66 research outputs found

    Estudio taxonómico y filogenético de las variedades de Struthiopteris spicant (L.) Weiss (Blechnaceae, Polypodiopsida) en Europa

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    Struthiopteris spicant (L.) Weiss es un helecho con una amplia distribución en el hemisferio norte, en América y Eurasia. Presenta cierta plasticidad fenotípica, de manera que algunas entidades subordinadas han sido descritas, siendo consideradas la mayoría variedades y formas ecológicas. Dos de estas variedades aparecen en la Península Ibérica, la más común, la variedad spicant, y la variedad homophyllum (Merino) Gabriel y Galán & Pino, que está definida como endémica del noreste de la Península. Además, varios individuos con una apariencia similar y difícilmente asignables a ninguna de las variedades descritas han sido encontrados en el norte de la Península, Salamanca y las Islas Canarias. También existe una variedad islandesa, la variedad fallax (Lange) Wasowicz & Gabriel y Galán, endémica de Deildartunguhver (oeste de Islandia), a la que hemos tenido acceso. Todas estas formas presentan diferencias morfológicas muy notables que nos hacen dudar de su rango taxonómico. En este trabajo, se ha llevado a cabo un análisis morfológico y anatómico completo de 43 individuos de las tres formas. Además, en 15 individuos se ha realizado un estudio genético de sitios polimórficos utilizando marcadores cloroplásticos, nucleares y microsatélites. Los resultados obtenidos indican que algunos caracteres anatómicos (sobre todo las escamas y los tamaños foliares) podrían tener una significación taxonómica, lo que viene apoyado por los datos moleculares. En conclusión, se puede considerar que estamos tratando con entes de rango taxonómico mayor que meras variedades

    Sinopsis global y aproximación a la filogenia molecular del género Parablechnum C. Presl (Blechnaceae, Polypodiopsida)

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    Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Biológicas, leída el 05-09-2022The family Blechnaceae is a lineage that includes about 280 species in 25 genera, and together with the Onocleaceae is the most recent family of ferns. Within this family, Parablechnum is the most diverse genus, with about 65 species. The distribution of this genus reflects very well the distribution of the most diverse areas of the family: Central and South America, the Austropacific and some representatives in southern Africa, Madagascar and the Mascarene archipelago.The distribution of this genus reflects a disjunction that could easily be explained by Gondwanan vicariance, but the available dating indicates that the genus underwent a rapid radiation after the separation from Gondwana, which would imply that its distribution is due to long-distance dispersal (LDD). In addition, the intra-continental dispersal of the genus together with other problems such as poor representation in herbaria has made the taxonomy of Parablechnum unclear to date.In this context, a revision of the systematics of the genus has been proposed using herbarium material and some field collections to elucidate the taxonomy and evolutionary history of the genus.For this purpose, 3,738 specimens from 52 herbariums of all the species of Parablechnum conceived to date have been examined physically and digitally. Where possible, the anatomy of the fertile pinnae and epidermis was studied, and spores and sporangia were observed by light and electron microscopy. In addition, DNA was extracted from 127 individuals and five chloroplastic markers were sequenced for maximum likelihood phylogenetic trees and Bayesian inference. In addition, a dating have been carried out. For this purpose, 582 sequences were used, 469 of which were newly created in this work...La familia Blechnaceae es un linaje que incluye unas 280 especies en 25 géneros, y junto con las Onocleaceae es la familia más reciente de helechos. Dentro de esta familia, Parablechnum es el género más diverso, con alrededor de 65 especies. La distribución de este género refleja muy bien la distribución de los puntos más diversos de la familia: América Central y del Sur, el Austropacífico y algunos representantes en el sur de África, Madagascar y el archipiélago mascareno. La distribución de este género refleja una disyunción que podría explicarse fácilmente por la vicarianza gondwánica, pero las dataciones disponibles indican que el género tuvo una radiación rápida tras la separación de Gondwana, lo que implicaría que su distribución se debe a la dispersión a larga distancia (LDD). Además, la dispersión dentro de los distintos continentes del género junto con otros problemas como la escasa representación en los herbarios ha hecho que la taxonomía de Parablechnum no esté clara hasta la fecha. En este contexto, se ha propuesto una revisión de la sistemática del género utilizando material de herbario y algunas colecciones de campo para dilucidar la taxonomía y la historia evolutiva del género. Para ello, se han examinado 3.738 pliegos provenientes de 52 herbarios de todas las especies concebidas hasta hoy de Parablechnum, de forma física y presencial. En los taxones en los que ha sido posible se ha estudiado de la anatomía de las pinnas fértiles, la epidermis y se han observado las esporas y los esporangios con microscopía óptica y electrónica. Así mismo, se ha extraído ADN de 127 individuos y se han secuenciado cinco marcadores cloroplásticos para la realización de árboles filogenéticos de máxima verosimilitud e inferencia bayesiana. Además, se ha realizado una datación. Para este fin se han utilizado 582 secuencias de las cuales 469 son de nueva creación en este trabajo...Fac. de Ciencias BiológicasTRUEunpu

