El "cervell" a la punta de l'arrel?

L'àpex de l'arrel podria tenir una funció similar a la del cervell dels animals inferiors, rebent senyals i coordinant moviments. Aquesta idea no és nova: ja l'havia formulada Darwin l'any 1880, i està recolzada pel fet que s'han detectat a l'arrel senyals químics i elèctrics que podrien ser anàlegs als del nostre sistema nerviós. Aquesta comunicació entre les cèl·lules de la planta disposaria d'un "centre d'operacions" a l'àpex de l'arrel, on s'integraria i es processaria la informació per a la "presa de decisions". Una investigació realitzada al laboratori de Biologia Molecular de plantes de la UAB sobre la distribució i regulació de l'auxina, hormona implicada pràcticament en tots els processos del desenvolupament de les plantes superiors, aporta nous coneixements per a comprendre millor aquests processos.El ápice de la raíz podría tener una función similar a la del cerebro de losanimales inferiores, recibiendo señales y coordinando movimientos. Estaidea no es nueva: ya la había formulado Darwin en 1880, y estáapoyada por el hecho de que se han detectado en la raíz señales químicas y eléctricas que podrían ser análogos a los de nuestro sistema nervioso. Esta comunicación entre las células de la planta dispondría deun "centro de operaciones" en el ápice de la raíz, donde se integraría y se procesaría la información para la "toma de decisiones". Una investigación realizada en el laboratorio de Biología Molecular de plantas de la UAB sobre la distribución y regulación de la auxina, hormona implicada en el desarrollo de las plantas superiores, aporta nuevos conocimientos para comprender mejor estos proceso

Proceso de simbolización del concepto de potencia : análisis de libros de texto de secundaria

En este trabajo se presenta un estudio del desarrollo del sistema de signos del concepto de potencia en los libros de texto de matemáticas de educación secundaria obligatoria. Se analiza el tratamiento que los textos promueven de los contenidos conceptuales y procedimentales asociados a la idea de potencia. Para ello se seleccionan «dominios de actividad matemática» (Mamona-Downs y Downs, 2002) que caracterizan el concepto y se relacionan con las «etapas del proceso de abstracción» asociado al desarrollo de los signos matemáticos en el sentido que propone Socas (1997). El análisis permite identificar las características del concepto y la ausencia de aspectos relevantes del signifi cado de potencia que ponen de manifiesto los libros de texto analizados

Proceso de simbolización del concepto de potencia : análisis de libros de texto de secundaria

En este trabajo se presenta un estudio del desarrollo del sistema de signos del concepto de potencia en los libros de texto de matemáticas de educación secundaria obligatoria. Se analiza el tratamiento que los textos promueven de los contenidos conceptuales y procedimentales asociados a la idea de potencia. Para ello se seleccionan «dominios de actividad matemática» (Mamona-Downs y Downs, 2002) que caracterizan el concepto y se relacionan con las «etapas del proceso de abstracción» asociado al desarrollo de los signos matemáticos en el sentido que propone Socas (1997). El análisis permite identificar las características del concepto y la ausencia de aspectos relevantes del significado de potencia que ponen de manifiesto los libros de texto analizados.This paper studies the development of sign systems associated with the concept of power presented in secondary school Mathematics textbooks. The treatment that texts provide of the conceptual and procedural contents associated to the concept of power is analysed in this work. For this objective, we have selected «Mathematical activity domains» (Mamona-Downs & Downs, 2002) which characterizes the concept, connecting it with the development of abstraction process stages of mathematical signs as described by Socas (1997). This analysis allows us to identify features of the concept and the lack of relevant aspects of the meaning of the concept of powe

Improved wear performance of ultra high molecular weight polyethylene coated with hydrogenated diamond like carbon

Hydrogenated diamond like carbon (DLCH) thin films were deposited on medical grade ultra high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition. The DLCH coating thicknesses ranged from 250 to 700. nm. The substrates were disks made of UHMWPEs typically used for soft components in artificial joints, namely virgin GUR 1050 and highly crosslinked (gamma irradiated in air to 100. kGy) UHMWPEs. Mechanical and tribological properties under bovine serum lubrication at body temperature were assessed on coated and uncoated polyethylenes by means of nano-hardness and ball-on-disk tests, respectively. Morphological features of the worn surfaces were obtained by confocal microscopy and scanning electron microscopy. This study confirms an increase in surface hardness and good wear resistance for coated materials after 24. h of sliding test compared to uncoated polyethylene. These results point out that to coat UHMWPE with DLCH films could be a potential method to reduce backside wear in total hip and knee arthroplasties.Ministerio de Ciencia y Educación MAT2006-12603- C02-01, CSD2008-0002

Trace elements and C and N isotope composition in two mushroom species from a mine-spill contaminated site

Fungi play a key role in the functioning of soil in terrestrial ecosystems, and in particular in the remediation of degraded soils. The contribution of fungi to carbon and nutrient cycles, along with their capability to mobilise soil trace elements, is well-known. However, the importance of life history strategy for these functions has not yet been thoroughly studied. This study explored the soil-fungi relationship of two wild edible fungi, the ectomycorrhizal Laccaria laccata and the saprotroph Volvopluteus gloiocephalus. Fruiting bodies and surrounding soils in a mine-spill contaminated area were analysed. Isotope analyses revealed Laccaria laccata fruiting bodies were 15N-enriched when compared to Volvopluteus gloiocephalus, likely due to the transfer of 15N-depleted compounds to their host plant. Moreover, Laccaria laccata fruiting bodies δ13C values were closer to host plant values than surrounding soil, while Volvopluteus gloiocephalus matched the δ13C composition to that of the soil. Fungal species presented high bioaccumulation and concentrations of Cd and Cu in their fruiting bodies. Human consumption of these fruiting bodies may represent a toxicological risk due to their elevated Cd concentrations

Deciphering the plasma membrane hallmarks of apoptotic cells: Phosphatidylserine transverse redistribution and calcium entry

BACKGROUND: During apoptosis, Ca(2+)-dependent events participate in the regulation of intracellular and morphological changes including phosphatidylserine exposure in the exoplasmic leaflet of the cell plasma membrane. The occurrence of phosphatidylserine at the surface of specialized cells, such as platelets, is also essential for the assembly of the enzyme complexes of the blood coagulation cascade, as demonstrated by hemorrhages in Scott syndrome, an extremely rare genetic deficiency of phosphatidylserine externalization, without other apparent pathophysiologic consequences. We have recently reported a reduced capacitative Ca(2+) entry in Scott cells which may be part of the Scott phenotype. RESULTS: Taking advantage of these mutant lymphoblastoid B cells, we have studied the relationship between this mode of Ca(2+) entry and phosphatidylserine redistribution during apoptosis. Ca(2+) ionophore induced apoptosis in Scott but not in control cells. However, inhibition of store-operated Ca(2+) channels led to caspase-independent DNA fragmentation and decrease of mitochondrial membrane potential in both control and Scott cells. Inhibition of cytochrome P450 also reduced capacitative Ca(2+) entry and induced apoptosis at comparable extents in control and Scott cells. During the apoptotic process, both control and more markedly Scott cells externalized phosphatidylserine, but in the latter, this membrane feature was however dissociated from several other intracellular changes. CONCLUSIONS: The present results suggest that different mechanisms account for phosphatidylserine transmembrane migration in cells undergoing stimulation and programmed death. These observations testify to the plasticity of the plasma membrane remodeling process, allowing normal apoptosis even when less fundamental functions are defective