Showing papers by "University of Extremadura published in 1984"
TL;DR: This is the first case of a new variant of hyperphenylalaninemia in which the formation of dihydroneopterin triphosphate and its pterin metabolites in liver is markedly diminished, and it is concluded that the molybdenum cofactor of these enzymes may not be derived from dihydroneship in man.
Abstract: A 4-year-old patient is described with hyperphenylalaninemia, severe retardation in development, severe muscular hypotonia of the trunk and hypertonia of the extremities, convulsions, and frequent episodes of hyperthermia without infections. Urinary excretion of neopterin, biopterin, pterin, isoxanthopterin, dopamine, and serotonin was very low, although the relative proportions of pterins were normal. In lumbar cerebrospinal fluid, homovanillic acid, 5-hydroxy-indoleacetic acid, neopterin and biopterin were low. Oral administration ofL-erythro tetrahydrobiopterin normalized the elevated serum phenylalanine within 4 h, serum tyrosine was increased briefly and serum alanine and glutamic acid for a longer time. Urinary dopamine and serotonin excretion were also increased. Administration of an equivalent dose ofd-erythro tetrahydroneopterin was ineffective and demonstrated that this compound is not a cofactor in vivo and cannot be transformed into an active cofactor. GTP cyclohydrolase I activity was not detectable in liver biopsies from the patient. The presence of an endogenous inhibitor in the patient's liver was excluded. This is the first case of a new variant of hyperphenylalaninemia in which the formation of dihydroneopterin triphosphate and its pterin metabolites in liver is markedly diminished. Normal activities of xanthine oxidase and sulfite oxidase were apparent since uric acid levels were normal and no increase in hypoxanthine, xanthine, andS-sulfocysteine concentrations could be observed in urine. It is concluded that the molybdenum cofactor of these enzymes may not be derived from dihydroneopterin triphosphate in man. Also, since no gross abnormalities in the patient's immune system could be found, it seems unlikely that dihydroneopterin triphosphate metabolites, such as neopterin, participate actively in immunological processes, as postulated by others. See Note added in proof.
156 citations
TL;DR: The enzyme was protected against redox inactivation by low concentrations of GSSG, ferricyanide, GSH, or dithiothreitol, and high concentrations of NAD(P)+; oxidized glutathione effectively protected the enzyme at concentrations even lower than GSH.
130 citations
58 citations
TL;DR: The glutathione reductase from Escherichia coli strain S33 was purified to homogeneity by a simple and fast procedure consisting of two affinity chromatography steps, and the sensitivity towards such mercurial was greatly enhanced after reduction of the enzyme by NADPH.
Abstract: The glutathione reductase from Escherichia coli strain S33 was purified to homogeneity by a simple and fast procedure consisting of two affinity chromatography steps After 40-80% ammonium sulfate fractionation, the enzyme was adsorbed to an N6-2'5'-ADP-Sepharose affinity column from which it was specifically eluted by a 0-10 mM NADP+ linear gradient The enzyme was finally purified to homogeneity after a second affinity chromatography step in a C8-ATPR-Sepharose column, from which it was eluted by means of the same NADP+ gradient Starting from 182 g of E coli cells, 69 mg of pure enzyme was obtained after a 2632-fold purification, with a total yield of 63% The pure enzyme showed a specific activity of 361 U/mg, and its absorption spectrum was characteristic of a flavoprotein, with an A272/A450 of 784 The enzyme was a dimer with a molecular weight 109 000 and 40 A hydrodynamic radius The optimum pH were 75 and 45 with NADPH and NADH, respectively, as reductants Apparent K'm values of 16, 377, and 66 microM were determined at pH 75 for NADPH, NADH, and GSSG, respectively Upon storage the enzyme was stable at pH values ranging from 75 to 95, being additionally stabilized by FAD, NADP+, dithiothreitol, or glycerol The pure enzyme was quite heat stable, denaturing significantly only after 10 min at 70 degrees C A marked activity loss was observed however, even at 0 degrees C, in the presence of 20 microM NADPH The enzyme was inactivated by low concentrations of para-hydroximercuribenzoate; the sensitivity towards such mercurial was greatly enhanced after reduction of the enzyme by NADPH
33 citations
TL;DR: Rat brain P1,P3-bis(5'-adenosyl)-triphosphate adenylohydrolase (dinucleosidetriphosphatase, EC 3.6.1.29) was purified 1000-fold and the optimum pH value was about 7.5.
