Showing papers by "University of Oviedo published in 1999"

Linear-scaling ab-initio calculations for large and complex systems

Abstract: A brief review of the Siesta project is presented in the context of linear-scaling density-functional methods for electronic-structure calculations and molecular-dynamics simulations of systems with a large number of atoms. Applications of the method to different systems are reviewed, including carbon nanotubes, gold nanostructures, adsorbates on silicon surfaces, and nucleic acids. Also, progress in atomic-orbital bases adapted to linear-scaling methodology is presented.

Ab initio structural, elastic, and vibrational properties of carbon nanotubes

Abstract: A study based on ab initio calculations is presented on the structural, elastic, and vibrational properties of single-wall carbon nanotubes with different radii and chiralities. These properties are obtained using an implementation of pseudopotential-density-functional theory, which allows calculations on systems with a large number of atoms per cell. Different quantities are monitored versus tube radius. The validity of expectations based on graphite is explored down to small radii, where some deviations appear related to the curvature-induced rehybridization of the carbon orbitals. Young moduli are found to be very similar to graphite and do not exhibit a systematic variation with either the radius or the chirality. The Poisson ratio also retains graphitic values except for a possible slight reduction for small radii. It shows, however, chirality dependence. The behavior of characteristic phonon branches as the breathing mode, twistons, and high-frequency optic modes, is also studied, the latter displaying a small chirality dependence at the top of the band. The results are compared with the predictions of the simple zone-folding approximation. Except for the known deficiencies of the zone-folding procedure in the low-frequency vibrational regions, it offers quite accurate results, even for relatively small radii.

Regulation of Mammalian Circadian Behavior by Non-rod, Non-cone, Ocular Photoreceptors

Abstract: Circadian rhythms of mammals are entrained by light to follow the daily solar cycle (photoentrainment). To determine whether retinal rods and cones are required for this response, the effects of light on the regulation of circadian wheel-running behavior were examined in mice lacking these photoreceptors. Mice without cones (cl) or without both rods and cones (rdta/cl) showed unattenuated phase-shifting responses to light. Removal of the eyes abolishes this behavior. Thus, neither rods nor cones are required for photoentrainment, and the murine eye contains additional photoreceptors that regulate the circadian clock.

Mutations in the gene encoding B1 subunit of H+-ATPase cause renal tubular acidosis with sensorineural deafness

Abstract: H+-ATPases are ubiquitous in nature; V-ATPases pump protons against an electrochemical gradient, whereas F-ATPases reverse the process, synthesizing ATP. We demonstrate here that mutations in ATP6B1, encoding the B-subunit of the apical proton pump mediating distal nephron acid secretion, cause distal renal tubular acidosis, a condition characterized by impaired renal acid secretion resulting in metabolic acidosis. Patients with ATP6B1 mutations also have sensorineural hearing loss; consistent with this finding, we demonstrate expression of ATP6B1 in cochlea and endolymphatic sac. Our data, together with the known requirement for active proton secretion to maintain proper endolymph pH, implicate ATP6B1 in endolymph pH homeostasis and in normal auditory function. ATP6B1 is the first member of the H+-ATPase gene family in which mutations are shown to cause human disease.

Regulation of the mammalian pineal by non-rod, non-cone, ocular photoreceptors.

Abstract: In mammals, ocular photoreceptors mediate an acute inhibition of pineal melatonin by light. The effect of rod and cone loss on this response was assessed by combining the rd mutation with a transgenic ablation of cones (cl) to produce mice lacking both photoreceptor classes. Despite the loss of all known retinal photoreceptors, rd/rd cl mice showed normal suppression of pineal melatonin in response to monochromatic light of wavelength 509 nanometers. These data indicate that mammals have additional ocular photoreceptors that they use in the regulation of temporal physiology.

Collagenase 3 is a target of Cbfa1, a transcription factor of the runt gene family involved in bone formation.

