Structural Changes in Hela Cells Cultivated in Serum-free Medium

In general, it is still impossible, except in a few instances (7, 9), to cult ivate an imal and h u m a n cells successfully in serum-free medium. W h e n cul t ivated under such conditions, the cells proliferate for only a l imited period of t ime and then stop. I t seems reasonable to assume tha t differences in the consti tuents of the med ium which have such a marked influence on pat terns of cell growth might be reflected in the fine s tructure of the cells. The role of serum in cell growth is one of the most interesting problems in the field of tissue culture. The impor tance of serum protein has been clarified recently by the observations of many investigators (5, 8, 11, 12, 14). However, so far the role of substances of low molecular weight in serum has not been made clear. The present investigation was designed to ascertain some of the changes in the ul t ras t ructure of HeLa cells grown in serum-free med ium and to clarify the role of substances of low molecular weight in serum in the growth of cells.