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C J Janse

Publications and source records attributed to C J Janse.

70 records · Page 4Linked to original sources
PubMed1990

Generation of chromosome size polymorphism during in vivo mitotic multiplication of Plasmodium berghei involves both loss and addition of subtelomeric repeat sequences.

Extensive chromosome size polymorphism arises in Plasmodium berghei during in vivo mitotic multiplication. Size differences between homologous chromosomes involve rearrangements occurring in the subtelomeric portions while internal chromosomal regions do not contribute significantly to chromosome size polymorphism. Differences in the copy number of a 2.3-kb subtelomeric repeated unit are shown to correlate with size variations, and in at least one case to account completely for the size difference between two variants of the same chromosome.

Animals↗
PubMed1989

Plasmodium berghei: gametocyte production, DNA content, and chromosome-size polymorphisms during asexual multiplication in vivo.

In this study the DNA content and the karyotype of clones of Plasmodium berghei, which differed in the capability to produce gametocytes, were determined. The DNA content per haploid genome was established by cytofluorometric methods after staining of the haploid merozoites with DNA-specific fluorescent dyes. Field inversion gel electrophoresis was used to establish the number and size of the chromosomes. Parasites of a high gametocyte producer clone (original HP) and a low producer clone (original LP) contained 13 to 14 chromosomes in the size range of 0.5-3.8 megabase. In four independent experiments parasites of the original HP clone were maintained in mice and were mechanically transmitted for prolonged periods of time (up to 90 weeks). During the transmission period the capability to produce gametocytes decreased in all four lines. After mosquito transmission of parasites from these low producer lines, the gametocyte production returned to the level of the original HP clone. The total DNA content per haploid genome of low producer parasites was not significantly different from that of HP parasites. During prolonged periods of asexual multiplication of the HP clone in vivo, changes in the relative size of several chromosomes were detected. Mosquito transmission of the original HP clone did not result in a change of the karyotype. However, novel karyotypes were readily observed after mosquito transmission of parasites of the low producer lines. The decrease of the capability to produce gametocytes did not necessarily involve detectable changes in DNA content or in karyotype.

Animals↗
PubMed1989

Host cell specificity and schizogony of Plasmodium berghei under different in vitro conditions.

Invasion and intra-erythrocytic growth of two strains of Plasmodium berghei (ANKA and K173) were studied under different in vitro conditions. Some important limiting factors for the mass cultivation of this rodent malaria parasite were reconsidered. Parasites of both strains developed normally from ringforms into mature schizonts in RPMI1640 supplemented with Fetal Calf Serum (FCS). At a temperature of 37 degrees C the duration of the schizogonic cycle was comparable to that of the same parasites developing under in vivo conditions. At 27 degrees C, however, the asexual cycle took 60-72 h. In medium supplemented with mouse serum instead of FCS the growth of the parasites was severely inhibited. Parasites of both strains showed a strict preference for reticulocytes. Red blood cells from rats, mice and hamsters were readily invaded by merozoites from both strains. Erythrocytes from rabbits and guinea pigs were resistant to invasion by P. berghei. It is concluded that host cell specificity technically limits the possibilities for mass cultivation of P. berghei. The validity of recent publications, describing alternative culture systems for this rodent parasite, is discussed.

Animals↗
PubMed1989

Evidence for diploidy in metacyclic forms of African trypanosomes.

The DNA contents of bloodstream form trypanosomes (life cycle stages circulating in the blood of the vertebrate host) of four African Trypanosoma species and of metacyclic forms (the life cycle stage that is injected into the vertebrate by the tsetse fly during its bite) of the same four species were measured by cytofluorometry of individual cells or nuclei. The results showed unambiguously that the metacyclic forms cannot be considered to be products of meiosis containing only half of the DNA of bloodstream forms, in contrast to what was previously reported for Trypanosoma brucei [Zampetti-Bosseler, F., Schweizer, J., Pays, E., Jenni, L. & Steinert, M. (1986) Proc. Natl. Acad. Sci. USA 83, 6063-6064] during an attempt to localize the gametes in the life cycle after experimental evidence of sexual gene exchange in this parasite was reported.

