Showing papers by "University of Oviedo published in 2001"

The effects of brand associations on consumer response

Abstract: This paper studies the dimensions of brand image, focusing on the functions or value of the brand as perceived by consumers. In this way, four categories of functions are identified: guarantee, personal identification, social identification and status. By way of hypotheses, it has been proposed that these functions have a positive influence on the consumer’s willingness to recommend the brand, pay a price premium for it and accept brand extensions. The hypotheses have been tested in the Spanish sports shoes market and were partially supported. The results obtained confirm the convenience of analyzing brand associations separately and enable the ascertaining of the brand associations that are the most relevant in order to attain certain consumer responses.

Atomistic simulation of Sr F 2 polymorphs

Abstract: Electron gas interionic potentials (EGIP) have been developed to determine the equation of state (EOS) of the cubic (C1) and orthorhombic (C23) polymorphs of ${\mathrm{SrF}}_{2},$ including the thermal effects by means of a quasiharmonic Debye model. The zero pressure cell parameter ${(a}_{0}),$ lattice energy ${(E}_{\mathrm{latt}}),$ and bulk modulus ${(B}_{0})$ of the C1 phase are computed with errors smaller than 1.2%, 1.2%, and 7.1%, respectively. The predicted EOS is in good agreement with the observed data and satisfies the universal Vinet EOS. For the C23 phase, the optimized zero-$p$ cell parameters a, b, and c and the six fractional coordinates are reported and the pressure dependence of ${a/a}_{0},$ ${b/b}_{0},$ and ${c/c}_{0}$ explored by fitting independent modified Vinet EOS's to the computed data. The analysis reveals a greater compressibility of the C23 phase along the b and c axes than along the a direction. Our calculation predicts the $\mathrm{C}1\ensuremath{\rightleftharpoons}\mathrm{C}23$ equilibrium to occur at ${p}_{\mathrm{tr}}=3.92$ GPa, which is between the observed values for the $\mathrm{C}\stackrel{\ensuremath{\rightarrow}}{1}\mathrm{C}23$ ${(p}_{\mathrm{tr}}=5.0$ GPa) and $\mathrm{C}23\ensuremath{\rightarrow}\mathrm{C}1$ ${(p}_{\mathrm{tr}}=1.7$ GPa) phase transitions.

Bioremediation of diesel-contaminated soils: Evaluation of potential in situ techniques by study of bacterial degradation

Abstract: The development of a simple laboratory methodology allows theimplementation of in situbioremediation of polluted soils with diesel fuel. In thisinvestigation microbiological and chemical analyses and a suitable bioreactor design, were veryuseful for suggesting the best ways to improve biodegradation extents in a diesel-enrichedsoil. Biostimulation with inorganic nitrogen and phosphorus produced the best resultsin a simple bioreactor, with biodegradation extents higher than 90% after 45 days. Also,the addition of activated sludge from a domestic wastewater plant increased the degradationrate to a great extent. In both cases, microbiological studies showed the presence ofAcinetobacter sp. degrading most of thehydrocarbons. Simultaneously, a diesel fuel release(approximately 400,000 l) was studied. Samples taken in polluted soil and water revealed thatbacteria from the genus Acinetobacterwere predominant. In plate studies, Acinetobacter coloniesproduced a whitish substance with the characteristics of a biosurfactant. Remarkably, thepresence of this product was evident at the field site, both in the riverbanks and in the physicalrecovery plant. The study of the similarities between laboratory results and the diesel spillsite strongly suggested that natural conditions at the field site allowed the implementationof in situ bioremediation after physical removal of LNAPL (light nonaqueous-phase liquids).

The hexokinase 2 protein regulates the expression of the GLK1, HXK1 and HXK2 genes of Saccharomyces cerevisiae.

Abstract: The key glycolytic HXK2 gene, coding for the enzyme hexokinase 2 (Hxk2p), is expressed when cells of the yeast Saccharomyces cerevisiae are grown on a fermentable medium using glucose, fructose or mannose as a carbon source. After shifting the cells to a non-fermentable carbon source, the HXK2 gene is repressed and the HXK1 and GLK1 genes are rapidly de-repressed, producing the enzymes hexokinase 1 (Hxk1p) and glucokinase (Glk1p) respectively. Because the in vivo functions of the Hxk1p and Glk1p enzymes have remained a mystery so far, we have investigated this glucose-induced regulatory process. Here we demonstrate the involvement of Hxk2p in the glucose-induced repression of the HXK1 and GLK1 genes and the glucose-induced expression of the HXK2 gene. We have also demonstrated the involvement of Hxk1p as a negative factor in the expression of the GLK1 and HXK2 genes. Further experimental evidence, using mutant cells expressing a truncated version of Hxk2p unable to enter the nucleus, shows that nuclear localization of Hxk2p is necessary for glucose-induced repression signalling of the HXK1 and GLK1 genes and for glucose-induced expression of the HXK2 gene. Gel mobility-shift analysis shows that Hxk2p-mediated regulation is exerted through ERA (ethanol repression autoregulation)-like regulatory sequences present in the HXK1 and GLK1 promoters and in two downstream repressing sequences of the HXK2 gene. These findings reveal a novel mechanism of gene regulation whereby the product of a glycolytic gene, normally resident in the cytosol, interacts directly with nuclear proteins to regulate the transcription of the HXK1 and GLK1 genes and to autoregulate its own transcription.

