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Orientation of helminths during host seeking
Vojtová, Terezie ; Mikeš, Libor (advisor) ; Horák, Petr (referee)
Helminths are often forced in the environment to search for their host quickly in order to continue the ontogenetic development, or else to finish it. To search for and indentify the host, they use various types of receptors which allow them to provoke a taxes corresponding to the oncoming stimulus and to react to the presence of the host. This thesis includes the summary of the existing knowledge related to the orientation of helminths, the comparison of the mechanisms used by the searching of a host and signals in the environment. In respect to the concept relevant to the helminths, this work concerns trematodes, whose freely movable stadia are miracidium and cercaria, and then monogeneans which are viparous or oviparous with oncomiracidium larva, and nematodes with the third infective larva stage. The representatives of fish parasites of Myxozoans and Ciliophorea are also mentionned, since they use similar mechanisms to look for hosts as helminths. Powered by TCPDF (www.tcpdf.org)
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Production and elimination of superoxide radical in relation to the compatibility of snails and trematodes
Cibulková, Lucie ; Skála, Vladimír (advisor) ; Nývltová, Eva (referee)
Almost all trematodes use snails as the intermediate host in their life cycles. To survive within the host, they have to efficiently avoid defense reactions of its immune system. The most important effector cells, haemocytes, produce reactive oxygen species with the first molecule known as superoxide radical. Various snail species produce different levels of these radicals in relation to the compatibility with the invasive trematode species. The parasite decreases the levels of toxic radicals by using antioxidant enzymes including superoxide dismutase which catalyzes transformation of superoxide radical into hydrogen peroxide. This dismutation reaction is the first step during the oxidative burst and likely influences survival of trematodes within the host. Based on the current knowledge the production and elimination of superoxide radical in relation to the compatibility between snails and trematodes have been described thoroughly for a few models such as for example Biomphalaria glabrata-Schistosoma mansoni. However, this interaction appears to play a key role and, therefore, it deserves more attention in another models as well. Key words: trematodes, snails, compatibility, haemocytes, oxidative burst, antioxidant enzymes, superoxide dismutase, superoxide radical
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Cultivation of Trematodes
Vrbová, Kristýna ; Kašný, Martin (advisor) ; Chanová, Marta (referee)
Many of Trematode species are serious pathogens of human and animals; therefore they are the subjects of intensive investigation. The successful in vitro cultivation of these organisms could represent the first step for further sophisticated experiments focused on characterization of crucial biological processes related to the particular phases of fluke life cycle or for the studies focused on testing the anthelmintic effect of various compounds. This thesis reviews majority of information published in relation to in vitro cultivation of Trematodes. It shows that for many Trematode families is our knowledge of culturing methods very limited. In contrast to the first attempts to cultivate some species of Trematodes about 100 years ago, nowadays we dispose of technologies enabling to cultivate particular live cells isolated from different tissues of flukes. Some of the cultivation media originally used for cell cultures are now commercially available and they were successfully used for cultivation of whole worms. Nevertheless, we still haven't been able to continuously cultivate a Trematode species by using an egg at the beginning and finish with fully developed adult producing eggs. However, there are some partially successful experiments in which development of particular life stages of some flukes has been...
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Early embryonal development and morphogenesis of selected organ systems of the rediae and cercariae of Fascioloides magna.
Pankrác, Jan ; Kašný, Martin (advisor) ; Macůrková, Marie (referee)
Fascioloides magna (giant liver fluke) is a digenetic trematode with two-host life cycle and high veterinary importancy. Typical definitive host is a deer (Cervidae), but many other species from different families can be accidentally infected, for example sheep, goat or cattle. Very important role in the life cycle of F. magna has the first host - fresh water snail of the family Lymnaeidae. Three different life stages of F. magna, two of them with ability of reproduction - sporocysts and rediae develop in the body of snail. The third stage - cercaria is produced by rediae. Cercariae are able to escape from the snail, encyst and become infective for the definitive host. Since the second half of the 19th century many researchers studied the development of particular stages in the first intermediate host, but many characteristics of this process are still not fully understood. This thesis should reveal some of unanswered questions concerning to the reproduction and ontogenetic development of trematodes, which is presented on the examples of three organ systems - muscles, nerves and excretory system of rediae and cercariae of F. magna.
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Determination of gastropods of the genus Radix, the intermediate hosts of trematodes
Mikešová, Kateřina ; Beran, Luboš (referee)
Lymnaeid snails of the genus Radix are common freshwater molluscs of Europe. Formerly, the following species have been reported from the Czech Republic according to the morphology of the shell: R. auricularia, R. peregra, R. ovata and R. ampla. However, recent studies involving molecular data revealed that species determination based on traditional approaches employing morphology of the shell and gonads can be more complicated, confusing and not fully reliable. The shape of the shell is affected by particular life conditions of the snails and proves to be highly variable. The characteristics that can be found on gonads are dependent on the reproductive phase of the snail, and sometimes also on the presence of trematode larval stages, which can cause parasitic castration. Recently, molecular taxonomy is the most reliable approach, especially when a combination of sequences of mitochondrial and nuclear DNA is used. As molecular analyses are relatively time-consuming and expensive, some authors try to find some additional morphological features that could be used for determination of Radix snails in the field, without the need of demanding equipment. Problems in taxonomy and systematics of members of the genus Radix have a practical point in studies of trematode life cycles. From the view of human and...
