94 F. B. BANG 



as contrasted with monkey kidney, started with a disappearance of the 

 nucleolus (Dunnebacke 1956b, 1957). 



An interesting attempt to segregate the process of viral synthesis from the 

 changes seen in the cell used the metabolic inhibitor, fluorphenylalanine 

 (Ackerman et al., 1954). Apparently, once the virus infection was initiated, 

 although actual production of infectious virus was inhibited, cell changes 

 proceeded. The changes described are mainly terminal, however, and a more 

 detailed comparison of the viral growth and the cell changes in the same 

 cultures is needed. 



3. Other Findings 



An interesting attempt was made by Klone (1955b) to determine whether 

 infection of monkey kidney cells had any direct effect on mitotic activity. 

 No increase or decrease in mitosis rate was observed, but certain findings 

 suggested that cells might be infected before mitosis set in, and that division 

 would then proceed with eventual death of both daughter cells. By following 

 individual cells for a number of hours, he was able to show that both daughter 

 cells were destroyed at similar but not identical times. In one case, a cell was 

 followed through to an abnormal telophase, from which the cell did not 

 recover but fell apart. 



In an electron microscope study of "virus-like bodies" in the nuclei of 

 epithelial cells infected with type 1 poliomyelitis virus, Ruska et al. (1956) 

 have reported on the occurrence of accumulation of particles of about 26 nux 

 in size, in close association with remnants of nucleoli. The occurrence of these 

 particles, which in themselves are not highly distinctive, needs to be corre- 

 lated with the appearance of infectious virus and the sequence of cellular 

 changes. 



The localization of poliomyelitis antigen by fluorescent antibody (Buckley, 

 1956) shows that type 1 may be found both in the nucleus and the cytoplasm 

 and may be found in peripheral blebs of the cell as it breaks down. In the 

 early stages specific fluorescence was diffuse or granular. 



A summary of concurrent findings on the effects of poliomyelitis virus on 

 living cells in tissue culture would include: (1) Peripheral contraction of the 

 thin endoplasmic spread, which leaves ghosts of branched material behind to 

 simulate irregular extrusions; (2) disappearance of the nucleolus; (3) forma- 

 tion of a large, paranuclear mass. 



It seems clear that the morphological steps which lead to final death and 

 disintegration of the infected cell cannot as yet be set in proper sequence. 

 The cells vary in their response to the virus so that, as yet, early cytoplasmic 

 changes have not been differentiated from nuclear destruction. Undoubtedly, 

 part of the difficulty is that different cells react in different ways to the same 

 virus (Dunnebacke, 1957). Thus, morphological evidence does not tell us 



