Ctp1CtIP and Rad32Mre11 nuclease activity are required for Rec12Spo11 removal, but Rec12Spo11 removal is dispensable for other MRN-dependent meiotic functions

The evolutionarily conserved Mre11/Rad50/Nbs1 (MRN) complex is involved in various aspects of meiosis. Whereas available evidence suggests that the Mre11 nuclease activity might be responsible for Spo11 removal in Saccharomyces cerevisiae, this has not been confirmed experimentally. This study demonstrates for the first time that Mre11 (Schizosaccharomyces pombe Rad32(Mre11)) nuclease activity is required for the removal of Rec12(Spo11). Furthermore, we show that the CtIP homologue Ctp1 is required for Rec12(Spo11) removal, confirming functional conservation between Ctp1(CtIP) and the more distantly related Sae2 protein from Saccharomyces cerevisiae. Finally, we show that the MRN complex is required for meiotic recombination, chromatin remodeling at the ade6-M26 recombination hot spot, and formation of linear elements (which are the equivalent of the synaptonemal complex found in other eukaryotes) but that all of these functions are proficient in a rad50S mutant, which is deficient for Rec12(Spo11) removal. These observations suggest that the conserved role of the MRN complex in these meiotic functions is independent of Rec12(Spo11) removal.

A Stieltjes approach to static hedges

Static hedging of complicated payoff structures by standard instruments becomes increasingly popular in finance. The classical approach is developed for quite regular functions, while for less regular cases, generalized functions and approximation arguments are used. In this note, we discuss the regularity conditions in the classical decomposition formula due to P. Carr and D. Madan (in Jarrow ed, Volatility, pp. 417–427, Risk Publ., London, 1998) if the integrals in this formula are interpreted as Lebesgue integrals with respect to the Lebesgue measure. Furthermore, we show that if we replace these integrals by Lebesgue–Stieltjes integrals, the family of representable functions can be extended considerably with a direct approach.

A bacterial cytotoxin identifies the RhoA exchange factor Net1 as a key effector in the response to DNA damage.

BACKGROUND: Exposure of adherent cells to DNA damaging agents, such as the bacterial cytolethal distending toxin (CDT) or ionizing radiations (IR), activates the small GTPase RhoA, which promotes the formation of actin stress fibers and delays cell death. The signalling intermediates that regulate RhoA activation and promote cell survival are unknown. PRINCIPAL FINDINGS: We demonstrate that the nuclear RhoA-specific Guanine nucleotide Exchange Factor (GEF) Net1 becomes dephosphorylated at a critical inhibitory site in cells exposed to CDT or IR. Expression of a dominant negative Net1 or Net1 knock down by iRNA prevented RhoA activation, inhibited the formation of stress fibers, and enhanced cell death, indicating that Net1 activation is required for this RhoA-mediated responses to genotoxic stress. The Net1 and RhoA-dependent signals involved activation of the Mitogen-Activated Protein Kinase p38 and its downstream target MAPK-activated protein kinase 2. SIGNIFICANCE: Our data highlight the importance of Net1 in controlling RhoA and p38 MAPK mediated cell survival in cells exposed to DNA damaging agents and illustrate a molecular pathway whereby chronic exposure to a bacterial toxin may promote genomic instability.

Hydrographic Conditions Off Northern Chile During the 1996-1998 La Niña and El Niño Events

The evolution of oceanographic conditions in the upwelling region off northern Chile (18 degrees-24 degrees S) between 1996 and 1998 (including the 1997-1998 El Niño) is presented using hydrographic measurements acquired on quarterly cruises of the Chilean Fisheries Institute, with sea surface temperature (SST), sea level, and wind speeds from Arica (18.5 degrees S), Iquique (20.5 degrees S), and Antofagasta (23.5 degrees S) and a time series of vertical temperature profiles off Iquique. Spatial patterns of sea surface temperature and salinity from May 1996 to March 1997 followed a normal seasonal progression, though conditions were anomalously cool and fresh. Starting in March 1997, positive anomalies in sea level and sea surface temperature propagated along the South American coast to 37 degrees S. Maximum sea level anomalies occurred in two peaks in May-July 1997 and October 1997 to February 1998, separated by a relaxation period. Maximum anomalies (2 degrees C and 0.1 practical salinity units (psu)) extended to 400 m in December 1997 within 50 km of the coast. March 1998 presented the largest surface anomalies (> 4 degrees C and 0.6 psu). Strong poleward flow (20-35 cm s(-1) ) occurred to 400 m or deeper during both sea level maxima and weaker (10 cm s(-1) ) equatorward flow followed each peak. By May 1998, SST had returned to the climatological mean, and flow was equatorward next to the coast. However, offshore salinity remained anomalously high owing to a tongue of subtropical water extending southeast along the Peruvian coast. Conditions off northern Chile returned to normal between August and December 1998. The timing of the anomalies suggests a connection to equatorial waves. The progression of the 1997-1998 El Niño was very similar to that of 1982-1983, though with different timing with respect to seasons.

