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PubMed1987

Iron uptake in Mycelia sterilia EP-76.

The cyclic trihydroxamic acid, N,N',N''-triacetylfusarinine C, produced by Mycelia sterilia EP-76, was shown to be a ferric ionophore for this organism. The logarithm of the association constant k for the ferric triacetylfusarinine C chelate was determined to be 31.8. Other iron-chelating agents, such as rhodotorulic acid, citric acid, and the monomeric subunit of triacetylfusarinine C, N-acetylfusarinine, delivered iron to the cells by an indirect mechanism involving iron exchange into triacetylfusarinine C. In vitro ferric ion exchange was found to be rapid with triacetylfusarinine C. Gallium uptake rates comparable to those of iron were observed with the chelating agents that transport iron into the cell. Ferrichrome, but not ferrichrome A, was also capable of delivering iron and gallium to this organism, but not by an exchange mechanism. Unlike triacetylfusarinine C, the 14C-ligand of ferrichrome was retained by the cell. A midpoint potential of -690 mV with respect to the saturated silver chloride electrode was obtained for the ferric triacetylfusarinine C complex, indicating that an unfavorable reduction potential was not the reason for the use of a hydrolytic mechanism of intracellular iron release from the ferric triacetylfusarinine C chelate.

Biological Transport, Active↗
PubMed2001

Adhesion of a glass-ionomer root canal sealer to the root canal wall.

Glass-ionomer root canal sealer is commonly used because of its chemical bonding and favorable physical characteristics when bonding to dentin. This study was designed to determine the tensile bond strength of a glass-ionomer sealer (Ketac Endo, Espe, Seefeld, Germany) on root canal walls after pretreatment with different conditioners. Flat inner surfaces of root canal specimens were prepared. The specimens were divided into five groups of 10 teeth, and the groups were conditioned with one of the following smear layer removal solutions: 15% EDTA/NaOCl, 10% polyacrylic acid, 35% phosphoric acid, 6% citric acid, and 5.25% NaOCl as a control. Then the exposed root canal areas were coated with Ketac-Endo. Tensile bonding was measured using a universal testing machine until ultimate failure was obtained. The groups that were treated with phosphoric acid and citric acid showed significantly higher bond strengths than the groups that were treated with 15% EDTA and polyacrylic acid (p < 0.05). Bonding to dentin without smear layer removal (NaOCl group) was too low to be measured in the testing apparatus. Scanning electron microscopy confirmed that phosphoric and citric acids were more effective in removing smear layer than EDTA or polyacrylic acid. The result supported the view that pretreatment with phosphoric acid or citric acid should be used in association with glass-ionomer root canal sealer to achieve the most effective removal of the smear layer and to provide better adhesion.

Acid Etching, Dental↗
PubMed2002

[Comparison of effect on S.mutans producing acid ability between organic weak acid and fluoride].

OBJECTIVE: To figure out the effects of organic weak acids, benzoate, citric acid and malic acid on the main cariogenic bacteria S.mutans Ingbritt. To evaluate the possibility of above weak acids as anti-caries reagents. METHODS: S.mutans Ingbritt was inoculated into tryptic soy broth containing different concentrations of fluoride, benzoate, citric acid and malic acid, grew in anaerobic conditions at 37 degrees centigrade for 48h. The final pH values of suspension were measured. RESULTS: Fluoride had best inhibitory effect on S.mutans Ingbritt in low concentrations, whereas other 3 weak acids, benzoate, citric acid and malic acid could inhibit S.mutans Ingbritt in a higher concentrations. The order of effectiveness was fluoride>malic acid>benzoate>citric acid. CONCLUSION: Fluoride has the best inhibitory effect on S.mutans producing acid ability. Though weak acids benzoate, malic acid and citric acid in high concentration had different inhibitory effects on S.mutans Ingbritt, however high concentration of organic acids can make enamel demineralization.

English Abstract↗
PubMed1992

Production of citric and oxalic acids and solubilization of calcium phosphate by Penicillium bilaii.

