a competitive basis, based on the merit of the research project 

 as evaluated by Centers' Steering Committees. 



Examples of recent activities at the Centers are: 



1. Production of 100 mg Sindbis Virus propagated 

 in 200 roller bottles of cells for use in x-ray 

 structural studies. 



2. Production of 750 roller bottles of SV40 trans- 

 formed BALB 3T3 cells for purification and 

 characterization of T antigen. 



3. Growth of 300 liters of mouse leukemia cells 

 for isolation and structural analysis of a 

 specific lysine transfer RNA implicated in 

 the control of cell division. 



4. Growth of 3.1 x 10 12 BW 5147 cells for the 

 isolation and structural analysis of H-2k 

 and Thy-1 alloantigens. 



Following approval of an application, the investigator sends 

 a stock of cells or virus to the center. The stock is then grown 

 to the requested amount, under conditions of careful handling and 

 rigorous screening for contaminants (including mycoplasma), and 

 prepared according to the needs of the investigator. Investi- 

 gators will be asked to pay minimal costs to cover media and 

 other supplies. 



165 



