A variety of cell sizes and m orphologies was displayed both in prim ary and low passage and sometim es in higher passage level cell cultures. The m orphology displayed included spindle- shaped (bi-polar) and stellate (m ulti-polar), ep ith e lia l-lik e cells, m ulti-processed cells as w ell as sm all and large flat cells and polygonal cells of various sizes. All cultures d isp la y e d at least one or more of these morphologies.
Astrocytomas
M ost low and high grade astrocytoma cultures showed a great diversity of cell types in s h o rt term culture and included thin spindle-shaped cells, w ith both long and short processes, and large flat cells w ith processes as shown in Figs 7a, 8a and 9a respectively. The only s lig h t difference between the low and high grade tumours was th at the cells derived from th e higher grade tumours h ad a tendency to grow in clusters of tightly packed cells. In cultures derived from pilocytic astrocytomas, a striking feature w as the presence of cells w ith very long processes w hich resembled oligodendrocytes (Figs 7e & 8c respectively) w hich were infrequent in cultures derived from high grade astrocytomas. How ever, there did not a p p e a r to be differences betw een the pilocytic and fibrillary tum ours in term s of cell types.
M eduUoblastomas & PNETs
The most common feature of cultures derived from these tumours was the presence of flo a tin g aggregates. Such cultures also displayed heterogeneity in cell types present and included round, small and flat polygonal cells, both hi- and tri-polar cells as show n in Figs 10a and 11a respectively. Fascicular cells were displayed by a number of MB cultures and are illu s tra te d in Fig H e. In one PNET, (not shown) the culture displayed a varied m orphology to g eth e r w ith a "Homer-W right" rosette pattern of growth.
Ependymomas
The m ajority of ependymoma cultures comprised various cell types, including large flat and polygonal cells w ith frequent nucleoli present in m any of the cells as illustrated in Figs 12a-c and 13a-c. In some large flat cells, individual fibres were visible as show n in Figs 12b and 13c. As these cultures were passaged, the m orphology tended to change to a pattern of uniform
sheets of bi-polar cells. A lthough cell lines grown on plastic are not illu strated , th e m orphology of these cultures was similar to those seen on other substrates.
Morphology on different substrates
W hen the same culture was grown on different substrates, a different type of m orphology or the predom inance of a particular type of cell was observed in some cases. How ever, common cell types were seen in all tum our groups on different substrates. For all tum our histologies and substrates investigated, bi-polar cells were the most frequent cell type observed, T ri-p o lar m orphology was seen m ainly in low grade astrocytom as, m eduUoblastomas and ependymomas, but were not a prominent feature of high grade astrocytom a cultures. For ependymomas, grow th cn plastic, FN and LMN and vitrogen produced cell cultures w ith pleom orphism m ore m arked than that observed on PLL, CeU-tak, M atrigel and glass. On th e form er surfaces, a num ber of different ceU types were present in these cultures, including sm all and large polygonal cells (including flat and round), hi- and tri-polar cells w ith m any nucleoli, while on PLL, Cell-tak, M atrigel and glass, a m ore hom ogeneous ceU population w as observed, where, on a particular substrate, a certain cell type would dom inate. For exam ple, cn M atrigel, large fascicular cells w ith visible striated fibres were seen, w hile cn glass or PLL, ceUs would grow as sheets of bi-polar cells. Cultures produced from m eduU oblastom as
displayed considerable heterogeneity in m orphology in vitro.
The different grow th patterns seen in w ithin each of the histological groups grown cn a variety of substrates are iUustrated in Figs 7-13 and are described below.
Low grade pilocytic astrocytom a culture (IN1520) grown cn plastic, LMN, C e ll-ta k , M atrigel, glass and vitrogen is iUustrated in Figs 7a-f. A simUar type of m orphology w as seen cn plastic, LMN and vitrogen, i.e., bi- and tri-polar cells w ith short processes w ith th e occasional flat polygonal cell. However, cn surfaces CeU-tak, M atrigel and glass, a much more varied m orphology was displayed, including fascicular cells (on CeU-tak) and larg e flat cells (CeU-tak and M atrigel). Also of interest was the presence of cells w ith very long processes w hich resem bled oUgodendrocytes displayed on these three surfaces, w hich did not appear in cultures grow n on plastic, LMN and vitrogen. This suggests th a t CeU-tak, M a trig e l and glass prom oted the adherence and grow th of such cells.
Ependymoma cultures (IN1497 and U^1594) also showed a varied m orphology depending on substrate. For example, IN1594 displayed sim ilar cell types w hen grown on FN , LMN and CeU-tak (Figs 13a-c), ie., flat polygonal and fascicular cells. How ever, cells on CeU-tak w ere much larger w ith few processes, w hilst those grown cn FN and LMN w ere smaUer, w ith a rather larger num ber of ceUs w ith short processes. In addition, on LMN a m ore compact grow th was observed.