Although the cells in tissues are known to be motile under special conditions (e.g., during tissue turnover or wound healing), there are not many reports that polygonal cells covering an area without leaving any gaps are also capable of movement. In the present study, cell movements (cell shifting and rearrangement) in a living mammalian eye tissue were documented by identifying and locating individual cells over intervals as long as 100 days. Cat corneal endothelium, a monolayered cell sheet, was wounded by removing a small number (about 180) of endothelial cells from the internal lining of the cornea. Healing of the wounded tissue was observed with a wide-view specular microscope applied to the outer surface of the cornea, enabling us to identify individual cells for as long as two to three months. Cells surrounding the wound underwent areal enlargement, elongated toward the wound, and shifted to cover the wound surface. During days 4-7, cells became rearranged by changing neighbors in such a way that they retained their enlarged size but recovered their non-elongated, original shape. This pattern of cell rearrangement was interpreted by a computer simulation which assumed that cells shorten their boundary length while maintaining contacts with contiguous cells. After day 7, the enlarged cells adjacent to the wounded area gradually contracted and pulled surrounding cells toward the wounded area. These movements were followed by a temporary halt in cell shifting, then by a recovery of shifting and cell elongation. These movements are interpreted as a result of the contractility of endothelial cell microfilaments.

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A case of mesenchymal chondrosarcoma occurring in the right orbit of a 84-year-old Japanese female was reported. The ultrastructural findings of tumour are composed of three cell types: well-differentiated cartilaginous cells, undifferentiated cells and transitional cells. The well-differentiated cells showed scalloped cytoplasmic membranes, numerous mitochondria showing dense electron matrix, various size of lipid granules, and abundant amount of extracellular matrix. The extracellular matrix were collagen fibres and ground substances and matrix vesicle. The undifferentiated cells showed smooth cytoplasmic membranes, large nuclei resembling primitive mesenchymal cells.

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