Abstract
Morphogenesis and cytodifferentiation of the subcommissural organ (SCO) of the hamster were studied by light, and scanning and transmission electron microscopy, from 11.0 to 15.6 days of gestation and to 60 days after birth. The cells of SCO were differentiated at 12.5 days of gestation, earlier than the adjacent ordinary ependymal cells. The SCO consisted of tall columnar epithelial cells with less developed organelles and short cilia. At 13.0 to 14.5 days of gestation, many polysomes and a small number of rER and microtubules were observed in the cytoplasm. At 15.0 days, rER, sER and microtubules were increased in number. Just before birth (15.5-15.6 days of gestation), cisternae of rER became slightly swollen and filled with flocculent substances. At 0 to 2 days after birth, the cisternae of rER were enlarged remarkably, and moderately electron-dense granules appeared in the apical cytoplasm. Irregular thread-like fibrils, apparently secretory materials, began to cover a part of the ventricular surface of the SCO, together with conspicuously stretched cilia. At 2 to 3 days after birth, secretory materials in the cytoplasm and in the ventricular surface became to be stained positively by chrome-alum hematoxylin, with the first appearance of Reissner's fiber. At 5 to 20 days, rER became more conspicuously swollen and filled with flocculent substances, as was observed in the adult.
