Oocyte Meiotic Resumption under High Surveillance

Germinal vesicle breakdown (GVBD) is the hallmark of oocyte meiotic resumption. It occurs under minimal stimulation during in vitro maturation (IVM). Several factors have been described to be involved in the inhibition of oocyte meiotic resumption such as purine derivatives. This study was assessing whether adenosinergic and guanosinergic systems are functional and participating in the inhibition of oocyte maturation. The objectives of the present study were to evaluate the effect of two purines, adenosine (ADO) and guanosine (GUO), on in vitro oocyte meiotic resumption, cumulus cell expansion, and gap junction communication. Both ADO and GUO significantly inhibited GVBD oocytes. The inhibitory effect lasted 24 hours and was reversible for meiotic resumption and cumulus cell expansion. Both ADO and GUO increased gap junction communication in cumulus cells. Equine chorionic gonadotropin (eCG) and the adenylyl cyclase stimulator, forskolin (FK), were both supportive of ADO and GUO inhibitory effect. The results are suggesting both adenosinergic and guanosinergic systems efficient in inhibiting oocyte meiotic resumption. The use of these two systems as part of a pre-IVM culture period would be a novel strategy to explore in order to improve oocyte developmental competence

The dynamics of connexin expression, degradation and localisation are regulated by gonadotropins during the early stages of in vitro maturation of swine oocytes

Gap junctional communication (GJC) plays a primordial role in oocyte maturation and meiotic resumption in mammals by directing the transfer of numerous molecules between cumulus cells and the oocyte. Gap junctions are made of connexins (Cx), proteins that regulate GJC in numerous ways. Understanding the dynamic regulation of connexin arrangements during in vitro maturation (IVM) could provide a powerful tool for controlling meiotic resumption and consequently in vitro development of fully competent oocytes. However, physiological events happening during the early hours of IVM may still be elucidated. The present study reports the dynamic regulation of connexin expression, degradation and localization during this stage. Cx43, Cx45 and Cx60 were identified as the main connexins expressed in swine COC. Cx43 and Cx45 transcripts were judged too static to be a regulator of GJC, while Cx43 protein expression was highly responsive to gonadotropins, suggesting that it might be the principal regulator of GJC. In addition, the degradation of Cx43 expressed after 4.5 h of IVM in response to equine chorionic gonadotropin appeared to involve the proteasomal complex. Cx43 localisation appeared to be associated with GJC. Taken together, these results show for the first time that gonadotropins regulate Cx43 protein expression, degradation and localisation in porcine COC during the first several hours of IVM. Regulation of Cx43 may in turn, via GJC, participate in the development of fully competent oocytes

New insight into the role of phosphodiesterase 3A in porcine oocyte maturation

BACKGROUND: The ovulatory surge of gonadotropins triggers oocyte maturation and rupture of the ovarian follicle. The resumption of nuclear maturation in the oocyte from the prophase stage is characterized by germinal vesicle breakdown (GVBD). It has previously been shown that specific inhibition of cAMP degradation by PDE3 prevents the resumption of oocyte meiosis. However, no report has characterized the activity of PDE3 in the porcine oocyte, or the implication of the cAMP-PDE3 pathway in the entire nuclear maturation process. In this study, PDE3 activity in the oocyte was assessed during in vitro maturation (IVM) and the possible roles of the cAMP-PDE3 pathway in the resumption and progression of meiosis were investigated in terms of different models of oocyte maturation. RESULTS: Cyclic AMP-degrading PDE activity was detected in the cumulus-oocyte complex (COC) and was partially inhibited by a specific PDE3 inhibitor, cilostamide. When measured only in the denuded oocyte, PDE activity was almost completely inhibited by cilostamide, suggesting that cAMP-PDE3 activity is the major cAMP-PDE in porcine oocytes. PDE3A mRNA was detected by RT-PCR. PDE3 activity did not vary significantly during the early hours of IVM, but a maximum was observed at 13 hours. In cumulus-oocyte complexes, meiosis resumed after 20.81 hours of culture. PDE3 inhibition no longer maintained meiotic arrest if sustained beyond 17.65 hours of IVM, 3 hours prior to resumption of meiosis. Thereafter, PDE3 inhibition progressively lost its efficacy in GVBD. When the protein phosphatase 1 and 2A inhibitor okadaic acid was continuously or transiently (3 hours) present during IVM, meiosis resumed prematurely; PDE3 inhibition was unable to prevent GVBD. However, PDE3 inhibition in COC treated with OA for 3 hours significantly delayed meiosis at the intermediate stage. CONCLUSION: The present investigation has demonstrated that PDE3A is the major cAMP-degrading PDE in the oocyte. It regulates the resumption of meiosis until 3 hours prior to GVBD and transiently affects meiotic progression

