Nucleoli of animal cells cultured in vitro are modified by a component of "nonimmune" animal serum. Modified nucleoli bind fluorescein-conjugated nonimmune serum proteins, as shown by calcium ion-dependent fluorescence. Analysis of serum indicates that the nucleolar-binding component is a globulin, with an electrophoretic mobility in the same region as the slow alpha-1 component in pH 8.6 Veronal buffer. The component has a low sedimentation constant (2.4S), and appears to contain glycoprotein with relatively high sialic acid content (8.5%); the latter moiety may be essential to reaction with nucleoli. The nucleolar component reacting with this alpha globulin fraction appears to be a histonelike basic protein. Primary cultures of animal cells have been supported for 1 wk through attachment, spreading, and outgrowth from colonies to confluent monolayers in medium containing a nucleolar-reactive serum fraction as the only protein supplement.
AFFINITY OF ANIMAL CELL NUCLEOLI FOR NORMAL SERUM : Preliminary Characterization of Serum and Cell Components
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John C. Maisel, Ralph I. Lytle; AFFINITY OF ANIMAL CELL NUCLEOLI FOR NORMAL SERUM : Preliminary Characterization of Serum and Cell Components . J Cell Biol 1 June 1966; 29 (3): 461–473. doi: https://doi.org/10.1083/jcb.29.3.461
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