Hydroxyurea (10mM) blocks the exponential growth of Tetrahymena
pyriformis (GL-I) populations by arresting progress through the cell
cycle once the cells enter S-phase. Autoradiographic analysis reveals
that HU reduces the uptake of tritiated thymidine (³H-TdR) into
macronuclear DNA in S-phase cells to about 1/5 of that in untreated
S-phase cells....