Éditeur(s) : HAL CCSD Landes Bioscience
Résumé : International audience
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
Autophagy

hal-00735751
https://hal.archives-ouvertes.fr/hal-00735751
PUBMED : 22966490

Éditeur(s) : HAL CCSD Elsevier
Résumé : In situ analysis of major elements, platinum-group elements and Os isotope composition data for 170 grains of Ru–Os–Ir alloys from podiform chromitites in the Luobusa and Dongqiao ophiolites, Tibet, provide new constraints on the sources of the alloy grains, the Os-isotope composition of the Neo-Tethyan oceanic upper mantle, and the timing of melt–rock reactions in the ultramafic peridotites of the host ophiolites. Most alloy grains are osmiridium and iridosmine. Based on elemental and isotopic compositions, two populations can be identified. Group I, found in both ophiolite bodies, has fractionated PGE patterns typical of alloys and homogeneous 187Os/188Os 0.12645 ± 4 (2s; n = 145). Group II alloys from the Dongqiao ophiolites show smooth PGE patterns and 187Os/188Os ranges from 0.12003 to 0.12194 (yielding Re-depletion ages ≥ 1.1 Ga). Both the PGE patterns and the Os isotopic compositions of Group II resemble those of sulfides residual after melting. Group I alloys represent an early cumulate phase during the crystallization of magmas and are interpreted as derived from an asthenospheric melt. In contrast, Group II alloys are inferred to derive from the breakdown of residual sulfides from the mantle section of the ophiolite, which may represent relics of a sub-continental lithospheric mantle. The coexistence of the two groups of alloys in Dongqiao samples reflects interaction between asthenosphere-derived melts and old depleted lithospheric mantle and suggests that the chromitites originated through melt–rock reactions. The data on the Group I alloys support the hypothesis that the Re–Os evolution of the convective oceanic mantle resembles that of enstatite chondrites.
ISSN: 0012-821X

hal-00404967
https://hal.archives-ouvertes.fr/hal-00404967
DOI : 10.1016/j.epsl.2007.05.044