Tubular intranuclear inclusions in Lucanus cervus: 3-dimensional model of some crystalloid zones of the inclusions by tilting experiments

Abstract

Intranuclear aggregates of flexuous tubules are observed in different tissues of the stag beetle Lucanus cervus. In cross section the tubules appear as electron-dense circles with 14 nm outside diameter. Electron microscopical autoradiography, after tritiated uridine or tritiated thymidine injection and DNA staining on ultrathin sections, reveal that these inclusions do not contain nucleic acids. On ultrathin sections of GMA-embedded tissues they could be extracted by pronase and are therefore proteinaceous in nature. Sometimes and particularly in the accessory glands of the male reproductive system, paracrystalline zones may appear in the inclusion, giving rise, on sections, to several pattern types. The use of an electron microscope fitted with a goniometer stage clearly demonstrated that these patterns are views of identical crystalloids sectioned through at different angles. In the crystalloid zones the flexuous tubules become straight with electron dense walls and constitute perfectly superposed layers of parallel tubules.