A six-dimensional compact symplectic solvmanifold without Kahler structures

International audienceThe purpose of this paper is to construct a compact symplectic (non-nilpotent) solvmanifold $M^{6} = \Gamma / G$ of dimension $6$ which does not admit Kähler structures. We show that the minimal model of $M^{6}$ is not formal by proving that there are non-trivial (quadruple) Massey products, however we remark that all the (triple) Massey products of $M^{6}$ vanish

A highly dynamic F-actin network regulates transport and recycling of micronemes in Toxoplasma gondii vacuoles

The obligate intracellular parasite Toxoplasma gondii replicates in an unusual process, described as internal budding. Multiple dausghter parasites are formed sequentially within a single mother cell, requiring replication and distribution of essential organelles such as micronemes. These organelles are thought to be formed de novo in the developing daughter cells. Using dual labelling of a microneme protein MIC2 and super-resolution microscopy, we show that micronemes are recycled from the mother to the forming daughter parasites using a highly dynamic F-actin network. While this recycling pathway is F-actin dependent, de novo synthesis of micronemes appears to be F-actin independent. The F-actin network connects individual parasites, supports long, multidirectional vesicular transport, and regulates transport, density and localisation of micronemal vesicles. The residual body acts as a storage and sorting station for these organelles. Our data describe an F-actin dependent mechanism in apicomplexans for transport and recycling of maternal organelles during intracellular development

TLR4 and NLRP3 Caspase 1- IL-1β- Axis are not Involved in Colon Ascendens Stent Peritonitis (Casp)-Associated Heart Disease

Hemodynamic collapse and myocardial dysfunction are among the major causes ofdeath in severe sepsis. The purpose of this study was to assess the role played by TLR4and by the NLRP3 inflammasome in the cardiac dysfunction that occurs after highgradepolymicrobial sepsis. We performed the colon ascendens stent peritonitis (CASP)surgery in Tlr4-/-, Nlrp3-/- and caspase-1-/- mice. We also assessed for the first time theelectrical heart function in the CASP model. The QJ interval was increased in wild-typeC57BL/6J mice after CASP when compared to sham controls, a result paralleled by anincrease in the cardiac action potential duration (APD). The decreases in ejectionfraction (EF), left-ventricle end diastolic volume (LVEDV), stroke volume, and cardiacoutput found after CASP were similar among all groups of mice. Similar heart responsewas found when Nlrp3-/- mice were submitted to high-grade CLP. Despite developingcardiac dysfunction similar to wild-types after CASP, Nlrp3-/- mice had reducedcirculating levels of IL-1β, IL-6 and TNF-α. Our results demonstrate that the geneticablation of Tlr4, Nlrp3, and caspase-1 does not prevent the cardiac dysfunction, despitepreventing the increase in pro-inflammatory cytokines, indicating that these are notfeasible targets to therapy in high-grade sepsis.Fil: López Alarcón, Maria Micaela. Universidade Federal do Rio de Janeiro; BrasilFil: Fernandez Ruocco, Maria Julieta. Universidade Federal do Rio de Janeiro; BrasilFil: Ferreira, Fabiano. Universidade Federal do Rio de Janeiro; BrasilFil: Paula Neto, Heitor A.. Universidade Federal do Rio de Janeiro; BrasilFil: Sepúlveda, Marisa Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Investigaciones Cardiovasculares ; ArgentinaFil: Vila Petroff, Martin Gerarde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Investigaciones Cardiovasculares ; ArgentinaFil: Carvalho, Adriana Bastos. Universidade Federal do Rio de Janeiro; BrasilFil: Peroba Ramos, Isalira. Universidade Federal do Rio de Janeiro; BrasilFil: Branda, Hugo Justino. Universidade Federal do Rio de Janeiro; BrasilFil: Neto Paiva, Claudia. Universidade Federal do Rio de Janeiro; BrasilFil: Medei, Emiliano. Universidade Federal do Rio de Janeiro; Brasi

A global sampler of single particle tracking solutions for single molecule microscopy.

The dependence on model-fitting to evaluate particle trajectories makes it difficult for single particle tracking (SPT) to resolve the heterogeneous molecular motions typical of cells. We present here a global spatiotemporal sampler for SPT solutions using a Metropolis-Hastings algorithm. The sampler does not find just the most likely solution but also assesses its likelihood and presents alternative solutions. This enables the estimation of the tracking error. Furthermore the algorithm samples the parameters that govern the tracking process and therefore does not require any tweaking by the user. We demonstrate the algorithm on synthetic and single molecule data sets. Metrics for the comparison of SPT are generalised to be applied to a SPT sampler. We illustrate using the example of the diffusion coefficient how the distribution of the tracking solutions can be propagated into a distribution of derived quantities. We also discuss the major challenges that are posed by the realisation of a SPT sampler

Supramolecular clustering of the cardiac sodium channel Nav1.5 in HEK293F cells, with and without the auxiliary β3-subunit.

