Study of the influence of actin-binding proteins using linear analyses of cell deformability

The actin cytoskeleton plays a key role in the deformability of the cell and in mechanosensing. Here we analyze the contributions of three major actin cross-linking proteins, myosin II, a-actinin and filamin, to cell deformability, by using micropipette aspiration of Dictyostelium cells. We examine the applicability of three simple mechanical models: for small deformation, linear viscoelasticity and drop of liquid with a tense cortex; and for large deformation, a Newtonian viscous fluid. For these models, we have derived linearized equations and we provide a novel, straightforward methodology to analyze the experiments. This methodology allowed us to differentiate the effects of the cross-linking proteins in the different regimes of deformation. Our results confirm some previous observations and suggest important relations between the molecular characteristics of the actin-binding proteins and the cell behavior: the effect of myosin is explained in terms of the relation between the lifetime of the bond to actin and the resistive force; the presence of a-actinin obstructs the deformation of the cytoskeleton, presumably mainly due to the higher molecular stiffness and to the lower dissociation rate constants; and filamin contributes critically to the global connectivity of the network, possibly by rapidly turning over crosslinks during the remodeling of the cytoskeletal network, thanks to the higher rate constants, flexibility and larger size. The results suggest a sophisticated relationship between the expression levels of actinbinding proteins, deformability and mechanosensing

Rendimiento y calidades de chapa en clones de chopo a diferentes alturas del fuste

Some major morphological characteristics in relation to log yield in plywood industries were studied in 13 poplar clones, from Populetum of Zamadueñas (Valladolid). Taper, eccentricity, ovality and bark percentage were analysed. Industrial peeling was made in logs up to 12 m height, analysing the veneer yields and comparing the different quality class among clones at different height levels. Log veneer yields up to 12 m trunk length averaged 60 to 70 % in volume without significant differences among clones. In general, the best performance was found in the middle to lower stem zone. However, clones ‘I-214’, ‘Flevo’, ‘MC’ and ‘PA-1’ maintained their optimum yield even above 10 m height in trunk. ‘Campeador’, ‘I-214’, ‘I-262’, ‘PA-1’ and ‘MC’ showed the best yield and quality performance. ‘Canadá blanco’ and ‘454-40’ have acceptable conditions for this use, but their yield was lower.En 13 clones de chopo, procedentes de una parcela de experimentación ubicada en Zamadueñas (Valladolid), se estudian algunas de las características morfológicas relacionadas con el rendimiento de las trozas para su utilización en la industria del desenrollo. Las variables analizadas han sido: conicidad, excentricidad, elipticidad y porcentaje de corteza. Con las trozas resultantes hasta una altura de 12 m se llevó a cabo una operación industrial de desenrollo, realizándose el estudio del rendimiento y la comparación de las diferentes calidades de chapa obtenidas entre los clones y a diferentes alturas en el tronco. El rendimiento en chapa hasta los 12 m de tronco ha oscilado entre el 60 y el 70 %, en volumen, sin marcadas diferencias entre los clones. En general, el mayor aprovechamiento se produce en la zona media-baja del tronco, pero en algunos casos, el rendimiento óptimo se ha mantenido incluso por encima de los 10 m, como ha ocurrido en los clones ‘I-214’, ‘Flevo’, ‘MC’ y ‘PA-1’. Los clones ‘Campeador’, ‘I-214’, ‘I-262’, ‘PA-1’ y ‘MC’ han sido los que mejor respuesta han manifestado en cuanto a rendimiento y calidad. ‘Canadá blanco’ y ‘454-40’ han dado una calidad aceptable, pero su rendimiento ha sido menor

Material properties of evolutionary diverse spider silks described by variation in a single structural parameter

Spider major ampullate gland silks (MAS) vary greatly in material properties among species but, this variation is shown here to be confined to evolutionary shifts along a single universal performance trajectory. This reveals an underlying design principle that is maintained across large changes in both spider ecology and silk chemistry. Persistence of this design principle becomes apparent after the material properties are defined relative to the true alignment parameter, which describes the orientation and stretching of the protein chains in the silk fiber. Our results show that the mechanical behavior of all Entelegynae major ampullate silk fibers, under any conditions, are described by this single parameter that connects the sequential action of three deformation micromechanisms during stretching: stressing of protein-protein hydrogen bonds, rotation of the ?-nanocrystals and growth of the ordered fraction. Conservation of these traits for over 230 million years is an indication of the optimal design of the material and gives valuable clues for the production of biomimetic counterparts based on major ampullate spider silk

Comparación de la Resistencia mecánica y disipación de energía de la seda de seguridad y de la seda víscida de araña

