Showing papers by "Spanish National Research Council published in 1998"
01 Mar 1998
TL;DR: The paradigm shift from a transfer view to a modeling view is discussed and two approaches which considerably shaped research in Knowledge Engineering are described: Role-limiting Methods and Generic Tasks.
Abstract: This paper gives an overview of the development of the field of Knowledge Engineering over the last 15 years. We discuss the paradigm shift from a transfer view to a modeling view and describe two approaches which considerably shaped research in Knowledge Engineering: Role-limiting Methods and Generic Tasks. To illustrate various concepts and methods which evolved in recent years we describe three modeling frameworks: CommonKADS, MIKE and PROTEGE-II. This description is supplemented by discussing some important methodological developments in more detail: specification languages for knowledge-based systems, problem-solving methods and ontologies. We conclude by outlining the relationship of Knowledge Engineering to Software Engineering, Information Integration and Knowledge Management.
3,406 citations
TL;DR: In this article, the topological properties of ρ(r) at the intermolecular critical points of 83 experimentally observed hydrogen bonds [X-H⋯O (X=C,N,O)], using accurate X-ray diffraction experiments, were analyzed.
2,675 citations
TL;DR: In this article, the kinetic behavior of polyphenols common in fruits as free radical scavengers was studied using 2,2-diphenyl-1-picrylhydrazyl (DPPH).
Abstract: The kinetic behaviour of polyphenols common in fruits as free radical scavengers was studied using 2,2-diphenyl-1-picrylhydrazyl (DPPH.). After addition of different standard concentrations to DPPH. (0.025 g litre-1), the percentage of remaining DPPH. was determined at different times from the absorbances at 515 nm. The percentage remaining DPPH. against reaction time followed a multiplicative model equation: In [DPPH.REM] = b 1n t + 1n a. The slopes of these equations may be useful parameters to define the antioxidant capacity. The steeper the slope, the lower the amount of antioxidant necessary to decrease by 50% the initial DPPH. concentration (EC50). This parameter, EC50, is widely used to measure antioxidant power, but it does not takes into account the reaction time. Time needed to reach the steady state to the concentration corresponding at EC50 (T(EC50)) was calculated, and antiradical efficiency (AE) was proposed as a new parameter to characterise the antioxidant compounds where AE = 1/EC50 T(EC50). It was shown that AE is more discriminatory than EC50. AE values are more useful because they also take into account the reaction time. The results have shown that the order of the AE (x 10(-3)) in the compounds tested was: ascorbic acid (11.44) > caffeic acid (2.75) greater than or equal to gallic acid (2.62) > tannic acid (0.57) greater than or equal to DL-alpha-tocopherol (0.52) > rutin (0.21) greater than or equal to quercetin (0.19) > ferulic acid (0.12) greater than or equal to 3-tert-butyl-4-hydroxyanisole, BHA (0.10) > resveratrol (0.05).
1,812 citations
TL;DR: It is possible in certain cases to propose a partial model of the way in which the different elements involved in catabolite repression may be integrated, and preliminary evidence suggests that Snf1 is in a dephosphorylated state under these conditions.
Abstract: Glucose and related sugars repress the transcription of genes encoding enzymes required for the utilization of alternative carbon sources; some of these genes are also repressed by other sugars such as galactose, and the process is known as catabolite repression. The different sugars produce signals which modify the conformation of certain proteins that, in turn, directly or through a regulatory cascade affect the expression of the genes subject to catabolite repression. These genes are not all controlled by a single set of regulatory proteins, but there are different circuits of repression for different groups of genes. However, the protein kinase Snf1/Cat1 is shared by the various circuits and is therefore a central element in the regulatory process. Snf1 is not operative in the presence of glucose, and preliminary evidence suggests that Snf1 is in a dephosphorylated state under these conditions. However, the enzymes that phosphorylate and dephosphorylate Snf1 have not been identified, and it is not known how the presence of glucose may affect their activity. What has been established is that Snf1 remains active in mutants lacking either the proteins Grr1/Cat80 or Hxk2 or the Glc7 complex, which functions as a protein phosphatase. One of the main roles of Snf1 is to relieve repression by the Mig1 complex, but it is also required for the operation of transcription factors such as Adr1 and possibly other factors that are still unidentified. Although our knowledge of catabolite repression is still very incomplete, it is possible in certain cases to propose a partial model of the way in which the different elements involved in catabolite repression may be integrated.
