Electron Microscopic and Histochemical Studies of an Unusual Crystalline Protein Occurring in Cells Infected by Type 5 Adenovirus. Preliminary Observations

In the course of studies which are designed to yield information concerning the physical and chemical nature of the adenoviruses, as well as the manner of their development in infected cells, it has recently been discovered that type 5 adenovirus exhibits certain remarkable features. Earlier electron microscopic observations of types 3, 4, and 7 adenovirus in thin sections of HeLa cells showed that the viral particles develop in the nucleus and frequently exhibit crystalline arrangement in a cubic body-centered lattice (1, 2). Histochemical studies demonstrated that these crystals are Strongly Feulgenpositive, thus indicating that the virus contains deoxyribonucleic acid (3). Type 5 resembles types 3, 4, and 7 with respect to size, shape, internal structure, development in cell nuclei, and formation of Feulgen-positive crystals. However, a large proportion of cells which are infected by type 5 virus, as revealed by the electron microscope, also contain extraordinary crystals that are not composed of viral particles. These crystals often exceed 30 V in length and are