| Abstract |
Although a great deal is known about the ultrastructure of both normal and
neoplastic cells of neuroectodermal origin, our appreciation of the three-
dimensional architecture and relationships of various neurons and glial
cells rests largely on classic light microscopic studies employing silver
impregnations of Golgi and Cajal. Ultrastructural serial sectioning
techniques have also been combined with computer assisted reconstruction
methods to further extend some of these relationships, e.g., synaptic
contacts of a neuron in well-defined anatomical systems. An alternate
complementary approach to three-dimensional architecture and relationships
of cells in the nervous system should also be possible utilizing
techniques of scanning electron microscopy (SEM). However, in order to
visualize cells with this technique, cells must either be isolated or
fractured in situ for examination. Isolation of cells from the central
nervous system (CNS) may significantly truncate or distort the processes
of cells as well as result in artefactual changes in their surfaces.
Cleavage of CNS tissue along natural fracture planes, as freeze fracture,
also gives only a limited plane of view in which many processes of a cell
are incompletely visualized, and in SEM the interpretation of surfaces
cleaved after critical point drying, and the various artefacts created by
such methods, are not well established and thus preclude definitive
interpretation.
Tissue culture would seem to present a more ideal starting point for
surface studies and visualization of relationships between different cells.
Growth patterns of various neuroectodermal elements can be studied after
there is repair of the initial damage incurred during cellular isolation.
The temporal development, or morphological changes in particular cells in
the living state, may be followed by light microscopy and then selected
for SEM evaluation. Finally, in isolated defined tissue culture systems
such as those of organotypic culture or monolayer culture, selected cells
may be exposed to agents or isotopes under controlled experimental
conditions for further evaluation of given morphological states. Tissue
culture, however, represents only one starting point since the most
exquisite anatomical definitions are lost, and only selected special
cellular elements are capable of growth and maintenance in such systems, i.
e., embryonic and fetal CNS, and tumor cells. The purpose of this chapter
is to describe similarities and differences clarified by SEM in identified
developing neurons and glial cells in culture with their "transformed"
counterparts, neuronal and glial neoplasms in culture.
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