Meiotic Cells Counteract Programmed Retrotransposon Activation via RNA-Binding Translational Repressor Assemblies

International audienceRetrotransposon proliferation poses a threat to germline integrity. While retrotransposons must be activated in developing germ cells in order to survive and propagate, how they are selectively activated in the context of meiosis is unclear. We demonstrate that the transcriptional activation of Ty3/Gypsy retrotransposons and host defense are controlled by master meiotic regulators. We show that budding yeast Ty3/Gypsy co-opts binding sites of the essential meiotic transcription factor Ndt80 upstream of the integration site, thereby tightly linking its transcriptional activation to meiotic progression. We also elucidate how yeast cells thwart Ty3/Gypsy proliferation by blocking translation of the retrotransposon mRNA using amyloid-like assemblies of the RNA-binding protein Rim4. In mammals, several inactive Ty3/Gypsy elements are undergoing domestication. We show that mammals utilize equivalent master meiotic regulators (Stra8, Mybl1, Dazl) to regulate Ty3/Gypsy-derived genes in developing gametes. Our findings inform how genes that are evolving from retrotransposons can build upon existing regulatory networks during domestication

Somatosensory Evoked Potentials suppression due to remifentanil during spinal operations; a prospective clinical study

<p>Abstract</p> <p>Background</p> <p>Somatosensory evoked potentials (SSEP) are being used for the investigation and monitoring of the integrity of neural pathways during surgical procedures. Intraoperative neurophysiologic monitoring is affected by the type of anesthetic agents. Remifentanil is supposed to produce minimal or no changes in SSEP amplitude and latency. This study aims to investigate whether high doses of remifentanil influence the SSEP during spinal surgery under total intravenous anesthesia.</p> <p>Methods</p> <p>Ten patients underwent spinal surgery. Anesthesia was induced with propofol (2 mg/Kg), fentanyl (2 mcg/Kg) and a single dose of cis-atracurium (0.15 mg/Kg), followed by infusion of 0.8 mcg/kg/min of remifentanil and propofol (30-50 mcg/kg/min). The depth of anesthesia was monitored by Bispectral Index (BIS) and an adequate level (40-50) of anesthesia was maintained. Somatosensory evoked potentials (SSEPs) were recorded intraoperatively from the tibial nerve (P37) 15 min before initiation of remifentanil infusion. Data were analysed over that period.</p> <p>Results</p> <p>Remifentanil induced prolongation of the tibial SSEP latency which however was not significant (p > 0.05). The suppression of the amplitude was significant (p < 0.001), varying from 20-80% with this decrease being time related.</p> <p>Conclusion</p> <p>Remifentanil in high doses induces significant changes in SSEP components that should be taken under consideration during intraoperative neuromonitoring.</p

Microbially mediated reduction of FeIII and AsV in Cambodian sediments amended with 13C-labelled hexadecane and kerogen

Microbial activity is generally accepted to play a critical role, with the aid of suitable organic carbon substrates, in the mobilisation of arsenic from sediments into shallow reducing groundwaters. The nature of the organic matter in natural aquifers driving the reduction of AsV to AsIII is of particular importance but is poorly understood. In this study, sediments from an arsenic rich aquifer in Cambodia were amended with two 13C-labelled organic substrates. 13C-hexadecane was used as a model for potentially bioavailable long chain n-alkanes and a 13C-kerogen analogue as a proxy for non-extractable organic matter. During anaerobic incubation for 8 weeks, significant FeIII reduction and AsIII mobilisation were observed in the biotic microcosms only, suggesting that these processes were microbially driven. Microcosms amended with 13C-hexadecane exhibited a similar extent of FeIII reduction to the non-amended microcosms, but marginally higher AsIII release. Moreover, gas chromatography–mass spectrometry analysis showed that 65 % of the added 13C-hexadecane was degraded during the 8-week incubation. The degradation of 13C-hexadecane was microbially driven, as confirmed by DNA stable isotope probing (DNA-SIP). Amendment with 13C-kerogen did not enhance FeIII reduction or AsIII mobilisation, and microbial degradation of kerogen could not be confirmed conclusively by DNA-SIP fractionation or 13C incorporation in the phospholipid fatty acids. These data are, therefore, consistent with the utilisation of long chain n-alkanes (but not kerogen) as electron donors for anaerobic processes, potentially including FeIII and AsV reduction in the subsurface

