29 research outputs found

    Addition of granulosa cells collected from differential follicle stages supports development of oocytes derived from porcine early antral follicles

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    Abstract Purpose Improvement of in vitro oocyte growth by addition of granulosa cells derived from differential developmental stages of follicles. Methods Granulosa cells (GCs) collected from either early antral follicles (EAFs) or antral follicles (AFs) were added to oocyte‐granulosa cell complexes (OGCs) derived from EAFs, and the in vitro growth of the oocytes was evaluated. Results Granulosa cells were incorporated into OGCs to form new OGCs within 2 days of culture. After 14 days of culture, the number of GCs surrounding oocytes was similar among the three OGCs conditions (unmanipulated “natural OGCs,” “EAF‐GCs add OGCs,” and “AF‐GCs add OGCs”), whereas the survival rate of the GCs and diameter of oocytes grown in vitro were the greatest for “AF‐GCs added OGCs.” After parthenogenetic activation, developmental rate till the blastocyst stage tended to be higher for “AF‐GCs add OGCs” compared with other groups. Addition of AF‐GCs significantly increased a hypoxic marker (pimonidazole staining) and increased the lipid content in oocytes grown in vitro compared with unmanipulated OGCs. Conclusion Addition of GCs derived from more advanced stages of follicles to the OGCs changes the metabolism of oocytes and is beneficial for in vitro growth of oocytes derived from EAFs

    Active DNA damage response signaling initiates and maintains meiotic sex chromosome inactivation

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    Meiotic sex chromosome inactivation (MSCI) is an essential process in the male germline. While genetic experiments have established that the DNA damage response (DDR) pathway directs MSCI, due to limitations to the experimental systems available, mechanisms underlying MSCI remain largely unknown. Here we establish a system to study MSCI ex vivo, based on a short-term culture method, and demonstrate that active DDR signaling is required both to initiate and maintain MSCI via a dynamic and reversible process. DDR-directed MSCI follows two layers of modifications: active DDR-dependent reversible processes and irreversible histone post-translational modifications. Further, the DDR initiates MSCI independent of the downstream repressive histone mark H3K9 trimethylation (H3K9me3), thereby demonstrating that active DDR signaling is the primary mechanism of silencing in MSCI. By unveiling the dynamic nature of MSCI, and its governance by active DDR signals, our study highlights the sex chromosomes as an active signaling hub in meiosis

    Standardization of Size, Shape and Internal Structure of Spinal Cord Images: Comparison of Three Transformation Methods

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    <div><p>Functional fluorescence imaging has been widely applied to analyze spatio-temporal patterns of cellular dynamics in the brain and spinal cord. However, it is difficult to integrate spatial information obtained from imaging data in specific regions of interest across multiple samples, due to large variability in the size, shape and internal structure of samples. To solve this problem, we attempted to standardize transversely sectioned spinal cord images focusing on the laminar structure in the gray matter. We employed three standardization methods, the affine transformation (AT), the angle-dependent transformation (ADT) and the combination of these two methods (AT+ADT). The ADT is a novel non-linear transformation method developed in this study to adjust an individual image onto the template image in the polar coordinate system. We next compared the accuracy of these three standardization methods. We evaluated two indices, i.e., the spatial distribution of pixels that are not categorized to any layer and the error ratio by the leave-one-out cross validation method. In this study, we used neuron-specific marker (NeuN)-stained histological images of transversely sectioned cervical spinal cord slices (21 images obtained from 4 rats) to create the standard atlas and also to serve for benchmark tests. We found that the AT+ADT outperformed other two methods, though the accuracy of each method varied depending on the layer. This novel image standardization technique would be applicable to optical recording such as voltage-sensitive dye imaging, and will enable statistical evaluations of neural activation across multiple samples.</p></div

    Sample images of spinal cord.

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    <p>(<b>A</b>) Isolated lower brainstem and cervical spinal cord. (<b>B</b>) Neuron-specific marker NeuN-stained histological image of the cross-section of the spinal cord at C4 level. A NeuN-stained image showed clearly demarcated laminar structures of the gray matter of the spinal cord.</p
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