DNA synthesis in malaria parasites during sexual and erythrocytic asexual development : proefschrift ... / door Christoffel Jan Janse.

  • Janse, Chris J.
Date:
1987
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: DNA synthesis in malaria parasites during sexual and erythrocytic asexual development : proefschrift ... / door Christoffel Jan Janse. Source: Wellcome Collection.

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    3 the development of techniques for in vitro sexual development (reviewed by Trigg, 1985). For studies on the genetics and on the molecular basis of cell differentia¬ tion it is most important to understand how the genetic material is organ¬ ized during the life cycle, e.g. the chromosome number, the ploidy of each parasite stage, the time and rate of DNA synthesis, the time at which meiosis occurs, etc. Several cytological studies have been made on the genome of malaria parasites but disappointingly little information on these points has been obtained (see chapter 1.2). This is mainly due to the unusual condensation pattern of the parasitic DNA. Chromosomes of malaria parasites do not condense prior to mitosis (Sinden, 1978), which precludes easy establishment of molecular karyograms by conventional cytological techniques. In the present study we determined, as a first step towards a better understanding of the organization of the genetic material of malaria para¬ sites, the ploidy of the successive developmental stages and the time and rate of DNA synthesis during asexual and sexual development, using cytophotometric methods. In contrast to biochemical methods, cytophotometry allows the measurement of the DNA content of individual cells, that can be identified morphologi¬ cally, thus avoiding sources of errors related to purification of cells, cell synchronization, inaccuracy of cell counting and loss of DNA during ex¬ traction. We mainly used the Feulgen-pararosaniHne reaction procedure. Although the physicochemdcal background of the Feulgen staining reaction has not been completely elucidated, it is highly specific and - when prop¬ erly controlled - stoichiometric for DNA. Therefore it has become a valu¬ able tool and one of the most widespread methods in quantitative cytophotometry (see Schulte (1986) for staining properties ). Moreover, it has been shown to be sufficiently sensitive to be applicable to organisms with very small genome sizes (CorneUssen et al., 1984). This study is confined to DNA synthesis during erythrocytic asexual and erythrocytic as well as post-erythrocytic sexual development.