53 research outputs found
The Effect of a DNA Damaging Agent on Embryonic Cell Cycles of the Cnidarian Hydractinia echinata
The onset of gastrulation at the Mid-Blastula Transition can accompany profound changes in embryonic cell cycles including the introduction of gap phases and the transition from maternal to zygotic control. Studies in Xenopus and Drosophila embryos have also found that cell cycles respond to DNA damage differently before and after MBT (or its equivalent, MZT, in Drosophila). DNA checkpoints are absent in Xenopus cleavage cycles but are acquired during MBT. Drosophila cleavage nuclei enter an abortive mitosis in the presence of DNA damage whereas post-MZT cells delay the entry into mitosis. Despite attributes that render them workhorses of embryonic cell cycle studies, Xenopus and Drosophila are hardly representative of diverse animal forms that exist. To investigate developmental changes in DNA damage responses in a distant phylum, I studied the effect of an alkylating agent, Methyl Methanesulfonate (MMS), on embryos of Hydractinia echinata. Hydractinia embryos are found to differ from Xenopus embryos in the ability to respond to a DNA damaging agent in early cleavage but are similar to Xenopus and Drosophila embryos in acquiring stronger DNA damage responses and greater resistance to killing by MMS after the onset of gastrulation. This represents the first study of DNA damage responses in the phylum Cnidaria
Retinoic Acid Signalling and the Control of Meiotic Entry in the Human Fetal Gonad
The development of mammalian fetal germ cells along oogenic or spermatogenic fate trajectories is dictated by signals from the surrounding gonadal environment. Germ cells in the fetal testis enter mitotic arrest, whilst those in the fetal ovary undergo sex-specific entry into meiosis, the initiation of which is thought to be mediated by selective exposure of fetal ovarian germ cells to mesonephros-derived retinoic acid (RA). Aspects of this model are hard to reconcile with the spatiotemporal pattern of germ cell differentiation in the human fetal ovary, however. We have therefore examined the expression of components of the RA synthesis, metabolism and signalling pathways, and their downstream effectors and inhibitors in germ cells around the time of the initiation of meiosis in the human fetal gonad. Expression of the three RA-synthesising enzymes, ALDH1A1, 2 and 3 in the fetal ovary and testis was equal to or greater than that in the mesonephros at 8–9 weeks gestation, indicating an intrinsic capacity within the gonad to synthesise RA. Using immunohistochemistry to detect RA receptors RARα, β and RXRα, we find germ cells to be the predominant target of RA signalling in the fetal human ovary, but also reveal widespread receptor nuclear localization indicative of signalling in the testis, suggesting that human fetal testicular germ cells are not efficiently shielded from RA by the action of the RA-metabolising enzyme CYP26B1. Consistent with this, expression of CYP26B1 was greater in the human fetal ovary than testis, although the sexually-dimorphic expression patterns of the germ cell-intrinsic regulators of meiotic initiation, STRA8 and NANOS2, appear conserved. Finally, we demonstrate that RA induces a two-fold increase in STRA8 expression in cultures of human fetal testis, but is not sufficient to cause widespread meiosis-associated gene expression. Together, these data indicate that while local production of RA within the fetal ovary may be important in regulating the onset of meiosis in the human fetal ovary, mechanisms other than CYP26B1-mediated metabolism of RA may exist to inhibit the entry of germ cells into meiosis in the human fetal testis
Ibuprofen is deleterious for the development of first trimester human fetal ovary ex vivo
International audienceSTUDY QUESTION Does ibuprofen use during the first trimester of pregnancy interfere with the development of the human fetal ovary? SUMMARY ANSWER In human fetuses, ibuprofen exposure is deleterious for ovarian germ cells. WHAT IS KNOWN ALREADY In utero stages of ovarian development define the future reproductive capacity of a woman. In rodents, analgesics can impair the development of the fetal ovary leading to early onset of fertility failure. Ibuprofen, which is available over-the-counter, has been reported as a frequently consumed medication during pregnancy, especially during the first trimester when the ovarian germ cells undergo crucial steps of proliferation and differentiation. STUDY DESIGN, SIZE, DURATION Organotypic cultures of human ovaries obtained from 7 to 12 developmental week (DW) fetuses were exposed to ibuprofen at 1-100 μM for 2, 4 or 7 days. For each individual, a control culture (vehicle) was included and compared to its treated counterpart. A total of 185 individual samples were included. PARTICIPANTS/MATERIALS, SETTING, METHODS Ovarian explants were analyzed by flow cytometry, immunohistochemistry and quantitative PCR. Endpoints focused on ovarian cell number, cell death, proliferation and germ cell complement. To analyze the possible range of exposure, ibuprofen was measured in the umbilical cord blood from the women exposed or not to