1,246 citations
TL;DR: The results place p14ARF in an independent pathway upstream of p53 and imply that CDKN2A encodes two proteins that are involved in tumour suppression.
Abstract: The two distinct proteins encoded by the CDKN2A locus are specified by translating the common second exon in alternative reading frames The product of the alpha transcript, p16(INK4a), is a recognized tumour suppressor that induces a G1 cell cycle arrest by inhibiting the phosphorylation of the retinoblastoma protein by the cyclin-dependent kinases, CDK4 and CDK6 In contrast, the product of the human CDKN2A beta transcript, p14(ARF), activates a p53 response manifest in elevated levels of MDM2 and p21(CIP1) and cell cycle arrest in both G1 and G2/M As a consequence, p14(ARF)-induced cell cycle arrest is p53 dependent and can be abrogated by the co-expression of human papilloma virus E6 protein p14(ARF) acts by binding directly to MDM2, resulting in the stabilization of both p53 and MDM2 Conversely, p53 negatively regulates p14(ARF) expression and there is an inverse correlation between p14(ARF) expression and p53 function in human tumour cell lines However, p14(ARF) expression is not involved in the response to DNA damage These results place p14(ARF) in an independent pathway upstream of p53 and imply that CDKN2A encodes two proteins that are involved in tumour suppression
1,171 citations
TL;DR: Most of the current knowledge on plasmid replication and its control is based on the results of analyses performed with pure cultures under steady-state growth conditions, and sets important parameters needed to understand the maintenance of these genetic elements in mixed populations and under environmental conditions.
Abstract: SUMMARY An essential feature of bacterial plasmids is their ability to replicate as autonomous genetic elements in a controlled way within the host. Therefore, they can be used to explore the mechanisms involved in DNA replication and to analyze the different strategies that couple DNA replication to other critical events in the cell cycle. In this review, we focus on replication and its control in circular plasmids. Plasmid replication can be conveniently divided into three stages: initiation, elongation, and termination. The inability of DNA polymerases to initiate de novo replication makes necessary the independent generation of a primer. This is solved, in circular plasmids, by two main strategies: (i) opening of the strands followed by RNA priming (theta and strand displacement replication) or (ii) cleavage of one of the DNA strands to generate a 3′-OH end (rolling-circle replication). Initiation is catalyzed most frequently by one or a few plasmid-encoded initiation proteins that recognize plasmid-specific DNA sequences and determine the point from which replication starts (the origin of replication). In some cases, these proteins also participate directly in the generation of the primer. These initiators can also play the role of pilot proteins that guide the assembly of the host replisome at the plasmid origin. Elongation of plasmid replication is carried out basically by DNA polymerase III holoenzyme (and, in some cases, by DNA polymerase I at an early stage), with the participation of other host proteins that form the replisome. Termination of replication has specific requirements and implications for reinitiation, studies of which have started. The initiation stage plays an additional role: it is the stage at which mechanisms controlling replication operate. The objective of this control is to maintain a fixed concentration of plasmid molecules in a growing bacterial population (duplication of the plasmid pool paced with duplication of the bacterial population). The molecules involved directly in this control can be (i) RNA (antisense RNA), (ii) DNA sequences (iterons), or (iii) antisense RNA and proteins acting in concert. The control elements maintain an average frequency of one plasmid replication per plasmid copy per cell cycle and can “sense” and correct deviations from this average. Most of the current knowledge on plasmid replication and its control is based on the results of analyses performed with pure cultures under steady-state growth conditions. This knowledge sets important parameters needed to understand the maintenance of these genetic elements in mixed populations and under environmental conditions.
907 citations
TL;DR: In this paper, seven different composts were prepared by the Rutgers static-pile system using a wide range of wastes: sewage sludge, poultry manure, pig slurry, olive mill wastewater city refuse and the lignocellulosic wastes cotton waste, maize straw and sweet sorghum bagasse.
833 citations
John Innes Centre1, Harvard University2, Ghent University3, University of Paris4, Trinity College, Dublin5, University of East Anglia6, Spanish National Research Council7, Agricultural University of Athens8, MediGene9, Centre national de la recherche scientifique10, Katholieke Universiteit Leuven11, Max Planck Society12
TL;DR: Analysis of the sequence revealed an average gene density of one gene every 4.8 kilobases, and 54% of the predicted genes had significant similarity to known genes, and other interesting features were found, such as the sequence of a disease-resistance gene locus, the distribution of retroelements, and the frequent occurrence of clustered gene families.