An isolate of Penicillium bilaii previously reported to solubilize mineral phosphates and enhance plant uptake of phosphate was studied. Using agar media with calcium phosphate and the pH indicator alizarin red S, the influence of the medium composition on phosphate solubility and medium acidification was recorded. The major acidic metabolites produced by P. bilaii in a sucrose nitrate liquid medium were found to be oxalic acid and citric acid. Citric acid production was promoted under nitrogen-limited conditions, while oxalic acid production was promoted under carbon-limited conditions. Citric acid was produced in both growth and stationary phases, but oxalic acid production occurred only in stationary phase. When submerged cultures which normally produce acid were induced to sporulate, the culture medium shifted toward alkaline rather than acid reaction with growth.

Agar↗
PubMed1989

Antimutagenicity of some citrus fruits in Salmonella typhimurium.

The antimutagenic effect of 10 citrus fruit juices was observed against the mutagenicity of N-nitro-o-phenylenediamine (NPD) in TA97a and sodium azide in TA100 tester strains of Salmonella typhimurium using the Ames test. It was noticed that the juices of all these fruits reduced significantly the NPD and sodium azide induced revertant colonies. The inhibitory activity was enhanced if the mutagen and juice were co-incubated for about 30 min at 37 degrees C prior to performing the mutagenicity assay. Dilution with distilled water led to the reduction in the inhibitory activity. The antimutagenic activity of synthetic ascorbic acid or citric acid or combined ascorbic acid and citric acid was also seen. But the results with fruit juices tempted us to believe that in addition to ascorbic acid and citric acid, the presence of other factor(s) possessing antimutagenic properties cannot be ruled out.

Azides↗
PubMed2001

Development of a new calcium phosphate cement that contains sodium calcium phosphate.

A cement powder consisting of sodium calcium phosphate, Na3Ca6(PO4)5, in addition to tetracalcium phosphate and beta-tricalcium phosphate was prepared by pulverizing blocks of 4 wt% sodium-, 11 wt% carbonate-containing apatite samples that were heated at 1700 degrees C for 5 h. When mixed with 30 wt% malic acid or citric acid at a powder liquid ratio of 3:1, the cement set in 3 or 7 min at room temperature with compressive strength being around 52 or 27 MPa. In HeLa-cell cultures, the cement mixed with malic acid was less cytotoxic than the cement mixed with citric acid, which was far less cytotoxic than a commercial carboxylate cement used as a negative control, suggesting malic acid to be superior to citric acid as a liquid in this regard. Similar findings were also obtained with osteoclasts, of which culture experiments clearly suggested that the number of osteoclasts on the cement mixed with malic acid was significantly greater than that on the cement mixed with citric acid. Since osteoclastic response to substrates could be used as a maker in evaluating their bioresorbability associated with osteoclasts, the above finding may suggest that the cement that is to be mixed with malic acid would be more useful as bone substitutes.

Animals↗
PubMed2004

Viscoelastic characterizations of acellular dermal matrix (ADM) preparations for use as injectable implants.

Viscoelastic characteristics of acellular dermal matrix (ADM) preparations with various additives were analyzed with creep curves, stress-strain relationships, and the storage modulus with reference to those of ADM preparations crosslinked with glutaraldehyde. Creep curves for all ADM preparations were determined to comply with the Kelvin-Voigt model. The stress-strain plots of all ADM preparations compared were described as linear. The storage modulus of all ADM preparations was maintained at a nearly constant level throughout the range of oscillating frequencies applied. ADM preparations crosslinked with glutaraldehyde showed that both Young's modulus (E) for the spring part and retardation time (tau) in the Kelvin-Voigt model, and hence viscosity (eta) for the liquid part, increased with an increasing concentration of glutaraldehyde. Higher Young's modulus and viscosity and a greater extent of the "solid" response of ADM preparations crosslinked with glutaraldehyde might have been responsible for the longer persistence that was demonstrated after implantation. The increase in ADM concentration and the addition of various additives to ADM preparations, including alpha-hydroxy acid (citric acid, lactic acid, and glycolic acid) and hyaluronic acid, resulted in similar effects on the viscoelastic characteristics of the ADM preparations, but they were less efficacious than those crosslinked with glutaraldehyde. Among them, increasing ADM concentration to >200 mg/mL and addition of glycolic acid at a concentration of >2% improved the viscoelastic characteristics of the resulting ADM preparations so that their level of persistence was closer to that of material crosslinked with glutaraldehyde. On the contrary, the influence on viscoelastic characteristics of adding PVP greatly differed from that of hyaluronic acid and was only apparent when adding concentrations of PVP of >10%. Similarly, viscoelastic characteristics of the ADM preparations examined were also so sensitive to temperature that the persistence of ADM preparations after implantation at body temperature would deteriorate.

