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PubMed1975

Studies on the circadian rhythm of phosphoenolpyruvate carboxykinase. III. Circadian rhythm in the kidney.

Phosphoenolypyruvate carboxykinase [EC 4.1.1.21] activity in rat kidney shows a circadian rhythm with the highest activity between 0200 h and 0800 h and the lowest activity between 1400 h and 2000 h. The rhythm was observed in both sexes and throughout the year. Actinomycin D and cycloheximide effectively blocked the circadian increase in enzyme activity. These findings suggest that the circadian increase in phosphoenolypyruvate carboxykinase activity is due to net synthesis of enzyme protein through newly synthesized mRNA. In experiments with kidney cortex slices, gluconeogenesis from the radioactive precursor, [14C]malic acid, was considerably higher at 0200 h than at 1400 h, varying in parallel with the change in the enzyme activity.

Acclimatization↗
PubMedDate not supplied

[Chemical characteristics of "artificial wines" (author's transl)].

A wide investigation has been carried out in order to evidenciate the differences of composition between "artificial wines" and genuine wines. "Artificial wines" have been produced by fermentation of mixtures of different amounts of wine making by-products (less, pomaces and press-wines), water and sucrose. The results showed, in particular, that "artificial wines" have a very low content of both malic acid and proline and a high content of nitrates. Significant differences have been also found in the content of polyphenols, alkaline and alkaline earth metals and citric acid.

Calcium↗
PubMed2004

Use of miniaturised isotachophoresis on a planar polymer chip to analyse transition metal ions in solutions from metal processing plants.

An electrolyte system, using malic acid as a complexing agent, has been developed to allow the determination of transition metal cations using miniaturised isotachophoresis. The method allowed the simultaneous determination of Mn2+, Cr3+, Fe2+, Co2+, Zn2+ and Ni2+ to be made without interference from other common ions. Limits of detection were calculated to be in the range 0.5-1.0mg l(-1) for Mn2+, Cr3+ Co2+ and Zn2+ and 2.0 mg l(-1) for Fe2+ and 4.7 mg l(-1) for Ni2+. The successful analysis of five industrial samples, containing a range of these metal ions, obtained from metal processing plants were achieved in under 13 min. The separations were performed on a poly(methyl methacrylate) chip with integrated platinum wire conductivity detection electrodes.

Electrophoresis↗
PubMed2005

[Study on chemical constituents from Opuntia dillenii].

OBJECTIVE: To study the chemical composition of Opuntia dillenii. METHOD: Many kinds of chromatography methods were used in the isolation procedure, while the structures of isolated compounds were determined on the aids of NMR and MS spectral analysis. RESULT: A new compound, together with five known compounds, was isolated form the 80% ethanolic extract of its stems. CONCLUSION: The new compound was characterized as opuntioside. Four compounds were obtained for the first from the genus Opuntia, and they were daucosterol, p-hydroxybenzoicacid, L-(-)-malic acid, (E)-ferulic acid. Opuntiol was also separated for the first from the plant.

Coumaric Acids↗
PubMedDate not supplied

[The growth-inhibiting activity of mixed complexes of platinum(II) with ammonia and cycloalkylamines].

The effect was studied of mixed cys- and 3-, 4-, 5-, 6-nomial cycloalkylamines or substituted 2-, 3-, 4-methyl- and 4-hydroxycyclohexylamines as well as similar carboxylatocomplexes containing anions of malonic hydroxymalonic, succinic and malic acids on the growth of corn sprout roots. Complexes with non-substituted cycloalkylamines possessed the most pronounced cytostatic activity. Complexes with substituted cyclohexylamines were less active than their non-substituted analogue as well as other complexes with lesser size of cyclic substitute. The cytostatic activity of carboxylatocomplexes, as compared to that of chlorocomplexes, generally manifested itself at ten times higher concentraiton and depended not only on the size of cycloalkylamine but also on the nature of acidoligand.

Amines↗
PubMed1990

[Experimental development of a chitosan-bonded hydroxyapatite bone filling paste].