Las fibras de seda son materiales biológicos estructurales que presentan excelentes propiedades mecánicas. Las fibras de seda del hilo de seguridad producido por las arañas presentan unas propiedades mecánicas sólo superadas –en algunas propiedades– por las fibras sintéticas de altas prestaciones. Estas excelentes propiedades, y el hecho de que la biotecnología permite en la actualidad producir fibras bioinspiradas, fundamentan el interés de estudiar las propiedades de diferentes sedas, relacionando la composición y el comportamiento mecánico. El presente artículo aborda el estudio de las propiedades de los hilos de seda víscida, comparándolos con los hilos de seguridad. Al mismo tiempo se ha estudiado la relación entre las propiedades de los hilos de seda víscida y su situación en las telarañas, con el fin de analizar estas construcciones desde el punto de vista estructural. Los resultados muestran una enorme variabilidad de propiedades dentro de la telaraña, sin correlación con la situación. Además se ha encontrado una sorprendente similitud entre las propiedades mecánicas de ambos hilos

Adaptación transcultural de un cuestionario para medir la calidad de vida de los pacientes con anticoagulación oral

ObjetivoAdaptar a la cultura y el idioma españoles un cuestionario desarrollado para evaluar la calidad de vida de los pacientes con tratamiento anticoagulante oral (TAO) y medir su validezDiseñoEstudio observacional, descriptivo, de validación de un instrumento de medida de calidad de vida relacionada con la salud. Emplazamiento. Atención primaria y atención especializadaParticipantesUn total de 225 pacientes que incluía a todos los pacientes de nuestro centro que utilizan TAO y una muestra consecutiva de pacientes con TAO del servicio de hematología del hospital de referenciaMediciones principalesTraducción directa,traducción inversa y prueba de validez. Análisis factorial y agrupación por dimensiones de los ítems, análisis de la consistencia interna y análisis de correlación ítem-total de la versión definitiva del cuestionario en españolResultadosLa edad media de los pacientes fue de 65 ± 13 años, el 51,1% era mujer y el 45,8% era controlado en atención primaria. En el estudio de validez se realizó un análisis factorial con la extracción de 5 factores que explican el 41,62% del valor total de la varianza y la obtención de una agrupación diferente de la original, con unvalor de alfa de Cronbach global de 0,82 y de 0,56–0,74 en las diferentes dimensiones y análisis de correlación ítem-total con valores estadísticamente significativos, excepto en la pregunta número 29ConclusionesTras realizar la adaptación a la cultura y el idioma españoles de un cuestionario desarrollado para evaluar la calidad de vida de los pacientes con TAO, se ha obtenido un instrumento útil y válido para nuestro entornoObjectiveTo adapt to Spanish culture and language a questionnaire developed to evaluate the quality of life of patients taking oral anticoagulation treatment (OAT) and to measure its validityDesignA descriptive observation study to validate an instrument to measure health-related quality of lifeSettingPrimary and specialist careParticipants225 patients, all the patients at our centre who were on OAT and a consecutive sample of patients on OAT from the referral hospital's haemotology serviceMain measurementsDirect translation, back- translation, and pilot study. Factor analysis and item-dimension grouping, internal consistency analysis and analysis of the item- total correlation of the definitive version of the questionnaire in SpanishResultsMean age was 65 (SD=13 years); 51% were women; 45.8% were monitored in PC. Validity study: factor analysis extracted 5 factors that explained 41.62% of total variance value and obtained a grouping different from the original; Cronbach's alpha was .82 overall and ran from .56 to .74 in the various dimensions; and item-total correlation analysis had statistically significant values,except for question 29ConclusionsAfter adaptation to Spanish culture and language of a questionnaire developed to evaluate the quality of life of patients taking OAT, it was found to be a useful instrument, valid for use in our milie

Sequential origin in the high performance properties of spider dragline silk

Major ampullate (MA) dragline silk supports spider orb webs, combining strength and extensibility in the toughest biomaterial. MA silk evolved ~376 MYA and identifying how evolutionary changes in proteins influenced silk mechanics is crucial for biomimetics, but is hindered by high spinning plasticity. We use supercontraction to remove that variation and characterize MA silk across the spider phylogeny. We show that mechanical performance is conserved within, but divergent among, major lineages, evolving in correlation with discrete changes in proteins. Early MA silk tensile strength improved rapidly with the origin of GGX amino acid motifs and increased repetitiveness. Tensile strength then maximized in basal entelegyne spiders, ~230 MYA. Toughness subsequently improved through increased extensibility within orb spiders, coupled with the origin of a novel protein (MaSp2). Key changes in MA silk proteins therefore correlate with the sequential evolution high performance orb spider silk and could aid design of biomimetic fibers