Abstract: The human matrix metalloproteinases (MMPs) or matrixins are a family of structurally related neutral proteinases that are collectively capable of degrading essentially all extracellular matrix components (9). These enzymes play a major role in normal tissue-remodeling processes such as embryonic development, ovulation, and wound healing (44, 81). In addition, abnormal expression of these proteases may contribute to a variety of pathological conditions characterized by matrix destruction, including rheumatoid arthritis (52), atherosclerosis (25), and cancer invasion and metastasis (43, 72). Recently, and based on the hypothesis that samples of human tumor specimens could be an appropriate material to identify novel proteinases potentially involved in the spread of cancer, we have cloned from a breast carcinoma cDNA library a new member of the MMP family of enzymes that has been called collagenase 3 (MMP-13) (21, 55). Biochemical characterization of this enzyme has revealed that it degrades very efficiently the native helix of fibrillar collagens, with preferential activity on type II collagen. In addition, collagenase 3 may also act as a potent gelatinase, thus contributing to further degrade the initial cleavage products of collagenolysis to small fragments suitable for subsequent metabolism (33). Furthermore, recent studies have shown that collagenase 3 is also able to degrade the large cartilage proteoglycan aggrecan and other components of the extracellular matrix and basement membranes, including type IV collagen (19, 33, 35). Analysis of the expression of collagenase 3 in human tissues has revealed that in addition to its presence in diverse malignant tumors including breast carcinomas (21, 26), chondrosarcomas (77), basal cell carcinomas of the skin (1), and head and neck carcinomas (13, 29), this enzyme is produced during fetal ossification (30, 70) and in destructive joint diseases such as osteoarthritis and rheumatoid arthritis (41, 49, 59). Recent studies have provided information on the mechanisms controlling human collagenase 3 expression in pathological conditions. Thus, we have reported that this gene is predominantly expressed in fibroblasts adjacent to invasive breast cancer cells, in response to diffusible factors released from the epithelial tumor cells (76). A search of molecular factors with ability to induce collagenase 3 expression in human fibroblasts has shown that interleukin-1 (IL-1), tetradecanoyl phorbol acetate (TPA), and transforming growth factor β (TGF-β) are able to up-regulate the expression of this gene (76, 78). Functional analysis of the collagenase 3 gene promoter region has revealed that the inductive effects of all of these factors on the expression of collagenase 3 are mediated in part by an AP-1 site present in the 5′-flanking region of this gene (56, 78). Similar studies using human chondrosarcoma cells have indicated that basic fibroblast growth factor (bFGF) may be a major in vivo modulator of collagenase 3 expression in these malignant tumors (77). Furthermore, different groups have reported that IL-1β and tumor necrosis factor alpha (TNF-α) may induce collagenase 3 expression in osteoarthritic cartilage (11, 59). However, in marked contrast to these data on human collagenase 3 expression in pathological conditions, very little information is available on the mechanisms mediating its expression in normal conditions and, more specifically, in the process of bone formation, in which high levels of collagenase 3 have been detected. Recent structural analysis of the 5′-flanking region of the human collagenase 3 gene (56) has shown that it contains a sequence motif located at positions −133 to −139 that exhibits striking similarity to a sequence motif called nuclear matrix protein 2 (NMP-2) binding site (8, 47) or osteoblast-specific element 2 (OSE2) (15, 17). This sequence, originally described as a structural element essential for the osteoblastic expression of osteocalcin, is recognized by a transcription factor of the runt domain gene family, called Cbfa1 or Osf2 (7, 15, 17, 69, 83), that plays a major role in the expression of different osteoblast-specific genes (6, 7, 17, 37, 53). In this work we have evaluated the possibility that Cbfa1 is involved in the expression of collagenase 3 during bone formation. It was recently reported that parathyroid hormone (PTH) regulates the rat collagenase 3 promoter in osteoblastic cells through the cooperative interaction of an AP-1 site and a runt domain binding sequence recognized by runt domain proteins including Cbfa1 (67). Here, we provide in vitro and in vivo evidence that collagenase 3 is a target of Cbfa1 in osteoblastic and chondrocytic cells. In addition, on the basis of these transcriptional regulation studies, together with the potent proteolytic activity of collagenase 3 on bone and cartilage collagens, we propose that this enzyme may play a key role during fetal ossification.