Abstract: The plant Arabidopsis thaliana (Arabidopsis) has become an important model species for the study of many aspects of plant biology. The relatively small size of the nuclear genome and the availability of extensive physical maps of the five chromosomes provide a feasible basis for initiating sequencing of the five chromosomes. The YAC (yeast artificial chromosome)-based physical map of chromosome 4 was used to construct a sequence-ready map of cosmid and BAC (bacterial artificial chromosome) clones covering a 1.9-megabase (Mb) contiguous region, and the sequence of this region is reported here. Analysis of the sequence revealed an average gene density of one gene every 4.8 kilobases (kb), and 54% of the predicted genes had significant similarity to known genes. Other interesting features were found, such as the sequence of a disease-resistance gene locus, the distribution of retroelements, the frequent occurrence of clustered gene families, and the sequence of several classes of genes not previously encountered in plants.
832 citations
TL;DR: Statins were able to prevent the inhibitory action exerted by oxidized LDL on eNOS mRNA and protein levels and might influence vascular tone by modulating the expression of endothelial vasoactive factors.
Abstract: Endothelial dysfunction associated with atherosclerosis has been attributed to alterations in the L-arginine-nitric oxide (NO)-cGMP pathway or to an excess of endothelin-1 (ET-1). The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have been shown to ameliorate endothelial function. However, the physiological basis of this observation is largely unknown. We investigated the effects of Atorvastatin and Simvastatin on the pre-proET-1 mRNA expression and ET-1 synthesis and on the endothelial NO synthase (eNOS) transcript and protein levels in bovine aortic endothelial cells. These agents inhibited pre-proET-1 mRNA expression in a concentration- and time-dependent fashion (60-70% maximum inhibition) and reduced immunoreactive ET-1 levels (25-50%). This inhibitory effect was maintained in the presence of oxidized LDL (1-50 microg/ml). No significant modification of pre-proET-1 mRNA half-life was observed. In addition, mevalonate, but not cholesterol, reversed the statin-mediated decrease of pre-proET-1 mRNA levels. eNOS mRNA expression was reduced by oxidized LDL in a dose-dependent fashion (up to 57% inhibition), whereas native LDL had no effect. Statins were able to prevent the inhibitory action exerted by oxidized LDL on eNOS mRNA and protein levels. Hence, these drugs might influence vascular tone by modulating the expression of endothelial vasoactive factors.
775 citations
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TL;DR: The effects of salinity on tomato plant growth and fruit production, the cultural techniques which can be applied to alleviate the deleterious effects of salt, and the possibilities of breeding salt-tolerant tomatoes are reviewed.
763 citations
TL;DR: In this paper, a spin-glass-like transition was found in magnetic nanoparticles, with a very high surface to volume ratio, exhibiting both strong exchange anisotropy and magnetic training effect.
Abstract: $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ magnetic nanoparticles, with a very high surface to volume ratio, exhibit both strong exchange anisotropy and magnetic training effect. At the same time high field irreversibility in $M\left(H\right)$ curves and zero field cooled--field cooled (ZFC-FC) processes has also been detected. A low temperature spin-glass-like transition is evidenced at ${T}_{F}\ensuremath{\approx}42\mathrm{K}$ with strong irreversibility even at $H\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}55\mathrm{kOe}$. ${T}_{F}\left(H\right)$ evolves following the well known de Almeida--Thouless line $\ensuremath{\delta}{T}_{F}\ensuremath{\propto}{H}^{2/3}$. The thermal dependence of the exchange anisotropy field ${H}_{E}$ is described by the random-field model of exchange anisotropy. In the framework of this theory, a surface spin-glass layer about 0.6 nm thick is determined.
TL;DR: PARP−/− cells are extremely sensitive to apoptosis induced by triggers (like alkylating agents), which activates the base excision repair pathway of DNA, and the cleavage of PARP during apoptosis facilitates cellular disassembly and ensures the completion and irreversibility of the process.
TL;DR: Because EG seem to provide injured spinal axons with appropriate factors for long-distance elongation, these cells offer new possibilities for treatment of CNS conditions that require axonal regeneration.