Présence d’un pergélisol würmien sur le piémont des Pyrénées Atlantiques

Des cryoturbations se sont produites sur le sommet de terrasses anciennes sur le piémont nord des Pyrénées. Elles déforment le contact entre une couche de loess wùrmien et les cailloutis altérés sous-jacents. Deux fentes de gel fossiles, sous la zone cryoturbée, indiquent la présence, sous la couche active, d'un pergélisol à plus de 15 km au nord des moraines externes de Lourdes.Cryoturbations developed on top of old terraces of the northern piedmont of the Pyrénées. They deformed the contact between a Wurmian loess and weathered gravels underneath. Two fossil ice wedge casts observed under the cryoturbated layer are indicative of a permafrost of Wurmian age, extending more than 15 km north of the external moraines of Lourdes.Kryturbationen haben an der Oberfläche der alten Terrassen der Bergfussebene der Pyrenaen stattgefunden. Sie haben den Kontakt zwischen einer Lôss-Schicht aus der Wurmeiszeit und dem darunter liegenden verwitterten Gerôll verformt. Zwei fossile Frost-Klùfte unter der kryoturbaten Zone weisen auf das Vorhandensein eines Permafrostbodens unter der aktiven Schicht, mehr als 15 km nôrdlich der externen Morànen von Lourdes

COVID-19, the first pandemic in the post-genomic era.

The scale of the international efforts to sequence SARS-CoV-2 genomes is unprecedented. Early availability of genomes allowed rapid characterisation of the virus, thus kickstarting many highly successful vaccine development programmes. Worldwide genomic resources have provided a good understanding of the pandemic, supported close monitoring of the emergence of viral genomic diversity and pinpointed those sites to prioritise for functional characterisation. Continued genomic surveillance of global viral populations will be crucial to inform the timing of vaccine updates so as to pre-empt the spread of immune escape lineages. While genome sequencing has provided us with an exceptionally powerful tool to monitor the evolution of SARS-CoV-2, there is room for further improvements in particular in the form of less heterogeneous global surveillance and tools to rapidly identify concerning viral lineages

Selfduality for coupled Potts models on the triangular lattice

We present selfdual manifolds for coupled Potts models on the triangular lattice. We exploit two different techniques: duality followed by decimation, and mapping to a related loop model. The latter technique is found to be superior, and it allows to include three-spin couplings. Starting from three coupled models, such couplings are necessary for generating selfdual solutions. A numerical study of the case of two coupled models leads to the identification of novel critical points

Impact de pulvérisations de deltaméthrine dans un foyer de leishmaniose de Bolivie

