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Role of catalase and chitinase in the life cycle of Leishmania parasites
Glanzová, Kristýna ; Sádlová, Jovana (advisor) ; Kodym, Petr (referee)
Leishmaniasis is an infectious disease caused by protozoa of the genus Leishmania (Kinetoplastida: Trypanosomatidae) which are transmitted by phlebotomine sand flies (Diptera: Phlebotominae). For the dixenous life cycle, leishmania parasites are equipped with enzymes that facilitate survival in both insect vectors and mammalian hosts. Gene for the enzyme catalase which protects cells from reactive oxygen species by the elimination of H2O2 and is present in related monoxenous trypanosomatids is, however, missing in Leishmania genome. Chitinase can be involved in the interaction of leishmania parasites with chitin-containing structures in sand flies (peritrophic matrix, stomodeal valve). The expression of the enzyme in amastigotes suggests its significant function also in the mammalian host. I tested the role of these enzymes in the life cycle of leishmania by direct comparison of L. mexicana mutants (i) with inserted catalase gene and (ii) with deleted chitinase gene with control groups. I conducted experimental infections of Lu. longipalpis including transmission of leishmania to the hosts by bite, tested the survival of leishmania in macrophages and performed experimental infections of BALB/c mice followed by xenodiagnoses. The experiments confirmed that the presence of catalase in leishmania does...
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A comparison of the peritrophic matrix in four sand fly species (Diptera: Psychodidae) and its role in the Leishmania development (Kinetoplastida: Trypanosomatidae).
Homola, Miroslav ; Sádlová, Jovana (advisor) ; Hypša, Václav (referee)
anglický Phlebotomine sand flies (Diptera: Psychodidae) are the only proven vectors of Leishmania parasites (Kinetoplastida: Trypanosomatidae). In Nematoceran Diptera, including sand flies, adults produce a type 1 peritrophic matrix (PM) which is secreted in response to the distension of the midgut caused by blood meal. The PM is an acellular envelope composed of chitin fibres and proteins, which protects the midgut epithelium against abrasion and pathogens and improves digestion. In hematophagous insects, the PM also plays a central role in heme detoxification. Female sand flies acquire Leishmania with a bloodmeal and the parasites undergo complicated development in their gut finished by the colonization of the stomodeal valve. The PM is one of the most important barriers in Leishmania development and its role in the vector competence of the S. schwetzi is the main topic of this master thesis. The PM's kinetic and morfology in the S. schwetzi is compared with other three sand fly species which differ in susceptibility to L. donovani. The key role of the PM in S. schwetzi vector competence is finally proved by disrupting the PM using the exogenous chitinase from Beauveria bassiana. Under these artificial conditions, the Leishmania parasites (L. donovani and L. major) are able to exit the PM,...
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Peritrophic matrix of bloodsucking Dipteran insects.
Homola, Miroslav ; Sádlová, Jovana (advisor) ; Votýpka, Jan (referee)
The peritrophic matrix is an acellular envelope which surrounds the food bolus in the midgut of many animal species (especially in insects). It fulfils many functions in the midgut e. g.: protects the gut against an abrasion and against toxic substances, improves the digestion of food and protects the gut epithelium against pathogens. The last function might be the main reason of the occurrence of the peritrophic matrix in large amount of insect species. The peritrophic matrix is composed of chitin fibres and proteins. Chitin provides the peritrophic matrix strength and flexibility. Chitin fibres can be organised into three elementary structures: random, hexagonal and squared. The size of pores in peritrophic matrix depends on incorporated proteins - especially peritrophins. These pores determine the permeability of the peritrophic matrix for various penetrating molecules including digestive enzymes. This bachelor thesis is focused on Insecta sensu stricto (Hexapoda) and mainly on the order Diptera, especially bloodsucking species. Following chapters review recent information about the peritrophic matrix and its nomenclature, occurrence, assembling, composition and functions. Powered by TCPDF (www.tcpdf.org)
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