Abstract: The lack of axonal regeneration in the injured adult mammalian spinal cord leads to permanent functional impairment. To induce axonal regeneration in the transected adult rat spinal cord, we have used the axonal growth-promoting properties of adult olfactory bulb ensheathing glia (EG). Schwann cell (SC)-filled guidance channels were grafted to bridge both cord stumps, and suspensions of pure (98%) Hoechst-labeled EG were stereotaxically injected into the midline of both stumps, 1 mm from the edges of the channel. In EG-transplanted animals, numerous neurofilament-, GAP-43-, anti-calcitonin gene-related peptide (CGRP)-, and serotonin-immunoreactive fibers traversed the glial scars formed at both cord–graft interfaces. Supraspinal serotonergic axons crossed the transection gap through connective tissue bridges formed on the exterior of the channels, avoiding the channel interior. Strikingly, after crossing the distal glial scar, these fibers elongated in white and periaqueductal gray matter, reaching the farthest distance analyzed (1.5 cm). Tracer-labeled axons present in SC grafts were found to extend across the distal interface and up to 800 μm beyond in the distal cord. Long-distance regeneration (at least 2.5 cm) of injured ascending propriospinal axons was observed in the rostral spinal cord. Transplanted EG migrated longitudinally and laterally from the injection sites, reaching the farthest distance analyzed (1.5 cm). They moved through white matter tracts, gray matter, and glial scars, overcoming the inhibitory nature of the CNS environment, and invaded SC and connective tissue bridges and the dorsal and ventral roots adjacent to the transection site. Transplanted EG and regenerating axons were found in the same locations. Because EG seem to provide injured spinal axons with appropriate factors for long-distance elongation, these cells offer new possibilities for treatment of CNS conditions that require axonal regeneration.
TL;DR: It is shown that p19ARF in the mouse (the human homologue is called p14ARF) is essential for the activation of p53 in response to oncogenic Ras, and this results dissociate the activationof p53 into two pathways: one pathway is induced by DNA damage and is independent of p19 ARF, whereas the other pathway isinduced by oncogens Ras and is dependent on p19arF.
Abstract: Normal healthy cells possess safeguard mechanisms that sense oncogenic signals and trigger anti-tumorigenic responses that limit the proliferative potential of cells harbouring active oncogenes1. In particular, expression of the Ras oncogene in normal primary cells causes a cell-cycle arrest that involves the activation of the tumoursuppressor protein p53 (ref. 2). It has recently been reported that the tumour-suppressor p19ARF can activate p53 (3–5). Here we show that p19ARF in the mouse (the human homologue is called p14ARF) is essential for the activation of p53 in response to oncogenic Ras. These results, together with the finding that p19ARF does not mediate the activation of p53 by DNA damage6, dissociate the activation of p53 into two pathways: one pathway is induced by DNA damage and is independent of p19ARF, whereas the other pathway is induced by oncogenic Ras and is dependent on p19ARF.
TL;DR: This review provides a general introduction to the subject of antimicrobial peptides, with emphasis on aspects such as structural types, post-translational modifications, mode of action or mechanisms of resistance.
Abstract: Antibiotic peptides are a key component of the innate immune systems of most multicellular organisms. Despite broad divergences in sequence and taxonomy, most antibiotic peptides share a common mechanism of action, i.e., membrane permeabilization of the pathogen. This review provides a general introduction to the subject, with emphasis on aspects such as structural types, post-translational modifications, mode of action or mechanisms of resistance. Some of these questions are treated in depth in other reviews in this issue. The review also discusses the role of antimicrobial peptides in nature, including several pathological conditions, as well as recent accounts of their application at the preclinical level.
TL;DR: It is proposed that benthic suspension feeders can self-organize to enhance food capture and thus establish boundary systems capable of successfully exploiting a less structured system, namely, the plankton.
Abstract: In recent years, particular attention has been paid to coupling and energy transfer between benthos and plankton. Because of their abundance, certain benthic suspension feeders have been shown to have a major impact in marine ecosystems. They capture large quantities of particles and might directly regulate primary production and indirectly regulate secondary production in littoral food chains. Suspension feeders develop dense, three-dimensional communities whose structural complexity depends on flow speed. It has been postulated that these communities can self-organize to enhance food capture and thus establish boundary systems capable of successfully exploiting a less structured system, namely, the plankton.
TL;DR: In this article, a new class of precursors, based around polyol silicates, derived from glycerol, was described and employed for sol−gel bioentrapment in an approach distinguished by a high biocompatibility and mild encapsulation conditions, and which enables the reproducible and efficient confinement of proteins and cells inside silica.
