Traitement de la schistosomiase à S. mansoni : quelle alternative au praziquantel ?

Les schistosomiases sont des maladies parasitaires causées par des helminthes du genre Schistosoma (S.) qui touchent 200 millions de personnes dans le monde, mais restent rares chez le voyageur. Contrairement à S. heamatobium, agent de la bilharziose urinaire, S. mansoni, présent en Afrique subsaharienne, en Egypte ainsi qu'aux Antilles, au Surinam et dans le nordest du Brésil, est responsable des formes hépato-intestinales de la maladie. Les larves, vivant en eaux douces contaminées par des selles infectées, peuvent pénétrer la peau des baigneurs sans que l'individu ne s'en rende compte. Les parasites adultes s'établissent dans le système veineux digestif où ils se reproduisent et excrètent des oeufs qui migreront dans la lumière intestinale. Cette revue systématique évalue les effets des médicaments antibilharziens, utilisés seuls ou en association, pour traiter l'infection à S. mansoni

The roles of poly(ADP-ribose)-metabolizing enzymes in alkylation-induced cell death

Abstract.: Poly(ADP-ribose) (PAR) has been identified as a DNA damage-inducible cell death signal upstream of apoptosis-inducing factor (AIF). PAR causes the translocation of AIF from mitochondria to the nucleus and triggers cell death. In living cells, PAR molecules are subject to dynamic changes pending on internal and external stress factors. Using RNA interference (RNAi), we determined the roles of poly(ADP-ribose) polymerases-1 and -2 (PARP-1, PARP-2) and poly(ADP-ribose) glycohydrolase (PARG), the key enzymes configuring PAR molecules, in cell death induced by an alkylating agent. We found that PARP-1, but not PARP-2 and PARG, contributed to alkylation-induced cell death. Likewise, AIF translocation was only affected by PARP-1. PARP-1 seems to play a major role configuring PAR as a death signal involving AIF translocation regardless of the death pathway involve

Evolution of white dwarfs as a probe of theories of gravitation: the case of Brans-Dicke

Theories with varying gravitational constant G have long been studied. Among them, the most promising candidates as alternatives to standard general relativity are known as scalar–tensor theories. They are consistent descriptions of the observed Universe as well as the low-energy limit of several pictures of unified interactions. Thus, increasing interest in the astrophysical, gravitational wave and pulsar evolution consequences of such theories has been sparked over the last few years. In this work we study the evolution of white dwarf stars in the framework of the simplest model of scalar–tensor theory: Brans–Dicke gravity. We assume that the star is able to see the cosmological evolution of G (obtained from relativistic equations) while adopting a Newtonian model for describing its structure. This allows us to determine how the G variation affects the energetics of the stellar interior. The white dwarfs are analysed employing a well-tested computer code, with state-of-the-art data for the equation of state, opacities, neutrinos, etc.; all these characteristics are carefully described in the text. We compute the theoretical white dwarf luminosity function and use previous observational data to compare with and extract conclusions on the feasibility of the gravitational theory analysed. We find several striking results. The cooling of white dwarfs is strongly accelerated, particularly for massive stars and low luminosities, even if the Ο parameter of Brans–Dicke theory is big enough to accord well with any other test of gravitation. This uncommon cooling process translates into several distinctive features of white dwarf evolution, among which are (a) a new profile of luminosity versus fractional mass and age, (b) different central temperature versus surface luminosity, (c) low masses of progenitors, and most importantly (d) an appreciable variation in the luminosity function. We finally analyse the possibilities of, when precise data with unique interpretation are available, converting this into a powerful new test of gravitation.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Física La Plat

Using News Abstracts to Represent News Agendas

Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Thermohaline mixing and the photospheric composition of low-mass giant stars

We compute full evolutionary sequences of red giant branch stars close to the luminosity bump by including state of the art composition transport prescriptions for the thermohaline mixing regimes. In particular we adopt a self-consistent double-diffusive convection theory, that allows to handle the instabilities that arise when thermal and composition gradients compete against each other, and a very recent empirically motivated and parameter free asymptotic scaling law for thermohaline composition transport. In agreement with previous works, we find that during the red giant stage, a thermohaline instability sets in shortly after the hydrogen burning shell (HBS) encounters the chemical discontinuity left behind by the first dredge-up. We also find that the thermohaline unstable region, initially appearing at the exterior wing of the HBS, is unable to reach the outer convective envelope, with the consequence that no mixing of elements that produces a non-canonical modification of the stellar surface abundances occurs. Also in agreement with previous works, we find that by artificially increasing the mixing efficiency of thermohaline regions it is possible to connect both unstable regions, thus affecting the photospheric composition. However, we find that in order to reproduce the observed abundances of red giant branch stars close to the luminosity bump, thermohaline mixing efficiency has to be artificially increased by about 4 orders of magnitude from that predicted by recent 3D numerical simulations of thermohaline convection close to astrophysical environments. From this we conclude the chemical abundance anomalies of red giant stars cannot be explained on the basis of thermohaline mixing alone.Comment: 7 pages, 6 figures, accepted for publication in A&

Revisiting the theoretical DBV (V777 Her) instability strip: the MLT theory of convection

We reexamine the theoretical instability domain of pulsating DB white dwarfs (DBV or V777 Her variables). We performed an extensive $g$-mode nonadiabatic pulsation analysis of DB evolutionary models considering a wide range of stellar masses, for which the complete evolutionary stages of their progenitors from the ZAMS, through the thermally pulsing AGB and born-again phases, the domain of the PG1159 stars, the hot phase of DO white dwarfs, and then the DB white dwarf stage have been considered. We explicitly account for the evolution of the chemical abundance distribution due to time-dependent chemical diffusion processes. We examine the impact of the different prescriptions of the MLT theory of convection and the effects of small amounts of H in the almost He-pure atmospheres of DB stars on the precise location of the theoretical blue edge of the DBV instability strip.Comment: Proceedings, 16th European White Dwarf Workshop, Barcelona, 200

New fully evolutionary models for asteroseismology of ultra-massive white dwarf stars

Ultra-massive hydrogen-rich (DA spectral type) white dwarf (WD) stars ($M_{\star} > 1M_{\odot}$) coming from single-star evolution are expected to harbor cores made of $^{16}$O and $^{20}$Ne, resulting from semi-degenerate carbon burning when the progenitor star evolves through the super asymptotic giant branch (S-AGB) phase. These stars are expected to be crystallized by the time they reach the ZZ Ceti instability strip ($T_{\rm eff} \sim 12\,500$ K). Theoretical models predict that crystallization leads to a separation of $^{16}$O and $^{20}$Ne in the core of ultra-massive WDs, which impacts their pulsational properties. This property offers a unique opportunity to study the processes of crystallization. Here, we present the first results of a detailed asteroseismic analysis of the best-studied ultra-massive ZZ Ceti star BPM~37093. As a second step, we plan to repeat this analysis using ultra-massive DA WD models with C/O cores in order to study the possibility of elucidating the core chemical composition of BPM~37093 and shed some light on its possible evolutionary origin. We also plan to extend this kind of analyses to other stars observed from the ground and also from space missions like Kepler and TESS.Comment: 4 pages, 2 tables, 2 figures, poster contribution at the conference "Stars and their variability observed from space - Celebrating the 5th anniversary of BRITE-Constellation", Vienna, Austria, August 19 - 23, 2019. Eds: C. Neiner, W. Weiss, D. Baade, E. Griffin, C. Lovekin, A. Moffa