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Development of cellular polarity of hamster embryos during compaction
Theriogenology
255 DEVELOPMENTOF CELLULARPOLARITYOF HAMSTER EMBRYOSDURINGCOMPACTION H. SUZUKII, T. AZUMA~, H. KOYAMA 2 and X. YANG3
IFaculty of Agriculture and Life Sciences, Hirosaki University, Hirosaki, Japan, 2Department of Dairy Science, Rakuno Gakuen University, Japan and 3Department of Animal Science, University of Connecticut, Storrs CT 06269 USA Cellular polarization during preimplantation development of the embryo is believed to be a crucial event in the transition of a single cell embryo to a blastocyst stage embryo with morphologically and functionally differentiated cell types. Extensive studies have been done on this event in the mouse, but l i t t l e information is available in other species. The objectives of this study was to examine polarity development in hamster embryos by scanning electron microscopy (SEM), binding sites of Concanavalin A (Con A) and dynamics of nuclear and cytoskeletal polarity development. Embryos at different stages were collected from hamsters at various time following mating and isolated blastomeres or intact embryos were subjected to various analyses. SEMobservations revealed that 1 to 7 cell-stage embryos (n=90) showed a uniform distribution of microvilli over the cell surface. However, microvillous polarization was i n i t i a l l y noted in the blastomeres (10-35%, n:38) from 8-cell stage onward. Majority of microvillous poles remained in the basal region of imminent cell-cell contact but few were found at the apical surface of the blastomere. With FITC-Con A, the areas of cell contact were heavily stained, where the thick microfilament domain was also found with rhodamine-phalloidin stain. Microtubules were found more densely located around the nucleus during the interkinesis, and became redistributed in the region of the mitotic spindle during the karyokinesis. A nuclear position change from the center to the apical region away from the basal microvillous pole was noted at the 8-cell stage. I t is suggested that the changes of cell surface andnuclear position are the f i r s t manifestations of cell polarity of hamster 8-cell embryos and the outward migration of the nuclei may parallel to redistribution of microtubules in the cytoplasm. Supported by the Ito Foundation, Mishima Kaiun Memorial Foundation, Japan and by a Grants-in-Aid to Cooperative Research from RakunoGakuen University, 1996-1.
255 DEVELOPMENTOF CELLULARPOLARITYOF HAMSTER EMBRYOSDURINGCOMPACTION H. SUZUKII, T. AZUMA~, H. KOYAMA 2 and X. YANG3
IFaculty of Agriculture and Life Sciences, Hirosaki University, Hirosaki, Japan, 2Department of Dairy Science, Rakuno Gakuen University, Japan and 3Department of Animal Science, University of Connecticut, Storrs CT 06269 USA Cellular polarization during preimplantation development of the embryo is believed to be a crucial event in the transition of a single cell embryo to a blastocyst stage embryo with morphologically and functionally differentiated cell types. Extensive studies have been done on this event in the mouse, but l i t t l e information is available in other species. The objectives of this study was to examine polarity development in hamster embryos by scanning electron microscopy (SEM), binding sites of Concanavalin A (Con A) and dynamics of nuclear and cytoskeletal polarity development. Embryos at different stages were collected from hamsters at various time following mating and isolated blastomeres or intact embryos were subjected to various analyses. SEMobservations revealed that 1 to 7 cell-stage embryos (n=90) showed a uniform distribution of microvilli over the cell surface. However, microvillous polarization was i n i t i a l l y noted in the blastomeres (10-35%, n:38) from 8-cell stage onward. Majority of microvillous poles remained in the basal region of imminent cell-cell contact but few were found at the apical surface of the blastomere. With FITC-Con A, the areas of cell contact were heavily stained, where the thick microfilament domain was also found with rhodamine-phalloidin stain. Microtubules were found more densely located around the nucleus during the interkinesis, and became redistributed in the region of the mitotic spindle during the karyokinesis. A nuclear position change from the center to the apical region away from the basal microvillous pole was noted at the 8-cell stage. I t is suggested that the changes of cell surface andnuclear position are the f i r s t manifestations of cell polarity of hamster 8-cell embryos and the outward migration of the nuclei may parallel to redistribution of microtubules in the cytoplasm. Supported by the Ito Foundation, Mishima Kaiun Memorial Foundation, Japan and by a Grants-in-Aid to Cooperative Research from RakunoGakuen University, 1996-1.