title: An ultrastructural study of implantation in the golden hamster. I. Loss of the zona pellucida and initial attachment to the uterine epithelium.
abstract: Forty five blastocysts from 14 golden hamsters were examined in situ with light and electron microscopy between 3 and 4 days of pregnancy (post-ovulation). At 3 days blastocysts remained free within the uterine lumen with their zonae pellucidae intact. At various intervals between 3 days and 3 days 6 hours a gradual thinning of the zona occurred, indicating the possible presence of a lytic factor which aids in the removal of the zona pellucida. Blastocysts at 3 days 8 hours had lost their zonae pellucidae, and by 3 1/2 days they were completely enclosed by the uterine pithelium. By 4 days a more intimate association between the juxtaposed trophoblast and uterine epithelium occurred, leaving intermittent deposits of electron-dense material between the adjoining plasma membranes.
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000648:ultrastructure; D010064:Embryo Implantation; D004848:Epithelium / Q000648:ultrastructure; D005260:Female; D008928:Mitochondria / Q000648:ultrastructure; D010063:Ovum / Q000648:ultrastructure*; D011132:Polyribosomes / Q000648:ultrastructure; D011247:Pregnancy; D014327:Trophoblasts / Q000648:ultrastructure; D014599:Uterus / Q000648:ultrastructure*; D015044:Zona Pellucida / Q000648:ultrastructure*