Une unique pulvérisation domiciliaire de K-Othrine à 0,025 g/m2, en début de saison humide, contrôle efficacement les populations domestiques et péridomestiques de #Lutzomyia longipalpis, le vecteur de la leishmaniose viscérale, dans un village submontagnard de la province Nord-Yungas, Bolivie. Ce phlébotome est éliminé des habitations et des poulaillers durant, respectivement, 9 et 10 mois. Par contre, l'impact des traitements sur #Lu. nuneztovari anglesi, le vecteur présumé de la leishmaniose tégumentaire, est beaucoup moins marqué. Il se traduit, plus par une baisse de 50 % du taux de gorgement des populations capturées dans les maisons, que par une diminution de leur densité, difficile à apprécier du fait des variations saisonnières naturelles, et de l'absence de témoin représentatif. Ce résultat n'est pas inattendu, étant donné la forte exophilie de #Lu. n. anglesi$ dans la région. (Résumé d'auteur

Functional biogeography of oceanic islands and the scaling of functional diversity in the Azores

Analyses of species-diversity patterns of remote islands have been crucial to the development of biogeographic theory, yet little is known about corresponding patterns in functional traits on islands and how, for example, they may be affected by the introduction of exotic species. We collated trait data for spiders and beetles and used a functional diversity index (FRic) to test for nonrandomness in the contribution of endemic, other native (also combined as indigenous), and exotic species to functional-trait space across the nine islands of the Azores. In general, for both taxa and for each distributional category, functional diversity increases with species richness, which, in turn scales with island area. Null simulations support the hypothesis that each distributional group contributes to functional diversity in proportion to their species richness. Exotic spiders have added novel trait space to a greater degree than have exotic beetles, likely indicating greater impact of the reduction of immigration filters and/or differential historical losses of indigenous species. Analyses of species occurring in native-forest remnants provide limited indications of the operation of habitat filtering of exotics for three islands, but only for beetles. Although the general linear (not saturating) pattern of trait-space increase with richness of exotics suggests an ongoing process of functional enrichment and accommodation, further work is urgently needed to determine how estimates of extinction debt of indigenous species should be adjusted in the light of these findings

Does Europe need a comprehensive energy policy?

The nuclear meltdown in Fukushima has given renewed momentum to the anti-nuclear power movement across Europe. However, the degree of momentum varies greatly from country to country, and considering the geographically widespread consequences of a nuclear accident, it hardly appears optimal for one country to ban nuclear power while multiple nuclear power plants are still active in neighbouring countries. Even beyond the nuclear power dilemma, the economic and political externalities associated with energy policy are diffi cult to overstate. The contributions to this Forum look into the benefits expected from a comprehensive common energy policy for Europe and the problems which establishing such a policy would involve

Optimal parameters for the ocean's nutrient, carbon, and oxygen cycles compensate for circulation biases but replumb the biological pump

Accurate predictive modelling of the ocean's global carbon and oxygen cycles is challenging because of uncertainties in both biogeochemistry and ocean circulation. Advances over the last decade have made parameter optimization feasible, allowing models to better match observed biogeochemical fields. However, does fitting a biogeochemical model to observed tracers using a circulation with known biases robustly capture the inner workings of the biological pump? Here we embed a mechanistic model of the ocean's coupled nutrient, carbon, and oxygen cycles into two circulations for the current climate. To assess the effects of biases, one circulation (ACCESS-M) is derived from a climate model and the other from data assimilation of observations (OCIM2). We find that parameter optimization compensates for circulation biases at the expense of altering how the biological pump operates. Tracer observations constrain pump strength and regenerated inventories for both circulations, but ACCESS-M export production optimizes to twice that of OCIM2 to compensate for ACCESS-M having lower sequestration efficiencies driven by less efficient particle transfer and shorter residence times. Idealized simulations forcing complete Southern Ocean nutrient utilization show that the response of the optimized system is sensitive to the embedding circulation. In ACCESS-M, Southern Ocean nutrient and DIC trapping is partially short-circuited by unrealistically deep mixed layers. For both circulations, intense Southern Ocean production deoxygenates Southern-Ocean-sourced deep waters, muting the imprint of circulation biases on oxygen. Our findings highlight that the biological pump's plumbing needs careful assessment to predict the biogeochemical response to environmental changes, even when optimally matching observations.</p