In this study, we tested a number of defined and undefined compounds i
n comparison with yeastolate in Sf-9 insect cell culture including a g
roup of B vitamins and a series of purines and pyrimidines. Yeastolate
promoted the cell growth appreciably, increasing the maximum cell den
sity by more than 60%. Vitamins and purines, which are considered as t
he major constituents of yeastolate, are not responsible for its growt
h-promoting effect.