Cell cycle and DNA content of mitotic cells in brain ganglia of Drosophila larvae.
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Date
1995-03
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Abstract
The programmes of replication of hetero- and euchromatin regions, mitotic cell
cycle and the DNA content in metaphases in brain ganglia from late third instar larvae
of Drosophila melanogaster (wild type and a tumour bearing mutant, 1(2)gl, strain) and
of Drosophila nasuta were examined by autoradiography of [3H]thymidine labelled (continuous
or pulse) cells and by cytophotometry, respectively. Brain ganglia labelled continuously
with [3H]thymidine for 24 h in vitro showed a significantly high proportion of cells with
incorporation of radioactivity restricted to heterochromatin only. Pulse labelling of brain
ganglia from larvae of Drosophila melanogaster and Drosophila nasuta followed by chase
for different time intervals showed that (i) the frequency of labelled metaphases was more
than 50% within 15 to 30 min of chase and remained higher than 50% in nearly all the
chase samples till 24 h, (ii) euchromatin labelled metaphases appeared with a low frequency
within 1 to 4 h chase period but the heterochromatin labelled metaphases continued to be
more common in the later chase samples also, (iii) single chromatid labelled second cycle
metaphases were seen within 1 to 4 h after the pulse, but their frequency did not increase
in the later samples. Cytophotometry of feulgen-DNA and Hoechst 33258 stained metaphases
in late third instar larval brain ganglia revealed a greater variation in the DNA content of
individual metaphases, although the means were close to the expected 4 C content. It
appears that in relation to the known asymmetric cell divisions of neuroblast and other
neural cells, the mitotically active cells in brain ganglia comprise a heterogenous population
with widely varying lengths of the different phases of cell cycle; some of them may not
cycle regularly and may possibly have a discontinuous S-phase.
Description
Keywords
Metaphase chromosomes, endoreplication, replication bands, feulgen-staining, Hoechst 33258
Citation
Lakhotia S C, Roy J K, Chowdhuri Sujata Kar. Cell cycle and DNA content of mitotic cells in brain ganglia of Drosophila larvae. Journal of Biosciences. 1995 Mar; 20(2): 175-195.