Animals↗
PubMed2003

Structural elucidation of natural 2-hydroxy di- and tricarboxylic acids and esters, phenylpropanoid esters and a flavonoid from Autonoë madeirensis using gas chromatographic/electron ionization, electrospray ionization and tandem mass spectrometric techniques.

The chemical composition of Autonoë madeirensis bulbs was characterized as part of a systematic phytochemical study of this species. The compounds reported were mainly identified on the basis of gas chromatography/electron ionization, electrospray ionization and tandem mass spectrometry. The structures of the pure compounds were also characterized by means of other physical and spectroscopic data (m.p., IR, UV, NMR). The compounds identified were 2-hydroxy di- and tricarboxylic acids and esters (malic acid, citric acid and their methyl and ethyl esters), cis- and trans-hydroxycinnamic esters (methyl and ethyl p-coumarate and methyl ferulate) and a new flavone diglucoside, 7-O-[beta-glucosyl-(1-->2)-O-beta-glucosyl]apigenin, the interglucosidic linkage (1-->2) of which is, to the best of our knowledge, reported for the first time in a diglucoside of apigenin. The results may contribute to the chemotaxonomy of the Autonoë genus and lead to a rapid tool for the systematic characterization of these compounds in plant extracts.

Chromatography, Gas↗
PubMed1980

Effect of polybasic acids on structure of aluminum hydroxycarbonate gel.

The effect of oxalic acid, citric acid, and their sodium salts on the structure of aluminum hydroxycarbonate gel was studied to illustrate the various mechanisms by which polybasic acids interact with aluminum hydroxycarbonate gel. Analysis of changes in the pH-stat titrigram, the carbonate to aluminum ratio, the aluminum content of the supernate following centrifugation, and the adsorption of the organic solute indicates that polybasic acids may: (a) partially neutralize the aluminum hydroxycarbonate gel by a general acid effect, (b) modify the aluminum hydroxycarbonate surface by adsorption of the anionic form of the polybasic acid, (c) extract aluminum by the formation of a soluble complex, and (d) lead to the precipitation of a new crystalline phase.

Aluminum Hydroxide↗
PubMed2006

Liquid chromatographic--cold vapour atomic fluorescence spectrometric determination of mercury species.

Solvent extraction, sonication, and microwave-assisted extractions in the presence of extraction agents (thioacetic acid, citric acid, cysteine, 2-mercaptoethanol, HCl + NaCl, etc.) were tested for the isolation of mercury species. A mixture of 6 M HCl and 0.1 M NaCl was selected as the most suitable extraction agent. The extraction efficiency was about 10% higher and the RSD below 3.3% when microwave-assisted extraction was applied instead of sonication. The liquid chromatography-cold vapour atomic fluorescence spectrometry (LC/CV-AFS) method was optimised and used for separation and determination of inorganic mercury cations and alkylated and arylated mercury species. Isocratic elution at a flow rate of 0.15 mL/min (with a mobile phase containing 0.05% 2-mercaptoethanol (pH = 5) and 7% methanol and with a stepwise increase of methanol content up to 100% MeOH in the 15th min) was used for separation of mercury species on a Hypersil BDS C18 RP column. The limits of detection of the LC/CV-AFS system were estimated as 0.2 microg/L (3%) for MeHg+, 0.07 microg/L (5.3%) for inorganic Hg, 0.06 microg/L (3.4%) for PhHg+, and 0.12 microg/L (4.4%) for EtHg with the corresponding RSDs at 5 microg/L (n = 10) given in parentheses. The concentrations (2-10 mg/kg fresh weight) of total mercury and methylmercury (90-99% of the total mercury) in selected fish obtained by HPLC/CV-AFS were in good agreement (absolute deviations 0.05 mg/kg) but more precise (RSDs <5.4% at 5 mg/L, n = 10) than those determined by GC coupled to an electron capture detector. The RSDs (3.1-8.2% and 4.1-9.0%) of the overall analytical procedure for the determination of total mercury (AMA 254) and methylmercury (HPLC/CV-AFS) were determined for intra-day and inter-day assays, respectively.

