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Showing papers by "Spanish National Research Council published in 1988"


Journal ArticleDOI
TL;DR: Aldehyde groups, moderately separated from support surfaces, are proposed as suitable active groups for developing strategies to insolubilize-stabilize enzymes by multipoint covalent attachment to activated preexistent supports.

563 citations


Journal ArticleDOI
TL;DR: Variation in time (annual and seasonal) and space (between- and within-population) is examined for the pollinator assemblage of Lavandula latifolia, an insect-pollinated, summerflowering, evergreen shrub of Mediterranean woodlands in southeastern Spain, producing a spatio-temporal mosaic of pollinators.
Abstract: Variation in time (annual and seasonal) and space (between- and within-population) is examined for the pollinator assemblage of Lavandula latifolia (Labiatae), an insect-pollinated, summerflowering, evergreen shrub of Mediterranean woodlands in southeastern Spain. Lauandula latiflia is pollinated there by nearly 85 species of comparatively long-tongued Hymenoptera, Diptera and Lepidoptera. The diversity, composition and abundance of pollinators varied markedly between years. Lepidopteran taxa prevailed numerically in one year, hymenopterans in four years, and both groups had similar abundance in the remaining year. The vast majority of pollinators exhibited significant annual differences in average abundance. Only 35.7% of taxa were recorded in all of the six study years. The pollinator assemblage had marked seasonal dynamics. Important changes in species richness, abundance and composition took place over the flowering season of L. latiflia (nearly 3 months). Only 21.7y0 of insect taxa occurred throughout the flowering season. Lavandula latiflia populations at different distances from water courses differed broadly in the abundance and composition of pollinators. Hymenopterans dominated numerically at the water-distant sites, whereas lepidopterans prevailed in populations growing in the vicinity of streams. Only 40.7% of taxa were recorded at all of the four study populations. Within the same plant population, horizontal distances of the order of 25 m resulted in significant changes in pollinator composition. Variations at the four scales considered combine to produce, from the viewpoint of L. latifolia, a spatio-temporal mosaic of pollinators. As these differ broadly in frequency of pollen transfer, size of pollen loads deposited, and between-flower flight distance patterns, spatio-temporal variation will predictably result in inconsistent or contradictory selective pressures on the plant, thus hindering specialization in relation to particular pollinators.

436 citations


Journal ArticleDOI
21 Jul 1988-Nature
TL;DR: The isolation of complementary DNA and genomic clones of a gene that is ABA-inducible in the maize embryo, and whose messenger RNA accumulates in epidermial cells, which is also induced by water stress and wounding in leaves is described.
Abstract: Plant hormones such as abscisic acid (ABA) appear to modulate the responses of plants under adverse conditions1,2 ABA has a poorly-understood role in embryogenesis, accumulating in the stages before dessication3,4, and altering the rate of transcription of a specific set of genes5,6. The functions of the proteins encoded by these genes, however, are unknown, and their messenger RNAs decrease again during early germination7–9. No correlation has been established between ABA levels and the induction of particular genes in non-embryonic organs. The level of ABA increases substantially in leaf tissues subjected to water stress10 and thus it has been proposed that ABA mediates plant–water relations1,10. Here we describe the isolation of complementary DNA and genomic clones of a gene that is ABA-inducible in the maize embryo, and whose messenger RNA accumulates in epidermial cells, which is also induced by water stress and wounding in leaves. The deduced protein is rich in glycine. Identification of this gene will contribute to our understanding of the role of ABA.

417 citations


Journal ArticleDOI
TL;DR: In this article, the results of corrosion rate and simultaneous electrical resistance values of rebars in mortar fabricated with six different types of cements are given and the relation between those values is presented.

