102 research outputs found

    Stretch-Activated Piezo1 Channel in Endothelial Cells Relaxes Mouse Intrapulmonary Arteries

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    In intrapulmonary artery (IPA), endothelial cells (EC) respond to mechanical stimuli by releasing vasoactive factors to set the vascular tone. Piezo1, a stretch-activated calcium permeable channel is a sensor of mechanical stress in EC. The present study was undertaken to investigate the implication of Piezo1 in the endothelium-dependent regulation of IPA tone and its potential involvement in pulmonary hypertension, the main disease of this circulation. IPA tone was quantified by means of a myograph in control Piezo1+/+ mouse and in mouse lacking endothelial Piezo1 (EC-Piezo1-/-). Endothelial intracellular calcium concentration ([Ca2+]i) and nitric oxide (NO) production were measured, in mouse or human EC, with fluo-4 and DAF-fm probes, respectively. Immunofluorescence labeling and patch-clamp experiments revealed the presence of Piezo1 channels in EC. Yoda1, a Piezo1 agonist, induced an endothelium-dependent relaxation that was significantly reduced in pulmonary arteries in EC-Piezo1-/- compared to Piezo1+/+ mouse. Yoda1 as well as mechanical stimulation (by osmotic stress) increased [Ca2+]i in mouse or human EC. Consequently, both stimuli increased the production of NO. NO and [Ca2+]i increases were reduced in EC from Piezo1-/- mouse or in the presence of Piezo1 inhibitors. Furthermore, deletion of Piezo1 increased alpha-adrenergic mediated contraction. Finally, in chronically hypoxic mice, a model of pulmonary hypertension, Piezo1 still mediated arterial relaxation and deletion of this channel did not impair the development of the disease. The present study thus demonstrates that endothelial Piezo1 contributes to intrapulmonary vascular relaxation by controlling endothelial [Ca2+]i and NO production and that this effect is still present in pulmonary hypertension

    Coxiella burnetii Infection in Livestock, Pets, Wildlife, and Ticks in Latin America and the Caribbean: a Comprehensive Review of the Literature

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    Purpose of the Review Q fever , a bacterial zoonosis caused by Coxiella burnetii, is reported very heterogeneously in humans in Latin America. The objective of this study was to review the data on Coxiella burnetii Infection in animals in Latin America and the Caribbean. Recent Findings A comprehensive literature review was carried out in the 47 countries and territories of Latin America on various search engines and grouped into four groups: livestock, pets, wildlife, and ticks. Summary Thus, 113 studies were selected between 1950 and 2022. Among the 47 countries, only 25 (53%) had at least one publication related to C. burnetii infection in animals. The most productive country was Brazil (N = 51), followed by French Guiana (N = 21), and Colombia (N = 16). Studies in livestock from 20 countries have shown widely varying country-to-country rates of seroprevalence, ranging from 0 to 67%. Some studies from seven countries, especially French Guiana and Brazil, found antibodies and sometimes positive PCR in dogs and cats, generally in the context of investigations around human clustered cases. Knowledge remained fragmented about infection in wildlife from only five countries (Chile, Colombia, Brazil, French Guiana, and Uruguay). C. burnetii infection was identified by PCR in Chiroptera (7 species), Rodentia (6 species), Suina (2 species), Xenartha (1 species), Cingulata (1 species), and Perissodactyla (1 species). Studies on Coxiella sp. in ticks have been performed in 11 countries, mostly in Brazil, and mainly found Coxiella-like endosymbionts. Thus, data on C. burnetii infection in animals are sparse and incomplete in Latin America and the Caribbean, and more research is warranted

    Leptotene/Zygotene Chromosome Movement Via the SUN/KASH Protein Bridge in Caenorhabditis elegans

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    The Caenorhabditis elegans inner nuclear envelope protein matefin/SUN-1 plays a conserved, pivotal role in the process of genome haploidization. CHK-2–dependent phosphorylation of SUN-1 regulates homologous chromosome pairing and interhomolog recombination in Caenorhabditis elegans. Using time-lapse microscopy, we characterized the movement of matefin/SUN-1::GFP aggregates (the equivalent of chromosomal attachment plaques) and showed that the dynamics of matefin/SUN-1 aggregates remained unchanged throughout leptonene/zygotene, despite the progression of pairing. Movement of SUN-1 aggregates correlated with chromatin polarization. We also analyzed the requirements for the formation of movement-competent matefin/SUN-1 aggregates in the context of chromosome structure and found that chromosome axes were required to produce wild-type numbers of attachment plaques. Abrogation of synapsis led to a deceleration of SUN-1 aggregate movement. Analysis of matefin/SUN-1 in a double-strand break deficient mutant revealed that repair intermediates influenced matefin/SUN-1 aggregate dynamics. Investigation of movement in meiotic regulator mutants substantiated that proper orchestration of the meiotic program and effective repair of DNA double-strand breaks were necessary for the wild-type behavior of matefin/SUN-1 aggregates