    Synthesis and incorporation of rod-like nano-hydroxyapatite into type I collagen matrix: A hybrid formulation for 3D printing of bone scaffolds

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    Abstract Over the recent years, nanometric hydroxyapatite (HA) has gained interest as constituent of hybrid systems for bone scaffold fabrication, due to its biomimicry and biocompatibility. In this study, rod-like nano-HA particles were introduced in a type I collagen matrix to create a composite mimicking the bone composition. HA nano-rods (40−60 nm × 20 nm) were synthesised by hydrothermal method involving the use of an ammonium-based dispersing agent (Darvan 821-A) and fully characterised. The homogeneous dispersion of HA nanoparticles throughout the final hybrid formulation was achieved through their suspension in a collagen solution in presence of Darvan 821-A. The resulting homogeneous collagen/nano-HA suspension proved to be suitable for extrusion printing applications, showing shear thinning and sol-gel transition upon simil-physiological conditions. Furthermore, mesh-like structures were printed in a gelatine-supporting bath by means of a commercial bioprinter further demonstrating the potential of the designed hybrid system for the fabrication of 3D bone-like scaffolds

    Novel multifunctional strontium-copper co-substituted mesoporous bioactive particles

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    Abstract Sr-Cu co-substituted mesoporous bioactive glasses were synthesized by two different sol-gel approaches: an ultrasound-assisted base-catalyzed sol-gel procedure and an aerosol-assisted spray-drying method. The produced spherical shaped particles showed high specific surface area values and tunable pore size. The two different routes allowed obtaining samples with different morphology and size, characterized by the ability to induce hydroxyapatite deposition, to incorporate a specific amount of therapeutic ions (strontium with the aim to improve bone formation and copper for its antibacterial and pro-angiogenic properties) and to release them. The obtained multifunctional biomaterials synergistically combine the ability to promote bone formation and angiogenesis and to impart an antibacterial effect

    Imaging techniques for the assessment of the bone osteoporosis-induced variations with particular focus on micro-ct potential

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    For long time, osteoporosis (OP) was exclusively associated with an overall bone mass reduction, leading to lower bone strength and to a higher fracture risk. For this reason, the measurement of bone mineral density through dual X-ray absorptiometry was considered the gold standard method for its diagnosis. However, recent findings suggest that OP causes a more complex set of bone alterations, involving both its microstructure and composition. This review aims to provide an overview of the most evident osteoporosis-induced alterations of bone quality and a résumé of the most common imaging techniques used for their assessment, at both the clinical and the laboratory scale. A particular focus is dedicated to the micro-computed tomography (micro-CT) due to its superior image resolution, allowing the execution of more accurate morphometric analyses, better highlighting the architectural alterations of the osteoporotic bone. In addition, micro-CT has the potential to perform densitometric measurements and finite element method analyses at the microscale, representing potential tools for OP diagnosis and for fracture risk prediction. Unfortunately, technological improvements are still necessary to reduce the radiation dose and the scanning duration, parameters that currently limit the application of micro-CT in clinics for OP diagnosis, despite its revolutionary potential

    Design and Performance of an Adsorption Bed with Activated Carbons for Biogas Purification

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    Organic waste can be efficiently converted into energy using highly efficient energy systems, such as SOFCs coupled to the anaerobic digestion process. SOFC systems fed by biogenous fuels, such as biogas or syngas, suffer long-term stability due to trace compound impacts. It follows that, a mandatory gas cleaning section is needed to remove these pollutants at lower concentrations. This work investigates the adsorption mechanism for micro-contaminant removal through experimental results achieved using solid sorbents. Samples of different sorbent materials were analyzed in the laboratory to determine their performances in terms of sulfur (mainly hydrogen sulfide) and siloxanes (mainly D4-Octamethylcyclotetrasiloxane) adsorption capacities. The analysis shows that the chemical composition of the samples influences the adsorption of H2S (i.e., presence of calcium, iron, copper), while the effect of their textural properties mainly influences the adsorption of siloxane compounds, such as D4. A quantitative analysis was performed considering the influence of gas velocity on adsorption capacity. By increasing the biogas velocity (+45% and +89%), there was an indirect correlation with the H2S adsorption capacity (−27% and −44%). This identified an aspect related to the residence time required to be able to remove and retain the trace compound. The results obtained and summarized were used to develop a strategy for the removal of trace compounds in large-scale plants, e.g., for water purification

