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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    10 gametocyte production varied significantly (Van der Ploeg et al., 1985; С. Frontali and M. Ponzi, pers. comm.). DNA synthesis Malaria parasites do not use exogenous pyrimidines, in contrast to purines, for nucleic acid synthesis (for review see Homewood and Neame, 1980), but are dependent on ^ novo synthesis of pyrimidines. Almost all studies on DNA synthesis in malaria parasites deal with time and rate of incorporation of radio-labeled precursors into DNA during asexual intra-erythrocytic development. Gutteridge and Trigg (1970) and Jung ^ al. (1975) did not find a clear periodicity, but most other workers using synchronized infections demonstrated that DNA synthesis starts during the later part of trophozoite development and is highest during schizogony (Conklin et al., 1973; Newbold et al., 1982; Sodeinde & Luzzatto, 1982; Inselburg et ad., 1984; Gritzmacher et 1984; Waki et al., 1985). DNA synthesis in this phase could be inhibited by aphidicoHn (Inselburg et al., 1984), a specific inhibitor of polymerase-a (Ikegami et al., 1978), the enzyme primarily responsible for DNA chain elongation in all kinds of eukaryotes (Scovassi et al., 1980). This suggests that Plasmodium has a similar DNA polymerase. DNA synthesis during sexual reproduction has never been demonstrated directly. It has been suggested that both sexes of gametocytes replicate their genome during early development, resulting in transiently diploid female and in octoploid male gametocytes, since young gametocytes of P. falciparum contain intra-nuclear microtubules (Sinden, 1982) and are killed by the DNA synthesis inhibitor mitomycin-С (Sinden & Smalley, 1979), while exflagellation in P. yoeUi is insensitive to it (Toye et al., 1977). The gametes of both sexes are assumed to be haploid as a result of so-called cryptomitosis in the intra-erythrocytic female gametocyte (Sinden, 1983) and of rapid segregation of the 8 preformed haploid genome comple¬ ments in the male gametocyte during exflagellation.