Voltage-gated sodium channels comprise an ion-selective α-subunit and one or more associated β-subunits. The β3-subunit (encoded by the SCN3B gene) is an important physiological regulator of the heart-specific sodium channel, Nav1.5. We have previously shown that when expressed alone in HEK293F cells, the full-length β3-subunit forms trimers in the plasma membrane. We extend this result with biochemical assays and use the proximity ligation assay (PLA) to identify oligomeric β3-subunits, not just at the plasma membrane, but throughout the secretory pathway. We then investigate the corresponding clustering properties of the α-subunit and the effects upon these of the β3-subunits. The oligomeric status of the Nav1.5 α-subunit in vivo, with or without the β3-subunit, has not been previously investigated. Using super-resolution fluorescence imaging, we show that under conditions typically used in electrophysiological studies, the Nav1.5 α-subunit assembles on the plasma membrane of HEK293F cells into spatially localized clusters rather than individual and randomly dispersed molecules. Quantitative analysis indicates that the β3-subunit is not required for this clustering but β3 does significantly change the distribution of cluster sizes and nearest-neighbor distances between Nav1.5 α-subunits. However, when assayed by PLA, the β3-subunit increases the number of PLA-positive signals generated by anti-(Nav1.5 α-subunit) antibodies, mainly at the plasma membrane. Since PLA can be sensitive to the orientation of proteins within a cluster, we suggest that the β3-subunit introduces a significant change in the relative alignment of individual Nav1.5 α-subunits, but the clustering itself depends on other factors. We also show that these structural and higher-order changes induced by the β3-subunit do not alter the degree of electrophysiological gating cooperativity between Nav1.5 α-subunits. Our data provide new insights into the role of the β3-subunit and the supramolecular organization of sodium channels, in an important model cell system that is widely used to study Nav channel behavior.We would like to thank the Gurdon Institute Imaging Facility for use of their microscope and general assistance. This work was supported by a British Heart Foundation grant (PG/14/79/31102) to APJ and CLHH, The Wellcome Trust, award number: 105727/Z/14/Z to CLHH and a Medical Research Council grant (MR/K015591/1) to CLF, RAL, and STFC

Resolving the effect of oxygen vacancies on Co nanostructures using soft XAS/X-PEEM

Improving both the extent of metallic Co nanoparticle (Co NP) formation and their stability is necessary to ensure good catalytic performance, particularly for Fischer–Tropsch synthesis (FTS). Here, we observe how the presence of surface oxygen vacancies (Ovac) on TiO2 can readily reduce individual Co3O4 NPs directly into CoO/Co0 in the freshly prepared sample by using a combination of X-ray photoemission electron microscopy (X-PEEM) coupled with soft X-ray absorption spectroscopy. The Ovac are particularly good at reducing the edge of the NPs as opposed to their center, leading to smaller particles being more reduced than larger ones. We then show how further reduction (and Ovac consumption) is achieved during heating in H2/syngas (H2 + CO) and reveal that Ovac also prevents total reoxidation of Co NPs in syngas, particularly the smallest (∼8 nm) particles, thus maintaining the presence of metallic Co, potentially improving catalyst performance

High thyrotropin is critical for cardiac electrical remodeling and arrhythmia vulnerability in hypothyroidism