Impact of oil on bacterial community structure in bioturbated sediments

Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions - with tidal cycles and natural seawater - was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g21 wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria and Deltaproteobacteria. In the oiled-microcosms, the addition of H. diversicolor reduced the phylotype-richness, sequences associated to Actinobacteria, Firmicutes and Plantomycetes were not detected. These observations highlight the influence of the bioturbation on the bacterial community structure without affecting the biodegradation capacities

Tool developments in the OpenMC code: Correlated Sampling and Transient Fission Matrix approach using OpenFOAM CFD mesh

International audienceThis article presents the developments performed to enlarge the application of the OpenMC neutron transport code for thermohydraulics coupling and nuclear data uncertainty propagation. These developments rely firstly on the addition of the Correlated Sampling (CS) technique, which allows to propagate the impact of thermal feedback or cross section sampling on the neutronic calculations thanks to neutron weight modifications. The Correlated Sampling technique is associated here to Computer Aided Design (CAD) based mesh and to the Transient Fission Matrix (TFM) approach. These three elements are used together to allow a global handling of the neutronics-thermohydraulics coupling: the TFM approach deals with the neutron kinetics using a pre-calculation of the neutron transport stored in matrices, the Correlated Sampling technique provides the impact of the thermal feedbacks on the matrices, and the CAD mesh is used to define the volumes associated to each bin of the matrices in order to get the results on the same format as the Computational Fluid Dynamics (CFD) code to be coupled to neutronics, here the OpenFOAM code. Both the implementations and the verifications done are detailed in the article, together with a discussion on the current limitations

Tool developments in the OpenMC code: Correlated Sampling and Transient Fission Matrix approach using OpenFOAM CFD mesh

International audienceThis article presents the developments performed to enlarge the application of the OpenMC neutron transport code for thermohydraulics coupling and nuclear data uncertainty propagation. These developments rely firstly on the addition of the Correlated Sampling (CS) technique, which allows to propagate the impact of thermal feedback or cross section sampling on the neutronic calculations thanks to neutron weight modifications. The Correlated Sampling technique is associated here to Computer Aided Design (CAD) based mesh and to the Transient Fission Matrix (TFM) approach. These three elements are used together to allow a global handling of the neutronics-thermohydraulics coupling: the TFM approach deals with the neutron kinetics using a pre-calculation of the neutron transport stored in matrices, the Correlated Sampling technique provides the impact of the thermal feedbacks on the matrices, and the CAD mesh is used to define the volumes associated to each bin of the matrices in order to get the results on the same format as the Computational Fluid Dynamics (CFD) code to be coupled to neutronics, here the OpenFOAM code. Both the implementations and the verifications done are detailed in the article, together with a discussion on the current limitations

Tool developments in the OpenMC code: Correlated Sampling and Transient Fission Matrix approach using OpenFOAM CFD mesh

International audienceThis article presents the developments performed to enlarge the application of the OpenMC neutron transport code for thermohydraulics coupling and nuclear data uncertainty propagation. These developments rely firstly on the addition of the Correlated Sampling (CS) technique, which allows to propagate the impact of thermal feedback or cross section sampling on the neutronic calculations thanks to neutron weight modifications. The Correlated Sampling technique is associated here to Computer Aided Design (CAD) based mesh and to the Transient Fission Matrix (TFM) approach. These three elements are used together to allow a global handling of the neutronics-thermohydraulics coupling: the TFM approach deals with the neutron kinetics using a pre-calculation of the neutron transport stored in matrices, the Correlated Sampling technique provides the impact of the thermal feedbacks on the matrices, and the CAD mesh is used to define the volumes associated to each bin of the matrices in order to get the results on the same format as the Computational Fluid Dynamics (CFD) code to be coupled to neutronics, here the OpenFOAM code. Both the implementations and the verifications done are detailed in the article, together with a discussion on the current limitations