Abstract: The sol−gel encapsulation of labile biological materials with catalytic and recognition functions within robust polymer matrices remains a challenging task, despite the considerable research that has been focused on this field. Herein, we describe a new class of precursors, based around polyol silicates and polyol siloxanes, especially those derived from glycerol, that addresses problems faced with traditional bioencapsulation protocols. Poly(glyceryl silicate) (PGS) was prepared and employed for sol−gel bioentrapment, in an approach distinguished by a high biocompatibility and mild encapsulation conditions, and which enables the reproducible and efficient confinement of proteins and cells inside silica. The methodology was extended to metallosilicate, alkylsiloxane, functionalized siloxane, and composite sol−gels, thereby allowing the fabrication of a physicochemically diverse range of bio-doped polymers. The hybrid materials display activities approaching those of the free biologicals, together with the...
TL;DR: In this paper, the Langevin-dynamics approach was used to study the dynamics of magnetic nanoparticles, and the results were compared with different analytical expressions used to model the relaxation of nanoparticle ensembles, assessing their accuracy.
Abstract: The stochastic Landau-Lifshitz-Gilbert equation of motion for a classical magnetic moment is numerically solved (properly observing the customary interpretation of it as a Stratonovich stochastic differential equation), in order to study the dynamics of magnetic nanoparticles. The corresponding Langevin-dynamics approach allows for the study of the fluctuating trajectories of individual magnetic moments, where we have encountered remarkable phenomena in the overbarrier rotation process, such as crossing-back or multiple crossing of the potential barrier, rooted in the gyromagnetic nature of the system. Concerning averaged quantities, we study the linear dynamic response of the archetypal ensemble of noninteracting classical magnetic moments with axially symmetric magnetic anisotropy. The results are compared with different analytical expressions used to model the relaxation of nanoparticle ensembles, assessing their accuracy. It has been found that, among a number of heuristic expressions for the linear dynamic susceptibility, only the simple formula proposed by Shliomis and Stepanov matches the coarse features of the susceptibility reasonably. By comparing the numerical results with the asymptotic formula of Storonkin {Sov. Phys. Crystallogr. 30, 489 (1985) [Kristallografiya 30, 841 (1985)]}, the effects of the intra-potential-well relaxation modes on the low-temperature longitudinal dynamic response have been assessed, showing their relatively small reflection in the susceptibility curves but their dramatic influence on the phase shifts. Comparison of the numerical results with the exact zero-damping expression for the transverse susceptibility by Garanin, Ishchenko, and Panina {Theor. Math. Phys. (USSR) 82, 169 (1990) [Teor. Mat. Fiz. 82, 242 (1990)]}, reveals a sizable contribution of the spread of the precession frequencies of the magnetic moment in the anisotropy field to the dynamic response at intermediate-to-high temperatures.
TL;DR: Palaeo-reconstruction of the Apenninic arc suggests about 775 km of migration from the Late Oligocene to present along a transect from the Gulf of Lions to Calabria.
TL;DR: A.M.
Abstract: P. Schuster and P.F. Stadler, Nature and Evolution of Early Replicons. H.D. Robertson and O.D. Neel, Virus Origins: Conjoined RNA Genomes as Precursors to DNA Genomes. J.S. Semancik and N. Duran-Vila, Viroids in Plants: Shadows and Footprints of a Primitive RNA. C. Biebricher, Mutation, Competition, and Selection as Measured with Small RNA Molecules. A. Meyerhans and J.-P. Vartanian, The Fidelity of Cellular and Viral Polymerases and Its Manipulation for Hypermutagenesis. S. Wain-Hobson and M. Sala, Drift and Conservatism in RNA Virus Evolution: Are They Adapting or Merely Changing? E. Domingo, C. Escarmis, L. Menendez-Aarias, and J.J. Holland, Viral Quasispecies and Fitness Variations. M.A. McClure, The Retroid Agents: Disease, Function, and Evolution. D. Wodarz and M.A. Nowak, Dynamics of HIV Pathogenesis and Treatment. I.M. Rouzine and J.M. Coffin, Interplay between Experiment and Theory in Development of a Working Model for HIV-1 Population Dynamics. A.J. Gibbs, P.L. Keese, M.J. Gibbs, and F. Garcia-Arenal, Plant Virus Evolution: Past, Present, and Future. M. Gromeier, E. Wimmer, and A.E. Gorbalenya, Genetics, Pathogenesis, and Evolution of Picornaviruses. J.I. Esteban, M. Martell, W.F. Carman, and J. Gomez, The Impact of Rapid Evolution of the Hepatitis Viruses. R.G. Webster, Antigenic Variation in Influenza Viruses. L.P. Villarreal, DNA Virus Contribution to Host Evolution. C.R. Parrish and U. Truyen, Parvovirus Variation and Evolution. D.J. McGeoch and A.J. Davison, The Molecular Evolutionary History of the Herpesviruses. J. Salas, M.L. Salas, and E. Vinuela, African Swine Fever Virus: A Missing Link Between Poxviruses and Iridoviruses? Subject Index.