352 citations


Journal ArticleDOI
TL;DR: A generalized microplane model for brittle-plastic heterogeneous materials such as concrete, which describes not only tensile cracking but also nonlinear triaxial response in compression and shear, is presented in this article.
Abstract: A generalized microplane model for brittle-plastic heterogeneous materials such as concrete, which describes not only tensile cracking but also nonlinear triaxial response in compression and shear, is presented. The constitutive properties are characterized separately on planes of various orientations within the material, called the microplanes, on which there are only few stress and strain components and no tensorial, requirements need to be observed. These requirements are satisfied automatically by integration over all spatial directions. The state of each microplane is characterized by normal deviatoric and volumetric strains and shear strain, which makes it possible to match any Poisson ratio. The microplane strains are assumed to be the resolved components of the macroscopic strain tensor. The central assumption is that on the microplane level the stress-strain diagrams for monotonic loading are path-independent and that all the path dependence on the macrolevel is due to unloading, which happens selectively on microplanes of some orientations. The response on the microplane is assumed to depend on the lateral normal strain which does no work. in consequence, the incremental elastic moduli tensor is nonsymmetric, which is necessary to model friction and dilatancy. This tensor is also generally anistropic and fully populated (i.e., none of its elements can be prescribed as zero). The model involves many fewer free material parameters than the existing comprehensive macroscopic phenomenologic constitutive models for concrete.

316 citations


Journal ArticleDOI
TL;DR: Results indicated a marked deficiency in the metabolism of S‐adenosyl‐L‐methionine in cirrhosis.

274 citations


Journal ArticleDOI
TL;DR: Four distinct faunistic assemblages appear to be related to different hydrological characteristics, the extent of seasonal fluctuations, and to the changes in sediment structure associated with changes in the steepness of the bottom.
Abstract: We sampled the communities of decapod crustaceans inhabiting the depth zone between 3 and 871 m off the Catalan coast (North-West Mediterranean) from June 1981 to June 1983. The 185 samples comprised 90 species differing widely in their depth distributions. Multivariate analysis revealed four distinct faunistic assemblages, (1) littoral communities over sandy bottoms, (2) shelf communities over terrigenous muds, (3) upper-slope communitics, and (4) lower-slope or bathyal communities. The brachyuran crab Liocarcinus depurator is the most abundant species of the shelf assemblage, although L. vernalis dominates over the shallow sandy bottoms of the shelf. The dominant species of the upper-slope assemblage are nektobenthic species (Solenocera membranacea, Plesionika heterocarpus, Processa canaliculata), pelagic species (Pasiphaea sivado, Sergestes arcticus), and benthic species (Macropipus tuberculatus, Munida intermedia, Nephrops norvegicus). Aristeus antennatus comprise most of the biomass of the lower-slope community, which supports a greater diversity than the other assemblages. The main assemblages appear to be related to different hydrological characteristics, the extent of seasonal fluctuations, and to the changes in sediment structure associated with changes in the steepness of the bottom.

235 citations


Journal ArticleDOI
TL;DR: The 27Al and 29Si NMR signal analysis of samples heated above 400°C demonstrates that the tetrahedral sheet of kaolinite begins to break down near 600°C and continues to do so to 900°C as discussed by the authors.
Abstract: The 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS-NMR) study of the kaolinite-mullite transformation has shown the presence of Al in tetra- and pentacoordination in dehydroxylated kaolinite. The 29Si NMR signal analysis of samples heated above 400°C demonstrates that the tetrahedral sheet of kaolinite begins to break down near 600°C and continues to do so to 900°C. From the 27Al NMR signal evolution, it can be deduced that the exothermic peak at 980°C in DTA curves is associated with the modification of the coordination of Al, which changes from the tetra- or pentacoordination to the more stable octahedral coordination. Heating the sample at 880°C for 36 h produces the same transformation in the coordination of Al ions and the elimination of the exothermic peak at 980°C in the DTA diagram. After this transformation, all spectra show two tetrahedral lines characteristic of mullite, indicating that nuclei of mullite with low crystallinity are generated during the exothermic process which are not detected by XRD. At higher temperatures tetrahedral NMR peaks increase in intensity, yielding, at 1200°C, the 3:2 mullite NMR spectrum.

