1,721,033 research outputs found
Oocyte aging: looking beyond chromosome segregation errors
No full textThe age‐associated decline in female fertility is largely ascribable to a decrease in oocyte quality. This phenomenon is multifaceted and influenced by numerous interconnected maternal and environmental factors. An increase in the rate of meiotic errors is the major cause of the decline in oocyte developmental competence. However, abnormalities in the ooplasm accumulating with age — including altered metabolism, organelle dysfunction, and aberrant gene regulation — progressively undermine oocyte quality. Stockpiling of maternal macromolecules during folliculogenesis is crucial, as oocyte competence to achieve maturation, fertilization, and the earliest phases of embryo development occur in absence of transcription. At the same time, crucial remodeling of oocyte epigenetics during oogenesis is potentially exposed to interfering factors, such as assisted reproduction technologies (ARTs) or environmental changes, whose impact may be enhanced by reproductive aging. As the effects of maternal aging on molecular mechanisms governing the function of the human oocyte remain poorly understood, studies in animal models are essential to deepen current understanding, with translational implications for human ARTs. The present mini review aims at offering an updated and consistent view of cytoplasmic alterations occurring in oocytes during aging, focusing particularly on gene and epigenetic regulation. Appreciation of these mechanisms could inspire solutions to mitigate/control the phenomenon, and thus benefit modern ARTs
Characterization, isolation and culture of primordial germ cells in domestic animals: recent progress and insights from the ovine species
No full textPrimordial germ cell (PGC) allocation, characterization, lineage restriction, and differentiation have been extensively studied in the mouse. Murine PGC can be easily identified using markers as alkaline phosphatase content or the expression of pluripotent markers such as Pou5f1, Nunog, Sox2, Kit, SSEA1, and SSEA4. These tools allowed us to clarify certain aspects of the complex interactions of somatic and germinal cells in the establishment of the germ cell lineage, its segregation from the neighbouring somatic tissue, and the guidance mechanisms during migration that direct most of the germ cells into the genital ridges. Few data are available from other domestic animals and here we reported our preliminary studies on the isolation, characterization, and in vitro culture of sheep PGCs. Sheep PGCs can be identified with the markers previously used in mouse, but, in some cases, these markers are not coherently expressed in the same cell depending on the grade of differentiation and on technical problems related to commercial antibodies used. Pluripotency of PGCs in culture (EGCs) from domestic animals also needs further evaluation even though the derivation of embryonic pluripotent cell lines from large mammals may be an advantage as they are more physiologically similar to the human and perhaps more relevant for clinical translation studies. Comprehensive epigenetic reprogramming of the genome in early germ cells, and derived EGCs including extensive erasure of epigenetic modifications, may be relevant for gaining insight into events that lead to reprogramming and establishment of totipotency. EGCs can differentiate in vitro in a various range of tissues, form embryonic bodies, but in many cases failed to generate tumours when transplanted into immunodeficient mice and are not able to generate germline chimeric animals after their transfer. Such incomplete information clearly indicates the urge to improve the studies on derivation of stem cells in farm animals and shows the need for a multidisciplinary investigation in order to create farm animal models to set up suitable ethical and technical systems for cell regenerative therapies in humans. (C) 2010 Elsevier Inc. All rights reserved
142 Mimicking the follicular environment: in vitro maturation of prepubertal ovine oocytes in a liquid marble bioreactor as a 3-dimensional culture system
No full textCorrection: High in vitro survival rate of sheep in vitro produced blastocysts vitrified with a new method and device (Journal of Animal Science and Biotechnology (2019) 10 (90) DOI: 10.1186/s40104-019-0390-1)
No full textIn the original publication of this article [1], the author point out an error in Fig. 3. The correct Fig. 3 is below. The publisher apologizes to the readers and authors for the inconvenience. The original publication has been corrected
In vitro or in vivo post-fertilization embryo culture affects the gene expression patterns of ovine embryos
No full text3d liquid marble microbioreactors support in vitro maturation of prepubertal ovine oocytes and affect expression of oocyte-specific factors
No full textIn vitro oocyte maturation (IVM) is a well-established technique. Despite the high IVM rates obtained in most mammalian species, the developmental competence of IVM oocytes is subop-timal. The aim of this work was to evaluate the potential beneficial effects of a liquid marble micro-bioreactor (LM) as a 3D culture system to mature in vitro prepubertal ovine oocytes, as models of oocytes with intrinsic low competence. Cumulus–oocyte complexes of prepubertal sheep ovaries were in vitro matured in a LM system with hydrophobic fumed-silica-nanoparticles (LM group) or in standard conditions (4W control group). We evaluated: (a) maturation and (b) developmental rates following in vitro fertilization (IVF) and embryo culture; (c) expression of a panel of genes. LM and 4W groups showed similar IVM and IVF rates, while in vitro development to blastocyst stage approached significance (4W: 14.1% vs. LM: 28.3%; p = 0.066). The expression of GDF9, of enzymes involved in DNA methylation reprogramming and of the subcortical maternal complex was affected by the IVM system, while no difference was observed in terms of cell-stress-response. LM microbioreactors provide a suitable microenvironment to induce prepubertal sheep oocyte IVM and should be considered to enhance the developmental competence of oocytes with reduced potential also in other species, including humans
Comparazione dei patterns di espressione genica di embrioni prodotti in vitro da ovini adulti e prepuberi
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Genetic analysis of griffon vulture (Gyps fulvus) living in sardinia: a preliminary study
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