TL;DR: A systematic search for the function of all genes of this large family of regulatory genes in Arabidopsis thaliana revealed conserved amino acid motifs shared by subgroups of R2R3-MYB genes in addition to the characteristic DNA-binding domain.
Abstract: Transcription factors containing a conserved DNA-binding domain similar to that of the proto-oncogene c-myb have been identified in nearly all eukaryotes. MYB-related proteins from plants generally contain two related helix-turn-helix motifs, the R2 and R3 repeats. It was estimated that Arabidopsis thaliana contains more than 100 R2R3-MYB genes. The few cases where functional data are available suggest an important role of these genes in the regulation of secondary metabolism, the control of cell shape, disease resistance, and hormone responses. To determine the full regulatory potential of this large family of regulatory genes, a systematic search for the function of all genes of this family was initiated. Sequence data for more than 90 different A. thaliana R2R3-MYB genes have been obtained. Sequence comparison revealed conserved amino acid motifs shared by subgroups of R2R3-MYB genes in addition to the characteristic DNA-binding domain. No significant clustering of the genes was detected, although they are not uniformly distributed throughout the A. thaliana genome.
TL;DR: The hypothesis that enhanced germination may be more advantageous in unpredictable or less constant environments is supported.
Abstract: The capacity of seeds to germinate after ingestion by frugivores is important for the population dynamics of some plant species and significant for the evolution of plant-frugivore interactions. In this paper the effects of different vertebrates on seed germination of nearly 200 plant species are reviewed, searching for patterns that predict the circumstances in which germination of seeds is enhanced, inhibited, or unaffected by the passage through the digestive tract of a seed disperser. It was found that seed dispersers commonly have an effect on the germinability of seeds, or on the rate of germination, or both, in about 50% of the plants they consume, although the diversity of animal species tested so far is still rather low (42 bird species, 28 non-flying mammals, 10–15 bats, 12 reptiles, 2 fishes). Enhancement of germination occurred about twice as often as inhibition. In spite of the morphological and physiological differences in their digestive tracts, the different animal groups tested have similar effects on seed germination, although non-flying mammals tend to influence germination slightly more often than the other groups. Data on fishes are still too scarce for any generalization. Seed retention time in the dispersers' digestive tract is one factor affecting germination, and helps to explain the variation in seed responses observed among plant species, and even within a species. However other factors are also important; for example, the type of food ingested along with the fruits may affect germination through its influence on chemical or mechanical abrasion of the seed coat. Seed traits such as coat structure or thickness may themselves be responsible for some of the variation in seed retention times. Seeds of different sizes, which usually have different transit times through frugivores, and seeds of either fleshy or dry fruits, show often similar germination response to gut passage. Seeds of different plants species differ strongly in their germination response after ingestion, even by the same frugivore species. Congeneric plants often show little consistency in their response. Even within a species variation is found which can be related to factors such as the environmental conditions under which germination takes place, seed morphology, seed age, and the season when the seeds are produced. The effect of gut passage on germination differs between tropical and temperate zones. Seed germination of both shrubs and trees (data on herbaceous species are still scarce) in the temperate zone is more frequently enhanced than in the tropics. This result supports the hypothesis that enhanced germination may be more advantageous in unpredictable or less constant environments. Significant differences in frugivore-mediated germination are also found among different life forms. In both tropical and temperate zones, trees appear to be consistently more affected than shrubs or herbs. This might be due to an overall higher thickness of the seed coats, or to a higher frequency of seed-coat dormancy in tree species. The influence of frugivory upon the population dynamics of a species has to be evaluated relative to other factors that influence germination and seedling recruitment at a particular site. Whether seed ingestion by dispersers is really advantageous to a plant (as has commonly been assumed) can only be assessed if we also determine the fate of the ingested seeds under natural conditions, and compare it to the fate of seeds that have not been ingested.
TL;DR: In this paper, a grid of empirically well tested evolutionary tracks with masses M between 0.5 and 50 m⊙, spaced by approximately 0.1 in log M, and with metallicities Z = 0.03.
