A Reversal in Hair Cell Orientation Organizes Both the Auditory and Vestibular Organs.

Sensory hair cells detect mechanical stimuli with their hair bundle, an asymmetrical brush of actin-based membrane protrusions, or stereocilia. At the single cell level, stereocilia are organized in rows of graded heights that confer the hair bundle with intrinsic directional sensitivity. At the organ level, each hair cell is precisely oriented so that its intrinsic directional sensitivity matches the direction of mechanical stimuli reaching the sensory epithelium. Coordinated orientation among neighboring hair cells usually ensures the delivery of a coherent local group response. Accordingly, hair cell orientation is locally uniform in the auditory and vestibular cristae epithelia in birds and mammals. However, an exception to this rule is found in the vestibular macular organs, and in fish lateral line neuromasts, where two hair cell populations show opposing orientations. This mirror-image hair cell organization confers bidirectional sensitivity at the organ level. Here I review our current understanding of the molecular machinery that produces mirror-image organization through a regional reversal of hair cell orientation. Interestingly, recent evidence suggests that auditory hair cells adopt their normal uniform orientation through a global reversal mechanism similar to the one at work regionally in macular and neuromast organs. Macular and auditory organs thus appear to be patterned more similarly than previously appreciated during inner ear development

Intervenciones en la arquitectura moderna

Las teorías de la arquitectura moderna, sustentadas en ideas de eficiencia técnica, objetividad funcional y representación estética, fueron el sustento de una producción edilicia caracterizada por estructuras tridimensionales de racionalidad numérica que posibilitaron liberar la envolvente de su función portante y por lo tanto generar nuevas definiciones de la forma y el espacio. El edificio de Correos y Telecomunicaciones de la ciudad de Santa Fe, construido en la década de 1950 en el marco del vasto plan de la Dirección de Arquitectura del Ministerio de Comunicaciones de la Nación es un ejemplo de dichas ideas proyectuales. El edificio ha tenido cambios jurisdiccionales y funcionales que colaboraron a acelerar el deterioro material propio del paso del tiempo en el marco de una cultura política descuidada de lo público. Su estudio y análisis permiten abordar las particularidades de producción de la arquitectura moderna en ámbito local y, fundamentalmente, reflexionar acerca de las tensiones implícitas en la intervención del patrimonio moderno debatiéndose entre los fundamentos teóricos y la resultante material. Un trabajo de asistencia técnica realizado desde la FADU UNL, para la documentación y elaboración del proyecto de recuperación del edificio, es la experiencia a partir de la cual se plantean las presentes discusiones técnicas y conceptuales

Construcción de una mirada tecnológica de la historia de la arquitectura y recupero del patrimonio cultural

El trabajo plantea una mirada de la historia de la arquitectura centrada en las persistencias y cambios tecnológicos que posibilitaron pensar y concretar la arquitectura, con el propósito de aportar a buenas prácticas que permitan la recuperación, renovación y construcción del patrimonio cultural. El planteo centra la atención tanto en los procesos que posibilitaron pensar y materializar la obra como en los materiales y sistemas constructivos que viabilizaron su concreción física y que como tales, portan significaciones y han contribuido a generar el ambiente contemporáneo. La técnica es estudiada en su doble aspecto: técnico-racional y expresivo perceptual. Los aspectos técnicos-racionales refieren a materiales, saberes y tecnologías con sus continuidades, rupturas y nuevas concepciones en la ideación de la forma-espacio; los aspectos expresivos-perceptuales refieren a las posibilidades del material y la tecnología en tanto cualidades de textura, color, opacidad, transparencia, etc. y las significaciones que las mismas portan para la determinación del patrimonio. El abordaje desde los materiales y los sistemas de producción de la arquitectura, sistemas tecnológicamente fundados, posibilita realizar una selección de obras y agrupamientos que atienda los vínculos materiales y procedimientos. Un primer agrupamiento se integra a partir de arquitecturas de tierras y/o materiales derivados utilizados con procedimientos artesanales; un segundo agrupamiento se conforma a partir de materiales y procedimientos derivados de avances tecnológicos planteados por la revolución industrial que produjeron rupturas, cambios en las prácticas sociales, espaciales y de producción. El propósito es delinear categorías teóricas para una historiografía de la arquitectura desde la tecnología que contribuya a construir un corpus teórico que aporte saberes para el recupero de la edilicia tradicionalmente reconocida como: colonial, liberal y moderno. Atendiendo que lo liberal y moderno implica reconocer diferentes momentos de avances tecnológicos y por ende, diferentes momentos de la “racionalidad positivista” y de la “subjetividad romántica”, la ponencia presentará precisiones respecto a las categorizaciones planteadas y una propuesta de formación de posgrado realizada a través de cursos denominados “Tecnología y Patrimonio” desarrollados en la FADU-UNL, como instancia de capacitación e investigación, que propone una mirada ampliada de los aspectos que tradicionalmente intervienen en el proyecto de conservación.Tópico 1: Aspectos teóricos, históricos, legales, económicos y tecnológicos de la restauración y conservación de bienes patrimoniales

