Cellular dynamics of growth in sheep and goat synepitheliochorial placentomes: an autoradiographic study

• Published in: Journal of reproduction & fertility Vol. 98; no. 1; pp. 275 - 283
• Main Authors: Wooding, F B, Hobbs, T, Morgan, G, Heap, R B, Flint, A P
• Format: Journal Article
• Language: English
• Published: England Society for Reproduction and Fertility 01-05-1993
• Subjects: Animals; Autoradiography; Female; Goats - physiology; Microscopy, Electron; Placenta - cytology; Placenta - ultrastructure; Placentation; Pregnancy; Pregnancy, Animal - physiology; Sheep - physiology
• ISSN: 1470-1626; 0022-4251; 1741-7899
• DOI: 10.1530/jrf.0.0980275

This paper demonstrates that in sheep and goats the two definitive fetomaternal interface layers are developmentally related.
The fetal trophectoderm consists of binucleate and uninucleate cells. The apical microvilli of the trophectoderm interdigitate
with a layer consisting of syncytial plaques of limited area bounding the maternal connective tissue. Our previous histological
ultrastructural and immunocytochemical work has indicated that throughout pregnancy the fetal binucleate cells migrate to
and fuse with the uterine epithelium or its derivatives to form these syncytial plaques which constitute a persistent fetomaternal
tissue unique to ruminants. This quantitative autoradiographic study of thymidine incorporation into sheep and goat placentas
confirms the central role of the binucleate cell in placental growth, demonstrates that throughout pregnancy all binucleate
cells migrate and indicates that most of the nuclei of the syncytial plaques, which appear to have a limited lifespan, derive
from binucleate cell fusion.