25 citations
TL;DR: Diadenosine tetraphosphate, Ap4A, doubled the activity of AMP deaminase from rat muscle, with an activation constant of 0.005 mM, in the presence of0.05 mM AMP.
21 citations
TL;DR: It seems clear that the walls of yeast cells must be structurally and enzymatically a complex organelle, increased by the fact that different proteins with important roles in the cell economy as well as survival products are localized on the wall or in the periplasmic space.
Abstract: Yeast cells are covered by a rigid structure that protects the protoplast from osmotic changes and gives the characteristic shape to the cell. Studies on the composition of the wall of several species of yeast and other fungi have shown that they contain mainly polysaccharides with minor amounts of other materials. A completely rigid and continuous wall, nevertheless, would render growth impossible because cell extension would be restricted, so that an equilibrium must exist between softening (partial degradation) of wall and incorporation of new material into free ends of the polymers. From these considerations, it seems clear that the walls must be structurally and enzymatically a complex organelle. This complexity is increased by the fact that different proteins with important roles in the cell economy (e.g., invertase) and morphogenesis (β-glucanases) as well as survival products (e.g., killer, sexual factor) are localized on the wall or in the periplasmic space.
21 citations
01 Jan 1984
TL;DR: The physiological and enzymatic properties of these L-arabinose non-utilizing mutants suggest that L-Arabinose resistance is due to forward mutations in at least 3 other genes, araA, aRAB and araC, blocking steps prior to L-ribulose 5-phosphate accumulation.
Abstract: The evidence that most animal carcinogens are also mutagens,(20,24) strongly suggesting that DNA is the ultimate target of carcinogenic activation, has been an important support of the somatic mutation theory of the etiology of cancer. The recent demonstration that a single point mutation, a GC to TA transversion, leads to the activation of a human oncogene(30,36) is in agreement with this suggestion.
20 citations
TL;DR: In this paper, the Wigner one body distribution function of atomic nuclei is studied in the mean field approximation and several approximations to this method based on the density matrix expansion (DME) are also studied and reformulated.
19 citations
TL;DR: Yeast β(1–3) glucan synthetase is stimulated and stabilized by EDTA, and the role of all these agents on the activity and stability of the enzyme is interpreted in a unified scheme.
Abstract: Yeast β(1–3) glucan synthetase is stimulated and stabilized by EDTA. Sucrose protects the enzyme from selfinactivaton. Preincubation of cell free extracts at low sucrose concentrations indicates a slow transition of the enzyme towards dissociation. Transition kinetics at 30° C and 0° C in the presence and in the absence of sucrose are interpreted assuming that a subunit is thermolabile in the free state and that sucrose increases its stability. Magnesium is deletereous for glucan synthetase in cell-free extracts. Chaotropic agents inactivate glucan synthetase according to their capacity to solubilize and depolymerize biological compounds. Fluoride plays a special role in the activation of glucan synthetase. Its action appears to be dependent on the presence of GTP (or other nucleotides). The role of all these agents on the activity and stability of the enzyme is interpreted in a unified scheme.
16 citations
TL;DR: In this article, the aminonitrile synthesis applied to d -mannose gave, in good yield, a mixture of the two epimeric heptosamines 2-deoxy-2-(ethylamino)- d -glycero-α- d -galacto-heptopyranose and 2-Deoxy-1-aryl(glycofurano)imidazolidine-2-thiones, whose structures were assigned from the 1H-n.m.