RGS12 polarizes the GPSM2-GNAI complex to organize and elongate stereocilia in sensory hair cells.

Inhibitory G proteins (GNAI/Gα(i)) bind to the scaffold G protein signaling modulator 2 (GPSM2) to form a conserved polarity complex that regulates cytoskeleton organization. GPSM2 keeps GNAI in a guanosine diphosphate (GDP)-bound state, but how GPSM2-GNAI is generated or relates to heterotrimeric G protein signaling remains unclear. We find that RGS12, a GTPase-activating protein (GAP), is required to polarize GPSM2-GNAI at the hair cell apical membrane and to organize mechanosensory stereocilia in rows of graded heights. Accordingly, RGS12 and the guanine nucleotide exchange factor (GEF) DAPLE are asymmetrically co-enriched at the hair cell apical junction, and Rgs12 mouse mutants are deaf. GPSM2 and RGS12 share GoLoco motifs that stabilize GNAI(GDP), and GPSM2 outcompetes RGS12 to bind GNAI. Our results suggest that polarized GEF/GAP junctional activity might dissociate heterotrimeric G proteins, generating free GNAI(GDP) for GPSM2 at the adjacent apical membrane. GPSM2-GNAI(GDP), in turn, imparts asymmetry to the forming stereocilia to enable sensory function in hair cells

Geochemistry of the Albano and Nemi crater lakes in the volcanic district of Alban Hills

Lake Albano, located 20 km to the SE of Rome, is hosted within the most recent crater of the quiescent Alban Hills volcanic complex that produced hydromagmatic eruptions in Holocene times. Stratigraphic, archaeological and historical evidence indicates that the lake level underwent important variations in the Bronze Age. Before the IV century B.C. several lahars were generated by water overflows from the lake and in the IV century B.C. Romans excavated a drainage tunnel. The lake is located above a buried carbonate horst that contains a pressurized medium-enthalpy geothermal reservoir from which fluids escape to the surface to produce many important gas manifestations of mostly CO2. Previous studies recognized the presence of gas emissions also from the crater bottom. In 1997 the possibility of a Nyos-type event triggered by a lake rollover was considered very low, because the CO2 water concentration at depth was found to be far from saturation. However, considering the high population density nearby, the Italian Civil Protection Department recommended that periodical monitoring be carried out. To this scope we initiated in 2001 a systematic geochemical study of the lake. Thirteen vertical profiles have been repeatedly carried out in 2001–2006, especially in the deepest part of the lake (167 m in 2006), measuring T, pH, dissolved O2 and electrical conductivity. Water samples were collected from various depths and chemically and isotopically analysed. Two similar profiles have been measured also in the nearby Nemi crater lake. Results indicate that in the 4.5 years of monitoring the pressure of gas dissolved in the Lake Albano deep waters remained much lower than the hydrostatic pressure. A CO2 soil survey carried out on the borders of the two lakes, indicates the presence of some zones of anomalous degassing of likely magmatic origin. A water overturn or a heavy mixing of deep and shallow waters likely occurred in winter 2003–2004, when cold rainfall cooled the surface water below 8.5 °C. Such overturns cause only a limited gas exsolution from the lake when the deep water is brought to a few meters depth but can explain the observed decrease with time of dissolved CO2 at depth and related water pH increase. A gas hazard could occur in the case of a sudden injection through the lake bottom of a huge quantity of CO2-rich fluids, which might be caused by earthquake induced fracturing of the rock pile beneath the lake. A limnic gas eruption might also occur should CO2 concentration build up within the lake for a long time

