146 research outputs found

    L’impacte de la cabra (Capra hircus) sobre el teix (Taxus baccata) a l’illa de Mallorca

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    [cat] El teix Taxus baccata a les Balears es troba únicament a la Serra de Tramuntana, està protegit com d’Especial Protecció i és objecte d’un Pla de Maneig executat per la Conselleria de Medi Ambient del Govern de les Illes Balears. La forta pressió de les cabres Capra hircus, incrementada els darrer decennis per l’abandonament de les finques i l’agricultura, és una amenaça que fa perillar el futur del teix. El present treball completa i revisa l’inventari de teixos naturals a la Serra i avalua el seu estat de conservació en funció del grau d’afectació per les cabres assilvestrades. Un 70% dels teixos silvestres pateixen impactes visibles provocats per les cabres. Tot i que la majoria de teixos es trobem empenyalats, la gran majoria (un 84%) pateix un grau d’afectació moderat; el 14% restant presenta una afectació greu, amb una clara amenaça per a la seva supervivència. Els teixos menys afectats són els més difícilment accessibles, i no hi ha cap opció de que puguin créixer amb normalitat a un lloc on arribin les cabres. Ara que ja no es talla ni es permeten les cremes descontrolades, el teix podria tenir unes poblacions més nombroses, tot i que les elevades temperatures estivals i la disminució de les precipitacions, com a conseqüència del canvi climàtic, podrien esdevenir un factor limitant. Avui, però, el principal factor limitant no natural que afecta les poblacions de teix a Mallorca és la pressió que exerceixen les cabres assilvestrades les quals, en molts de casos, poden arribar a provocar la mort dels exemplars.[eng] The yew Taxus baccata in the Balearic Islands is only in the Serra de Tramuntana. It is under Special Protection category and is object of a Management Plan executed by the Balearic Environmental Administration. The strong pressure of goats Capra hircus, increased over the last decades due to the abandonment of farms and agriculture, is a threat that endangers yews future. The present report completes and reviews the inventory of natural yews in the Serra and evaluates its state of conservation based on the degree of involvement by the wild goats. 70% of natural yews suffer visible impacts caused by goats. Although most yews are in cliffs, the vast majority (84%) suffers a moderate degree of threat; the remaining 14% have a serious affectation, with a clear threat to their survival. The least-affected yews are the most difficult to reach, and there is no option to grow normally on a goat's place. Now that neither the cutting of yew or the uncontrolled burning are not allowed, the yew tree could have larger populations, although the high summer temperatures and the decrease of the precipitations, as a consequence of the climate change, could become a limiting factor. Today, however, the main unnatural limiting factor affecting yew populations in Mallorca is the pressure exerted by feral goats which, in many cases, may cause the death of specimens

    Transforming growth factor -α expression in rat experimental hepatocarcinogenesis

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    Growth factors in general and transforming growth factor-alpha in particular have been related to cell proliferation and cell differentiation. This study was designed to clarify the distribution pattem of TGF-alpha in chemically-induced hepatocarcinogenesis. Sprague- Dawley rats were subjected to different non-intensive or intensive carcinogenic treatments using diethylnitrosamine (DEN) as carcinogen and ethinyl estradiol (EE) as promoter. The livers were fixed in 2% paraformaldehyde, dehydrated in a series of ethanol solutions, embedded in paraffin and sectioned. In the preneoplastic lesions no TGF-alpha immunoreactive cells were identified, but in some hepatic tumours cell immunostained with TGF-alpha antibody were observed. These results suggest that the cells capable of expressing TGF-a constitutively may be involved in neoplastic development in vivo

    Cavitation of Electrons Bubbles in Liquid Helium Below saturation Pressure

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    We have used a Hartree-type electron-helium potential together with a density functional description of liquid 4^4He and 3^3He to study the explosion of electron bubbles submitted to a negative pressure. The critical pressure at which bubbles explode has been determined as a function of temperature. It has been found that this critical pressure is very close to the pressure at which liquid helium becomes globally unstable in the presence of electrons. It is shown that at high temperatures the capillary model overestimates the critical pressures. We have checked that a commonly used and rather simple electron-helium interaction yields results very similar to those obtained using the more accurate Hartree-type interaction. We have estimated that the crossover temperature for thermal to quantum nucleation of electron bubbles is very low, of the order of 6 mK for 4^4He.Comment: 22 pages, 9 figure

    Cell cycle-dependent acetylation of Rb2/p130 in NIH3T3 cells

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    The retinoblastoma protein (pRb) and the pRb-related proteins, p130 and p107, form the ‘pocket protein' family of cell cycle regulatory factors. A well characterized function of these proteins is the cell cycle-dependent regulation of E2F-responsive genes. The biological activity of pocket proteins is regulated by phosphorylation and for the founding member pRb it has been shown that acetylation also has an important role in modulating its function during the cell cycle. Here, we show that hyperphosphorylated retinoblastoma 2 (Rb2)/p130 also exists in an acetylated form in NIH3T3 cells. Acetylated p130 is present in the nucleus but not in the cytoplasm. Acetylation is cell cycle dependent, starting in S-phase and persisting until late G2-period. Using recombinant p130 and truncated forms for in vitro acetylation by the acetyltransferase p300, we could identify K1079 in the C-terminal part as the major acetylation site by mass spectrometry. Minor acetylation sites were pinpointed to K1068 and K1111 in the C-terminus, and K128 and K130 in the N-terminus. The human papilloma virus 16 protein-E7 preferentially binds to acetylated p130 and significantly increases in vitro p130 acetylation by p300