Chitosan, a naturally occurring high molecule or weight polymer which is stable in vivo like collagen, has proved a useful biomaterial in applications such as suture thread and artificial skin. A hydroxyapatite bone-filling material was developed with chitosan sol as a binder. Measurements were made of the solubility of chitosan, and of the setting time, compressive strength, and pH value of the material. X-ray microanalysis and diffraction analysis of the material were also conducted. Chitosan is freely soluble in malic acid and succinic acid, but insoluble in citric acid and oxalic acid. The setting time of the bone-filling material tended to decrease with increase in the amounts of its CaO and ZnO components. The setting time increased with increasing ratio of sol to other (powdered) ingredients. The pH value decreased with increasing ratios of chitosan sol to the powdered ingredients. High pH values resulted from increases in both CaO and ZnO. The time between the preparation of the chitosan sol and the onset of kneading significantly affected the compressive strength of the material when set. The strength measured roughly 50% more for times between 90 and 150 minutes than for times shorter or longer than that range. Greater compressive strength was generally observed for increases in both CaO and ZnO. The results of the X-ray microanalysis of the hardened paste showed calcium crystals other than hydroxyapatite.

Bone and Bones↗
PubMed1990

[Chemical constituents of the leaves of Crataegus pinnatifida Bge. var. major N. E. Br].

Compounds were isolated from the aqueous extract of the leaves of Crataegus pinnatifida var. major and seven of them were identified as 2-(4-hydroxybenzyl)malic acid, quercetin, hyperin, vitexin, rhamnosylvitexin, diethylamine hydrochloride and sorbitol respectively by UV, IR, NMR, MS, some chemical techniques by comparison with the standard spectra of known compounds.

Diethylamines↗
PubMed1989

[The effect of composition and ionic strength of external solution on the aspartate-ammonia lyase and fumarate hydratase activity in Escherichia coli cells].

It was found that the nonspecific effect of ionic strength of the external solution on the enzymatic activity of E. coli cells consists in rapid changes in the permeability of cell membranes interacting with the substrate. This effect depends on the initial substrate concentration, i.e., ionic strength of the external solution, and is maintained for some time as the substrate concentration decreases. Chloramphenicol, a protein synthesis inhibitor, and sodium azide, a respiration inhibitor (300 micrograms/ml and 200 microM, respectively) do not change the enzymatic activity of E. coli cells during the synthesis of L-aspartic and L-malic acids from fumaric acid. The kinetic equations of L-aspartate and L-malate synthesis are described by equations of zero and intermediate (between zero and first) order, respectively.

Ammonia-Lyases↗
PubMedDate not supplied

[Effect of aminoxidase activity regulators on the humoral immune response and proliferation of lymphoid and nonlymphoid cells].

DL-malic acid dibenzylhydrazide (I) and dihydrazide (II), inhibitors of aminoxidases, have been shown to inhibit immune reactions when administered at the phase of initiation but to stimulate the immune response and proliferation of lymphoid and nonlymphoid cells if given on the 2nd and 3rd day following immunization when the immune reaction is in progress. The intensity of local allergic reaction during passive skin anaphylaxis is reduced by I and enhanced by II if the compounds are administered 16 hrs prior to antigen challenge.

Anaphylaxis↗
PubMed1978

Enzymatic hydrolysis of soy protein for nutritional fortification of low pH food.

Enzymatic hydrolysis of proteins is an attractive means of obtaining the changes in the functional properties often necessary for incorporating the protein in low pH food, e.g. soft drinks. The main problem associated with protein hydrolysis is the welldel-known formation of bitter-tasting peptides. The bitterness seems to be related to a too high degree of hydrolysis (DH). DH is defined as the percentage of cleaved peptide bonds and serves as the controlling parameter for the hydrolysis process. The choice of hydrolysis parameters is briefly discussed in relation to studies on the hydrolysis kinetics which in many respects can be described by classical enzyme kinetics. Several pilot plant productions of isoelectric soluble soy protein hydrolyzates have been carried out using soy isolate or soy concentrate as the raw material. The preferred enzyme for this type of hydrolysis is Alcalase 0.6 L, a food-grade liquid preparation of subtilism Carlsberg. The chosen hydrolysis parameters are : Substrate conc. : 8 per cent protein (N x 6.25). Enzyme-substrate ratio : 2 per cent. pH : 8.0. Temperature : 50 degrees C. The optimal DH value with regard to taste seems to be 10 per cent, corresponding to about 2 hours' hydrolysis time. The hydrolysis is terminated by the addition of citric or malic acids until pH reaches a value of 4.2. Separation of the supernatant from the unconverted protein is carried out in a continuous, solids-ejecting centrifuge. Preliminary rat trials show a satisfactory nutritional quality of the hydrolyzates. Possible end-uses for soy protein hydrolyzates are briefly discussed.