Geochemistry of the Albano and Nemi crater lakes in the volcanic district of Alban Hills (Rome, Italy)

Lake Albano, located 20 km to the SE of Rome, is hosted within the most recent crater of the quiescent Alban Hills volcanic complex that produced hydromagmatic eruptions in Holocene times. Stratigraphic, archaeological and historical evidence indicates that the lake level underwent important variations in the Bronze Age. Before the IV century B.C. several lahars were generated by water overflows from the lake and in the IV century B.C. Romans excavated a drainage tunnel. The lake is located above a buried carbonate horst that contains a pressurized medium-enthalpy geothermal reservoir from which fluids escape to the surface to produce many important gas manifestations of mostly CO2. Previous studies recognized the presence of gas emissions also from the crater bottom. In 1997 the possibility of a Nyos-type event triggered by a lake rollover was considered very low, because the CO2 water concentration at depth was found to be far from saturation. However, considering the high population density nearby, the Italian Civil Protection Department recommended that periodical monitoring be carried out. To this scope we initiated in 2001 a systematic geochemical study of the lake. Thirteen vertical profiles have been repeatedly carried out in 2001-2006, especially in the deepest part of the lake (167m in 2005), measuring T, pH, dissolved O2 and electrical conductivity. Water samples were collected from various depths and chemically and isotopically analysed. Two similar profiles have been measured also in the nearby Nemi crater lake. Results indicate that in the 4.5 years of monitoring the pressure of gas dissolved in the Lake Albano deep waters remained much lower than the hydrostatic pressure. A CO2 soil survey carried out on the borders of the two lakes, indicates the presence of some zones of anomalous degassing of likely magmatic origin. A water overturn or a heavy mixing of deep and shallow waters likely occurred in winter 2003-2004, when cold rainfall cooled the surface water below 8.5 °C. Such overturns cause only a limited gas exsolution from the lake when the deep water is brought to a few meters depth but can explain the observed decrease with time of dissolved CO2 at depth and related water pH increase. A gas hazard could occur in the case of a sudden injection through the lake bottom of a huge quantity of CO2-rich fluids, which might be caused by earthquake induced fracturing of the rock pile beneath the lake. A limnic gas eruption might also occur should CO2 concentration build up within the lake for a long time

Diffuse degassing of carbon dioxide on the NW sector of Colli Albani volcanic complex (Rome, Italy)

Systematic CO2 soil flux surveys at Cava dei Selci on the Colli Albani volcano (28 seasonal surveys since the year 2000) have shown a significant variation of diffuse CO2 release, with a marked decrease, from 25 to 4 tonnes/day, from May 2000 to August 2004, followed by a new increase. Over the same period, CO2 flux halved at S. Maria delle Mole (16.8 tonnes/day in 2000 and 8.3 tonnes/day in 2006). Also the quantity of CO2 dissolved in the deep waters of the Albano crater lake decreased by one order of magnitude in the period 1997-2006. The high CO2 flux values in 2000 could represent the “tail” of a strong degassing episode recorded at Colli Albani in 1995 and related to local earthquakes. The following decrease of CO2 flux could reflect a permeability decrease caused by hydrothermal calcite precipitation favored by PCO2 reduction in the deep sourc