216 citations


Journal ArticleDOI
TL;DR: In this paper, le gradient d'abondance dans M33 est etudie sur la base d'observations spectroscopiques IPCS et CCD des raies d'emission dans les regions HII, en utilisant O I I, O I II, S I I and S I II dans l'etendue λλ3700-9600 A.
Abstract: Le gradient d'abondance dans M33 est etudie sur la base d'observations spectroscopiques IPCS et CCD des raies d'emission dans les regions HII, en utilisant O I I, O I II, S I I et S I II dans l'etendue λλ3700-9600 A pour affiner les abondances en oxygene dans les regions internes et etudier le comportement de S/O

201 citations


Journal ArticleDOI
04 Aug 1988-Nature
TL;DR: A crucial role of intracellular pH in the growth control of animal cells is supported and a more specific approach which involves expressing the gene for the yeast plasma membrane H+-ATPase7 in fibroblasts is introduced, suggesting that the yeast ATPase gene behaves as an oncogene in mammalian cells.
Abstract: A common early response of eukaryotic cells to stimuli which activate their proliferation is an increase in intracellular pH (ref. 1). In animal cells this is caused by the activation of an Na+/H+ exchange system2–5; in fungi and plants an H+-pumping ATPase6 is involved. The critical question is whether this intracellular alkalinization is merely coincident with the activation of cell proliferation or whether it is a regulatory signal2. To increase intracellular pH bypassing the usual physiological stimuli (growth factors, hormones etc.) alkaline media or ammonia have been used in the past2. Both approaches suffer from long-term toxicity effects and cannot be used in tumorigenic assays with whole organisms. We introduce here a more specific approach which involves expressing the gene for the yeast plasma membrane H+-ATPase7 in fibroblasts. The resulting cells have an elevated intracellular pH and acquire tumorigenic properties, suggesting that the yeast ATPase gene behaves as an oncogene in mammalian cells. These experiments support a crucial role of intracellular pH in the growth control of animal cells.

188 citations


Journal ArticleDOI
TL;DR: The results suggest an evolutionary relationship between phage and host lysins and the carboxyl-terminal domains of CPL and of the amidase might be responsible for the specific recognition of choline-containing cell walls, as well as for the noncompetitive inhibition of the catalytic activity of these enzymes by the pneumococcal lipoteichoic acid or by high concentrations of Choline.
Abstract: A 2.9-kilobase Acc I fragment of the DNA of the pneumococcal bacteriophage Cp-1, containing the cpl gene, hybridizes with the lytA gene encoding the pneumococcal amidase. The nucleotide sequence of the cpl gene of Cp-1, encoding a muramidase (CPL), has been determined. The 3' regions of the cpl and lytA coding sequences show considerable nucleotide sequence homology and the carboxyl-terminal domains of the deduced amino acid sequences of these lysins are quite similar: 73 of the carboxyl-terminal 142 amino acid residues are identical, and of the 69 substitutions, 55 are conservative. Comparisons between CPL, the pneumococcal amidase, and the muramidase of the fungus Chalaropsis sp. (an enzyme that also degrades the pneumococcal cell wall) strongly suggest that the carboxyl-terminal domains of CPL and of the amidase might be responsible for the specific recognition of choline-containing cell walls, as well as for the noncompetitive inhibition of the catalytic activity of these enzymes by the pneumococcal lipoteichoic acid or by high concentrations of choline. In addition, the active center of these enzymes should be located in their amino-terminal domains. Our results suggest an evolutionary relationship between phage and host lysins.

Journal ArticleDOI
TL;DR: In this paper, a parametre de souplesse du rayonnement η=(O + /O ++ )(S ++ /S + ) is defined, and l'on recommande comme critere de temperature effective des etoiles ionisantes dans les regions H II.
Abstract: On definit un parametre de souplesse du rayonnement η=(O + /O ++ )(S ++ /S + ) que l'on recommande comme critere de temperature effective des etoiles ionisantes dans les regions H II. Une etude des donnees existantes pour les regions H II geantes confirme que, pour une abondance en oxygene donnee, la temperature effective possede une limite superieure qui s'accroit avec une decroissance de l'abondance