Genetic diversity measures of local European beef cattle breeds for conservation purposes

Abstract: This study was undertaken to determine the genetic structure, evolutionary relationships, and the genetic diversity among 18 local cattle breeds from Spain, Portugal, and France using 16 microsatellites. Heterozygosities, estimates of Fst, genetic distances, multivariate and diversity analyses, and assignment tests were performed. Heterozygosities ranged from 0.54 in the Pirenaica breed to 0.72 in the Barrosa breed. Seven percent of the total genetic variability can be attributed to differences among breeds (mean Fst = 0.07; P < 0.01). Five different genetic distances were computed and compared with no correlation found to be significantly different from 0 between distances based on the effective size of the population and those which use the size of the alleles. The Weitzman recursive approach and a multivariate analysis were used to measure the contribution of the breeds diversity. The Weitzman approach suggests that the most important breeds to be preserved are those grouped into two clusters: the cluster formed by the Mirandesa and Alistana breeds and that of the Sayaguesa and Tudanca breeds. The hypothetical extinction of one of those clusters represents a 17% loss of diversity. A correspondence analysis not only distinguished four breed groups but also confirmed results of previous studies classifying the important breeds contributing to diversity. In addition, the variation between breeds was sufficiently high so as to allow individuals to be assigned to their breed of origin with a probability of 99% for simulated samples.

Comparison of procalcitonin with C-reactive protein and serum amyloid for the early diagnosis of bacterial sepsis in critically ill neonates and children.

Abstract: Objectives: To evaluate procalcitonin (PCT) as a diagnostic marker of bacterial sepsis in critically ill neonates and children and to compare the results of PCT with those of C-reactive protein (CRP) and serum amyloid (SAA). Design and setting: Prospective, observational study in neonatal and pediatric intensive care units. Patients: A total of 116 divided into four groups according to age and diagnosis: neonates (aged 3–30 days) with sepsis (n=20), neonates without sepsis (n=26), children (aged 2–12 years) with sepsis (n=32), and children without sepsis (n=38). Interventions: Serum PCT, CRP, and SAA were measured on admission or when a bacterial sepsis was suspected. Area under the receiver operating characteristic (ROC) curve, optimum predictive values, and optimum diagnostic cut off values were evaluated. Results: Admission PCT was significantly higher in neonates and children with sepsis than in the other groups. In the neonates the area under the ROC curve was 0.99 for PCT, 0.95 for CRP, and 0.98 for SAA; in the children it was 1 for PCT, 0.93 for CRP, and 0.96 for SAA. Cutoff concentrations for optimum prediction of sepsis in the neonates were PCT >6.1 ng/ml (diagnostic efficiency: 93.8%), CRP >23.0 mg/l (89.7%), and SAA >41.3 mg/l (95.3%); in the children they were PCT>8.1 ng/ml (100%), CRP>22.1 mg/l (89.8%), and SAA>67.2 mg/l (94.4%). Conclusion: In critically ill children PCT concentration is a better diagnostic marker of sepsis than CRP and SAA. In critically ill neonates, however, PCT, CRP, and SAA are similar diagnostic markers of sepsis. A PCT concentration higher than 8.1 ng/ml identified all children with bacterial sepsis.

Multidrug resistance is mediated by large plasmids carrying a class 1 integron in the emergent Salmonella enterica serotype [4,5,12:i:-].

Abstract: A multidrug-resistant Salmonella enterica serotype [4,5,12:i:-] clone carried a class 1 integron harboring dfrA12 and aadA2 gene cassettes and bla(TEM-1), aac(3)-IV, cmlA1, and tetA genes located in large plasmids of about 140 kb (carrying spv) or 120 kb (lacking spv). Several segregants, lacking multidrug resistance, contained a plasmid smaller than the parental one and no longer hybridized with probes for the lost resistances. The genes mediating resistance to ampicillin, chloramphenicol, and tetracycline in the [4,5,12:i:-] clone are different from those found in the pentadrug-resistant serotype Typhimurium DT104 clone.