Finding the missing link between landscape structure and population dynamics: a spatially explicit perspective

Abstract: We construct and explore a general modeling framework that allows for a systematic investigation of the impact of changes in landscape structure on population dynamics. The essential parts of the framework are a landscape generator with independent control over landscape composition and physiognomy, an individual‐based spatially explicit population model that simulates population dynamics within heterogeneous landscapes, and scale‐dependent landscape indices that depict the essential aspects of landscape that interact with dispersal and demographic processes. Landscape maps are represented by a grid of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} ewcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} ormalfo...

Identification and Characterization of Human MT5-MMP, a New Membrane-bound Activator of Progelatinase A Overexpressed in Brain Tumors

Abstract: A cDNA encoding a new member of the membrane-type (MT) matrix metalloproteinase (MMP) family has been identified and cloned from a human brain cDNA library. The isolated cDNA encodes a polypeptide of 645 amino acids that displays a similar domain organization as other MMPs, including a predomain with the activation locus, a zinc-binding site, and a hemopexin domain. The deduced amino acid sequence contains a COOH-terminal extension, rich in hydrophobic residues and similar in size to the equivalent domains identified in MT-MMPs. Immunofluorescence and Western blot analysis of COS-7 cells transfected with the isolated cDNA revealed that the encoded protein is localized in the plasma membrane. On the basis of these features, this novel human MMP has been called MT5-MMP because it represents the fifth member of the MT-MMP subfamily of MMPs. Fluorescent in situ hybridization experiments showed that the human MT5-MMP gene (MMP-24) maps to 20q11.2, a region frequently amplified in tumors from diverse sources. Northern blot analysis demonstrated that MT5-MMP is predominantly expressed in brain, kidney, pancreas, and lung. In addition, MT5-MMP transcripts were detected at high levels compared to normal brain tissue in a series of brain tumors, including astrocytomas and glioblastomas. The catalytic domain of MT5-MMP, produced in Escherichia coli as a fusion protein with glutathione S-transferase, exhibits a potent proteolytic activity against progelatinase A, leading to the generation of the Mr 62,000 active form of this enzyme. These data suggest that MT5-MMP may contribute to the activation of progelatinase A in tumor tissues, in which it is overexpressed, thereby facilitating tumor progression.

Naming times for the Snodgrass and Vanderwart pictures in Spanish.

Abstract: We present new Spanish norms for object familiarity and rated age of acquisition for 140 pictures taken from Snodgrass and Vanderwart (1980), together with data on visual complexity, image agreement, name agreement, word length (in syllables and phonemes), and five measures of word frequency. The pictures were presented to a group of 64 Spanish subjects, and oral naming latencies were recorded. In a multiple regression analysis, age of acquisition, object familiarity, name agreement, word frequency, and word length made significant independent contributions to predicting naming latency.

Origin of peraluminous granites and granodiorites, Iberian massif, Spain: an experimental test of granite petrogenesis

Abstract: The discrimination between potential source materials involved in the genesis of Iberian granites and granodiorites, as well as the role of mantle-crust inter- actions, are examined using constraints imposed by melting experiments, melting-assimilation experiments and Sr-Nd isotope systematics. The Sr-Nd isotope re- lationships indicate the existence of diAerent genetic trends in which juvenile mantle materials are involved by diAerent mechanisms: (1) a source trend, traced by a particular evolution of the pre-Hercynian basement and indicating mantle participation at the time of sedimen- tation; (2) a set of magmatic trends traced by gabbro- tonalite-enclave-granodiorite associations, implying the incorporation of new mantle material at the time of granite generation. These relationships strongly support a pure crustal origin for the peraluminous leucogranites, derived from partial melting of crustal protoliths, and a hybrid origin for the peraluminous granodiorites. These granodiorites are the most abundant granitic rocks of the Central Iberian zone (CIZ) of the Iberian massif, implying that processes of hybridisation by assimilation and/or magma mixing played an important role in granitoid production during the Hercynian orogeny. These hypotheses have been tested by means of melting and assimilation experiments. Melting experiments in the range 800-900 ∞C and at pressures of 3, 6, 10 and 15 kbar indicate that: (1) several potential source materials such as Bt-Ms gneisses and metagreywackes are suitable for the production of peraluminous leucogranite melts; (2) the melt compositions are always leucogranitic, re- gardless of pressure; (3) pressure exerts a strong influ- ence on the fertility of the source: experiments at 3 kbar produce more than 20 vol% of melt, compared with less than 5 vol% of melt produced at 10 and 15 kbar and at the same temperature. The melting-assimilation experi- ments carried out at 1000 ∞C and 4, 7 and 10 kbar and using a proportion of 50% gabbro and 50% gneiss give high melt proportions (more than 50 vol.%) and noritic residues. These melts have the composition of le- ucogranodiorites, and overlap with part of the compo- sitional range of peraluminous granodiorites of the Iberian massif. The generation of more mafic granodiorites may be explained by the incorporation of some residual orthopyroxene to the granodiorite mag- mas. The low solubility of Fe + Mg prevents the gen- eration of granodiorite melts with more than 3 wt% of MgO + FeO at all crustal pressures. The large volumes of peraluminous, hybrid granodiorites, produced by assimilation of crustal rocks by mantle magmas, imply that an important episode of crustal growth took place during the Late-Palaeozoic Hercynian orogeny in the Iberian massif.

