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the A2B5(+) cells that were seen after one day in culture.
The A2B5(+) neurons that developed in unpurified cultures
may have originated from the A2B5(+) cells that were
present when the tissue was dissociated (which were
presumably were the same cells that were A2B5(+) after a
day in culture). The fact that either no change or a slight
increase in the percentage of A2B5(+) cells occured in
unpurified cells after one day in culture is consistent
with A2B5 antigen not being modulated in unpurified
cultures. Similarly, the A2B5(+) neurons that developed in
purified cultures may have originated from the recruited
A2B5(+) cells seen after a day in culture. If this
hypothesis were true, then, this would imply the existence
of a previously unidentified intermediate cell type in the
optic tectum neuronal lineage. This cell would have the
characteristics of being A2B5(+)/ NF-M(-) and would be
susceptible to degeneration on polyornithine.
The analysis of GS in culture revealed another manner
in which purified cultures were identical to unpurified
cultures. GS was produced in purified monolayer cultures in
an indistinguishable pattern from unpurified cultures.
Quantitatively, the expression of GS in the two types of
cultures was also the same. These results suggest several
possible explanations. One is that the purification did
not result in separation of neurons and glia. This has been
discussed above. Another is that a small number of neurons