Nuclear factor κB is a critical determinant in N-methyl-D-aspartate receptor-mediated neuroprotection

Abstract: The role of a nuclear factor kappaB (NF-kappaB) in NMDA receptor-mediated neuroprotection is not known. A candidate sequence from the 5' flanking region of exon 3 of the rat brain-derived neurotrophic factor (BDNF) gene was used to show that exposure of rat cerebellar granule cells to 100 microM NMDA activated a specific DNA binding activity that was blocked by the NMDA receptor antagonist MK-801. Anti-p65 antibody or anti-p50 antibody 'supershifted' the DNA binding activity, suggesting that the DNA-protein complex was composed of p65 and p50 subunits. NMDA receptor-mediated neuroprotection was blocked when cerebellar neurons were transfected with a double-stranded oligonucleotide containing the BDNF gene NF-kappaB sequence. Furthermore, nuclear extracts prepared from neurons treated with NMDA and the double-stranded NF-kappaB oligonucleotide showed reduced DNA binding activity to the target sequence, supporting the idea that NF-kappaB may be involved in the transcriptional activation of the BDNF gene. To address this issue, we quantified the level of exon 3-specific BDNF mRNA. Relative to GAPDH mRNA levels and compared with untreated neurons, NMDA increased exon 3-specific BDNF mRNA twofold. In contrast, pretreatment of neurons with the NF-kappaB target DNA abolished the increase in BDNF mRNA following addition of NMDA. We also determined that BDNF itself induced an NF-kappaB DNA binding activity. Taken together, these data support a mechanism where NF-kappaB plays a critical role in NMDA-mediated neuroprotection.

Recent Developments in the Reactivity of Allenylidene and Cumulenylidene Complexes

Abstract: Allenylidene and higher cumulenylidene complexes [M]=C(=C)n=CR1R2 (n = 1, 2, 3) have continuously gained significance in the context of transition metal carbene chemistry. Important developments which have been disclosed during the last two years are reviewed. These include a variety of stoichiometric and catalytic reactions of allenylidene complexes and their utility in organic synthesis. The related chemistry of butatrienylidene (n = 2) and pentatetraenylidene (n = 3) complexes as well as theoretical studies are also reviewed.

Purification and characterization of a psychrophilic, calcium-induced, growth-phase-dependent metalloprotease from the fish pathogen Flavobacterium psychrophilum.

Abstract: Flavobacterium psychrophilum is a fish pathogen that commonly affects salmonids. This bacterium produced an extracellular protease with an estimated molecular mass of 55 kDa. This enzyme, designated Fpp1 (F. psychrophilum protease 1), was purified to electrophoretic homogeneity from the culture supernatant by using ammonium sulfate precipitation, ion-exchange chromatography, hydrophobic chromatography, and size exclusion chromatography. On the basis of its biochemical characteristics, Fpp1 can be included in the group of metalloproteases that have an optimum pH for activity of 6.5 and are inhibited by 1,10-phenanthroline, EDTA, or EGTA but not by phenylmethylsulfonyl fluoride. Fpp1 activity was dependent on calcium ions not only for its activity but also for its thermal stability. In addition to calcium, strontium and barium can activate the protein. The enzyme showed typical psychrophilic behavior; it had an activation energy of 5.58 kcal/mol and was more active at temperatures between 25 and 40 degrees C, and its activity decreased rapidly at 45 degrees C. Fpp1 cleaved gelatin, laminin, fibronectin, fibrinogen, collagen type IV, and, to a lesser extent, collagen types I and II. Fpp1 also degraded actin and myosin, basic elements of the fish muscular system. The presence of this enzyme in culture media was specifically dependent on the calcium concentration. Fpp1 production started early in the exponential growth phase and reached a maximum during this period. Addition of calcium during the stationary phase did not induce Fpp1 production at all. Besides calcium and the growth phase, temperature also seems to play a role in production of Fpp1. In this study we found that production of Fpp1 depends on factors such as calcium concentration, growth phase of the culture, and temperature. The combination of these parameters corresponds to the combination in the natural host during outbreaks of disease caused by F. psychrophilum. Consequently, we suggest that environmental host factors govern Fpp1 production.

Alternative Mating Strategies in Atlantic Salmon and Brown Trout

Abstract: By screening variable number of tandem repeat (VNTR) loci, multiple paternity within clutches has been found in wild populations of southern European Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). For Atlantic salmon, we determined the relative contribution of alternative male phenotypes to the next generation. Individual males that are morphologically juvenile yet sexually mature fertilized a large proportion of eggs, and they thereby contributed to an increase of genetic variability in wild populations via (1) balancing the sex ratio, (2) increasing outbreeding, and (3) enlarging the effective population size, in part a consequence of (1) and (2). In addition, these precocious males ensured that interspecific spawns involving Atlantic salmon females and brown trout males (a fairly common occurrence in southern Europe where the two species are sympatric) resulted mostly in Atlantic salmon progeny. For brown trout, preliminary genetic results indicated that multiple paternity, when present, was not due to alternative mating strategies by males, but rather to successive fertilizations by adult suitors.

