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as a marker for neurons than at day 7 or 8 (see Chapter 2).
Day 12 and 13 dissociated cells did not contain the easily
discernable rings of neurofilaments that were
characteristic of the day 7 and 8 cells. Most NF-M
reactivity was in the form of small blebs on one side of
the cell. These were presumably remnants of axons that were
sheared off during tissue dissociation. This difference in
immunoreactivity encountered in the older dissociated cells
possibly reflected more stable attachments between neurons
and thus an inability to retract their axons. Day 7 and 8
cells are in a phase of migration (LaVail and Cowan, 1971a)
and therefore might not have had the stable attachments of
the older tissue.
A2B5 Antigen and its Modulation
Purified cells were initially devoid of A2B5(+) cells.
This was demonstrated by both the immunofluorescent as well
as the immunoradiometric assays immeadiately following the
separations. The appearance of A2B5(+) cells in the
purified cell population in vitro was similar to that
reported with day 7 and 8 cells and was similarly confirmed
by the immunoradiometric assay. This suggests that the same
mechanism may be operating for the recruitment of
additional A2B5(+) cells with day 12 and 13 cells as was
operating with day 7 and 8 cells. A major difference,
though, is the extent to which this occurs. Here, the
percentage of A2B5(+) cells that appears after 24 hrs. in