TL;DR: It is proposed that the mechanism of production of JGB-induced syndactyly might be due to an alteration of the normal epithelial-mesenchymal interactions rather than to a direct inhibitory effect of the JGB on the dying program.
Abstract: In an attempt to clarify the mechanism of production of the syndactyly induced by Janus Green B (JGB) we have studied the morphology and structural modifications of the chick embryo leg bud after JGB administration by means of (1) neutral red vital staining, (2) whole-mount cartilage staining and (3) light microscopy and transmission and scanning electron microscopy. The results show that the well-known inhibition of interdigital cell death is accompanied by a precocious alteration of the epithelial tissue and especially of the epithelial-mesenchymal interface. 24 h after JGB administration the cells of the AER reduce the number of junctions and the basal ectodermal cells are detached into the mesenchymal tissue in zones in which the basal lamina undergoes disruption. In addition the interdigital mesenchymal cells diverted from the dying program are able to undergo a rapid differentiation into cartilage. It is proposed that the mechanism of production of JGB-induced syndactyly might be due to an alteration of the normal epithelial—mesenchymal interactions rather than to a direct inhibitory effect of the JGB on the dying program.
TL;DR: The synthesis and analytical properties of dimedone bisguanylhydrazone (DIBG) are described for the first time and the kinetic parameters of the reaction have been determined.
TL;DR: In this article, the new amino sugars 2-deoxy-2-(ethylamino)-α- l -glucopyranose, 2-deco-propylamino-α-l -glucofurano, and 2deco-(deco)-2deco]-α(or β)- l -mannopyransose have been prepared from l -arabinose by the aminonitrile synthesis.
TL;DR: In this paper, the reaction of 1-aryl-(1,2-dideoxy-d - glycero -β- l - gluco -heptofurano)[1, 2-d ]imidazolidine-2-thiones with benzyl chloride and an equivalent amount of sodium hydrogen carbonate yields 1- Daryl-2-(benzylthio)-(1 2 dideoxy -d -glycero)-β-l -gluco-hexagon-1-yl)IMIDazoles.
TL;DR: In this paper, the properties and analytical possibilities of salicylaldehyde guanylhydrazone as spectrophotometric reagent have been examined and a new method for the determination of iron has been developed.
TL;DR: In this article, the fluorescent chelate formed between 1-hydroxy-2-carboxy-anthraquinone and gallium(III) at pH 3.9 has been studied spectrofluorimetrically in an ethanol-water mixture (70/30% V/V).
Abstract: The fluorescent chelate formed between 1-hydroxy-2-carboxy-anthraquinone and gallium(III) at pH 3.9 has been studied spectrofluorimetrically in an ethanol-water mixture (70/30% V/V). A new method for the fluorimetric determination of gallium(III) is described. The fluorescence is monitored at 580 nm (wavelength of excitation 465 nm) and the range of application of the method is between 50 and 500 ng ml−1. The stoichiometry of the complex has been found to be 1∶1.
TL;DR: Acid catalyzed isomerization of 1-aryl-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) yields 1- Daryl-4-(D-galacto-pentitol-1-yl)imidazoles which can be also obtained by reductive desulphuration
Abstract: Acid catalyzed isomerization of 1-aryl-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-2-imidazolines (4) yields 1-aryl-4-(D-galacto-pentitol-1-yl)imidazoles (8) which can be also obtained by reductive desulphuration of 1-aryl-2-benzylthio-4-(D-galacto-pentitol-1-yl)imidazoles (6). Compounds (4) were obtained by desulphuration with Raney nickel from 1-aryl-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-imidazolidine-2-thiones (1) or 1-aryl-2-benzylthio-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-2-imidazolines (2).
TL;DR: The reaction between 1,2,4-trihydroxyanthraquinone-3-carboxylic acid and BrO3− in hydrochloric acid medium has been studied spectrophotometrically as discussed by the authors.
TL;DR: In this article, the fluorescent chelate formed between 1-hydroxy-2-carboxy-anthraquinone and gallium(III) at pH 3.9 has been studied spectrofluorimetrically in an ethanol-water mixture (70/30% V/V).
