From space to Earth: advances in human physiology from 20 years of bed rest studies (1986–2006)

Bed rest studies of the past 20 years are reviewed. Head-down bed rest (HDBR) has proved its usefulness as a reliable simulation model for the most physiological effects of spaceflight. As well as continuing to search for better understanding of the physiological changes induced, these studies focused mostly on identifying effective countermeasures with encouraging but limited success. HDBR is characterised by immobilization, inactivity, confinement and elimination of Gz gravitational stimuli, such as posture change and direction, which affect body sensors and responses. These induce upward fluid shift, unloading the body’s upright weight, absence of work against gravity, reduced energy requirements and reduction in overall sensory stimulation. The upward fluid shift by acting on central volume receptors induces a 10–15% reduction in plasma volume which leads to a now well-documented set of cardiovascular changes including changes in cardiac performance and baroreflex sensitivity that are identical to those in space. Calcium excretion is increased from the beginning of bed rest leading to a sustained negative calcium balance. Calcium absorption is reduced. Body weight, muscle mass, muscle strength is reduced, as is the resistance of muscle to insulin. Bone density, stiffness of bones of the lower limbs and spinal cord and bone architecture are altered. Circadian rhythms may shift and are dampened. Ways to improve the process of evaluating countermeasures—exercise (aerobic, resistive, vibration), nutritional and pharmacological—are proposed. Artificial gravity requires systematic evaluation. This review points to clinical applications of BR research revealing the crucial role of gravity to health

Evaluación del modelo de medición de factores de riesgo psicosocial en el sector informal urbano en Bogotá, 2015

Este estudio tiene el objetivo de evaluar el modelo de medición de factores de riesgo psicosocial- FRP en el trabajo implementado en Colombia, para el sector informal urbano. Se desarrolla un scoping review (revisión sistemática resumida) para conocer la literatura científica sobre evaluación de FRP en el sector informal, los estudios encontrados tienen diferentes enfoques, entre los más representativos están: lo psicosocial desde los efectos negativos en la salud mental, lo psicosocial incluido en un análisis sociológico de grupos de trabajadores específicos y lo psicosocial analizado como uno de los componentes de las condiciones de trabajo. Igualmente, se presenta un análisis de la Batería de Instrumentos para la Evaluación de FRP, encontrando observaciones sobre: el enfoque de riesgo, el perfil que desarrolla la evaluación, la participación del trabajador en el proceso de evaluación y el papel de los factores extralaborales e individuales en la evaluación. Y finalmente, se valora la pertinencia del modelo a través de la experiencia de (1) expertos en FRP y/o trabajo informal, (2) psicólogos especialistas en salud ocupacional con trayectoria en el tema y (3) trabajadores/as del sector informal urbano de Bogotá, quienes participan en alguna de las siguientes metodologías: encuesta a expertos, grupo focal, entrevista individual o prueba piloto. Los resultados generales del estudio evidencian que el modelo de medición de FRP tiene limitaciones para medir estos factores en el sector informal, por esta razón, se requiere desarrollar un modelo nuevo que se alimente de los avances logrados en el modelo actual de evaluación.Abstract. This study aims to evaluate the model assessment of Psychosocial Risk Factors (PRF) in the work implemented in Colombia, with regard to it´s relevance for the informal sector. To achieve it, takes a scoping review to know the scientific literature about evaluation of PRF in the informal sector. The studies found have different approaches, the most representatives are: the psychosocial, seen from the negative effects in mental health; the psychosocial, included in a sociological analysis of specific groups of workers; and the psychosocial, analyzed as a component of working conditions. The second part is the analysis of the instruments battery to assess the PRF, finding observations on: the risk approach, profile that developed the evaluation, the participation of workers in the assessment process, and the role of the outside work factors and individual factors in the evaluation. And finally, assesses the relevance of model through the experience of (1) PRF or informal work experts, (2) psychologists’ occupational health specialists with experience in the subject, and (3) workers of urban informal sector in Bogotá. They participated in some of the next methodologies: expert survey, focal groups, individual interviews or pilot test. The overall results of the study show the PRF assessment model application limitations to informal sector, for this reason, requires developing a new model based on the progress made in the current assessment model.Maestrí

The Puzzling Conservation and Diversification of Lipid Droplets from Bacteria to Eukaryotes

International audienceMembrane compartments are amongst the most fascinating markers of cell evolution from prokaryotes to eukaryotes, some being conserved and the others having emerged via a series of primary and secondary endosymbiosis events. Membrane compartments comprise the system limiting cells (one or two membranes in bacteria, a unique plasma membrane in eukaryotes) and a variety of internal vesicular, subspherical, tubular, or reticulated organelles. In eukaryotes, the internal membranes comprise on the one hand the general endomembrane system, a dynamic network including organelles like the endoplasmic reticulum, the Golgi apparatus, the nuclear envelope, etc. and also the plasma membrane, which are linked via direct lateral connectivity (e.g. between the endoplasmic reticulum and the nuclear outer envelope membrane) or indirectly via vesicular trafficking. On the other hand, semiautonomous organelles, i.e. mitochondria and chloroplasts, are disconnected from the endomembrane system and request vertical transmission following cell division. Membranes are organized as lipid bilayers in which proteins are embedded. The budding of some of these membranes, leading to the formation of the so-called lipid droplets (LDs) loaded with hydrophobic molecules, most notably triacylglycerol, is conserved in all clades. The evolution of eukaryotes is marked by the acquisition of mitochondria and simple plastids from Gram-positive bacteria by primary endosymbiosis events and the emergence of extremely complex plastids, collectively called secondary plastids, bounded by three to four membranes, following multiple and independent secondary endosymbiosis events. There is currently no consensus view of the evolution of LDs in the Tree of Life. Some features are conserved; others show Josselin Lupette and Eric Maréchal contributed equally with all other contributors