Effects of synthetic tripeptide on the differentiation of dissociated cerebral hemisphere nerve cells in culture.

Dissociated cells from 7-day-old chick embryo cerebral hemispheres were cultivated on collagen in Falcon Petri dishes in the presence of various concentrations of fetal calf serum and of a chemically synthesized tripeptide Gly-His-Lys. Four different culture conditions were employed in the composition of the nutrient medium in which the cells were cultivated: a low serum concentration of 1, 2 or 5% (group A), a low serum concentration with 200 ng/ml tripeptide (group B), a serum concentration of 10 to 20% (group C) and a serum concentration of 10 or 20% with 200 ng/ml tripeptide (group D). Within the first 24 h of cultivation the cells settled on the collagen substrate and outgrowth of neuronal processes started in all four culture conditions. After 48 h in culture, differences between the groups became evident. In group A most isolated nerve cells had disappeared and glial cells proliferated from the remaining clumps. In group B the neurons had differentiated in absence of glial cells, the proliferation of which was greatly suppressed. In group C and D a differentiation of neurons occurred in a similar way to group B, but in addition the glial cells had proliferated. After 7-8 days in culture the cells in group A and B suddenly degenerated. In group C and D the nerve cells maintained for up to 3 weeks. The optimum concentrations of tripeptide in which the neuroblasts grew fibers and maintained in culture during 7-8 days were in the range of 100-400 ng/ml. The role of the tripeptide in the differentiation and maintenance of nerve cells is discussed.