Showing papers by "University of Seville published in 1980"
TL;DR: Ammonium assimilation, rather than ammonium itself, seems to regulate nitrate utilization in A. nidulans, and its prevention by MSX and azaserine was demonstrated in the filamentous cyanobacteria Anabaena and Nostoc.
Abstract: Ammonium at low concentrations caused a rapid and effective inhibition of nitrate utilization in the light by the cyanobacterium Anacystis nidulans without affecting the cellular level of nitrate reductase activity. The inhibition was reversible, and the ability of the cells to utilize nitrate was restored immediately after ammonium had been exhausted. The inhibitory effect was dependent on consumption by the cells of the added ammonium which was rapidly incorporated into amino acids. In the presence of L-methionine-d,l-sulfoximine (MSX) or azaserine, inhibitors of the glutamine synthetase-glutamate synthase pathway, ammonium did not exhibit any inhibitory effect on nitrate utilization. Ammonium assimilation, rather than ammonium itself, seems to regulate nitrate utilization in A. nidulans. Short-term inhibition by ammonium of nitrate utilization and its prevention by MSX were also demonstrated in the filamentous cyanobacteria Anabaena and Nostoc.
123 citations
TL;DR: In this article, the design of current conveyors using a minimum number of operational amplifiers was reported. But their performance was not compared with other realisations, and they used different configurations of the amplifiers.
Abstract: Some circuits for the design of current conveyors are reported. The new configurations use a minimum number of operational amplifiers. Experimental data on their performance is compared with other realisations.
57 citations
TL;DR: The mutations which block lycopene cyclization and those which stop substrate transfer along the carotene pathway are very closely linked in Phycomyces as mentioned in this paper, and the frequencies of different kinds of mutants after treatments with the mutagens N-methyl-N′-Nnitro-N-nitrosoguanidine and ICR-170, their reversion patterns, and recombination analyses indicate that the mutations are governed by separate segments of a single bifunctional gene.
Abstract: The mutations which block lycopene cyclization and those which stop substrate transfer along the carotene pathway are very closely linked in Phycomyces. Simultaneous blocking of both processes commonly results from single exposures to mutagens; and both blockings may be simultaneously removed after a second exposure. The frequencies of different kinds of mutants after treatments with the mutagens N-methyl-N′-nitro-N-nitrosoguanidine and ICR-170, their reversion patterns, and recombination analyses indicate that lycopene cyclization and substrate transfer are governed by separate segments of a single bifunctional gene.
46 citations
TL;DR: The results indicate that photocarotenogenesis depends on a single sensory pathway which shares its earlier steps (governed by genesmadA andmadB) with the sensory pathway for phototropism and includes at least one specific step not known to be involved in other responses.
Abstract: The effect of light on carotene accumulation was studied by analyzing the β-carotene content of 4-α-old mycelia continuously exposed to illumination of different intensities. The wild-type, mutants defective in phototropism, mutants defective in carotene regulation, and newpic mutants specifically defective for photocarotenogenesis were examined. The results indicate that photocarotenogenesis depends on a single sensory pathway which shares its earlier steps (governed by genesmadA andmadB) with the sensory pathway for phototropism. It shares its later steps (probably governed by genescarA andpicB) with one of the pathways for carotene regulation, and includes at least one specific step (governed by genepicA) not known to be involved in other responses.
45 citations
TL;DR: In this paper, the activation energy (E/sub a/) and the log of the preexponential factor (log A) of 4f oxides were investigated for the catalytic deformation of 2-propanol, 1-butanol, and 2butanol.
35 citations
TL;DR: In this article, a detailed quantitative survey of the optical-model ambiguity in particular cases shows a very wide range of equally good choices in the Woods-Saxon parameters and even some degree of indefiniteness in the magnitudes usually considered to be well-defined, like the strong absorption radius.
34 citations
01 Jan 1980
TL;DR: The stimulation of protein and amino acid synthesis by blue light requires higher rates of ammonium production, and as the first steps in the utilization of nitrate, its uptake and/or its subsequent reduction to ammonia could be key reactions to be regulated by monochromatic light.
Abstract: Regulatory effects of monochromatic light in the overall processes of photosynthesis and respiration are widely known in higher plants and algae. Blue light plays an important role by changing the pattern of photosynthetic products and by stimulating mitochondrial respiration even under conditions of active photosynthesis (Voskresenskaya 1972). This blue light effect can be due to an enhancement in the flow of electrons from the noncyclic electron transport chain toward oxygen, promoting an increase in pseudocyclicphotophosphorylation, or to a stimulation of NAD(P)H consumption leading to a higher level in C3 compounds, in glycolate and in amino acids, together with a higher level of ATP (Steup and Pirson 1974; Eichhorn and Augsten 1977). Besides, it certainly also consists in a direct interference of blue light with the activities of various enzymes involved in carbon and amino acid metabolism (Ries and Gauss 1977; Miyachi et al. 1978). The stimulation of protein and amino acid synthesis by blue light requires higher rates of ammonium production, as suggested or already found by several authors (Voskresenskaya and Grishina 1962). As the first steps in the utilization of nitrate, its uptake and/or its subsequent reduction to ammonia could be key reactions to be regulated by monochromatic light.
