Merkel cell mitoses in vibrissae: an ultrastructural study.

This is the first ultrastructural description of Merkel cell mitoses. We observed four mitotic cells showing dense cored membrane-bound granules within their cytoplasm, i.e. the unique ultrastructural characteristics of Merkel cells which are not shared by other cutaneous epithelial cell types. These cells were located in vibrissal hair follicles of 12, 13 and 14 days old mouse embryos. This finding indicates that proliferation of Merkel cells can take place in the skin.