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  • 1
    Electronic Resource
    Electronic Resource
    Azadirachtin Disrupts Formation of Organised Microtubule Arrays during Microgametogenesis of Plasmodium berghei (2002)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 49 (2002), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Transmission of malaria parasites from vertebrate blood to the mosquito vector depends critically on the differentiation of the gametocytes into gametes. This occurs in response to environmental stimuli encountered by the parasite in the mosquito bloodmeal. Male gametogenesis involves three rounds of DNA replication and endomitosis, and the assembly de novo of 8 motile axonemes. Azadirachtin, a plant limnoid and insecticide with an unkown mode of action, specifically inhibits the release of motile gametes from activated microgametocytes but does not inhibit growth and replication of asexual blood stages. We have combined confocal laser scanning microscopy and transmission electron microscopy to examine the effect of azadirachtin on the complex reorganisation of the microtubule cytoskeleton during gametogenesis in Plasmodium berghei. Neither the replication of the genome nor the ability of tubulin monomers to assemble into microtubules upon gametocyte activation were prevented by azadirachtin. However, the drug interfered with the formation of mitotic spindles and with the assembly of microtubules into typical axonemes. Our observations suggest that azadarachtin specifically disrupts the patterning of microtubules into more complex structures, such as mitotic spindles and axonemes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2002.tb00234.x
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  • 2
    Electronic Resource
    Electronic Resource
    SOAP, a novel malaria ookinete protein involved in mosquito midgut invasion and oocyst development (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: An essential, but poorly understood part of malaria transmission by mosquitoes is the development of the ookinetes into the sporozoite-producing oocysts on the mosquito midgut wall. For successful oocyst formation newly formed ookinetes in the midgut lumen must enter, traverse, and exit the midgut epithelium to reach the midgut basal lamina, processes collectively known as midgut invasion. After invasion ookinete-to-oocyst transition must occur, a process believed to require ookinete interactions with basal lamina components. Here, we report on a novel extracellular malaria protein expressed in ookinetes and young oocysts, named secreted ookinete adhesive protein (SOAP). The SOAP gene is highly conserved amongst Plasmodium species and appears to be unique to this genus. It encodes a predicted secreted and soluble protein with a modular structure composed of two unique cysteine-rich domains. Using the rodent malaria parasite Plasmodium berghei we show that SOAP is targeted to the micronemes and forms high molecular mass complexes via disulphide bonds. Moreover, SOAP interacts strongly with mosquito laminin in yeast-two-hybrid assays. Targeted disruption of the SOAP gene gives rise to ookinetes that are markedly impaired in their ability to invade the mosquito midgut and form oocysts. These results identify SOAP as a key molecule for ookinete-to-oocyst differentiation in mosquitoes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03566.x
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  • 3
    Electronic Resource
    Electronic Resource
    Sexual development of malaria parasites is inhibited in vitro by the Neem extract Azadirachtin, and its semi-synthetic analogues (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 120 (1994), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract We have shown that azadirachtin, a compound from the neem tree, Azadirachta indica, and selected semi-synthetic derivatives, block the development of the motile male malarial gamete in vitro. Changes in the hemiacetal group at position C11 in the molecule result in a loss of activity in this assay. The motility of fully formed male gametes, and other selected flagellated cells, is unaffected by azadirachtin in vitro. These findings raise the possibility of developing azadirachtin-based compounds as antimalarials with transmission-blocking potential, as well as permitting the further study of structure-activity relationships in these compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb07044.x
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  • 4
    Electronic Resource
    Electronic Resource
    Immunological Detection of Cytoskeletal Proteins In the Exoerythrocytic Stages of Malaria By Fluorescence and Confocal Laser Scanning Microscopy (1993)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 40 (1993), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Using monospecific antibodies, the presence and distribution of tubulin, actin, myosin, intermediate filaments, and lamins were examined in the exoerythrocytic liver schizont of Plasmodium berghei by conventional indirect fluorescent antibody methods and confocal laser scanning microscopy. the binding reactivity of the antibodies to parasite proteins was determined by Western blot analysis. the localisation of all antibodies in control host hepatocytes followed expected distributions in both uninfected and infected hepatocytes; by contrast, reactivity to the exoerythrocytic schizont was variable. the parasite reacted positively with selected anti-tubulin, -actin, and -myosin antibodies in both fluorescence and Western blot analysis. Anti-lamin antibodies were positive by confocal indirect fluorescent antibody labelling, but no labelling was detected with anti-intermediate filament antibody. Within the technical limits of resolution of the methods as applied to asynchronous parasite infections, not one of the antibodies reacting positively with the parasite by the indirect fluorescent antibody technique could be shown to identify unequivocally the classic architectural features associated with their respective target organelles, i.e. microtubules, stress-fibres or the nuclear envelope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1993.tb04876.x
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of Expression of Two Major Plasmodium berghei Antigens in the Mosquito Vector, Anopheles stephensi (1993)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 40 (1993), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Expression of a 21 kDa determinant (Pbs21), first detected on the surface of ookinetes, and of the circumsporozoite protein (CSP) was studied by immunofluorescence and Western blots during the developmental cycle of Plasmodium berghei in the mosquito A nopheles stephensi. The expression of Pbs21 was predominantly localised on the ookinete surface one day after the infectious blood meal, and thereafter reactivity declined to a minimum on days 2 and 3, the time of onset of oocyst development. A gradual increase in fluorescence was observed on the oocysts from day 6 that was retained until day 17 post-infection. In contrast, sporozoites released from oocysts or salivary glands showed little or no antibody labelling with anti-Pbs21. Circumsporozoite protein was not detectable in any rnidgut preparations until 5–6 days after feeding, when reactivity was observed against immature oocysts. Expression then continued and increased throughout oocyst and sporozoite development. Western blots confirmed that Pbs21 was expressed minimally during the oocyst development but was not detectable in sporozoites. Co-localisation of anti-Pbs21 and anti-CSP monoclonal antibodies to the 50 kDa and 60 kDa bands in Western blots of sporozoite suggests immunological cross-reactivity between the CSP and the anti-21 kDa antibodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1993.tb06109.x
