Cells respond to salt stress by osmolyte synthesis and by increase of K(+) uptake and Na(+) efflux at the plasma membrane and of Na(+) accumulation at the vacuole. This cellular level of response has ...been approached by the molecular genetics of Saccharomyces cerevisiae. Two plasma membrane proteins, Sln1 and Sho1, operate as sensors for turgor loss under mild osmotic stress. They activate the Hog1 MAP kinase which induces several defence genes, including the ENA1 Na(-) -efflux pump. Hog1-mediated induction occurs by inactivation of the Sko1 repressor. High concentrations of Na(+) activate the calcium-dependent protein phosphatase calcineurin, which induces the ENA1 gene via the positive transcription factor Hal8/Crz1/Tcn1. Vacuoles could operate as Na(+) sensors through a Na(+)-Ca(2+) exchange mechanism. The electrical potential of the plasma membrane is a major determinant of the uptake of toxic cations, including Na(-), by non-specific leakage pathways. This biophysical parameter is modulated by the concerted activities of the proton pumping Pma1 ATPase and the Trk1, 2 K(+) uptake system. Both calcineurin and the protein kinase Hal4,5 modulate Trk1,2 and, indirectly, the membrane potential and salt tolerance. The limiting role of vacuolar cation accumulation in salt tolerance has been demonstrated by expression in yeast vacuoles of the bacterial antiporter NhaA.
Este artículo constituye una reflexión sobre las implicaciones de los procesos paradójicos de construcción social de la juventud en la forma de situarse y de ser situados los jóvenes frente al ...mercado de trabajo. La pluralidad de formas de comprender a la juventud puede entenderse como un síntoma de la contradictoria posición del joven frente a un mercado de trabajo segmentado que le aboca a mantener formas plurales, e incluso antitéticas, de ser joven. La precaria situación de la juventud ante el mercado de trabajo requiere definiciones abiertas y plurales con las que gestionar esta compleja y contradictoria posición. Estas prácticas de construcción del objeto epistemológico también pueden entenderse como un factor de explicación de la frágil situación del joven frente al mercado de trabajo. La construcción de una categoría unificadora como la de juventud, definida bajo un carácter deficitario, permite anular un potencial conflicto entre distintos grupos de edad por las desiguales condiciones de acceso al mercado de trabajo. Se discute la importancia de la invención de una categoría como la juvenil en la distribución, justificación y legitimación de posiciones desiguales de los distintos trabajadores frente al mercado de trabajo. /// This paper examines the implications of the paradoxical processes of the social construction of youth in terms of how young people put themselves, and are placed on, the job market. The fact that there are so many different ways of understanding youth can be interpreted as symptomatic of the ambivalent position of young people in terms of a segmented job market which causes them to adopt different and even antithetical forms of "being young". The precarious situation of young people in terms of the labour market requires open and plural definitions with which to tackle this complex and contradictory position. These approaches to constructing the subject of epistemological study can also be interpreted as one way of explaining young people's vulnerability in terms of the labour market. By putting youth into a single category, and stressing its negative character, we can obviate the potential conflict between different age-groups stemming from their unequal conditions of access to the labour market. This paper examines the importance of the invention of a category such as youth in terms of the distribution, justificación and legitimation of unequal positions of the various workers with regard to the labour market.
The purpose of this contribution is to discuss the social and ethical principles underlying the new model of social intervention proposed by these bodies. To promote and place in circulation concepts ...that will fuel public debate is an approach to the achievement of supranational regulation increasingly favoured by the European institutions. Here, in relation to the specific case of activation, we will discuss both the differing ways in which the model is utilised and the effects entailed by its implementation, as well as how it affects the adjudication of responsibilities between the welfare state, workers and employers. A diagnosis of the problem will be proposed and explored, together with possible and legitimate alternatives for its resolution. The activation paradigm posits a transformation of the social and ethical underpinnings of the social contract, requiring us to take up a moral stance in relation to unemployment and social exclusion. It accordingly fosters a change in ideological and terminological presuppositions -in what is taken for granted- as a means of depoliticising the handling of the social conflicts likely to accompany current developments in changing production models, in order to prevent the socio-political nature of social exclusion from emerging. The point is to avoid all consideration of this issue, thereby forestalling any questions of power or oppression that might be raised. PUBLICATION ABSTRACT
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