[The role of the mesenchyme in the development of the early primordium of the respiratory epithelium].

Development of respiratory epithelium (RE) rudiment was studied in tissue culture after removal of mesenchyme (M) and respiratory tract (RT) in 13 days old embryos of A and C57BL mice. During long-term cultivation of intact RT, organotypic structures (branching bronchioles, alveolus-like cavities) developed. No epithelial organotypic structures developed in the presence of single M cells; explants were represented by layers of cubic epithelium. During long-term cultivation foci of atypical growth consisting of intensively proliferating basophilic cells with high nucleocytoplasmic ratio appeared in these explants. Regions of planocellular metaplasia with or without keratinization could be found in these foci. The frequency of atypical proliferates depended on the strain of donor mice and on the region of the explanted RT.