90 F. B. BANG 



two, rounded, Feulgen-negative, eosinophilic, intranuclear inclusions were 

 found 14 to 18 hours after infection. Later, the nuclei enlarged and Feulgen- 

 positive basophilic material appeared against a glassy nuclear background. 

 With types 3 and 4, the lesions appeared at about the same time and appeared 

 as sharply defined crystal-like masses which also varied in their reactions to 

 the Feulgen stain. The nuclei enlarged and developed a "flower-like" appear- 

 ance. Microspectrophotometry of these nuclei showed increased amounts of 

 DNA in the infected cells. The cytoplasm was noted as disintegrating late in 

 the development of the lesion. However, in none of the reported studies of 

 the effect of the virus has an attempt been made to follow specific early 

 changes with phase microscopy or vital stains. The early appearance of the 

 strongly eosinophilic inclusion while the nucleolus remains intact and then 

 the development of a late basophilic inclusion has been confirmed by Lepine 

 et al. (1957). 



B. Electron Microscopy 



Three groups of investigators have described the remarkable intranuclear 

 array of virus particles. The study of Lagermolm et al. (1957) was carried out 

 with a series of cells in tissue cultures fixed from 6 to 72 hours after infection 

 with 10 7 ID 50 of virus. With type 5 virus, the appearance of small collections 

 of particles, often adjacent to the nuclear membrane, at 24 hours corres- 

 ponded with a slight rise in infectivity and the first appearance of cell lesions 

 with the light microscope. By 48 hours of infection the nuclear changes were 

 more regular and the crystal structures contained many more particles. At 72 

 hours some of the cells still did not show nuclear or cytoplasmic changes. In 

 some there was a complete replacement of the nuclei by the virus particles, 

 which were 30-60 mjtx in diameter. It was estimated that with a cuboidal 

 arrangement of these particles occupying about 100 c/x of crystal volume 

 there would be approximately 10 6 virus particles per cell. 



In their complete paper Harford et al. (1956) describe nuclear changes very 

 similar to those mentioned above in types 1 to 4: the arrangement in rows, 

 the presence of internal bodies within the particles, which measure 65 m/x at 

 maximum size; the variable staining of the inclusions with Feulgen's reagent 

 is again noted. 



In a detailed study of the virus particles within the nucleus of HeLa cells 

 infected with type 3 (4 and 7 were also studied but not presented), Morgan 

 et al. (1956b) concentrated on the apparently regular variation in the density 

 of the numerous particles as they occurred in the nuclei of otherwise intact 

 cells. They propose that when the virus is packed into a crystal array the 

 lattice is a cubic, body-centred packing of identical spheres. The regular 

 alternation in density of the rows of particles in the crystalline array is ex- 

 plained by the fact that the thin sections of these arrays, which are of the 