    The incorporation of strontium to improve bone-regeneration ability of mesoporous bioactive glasses

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    Over the recent years, mesoporous bioactive glasses (MBGs) gained interest as bone regeneration systems, due to their excellent bioactivity and ability to release therapeutic molecules. In order to improve the bone regeneration ability of MBGs, the incorporation of Sr2+ ions, due to its recognized pro-osteogenenic potential, represents a very promising strategy. In this study, MBGs based on the SiO₂⁻CaO system and containing different percentages (2 and 4 mol %) of strontium were prepared by two synthesis methods, in the form of microspheres and nanoparticles. Sr-containing MBGs were characterized by FE-SEM, XRD and N₂ adsorption/desorption analysis. The in vitro bioactivity in SBF resulted excellent. The assessment of fibroblast cell (line L929) viability showed that Sr-containing MBGs were biocompatible both in form of micro- and nanoparticles. The osteogenic response of osteoblast-like SAOS-2 cells was investigated by analysing the expression of GAPDH, COL1a1, RANKL, SPARC, OPG and ALPL genes, as cell differentiation markers. The results indicate that the incorporation of Sr into MBG is beneficial for bone regeneration as promotes a pro-osteogenic effect, paving the way to the design of advanced devices enabled by these nanocarriers also in combination with drug release, for the treatment of bone pathologies, particularly in patients with osteoporosis

    Osteoporosis-related variations of trabecular bone properties of proximal human humeral heads at different scale lengths

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    Abstract Osteoporosis (OP) is a skeletal disorder responsible for the weakening of the bone structure and, consequently, for an increased fracture risk in the elderly population. In the past, bone mineral density (BMD) variation was considered the best OP indicator, but recently the focus has shifted toward the variation of microstructural bone parameters. This work is based on the characterisation of 8-mm cylindrical biopsies harvested from proximal humeral heads belonging to healthy and osteoporotic patients, in order to assess the OP-related variations of bone properties at different scale lengths. In particular, bone biopsies underwent micro-computed tomography analysis to study the most relevant features of bone architecture and extrapolate the tissue mineral density (TMD) value of bone trabeculae. Compression tests and nanoindentations were performed to investigate the macro- and micromechanical properties of bone biopsies, respectively. In addition, XRD analyses were performed to obtain the mean hydroxyapatite (HA) crystallite size, while Raman spectroscopy investigated the collagen secondary structure. Thermogravimetric analysis was performed to evaluate the ratio between organic and inorganic phases. From the obtained results, OP samples showed a more anisotropic and less interconnected structure responsible for reduced compression strength. From this, it can be supposed that OP caused an alteration of bone structure that led to inferior macroscopic mechanical properties. Furthermore, OP samples possessed higher TMD and bigger HA crystals that are correlated to an increase of the hardness value obtained by means of nanoindentation. This less controlled HA crystal growth is probably due to an alteration of the organic matrix structure, as revealed by the increase of the random coil contribution in the Raman spectra of the OP bone. This higher crystal content led to an increase in trabecular density and hardness. In conclusion, the obtained data showed that OP affects bone properties at different scale lengths causing an alteration of its morphological, structural and mechanical features

    Biomimetic and mesoporous nano-hydroxyapatite for bone tissue application: a short review

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    In the last decades, many research groups have experimented the synthesis of hydroxyapatite (HA) for bone tissue application obtaining products with different shapes and dimensions. This review aims to summarise and critically analyse the most used methods to prepare physiologic-like nano-HA, in the form of plates or rods, similar to the HA present in the human bones. Moreover, mesoporous HA has gained increasing interest in the biomedical field due its pecualiar structural features, such as high surface area and accessible mesoporous volume, which is known to confer enhanced biological behaviour and the possibility to act as nanocarriers of functional agents for bone-related therapies. For this reason, more recent studies related to the synthesis of mesoporous HA, with physiological-like morphology, are also considered in this review. Since a wide class of surfactant molecules plays an essential role both in the shape and size control of HA crystals and in the formation of mesoporosity, a section devoted to the mechanisms of action of several surfactants is also provided
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