Journal ArticleDOI
TL;DR: Cell wall analysis evidenced a five- to ninefold reduction in the amount of chitin in mutants compared with that in the wild-type strain; however, the percentage of beta-glucan that remained insoluble after alkali extraction was considerably reduced in mutant cells.
Abstract: Calcofluor is a fluorochrome that exhibits antifungal activity and a high affinity for yeast cell wall chitin. We isolated Saccharomyces cerevisiae mutants resistant to Calcofluor. The resistance segregated in a Mendelian fashion and behaved as a recessive character in all the mutants analyzed. Five loci were defined by complementation analysis. The abnormally thick septa between mother and daughter cells caused by Calcofluor in wild-type cells were absent in the mutants. The Calcofluor-binding capacity, observed by fluorescence microscopy, in a S. cerevisiae wild-type cells during alpha-factor treatment was also absent in some mutants and reduced in others. Staining of cell walls with wheat germ agglutinin-fluorescein complex indicated that the chitin uniformly distributed over the whole cell wall in vegetative or in alpha-factor-treated cells was almost absent in three of the mutants and reduced in the two others. Cell wall analysis evidenced a five- to ninefold reduction in the amount of chitin in mutants compared with that in the wild-type strain. The total amounts of cell wall mannan and beta-glucan in wild-type and mutant strains were similar; however, the percentage of beta-glucan that remained insoluble after alkali extraction was considerably reduced in mutant cells. The susceptibilities of the mutants and the wild-type strains to a cell wall enzymic lytic complex were rather similar. The in vitro levels of chitin synthase 2 detected in all mutants were similar to that in the wild type. The significance of these results is discussed in connection with the mechanism of chitin synthesis and cell wall morphogenesis in S. cerevisiae.

Journal ArticleDOI
TL;DR: In this paper, the p/o selectivity in the isomerization of m-xylene is always high for ten-membered ring zeolites with crystals bigger than 1 μm.

Journal ArticleDOI
TL;DR: The observed phosphorylation of a protein identified as MAP-1B during neurite outgrowth is mainly due to the activation of a casein kinase II-related activity in differentiating neuroblastoma cells, suggesting an important role in posttranslational modifications of microtubule proteins required for neuronal differentiation.
Abstract: A neuroblastoma protein related to the brain microtubule-associated protein, MAP-1B, as determined by immunoprecipitation and coassembly with brain microtubules, becomes phosphorylated when N2A mouse neuroblastoma cells are induced to generate microtubule-containing neurites. To characterize the protein kinases that may be involved in this in vivo phosphorylation of MAP-1B, we have studied its in vitro phosphorylation. In brain microtubule protein, MAP-1B appears to be phosphorylated in vitro by an endogenous casein kinase II-like activity which also phosphorylates the related protein MAP-1A but scarcely phosphorylates MAP-2. A similar kinase activity has been detected in cell-free extracts of differentiating N2A cells. Using brain MAP preparations devoid of endogenous kinase activities and different purified protein kinases, we have found that MAP-1B is barely phosphorylated by cAMP-dependent protein kinase, Ca/calmodulin-dependent protein kinase, or Ca/phospholipid-dependent protein kinase whereas MAP-1B is one of the preferred substrates, together with MAP-1A, for casein kinase II. Brain MAP-1B phosphorylated in vitro by casein kinase II efficiently coassembles with microtubule proteins in the same way as in vivo phosphorylated MAP-1B from neuroblastoma cells. Furthermore, the phosphopeptide patterns of brain MAP-1B phosphorylated in vitro by either purified casein kinase II or an extract obtained from differentiating neuroblastoma cells are identical to each other and similar to that of in vivo phosphorylated neuroblastoma MAP-1B. Thus, we suggest that the observed phosphorylation of a protein identified as MAP-1B during neurite outgrowth is mainly due to the activation of a casein kinase II-related activity in differentiating neuroblastoma cells. This kinase activity, previously implicated in beta-tubulin phosphorylation (Serrano, L., J. Diaz-Nido, F. Wandosell, and J. Avila, 1987. J. Cell Biol. 105: 1731-1739), may consequently have an important role in posttranslational modifications of microtubule proteins required for neuronal differentiation.