Abstract: We have calculated a grid of empirically well tested evolutionary tracks with masses M between 0.5 and 50 M⊙, spaced by approximately 0.1 in log M, and with metallicities Z = 0.0001, 0.0003, 0.001, 0.004, 0.01, 0.02 and 0.03. We use a robust and fast evolution code with a self-adaptive non-Lagrangian mesh, which employs the mixing-length theory but treats convective mixing as a diffusion process, solving simultaneously for the structure and the chemical composition. The hydrogen and helium abundances are chosen as functions of the metallicity: X = 0.76 − 3.0ZY = 0.24 + 2.0Z. Two sets of models were computed, one without and one with a certain amount of enhanced mixing or ‘overshooting’. This amount has been empirically chosen by means of various sensitive tests for overshooting: (1) the luminosity of core helium burning (blue loop) giants of well-known mass, (2) the width of the main sequence as defined by double-lined eclipsing binaries with well-measured masses and radii, and (3) the shape and implied stellar distribution of isochrones of various open clusters. The first two tests have been the subject of previous papers, the third test is discussed in this paper. On the basis of these tests, we recommend the use of the overshooting models for masses above about 1.5M ⊙. We describe here the characteristics of the models, the procedure for constructing isochrones for arbitrary age and metallicity from the models, and the performance of these isochrones for several intermediate-age and old open clusters. All original models are available in electronic form and we describe the means by which they may be obtained.
TL;DR: In this paper, the authors tried to quantify the relationship between the amount of corrosion and cover cracking and showed that the corrosion is accelerated by applying constant currents causing the rebar to act as an anode.
Abstract: The present paper tries to contribute to quantifying the relationship between the amount of corrosion and cover cracking. The variables studied were: cover/diameter (c/o), proportions of cement, w/c, cast position of the bar, transverse reinforcement and corrosion rate. The corrosion is accelerated by applying constant currents causing the rebar to act as an anode. The results indicate that the cracking process develops in two steps: generation and propagation. Radius losses of about 15–50 μm are necessary to generate the first visible crack (<0.1 mm width). The propagation follows a behaviour of the type: w (crack width in mm)=a+bx (radius loss in μm).
Journal Article•
TL;DR: The results suggest that the Melan-A(26-35) peptide analogue ELAGIGILTV may be more immunogenic than the natural peptides in HLA-A*0201 melanoma patients and should thus be considered as a candidate for future peptide-based vaccine trials.
Abstract: The Melan-A/MART-1 gene, which is expressed by normal melanocytes as well as by most fresh melanoma samples and melanoma cell lines, codes for Ags recognized by tumor-reactive CTL. HLA-A*0201-restricted Melan-A-specific CTL recognize primarily the Melan-A27-35 (AAGIGILTV) and the Melan-A26-35 (EAAGIGILTV) peptides. The sequences of these two peptides are not necessarily optimal as far as binding to HLA-A*0201 is concerned, since both lack one of the dominant anchor amino acid residues (leucine or methionine) at position 2. In this study we introduced single amino acid substitutions in either one of the two natural peptide sequences with the aim of improving peptide binding to HLA-A*0201 and/or recognition by specific CTL. Surprisingly, analogues of the Melan-A27-35 peptide, which bound more efficiently than the natural nonapeptide to HLA-A*0201, were poorly recognized by tumor-reactive CTL. In contrast, among the Melan-A26-35 peptide analogues tested, the peptide ELAGIGILTV was not only able to display stable binding to HLA-A2.1 but was also recognized more efficiently than the natural peptide by two short-term cultured tumor-infiltrated lymph node cell cultures as well as by five of five tumor-reactive CTL clones. Moreover, in vitro generation of tumor-reactive CTL by stimulation of PBMC from HLA-A*0201 melanoma patients with this particular peptide analogue was much more efficient than that observed with either one of the two natural peptides. These results suggest that the Melan-A26-35 peptide analogue ELAGIGILTV may be more immunogenic than the natural peptides in HLA-A*0201 melanoma patients and should thus be considered as a candidate for future peptide-based vaccine trials.
TL;DR: These results suggest that lipases recognize these "well-defined" hydrophobic supports as solid interfaces and they become adsorbed through the external areas of the largeHydrophobic active centers of their "open and hyperactivated structure", which becomes a very promising immobilization method with general application for most lipases.