    The ITS1-5.8S-ITS2 Sequence Region in the Musaceae: Structure, Diversity and Use in Molecular Phylogeny

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    Genes coding for 45S ribosomal RNA are organized in tandem arrays of up to several thousand copies and contain 18S, 5.8S and 26S rRNA units separated by internal transcribed spacers ITS1 and ITS2. While the rRNA units are evolutionary conserved, ITS show high level of interspecific divergence and have been used frequently in genetic diversity and phylogenetic studies. In this work we report on the structure and diversity of the ITS region in 87 representatives of the family Musaceae. We provide the first detailed information on ITS sequence diversity in the genus Musa and describe the presence of more than one type of ITS sequence within individual species. Both Sanger sequencing of amplified ITS regions and whole genome 454 sequencing lead to similar phylogenetic inferences. We show that it is necessary to identify putative pseudogenic ITS sequences, which may have negative effect on phylogenetic reconstruction at lower taxonomic levels. Phylogenetic reconstruction based on ITS sequence showed that the genus Musa is divided into two distinct clades – Callimusa and Australimusa and Eumusa and Rhodochlamys. Most of the intraspecific banana hybrids analyzed contain conserved parental ITS sequences, indicating incomplete concerted evolution of rDNA loci. Independent evolution of parental rDNA in hybrids enables determination of genomic constitution of hybrids using ITS. The observation of only one type of ITS sequence in some of the presumed interspecific hybrid clones warrants further study to confirm their hybrid origin and to unravel processes leading to evolution of their genomes

    Functionalized Positive Nanoparticles Reduce Mucin Swelling and Dispersion

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    Multi-functionalized nanoparticles (NPs) have been extensively investigated for their potential in household and commercial products, and biomedical applications. Previous reports have confirmed the cellular nanotoxicity and adverse inflammatory effects on pulmonary systems induced by NPs. However, possible health hazards resulting from mucus rheological disturbances induced by NPs are underexplored. Accumulation of viscous, poorly dispersed, and less transportable mucus leading to improper mucus rheology and dysfunctional mucociliary clearance are typically found to associate with many respiratory diseases such as asthma, cystic fibrosis (CF), and COPD (Chronic Obstructive Pulmonary Disease). Whether functionalized NPs can alter mucus rheology and its operational mechanisms have not been resolved. Herein, we report that positively charged functionalized NPs can hinder mucin gel hydration and effectively induce mucin aggregation. The positively charged NPs can significantly reduce the rate of mucin matrix swelling by a maximum of 7.5 folds. These NPs significantly increase the size of aggregated mucin by approximately 30 times within 24 hrs. EGTA chelation of indigenous mucin crosslinkers (Ca2+ ions) was unable to effectively disperse NP-induced aggregated mucins. Our results have demonstrated that positively charged functionalized NPs can impede mucin gel swelling by crosslinking the matrix. This report also highlights the unexpected health risk of NP-induced change in mucus rheological properties resulting in possible mucociliary transport impairment on epithelial mucosa and related health problems. In addition, our data can serve as a prospective guideline for designing nanocarriers for airway drug delivery applications

    Deciduous Trees and the Application of Universal DNA Barcodes: A Case Study on the Circumpolar Fraxinus

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    The utility of DNA barcoding for identifying representative specimens of the circumpolar tree genus Fraxinus (56 species) was investigated. We examined the genetic variability of several loci suggested in chloroplast DNA barcode protocols such as matK, rpoB, rpoC1 and trnH-psbA in a large worldwide sample of Fraxinus species. The chloroplast intergenic spacer rpl32-trnL was further assessed in search for a potentially variable and useful locus. The results of the study suggest that the proposed cpDNA loci, alone or in combination, cannot fully discriminate among species because of the generally low rates of substitution in the chloroplast genome of Fraxinus. The intergenic spacer trnH-psbA was the best performing locus, but genetic distance-based discrimination was moderately successful and only resulted in the separation of the samples at the subgenus level. Use of the BLAST approach was better than the neighbor-joining tree reconstruction method with pairwise Kimura's two-parameter rates of substitution, but allowed for the correct identification of only less than half of the species sampled. Such rates are substantially lower than the success rate required for a standardised barcoding approach. Consequently, the current cpDNA barcodes are inadequate to fully discriminate Fraxinus species. Given that a low rate of substitution is common among the plastid genomes of trees, the use of the plant cpDNA “universal” barcode may not be suitable for the safe identification of tree species below a generic or sectional level. Supplementary barcoding loci of the nuclear genome and alternative solutions are proposed and discussed

    Reassessing global change research priorities in mediterranean terrestrial ecosystems : how far have we come and where do we go from here?

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    Aim: Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. - Location: Mediterranean terrestrial ecosystems. - Methods: This article revisits the research priorities proposed in a 1998 assessment. - Results: A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. - Main conclusions:(1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with large-scale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use
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