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J F Meis

Publications and source records attributed to J F Meis.

At least 163 records · Page 9Linked to original sources
PubMed1989

Plasmodium falciparum ookinetes migrate intercellularly through Anopheles stephensi midgut epithelium.

The migration of Plasmodium falciparum and P. berghei ookinetes through the midgut epithelium in Anopheles stephensi was studied by transmission electron microscopy. With ruthenium red (RR) staining, the results of previous studies were confirmed: P. falciparum ookinetes take an intercellular route through the midgut epithelium. In the same mosquito species, the rodent parasite P. berghei appeared to take an intracellular position, as previously suggested by other authors. The intra- or intercellular ookinete migration of P. berghei or P. falciparum, respectively, can perhaps be related to the higher mortality of P. berghei-infected mosquitoes within the first 2 days of infection. Evidence is presented that oocyst capsule formation begins as early as during the migration of the ookinete. After localization between the epithelial cells and the midgut basal lamina, the rapidly expanding oocyst stretches the overlying layer of the latter at the haemocoelic surface while a new basal lamina is generated between the oocyst and epithelial cell.

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PubMed1989

Immunogold determination of Plasmodium falciparum circumsporozoite protein in Anopheles stephensi salivary gland cells.

The distribution of circumsporozoite (CS) proteins of Plasmodium falciparum sporozoites was observed during the passage of mature sporozoites in the hemocoel of Anopheles stephensi and during their entrance and sojourn in the salivary gland cells (SGC). The CS protein was visualized using a monoclonal antibody (3SP2) and immunogold labeling on ultrathin cryosections. In the hemocoel the sporozoites cease synthesizing CS protein, and some of it is shedded resulting in a patchy labeling pattern on the outer pellicular membrane. No internal labeling was observed. The sporozoites enter the SGC by puncturing the basal or lateral membrane. Inside the SGC, CS protein synthesis is turned on again; the Golgi system, nuclear envelope and all 3 pellicular membranes contain CS immunoreactivity. In the last phase of maturation, micronemes display abundant CS immunoreactivity. Rhoptries also show some immunogold labeling, but not as much as the micronemes.

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PubMed1988

Immunogold localization of circumsporozoite protein of the malaria parasite Plasmodium falciparum during sporogony in Anopheles stephensi midguts.

The occurrence of the circumsporozoite (CS) proteins of Plasmodium falciparum sporozoites was monitored during sporogonic development in Anopheles stephensi mosquitoes. Using a monoclonal anti-CS protein antibody (3Sp2) and immunogold labeling on ultrathin cryosections it was found that CS protein is synthesized in immature oocysts from day 6 onwards when there are not yet signs of sporozoite formation. The CS protein is rapidly incorporated in the oocyst plasmalemma, which subsequently invaginates into the parasite. In the oocyst only the external sporozoite membrane contains CS protein. The inner pellicle membranes, rhoptries and micronemes do not react with monoclonal antibody (MoAb) 3Sp2.

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PubMed1987

Ultrastructural studies on the interaction of Plasmodium falciparum ookinetes with the midgut epithelium of Anopheles stephensi mosquitoes.

The interaction of Plasmodium falciparum ookinetes with the midgut epithelium of Anopheles stephensi is described by electron microscopy. Plasmodium falciparum ookinetes have been traced during the early stages of invasion and localization beneath the basal lamina of the midgut. It is generally assumed that ookinetes break through two membranes to reach the basal lamina of the midgut epithelium by an intracellular route. In the present study evidence is presented that the ookinete takes an intercellular route in traversing the epithelial layer. Compared to the mode of penetration and intracellular development of sporozoites and merozoites, an intercellular route for penetration of the ookinete is not inconsistent with its further extracellular development.

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PubMed1987

Cellular response against exoerythrocytic forms of Plasmodium berghei in rats.

Rats were infected with Plasmodium berghei sporozoites, and 47, 51, and 57 hr later exoerythrocytic parasites were examined by electron microscopy. At 47 hr, approximately 30% of nearly mature exoerythrocytic parasites were degenerating and were surrounded by a cellular infiltrate of Kupffer cells, monocytes, monocyte-derived macrophages, and neutrophils. Neutrophils appeared to be actively ingesting electron-dense fuzzy parasite material which was normally present in the parasitophorous vacuole. By 51 hr other mononuclear cells penetrated with filopodia between the host hepatocyte and exoerythrocytic parasite, and directly into the exoerythrocytic parasite. Exoerythrocytic parasites that formed merozoites at 51 hr lacked any notable cellular infiltration.

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PubMed1986

Fine structure of the malaria parasite Plasmodium falciparum in human hepatocytes in vitro.

Recent advances in the ability to culture the hepatic forms of mammalian malaria parasites, particularly of the important human pathogen Plasmodium falciparum have provided novel opportunities to study the ultrastructural organisation of the parasite in its natural host cell the human hepatocyte. In this electron-microscopic and immunofluorescence study we have found the morphology of both parasite and host cell to be well preserved. The exoerythrocytic forms, which may be found at densities of up to 100/cm2, grow at rates comparable to that in vivo in the chimpanzee. In the multiplying 5- and 7-day schizogonic forms of the ultrastructural organisation of the parasite bears striking resemblances to other mammalian parasites, e.g., the secretory activity and distribution of the peripheral vacuole system, but also homology with avian parasites, e.g., in nuclear and nucleolar structure and mitochondrial form. The latter homologies support earlier suggestions of the close phylogenetic relationship of P. falciparum with the avian parasites. Evidence is also presented showing the persistence of the cytoskeleton of the invasive sporozoite within the cytoplasm of the ensuing rapidly growing vegetative parasites.

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PubMed1986

Synchronization of Plasmodium falciparum gametocytes using an automated suspension culture system.

