Ultrastructural changes after diapause in the uterine glands, corpus luteum and blastocyst of the red-necked wallaby, Macropus rufogriseus banksianus.
Pouch young were removed from animals (Day 0) captured in the wild in order to reactivate diapausing blastocysts. The blastocyst and tissues from the uterine endometrium and the corpus luteum were preserved for electron microscopy at Days 0, 2.5, 4, 5, 6, 9, 14 and 21. At Day 0 the diapausing blastocyst is a unilaminar sphere with a diameter of about 260 micrometers. Blastocysts up to and including Day 6 did not exhibit expansion and no mitotic metaphase stages were found. Mitotic activity was present in the blastocyst at Day 9 and the overall diameter had expanded to 675 micometers. At days 2.5, 4, 5 and 6 the height of the uterine gland epithelium had increased by about 15% with a slight increase in the amount of membrane-bound secretory vesicles in non-ciliated cells of the uterine glands. The presence in these cells of numerous polyribosomes and heightened Golgi activity as well as an expansion of the endoplasmic reticulum foreshadowed the onset of a secretory phase. Electron-dense membrane-bound granules which were a most conspicuous feature of the cytoplasm of fully active luteal cells started to appear as early as Day 4. At the ultrastructural level, signs of reactivation of the blastocyst are later than those that are evident in the luteal cells and in the non-ciliated secretory cells of the uterine glands.
D000818:Animals; D001755:Blastocyst / Q000502:physiology / Q000648:ultrastructure*; D003338:Corpus Luteum / Q000648:ultrastructure*; D047108:Embryonic Development; D005260:Female; D007614:Macropodidae / Q000033:anatomy & histology* / Q000502:physiology; D008394:Marsupialia / Q000033:anatomy & histology*; D008854:Microscopy, Electron; D011247:Pregnancy; D013997:Time Factors; D014599:Uterus / Q000648:ultrastructure*