SHEEP TROPHOBLAST AND PLACENTAL FUNCTION - ULTRASTRUCTURAL-STUDY

  • 1 January 1977
    • journal article
    • research article
    • Vol. 124  (NOV) , 287-298
Abstract
Tissues were obtained from 16 ewes whose pregnancies ranged 70-146 days. Placentomes from each ewe (2-3) were perfused with ice-cold fixative through 1 or more fetal vessels and thin slices of the placenta were prepared for EM. Both the uninucleate cuboidal epithelial cells and the binucleate giant cells, of which the trophoblast was comprised, underwent marked structural modifications during the last half of pregnancy. The uninucleate epithelial cells showed ultrastructural features which may be correlated with the secretion of steroid hormones, the production of ovine placental lactogen and the performance of normal non-endocrine placental transport activities. The binucleate cells were of 2 main types, 1 concerned with glycogen storage and the other with the synthesis of a secretory product. Binucleate cells were always enclosed by a thin lamina of cuboidal cell cytoplasm which separated them completely from the maternal syncytium and the fetal connective tissue. Cuboidal epithelial and binucleate giant cells were either closely apposed or separated by canals or spaces of varying complexity. The ovine trophoblast was a further epithelium in which the local movement of water and solutes was mediated by standing gradient osmotic flow systems. Such flow systems may be an integral part of eutherian placental transport mechanisms.