Animals↗
PubMed1988

DNA synthesis in gametocytes of Plasmodium falciparum.

The DNA content of Plasmodium falciparum gametocytes during intra-erythrocytic development and during gametogenesis was established by cytophotometric methods. Intraerythrocytic micro- and macrogametocytes (Stage I-Stage VB) contain about twice the amount of DNA of haploid sporozoites and ringstages, indicating that DNA is synthesized during transformation of ringforms into Stage I gametocytes. Microgametocytes, after activation at pH 8, rapidly duplicate their genome several times, while the DNA content of macrogametocytes remains constant during gametogenesis.

Animals↗
PubMed1987

Plasmodium species: flow cytometry and microfluorometry assessments of DNA content and synthesis.

Fluorescence intensities were established by flow cytometry of different erythrocytic stages of Plasmodium berghei after staining of their DNA with Hoechst-33258 or Hoechst-33342. Parasites were obtained from highly synchronized infections or in vitro cultures. Most fluorescence measurements were performed using a low cost, clinical flow cytometer, equipped with a mercury arc lamp. Cells infected with P. berghei could be readily distinguished from uninfected cells on the basis of Hoechst-DNA fluorescence and single, double, and triple ring infected cells were separated clearly. The relative fluorescence intensities of different developmental stages (merozoites, ringforms, trophozoites, schizonts, and gametocytes) corresponded closely to the relative DNA contents of these stages as measured by microfluorometry. Flow cytometry appeared to be a sensitive and rapid method to measure DNA synthesis during asexual development; a C50 value of 5 microM of aphidicolin, a specific inhibitor of DNA synthesis, was established. Vital staining of parasites in culture was possible with both Hoechst dyes. After removal of Hoechst-33258, normal in vitro development of the stained parasites was observed. After Hoechst staining, the haploid ringforms of P. vivax showed slightly less fluorescence (15%) than ringforms of P. berghei and P. falciparum. No differences in fluorescence intensity were observed, however, by direct microfluorometry after Feulgen-pararosaniline staining, indicating that all three species have the same DNA content.

Base Composition↗
PubMed1986

DNA synthesis in Plasmodium berghei during asexual and sexual development.

DNA contents of individual stages of Plasmodium berghei were measured by direct microfluorometry after Feulgen-pararosaniline (SO2) staining. Sporozoites, intra-erythrocytic ringforms and trophozoites (until at least 15 h after invasion) are haploid and non-synthesizing DNA. DNA is synthesized just before and during schizogony, which takes 4-6 h. Genome duplication and segregation are alternating events throughout this process. Mature micro- and macrogametocytes have DNA contents between the haploid and diploid value; most, if not all of the DNA in excess of the haploid value is synthesized during the last 5-10 h of maturation. During gametogenesis microgametocytes within 8-10 min synthesize DNA steadily and at a very high rate to more than the octoploid value while the DNA content of macrogametocytes remains constant. Fertilization in vitro takes place within 1 h after gamete formation. Within 2 h and coinciding with the onset of meiosis the zygote then synthesizes DNA up to almost the tetraploid value, after which synthesis stops during ookinete development. All the above mentioned processes of DNA synthesis are reversibly inhibited by aphidicolin (C50 from 3-13 microM). From the rate of DNA synthesis during microgametogenesis we calculated a minimum of 1300 origins of replication in the haploid genome of P. berghei.

Animals↗
PubMed1986

Mitomycin-C is an unreliable inhibitor for study of DNA synthesis in Plasmodium.