Journal ArticleDOI
15 Feb 1988-Gene
TL;DR: Recombinant plasmids have been obtained that lead to the accumulation of five- to ten-fold more puromycin-N-acetyl-transferase (PAC) mRNA and two- to three-foldMore PAC activity than the already described plasmid pSV2pac, indicating that these pac-containing recombinants may be very useful dominant selectable markers for gene transfer in mammalian cells.

Journal ArticleDOI
TL;DR: In this article, the polar compounds previously obtained from heated fats by column chromatography are separated by high performance size exclusion chromatography (HPSEC) to increase knowledge of the alteration of frying fats.
Abstract: In this paper, separation of the polar compounds previously obtained from heated fats by column chromatography is proposed in order to increase knowledge of the alteration of frying fats. The analysis is carried out in 35 min by high performance size exclusion chromatography (HPSEC). The results demonstrate that the contribution of thermoxidative and hydrolytic degradations can be quantified. The method can also be applied to a better definition of non-heated fats.

Journal ArticleDOI
TL;DR: The presence of gross preferentially distributed striations on the buccal surfaces of permanent anterior teeth of Neandertal individuals from La Quina, Hortus and Angles-sur-l'Anglin (France), Saint Brais (Switzerland) and Shanidar (Iraq) has led some authors to hypothesize that Neandergals used stone tools to cut something held between the anterior teeth, inadvertently scratching the enamel at the same time.

Journal ArticleDOI
TL;DR: In this article, the 13C chemical shifts and a large collection of coupling constants have been measured for 169 N-substituted azoles with no other substituents on the ring.
Abstract: The 13C chemical shifts and a large collection of coupling constants have been measured for 169 N-substituted azoles with no other substituents on the ring. Simple additive models have been used to discuss both the chemical shifts and the coupling constants. The chemical shift of the substituent depends on the nature of the azole which can, accordingly, be classified into three to six families. Some structural problems (ring-chain isomerism of 1-trifluoromethylsulphonyl-1,2,3-triazole, silylotropy and stannotropy) are also discussed.

Journal ArticleDOI
TL;DR: The general microplane model formulated in Part I of this study is calibrated and verified by comparison with numerous nonlinear triaxial test data from the literature and good agreement is achieved.
Abstract: The general microplane model formulated in Part I of this study is calibrated and verified by comparison with numerous nonlinear triaxial test data from the literature and good agreement is achieved. The model involves many fewer material parameters than the previous phenomenologic macroscopic models. Numerical implementation is also considered.

Journal ArticleDOI
TL;DR: The room temperature structure of SrFe/sub 12/O/sub 19/ hexagonal ferrite has been refined from X-ray single-crystal data in this article, where structural isomorphism of the title compound with the hexagonal Ferrite BaFe/s 12 O/s 19/ has been demonstrated, corroborating that the bipyramidal Fe ions have a fast diffusional motion within a quasiharmonic double-well potential as in BaFe

Journal ArticleDOI
TL;DR: In this paper, the renormalisation of gauge coupling constants in theories with a G × U(1) N gauge group was examined, and it was shown that the mixing is scale independent to all orders.

Journal ArticleDOI
TL;DR: In this article, the utility of infrared and Raman spectroscopy in the characterization of powdered samples is illustrated for the case of TiO2 (rutile) by showing that particle shape and state of aggregation of the microcrystals are shown to have a strong effect on the infrared powder spectra as predicted by the Theory of the Average Dielectric Constant.

Journal ArticleDOI
TL;DR: In this article, the Weyl-Wigner transformation is extended to those particular degrees of freedom described by a finite number of states using a technique of constructing operator bases developed by Schwinger.
Abstract: We extend the Weyl-Wigner transformation to those particular degrees of freedom described by a finite number of states using a technique of constructing operator bases developed by Schwinger. Discrete transformation kernels are presented instead of continuous coordinate-momentum pair system and systems such as the one-dimensional canonical continuous coordinate-momentum pair system and the two-dimensional rotation system are described by special limits. Expressions are explicitly given for the spin one-half case.