Treatment of multiple adjacent gingival recessions with the tunnel subepithelial connective tissue graft: a clinical report.

Abstract: This article describes a surgical periodontal plastic procedure for the coverage of multiple adjacent gingival recessions. This surgical technique is based on the construction of a tunnel under the gingival tissue by means of a sulcular incision beyond the mucogingival line without raising the papillae. A large connective tissue graft obtained from the palatal mucosa is introduced through this tunnel, covering the adjacent gingival recessions. A suturing technique to allow this graft to slip through the tunnel under the gingival tissues and to secure and stabilize the graft covering the recessions is described. Twelve-month postoperative results are presented from 21 teeth that were treated with this technique: 100% root coverage was achieved in 66.7% of the recessions treated, with a mean root surface coverage of 91.6%. This study suggests that the use of this surgical procedure allows the treatment of multiple adjacent recessions in a single procedure with adequate early healing and highly predictable root coverage results.

Purification and characterization of an extracellular protease from the fish pathogen Yersinia ruckeri and effect of culture conditions on production.

Abstract: A novel protease, hydrolyzing azocasein, was identified, purified, and characterized from the culture supernatant of the fish pathogen Yersinia ruckeri. Exoprotease production was detected at the end of the exponential growth phase and was temperature dependent. Activity was detected in peptone but not in Casamino Acid medium. Its synthesis appeared to be under catabolite repression and ammonium control. The protease was purified in a simple two-step procedure involving ammonium sulfate precipitation and ion-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the purified protein indicated an estimated molecular mass of 47 kDa. The protease had characteristics of a cold-adapted protein, i.e., it was more active in the range of 25 to 42°C and had an optimum activity at 37°C. The activation energy for the hydrolysis of azocasein was determined to be 15.53 kcal/mol, and the enzyme showed a rapid decrease in activity at 42°C. The enzyme had an optimum pH of around 8. Characterization of the protease showed that it required certain cations such as Mg2+ or Ca2+ for maximal activity and was inhibited by EDTA, 1,10-phenanthroline, and EGTA but not by phenylmethylsulfonyl fluoride. Two N-methyl-N-nitro-N-nitrosoguanidine mutants were isolated and analyzed; one did not show caseinolytic activity and lacked the 47-kDa protein, while the other was hyperproteolytic and produced increased amounts of the 47-kDa protein. Azocasein activity, SDS-PAGE, immunoblotting by using polyclonal anti-47-kDa-protease serum, and zymogram analyses showed that protease activity was present in 8 of 14 strains tested and that two Y. ruckeri groups could be established based on the presence or absence of the 47-kDa protease.

