Response to Gamma-radiation of Mouse Embryonic Lung Cultivated in Vitro

Summary

The radiation response of mouse embryonic lung-rudiments during 48 hours of cultivation in vitro was studied. The reaction appears to consist of the succession of two phases. The first phase lasts about 12 hours after irradiation, and may be defined as ‘epithelial phase’ as it shows degenerative changes of the epithelium, originating in the trachea and then gradually spreading in a distal direction as far as the terminal buds. In this phase no mitoses are observed either in the epithelium or in mesenchyme.

The second phase begins with resumption of mitotic activity and shows regenerative phenomena in the epithelium, which, however, maintains signs of diffuse cytological changes. At the same time pycnotic degeneration appears in the mesenchyme and invades it throughout, so that this phase can be called ‘mesenchymal’.