Food, Fortified↗
PubMed1984

[Isolation of atmospheric-nitrogen-fixing spirilla from the waters of the Paraná delta and other rivers].

Seventeen strains of Spirillum-like organisms (2) were isolated from the Parana Delta and other rivers (Table 1), using the following medium: 0.5% malic acid; 0.4% KOH; 0.5% K2HPO4; 0.005% yeast extract; pH was adjusted to 7 with KOH and 0.15% agar. The organisms produced a white, dense and sub-superficial pellicle in this medium, and streaking them on plates, single colonies could be isolated. They were easily recognized thanks to the Congo red added to the medium, because the bacteria, as it happens with Azospirillum species (6) (Spirillum lipoferum) (1), concentrated the strain. Using a colorimetric determination for ethylene (5), nitrogenase activity was detected in all the strains and in the NFb and potato-agar media the colonies were typical of Azospirillum (3). In PSS-semisolid and solid media, the growth was similar to that observed with Azospirillum strains. The isolated organisms developed in this medium better at 28 degrees C than at 37 degrees C, and the same was observed with 8 strains of Azospirillum isolated from plan roots of different species obtained from temperate regions. Some physiological tests were performed to identify the isolated organisms (Table 2). None of the isolated strains could be classified as a known species of Spirillum (4, 7), according to these tests. As thirteen strains showed properties in common with the terrestrial species A. brasilense and the others with A. lipoferum (8) they were tentatively identified as members of these species. Further studies are needed to ensure the classification of these strains and to determine the importance of these bacteria in the nitrogen balance of the waters from where they were isolated.

Argentina↗
PubMed1982

Detection of adulteration in blackberry juice concentrates and wines.

Adulteration of blackberry juice concentrates and wines with juice of sorbitol-containing fruits was detected by determining carbohydrates by high performance liquid chromatography, gas-liquid chromatography, and thin layer chromatography. Sorbitol is not fermented by yeast and can be detected in wines made from blackberry juice concentrates that contain sorbitol. High levels of sorbitol and quinic and malic acids suggest that an imported blackberry concentrate may have been adulterated with plum. Degradation of anthocyanin pigments during processing and storage limits the utility of pigment analyses in detecting adulteration.

Anthocyanins↗
PubMed1980

Reversal of digoxin induced cardiac arrhythmias by nickel chloride.

The effect of NiCl2 on digoxin induced cardiac arrhythmias were studied in anesthetized dogs and in isolated perfused hearts of rabbits, guinea pigs and rats. The results indicate that NiCl2 can effectively antagonize the digoxin induced cardiac arrhythmias in both intact as well as in isolated hearts. Sinus rhythm was restored and the cardiovascular status of the animal (which was digitoxic) eventually restored to normal. When not treated with NiCl2 the cardiovascular status of the dogs was progressively worsened leading to death. NiCl2 alone did not have any marked effect in normal hearts. It is likely that Ni2+ might be competing with Ca2+ at the cell membrane sites thereby antagonizing the toxic effects of digoxin. It is also possible that an increase in malic acid and oxaloacetic acid activity induced by NiCl2 may play a role in reversing the toxicity of digoxin.

Animals↗
PubMed1978

[Enzymatic methods in the analysis of musts and wines].