Uncoupling Time and Space in the Collinear Regulation of Hox Genes

During development of the vertebrate body axis, Hox genes are transcribed sequentially, in both time and space, following their relative positions within their genomic clusters. Analyses of animal genomes support the idea that Hox gene clustering is essential for coordinating the various times of gene activations. However, the eventual collinear ordering of the gene specific transcript domains in space does not always require genomic clustering. We analyzed these complex regulatory relationships by using mutant alleles at the mouse HoxD locus, including one that splits the cluster into two pieces. We show that both positive and negative regulatory influences, located on either side of the cluster, control an early phase of collinear expression in the trunk. Interestingly, this early phase does not systematically impact upon the subsequent expression patterns along the main body axis, indicating that the mechanism underlying temporal collinearity is distinct from those acting during the second phase. We discuss the potential functions and evolutionary origins of these mechanisms, as well as their relationship with similar processes at work during limb development

Le antiche stazioni delle ferrovie a Santa Fe. Riflessioni e possibilità di futuro nel mosaico urbano

Santa Fe (Argentina) alla fine del 1880, dopo tre decadi di controversie politiche, sull'onda di un panorama economico internazionale propizio, dà inizio ad un processo di costruzione materiale che si concentra principalmente nella realizzazione delle prime ferrovie, nella promozione all’attività portuale, nello sviluppo di opere di igiene pubblica e nell'apertura di nuove strade; tutte iniziative che concettualmente avevano un forte slancio operativo dal punto di vista della modernizzazione e che consentivano l’inserimento della Regione nel commercio internazionale. L'infrastruttura ferroviaria, e all’interno di essa le stazioni come elementi singolari, risulta essere una scommessa produttiva di scala verso un avvenire della città, proiettando aspettative, generando immagini di un sogno che trovava attuazione nello scenario urbano. La dismissione totale, attorno alla fine del 1990, degli usi delle stazioni ferroviarie e delle relative aree di pertinenza all’interno del consolidato tessuto urbano, ha disegnato un paesaggio in cui le componenti materiali condensano la doppia peculiarità di raccogliere la memoria di una parte costitutiva del divenire storico della città e, allo stesso tempo, aprono la possibilità di attuare interventi di recupero architettonico e assegnazioni di nuovi usi urbani. Gli edifici rappresentativi e funzionali della modernizzazione, le tre stazioni che furono realizzate a Santa Fe, occupavano originariamente lotti localizzati nelle periferie, dove la scacchiera si rompeva, sebbene col tempo l'estensione e il consolidamento del tessuto allargarono il confine urbano, incorporandole come luoghi contigui all’area centrale, con il conseguente cambio di valorizzazione. Le trasformazioni che hanno coinvolto queste aree durante il XX secolo, nel senso fisico e socio-culturale, permettono oggi di avviare una riflessione e di approssimarsi alle problematiche della conservazione del patrimonio industriale argentino da diversi prospettive. La Stazione della Ferrovia Santa Fe (1887) che metteva in comunicazione la città col territorio delle colonie agricole, è stata demolita nel 1965 per dare luogo alla costruzione dell’autostazione. La Stazione della Ferrovia Mitre (1892) e la Stazione della Ferrovia Belgrano (1912-1928), condividono l’avanzato processo di abbandono e degrado, ma non le trasformazioni future previste, come conseguenza delle diverse potenzialità di localizzazione rispetto all’area centrale e dei loro spazi di rappresentazione. Per la stazione Mitre non è previsto ancora un immediato recupero, a causa alla presenza di un contesto ambientale socialmente più compromesso, mentre per la stazione Belgrano, collocata sul tradizionale Boulevard Gálvez della città, è stato avviato un processo di licitazione pubblica per dare inizio al recupero dell'edificio storico e dello spazio contiguo delle ferrovie. Appare chiaro che, sebbene la chiusura dell’attività ferroviaria abbia provocato cambiamenti nel significato di questi edifici, tuttavia il processo di rigenerazione non ha implicato la scomparsa fisica degli elementi della memoria, la cui presenza è in grado ancora oggi di imprimere un alto contenuto di valore a questi vuoti urbani, carichi di significati e al centro della discussione come spazi fondamentali per ripensare e riqualificare l’area centrale della città