Abstract |
This thesis is a study of the biology of Drosophila imaginal disc cells
growing as continuous cell lines. Their morphological characteristics and
cellular properties were analysed in order to characterise the cells in
vitro. Morphological analysis of the cells revealed several cell types
within the original cell lines perhaps representing a diversity in the
cellular origin of these cells. A new cloning technique was devised which
enabled a single imaginal disc cell to give rise to new cell line and
indicated that a single cell could give rise to the different cell types
seen in culture. This indicates that the diversity in morphology of the
cells in culture was an indication of the conditions in culture rather
than as a result of cellular diversity. The original cell lines and the
newly derived cloned cell lines were subjected to the insect moulting
hormone 20-HE in order to ascertain the degree of differentiation that was
possible in culture. The cells showed a dramatic morphological response to
hormone, they elongated, began to aggregate and threw out cell processes.
This is combined with concomitant biochemical changes in the cell lines,
including the induction of chitin synthesis and acetylcholinesterase. The
cells in culture show a characteristic pattern of aggregation which was
studied at the ultrastructural level using electron microscopy. These
studies and also immunofluorescence of cell aggregates indicated the
prevalence of cell processes and a role was postulated for their action in
bringing about these aggregates. Aggregation was also correlated with the
expression of PS integrins, which are well characterised Drosophila
adhesion molecules. The adhesive properties of the cells were further
characterised with reaggregation experiments in different media as a
prelude to setting up cell sorting assays between wing and leg cell lines.
This proved somewhat inconclusive but pointed to some sorting out
occurring between wing and leg cells.
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