    Chromosome Painting Reveals Asynaptic Full Alignment of Homologs and HIM-8–Dependent Remodeling of X Chromosome Territories during Caenorhabditis elegans Meiosis

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    During early meiotic prophase, a nucleus-wide reorganization leads to sorting of chromosomes into homologous pairs and to establishing associations between homologous chromosomes along their entire lengths. Here, we investigate global features of chromosome organization during this process, using a chromosome painting method in whole-mount Caenorhabditis elegans gonads that enables visualization of whole chromosomes along their entire lengths in the context of preserved 3D nuclear architecture. First, we show that neither spatial proximity of premeiotic chromosome territories nor chromosome-specific timing is a major factor driving homolog pairing. Second, we show that synaptonemal complex-independent associations can support full lengthwise juxtaposition of homologous chromosomes. Third, we reveal a prominent elongation of chromosome territories during meiotic prophase that initiates prior to homolog association and alignment. Mutant analysis indicates that chromosome movement mediated by association of chromosome pairing centers (PCs) with mobile patches of the nuclear envelope (NE)–spanning SUN-1/ZYG-12 protein complexes is not the primary driver of territory elongation. Moreover, we identify new roles for the X chromosome PC (X-PC) and X-PC binding protein HIM-8 in promoting elongation of X chromosome territories, separable from their role(s) in mediating local stabilization of pairing and association of X chromosomes with mobile SUN-1/ZYG-12 patches. Further, we present evidence that HIM-8 functions both at and outside of PCs to mediate chromosome territory elongation. These and other data support a model in which synapsis-independent elongation of chromosome territories, driven by PC binding proteins, enables lengthwise juxtaposition of chromosomes, thereby facilitating assessment of their suitability as potential pairing partners

    Meiotic Chromosome Pairing Is Promoted by Telomere-Led Chromosome Movements Independent of Bouquet Formation

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    Chromosome pairing in meiotic prophase is a prerequisite for the high fidelity of chromosome segregation that haploidizes the genome prior to gamete formation. In the budding yeast Saccharomyces cerevisiae, as in most multicellular eukaryotes, homologous pairing at the cytological level reflects the contemporaneous search for homology at the molecular level, where DNA double-strand broken ends find and interact with templates for repair on homologous chromosomes. Synapsis (synaptonemal complex formation) stabilizes pairing and supports DNA repair. The bouquet stage, where telomeres have formed a transient single cluster early in meiotic prophase, and telomere-promoted rapid meiotic prophase chromosome movements (RPMs) are prominent temporal correlates of pairing and synapsis. The bouquet has long been thought to contribute to the kinetics of pairing, but the individual roles of bouquet and RPMs are difficult to assess because of common dependencies. For example, in budding yeast RPMs and bouquet both require the broadly conserved SUN protein Mps3 as well as Ndj1 and Csm4, which link telomeres to the cytoskeleton through the intact nuclear envelope. We find that mutants in these genes provide a graded series of RPM activity: wild-type>mps3-dCC>mps3-dAR>ndj1Δ>mps3-dNT = csm4Δ. Pairing rates are directly correlated with RPM activity even though only wild-type forms a bouquet, suggesting that RPMs promote homologous pairing directly while the bouquet plays at most a minor role in Saccharomyces cerevisiae. A new collision trap assay demonstrates that RPMs generate homologous and heterologous chromosome collisions in or before the earliest stages of prophase, suggesting that RPMs contribute to pairing by stirring the nuclear contents to aid the recombination-mediated homology search

    Parasite responses to pollution: what we know and where we go in ‘Environmental Parasitology’

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    Contamination des réseaux trophiques de l'estuaire de la Gironde par les métaux-traces

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    Extrait de documentLa Gironde, milieu de transition, apparaît comme particulièrement vulnérable et menacé par des contaminations métalliques. Les recherches mises en oeuvre dans le cadre du GIS ECOBAG s'inscrivent dans une démarche résolument pluridisciplinaire et exploratoire, basée sur trois compartiments biologiques : la base des réseaux trophiques, les bivalves, les poissons
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