Showing papers by "University of Oviedo published in 1996"

Neurohormone melatonin prevents cell damage: effect on gene expression for antioxidant enzymes.

Abstract: It is well known that porphyrins cause a toxic light-mediated effect due to their capability to generate free radicals. Several reports have proved that melatonin is a potent free radical scavenger. The aim of this work has been to study the ability of melatonin to prevent the cell damage caused by porphyrins in the Harderian gland of female Syrian hamsters. Cell injury was evaluated estimating the percentage of damaged cells found in the gland and analyzing the degree of this damage at ultrastructural level. To explain the mechanism by which this hormone could prevent the cell damage caused by porphyrins, its capability to both decrease porphyrin synthesis and increase the mRNA levels for antioxidant enzymes was evaluated. Our results demonstrate that melatonin administration decreases the percentage of damaged cells, porphyrin synthesis, and aminolevulinate synthase (ALA-S) mRNA levels and increases the mRNA levels for manganese superoxide-dismutase and copper-zinc superoxide dismutase. When observed un...

Thermodynamical properties of solids from microscopic theory : applications to mgf2 and al2o3

Abstract: We have recently developed a non-empirical Debye-like model for the inclusion of thermal effects in the equation of state (EOS) of solids. This model allows the calculation of many thermodynamical properties from the E-V relationship. We report the results of a theoretical investigation that explores the EOS of two ionic solids: MgF2 and Al2O3. The interionic interactions are modelized using either the ab initio Perturbed Ion (aiPI) method or the electron gas formalism along with aiPI electronic wavefunctions, which are allowed to relax with crystal strains. Our EOS results are in overall good agreement with experimental data. Other thermodynamic properties behave in the same way, although Gruneisen constant and related quantities have significant errors. This may be caused by numerical inaccuracies on the high order derivatives needed for its calculation.

Molecular Cloning of a Novel Membrane-type Matrix Metalloproteinase from a Human Breast Carcinoma

Abstract: A new member of the matrix metalloproteinase (MMP) family of enzymes has been cloned from a human breast carcinoma cDNA library. The isolated cDNA contains on open reading frame 1554 bp long, encoding a polypeptide of 518 amino acids. The predicted amino acid sequence displays a similar domain organization as the remaining MMPs, including a prodomain with the activation locus, the zinc-binding site, and the hemopexin domain. In addition, it contains a C-terminal extension, rich in hydrophobic residues and similar in size to those present in the different membrane-type MMPs (MT-MMPs) identified to date. On the basis of these structural characteristics, this novel MMP has been tentatively called MT4-MMP, because it represents the fourth member of this subclass of MMPs characterized mainly by the occurrence of putative transmembrane domain in their amino acid sequences. MT4-MMP also contains a nine-residue insertion between the propeptide and the catalytic domain, which is a common feature of MT-MMPs and stromelysin-3. This amino acid sequence insertion ends with the consensus sequences R-X-R/K-R, which seems to be essential in the activation of these proteinases by furin. Northern blot analysis of polyadenylated RNAs isolated from a variety of human tissues revealed that the MT4-MMP gene ( MMP-17 ) is expressed mainly in the brain, leukocytes, the colon, the ovary, and the testis. The expression of MT4-MMP in leukocytes together with its putative membrane localization suggest that this enzyme could be involved in the activation of membrane-bound precursors of growth factors or inflammatory mediators such as tumor necrosis factor-α. In addition, MT4-MMP transcripts were detected in all breast carcinomas, as well as in all breast cancer cell lines analyzed in the present work. On the basis of these expression data in breast tumors, a potential role for human MT4-MMP in the tumoral process is also suggested.

Tuning and test of fragmentation models based on identified particles and precision event shape data

Abstract: Event shape and charged particle inclusive distributions are measured using 750000 decays of the Z to hadrons from the DELPHI detector at LEP. These precise data allow a decisive confrontation with models of the hadronization process. Improved tunings of the JETSET, ARIADNE and HERWIG parton shower models and the JETSET matrix element model are obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments. The description of the data distributions by the models is critically reviewed with special importance attributed to identified particles.