34 citations
TL;DR: In this article, a thermopile conduction calorimeter for the determination of the thermal properties of single crystals with applied electric field is described, and the specific heat of triglycine sulfate is measured near the critical point and at several applied electric fields (0, 160, 300, 500, and 800 V/cm).
Abstract: A thermopile conduction calorimeter for the determination of the thermal properties of single crystals with applied electric field is described. The specific heat of triglycine sulfate is measured near the critical point and at several applied electric fields (0, 160, 300, 500, and 800 V/cm). An echelon-type function is used to obtain the best fitting curve and for E ≧ 300 V/cm the results confirm the predictions deduced from the thermodynamic theory of ferroelectricity.
On decrit un calorimetre a thermopiles pour l'etude des proprietes thermiques des monocristaux etant soumis a differents champs electriques. On mesure la chaleur specifique du sulfate de glycocolle pres du point critique et a differents champs electriques (0, 160, 300, 500 et 800 V/cm). On ajuste une fonction type echelon aux points experimentaux et on trouve que pour E ≧ 300 V/cm les resultats sont d'accord avec les predictions de la theorie thermodynamique de la ferroelectricite.
31 citations
TL;DR: The decrease of the levels of RNA polymerases I and III in starved nauplii could be the molecular mechanism responsible for the drop in RNA synthesis observed during the larval development in cultures of nauPLii in the absence of an external source of food.
Abstract: Artemia nauplii contain three forms of RNA polymerase. RNA polymerases I and II have the common pattern of α-amanitin sensitivity of the eukaryotic enzymes, but RNA polymerase III is insensitive to high concentrations of the drug. The determination of the levels of the RNA polymerases during early larval development is affected by the increase of proteolytic activity during this stage, which produces the inactivation of RNA polymerases I and III in vitro. Protease B has been identified to be the enzyme responsible for the inactivation of RNA polymerase I. The culture conditions of Artemia larvae also affect the levels of the RNA polymerases. The maintenance of the larvae in the absence of food produces a decrease of RNA polymerases I and III several hours after hatching. In contrast, fed nauplii contain almost stable levels of the three forms of RNA polymerases during the studied period of larval development. The decrease of the levels of RNA polymerases I and III in starved nauplii could be the molecular mechanism responsible for the drop in RNA synthesis observed during the larval development in cultures of nauplii in the absence of an external source of food.
27 citations
01 Feb 1980
TL;DR: In this article, constant strain rate compressions along with Vickers indentations have been performed on { 100, { 110, and {111 } faces around the Neel temperature, i.e. between 0 °C and 40 °C.
Abstract: Constant strain rate compressions along have been performed on CoO single crystals (e ∼ 6 x 10-5 s-1). Yield stresses and work hardening rates have been measured between 77 K and 1 400 K; CoO is very strong when compared to similar compounds. Vickers indentations have been performed on { 100 }, { 110 } and {111 } faces around the Neel temperature, i.e. between 0 °C and 40 °C. Hardness values are low if compared to constant strain rate deformation characteristics; they show a minor anomaly at the Neel temperature.
26 citations
TL;DR: In this article, a continuation of the study and applications of biacetyl bis(4-phenyl-3-thiosemicarbazone) (BBPT) and bipyridylglyoxal bis (4phenyl 3-thIosemic) (BGPT) is presented.
TL;DR: Results suggest that blocking of lycopene cyclisation by CPTA releases a negative control by β-carotene and that gene carA is involved in this regulatory mechanism.
TL;DR: In this paper, the same amount of CO is adsorbed on both samples, with a single band at 2070 cm-1 in the Rh SiO 2 sample that shifts to 2020 cm- 1 in Rh TiO 2, thus indicating a higher electron donor capacity of this sample.
TL;DR: In this article, the properties of 3-hydroxypyridine-2-aldehyde 2-pyridylhydrazone as a spectrophotometric and fluorimetric reagent are described.
TL;DR: In this paper, the polyhydroxyalkyl chain of 6,6-dimethyl-2-(d -gluco -pentitol-l-yl)-4,5,6,7-tetrahydroindol-4-one and 2-( d - galacto-pentitol l-yl)4, 5, 6,7, 7, 7 -tetrahedron 4-one were obtained by acid-catalysed dehydration.
TL;DR: The energy dependence of the fusion cross section and its maximum value are well predicted, for a wide range of nuclei and energies, by introducing information on the nuclear matter density distribution into a simple formula.
TL;DR: In this article, the authors show that the apparent contradiction between the statement of Dharwadkar et al. and their conclusion is due to the different ways of defining the constant rate.
TL;DR: The spectral properties of biacetyl bis(2-pyridyl)hydrazone (BBPH) and other BMPH derivatives have been studied by spectrophotometry.
01 Aug 1980
TL;DR: The method is used to compute the upper and lower bounds parameters of microstrip on sapphire substrate and general expressions are obtained for the permittivity and the thickness of an equivalent isotropic substrate.
