Ultrastructural Study of Changes in Cell Morphology and Extracellular Matrix in Prospective Endodermal Cells of Newt...

The cell morphology, cell-to-cell contact behavior and extracellular matrix (ECM) of inner cells (prospective endodermal cells) of newt (Cynops pyrrhogaster) embryos were examined from the morula to gastrula stage by light and electron microscopy. The inner cells showed increased cell-to-cell contact from the early blastula to early gastrula stage. The cells formed blebs (5-15 μm in diameter) during the blastula stage, and started to form filopodia and lamellipodia before gastrulation. Alcian blue and lanthanum nitrate treatment revealed ECM components on the cell surface in the early blastula stage and these components increased in amount from the late blastula to early gastrula stage. It is suggested that the increase in ECM components on the cell surface may have some relation with changes in cell-to-cell contact and formation of processes on the cell surface. Besides the cell surface ECM components, glycogen-like granules were observed in intercellular spaces. From the distribution of granules in gastrulae, it is suggested that these may be important in maintaining intercellular spaces for migration of invaginating cells.