ibuprofen prior to termination of pregnancy. MAIN RESULTS AND THE ROLE OF CHANCE Human ovarian explants exposed to 10 and 100 μM ibuprofen showed reduced cell number, less proliferating cells, increased apoptosis and a dramatic loss of germ cell number, regardless of the gestational age of the fetus. Significant effects were observed after 7 days of exposure to 10 μM ibuprofen. At this concentration, apoptosis was observed as early as 2 days of treatment, along with a decrease in M2A-positive germ cell number. These deleterious effects of ibuprofen were not fully rescued after 5 days of drug withdrawal. LARGE SCALE DATA N/A. LIMITATIONS, REASONS FOR CAUTION This study was performed in an experimental setting of human ovaries explants exposed to the drug in culture, which may not fully recapitulate the complexity of in vivo exposure and organ development. Inter-individual variability is also to be taken into account. WIDER IMPLICATIONS OF THE FINDINGS Whereas ibuprofen is currently only contra-indicated after 24 weeks of pregnancy, our results points to a deleterious effect of this drug on first trimester fetal ovaries ex vivo. These findings deserve to be considered in light of the present recommendations about ibuprofen consumption pregnancy, and reveal the urgent need for further investigations on the cellular and molecular mechanisms that underlie the effect of ibuprofen on fetal ovary development. © The Author(s) 2018. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology
Pulmonary Endpoints (Lung Carcinomas and Asbestosis) Following Inhalation Exposure to Asbestos
Lung carcinomas and pulmonary fibrosis (asbestosis) occur in asbestos workers. Understanding the pathogenesis of these diseases is complicated because of potential confounding factors, such as smoking, which is not a risk factor in mesothelioma. The modes of action (MOA) of various types of asbestos in the development of lung cancers, asbestosis, and mesotheliomas appear to be different. Moreover, asbestos fibers may act differentially at various stages of these diseases, and have different potencies as compared to other naturally occurring and synthetic fibers. This literature review describes patterns of deposition and retention of various types of asbestos and other fibers after inhalation, methods of translocation within the lung, and dissolution of various fiber types in lung compartments and cells in vitro. Comprehensive dose-response studies at fiber concentrations inhaled by humans as well as bivariate size distributions (lengths and widths), types, and sources of fibers are rarely defined in published studies and are needed. Species-specific responses may occur. Mechanistic studies have some of these limitations, but have suggested that changes in gene expression (either fiber-catalyzed directly or by cell elaboration of oxidants), epigenetic changes, and receptor-mediated or other intracellular signaling cascades may play roles in various stages of the development of lung cancers or asbestosis
A Developmental Stage-Specific Switch from DAZL to BOLL Occurs during Fetal Oogenesis in Humans, but Not Mice
The Deleted in Azoospermia gene family encodes three germ cell-specific RNA-binding proteins (DAZ, DAZL and BOLL) that are essential for gametogenesis in diverse species. Targeted disruption of Boll in mice causes male-specific spermiogenic defects, but females are apparently fertile. Overexpression of human BOLL promotes the derivation of germ cell-like cells from genetically female (XX), but not male (XY) human ES cells however, suggesting a functional role for BOLL in regulating female gametogenesis in humans. Whether BOLL is expressed during oogenesis in mammals also remains unclear. We have therefore investigated the expression of BOLL during fetal oogenesis in humans and mice. We demonstrate that BOLL protein is expressed in the germ cells of the human fetal ovary, at a later developmental stage than, and almost mutually-exclusive to, the expression of DAZL. Strikingly, BOLL is downregulated, and DAZL re-expressed, as primordial follicles form, revealing BOLL expression to be restricted to a narrow window during fetal oogenesis. By quantifying the extent of co-expression of DAZL and BOLL with markers of meiosis, we show that this window likely corresponds to the later stages of meiotic prophase I. Finally, we demonstrate that Boll is also transiently expressed during oogenesis in the fetal mouse ovary, but is simultaneously co-expressed within the same germ cells as Dazl. These data reveal significant similarities and differences between the expression of BOLL homologues during oogenesis in humans and mice, and raise questions as to the validity of the Boll(-/-) mouse as a model for understanding BOLL function during human oogenesis
Sea urchin embryo as a model for analysis of the signaling pathways linking DNA damage checkpoint, DNA repair and apoptosis
The Characterization of Phospholipid Functional Group Probe Species on Respirable Silicon-Containing Dusts by Solid-State 13
Biopersistence of the mineral matter of coal mine dusts in silicotic human lungs: is there a preferential release of iron?
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