Persistence and variation in microstructural design during the evolution of spider silk

The extraordinary mechanical performance of spider dragline silk is explained by its highly ordered microstructure and results from the sequences of its constituent proteins. This optimized microstructural organization simultaneously achieves high tensile strength and strain at breaking by taking advantage of weak molecular interactions. However, elucidating how the original design evolved over the 400 million year history of spider silk, and identifying the basic relationships between microstructural details and performance have proven difficult tasks. Here we show that the analysis of maximum supercontracted single spider silk fibers using X ray diffraction shows a complex picture of silk evolution where some key microstructural features are conserved phylogenetically while others show substantial variation even among closely related species. This new understanding helps elucidate which microstructural features need to be copied in order to produce the next generation of biomimetic silk fibers

Pressure-Driven Metallization in Hafnium Diselenide

The quest for new transition metal dichalcogenides (TMDs) with outstanding electronic properties operating at ambient conditions draws us to investigate the 1T-HfSe2 polytype under hydrostatic pressure. Diamond anvil cell (DAC) devices coupled to in- situ synchrotron X-ray, Raman and optical (VIS-NIR) absorption experiments along with density functional theory (DFT) based calculations prove that: (i) bulk 1T-HfSe2 exhibits strong structural and vibrational anisotropies, being the interlayer direction especially sensitive to pressure changes, (ii) the indirect gap of 1T-HfSe2 trend to vanish by a -0.1 eV/GPa pressure rate, slightly faster than MoS2 or WS2, (iii) the onset of the metallic behavior appears at Pmet ~10 GPa, which is to date the lowest pressure among common TMDs, and finally (iv) the electronic transition is explained by the bulk modulus B0-Pmet correlation, along with the pressure coefficient of the band gap, in terms of the electronic overlap between chalcogenide p-type and metal d-type orbitals

Highs and Lows of Bond Lengths: Is There Any Limit?

Two distinct points on the potential energy curve (PEC) of a pairwise interaction, the zero-energy crossing point and the point where the stretching force constant vanishes, allow us to anticipate the range of possible distances between two atoms in diatomic, molecular moieties and crystalline systems. We show that these bond-stability boundaries are unambiguously defined and correlate with topological descriptors of electron-density-based scalar fields, and can be calculated using generic PECs. Chemical databases and quantum-mechanical calculations are used to analyze a full set of diatomic bonds of atoms from the s-p main block. Emphasis is placed on the effect of substituents in C-C covalent bonds, concluding that distances shorter than 1.14 Å or longer than 2.0 Å are unlikely to be achieved, in agreement with ultra-high-pressure data and transition-state distances, respectively. Presumed exceptions are used to place our model in the correct framework and to formulate a conjecture for chained interactions, which offers an explanation for the multimodal histogram of O-H distances reported for hundreds of chemical systems

The Glial Regenerative Response to Central Nervous System Injury Is Enabled by Pros-Notch and Pros-NFκB Feedback

Organisms are structurally robust, as cells accommodate changes preserving structural integrity and function. The molecular mechanisms underlying structural robustness and plasticity are poorly understood, but can be investigated by probing how cells respond to injury. Injury to the CNS induces proliferation of enwrapping glia, leading to axonal re-enwrapment and partial functional recovery. This glial regenerative response is found across species, and may reflect a common underlying genetic mechanism. Here, we show that injury to the Drosophila larval CNS induces glial proliferation, and we uncover a gene network controlling this response. It consists of the mutual maintenance between the cell cycle inhibitor Prospero (Pros) and the cell cycle activators Notch and NFκB. Together they maintain glia in the brink of dividing, they enable glial proliferation following injury, and subsequently they exert negative feedback on cell division restoring cell cycle arrest. Pros also promotes glial differentiation, resolving vacuolization, enabling debris clearance and axonal enwrapment. Disruption of this gene network prevents repair and induces tumourigenesis. Using wound area measurements across genotypes and time-lapse recordings we show that when glial proliferation and glial differentiation are abolished, both the size of the glial wound and neuropile vacuolization increase. When glial proliferation and differentiation are enabled, glial wound size decreases and injury-induced apoptosis and vacuolization are prevented. The uncovered gene network promotes regeneration of the glial lesion and neuropile repair. In the unharmed animal, it is most likely a homeostatic mechanism for structural robustness. This gene network may be of relevance to mammalian glia to promote repair upon CNS injury or disease