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The substratum polyornithine resulted in much
different development of embryonic tectum cells in vitro.
As observed by Adler et al. (1979), when dissociated day 7
or 8 tectum cells were plated on polyornithine only the
neurons developed and the glia degenerated over a period of
about a week. This resulted in aggregates of neurons with
interconnecting processes attached to the coverslips amidst
the nuclei and debris of dead glia (Fig.2-8). When purified
A2B5(-) cells were plated on polyornithine virtually all
cells degenerated. Conversely, when cells recovered from
the microspheres (A2B5(+)-enriched) were plated on this
substratum many neurons developed. In fact, this fraction
of cells resulted in the most visually dense networks of
neurons. This suggests that the purified A2B5(-) cells were
deficient in neurons and that the microsphere cells were
enriched in them.
Filament Expression In Vitro
The expression in vitro of two neural tissue specific
intermediate filaments was examined by immunohistochemistry
of monolayer cultures. Glial fibrillary acidic protein
(GFAP) positive filaments were found to be present in the
population of A2B5(-) flat glial cells underlying the
neurons (not shown). Immuno-reactivity was seen in most if
not all flat cells but not in cells with a neuronal
morphology. Unlike GFAP, there were cells present in
dissociated 7 or 8 day tectum that reacted with antibodies