Fine Structure of Plasmodium mexicanum

Moore, Julie M.; Re, Sinden

doi:10.2307/3278910

Cited by 16 publications

(7 citation statements)

References 11 publications

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“…In the transmission electron microscope mature gametocytes were seen to have the same pellicular structure as immature stages, and the inner double membrane was often involuted as densely staining irregular sacs. Similar involutions have been observed in the saurian parasite P. mexicanum (Moore & Sinden 1974). A micropore was invariably found in the pellicle of the gametocyte, frequently situated opposite the base of Laveran's 'b ib ' (figure 9).…”

Section: (B) Mature Gametocytessupporting

confidence: 69%

Gametocyte and gamete development inPlasmodium falciparum

Sinden

Canning

Bray

et al. 1978

Proc. R. Soc. Lond. B.

163

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The ultrastructural organization of the mature gametocytes of Plasmodium falciparum isolated from the peripheral circulation of naturally infected Gambians is examined and compared with immature forms obtained from the peripheral circulation of a chloroquine treated patient. The latter are recognized as the stage 2 and 3 developmental forms (Hawking, Wilson & Gammage 1971 Trans. R. Soc. trop. Med. Hyg . 65, 549-559) observed by light microscopy and are distinguished in the electron microscope by three characters; (i) they do not fill the host cell, (ii) they contain few, if any, osmiophilic bodies, (iii) they possess an extensive subpellicular tubule system. Maturation (capacitation) of these immature parasites takes many days and is followed by an extended period of maturity during which the gametocytes will exflagellate. Mature macro- and microgametocytes have numerous characters in common with the gametocytes of avian and reptilian Plasmodiidae, namely a tripartite pellicle, cristate mitochondria, a comparatively high density of osmiophilic bodies in the macrogametocyte, cytostomal feeding, Golgi body, and persistent nucleolus in the female gametocyte. These similarities together with the unexpected nuclear changes detected in macrogametogenesis suggest that P. falciparum is best considered as pre-dating the ‘malariae’ and ‘vivax’ groups and not as having evolved from them. Light microscopy, scanning and transmission electron microscopy and videotape analyses of gamete formation were undertaken. Nuclei in the mature gametocytes are Feulgen negative but upon activation rapidly become Feulgen positive. The gametes also are Feulgen positive. The crescentic parasites swell to become large spherical cells and escape from the host cell by osmotic or enzymic activity. The microgametocyte undergoes three mitotic divisions during which the chromosomes are sequentially reduced in number such that ca . 7 are incorporated into each gametic nucleus. The microtubule organizing centre (m. t. o. c.), which in the mature gametocyte is associated with the intranuclear body, is attached to the centriolar plaque of the first division spindle. There it differentiates into kinetosomes which act as foci for the polymerization of axonemes. The kinetosomes and axonemes remain attached to the centriolar plaques during division and are segregated synchronously with the genome at each division. Subsequently one axoneme enters each haploid gamete at exflagellation. Exflagellation is accompanied by a significant reduction in microgametocyte volume which is associated with an increase in density of the cytoplasm. The female gametocyte does not decrease in volume but undergoes nuclear changes in which a single pole of an intranuclear spindle is detected. Comparisons are made with macrogametogenesis in avian malarial parasites from which it is suggested that this spindle, if not half of a normal mitotic spindle, is an atavistic trait. The possibility of a meiotic gametic division is discussed but discounted. The activity pattern of the microgamete was found to be similar to that of other malarial parasites, with states of high and low activity or immobility. High activity, which results in rapid movement through the medium, is produced by long wavelength (12 μm), low amplitude (1.1μm) waves generated at ca . 12 waves per second; low activity, which results in contorted gyrating on the spot, is produced by long wavelength (14.1), high amplitude (2.3) waves produced at ca 1 wave per second. Following an initial period of continuous activity the gamete usually alternates between high and low activity states. Subsequent low activity and immobility is in turn followed by death. Microgamete activity was profoundly affected by the plasma of some patients, presumably as a result of the antigametocyte antibodies present. The microgamete contains a single axoneme, at one end of which lies the kinetosome with the juxtakinetosomal sphere and granule. It is this end which emerges first from the parental gametocyte. A single nucleus is centrally located in many microgametes although 23% are anucleate.