Protein and microsatellite single locus variability in Salmo salar L. (Atlantic salmon)

Abstract: We describe genetic variation at three microsatellite single loci and six allozyme loci of seven natural Atlantic salmon populations from Ireland and Spain. A comparison of genetic variability detected at both types of loci is performed. Also, the relative value of microsatellite single locus variability with regard to the identification of individual salmon populations is assessed. Microsatellite loci are shown to display higher levels of variation than allozyme loci. Mean number of alleles (6 ± 1.53) and heterozygosity (0.46 ± 0.04) at microsatellite loci are greater than those found for allozymes (1.85 ±0.05 and 0.21 + 0.03, respectively), and some microsatellite alleles appear to be specific for a location or geographical area. Allozyme and microsatellite variation show the same pattern of differentiation between populations with Irish and Spanish populations grouped into different clusters. However, greater values of genetic distance were found among microsatellite (D = 0.0747 + 0.011) rather than among allozyme loci (D = 0.0449 + 0.008). These results provide evidence that microsatellite-based analysis of genetic variation will be useful in the identification of individual populations of Atlantic salmon.

Systemic aluminum toxicity: effects on bone, hematopoietic tissue, and kidney.

Abstract: Although the full mechanisms are not yet elucidated, research into the mechanism of toxicity of aluminum (Al) on bone formation and remodeling and on hematopoietic tissue is ongoing. In contrast little information exists on the interactive effects of systemic Al and the kidney. In bone, both clinically and experimentally, high doses of Al inhibit remodeling, slowing both osteoblast and osteoclast activities and producing osteomalacia and adynamic bone disease. In contrast, while very low levels of Al are mitogenic in bones of experimental animals, the effect of low levels of Al in humans is unknown. Aluminum has been shown to have its mitogenic action at the osteoblast, but whether the effect on resorption is viz osteoblast-directed changes in osteoclast activity has not yet been determined. Parathyroid hormone (PTH) levels are disrupted by Al in humans and animals. Whether altered PTH levels play a major or even a minor role in Al-dependent osteotoxicity requires clarification. In hematopoietic tissue, Al causes a microcytic anemia, not reversible by iron. Friend leukemia cells treated with Al have been reported to accumulate excess iron, without incorporating it into ferritin or heme. It is not yet known which steps in iron metabolism are disrupted by Al, if they involve a single mechanism of action, or even if this disruption in iron metabolism accounts for the anemia seen in Al toxicosis. In kidney, research is needed to evaluate Al nephrotoxicity; there are almost no studies in this area. Furthermore, research is needed to evaluate mechanisms of renal Al excretion, presently shown by one study to occur at the distal tubule. Such studies might well throw light on whether Al plays a role in aggravating renal insufficiency, or whether the role of the kidney in Al toxicosis is limited to the causative effect of renal compromise on Al accumulation. In summary, while a number of mechanisms have been proposed for the toxic action of Al, no single mechanism emerges to explain these diverse effects of systemic Al. Recommendations for future research are presented and summarized in Table 1.

Preparation of a New Type of Phosphazene High Polymers Containing 2,2‘-Dioxybiphenyl Groups