Seasonal Climatology of Hydrographic Conditions in the Upwelling Region Off Northern Chile

Over 30 years of hydrographic data from the northern Chile (18 degreesS-24 degreesS) upwelling region are used to calculate the surface and subsurface seasonal climatology extending 400 km offshore. The data are interpolated to a grid with sufficient spatial resolution to preserve cross-shelf gradients and then presented as means within four seasons: austral winter (July-September), spring (October-December), summer (January-March), and fall (April-June). Climatological monthly wind forcing, surface temperature, and sea level from three coastal stations indicate equatorward (upwelling favorable) winds throughout the year, weakest in the north. Seasonal maximum alongshore wind stress is in late spring and summer (December-March). Major water masses of the region are identified in climatological T-S plots and their sources and implied circulation discussed. Surface fields and vertical transects of temperature and salinity confirm that upwelling occurs year-round, strongest in summer and weakest in winter, bringing relatively fresh water to the surface nearshore. Surface geostrophic flow nearshore is equatorward throughout the year. During summer, an anticyclonic circulation feature in the north which extends to at least 200 m depth is evident in geopotential anomaly and in both temperature and geopotential variance fields. Subsurface fields indicate generally poleward flow throughout the year, strongest in an undercurrent near the coast. This undercurrent is strongest in summer and most persistent and organized in the south (south of 21 degreesS), A subsurface oxygen minimum, centered at similar to 250 m, is strongest at lower latitudes. Low-salinity subsurface water intrudes into the study area near 100 m, predominantly in offshore regions, strongest during summer and fall and in the southernmost portion of the region. The climatological fields are compared to features off Baja within the somewhat analogous California Current and to measurements from higher latitudes within the Chile-Peru Current system.

Cohort and Gender Differences in Psychosocial Adjustment to Later-Life Widowhood

Objectives. Despite the large body of literature on bereavement, little is known about the impact of sociohistorical context on individual reactions to spousal loss. This study examines the effect of marital status, time period and gender on physical and mental health, and whether reported difficulties following spousal loss differ at 2 distinctive time periods. Method. Two cohorts of older bereaved persons (n = 753) in Switzerland, surveyed in 1979 and 2011, were compared regarding their reports of difficulties related to marital loss. The bereaved spouses were also compared with a group of married contemporaries (n = 1,517) regarding subjective health and depressive symptoms. Results. Marital status and gender each have independent effects on subjective health and depressive symptoms. The effects of widowhood on subjective health differed significantly at both time points. Widowed individuals in 2011, especially women, reported fewer social and financial difficulties than their counterparts in 1979. However, the effect of widowhood on depressive symptoms and psychological difficulties did not differ significantly across time points. Discussion. Social changes in the late 20th century may be protective for older adults’ physical, social, and financial well-being in the face of spousal loss, yet these changes do not alleviate widow(er)s’ psychological distress.

K-t GRAPPA-accelerated 4D flow MRI of liver hemodynamics: influence of different acceleration factors on qualitative and quantitative assessment of blood flow.

OBJECTIVE We sought to evaluate the feasibility of k-t parallel imaging for accelerated 4D flow MRI in the hepatic vascular system by investigating the impact of different acceleration factors. MATERIALS AND METHODS k-t GRAPPA accelerated 4D flow MRI of the liver vasculature was evaluated in 16 healthy volunteers at 3T with acceleration factors R = 3, R = 5, and R = 8 (2.0 × 2.5 × 2.4 mm(3), TR = 82 ms), and R = 5 (TR = 41 ms); GRAPPA R = 2 was used as the reference standard. Qualitative flow analysis included grading of 3D streamlines and time-resolved particle traces. Quantitative evaluation assessed velocities, net flow, and wall shear stress (WSS). RESULTS Significant scan time savings were realized for all acceleration factors compared to standard GRAPPA R = 2 (21-71 %) (p < 0.001). Quantification of velocities and net flow offered similar results between k-t GRAPPA R = 3 and R = 5 compared to standard GRAPPA R = 2. Significantly increased leakage artifacts and noise were seen between standard GRAPPA R = 2 and k-t GRAPPA R = 8 (p < 0.001) with significant underestimation of peak velocities and WSS of up to 31 % in the hepatic arterial system (p <0.05). WSS was significantly underestimated up to 13 % in all vessels of the portal venous system for k-t GRAPPA R = 5, while significantly higher values were observed for the same acceleration with higher temporal resolution in two veins (p < 0.05). CONCLUSION k-t acceleration of 4D flow MRI is feasible for liver hemodynamic assessment with acceleration factors R = 3 and R = 5 resulting in a scan time reduction of at least 40 % with similar quantitation of liver hemodynamics compared with GRAPPA R = 2.

Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko

We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low-activity state. Quasi-coherent, large-amplitude (δ B/B ~ 1), compressional magnetic field oscillations at ~ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied cometary interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pickup-ion-driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

Evolution of 1996-1999 La Niña and El Niño Conditions Off the Western Coast of South America: A Remote Sensing Perspective

We present the evolution of oceanographic conditions off the western coast of South America between 1996 and 1999, including the cold periods of 1996 and 1998-1999 and the 1997-1998 El Niño, using satellite observations of sea level, winds, sea surface temperature (SST), and chlorophyll concentration. Following a period of cold SST and low sea levels in 1996, both were anomalously high between March 1997 and May 1998. The anomalies were greatest between 5 degrees S and 15 degrees S, although they extended beyond 40 degrees S. Two distinct peaks in sea level and SST occurred in June-July 1997 and December 1997 to January 1998, separated by a relaxation period (August-November) of weaker anomalies. Satellite winds were upwelling favorable throughout the time period for most of the region and in fact increased between November 1997 and March 1998 between 5 degrees S and 25 degrees S. Satellite-derived chlorophyll concentrations are available for November 1996 to June 1997 (Ocean Color and Temperature Sensor (OCTS)) and then from October 1997 to present (Sea-viewing Wide Field-of-view Sensor (SeaWiFS)). Near-surface chlorophyll concentrations fell from May to June 1997 and from December 1997 to March 1998. The decrease was more pronounced in northern Chile than off the coast of Peru or central Chile and was stronger for larger cross-shelf averaging bins since nearshore concentrations remained relatively high.

Satellite-Measured Chlorophyll and Temperature Variability Off Northern Chile During the 1996-1998 La Niña and El Niño

Time series of satellite measurements are used to describe patterns of surface temperature and chlorophyll associated with the 1996 cold La Nina phase and the 1997-1998 warm El Nino phase of the El Nino - Southern Oscillation cycle in the upwelling region off northern Chile. Surface temperature data are available through the entire study period. Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data first became available in September 1997 during a relaxation in El Nino conditions identified by in situ hydrographic data. Over the time period of coincident satellite data, chlorophyll patterns closely track surface temperature patterns. Increases both in nearshore chlorophyll concentration and in cross-shelf extension of elevated concentrations are associated with decreased coastal temperatures during both the relaxation in El Nino conditions in September-November 1997 and the recovery from EI Nino conditions after March 1998. Between these two periods during austral summer (December 1997 to March 1998) and maximum El Nino temperature anomalies, temperature patterns normally associated with upwelling were absent and chlorophyll concentrations were minimal. Cross-shelf chlorophyll distributions appear to be modulated by surface temperature frontal zones and are positively correlated with a satellite-derived upwelling index. Frontal zone patterns and the upwelling index in 1996 imply an austral summer nearshore chlorophyll maximum, consistent with SeaWiFS data from I 1998-1999, after the El Nino. SeaWiFS retrievals in the data set used here are higher than in situ measurements by a factor of 2-4; however, consistency in the offset suggests relative patterns are valid.

Enseñanza y Aprendizaje en la Universidad: Representaciones Sociales que construyen los docentes de la Licenciatura en Trabajo Social de la UNaM. 16H360

