The touch and zap method for in vivo whole-cell patch recording of intrinsic and visual responses of cortical neurons and Glial cells

Whole-cell patch recording is an essential tool for quantitatively establishing the biophysics of brain function, particularly in vivo. This method is of particular interest for studying the functional roles of cortical glial cells in the intact brain, which cannot be assessed with extracellular recordings. Nevertheless, a reasonable success rate remains a challenge because of stability, recording duration and electrical quality constraints, particularly for voltage clamp, dynamic clamp or conductance measurements. To address this, we describe "Touch and Zap", an alternative method for whole-cell patch clamp recordings, with the goal of being simpler, quicker and more gentle to brain tissue than previous approaches. Under current clamp mode with a continuous train of hyperpolarizing current pulses, seal formation is initiated immediately upon cell contact, thus the "Touch". By maintaining the current injection, whole-cell access is spontaneously achieved within seconds from the cell-attached configuration by a self-limited membrane electroporation, or "Zap", as seal resistance increases. We present examples of intrinsic and visual responses of neurons and putative glial cells obtained with the revised method from cat and rat cortices in vivo. Recording parameters and biophysical properties obtained with the Touch and Zap method compare favourably with those obtained with the traditional blind patch approach, demonstrating that the revised approach does not compromise the recorded cell. We find that the method is particularly well-suited for whole-cell patch recordings of cortical glial cells in vivo, targeting a wider population of this cell type than the standard method, with better access resistance. Overall, the gentler Touch and Zap method is promising for studying quantitative functional properties in the intact brain with minimal perturbation of the cell's intrinsic properties and local network. Because the Touch and Zap method is performed semi-automatically, this approach is more reproducible and less dependent on experimenter technique

Antinumerolagia

Abstract not availabl

HIERRO Y ACERO. TECNOLOGÍA HISTÓRICA Y METAL EN LAS ESPADAS

Ciclo de Conferencias "Embajadores" del CENIMLa arqueometalurgia es la ciencia que estudia los metales históricos y arqueológicos con el fin de extraer información sobre el pasado. El objetivo es relacionar los materiales metálicos del Patrimonio Histórico con el contexto humano, social y cultural que los rodeaba originariamente. Es decir, que nos permite conectar el objeto histórico con las personas que lo diseñaron, lo fabricaron y lo utilizaron. En este sentido, el armamento antiguo constituye un objeto de estudio provisto de un enorme interés tecnológico por la alta exigencia mecánica que tenía la actividad del combate sobre los materiales involucrados. Armas y armaduras constituyen una interesante fuente de información sobre cómo se resolvían complejos problemas técnicos con los medios disponibles. Esto nos ayuda a entender mejor los mecanismos de toma de decisiones en el campo de la tecnología, que tienen mucho que ver con cómo nos relacionamos con nuestro entorno en nuestros intentos por modificarlo, lo cual constituye una de las características fundamentales del pensamiento humano. La charla, de carácter divulgativa, está orientada a explicar la fabricación del armamento en la antigüedad, centrándonos en el caso de las espadas. Estas son objetos históricos que no solo poseen un gran interés tecnológico por la exigencia de su uso, sino que también poseen una enorme carga emocional, al tratarse de símbolos arraigados profundamente en nuestro subconsciente cultural. Se plantean los problemas asociados a las exigencias físicas de estas armas y como la tecnología encuentra soluciones a estos problemas, en un paralelo didáctico de como hoy en día la investigación en materiales encuentra soluciones a nuestros problemas cotidianos.N

Towards an Improved Understanding of Biogeochemical Processes Across Surface-Groundwater Interactions in Intermittent Rivers and Ephemeral Streams

Surface-groundwater interactions in intermittent rivers and ephemeral streams (IRES), waterways which do not flow year-round, are spatially and temporally dynamic because of alternations between flowing, non-flowing and dry hydrological states. Interactions between surface and groundwater often create mixing zones with distinct redox gradients, potentially driving high rates of carbon and nutrient cycling. Yet a complete understanding of how underlying biogeochemical processes across surface-groundwater flowpaths in IRES differ among various hydrological states remains elusive. Here, we present a conceptual framework relating spatial and temporal hydrological variability in surface water-groundwater interactions to biogeochemical processing hotspots in IRES. We combine a review of theIRES biogeochemistry literature with concepts of IRES hydrogeomorphology to: (i) outline common distinctions among hydrological states in IRES; (ii) use these distinctions, together with considerations of carbon, nitrogen, and phosphorus cycles within IRES, to predict the relative potential for biogeochemical processing across different reach-scale processing zones (flowing water, fragmented pools, hyporheic zones, groundwater, and emerged sediments); and (iii) explore the potential spatial and temporal variability of carbon and nutrient biogeochemical processing across entire IRES networks. Our approach estimates the greatest reach-scale potential for biogeochemical processing when IRES reaches are fragmented into isolated surface water pools, and highlights the potential of relatively understudied processing zones, such as emerged sediments. Furthermore, biogeochemical processing in fluvial networks dominated by IRES is likely more temporally than spatially variable. We conclude that biogeochemical research in IRES would benefit from focusing on interactions between different nutrient cycles, surface-groundwater interactions in non-flowing states, and consideration of fluvial network architecture. Our conceptual framework outlines opportunities to advance studies and expand understanding of biogeochemistry in IRES

Effects of flow discontinuities on carbon gas fluxes in a Mediterranean fluvial network = Efecte de les dicontinuitats hidrològiques sobre els fluxes gasosos de carboni en una xarxa fluvial Mediterrània

