Ultrastructure and formation of lamellated inclusion bodies in induced lung tumors of the European hamster.

Utlrastructure and formation of lamellated inclusion bodies (LB) in N-dibutyl-nitrosamine-induced lung tumors in European hamsters are described. Two types of LBs are observed: one with cross-barred lamellae and one with concentric lamellae. Both types develop from lysosome-like dense bodies which are formed by the Golgi apparatus. More mature forms fuse with rough endoplasmic reticulum (RER). Mature LBs migrate to the cell surface, where their contents are extruded into the alveolar lumen by means of a merocrine secretion. The extruded lamellae give rise to the myelin figures and lattices that are reported to possess surfactant properties.