[Ultrastructure of intercellular contacts in the histogenesis of the epidermis in the mouse].

Development of intercellular contacts in dermal epithelium of the back has been studied in 9-, 16-, 20-day-old mouse embryos and in 10-day-old animals. At the double layered stage of histogenesis the proper contacts of basal epitheliocytes are poorly developed. Early appearance of gap junctions takes place. These cells are kept in the layer at the expense of more differentiated peridermal cells and a continuous basal membrane. An intensive development of the intercellular junctions is observed in 15-day-old embryos. The spine cells make their contacts only by their processes. In the zone of the contacts desmosomes, connective complexes, invaginations are often seen. By the 20th day of embryogenesis, contact plates are formed, although essential intercellular gaps still remain. By the 10th day of the postnatal period, a column of the epidermal proliferative unit is formed. Melanocytes have both desmosomes and semidesmosomes. Apigmented granular dendrocytes (Langerhans cells) are connected with epidermocytes by means of simple and gap junctions. The data obtained make wider our knowledge on cellular interactions between variously differentiated cells in the tissue composition as an integrated system.