[eng] Inland waters are active components of the global carbon (C) cycle that transform, store and outgas more than half of the C they receive from adjacent terrestrial ecosystems. However, fundamental uncertainties regarding the spatiotemporal patterns, controls and sources of C gas fluxes in fluvial networks still exist. For instance, current biogeochemical models addressing C transport and processing in fluvial networks from a continuous perspective, do not integrate the effects of local discontinuities such as river impoundment or stream flow intermittency on the dynamics of C gas fluxes. The present dissertation aims to examine how flow discontinuities (i.e., river impoundment, flow fragmentation and drying) shape the spatiotemporal patterns, the controls and the sources of C gas fluxes in a Mediterranean fluvial network. The study was performed from December 2012 to March 2015 in the Fluvià river (NE Iberian Peninsula), characterized by a high density of impounded waters associated to small water retention structures (SWRS; i.e., weirs and small to very small impoundments with surface area < 0.1 km2 and a volume < 0.2 hm3) as well as fragmented river sections dominated by isolated water pools and dry riverbeds coinciding with dry periods. Results of this dissertation show that river discontinuities associated to SWRS and flow intermittency modulate the spatiotemporal patterns, controls and sources of C gas fluxes in the studied fluvial network. However, the magnitude of these effects varied depending on the nature of the discontinuity (i.e., river impoundment or flow intermittency), the type of C gas (i.e., carbon dioxide (CO2) or methane (CH4)) and the hydrological condition (i.e., high or low flow). The presence of SWRS, despite their relatively small water capacity, attenuated the turbulent conditions occurring in free-flowing river sections. As a consequence, the diffusive CO2 emissions from impounded waters were significantly lower than from free-flowing river sections. Contrarily, no reduction in CH4 emissions from impounded river sections associated to the presence of SWRS was detected. This result suggests that the higher internal CH4 production at the impounded river sections, which remained very stable over time, compensated the attenuated physical effect on CH4 emissions. Despite potential inaccuracies in capturing the temporal and spatial heterogeneity, the ebullition was the predominant pathway of CH4 emissions in impounded river sections. Moreover, sources other than internal metabolism (i.e., external inputs, internal geochemical reactions or photochemical mineralization) sustained most of the fluvial network CO2 emissions. Specifically, the magnitude and sources of CO2 emissions depended on flow conditions in the free-flowing sections, whereas they remained relatively stable and independent of hydrological variation in the impounded river sections. The channels of temporary rivers remain as active biogeochemical habitats processing and degassing significant amounts of CO2 to the atmosphere after flow cessation. In contrast, the CH4 efflux from dry beds was undetectable in almost all cases, most likely due to the high aeration limiting the redox requirements for microbial CH4 production. Our results also suggest that the source of CO2 emitted from dry riverbeds remains unclear, although CO2 produced from biological mineralization of fresh and labile organic matter fractions could be an important source. Future hydrological scenarios considering the combined effects of climate change and human pressures on water resources in the Mediterranean regions show the rather low sensitivity of the annual CO2, CH4 and total C emissions to shifts in river discharge. In contrast, they stress the high sensitivity of annual CH4 and total C emissions to shifts in the surface area of lentic waterbodies associated to SWRS. Overall, the main findings of this dissertation point to the need for a shift away from a continuous and system-centric view to a more inclusive approach that incorporates spatiotemporal discontinuities (i.e., SWRS and flow fragmentation and drying) as a suitable framework to understand the dynamics of C gas fluxes in fluvial networks.[cat] Les aigües continentals són uns components molt actius en cicle del carboni (C). Aquests, transformen, emmagatzemen i emeten la meitat de C que reben dels ecosistemes terrestres adjacents. No obstant, encara existeix una elevada incertesa pel que fa als patrons espaciotemporals, factors de control i principals fonts dels fluxos gasosos de C en xarxes fluvials. Els resultats d’aquesta tesi mostren que les estructures de retenció d’aigua de mida petita (ERMP), les quals són molt comuns en rius Mediterranis, van atenuar les condicions turbulents que caracteritzen les seccions del riu amb aigües corrents. Com a conseqüència, les emissions difusives de CO2 des d’aigües represades van ser inferiors a aquells des d’aigües corrents. Contràriament, la presència de ERMP no va suposar un efecte negatiu sobre les emissions de CH4. Tanmateix, fonts diferents al metabolisme intern (això és, entrades externes i reaccions geoquímiques o fotoquímiques internes) van sostenir les emissions de CO2 de la xarxa fluvial. La magnitud i fonts d’aquestes van dependre de les condicions hidrològiques en el cas dels trams d’aigües corrents, mentre que es van mantenir relativament estables i independents de la hidrologia en aquelles seccions de riu reprssades. Les lleres dels rius intermitents romanen actives pel que fa al processat i emissió de CO2 a l’atmosfera una vegada el flux superficial d’aigua cessa. Per contra, el flux d’emissió de CH4 des de les lleres seques va ser indetectable en gairebé tots els casos, probablement degut a les condicions d’alta aeració que limiten els requisits redox per a la producció microbiana de CH4. El flux d’emissió de CO2 des de les lleres seques va doblar a l’emès des de les lleres amb aigües corrents i va ser comparable a l’emès des dels sòls terrestres adjacents. No obstant, les lleres seques i els sòls terrestres adjacents van resultar ser mol diferents des d’un punt de vista fisicoquímic, mostrant així diferències en els principals factors i fonts que en regulen les emissions de CO2. En resum, les principals troballes fetes en aquesta tesi apunten cap a una necessitat clara de substituir els models continus i limitats espacialment per aquells models que incorporen discontinuïtats espaciotemporals (això és, represament del riu o intermitència del règim hidrològic) per tal d’entendre en millor mesura les dinàmiques dels fluxos gasos de C en xarxes fluvials