493 research outputs found

    Pan-embryo cell dynamics of germlayer formation in zebrafish

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    Cell movements are coordinated across spatio-temporal scales to achieve precise positioning of organs during vertebrate gastrulation. In zebrafish, mechanisms governing such morphogenetic movements have so far only been studied within a local region or a single germlayer. Here, we present pan-embryo analyses of fate specification and dynamics of all three germlayers simultaneously within a gastrulating embryo, showing that cell movement characteristics are predominantly determined by its position within the embryo, independent of its germlayer identity. The spatially confined fate specification establishes a distinct distribution of cells in each germlayer during early gastrulation. The differences in the initial distribution are subsequently amplified by a unique global movement, which organizes the organ precursors along the embryonic body axis, giving rise to the blueprint of organ formation

    Structure and decay of a proto-Y region in Tilapia, Oreochromis niloticus

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    Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.Sex-determination genes drive the evolution of adjacent chromosomal regions. Sexually antagonistic selection favors the accumulation of inversions that reduce recombination in regions adjacent to the sex-determination gene. Once established, the clonal inheritance of sex-linked inversions leads to the accumulation of deleterious alleles, repetitive elements and a gradual decay of sex-linked genes. This in turn creates selective pressures for the evolution of mechanisms that compensate for the unequal dosage of gene expression. Here we use whole genome sequencing to characterize the structure of a young sex chromosome and quantify sex-specific gene expression in the developing gonad. We found an 8.8 Mb block of strong differentiation between males and females that corresponds to the location of a previously mapped sex-determiner on linkage group 1 of Oreochromis niloticus. Putatively disruptive mutations are found in many of the genes within this region. We also found a significant female-bias in the expression of genes within the block of differentiation compared to those outside the block of differentiation. Eight candidate sex-determination genes were identified within this region. This study demonstrates a block of differentiation on linkage group 1, suggestive of an 8.8 Mb inversion encompassing the sex-determining locus. The enrichment of female-biased gene expression inside the proposed inversion suggests incomplete dosage compensation. This study helps establish a model for studying the early-to-intermediate stages of sex chromosome evolution.https://doi.org/10.1186/1471-2164-15-97

    Wildtype epidermal growth factor receptor (Egfr) is not required for daily locomotor or masking behavior in mice

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    BACKGROUND: Recent studies have implicated the epidermal growth factor receptor (EGFR) within the subparaventricular zone as being a major mediator of locomotor and masking behaviors in mice. The results were based on small cohorts of mice homozygous for the hypomorphic Egfr(wa2 )allele on a mixed, genetically uncontrolled background, and on intraventricular infusion of exogenous EGFR ligands. Subsequenlty, a larger study using the same genetically mixed background failed to replicate the original findings. Since both previous approaches were susceptible to experimental artifacts related to an uncontrolled genetic background, we analyzed the locomotor behaviors in Egfr(wa2 )mutant mice on genetically defined, congenic backgrounds. METHODS: Mice carrying the Egfr(wa2 )hypomorphic allele were bred to congenicity by backcrossing greater than ten generations onto C57BL/6J and 129S1/SvImJ genetic backgrounds. Homozygous Egfr(wa2 )mutant and wildtype littermates were evaluated for defects in locomotor and masking behaviors. RESULTS: Mice homozygous for Egfr(wa2 )showed normal daily locomotor activity and masking indistinguishable from wildtype littermates at two light intensities (200–300 lux and 400–500 lux). CONCLUSION: Our results demonstrate that reduced EGFR activity alone is insufficient to perturb locomotor and masking behaviors in mice. Our results also suggest that other uncontrolled genetic or environmental parameters confounded previous experiments linking EGFR activity to daily locomotor activity and provide a cautionary tale for genetically uncontrolled studies

    Level of sedation in critically ill adult patients : a protocol for a systematic review with meta-analysis and trial sequential analysis

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    Publisher Copyright: © 2022 BMJ Publishing Group. All rights reserved.Introduction It is standard of care to provide sedation to critically ill patients to reduce anxiety, discomfort and promote tolerance of mechanical ventilation. Given that sedatives can have differing effects based on a variety of patient and pharmacological characteristics, treatment approaches are largely based on targeting the level of sedation. The benefits of differing levels of sedation must be balanced against potential adverse effects including haemodynamic instability, causing delirium, delaying awakening and prolonging the time of mechanical ventilation and intensive care stay. This systematic review with meta-analysis aims to investigate the current evidence and compare the effects of differing sedation levels in adult critically ill patients. Methods and analyses We will conduct a systematic review based on searches of preidentified major medical databases (eg, MEDLINE, EMBASE, CENTRAL) and clinical trial registries from their inception onwards to identify trials meeting inclusion criteria. We will include randomised clinical trials comparing any degree of sedation with no sedation and lighter sedation with deeper sedation for critically ill patients admitted to the intensive care unit. We will include aggregate data meta-analyses and trial sequential analyses. Risk of bias will be assessed with domains based on the Cochrane risk of bias tool. An eight-step procedure will be used to assess if the thresholds for clinical significance are crossed, and the certainty of the evidence will be assessed using Grades of Recommendations, Assessment, Development and Evaluation. Ethics and dissemination No formal approval or review of ethics is required as individual patient data will not be included. This systematic review has the potential to highlight (1) whether one should believe sedation to be beneficial, harmful or neither in critically ill adults; (2) the existing knowledge gaps and (3) whether the recommendations from guidelines and daily clinical practice are supported by current evidence. These results will be disseminated through publication in a peer-reviewed journal.Peer reviewe

    Laboratory earthquake forecasting. A machine learning competition

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    Earthquake prediction, the long-sought holy grail of earthquake science, continues to confound Earth scientists. Could we make advances by crowdsourcing, drawing from the vast knowledge and creativity of the machine learning (ML) community? We used Google’s ML competition platform, Kaggle, to engage the worldwide ML community with a competition to develop and improve data analysis approaches on a forecasting problem that uses laboratory earthquake data. The competitors were tasked with predicting the time remaining before the next earthquake of successive laboratory quake events, based on only a small portion of the laboratory seismic data. The more than 4,500 participating teams created and shared more than 400 computer programs in openly accessible notebooks. Complementing the now well-known features of seismic data that map to fault criticality in the laboratory, the winning teams employed unexpected strategies based on rescaling failure times as a fraction of the seismic cycle and comparing input distribution of training and testing data. In addition to yielding scientific insights into fault processes in the laboratory and their relation with the evolution of the statistical properties of the associated seismic data, the competition serves as a pedagogical tool for teaching ML in geophysics. The approach may provide a model for other competitions in geosciences or other domains of study to help engage the ML community on problems of significance
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