title: Fine structures of embryonic discs of in vivo post-hatching porcine blastocysts at the pre-primitive streak stage.
abstract: To date, reports about the ultrastructure of porcine embryonic discs have not shown details of the primitive streak. The main objective of this study was to examine the ultrastructure of interior and exterior embryonic discs in porcine in vivo blastocysts with diameters of 1, 3 and 9 mm using scanning electron microscopy and transmission electron microscopy. For the first time, we revealed the ultrastructure of the unusual group of cells in the pre-primitive streak area of embryonic discs. The cells were 1-2 μm in diameter, had high electron density and contained abundant, free ribosomes and endoplasmic reticulum. These primitive streak cells could represent original embryonic stem cells or represent a stem cell niche. The results also showed three types of cells on the exterior surface of the embryonic discs. Moreover, our results provided morphological evidence of condensed nuclei in the smooth cells on the surface of the embryonic disc.
authors.affiliation: Department of Obstetrics and Gynecology, School of Medicine, University of California at Davis, Sacramento, CA, USA.
authors.forename: P
authors.initials: P
authors.lastname: Xia
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.forename: P
authors.initials: P
authors.lastname: Qin
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology* / Q000648:ultrastructure*; D002454:Cell Differentiation; D047108:Embryonic Development / Q000502:physiology*; D013552:Swine / Q000196:embryology*