Abstract: The direct reaction of [NPCl2]n with the difunctional reagent 2,2‘-dihydroxybiphenyl (HOC6H4C6H4OH) and K2CO3 in tetrahydrofuran gave soluble linear phosphazene high polymers instead of the expected cross-linked products. The reaction of [N3P3Cl6] with 1, 2, or 3 equiv of HOC6H4C6H4OH and K2CO3 in acetone gave the known spiro derivatives [N3P3Cl4(O2C12H8)], [N3P3Cl2(O2C12H8)2], and [N3P3(O2C12H8)3] without formation of bridging products, and the dichloro derivative reacted directly with para-substituted phenols HOC6H4R and K2CO3 in acetone to give the new compounds [N3P3(OC6H4R)2(O2C12H8)2] (R = Br, COC6H5, or OCH3), without signs of replacement of the bis(aryloxy) substituents. In an analogous manner, poly(dichlorophosphazene) [NPCl2]n reacted with HOC6H4C6H4OH and K2CO3 in THF without significant cross-linking to give, depending on the mole ratio, the soluble polymer [NP(O2C12H8)]n (Mw = 450 000, Tg = 160 °C) or the partially substituted polymers {[NP(O2C12H8)]0.35[NPCl2]0.65}n. The latter were subseque...

Sex chromosome linkage of 5S rDNA in rainbow trout (Oncorhynchus mykiss)

Abstract: The karyotype of the rainbow trout is characterized by a primitive XX/XY sex-determining chromosomal system. (Thorgaard et al., 1977). In the present study using FISH we have physically linked the 5S rRNA genes to the partially undifferentiated X chromosome pair. PCR amplified 5S rDNA was used for FISH and hybridization signals indicated that the genes were duplicated, present in one acrocentric and one metacentric pair of chromosomes. After analyzing several individuals, the female metaphases showed four fluorescent signals whereas males presented only three signals. Two of the three signals obtained in males corresponded to the metacentric pair whereas the single signal was mapped to the heterochromatin that cytologically differentiates the X chromosome from the Y chromosome. Double FISH experiments demonstrated that the 5S rDNA which is not sex linked is located at the NOR bearing arm close to the major ribosomal RNA genes (5.8S, 18S and 28S), similar to the situation observed in Atlantic salmon (Pendas et al., 1994a).

Contractual Form in Domestic and International Strategic Alliances

Abstract: This paper studies the factors that influence the adoption of a contractual form in strategic alliances within a transaction, cost framework. It is argued that joint ventures are preferred to contractual agreements as cooperation becomes increasingly complex. An analysis of 663 strategic alliances has confirmed this proposition while showing the differences that exist between domestic and international alliances. The former are more intensively influenced by variables relative to organizational complexity such as the number of partners and the number of functional areas; the latter being influenced to a greater extent by strategic complexity and the need to learn.

Systems of mating to reduce inbreeding in selected populations

Abstract: Stochastic simulation is used to compare different systems of mating to reduce rates of inbreeding in selection programmes with phenotypic or animal model best linear unbiased prediction (BLUP) evaluation. Compensatory mating (the mating between individuals from the largest selected families to individuals from the smallest) turns out to be proportionately about 0-30 more effective than minimum coancestry matings for situations with low rates of inbreeding, such as phenotypic selection or high population size, although the advantage is less apparent if common environmental effects are important. A modification of this system of mating is proposed which can be applied for overlapping generations, and this is shown to reduce rates of inbreeding proportionately by about 0-50 more than for discrete generations. Under high inbreeding, however, such as for BLUP selection and small population size, minimum coancestry matings, or even avoidance of sib matings are more effective. A procedure combining compensatory and minimum coancestry matings is also simulated and gives the largest reductions in the rate of inbreeding. The effects of these and other systems of mating on the rate of inbreeding are shown to occur through a reduction in the cumulative effect of selection and a deviation from Hardy-Weinberg proportions.

Ole e 3, an olive-tree allergen, belongs to a widespread family of pollen proteins.