Abstract: An analytical approach is used to find the upper bounds of microstrip line capacitance which arbitrary anisotropic substrate. General expressions are obtained for the permittivity and the thickness of an equivalent isotropic substrate. The method is used to compute the upper and lower bounds parameters of microstrip on sapphire substrate.
TL;DR: Lineweaver-Burk plots of the initial reaction velocities at varying concentrations of substrates have been performed, and product inhibition patterns show an iso ping pong bi bi steady state kinetic mechanism, with isomeration of the enzymatic form which binds NADH, for the NADH-nitrate reductase activity.
TL;DR: The existence of the inm-1 mutation proves that nitrosoguanidine mutagenesis is not merely the result of reactions between the chemical and DNA, but requires specific cellular function(s), and underscores the peculiarity of nitrosOGuanidine as a mutagen.
Abstract: A newly-isolated Escherichia coli mutant suffers only about 10% as many mutations as normal strains on exposure to nitrosoguanidine1. The responsible mutation, inm-1, maps at approximately minute 79 in the current E. coli genetic map. The mutant is normal for overall growth, nitrosoguanidine lethality, spontaneous mutagenesis, ultraviolet light lethality and mutagenesis, ethyl methanesulfonate lethality and mutagenesis, and the adaptive repair induced by alkylating agents. The existence of this mutation proves that nitrosoguanidine mutagenesis is not merely the result of reactions between the chemical and DNA, but requires specific cellular function(s), and underscores the peculiarity of nitrosoguanidine as a mutagen.
TL;DR: In this paper, the reaction between 2-amino-2-deoxyaldoses and β-dicarbonyl compounds yields polyhydroxyalkylpyrroles.
TL;DR: In this paper, NiO single crystals have been creeped in compression between 1 070 °C and 1 550 °C for stresses in the range 10 MPa-150 MPa.
Abstract: NiO single crystals have been crept in compression between 1 070 °C and 1 550 °C for stresses in the range 10 MPa-150 MPa. Oxygen partial pressures were varied between 10-5 atm. and air. The steady state creep rate seems to depend on the concentration of oxygen vacancies V"O, in agreement with an oxygen diffusion controlled creep mechanism.
TL;DR: In this paper, the shape index of a TPD peak was evaluated in connection with its use in TPD-kinetic analysis, and it was shown that the Shape Index depends on ΔH/RT and T2/T1 (i.e., the enthalpy of adsorption or the energy of activation for desorption).
TL;DR: The synthesis, characteristics, properties and metal-ion interactions of 2-(3'-sulphobenzoyl)-pyridine thiosemicarbazone and phenyl thiosine have been studied and the behaviour of the iron-reagent systems has been investigated.
TL;DR: In this article, a kinetic method is described for the determination of trace amounts of magnesium in the presence of calcium, based on the inhibition of the manganese(II) catalyzed aerial oxidation of 1,4-dihydroxyphthalimide dithiosemicarbazone reaction by 2.
TL;DR: In this paper, an analysis is made of the method proposed by Gorbachev for the kinetic study of non-isothermal transformations using the KEKAM equationα=1−exp(−ktn).
Abstract: An analysis is made of the method proposed by Gorbachev for the kinetic study of non-isothermal transformations using the KEKAM equationα=1−exp(−ktn). It is demonstrated that the procedure cannot be used to determine either the kinetic exponentn or the activation energyE.
TL;DR: In this paper, a thermopile conduction calorimeter was used for the determination of the pyroelectric coefficient of triglycine sulfate, and the results of the method were compared with the expressions deduced from thermodynamic theory.
Abstract: A calorimetric method for the determination of the pyroelectric coefficient is developed by means of a thermopile conduction calorimeter. This method is applied to the measurement of the pyroelectric coefficient of triglycine sulfate. Eleven different temperatures setting are used between 319.88 and 322.73 K; for each temperature, eleven different electric fields are applied up to a maximum of 880 V/cm. The results agree with those in the bibliography. In addition, the experimental data are compared with the expressions deduced from thermodynamic theory, yielding good results. Coefficients β and γ of the Devonshire development are evaluated and the usefullness of the method is discussed.
On decrit une methode calorimetrique pour la mesure du coefficient pyroelectrique avec un calorimetre de flux. Avec cette methode on a mesure le coefficient pyroelectrique du sulfate de glycocolle a once differents temperatures compries entre 319,88 et 322,73 K; a chaque temperature on a applique once champs electriques jusqu' a un valeur de 880 V/cm. On comparet les resultats avec ceux de la bibliographie et avec la theorie thermodynamique de la ferroelectricite. Les coefficients β et γ du developement de Devonshire sont evaluees et on fait une discussion de la methode.
TL;DR: The energy dependence of both the strong absorption radius, Rsa, and the rainbow distance, Rr, in the elastic scattering of a dozen pairs of heavy ions is studied in this paper, where the rainbow effect appears to prevail (Rr > Rsa) above a certain energy which is proportional to the product Z1Z2.