Cytophotometric studies on DNA synthesis during asexual and sexual development of Plasmodium berghei contradicted earlier conclusions on DNA synthesis in Plasmodium which were largely based on experiments in which mitomycin-C had been used as a DNA replication inhibitor. Therefore, the effect of mitomycin on intra erythrocytic asexual development and on microgametogenesis, fertilization and zygote/ookinete development of P. berghei was studied in vitro. All DNA-synthesizing stages (schizonts, exflagellating microgametocytes and zygotes) and also DNA synthesis itself in all such stages, are totally unaffected by mitomycin concentrations 10 times higher than that which inhibits normal development of the non-DNA-synthesizing rings and trophozoites. The results are explained by the mode of action of mitomycin.

Animals↗
PubMed1985

In vitro formation of ookinetes and functional maturity of Plasmodium berghei gametocytes.

In vitro formation of Plasmodium berghei ookinetes was studied. Gametocytes produced in vitro were obtained from heart and tail blood of Swiss mice and from blood removed from mosquitoes directly after feeding on these mice. In vitro produced gametocytes were obtained from short-term cultures of the erythrocytic stages of P. berghei. Reproducible ookinete production was obtained in medium RPMI 1640, pH 7.8-8.0, using in vivo and in vitro produced gametocytes. The morphology of developmental stages of ookinetes and degenerate forms at the light microscope level is described. More ookinetes were produced in medium RPMI 1640 compared to MEM and ookinete yield--defined as the ratio between the number of in vitro produced ookinetes/10(5) erythrocytes and the number of exflagellations/10(5) erythrocytes in the infected blood--increased with lower erythrocyte densities in the cultures within the range of dilutions tested. A linear relationship existed between gametocytaemia and the number of ookinetes produced. The methods for in vitro ookinete formation and for estimating ookinete yields enabled us to study aspects of functional maturity of gametocytes independent of mosquitoes. The numbers of exflagellating gametocytes and in vitro ookinete yields in tail blood corresponded with those in heart blood and blood ingested by mosquitoes, suggesting a random distribution of functionally mature gametocytes within the vertebrate host.

Animals↗
PubMed1985

Development of Plasmodium berghei ookinetes in the midgut of Anopheles atroparvus mosquitoes and in vitro.

Plasmodium berghei ookinete formation in vitro and within the midgut of susceptible Anopheles atroparvus were compared. No significant morphological differences were seen, except that in vitro development was more synchronized and less degenerating forms occurred. In vitro ookinete yields were 4-31 times higher and less variable than those in vivo. Mosquitoes of a susceptible and of a refractory line of A. atroparvus were simultaneously fed on the same host or via a membrane with the same suspension of in vitro-formed mature ookinetes. Up to 100% of mosquitoes of the susceptible line produced oocysts, mostly in high numbers, whereas infection rates and numbers of oocysts produced in mosquitoes of the refractory line were lower and much more so after host feeding than after membrane feeding of mature ookinetes, indicating that refractoriness does not depend on a single process of inhibition.

Animals↗
PubMed1985

Synchronized erythrocytic schizogony and gametocytogenesis of Plasmodium berghei in vivo and in vitro.

Both asexual and sexual development of Plasmodium berghei was synchronized without chemical intervention using in vitro culture techniques. Combined in vivo and in vitro experiments were performed on the relationship between age, morphology and maturity of gametocytes. Schizogony took 22-23 h in the experiments. At 26 h post-invasion (p.i.) the first males became capable of exflagellation. By 20 h p.i. the first gametocytes were recognizable in Giemsa-stained smears but the sex was hardly distinguishable until maturity (26 h p.i.). Survival time of gametocytes was estimated at 26 h in vitro (half-life 13 h) and the same survival time was suggested for gametocytes in vivo. Schizonts of P. berghei apparently disappeared from the peripheral circulation upon maturity, rupturing almost immediately. Mature schizonts in vitro persisted up to 48 h p.i. in non-agitated cultures. No evidence was collected for sequestration of any sub-population of gametocytes.

Animals↗