Animals↗
PubMed2001

Calcite Crystal Growth Rate Inhibition by Polycarboxylic Acids.

Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. Copyright 2001 Academic Press.

Journal Article↗
PubMed1993

Na(+)-dependent biotin transport into brush-border membrane vesicles from human kidney cortex.

Renal reabsorption of biotin was investigated in human kidney by means of the isolated brush-border membrane vesicle technique. Biotin uptake into the vesicles was sodium-dependent producing a typical overshoot when incubated under sodium-gradient conditions (external concentration greater than internal). This effect was not observed in the presence of gradients of KCl, LiCl or choline-chloride, nor in the absence of any salt. Using the K+/valinomycin voltage-clamp method biotin uptake remained uninfluenced, i.e. was electroneutral, whereas glucose uptake (which is known to be electrogenic in kidney of other species) was greatly increased. When biotin transport was investigated as a function of external sodium concentration a stoichiometic coupling factor of 1 for the Na(+)-biotin- cotransport was determined. Increasing the biotin concentration in the incubation medium up to 200 mumol/l led to saturation with the kinetic parameters of 31 mumol/l for the apparent Michaelis constant and 82 nmol g protein-1 30 s-1 for the maximal transport rate. Uptake was not saturable in the concentration range of 0.001-1 mumol/l. Inhibition of the biotin uptake (25 mumol/l) was observed in the presence of 250 mumol/l dethiobiotin, bisnorbiotin, thioctic acid, and probenecid, whereas biocytin, propionic acid, lactic acid, succinic acid, citric acid, ascorbic acid, primidone and carbamazepine had no effect. We conclude that renal biotin reabsorption in human kidney is specifically sodium-dependent, saturable and electroneutral. It therefore fulfills the requirements for a secondary active carrier-mediated transport system. The results suggest that biocytin is not an inhibitor of renal biotin reabsorption.

Biomarkers↗
PubMed1996

[Characterization of low molecular weight zinc species in normal commercial vegetable foodstuffs].

In six different ordinary vegetables, namely kohlrabi, Chinese cabbage, chard, leak, spinach and Jerusalem artichoke, zinc was mainly found as low molecular weight species. In the present study, these important zinc compounds are further investigated. The determinations of the metal are performed by ET-AAS. The zinc complexes of all vegetables are anionic at pH 8.0 and show similar elution behaviour in gel permeation and anion exchange chromatography. Consequently, a great resemblance in structure between the low molecular weight zinc species from the different vegetables can be supposed. Exemplary, the zinc complexes of kohlrabi and Chinese cabbage are further examined. In more purified samples of these vegetables compared to zinc neither stoichiometric amounts of free protein amino acids nor nicotianamine, free malic acid, citric acid or phytic acid have been detected. Mainly glutamic acid is found in molar excess to zinc after acid hydrolysis in both cases. The cysteine contents of both zinc-binding fractions are very low. Conclusively, the well-known gamma-glutamylcysteinyl-glycines (phytochelatines) can not be responsible for the bonding of zinc in both ordinary vegetables. We suppose that zinc in kohlrabi and Chinese cabbage is bound to a glutamic acid derivative unknown as yet, possibly a malic acid ester.

