Abstract
Morphology of the bovine amnion was studied by light microscopy, scanning and transmission electron microscopy throughout pregnancy. Early in gestation, amniotic epithelial cells were squamous with few microvilli and numerous cytoplasmic organelles. Late in gestation, cells were cuboidal with numerous microvilli, wide intercellular spaces, and few cytoplasmic organelles. Amnion contained many plaque-like projections. Amniotic plaques appeared to be formed by mitosis of normal epithelial cells. The ultrastructure of plaques was similar to mammalian epidermis. In addition, protein synthesis and secretion in vitro by amniotic tissues from Days 40, 70, 90 and 160 of pregnancy was characterized. Metabolically labeled proteins released into culture medium were analyzed by two-dimensional polyacrylamide gel electrophoresis and fluorography. Patterns of protein production by the amnion remained relatively unchanged from Days 40 through 160. A low molecular mass protein (23 kDa; pI 5.3–6.1) produced by amnion and present in amniotic fluid was identified as retinol-binding protein (RBP) by immune precipitation with antiserum to bovine placental RBP. Immunocytochemical analysis localized the protein in amniotic epithelial cells and cells of amniotic plaques. Results of the study suggest that morphological changes of bovine amnion during the course of pregnancy may reflect functional changes in the amnion. Moreover, proteins synthesized by bovine amnion, such as RBP, may function in embryonic development.
Published Version
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