Abstract: An allergen has been isolated from a saline extract of olive tree (Olea europaea) pollen. The protein consists of a single polypeptide chain of 9.2-kDa, as determined by mass spectrometry. It contains neither tryptophan nor tyrosine residues, and displays an acidic isoelectric point. The secondary structure of the protein, estimated from the analysis of the circular-dichroism spectrum in the peptide-bond region, is composed of 52% a-helix, 10%β-strand, 29%βturn and 9% non-regular conformation. The N-terminal end of the protein is blocked. Amino-acid-sequence data have been obtained from peptides produced by CNBr treatment of the native allergen. A partial sequence of 36 amino acids has thus been elucidated. The protein exhibits sequence similarity with pollen allergens from Brassica species and contains a Ca2+-binding motif. The isolated protein displays IgE-binding activity against sera of patients allergic to olive-tree pollen. It has been named Ole e 3, according to the recommendations of the IUIS Nomenclature Committee. IgG ELISA inhibition assays with polyclonal antibodies specific for Ole e 3 reveal the presence of proteins similar to Ole e 3 in the pollen from non-related plant species, which may explain allergic cross-reactivity processes.

The spatio-temporal pattern of photoreceptor degeneration in the aged rd/rd mouse retina.

Abstract: Photoreceptor degeneration in the retina of the rd/rd (retinal degeneration) mice has been studied using immunocytochemistry with antisera against cone- and rod-opsin. The rd/rd mice exhibited different regional specific rates of degeneration for rods and cones. As early as postnatal day 25, cells labelled with the rod-opsin and cone-opsin antisera disappeared preferently from the central retina. Whereas in the inferior half of the retina, degeneration subsequently proceeded towards the periphery, this did not occur in the dorsal hemisphere. By the age of 100 days, many cells immunoreactive for the cone-opsin antiserum and a few cells immunoreactive for the rod-opsin antiserum were located in an area of the dorsal retina. The ventral retina lacked labelled elements at this age. Finally, rd/rd mice at one year or 600 days of age contained a similar number of cone-opsin immunopositive cells (approximately 2000–2800 cells), occupying almost the same area in the retina as that found at 100 days of age. A photoreceptor candidate for the entrainment of non-visual photoreception probably remains in the cone population in aged rd/rd mice.

Fish community variation along physical gradients in short streams of northern Spain and the disruptive effect of dams

Abstract: Relationships between the fish community and selected habitat features were examined in a set of short temperate streams located at the northern end of the Iberian Peninsula. The fish fauna in these streams consists mostly of diadromous or estuarine species. Species richness and diversity increased with stream order, depth and width and decreased with elevation and distance from the sea. Stream order (positively) and elevation (negatively) were the two variables most highly correlated with species richness and diversity; higher order streams (order 3–4) showed greater values of species diversity than lower order ones (order 1) even when the elevation effect was removed. Addition of species in the downstream direction, but no replacement or loss was evidenced. We also compared the observed values of species diversity with those predicted from habitat features for a set of locations above unpassable dams. A great majority of the sites showed lower than predicted diversity values, which is an expected outcome for this mainly migratory fish fauna.

Evaluation of technologically important traits in lactic acid bacteria isolated from spontaneous fermentations

Abstract: A set of 120 isolates of Lactobacillus (75), Lactococcus (25) and Leuconostoc (20), mainly isolated from natural starter-free fermentation processes, has been screened for some technologically important traits, including lactose hydrolysis, extracellular polysaccharide production, fermentation of carbohydrates, antimicrobial agent susceptibility and bacteriocin production. Some of the strains exhibited important features for particular fermentations. Furthermore, the sensitivity resistance phenotype to antimicrobials showed genus-specific patterns.

Chromosomal localization of the major and 5S rRNA genes in the European eel (Anguilla anguilla)

Abstract: The major (18S, 5.8S, and 28S) and 5S rRNA genes have been mapped by double fluorescent in situ hybridization to European eel metaphase chromosomes. The major rRNA genes were localized to a submetacentric pair of chromosomes that showed a consistent size polymorphism among the individuals studied. The 5S rRNA genes were clustered in a single locus that mapped to the centromeric region of an acrocentric pair. In contrast to the major rRNA genes, no detectable polymorphism, in either size or intensity of the fluorescent signal, was observed. The chromosomal organization of both families of rRNA genes are discussed in terms of genomic organization and chromosomal evolution.

