Effects of brain extracts from chick embryo on the development of astroblasts in culture

Different soluble extracts were prepared from chick brains and tested for their effect on the development of glial cells prepared from the cerebral hemispheres of newborn rats and grown in primary culture. Every brain extract tested, from animals between 8 days embryonic and adult ages, stimulated astroblast proliferation and accelerated their maturation as shown by morphological changes, the appearance of gliofilament bundles and by the increase of the amount of the glial-specific protein S-100 between 10 and 40 days in culture. These effects were observed in cultures continuously treated with extracts beginning with the 5th day after seeding. In cultures in which treatment was stopped 25 days after seeding, S-100 level continued to increase like in continuously treated cells. An identical increase of S-100 protein level was induced by treatments started as early as 24 h or as late as 25 days after seeding. In contrast, when the extracts were added at time 0 a toxic effect was observed and no stimulation of the maturation occurred.