Degeneration of purified cells on the neuron-
selective substratum polyornithine suggested that these
cells contained a paucity of neurons initially after
separation. Immunohistochemistry combined with 3H-thymidine
autoradiography of cells and monolayers demonstrated that
new DNA synthesis was required for neither the acquisition
of surface A2B5-antigen, nor for differentiation into
neurons. These results suggest that in early embryonic
vertebrate brain (days 7 and 8) cells are present which are
capable of replacing depleted neurons in vitro.
With day 12 and 13 cells, nearly all purified A2B5(-)
cells were identifiable as glia by reacting with antibodies
against either glutamine synthetase or galactocerebroside.
Most (=80%) of the purified A2B5(-) cells in culture for
one day became A2B5(+). No increase in the percentage of
A2B5(+) cells from 45% was observed in unpurified cultures.
Long-term monolayer cultures from purified cells contained
many A2B5(+) cells with a flattened glial or round
morphology. These A2B5(+) cells frequently reacted with
antibodies against glial fibrillary acidic protein and
another glial marker, 5A11, which indicated a partial glial
character. Additionally, flattened glial-like cells were
found to contain elaborate networks of anti-neurofilament-M
reactive filaments. The above combinations of markers were
not found in unpurified monolayers and are believed to be a
result of the immunomagnetic removal of neurons. It is
IX