Immunization with Potato Plants Expressing VP60 Protein Protects against Rabbit Hemorrhagic Disease Virus

Abstract: The major structural protein VP60 of rabbit hemorrhagic disease virus (RHDV) has been produced in transgenic potato plants under the control of a cauliflower mosaic virus 35S promoter or a modified 35S promoter that included two copies of a strong transcriptional enhancer. Both types of promoters allowed the production of specific mRNAs and detectable levels of recombinant VP60, which were higher for the constructs carrying the modified 35S promoter. Rabbits immunized with leaf extracts from plants carrying this modified 35S promoter showed high anti-VP60 antibody titers and were fully protected against the hemorrhagic disease.

Knowledge management in agile innovative organisations

Abstract: Technology and innovation processes are formed by knowledge bases and continuous flows of information. Their intangibility and the actual trend to support the competitiveness of the firm in the synergetic relations of its intangible assets have led to a new form of analysis of the technological innovation processes. Technology management also requires assuming new activities to manage effectively the flow of information and the knowledge reservoirs which are necessary to provide a quick answer to the uncertainty and dynamism of technological evolution. The firm should also create knowledge milieus, common shared environments or bas and a clear knowledge culture. In this paper, we review the importance of the knowledge consideration of technology and its incidence on the innovation process, and then we analyse which are the main charactersitics of knowledge management and how it should be put into practice in the innovating firm, where knowledge managers are an essential component.

Electronic states in a finite carbon nanotube : a one-dimensional quantum box

Abstract: The theoretical scanning-tunneling-spectroscopy image catalog of quantized molecular orbitals of finite armchair carbon nanotubes deposited on a gold (111) surface is presented. Just four different three-dimensional standing-wave (SW) patterns are obtained for electrons close to the Fermi level. The experimental observations of a SW modulation of 0.74 nm and peak pairing in line scans are understood in sight of our results. We show that SW patterns can be explained in terms of the simple H\"uckel model, but the associated energies, relevant to spectroscopic and transport measurements, are very sensitive to different effects beyond that model including the relaxed geometry, the electronic self-consistency in the finite tubes, and the interaction with the substrate.

On-line timetable re-scheduling in regional train services

Abstract: In the daily activity of regional railway traffic, when the circulation frequencies are high, any anomaly that alters the scheduled circulation of trains may distort any of all of the established timetables and involve re-scheduling many of services, due to the numerous possible alternatives for resolving the situation. An on-line model is presented in this article which helps in choosing the most appropriate solution based on an intelligent exploration of the solutions space. The tool has been implemented in the Spanish national railways company.

Melatonin blocks the activation of estrogen receptor for DNA binding

Abstract: The present study shows that melatonin prevents, within the first cell cycle, the estradiol-induced growth of synchronized MCF7 breast cancer cells. By using nuclear extracts of these cells, we first examined the binding of estradiol–estrogen receptor complexes to estrogen-responsive elements and found that the addition of estradiol to whole cells activates the binding of the estrogen receptor to DNA whereas melatonin blocks this interaction. By contrast, melatonin neither affects the binding of estradiol to its receptor nor the receptor nuclear localization. Moreover, we also show that addition of estradiol to nuclear extracts stimulates the binding of estrogen receptor to DNA, but this activation is also prevented by melatonin. The inhibitory effect caused by melatonin is saturable at nanomolar concentrations and does not appear to be mediated by RZR nuclear receptors. The effect is also specific, since indol derivatives do not cause significant inhibition. Furthermore, we provide evidence that melatoni...

[Validation of the Spanish version of the Liebowitz social anxiety scale, social anxiety and distress scale and Sheehan disability inventory for the evaluation of social phobia].

Abstract: Fundamento: La fobia social es un trastorno de ansiedad de creciente interes en la clinica e investigacion psiquiatricas. Los cuestionarios de mayor difusion en la evaluacion psicometrica de estos pacientes son: Liebowitz Social Anxiety Scale (LSAS), Social Anxiety and Distress Scale (SADS) y Sheehan Disability Inventory (SDI). El objetivo del presente estudio fue evaluar la validez y reproducibilidad de las versiones

Examples of Independence for Imprecise Probabilities

Abstract: In this paper we try to clarify the notion of independence for imprecise probabilities. Our main point is that there are several possible definitions of independence which are applicable in different types of situation. With this aim, simple examples are given in order to clarify the meaning of the different concepts of independence and the relation- ships between them.