Cytosolic Antibody Research Articles

Globular intranuclear inclusions in the midgut cells of Carausius morosus: Ultrastructure, composition and kinetics of growth

Spherical electron-dense bodies, up to 2 μ m in diameter, are seen generally in clusters, in the nuclei of the midgut cells of Carausius morosus . The inclusions are never surrounded by a membrane and there seems to be no direct relationship between them and the nucleolus. Cytochemical methods on paraffin sections and on thin sections reveal that the inclusions are proteinaceous in nature and contain carbohydrates. In electron microscopical autoradiography the inclusions are densely labeled a few hours after an injection of tritiated lysine or arginine. The kinetics of inclusion growth, examined by quantitative ultrastructural autoradiography, suggest a migration of cytoplasmic proteins to the nucleus, where parts of them are then progressively incorporated into the intranuclear inclusions. The results of an immunocytochemical method utilizing cytosol antibodies are in agreement with these findings. Pellets of isolated intranuclear inclusions may be solubilized when treated by a combination of a hydrogen bond cleaving agent and a reducing agent. The amino acid composition reveals that the proteins of the inclusions are predominantly acidic. With SDS-polyacrylamide gel electrophoresis of the solubilized inclusions, up to 16 proteins can be detected; some of them are glycoproteins. A comparison between the electrophoretic profile of the inclusions and the profile of the cytosol proteins reveals that several proteins of the inclusions are major components of the cytosol.