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructural Observations on the Infection of Rat Liver by Plasmodium berghei Sporozoites In Vivo (1983)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 30 (1983), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The invasion of liver parenchymal cells by sporozoites of Plasmodium berghei Vincke & Lips, 1948, was studied in vivo using transmission electron microscopy. Livers of Brown Norway rats were examined 30 and 60 min after intraportal injection of 15 million sporozoites each. Sporozoites found after incorporation into vacuoles in hepatocytes were often located near a bile canaliculus at the lateral cell surface, surrounded by hepatocyte lysosomal structures; however, degradation of sporozoites caused by lysosomal digestion inside hepatocytes was never observed. Due to the crescent shape of sporozoites, serial sections were necessary to demonstrate the actual process of invasion of the hepatocyte. The hepatocyte's plasmalemma appeared to invaginate due to the sporozoite's action, thereby creating a parasitophorous vacuole. It was suggested that the sporozoite actively penetrated the hepatocyte; however, no visible depletion of rhoptries and micronemes was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1983.tb02931.x
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  • 7
    Electronic Resource
    Electronic Resource
    Heterogeneous ribosome populations are present in Plasmodium berghei during development in its vector (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genome of the rodent malaria parasite, Plasmodium berghei, contains two sets of variant ribosomal RNA (rRNA) genes, termed the A and S types, that are expressed predominantly during the vertebrate and mosquito stages of the parasite's development respectively. Using in situ hybridization, we have examined the transcriptional activity of the A- and S-type rRNA genes, and the switch in expression of the ribosome populations that occurs after parasite transmission to the mosquito. By detection of precursor rRNA molecules, we show that A-type rRNA transcription is downregulated throughout development in the mosquito, whereas the initiation of S-type rRNA transcription is linked to the proliferative phase of the oocyst. Mature A-type rRNA persists during development of the zygote into the ookinete/young oocyst. In contrast, mature S-type rRNA is first detectable in young oocysts and is subsequently present at high levels during further development of oocysts and sporozoites. These results demonstrate that the switch in transcription between the A- and S-type rRNA genes is developmentally regulated, taking place only as the parasite begins to proliferate in the mosquito. A-type ribosomes are therefore not only translationally active in the early stages of development in the mosquito, but are also crucial at this phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01167.x
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  • 8
    Electronic Resource
    Electronic Resource
    A malaria scavenger receptor-like protein essential for parasite development (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 45 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Malaria parasites suffer severe losses in the mosquito as they cross the midgut, haemolymph and salivary gland tissues, in part caused by immune responses of the insect. The parasite compensates for these losses by multiplying during the oocyst stage to form the infectious sporozoites. Upon human infection, malaria parasites are again attenuated by sustained immune attack. Here, we report a single copy gene that is highly conserved amongst Plasmodium species that encodes a secreted protein named PxSR. The predicted protein is composed of a unique combination of metazoan protein domains that have been previously associated with immune recognition/activation and lipid/protein adhesion interactions at the cell surface, namely: (i) scavenger receptor cysteine rich (SRCR); (ii) pentraxin (PTX); (iii) polycystine-1, lipoxygenase, alpha toxin (LH2/PLAT); (iv) Limulus clotting factor C, Coch-5b2 and Lgl1 (LCCL). In our assessment the PxSR molecule is completely novel in biology and is only found in Apicomplexa parasites. We show that PxSR is expressed in sporozoites of both human and rodent malaria species. Disruption of the PbSR gene in the rodent malaria parasite P. berghei results in parasites that form normal numbers of oocysts, but fail to produce any sporozoites. We suggest that, in addition to a role in sporogonic development, PxSR may have a multiplicity of functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03118.x
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  • 9
    Electronic Resource
    Electronic Resource
    Plasmodium berghei ookinetes bind to Anopheles gambiae and Drosophila melanogaster annexins (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 57 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Using a proteomic approach we identified polypeptides from Anopheles gambiae and Drosophila melanogaster protein extracts that selectively bind purified Plasmodium berghei ookinetes in vitro; these were two and three distinct polypeptides, respectively, with an apparent molecular weight of about 36 kDa. Combining two-dimensional electrophoresis and MALDI-TOF (matrix-associated laser desorption ionization time of flight) mass spectrometry we determined that the polypeptides correspond to isomorphs of the annexin B11 protein of the fruit fly. When protein extracts derived from A. gambiae and D. melanogaster tissue culture cells were further fractionated, the binding activity matching the annexin protein could be localized in the fraction derived from cell membranes in both diptera. Antibody staining showed that annexin also binds to ookinetes during the invasion of the mosquito midgut. Finally, inclusion of antiannexin antisera in a mosquito blood meal impaired parasite development, suggesting a facilitating role for annexins in the infection of the mosquito by Plasmodium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04664.x
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  • 10
    Electronic Resource
    Electronic Resource
    Sporozoite invasion (1993)
    [s.l.] : Nature Publishing Group
    Nature 362 (1993), S. 26-26 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR — Our understanding of the molecuá-lar basis of the invasion and subsequent development of malaria sporozoites in hepatocytes has been improved by reá-cent reports that two sporozoite surface proteins, CS (ref. 1) and TRAP (ref. 2), both contain a sequence, region II, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/362026a0
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