Abstract: A number of bacterial lipases can be immobilized in a rapid and strong fashion on octyl-agarose gels (e.g., lipases from Candida antarctica, Pseudomonas fluorescens, Rhizomucor miehei, Humicola lanuginosa, Mucor javanicus, and Rhizopus niveus). Adsorption rates in absence of ammonium sulfate are higher than in its presence, opposite to the observation for typical hydrophobic adsorption of proteins. At 10 mM phosphate, adsorption of lipases is fairly selective allowing enzyme purification associated with their reversible immobilization. Interestingly, these immobilized lipase molecules show a dramatic hyperactivation. For example, lipases from R. niveus, M. miehei, and H. lanuginosa were 6-, 7-, and 20-fold more active than the corresponding soluble enzymes when catalyzing the hydrolysis of a fully soluble substrate (0.4 mM p-nitrophenyl propionate). Even higher hyperactivations and interesting changes in stereospecificity were also observed for the hydrolysis of larger soluble chiral esters (e.g. (R,S)-2-hydroxy-4-phenylbutanoic ethyl ester). These results suggest that lipases recognize these "well-defined" hydrophobic supports as solid interfaces and they become adsorbed through the external areas of the large hydrophobic active centers of their "open and hyperactivated structure". This selective interfacial adsorption of lipases becomes a very promising immobilization method with general application for most lipases. Through this method, we are able to combine, via a single and easily performed adsorption step, the purification, the strong immobilization, and a dramatic hyperactivation of lipases acting in the absence of additional interfaces, (e.g., in aqueous medium with soluble substrate). Copyright 1998 John Wiley & Sons, Inc.
TL;DR: In this paper, the authors define the hydrogen bond as an attractive interaction between two molecular moieties in which at least one of them contains a hydrogen atom that plays a fundamental role.
Abstract: Hydrogen bonds (HBs) are the most important ‘weak’ interactions encountered in solid, liquid and gas phases. The HB can be defined as an attractive interaction between two molecular moieties in which at least one of them contains a hydrogen atom that plays a fundamental role. Classical HBs correspond to those formed by two heteroatoms, A and B, with a hydrogen atom bonded to one of them and located approximately in between (A–H···B). Recently, knowledge of the number of functional groups which act as hydrogen bond donors or acceptors has increased considerably and most of these new groups are discussed.
TL;DR: Different approaches for lipase immobilization mainly related to the further use of immobilized derivatives to carry out enantio and regioselective hydrolysis in high water-activity systems are reviewed.
TL;DR: In this article, the authors present an experimental analysis of the acoustic transmission of a two-dimensional periodic array of rigid cylinders in air with two different geometrical configurations: square and triangular.
Abstract: In this Letter we present an experimental analysis of the acoustic transmission of a two-dimensional periodic array of rigid cylinders in air with two different geometrical configurations: square and triangular. In both configurations, and above a certain filling fraction, we observe an overlap, in the range of the audible frequencies, between the attenuation peaks measured along the two high-symmetry directions of the Brillouin zone. This effect is considered as the fingerprint of the existence of a full acoustic gap. Nevertheless, the comparison with our calculation of band structures shows that the triangular lattice has band states in that frequency range. We call them deaf bands. This contradictory result is explained by looking at the symmetry of the deaf bands; they cannot be excited by experiments of sound transmission. [S0031-9007(98)06295-4]
TL;DR: It is suggested that BRM participates in the regulation of cell proliferation in adult mice, supported by the observation that mutant embryonic fibroblasts were significantly deficient in their ability to arrest in the G0/G1 phase of the cell cycle in response to cell confluency or DNA damage.
Abstract: The mammalian SWI–SNF complex is an evolutionarily conserved, multi‐subunit machine, involved in chromatin remodelling during transcriptional activation. Within this complex, the BRM (SNF2α) and BRG1 (SNF2β) proteins are mutually exclusive subunits that are believed to affect nucleosomal structures using the energy of ATP hydrolysis. In order to characterize possible differences in the function of BRM and BRG1, and to gain further insights into the role of BRM‐containing SWI–SNF complexes, the mouse BRM gene was inactivated by homologous recombination. BRM −/− mice develop normally, suggesting that an observed up‐regulation of the BRG1 protein can functionally replace BRM in the SWI–SNF complexes of mutant cells. Nonetheless, adult mutant mice were ∼15% heavier than control littermates. This may be caused by increased cell proliferation, as demonstrated by a higher mitotic index detected in mutant livers. This is supported further by the observation that mutant embryonic fibroblasts were significantly deficient in their ability to arrest in the G 0 /G 1 phase of the cell cycle in response to cell confluency or DNA damage. These studies suggest that BRM participates in the regulation of cell proliferation in adult mice.