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Morphology of Fascioloides magna life stages and histopathological changes in selected species of definitive hosts
Košťáková, Monika ; Kašný, Martin (advisor) ; Hodová, Iveta (referee)
Fascioloides magna is a trematode originating in North America. It is a significant pathogen, especially in cervids, but it can also infect ruminants kept for agricultural purposes.Adult trematodes are found in the liver tissue of their definitive hosts, where they can survive for a long period of time and produce large quantity of eggs. Those are passed through bile ducts and intestine with feces into the external environment. This thesis is focused on the morphology of individual developmental stages of F. magna. To this date only very limited number of literary resources concerning the topic had been published. Recorded results are compared with literary resources on Fasciola hepatica, a closely related trematode. The morphological characteristics of the individual developmental stages were studied by using histological, electron-miscroscopical and other methods (fluorescent labelling). The thesis also describes pathological changes of the definitive hosts' liver tissue. By means of the stated methods, the thesis expands the existing knowledge on the morphology of F. magna especially of surface structures and the distribution of the senzoric organs, some of which have been described for the very first time. Powered by TCPDF (www.tcpdf.org)
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Ontogenesis of trematode larval stages of the family Fasciolidae in the intermediate snail hosts.
Pankrác, Jan ; Kašný, Martin (advisor) ; Soldánová, Miroslava (referee)
The family Fasciolidae is an important group of trematodes including serious pathogens of humans and livestock. The life cycle is divided into two phases - sexual reproduction in the definitive host body (large land mammals) and an asexual reproduction in the intermediate host body (aquatic snails of the family Lymnaeidae and Planorbidae). Development within the snail host is characterized by production of large amounts of parasite larvae (sporocyst, rediae, cercariae). Cercariae released from the snail immediately start to transform into metacercariae, the larval stages infectious for definitive host. Snail phase of infection is generally accompanied by number of mostly negative symptoms (massive pathological changes, often followed by reduction of fertility). This summary reveals that current knowledge concerning the ontogenetic development of fasciolids in the intermediate host is uncomplete and unequally investigated. According to this summary is also obvious that some of the published findings are universally valid for all members of the family Fasciolidae and other are characteristic only for particular species.
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Glycocalyx shedding by cercariae of bird schistosomes
Chaloupecká, Jana ; Mikeš, Libor (advisor) ; Štěrba, Ján (referee)
Trichobilharzia spp. are avian schistosomes related to medically important human parasites of the genus Schistosoma. Penetrating cercariae are well known as causative agent of cercarial dermatitis in humans. Cercariae actively penetrate the skin of definitive hosts and transform into schistosomula. This process is preceded by cercarial tail detachment and includes emptying of penetration glands and extensive surface changes. One of these changes is the loss of highly immunogenic glycocalyx which represents a protective coat in the aquatic environment. The glycocalyx has specific composition of saccharide molecules which are bound to lipids or proteins on the membrane of cercarial tegument. There is only limited information about the mechanism of shedding. Hypotheses based on indirect evidences suggest that peptidases or (phospho)lipases from penetration glands could be involved. This work describes the changes in surface glycosylation during transformation of cercariae into schistosomula by fluorescently labelled lectins and monoclonal antibodies against Lewis X antigen. Lectins UEA-I, LTA and PNA have been chosen as markers of transformation of T. regenti. Further, our experiments have been focused on shedding of cercarial glycocalyx. During in vitro induction of penetration gland emptying and...
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Features and functions of glycocalyx of trematode cercariae
Chaloupecká, Jana ; Mikeš, Libor (advisor) ; Kašný, Martin (referee)
Trematodes are parasites from phylum Platyhelminthes which have compex life cycles involving two to four hosts. This work focuses especially on trematodes of the family Schistosomatidae. Their cercariae which leave the snail intermediate host, actively penetrate the skin of definitive hosts and transform into schistosomula. This is accompanied by detachment of cercarial tail and emptying of penetration glands. During transformation, cercarial bodies undergo extensive ultrastructural and molecular changes. One of these changes is the loss of surface glycocalyx which represents a protective coat in the aquatic environment. In glycocalyx shedding, participation of proteolytic enzymes from cercarial penetration glands is expected during invasion of the host. Glycocalyx has specific composition of saccharide molecules which are bound to lipids or proteins on the membrane of cercarial tegument. This work describes the origin, ultrastructure, saccharide composition, function and shedding mechanism of cercarial glycocalyx.
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