Amino Acid Sequence↗
PubMed1996

Biochemical relationship between urine composition and urinary stone formation in stone forming patients.

The precise relationship between urine composition and stone formation has not yet been completely understood. The object of this work is to study some constituents of the urine in stone formers and normal subjects in a trial to correlate stone formation with urine composition. Urinary levels of oxalic acid, uric acid and phosphate were elevated in oxalate, urate and phosphate stone formers, respectively, while in the urine of mixed stone formers both oxalic and uric acids were increased. Urinary levels of ascorbic acid, citric acid and mucopolysaccharides in all groups of patients were significantly higher than the corresponding control levels. Although oxalic acid, uric acid and phosphate concentrations were high in their respective stones, the concentrations of these constituents were nearly the same in the mixed stones. Also Ca2+ concentration was higher in stones of oxalate and mixed stone formers than in stones of urate and phosphate formers. Exceptionally, magnesium was high in stones of phosphate stone formers. It is recommended that urinary contents of oxalate, urate and phosphate have to be minimized to overcome stone recurrence.

Adult↗
PubMed2001

Separation of vanadium, niobium and tantalum as ternary mixed-ligand complexes by capillary electrophoresis using chelation with 4-(2-pyridylazo)resorcinol and tartaric acid.

Vanadium(V), niobium(V) and tantalum(V) were separated as ternary mixed-ligand complexes by capillary electrophoresis using 4-(2-pyridylazo)resorcinol (PAR) as the color chelating reagent. Four carboxylic acids such as tartaric acid (Tart), oxalic acid, citric acid and acetic acid were investigated as the additional ligand. The first was chosen as the best. Other parameters such as the concentration ratio of Tart to PAR, buffer concentration, injection time and applied voltage were also optimized. Under the optimized conditions, a complete separation of the three metal complexes was accomplished within 10 min. A linear calibration curve in the range of two orders of magnitude was obtained.

Journal Article↗
PubMed2005

Suitability of a malachite green procedure to detect minimal amounts of phosphate dissolved in acidic solutions.

The study describes the suitability of a colorimetric method (malachite green procedure) for detection of minimal amounts of phosphate (7.3-29.1 micromol/L) in different acidic solutions (hydrochloric acid, oxalic acid, maleic acid, perchloric acid, tartaric acid, citric acid, lactic acid and acetic acid) adjusted to pH 2.0. A mixture of the respective phosphate 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 applied method is a reliable and suitable tool to detect and quantify minimal phosphate contents in small samples of acidic solutions that have the potential to cause erosive dental lesions.

Acids↗
PubMed1991

Preference of Old World monkeys for amino acids and other gustatory stimuli: the influence of monosodium glutamate.

Monosodium glutamate (MSG) is widely considered to enhance the flavor of beef, chicken, fish, and vegetables. This effect may be due to the interaction of glutamate with free amino acids or other basic taste stimuli present in these foods. A single-bottle test was used in order to test the preference of Old World monkeys for an extended array of gustatory stimuli individually and in combination with MSG. Six male cynomolgus monkeys, maintained on an 18-h water deprivation schedule, were given 30 min access daily to a sapid stimulus or distilled water. The following stimuli (selected on the basis of prior experimentation) were tested alone and in combination with 0.03 M MSG: sucrose, fructose, glucose, maltose, polycose, sodium saccharin, glycine, sodium chloride, hydrochloric acid, tartaric acid, malic acid, citric acid, quinine hydrochloride, urea, and beef broth. The L-isomers of the following free amino acids also were tested: alanine, histidine, phenylalanine, proline, serine, valine. The addition of MSG to the stimuli listed above had no significant effect upon the monkeys' preference or aversion thresholds. Most suprathreshold stimuli that the monkeys neither preferred nor avoided were unaffected by the addition of MSG. The monkeys' preference for sugars was adversely affected in mixtures containing MSG, but other stimuli that humans report to be sweet tasting (alanine, glycine, polycose) were unaffected. The data from the present experiment demonstrate that MSG was capable of altering the monkeys' preference for some but not all of the gustatory stimuli tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