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Section: (B) Mature Gametocytessupporting

confidence: 69%

Gametocyte and gamete development inPlasmodium falciparum

Sinden

Canning

Bray

et al. 1978

Proc. R. Soc. Lond. B.

163

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“…A translation through the virtual sections is presented in Supplementary Movie 4 . Close examination shows that the MTOC has a similar architecture to the centriolar plaque structures that anchor each of the hemispindles in dividing asexual blood stage parasites 10 , 12 , 13 , 15 , 16 . Centriolar plaque density is observed on either side of the nuclear membranes.…”

Section: Resultsmentioning

confidence: 99%

“…In Plasmodium, the nuclear membrane remains intact and the chromosomes are kept in an uncondensed state as nuclear microtubules capture the kinetochores during mitosis 10,11 . An electron-dense acentriolar centrosome (termed the centriolar plaque) is embedded in a pore in the nuclear envelope, and is likely present throughout the cell cycle 10,[12][13][14][15][16][17] .…”

mentioning

confidence: 99%

Repurposing the mitotic machinery to drive cellular elongation and chromatin reorganisation in Plasmodium falciparum gametocytes

Shami

Cho

et al. 2022

Nat Commun

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The sexual stage gametocytes of the malaria parasite, Plasmodium falciparum, adopt a falciform (crescent) shape driven by the assembly of a network of microtubules anchored to a cisternal inner membrane complex (IMC). Using 3D electron microscopy, we show that a non-mitotic microtubule organizing center (MTOC), embedded in the parasite’s nuclear membrane, orients the endoplasmic reticulum and the nascent IMC and seeds cytoplasmic microtubules. A bundle of microtubules extends into the nuclear lumen, elongating the nuclear envelope and capturing the chromatin. Classical mitotic machinery components, including centriolar plaque proteins, Pfcentrin-1 and −4, microtubule-associated protein, End-binding protein-1, kinetochore protein, PfNDC80 and centromere-associated protein, PfCENH3, are involved in the nuclear microtubule assembly/disassembly process. Depolymerisation of the microtubules using trifluralin prevents elongation and disrupts the chromatin, centromere and kinetochore organisation. We show that the unusual non-mitotic hemispindle plays a central role in chromatin organisation, IMC positioning and subpellicular microtubule formation in gametocytes.

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“…During the hemoglobin feeding blood-stage, Plasmodium disassembles the IMC alleviating it of these obstacles to endocytosis (Ferreira et al, 2021). However, the IMC is reassembled during schizogony and merozoite formation where K13 rings are also seen, and micropores are observed in merozoites by TEM also (Moore and Sinden, 1974; Wichers et al, 2021; Yang et al, 2019b). It is likely that these micropores differentiate into cytostomes upon the invasion of new blood cells and ring-stage formation.…”

Section: Discussionmentioning

confidence: 99%

Stable and ancient endocytic structures navigate the complex pellicle of apicomplexan parasites

Kořený

Mercado-Saavedra

Klinger

et al. 2022

Preprint

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Apicomplexan parasites have an immense impact on humanity, but their basic cellular processes are often poorly understood. The sites of endocytosis, the conservation of this process with other eukaryotes, and its functions across Apicomplexa are major unanswered questions. Yet endocytosis in Plasmodium is implicated in antimalarial drug failure. Using the apicomplexan model Toxoplasma, we identified the molecular composition and behavior of unusual, fixed endocytic structures. Here, stable complexes of endocytic proteins differ markedly from the dynamic assembly/disassembly of these machineries in other eukaryotes. Moreover, conserved molecular adaptation of this structure is seen in Apicomplexa, including the kelch-domain protein K13 central to malarial drug-resistance. We determine that an essential function of endocytosis in Toxoplasma is plasma membrane homeostasis, rather than parasite nutrition, and that these specialized endocytic structures originated early in infrakingdom Alveolata, likely in response to the complex cell pellicle that defines this medically and ecologically important ancient eukaryotic lineage.

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Fine Structure of Plasmodium mexicanum

Cited by 16 publications

References 11 publications

Gametocyte and gamete development inPlasmodium falciparum

Gametocyte and gamete development inPlasmodium falciparum

Repurposing the mitotic machinery to drive cellular elongation and chromatin reorganisation in Plasmodium falciparum gametocytes

Stable and ancient endocytic structures navigate the complex pellicle of apicomplexan parasites

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