Mutational analysis of the human cyclin-dependent kinase inhibitor p27kip1 in primary breast carcinomas

Abstract: The human p27kip1 gene encodes a cyclin-dependent kinase inhibitor implicated in the negative regulation of the cell cycle. In order to elucidate the possible role of p27 mutations in the development or progression of human breast cancer, we have studied the occurrence of genetic abnormalities in this gene in a series of 30 primary breast carcinomas. Direct sequence analysis of the polymerase chain reaction amplified human p27 gene revealed the occurrence of two sequence variations with respect to the reported sequence; both variants were also present in the lymphocyte DNA from the same patients. First, a silent G to A change at codon 142 (Thr) was detected in a single case. Second, a T to G transversion at codon 109, resulting in a Val to Gly change, was observed in eight tumour DNA samples (26%) and in 31 out of 80 unrelated normal individuals (39%). This latter change creates a BglI restriction site that might be useful for genetic analysis of human tumours. Despite the occurrence of these polymorphisms, we did not however find any evidence of somatic mutations in the coding region of the p27 gene. On the basis of these results, we suggest that alterations in the integrity of the human p27 gene are not common events in human breast carcinomas.

Functional analysis of pneumolysin by use of monoclonal antibodies.

Abstract: We have produced a panel of monoclonal antibodies to pneumolysin, the membrane-damaging toxin from Streptococcus pneumoniae. We have used these antibodies to identify three regions of the toxin sequence that are involved in the lytic mechanism of this toxin. Two of these sites probably form the cell binding site of this toxin. Antibodies to the third site inhibit the lytic action of this toxin but not the binding of this toxin to cells. This site is engaged in the oligomerization process involved in the formation of pores in cell membranes. Two of these epitopes are also present in the related toxin perfringolysin O.

Genetic assessment of the reproductive success of Atlantic salmon precocious parr by means of VNTR loci

Abstract: Atlantic salmon precocious parr are dwarf mature males able to mate with adult females making profit of their small size. In this work the reproductive success of the dwarf males in the presence of an adult male and female spawning couple has been estimated in three different situations under simulated natural conditions at the Lapitxuri experimental channel (France). Different hypervariable minisatellite loci were used in the paternity assessment of the progeny. In all the situations tested, precocious parr were able to fertilize between 24.7 and 89.3 per cent of the total eggs. The results are discussed in relation to the important role of Atlantic salmon precocious parr in population structure and the evolution of salmon populations.

Phytoplankton biomass and production in shelf waters off NW Spain: spatial and seasonal variability in relation to upwelling

Abstract: Chlorophyll-a and primary production on the euphotic zone of the N-NW Spanish shelf were studied at 125 stations between 1984 and 1992. Three geographic areas (Cantabrian Sea, Rias Altas and Was Baixas), three bathymetric ranges (20 to 60 m, 60 to 150 m and stations deeper than 200 m), and four oceanographic stages (spring and autumn blooms, summer upwelling, summer stratification and winter mixing) were considered. One of the major sources of variability of chlorophyll and production data was season. Bloom and summer upwelling stages have equivalent mean and maximum values. Average chlorophyll-a concentrations approximately doubled in every step of the increasing productivity sequence: winter mixing — summer stratification — high productivity (upwelling and bloom) stages. Average primary production rates increased only 60% in the described sequence. Mean (± sd) values of chlorophyll-a and primary production rates during the high productivity stages were 59.7 ± 39.5 mg Chl-a m−2 and 86.9 ± 44.0 mg C m−2 h−1, respectively. Significant differences in both chlorophyll and primary production resulted between geographic areas in most stages. Only 27 stations showed the effects of the summer upwelling that affected coastal areas in the Cantabrian Sea and Rias Baixas shelf, but also shelf-break stations in the Rias Altas area. The Rias Baixas area had lower chlorophyll than both the Rias Altas and the Cantabrian Sea areas during spring and autumn blooms, but higher during summer upwelling events. On the contrary, primary production rates were higher in the Rias Baixas area during blooms in spring and autumn. Mid-shelf areas showed the highest chlorophyll concentrations during high productivity stages, probably due to the existence of frontal zones in all geographic areas considered. The estimated phytoplankton growth rates were comparable to those of other coastal upwelling systems, with average values lower than the maximum potential growth rates. Doubling rates for upwelling and stratification stages in the northern and Rias Altas shelf areas were equivalent, despite larger biomass accumulations during upwelling events. Low turnover rates of the existing biomass in the Rias Baixas shelf in upwelling stages suggests that the accumulation of phytoplankton was due mainly to the export from the highly productive rias, while the contribution of in situ production to these accumulations was relatively lower.