El presente proyecto pretende continuar con la línea de investigación que se iniciara con el proyecto “La formación en Educación Especial en la UNAM, conceptualizaciones y paradigmas” (16H-157). Posteriormente, “La Formación de Docentes Reflexivos en el Profesorado de Educación Especial: análisis crítico desde la mirada de egresados y estudiantes” (16H-188) y “La Formación de Docentes Críticos y Reflexivos en el Profesorado de Educación Especial: Representaciones Sociales de los Docentes” (16 H 235). Ambos, referidos a la docencia universitaria en ámbitos de la Facultad de Humanidades y Ciencias Sociales, nos posibilitaron conocer aspectos relevantes de la formación profesional docente que se desarrolla a través de la propuesta curricular del Profesorado en Educación Especial. En la presente oportunidad, nuestro eje de indagación se amplía a otra Carrera de la misma Unidad Académica con la intención de abordar las representaciones sociales que construyen los docentes de la Licenciatura en Trabajo Social con relación a las nociones de Enseñanza y Aprendizaje en la Universidad. En tal sentido, por un lado se construirá conocimiento desde una particular mirada hacia las formas que adquiere la vinculación entre enseñanza y aprendizaje, adentrándonos en los posibles modelos construidos sobre la identidad profesional, y por otro, identificar y analizar fundadamente los saberes que circulan en dicho espacio de formación profesional para poder ponerlos en tensión. El interés en el tema se vincula con el anclaje y la trayectoria que posee la citada carrera, habiendo sido una de las fundantes de la Universidad Nacional de Misiones en la Década de 1970. Además, el interés está dado en que desde el año 2010 se encuentra en un proceso de inauguración de un nuevo plan de estudios (Resolución N°002/10), precedido por uno vigente desde 1999 al cual, a su vez, lo precedió la propuesta curricular implementada desde 1982. Los argumentos que dieron lugar al último cambio de Plan de Estudios provinieron de sucesivas evaluaciones, principalmente del claustro docente, al no encontrarse cumplidos los objetivos planteados. A su vez, los resultados alcanzados hasta el momento con la nueva propuesta ya expresan nuevas preocupaciones en el mismo claustro en relación a los resultados que se observan en la formación, tanto en términos cualitativos como en términos cuantitativos, destacándose en el ciclo 2011, por ejemplo, la deserción de alrededor del 50% de los estudiantes inscriptos en cada una de las Asignaturas, según los registros proporcionados por la Dirección Alumnado de la Facultad. Estas cuestiones ya han ido emergiendo desde momentos anteriores y recibieron diferentes tratamientos como ser proyectos de investigación y de extensión, dirigidos tanto hacia los estudiantes, a través de cuestiones vinculadas con la situación de ingreso a la universidad, como hacia los docentes, apuntando a los paradigmas de la profesión y sus relevancias según momentos históricos de la misma. Pero, desde la perspectiva que proponemos en el presente proyecto, es decir, abordando cuestiones propias de la práctica docente y de formación profesional en contextos universitarios, no hallamos en la Carrera antecedentes que lo hayan abordado. Es por ello que, partimos de la necesidad de poner en cuestión las condiciones de producción de las prácticas docentes en la formación de profesionales Licenciados en Trabajo Social en la UNaM. Nuestra propuesta de indagación se fundamenta en cuestiones propias del campo de la docencia universitaria desde donde es posible afirmar que la construcción de lo disciplinar en la formación de profesionales opera en base a modelos, creencias y valores que sustentan los sujetos que participan de la acción de enseñanza, los cuales, por lo general, circulan de modo inconsciente o implícito. De allí que, nos planteamos como principal interrogante: ¿Cuál es el estado de las RS y otros saberes construidos por los sujetos docentes pertenecientes al escenario seleccionado, y cuáles son sus trayectorias profesionales docentes que los habilitan y sostienen, es decir, que los producen y reproducen? Las investigaciones previas desarrolladas por este equipo de trabajo y los hallazgos producidos a través de cada una de ellas, nos indica como apropiado sustentar teórica y metodológicamente esta investigación en los marcos conceptuales desarrollados por Serge Moscovicci y sus seguidores, dado que la Teoría de las Representaciones Sociales constituye un referencial apropiado para la indagación, en tanto permite identificar y analizar a través de los discursos de lo sujetos, los conocimientos, saberes, valores, habilidades, destrezas y actitudes que se ponen en juego en el escenario profesional docente cotidiano. Otros aportes teóricos provienen de las producciones de Alfred Schütz (1993), referidos a la comprensión de la vida de sentido común; de Schön (1992), Carr y Kemmis (1988) referidas a la Articulación Teoría-Práctica; y consideraciones en torno a las nociones de enseñanza y aprendizaje en la Enseñanza Superior de Autores tales como, Brockbank y McGill (2002) y Berstein (1990). Pretendemos con nuestra indagación, en una primera aproximación, reflejar aspectos de la formación profesional en Trabajo Social en el campo de la docencia universitaria, las posibles vinculaciones entre formación docente y sus prácticas, capturando los discursos que circulan en las producciones científicas y académicas actuales. Y, en un segundo momento, formular interrogantes que nos habiliten continuar posteriormente en otro proyecto ahondando las posibles relaciones entre las prácticas de enseñanza y los procesos de aprendizaje que pudieran expresar los estudiantes.