfaces of bovine lower incisors were treated with 10 and 20% polyacrylic acid, 12% citric acid and 35% phosphoric acid for 20s. Fuji III LC was applied to the etched enamel surfaces, and the shear bond strength of each specimen was measured using an Instron Universal Testing Instrument. The amounts of calcium ions dissolved from the treated enamel surfaces were also measured using a polarized Zeeman atomic absorptiometer. RESULTS: In specimens pretreated with distilled water, 10% polyacrylic acid, 20% polyacrylic acid, 12% citric acid and 35% phosphoric acid, the mean values of shear bond strength were 5.5, 12.5, 15.2, 15.2 and 15.1MPa, respectively, and the amounts of Ca(2+) dissolved from the enamel surfaces were 5.6, 41.4, 88.5, 131.6 and 588.3 microg/cm(2), respectively. CONCLUSIONS: The adhesion of a resin-modified glass-ionomer sealant to bovine enamel was significantly improved by the use of tooth-conditioning agents. Especially, treatment of an enamel surface with 20% polyacrylic acid results in good shear both strength and relatively small degree of enamel erosion.

Acid Etching, Dental↗
PubMed1997

Overexpression of cytosolic malate dehydrogenase (MDH2) causes overproduction of specific organic acids in Saccharomyces cerevisiae.

Saccharomyces cerevisiae accumulates L-malic acid through a cytosolic pathway starting from pyruvic acid and involving the enzymes pyruvate carboxylase and malate dehydrogenase. In the present study, the role of malate dehydrogenase in the cytosolic pathway was studied. Overexpression of cytosolic malate dehydrogenase (MDH2) under either the strong inducible GAL10 or the constitutive PGK promoter causes a 6- to 16-fold increase in cytosolic MDH activity in growth and production media and up to 3.7-fold increase in L-malic acid accumulation in the production medium. The high apparent Km of MDH2 for L-malic acid (11.8 mM) indicates a low affinity of the enzyme for this acid, which is consistent with the cytosolic function in the enzyme and differs from the previously published Km of the mitochondrial enzyme (MDH1, 0.28 mM). Under conditions of MDH2 overexpression, pyruvate carboxylase appears to be a limiting factor, thus providing a system for further metabolic engineering of L-malic acid production. The overexpression of MDH2 activity also causes an evaluation in the accumulation of fumaric acid and citric acid. Accumulation of fumaric acid is presumably caused by high intracellular L-malic acid concentrations and the activity of the cytosolic fumarase. The accumulation of citric acid may suggest the intriguing possibility that cytosolic L-malic acid is a direct precursor of citric acid in yeast.

Citric Acid↗
PubMed1996

N-terminal sequence of amino acids and some properties of an acid-stable alpha-amylase from citric acid-koji (Aspergillus usamii var.).

An acid-stable alpha-amylase (AA) was purified from an acidic extract of citric acid-koji (A. usamii var.). The N-terminal sequence of the first 20 amino acids of the enzyme was identical with that of AA from A. niger, but the two enzymes differed in molecular weight. HPLC analysis for identifying the anomers of products indicated that the AA hydrolyzed maltopentaose (G5) at the third glycoside bond predominantly, which differed from Taka-amylase A and the neutral alpha-amylase (NA) from the citric acid-koji.

Amino Acid Sequence↗