Detecting the impact of climate and disturbances on tree-rings of Fagus sylvatica L. and Quercus robur L. in a lowland forest in Cantabria, Northern Spain

Abstract: L'influence relative du climat et des perturbations locales sur la croissance radiale du hetre et du chene pedoncule a ete analysee dans une vieille foret naturelle du Nord de l'Espagne. Entre 1925 et 1980, 36 % de la variance des largeurs de cernes du hetre et 29 % de celle du chene s'expliquent par le climat. Les modeles climatiques elabores montrent que la croissance radiale du hetre est limitee par les precipitations du mois de juillet de l'annee precedente, alors que celle du chene l'est par le deficit hydrique du mois de juillet de l'annee en cours. Dix periodes de perturbation de la croissance, d'origine non climatique, ont ete identifiees entre 1780 et 1997, parmi lesquelles celle de 1922-1935 a ete la plus importante. La croissance radiale des hetres apparait faible de 1800 a 1920 en raison de la fermeture du couvert forestier au cours de cette periode. Puis des perturbations survenues en 1922-1935 et 1948-1953 entrainent une augmentation de la croissance, qui devient alors superieure au signal commun. Conjointement, la reponse aux contraintes climatiques se renforce au cours des memes periodes. Chez le chene, les deviations de la croissance par rapport au signal commun sont en accord avec l'historique des perturbations locales jusqu'en 1850. Puis la croissance devient independante de ces perturbations et converge avec le signal commun. Sa reponse au climat demeure constante de 1925 a 1980.

Evidence for a heterotrophic subtropical northeast Atlantic

Abstract: The mean (±SE) depth-integrated gross production (P) of 2,600 ± 271 mg O2 m−2 d−1 derived from a compilation of data from nine cruises conducted between 1991–2000 in the subtropical NE Atlantic was found to be significantly lower (t-test, P = 0.005, N = 33) than the mean (±SE) community respiration (R) of 3,821 ± 276 mg O2 m−2 d−1. Two-thirds of the stations investigated were heterotrophic, and the P/R ratio of the communities tended to increase as P increased, such that communities where P < 3,000 mg O2 m−2 d−1 tended to be heterotrophic. The tendency for R to exceed P (P/R , 1.0) was statistically significant (Wilcoxon ranked sign test, P < 0.05) in the upper and deep layers of the photic zone, with an overall balance between P and R at intermediate depths. These results provide evidence that the subtropical NE Atlantic is a heterotrophic ecosystem, where planktonic communities respire more organic carbon than they produce, thereby acting as net sources of CO2.

A regulatory cascade involving retinoic acid, Cbfa1, and matrix metalloproteinases is coupled to the development of a process of perichondrial invasion and osteogenic differentiation during bone formation.

Abstract: Tissue-remodeling processes are largely mediated by members of the matrix metalloproteinase (MMP) family of endopeptidases whose expression is strictly controlled both spatially and temporally. In this article, we have examined the molecular mechanisms that could contribute to modulate the expression of MMPs like collagenase-3 and MT1-MMP during bone formation. We have found that all-trans retinoic acid (RA), which usually downregulates MMPs, strongly induces collagenase-3 expression in cultures of embryonic metatarsal cartilage rudiments and in chondrocytic cells. This effect is dose and time dependent, requires the de novo synthesis of proteins, and is mediated by RAR-RXR heterodimers. Analysis of the signal transduction mechanisms underlying the upregulating effect of RA on collagenase-3 expression demonstrated that this factor acts through a signaling pathway involving p38 mitogen-activated protein kinase. RA treatment of chondrocytic cells also induces the production of MT1-MMP, a membrane-bound metalloproteinase essential for skeletal formation, which participates in a proteolytic cascade with collagenase-3. The production of these MMPs is concomitant with the development of an RA-induced differentiation program characterized by formation of a mineralized bone matrix, downregulation of chondrocyte markers like type II collagen, and upregulation of osteoblastic markers such as osteocalcin. These effects are attenuated in metatarsal rudiments in which RA induces the invasion of perichondrial osteogenic cells from the perichondrium into the cartilage rudiment. RA treatment also resulted in the upregulation of Cbfa1, a transcription factor responsible for collagenase-3 and osteocalcin induction in osteoblastic cells. The dynamics of Cbfa1, MMPs, and osteocalcin expression is consistent with the fact that these genes could be part of a regulatory cascade initiated by RA and leading to the induction of Cbfa1, which in turn would upregulate the expression of some of their target genes like collagenase-3 and osteocalcin.