An automated suspension culture system for the cultivation of Plasmodium falciparum is described which retains a degree of flexibility which is absent in other automated culture apparatuses. Not only does this system of cultivation promote rapid multiplication of asexual parasites but also permits the development and maturation of gametocytes. Using a combination of gelatin flotation and N-acetyl glucosamine treatment synchronous development of gametocytes was achieved. The total time for gametocyte maturation in vitro under the conditions provided was 7 days. Stages II and V required 48 h for development whilst I, III and IV needed 24 h each. Mature microgametocytes were relatively long lived in comparison with macrogametocytes. Electron microscopic study of the synchronized stages confirmed the observations of Sinden (1982) but, in addition, we noted the presence of Garnham bodies, a cytostome in all stages and dense spherules in stages I-III similar to the fenestrated buttons in sporozoites and exoerythrocytic forms. The relationship between the number of osmiophilic bodies in the mature gametocytes and their ability to escape from the red cell is reaffirmed.

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PubMed1986

Organization of the exoerythrocytic stage of the rodent malaria parasite Plasmodium berghei. A cytochemical study.

With the osmium tetroxide-zinc iodide impregnation technique the visualization of the internal organization of the exoerythrocytic form of the rodent malaria parasite Plasmodium berghei was improved. Osmium impregnation leached the ground matrix of the parasite thereby displaying a system of intermediate-sized filaments. Because microtubules are only present as part of the mitotic spindle and as remnants of the sporozoite cytoskeleton, the observed intermediate-sized filaments comprise most of the cytoskeletal organization of the liver stage malaria parasite.

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PubMed1985

Transformation of sporozoites of Plasmodium berghei into exoerythrocytic forms in the liver of its mammalian host.

Intrahepatocytic transformation in vivo of the rodent malaria sporozoite of Plasmodium berghei, into the young trophic exoerythrocytic tissue stage was studied by immunofluorescence, light- and electron microscopy. The first 20 h of intracellular life were involved entirely in dedifferentiation with limited proliferation of organelles. From about 20 h onwards nuclear division commenced, rough endoplasmic reticulum became markedly expanded, and mitochondria increased in numbers. However, remains of the sporozoite pellicle (i.e., inner membranes and subpellicular microtubules) persisted for at least 28 h, which correlates with the persisting reaction of young exoerythrocytic forms with antisporozoite antibodies. In general, the basic mechanism of transformation resembles that of the ookinete into oocyst and that of the merozoite into erythrocytic trophozoite.

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PubMed1985

Electron microscopic studies on the interaction of rat Kupffer cells and Plasmodium berghei sporozoites.

The interactions between Plasmodium berghei sporozoites and Kupffer cells in rat liver were studied by transmission electron microscopy. Between 10 and 45 min after inoculation, sporozoites were found in the process of entering Kupffer cells and inside phagolysosomes. The sporozoites entered the Kupffer cells by phagocytosis as determined by the presence of pseudopods and local accumulations of aggregated microfilaments and the resulting exclusion of other organelles in the phagocyte cytoplasm beneath the attached parasite. Sporozoites were taken up either with their anterior end first, or backwards. Scanning electron microscopy of in vitro sporozoite Kupffer cell interaction confirmed these observations. It was concluded that sporozoites are taken up in a normal phagocytic way by the Kupffer cells, regardless of their initial place of contact or position. Thirty min after inoculation sporozoites found in phagolysosomes were still morphologically intact but after 45 min we could encounter completely digested sporozoites.

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PubMed1985

Fine structure of exoerythrocytic merozoite formation of Plasmodium berghei in rat liver.

The fine structure of exoerythrocytic merogony of Plasmodium berghei was studied after perfusion-fixation of rat livers from 51 h post-inoculation onwards. Meroblast formation was effected by clefts originating from the parasite plasmalemma and by fusion of vacuoles with each other. Invaginations at the periphery resulted in labyrinthine structures providing the parasites with an enormous increase in surface area, which might facilitate exchange of metabolites. When the parasitophorous vacuole membrane collapsed, the newly formed merozoites were lying free in the hepatocytic cytoplasm, which degenerated until the merozoites were sticking together by a stroma, obviously a remnant of the host hepatocyte. Groups of merozoites, still kept together by the spongy stroma, were subsequently released in the bloodstream. At 53 h most of the developmental stages leading to the release of merozoites could be found and thereafter parasite numbers decreased while large granulomas became apparent.

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PubMed1984

Histochemical observations on the exoerythrocytic malaria parasite Plasmodium berghei in rat liver.

Enzyme histochemical methods were performed on sporozoite infected liver tissue of rats in order to gain insight into the nutrition and metabolism of exoerythrocytic forms of Plasmodium berghei. The following enzymes were demonstrated in the hepatocytic stages of the parasites, obtained 41 and 48 h after inoculation of sporozoites: acid phosphatase, cytochrome oxidase, NADH-tetrazolium reductase, succinate dehydrogenase, NAD+ and NADP+ dependent isocitrate dehydrogenase, NADP+-dependent malate dehydrogenase, lactate dehydrogenases, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenases and alpha-glycerol-phosphate dehydrogenase. The results suggest that a conventional Embden-Meyerhoff pathway, pentose phosphate pathway and Krebs' citric acid cycle may in part be present in these exoerythrocytic parasites. Alkaline phosphatase, nucleoside polyphosphatase, 5' nucleotidase, glucose-6-phosphatase, alpha-glucan phosphorylase, NAD+ dependent malate dehydrogenase, amino-peptidase M and non-specific esterases were not detected by our techniques in the parasite. The enzyme distribution of this intrahepatocytic malaria parasite revealed by histochemistry is compared with the enzyme distribution in the other phases of the parasite's life cycle.

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