Background: Hypothyroidism, the most common endocrine disease, induces cardiac electrical remodeling that creates a substrate for ventricular arrhythmias. Recent studies report that high thyrotropin (TSH) levels are related to cardiac electrical abnormalities and increased mortality rates. The aim of the present work was to investigate the direct effects of TSH on the heart and its possible causative role in the increased incidence of arrhythmia in hypothyroidism. Methods: A new rat model of central hypothyroidism (low TSH levels) was created and characterized together with the classical propylthiouracil-induced primary hypothyroidism model (high TSH levels). Electrocardiograms were recorded in vivo, and ionic currents were recorded from isolated ventricular myocytes in vitro by the patch-clamp technique. Protein and mRNA were measured by Western blot and quantitative reverse transcription polymerase chain reaction in rat and human cardiac myocytes. Adult human action potentials were simulated in silico to incorporate the experimentally observed changes. Results: Both primary and central hypothyroidism models increased the L-type Ca2+ current (ICa-L) and decreased the ultra-rapid delayed rectifier K+ current (IKur) densities. However, only primary but not central hypothyroidism showed electrocardiographic repolarization abnormalities and increased ventricular arrhythmia incidence during caffeine/dobutamine challenge. These changes were paralleled by a decrease in the density of the transient outward K+ current (Ito) in cardiomyocytes from animals with primary but not central hypothyroidism. In vitro treatment with TSH for 24 hours enhanced isoproterenol-induced spontaneous activity in control ventricular cells and diminished Ito density in cardiomyocytes from control and central but not primary hypothyroidism animals. In human myocytes, TSH decreased the expression of KCND3 and KCNQ1, Ito, and the delayed rectifier K+ current (IKs) encoding proteins in a protein kinase A–dependent way. Transposing the changes produced by hypothyroidism and TSH to a computer model of human ventricular action potential resulted in enhanced occurrence of early afterdepolarizations and arrhythmia mostly in primary hypothyroidism, especially under b-adrenergic stimulation. Conclusions: The results suggest that suppression of repolarizing K+ currents by TSH underlies most of the electrical remodeling observed in hypothyroidism. This work demonstrates that the activation of the TSHreceptor/protein kinase A pathway in the heart is responsible for the cardiac electrical remodeling and arrhythmia generation seen in hypothyroidism.Fil: Fernandez Ruocco, Maria Julieta. Universidade Federal do Rio de Janeiro; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Gallego, Monica. Universidad del País Vasco; EspañaFil: Rodriguez de Yurre, Ainhoa. Universidade Federal do Rio de Janeiro; Brasil. Universidad del País Vasco; EspañaFil: Zayas Arrabal, Julian. Universidad del País Vasco; EspañaFil: Echeazarra, Leyre. Universidade Federal do Rio de Janeiro; BrasilFil: Alquiza, Amaia. Universidad del País Vasco; EspañaFil: Fernández López, Victor. Universidad del País Vasco; EspañaFil: Rodriguez Robledo, Juan M.. Universidad del País Vasco; EspañaFil: Brito, Oscar. Instituto Nacional de Cardiologia; BrasilFil: Schleier, Ygor. Universidade Federal do Rio de Janeiro; BrasilFil: Sepúlveda, Marisa Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Oshiyama, Natalia F.. University of Campinas. Center for Biomedical Engineering; BrasilFil: Vila Petroff, Martin Gerarde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Bassani, Rosana A.. University of Campinas. Center for Biomedical Engineering; BrasilFil: Medei, Emiliano H.. Universidade Federal do Rio de Janeiro; BrasilFil: Casis, Oscar. Universidad del País Vasco; Españ

Correlative multi-scale cryo-imaging unveils SARS-CoV-2 assembly and egress.

Funder: Medical Research CouncilSince the outbreak of the SARS-CoV-2 pandemic, there have been intense structural studies on purified viral components and inactivated viruses. However, structural and ultrastructural evidence on how the SARS-CoV-2 infection progresses in the native cellular context is scarce, and there is a lack of comprehensive knowledge on the SARS-CoV-2 replicative cycle. To correlate cytopathic events induced by SARS-CoV-2 with virus replication processes in frozen-hydrated cells, we established a unique multi-modal, multi-scale cryo-correlative platform to image SARS-CoV-2 infection in Vero cells. This platform combines serial cryoFIB/SEM volume imaging and soft X-ray cryo-tomography with cell lamellae-based cryo-electron tomography (cryoET) and subtomogram averaging. Here we report critical SARS-CoV-2 structural events - e.g. viral RNA transport portals, virus assembly intermediates, virus egress pathway, and native virus spike structures, in the context of whole-cell volumes revealing drastic cytppathic changes. This integrated approach allows a holistic view of SARS-CoV-2 infection, from the whole cell to individual molecules

17-a-estradiol late in life extends lifespan in aging UM-HET3 male mice; nicotinamide riboside and three other drugs do not affect lifespan in either sex.

In genetically heterogeneous mice produced by the CByB6F1 x C3D2F1 cross, the non-feminizing estrogen, 17-α-estradiol (17aE2), extended median male lifespan by 19% (p \u3c 0.0001, log-rank test) and 11% (p = 0.007) when fed at 14.4 ppm starting at 16 and 20 months, respectively. 90th percentile lifespans were extended 7% (p = 0.004, Wang-Allison test) and 5% (p = 0.17). Body weights were reduced about 20% after starting the 17aE2 diets. Four other interventions were tested in males and females: nicotinamide riboside, candesartan cilexetil, geranylgeranylacetone, and MIF098. Despite some data suggesting that nicotinamide riboside would be effective, neither it nor the other three increased lifespans significantly at the doses tested. The 17aE2 results confirm and extend our original reports, with very similar results when started at 16 months compared with mice started at 10 months of age in a prior study. The consistently large lifespan benefit in males, even when treatment is started late in life, may provide information on sex-specific aspects of aging