Polarized cortical tension drives zebrafish epiboly movements

The principles underlying the biomechanics of morphogenesis are largely unknown. Epiboly is an essential embryonic event in which three tissues coordinate to direct the expansion of the blastoderm. How and where forces are generated during epiboly, and how these are globally coupled remains elusive. Here we developed a method, hydrodynamic regression (HR), to infer 3D pressure fields, mechanical power, and cortical surface tension profiles. HR is based on velocity measurements retrieved from 2D+T microscopy and their hydrodynamic modeling. We applied HR to identify biomechanically active structures and changes in cortex local tension during epiboly in zebrafish. Based on our results, we propose a novel physical description for epiboly, where tissue movements are directed by a polarized gradient of cortical tension. We found that this gradient relies on local contractile forces at the cortex, differences in elastic properties between cortex components and the passive transmission of forces within the yolk cell. All in all, our work identifies a novel way to physically regulate concerted cellular movements that might be instrumental for the mechanical control of many morphogenetic processes.Peer ReviewedPostprint (author's final draft

Vitamin A and pregnancy: review of the literature and risk assessment

TeratologíaVitamin A plays a key role in many essential biological processes, such as the embryonic development, regulation of proliferation and diferentiation of many cell types. The present article reviews the biochemistry, metabolism and mode of action of retinoides (including vitamin A), as well as their role in the embryo development and their teratogenic effect on animal and human beings.N

Gas accretion as the origin of chemical abundance gradients in distant galaxies

It has recently been suggested that galaxies in the early Universe can grow through the accretion of cold gas, and that this may have been the main driver of star formation and stellar mass growth. Because the cold gas is essentially primordial, it has a very low abundance of elements heavier than helium (metallicity). As it is funneled to the centre of a galaxy, it will lead the central gas having an overall lower metallicity than gas further from the centre, because the gas further out has been enriched by supernovae and stellar winds, and not diluted by the primordial gas. Here we report chemical abundances across three rotationally-supported star-forming galaxies at z~3, only 2 Gyr after the Big Bang. We find an 'inverse' gradient, with the central, star forming regions having a lower metallicity than less active ones, opposite to what is seen in local galaxies. We conclude that the central gas has been diluted by the accretion of primordial gas, as predicted by 'cold flow' models.Comment: To Appear in Nature Oct 14, 2010; Supplementary Information included her

A multi-step finite-state automaton for arbitrarily deterministic Tsetlin Machine learning

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The activity of the Spanish Teratology Information Services (SITTE and SITE) during year 2011

Otros Resultados: Actividad TraslacionalWe present a summary of the activity of the two Teratology Information Services: SITTE (for health professionals) and SITE (for the general population) during year 2011. The total number of calls received in both services was 5,340 (829 from SITTE and 4,511 from SITE). We also analyzed calls asking for maternal diseases because some of them, like diabetes and hypertension, can be of risk for the correct prenatal development, either by themselves or by the treatment. Like all these previous years, drugs have been the main issue of concern in consulting (68.67% SITTE; 40.84% SITE), particulary about psychoanaleptics (12.71% SITTE; 12.55% SITE) and psycholeptics (12.37% SITTE; 12.90% SITE). Sometimes this concern is the reason for many chronic treatments to be withdrawn when knowing about the pregnancy, without taking into account the risk this may bring to the mother´s illness.N