Immunohistochemistry of human cutaneous Meissner and pacinian corpuscles

Abstract: This paper reviews the immunohistochemical characteristics of two kinds of human cutaneous sensory nerve formations (SNFs), the Meissner and Pacinian corpuscles. In both kinds of SNF the central axon might be easily identifiable because it displays immunoreactivity (IR) for the neuroendocrine markers neuron-specific enolase and protein gene product 9.5, as well as for neuron-specific intermediate filament proteins, i.e., neurofilaments. Other intermediate filament proteins such as vimentin are localized in the lamellar cells of Meissner corpuscles, and in the inner core, outer core and capsule of Pacinian corpuscles. However, they lack cytokeratins or glial fibrillary acidic protein IR. On the other hand, and in agreement with ultrastructural data, IR for basement membrane constituents laminin and type IV collagen is found underlying all SNF constituents, with the exception of the axon. One of the mechanisms involved in the maintenance of intracellular calcium ions (Ca2+) homeostasis is the calcium binding proteins. Ca2+ play a key role in the mechanoelectric transduction and have been localized in SNFs. In this way IR for the Ca(2+)-binding proteins calbindin D28K, parvalbumin and calretinin, is present and colocalized in both Meissner and Pacinian corpuscles; furthermore, S-100 protein is exclusively localized in the lamellar cells and the inner core. On the other hand, the skin is a main source of neurotrophins for a subset of neural crest sensory neurons, some of which end forming SNF. These factors are conveyed via retrograde axonal transport from the skin to the cell body of the responsive neurons. Interestingly, Meissner and Pacinian corpuscles also display IR for the pan-neurotrophin low-affinity receptor (p75), and for the trkA receptor protein, a basic constituent of the high-affinity receptor for some neurotrophins. Moreover, they express IR for the epidermal growth factor receptor. Finally, other antigens not proper to the cells forming human cutaneous SNF, such as the epithelial membrane antigen and the leucocytary antigen-7, have also been detected.

Energy dependence of the differences between the quark and gluon jet fragmentation

Abstract: Three jet events arising from decays of the Z boson, collected by the DELPHI detector, were used to measure differences in quark and gluon fragmentation. Gluon jets were anti-tagged by identifying b quark jets. Unbiased quark jets came from events with two jets plus one photon. Quark and gluon jet properties in different energy ranges were compared for the first time within the same detector. Quark and gluon jets of nearly the same energy in symmetric three jet event topologies were also compared. Using three independent methods, the average value of the ratio of the mean charged multiplicities of gluon and quark jets is = 1.241 ± 0.015 (stat.) ± 0.025 (syst.). Gluon jets are broader and produce fragments with a softer energy spectrum than quark jets of equivalent energy. The string effect has been observed in fully symmetric three jet events. The measured ratio R_{gamma} of the charged particle flow in the qoverline{q} inter-jet region of the qar{q}g and qar{q}gamma samples agrees with the perturbative QCD expectation. The dependence of the mean charged multiplicity on the hadronic center-of-mass energy was analysed in photon plus n-jet events. The value for alpha_s(M_Z) determined from these data using a QCD prediction with corrections at leading and next-to-leading order is αs(MZ)= 0.116 ± 0.003 (stat.) ± 0.009 (syst.).