Journal ArticleDOI
TL;DR: In this paper, a series of ambers and resins derived from different locations (Dominican Republic, Philippines, Canada, Israel, New Zealand, Chile) having diverse botanical affinities (Araucariaceae, Hymenaea) and variable age (from Holocene to Early Cretaceous).

Journal ArticleDOI
01 Jul 1988-Geoderma
TL;DR: In this article, fire-induced changes in humic and lipid soil fractions were assessed by two approaches: preparation liquid chromatography (CLC) and GC-MS in the case of humic acids.

Journal ArticleDOI
TL;DR: The data strongly support the idea that thyroid hormones influence human brain development at least from the 9th to the 10th week of gestational age and suggest the presence of a small gradient between nuclear and cytosolic free T3 in both fetal tissues.
Abstract: The total number and saturation of nuclear receptors for T3 were measured in human fetal brain and lung from the 9th to the 13th week of fetal life. The concentrations of occupied and unoccupied receptor sites were determined by measuring total binding capacity at 0 and 22 C. At 0 C [125I]T3 was bound mainly to unoccupied sites, whereas at 22 C it was bound to unoccupied sites plus a fraction (70%) of endogenously occupied sites. Saturations of brain and lung receptors were similar (12–27%). From the fractional receptor occupancy and the receptor dissociation constants (34 pmol/L in brain and 56 pmol/L in lung) the concentration of intranuclear free T3 was calculated to be 9 pmol/L in brain and 11 pmol/L in lung. Total and free cytosolic T3 were measured by RIA and equilibrium dialysis. Total T3 was below the limit of detection in lung (90 pmol/L). The concentration of free T3 in brain cytosol was 0.95 pmol/L at 11 weeks and 2.96 pmol/L at 13 weeks, i.e. considerably lower than the nuclear free T3 concent...

Journal ArticleDOI
TL;DR: The production of superoxide free radicals in pellet and supernatant fractions of glyoxysomes, specialized plant peroxisomes from watermelon cotyledons, and the generation of O(2) (-) radicals in glyxysomes by endogenous metabolites suggests new active oxygen-related roles for glyoxesomes, and for perxisomes in general, in cellular metabolism.
Abstract: The production of superoxide free radicals in pellet and supernatant fractions of glyoxysomes, specialized plant peroxisomes from watermelon (Citrullus vulgaris Schrad.) cotyledons, was investigated. Upon inhibition of the endogenous superoxide dismutase, xanthine, and hypoxanthine induced in glyoxysomal supernatants the generation of O2− radicals and this was inhibited by allopurinol. In glyoxysomal pellets, NADH stimulated the generation of superoxide radicals. Superoxide production by purines was due to xanthine oxidase, which was found predominantly in the matrix of glyoxysomes. The generation of O2− radicals in glyoxysomes by endogenous metabolites suggests new active oxygen-related roles for glyoxysomes, and for peroxisomes in general, in cellular metabolism.

Journal ArticleDOI
01 Apr 1988
TL;DR: In this article, the authors define a set of equations constitutives decrivant chacun des trois mecanismes independant deformation: glissement des dislocations, glissements des joints de grains, and flux diffusionnel directionnel.
Abstract: L'ecoulement plastique des solides polycristallins a lieu par l'un des trois mecanismes independants de deformation: glissement des dislocations, glissement des joints de grains, et flux diffusionnel directionnel. Developpement des equations constitutives decrivant chacun des trois mecanismes. Les equations se fondent sur une dependance exponentielle de la vitesse de deformation. Determination de l'exposant de contrainte. Influence de la microstructure: taille des grains, taille des sous-grains, densite des dislocations. Description quantitative des competitions entre ces differents mecanismes. Analyse du processus dominant

Journal ArticleDOI
TL;DR: The surface interactions of CO, CO2 and H2 with perovskite-type oxide LaCoO3 as a function of the reduction temperature have been studied by means of XPS and TPD spectroscopies as mentioned in this paper.