Abstract: The fluorescent chelate formed between 1-hydroxy-2-carboxy-anthraquinone and gallium(III) at pH 3.9 has been studied spectrofluorimetrically in an ethanol-water mixture (70/30% V/V). A new method for the fluorimetric determination of gallium(III) is described. The fluorescence is monitored at 580 nm (wavelength of excitation 465 nm) and the range of application of the method is between 50 and 500 ng ml−1. The stoichiometry of the complex has been found to be 1∶1.
TL;DR: Dimedone bisthiosemicarbazone monohydrochloride has been examined to evaluate its usefulness as a reagent for rapid and sensitive Spectrophotometric determination of chlorate (0.5-5.0 ppm) by oxidation of the reagent in 70% perchloric acid medium and measurement of the yellow product.
Abstract: Dimedone bisthiosemicarbazone monohydrochloride has been examined to evaluate its usefulness as a reagent for rapid and sensitive Spectrophotometric determination of chlorate (0.5–5.0 ppm) by oxidation of the reagent in 70% perchloric acid medium and measurement of the yellow product. The molar absorptivity at 417 nm is 1.86×104 l·mole−1·cm−1. The relative standard deviation is 1.6% for 2.5 ppm of chlorate.
TL;DR: In this article, the analytical properties of an iron-II-PAG system are described. And the optimal conditions for a spectrophotometric determination of iron are shown. And a polarographic behavior of the PAG system has been attempted.
TL;DR: In this article, the Pseudopurpurin-Pd(II) complex was studied spectrophotometrically in an ethanolic-water medium and the relative error and interferences of the method were investigated.
01 Jan 1984
TL;DR: In this paper, the ATDHF formulations for large amplitude collective nuclear modes are reviewed together with the conditions of validity that establish the range of applicability of the theory to soluble models.
Abstract: ATDHF formulations for large amplitude collective nuclear modes are reviewed together with the conditions of validity that establish the range of applicability of the theory. Application to soluble models is presented to clarify the meaning of different validity conditions and equations of path. Extensions of the standard ATDHF formalism are also discussed.
TL;DR: In this paper, a method for the fluorimetric determination of BrO3, at the nanogram level, based on the oxidation of 1,2,4-tri-hydroxyanthraquinone-3-carboxylic acid in sulfuric acid medium, was described.
Abstract: A method is described for the fluorimetric determination of BrO3, at the nanogram level, based on the oxidation of 1,2,4-tri-hydroxyanthraquinone-3-carboxylic acid in sulfuric acid medium. The fluorescence emission is monitored at 585 nm (wavelength of excitation 521 nm). The method shows a detection limit of 5 ng/ml, being the most sensitive of all the established methods for the determination of this anion by photometry and fluorimetry.
TL;DR: Maximum velocity of nucleoside diphosphate kinase (50 U/g dry cysts) is well in excess over the enzymes which transform diguanosine tetraphosphate into AMP.
Abstract: 1. 1. Nucleoside diphosphate kinase (EC. 2.7.4.6) has been purified 1900-fold with 17% yield from Artemia dormant embryos. 2. 2. The purified enzyme exhibits a ping-pong mechanism of reaction. The calculated Km values for ADP, GTP, ITP, UTP and CTP are 0.04, 0.17, 0.25, 0.27 and 0.62 mM, respectively. 3. 3. The role of this enzyme in the conversion of diguanosine tetraphosphate into ATP is also discussed. Maximum velocity of nucleoside diphosphate kinase (50 U/g dry cysts) is well in excess (around thousand-fold) over the enzymes which transform diguanosine tetraphosphate into AMP.
TL;DR: In this paper, measurements of condensation nuclei (CN) were taken daily at Villanubla, Spain, 845 m above sea level, in the months of March and April, 1980.
TL;DR: In this paper, the following acetylene derivatives have been employed: methyl propiolate, ethyl phenylpropiolate and dimethyl acetylenedicarboxylate (6 ).