The enzymatic methods are based on the property of the enzymes to catalyse specifically and reversibly the conversion of certain metabolites. These methods, developed thanks to the industrial preparation of enzymes, can be applied with no major modification to the analysis of drinks. About 15 constituants of musts and wines can now be determined by these methods. If their cost price was not relatively high, their specificity, sensitivity and rapidity would enable them to compete with the most precise of chemical methods. This is why they are only used in analytic oenology when chemical analysis is most specific enough or too laborious. Enzymatic measurement allows one by its specificity to determine the amount of residual sugar that is fermentable in a dry wine and by its sensitivity to verifie the total disappearance of the malic acid of the wine. Its rapidity must make it preferable to the long and not very specific chemical measurement, especially concerning the determination of citric acid. But glycerol, ethanol and acetic acid can be measured by chemical or chromatographical means with sufficient precision and for a more modest price. In oenology the methods are essentially used for research. They have permitted the study of the combinations of sulphur anhydride in wines (measurement of cetonic acids). The determination of the isomeric nature of the lactic acid produced from sugars by lactic bacteria is based on their application; this determination is a criterium for the identification and classification of these microorganisms. The measurement of the lactic acid during vinification allows the early disclosure of the first effects of a bacterial development; inversely it permits the invalidation of the existence of a lactic sourness, which a high volatile acidity might point to. Lastly, the enzymatic measurement of gluconic acid allows the health of the crop to be controlled.

Anhydrides↗
PubMed1976

[Comparative study of the effect of inhibitors of monoamine oxidase and ftorafur on the growth of de-differentiated astrocytoma].

To evaluate the possible antitumour effect of intensified deposition of serotonin in the region of localization of the tumour caused by a pharmacological preparation studies of the effect of inhibitors of monoamine oxidase transamine and N2N2-dibenzylhydrazide of DL-malic acid on rat's cerebellum tumour de-differentiated by astrocytoma (strain No 101/12) were carried out. The effect of inhibitors of monoamine oxidase was compared with that of antiblastic preparation of phthorafur. Differences in the mechanisms of action of pharmacological agents referred to above are shown. It was established that inhibitors of monoamine oxidase administered against the background of the developing tumour caused a considerable reduction in its weight and prononced dystrophic and necrotic changes.

Animals↗
PubMedDate not supplied

[Immobilization of Bacillus subtilis proteases on a styrol copolymer with maleic anhydride with covalent and coordination bonds].

Insoluble enzymes have been obtained through an interaction of the complex preparation of proteases, protosubtilin G15x, with the sterol and maleic anhydride copolymer in aprotic dipolar solvents and as a result of formation of mixed enzyme-polymer complexes of protosubtilin G15x and the sterol and malic acid copolymer in aqueous solution in the presence of metal ions. The effect of metal ions on the yield and activity of the resultant immobilized preparation has been studied.

Bacillus subtilis↗
PubMed2006

Time course of the evolution of malic and lactic acids in the alcoholic and malolactic fermentation of grape must by quantitative 1H NMR (qHNMR) spectroscopy.

Quantitative NMR can be used to monitor several processes that take place in the transformation of the must of wine grapes. The study described here focused attention on monitoring of the malic and lactic acid levels during the alcoholic and malolactic fermentation processes. The method allows the simultaneous quantification of both acids through a range of 1-3.2 mmol/L. The effectiveness of each process was assessed and compared by carrying out precise analyses using enzymatic methods.

Fermentation↗
PubMed1998

Isolation and characterization of Kluyveromyces marxianus mutants deficient in malate transport.

In malic acid-grown cells of the strains ATCC 10022 and KMS3 of Kluyveromyces marxianus the transport of malic acid occurred by a malate-proton symport, which accepted L-malic, D-malic, succinic and fumaric acids, but not tartaric, malonic or maleic acids. The system was inducible and subjected to glucose repression. Mutants of the strain KMS3, unable to grow in a medium with malic acid, were isolated and checked for their capacity to utilize several carbon sources and to transport dicarboxylic acids by the malate-proton symport. Two distinct clones affected on malate transport were obtained. Both were able to grow on a medium with glycerol or ethanol but not with DL-malic, succinic, oxoglutaric and oxaloacetic acids as the sole carbon and energy sources. However, while one of the mutants (Mal7) displayed activity levels for the enzymes malate dehydrogenase, isocitrate lyase, and phosphoenolpyruvate carboxykinase similar to those of the wild strain, in the other mutant type (Mal6) the activities for the same enzymes were significantly reduced. Plasma membranes from derepressed cells of the wild strain and of the mutants Mal6 and Mal7 were isolated and the protein analysed by SDS-PAGE. The electrophoretic patterns of these preparations differed in a polypeptide with an apparent molecular mass of about 28 kDa, which was absent only in the mutant Mal7. The results indicated that Mal7 can be affected in a gene that encodes a malate carrier in K. marxianus.

Biological Transport↗