IN a search for nerve growth factor (NGF) in tissue extracts of a muri
ne transplantable teratocarcinoma that harbours immature neural tissue
in abundance, a trypsin-sensitive and heat labile neurotrophic activi
ty was identified. The final protein fraction obtained by cation excha
nge chromatography contained five proteins with mel. wts ranging from
52 to 72 kD. It supported the growth and differentiation of immature n
eurones in neonatal rat cerebellar cultures but had no effect on embry
onic chick dorsal root ganglia which are the classical targets for NGF
.