The release of genome sequence information is revolutionising the study of helminth parasites by providing important datasets for comparative genomics, allowing the comprehensive analysis of signalling pathways that regulate nematode development. Much of the current knowledge of nematode signalling pathways is based on studies of the free-living model Caenorhabditis elegans. The recent availability of the Trichinella spiralis genome sequence presented an opportunity to study signalling pathways of this, and other, parasitic nematodes, providing a phylum-wide overview of a given signalling pathway. The transforming growth factor-β (TGF-β) ligands are a superfamily of structurally related polypeptides that regulate a wide range of cellular processes in animal tissues. Since the discovery that the TGF-β daf-7 regulates the developmentally-arrested dauer stage in C. elegans, there is the potential for TGF-β signalling to regulate developmental arrest, parasite development and even host-parasite communication in T. spiralis and other nematodes. In the present study, thirteen genes encoding putative TGF-β signalling components, from T. spiralis, have been identified and characterised. Phylogenetic analysis suggests that daf-7 is not conserved beyond C. elegans and that functional extrapolation from C. elegans biology to distantly-related nematodes is difficult. Furthermore, the analysis herein shows a high level of divergence among parasitic nematode TGF-βs. Since the last common ancestor of T. spiralis and C. elegans was the ancestor of the entire nematode phylum, these comparisons allow speculation on the TGF-β signalling networks of the ancestral nematode and provide information on the emergence of TGF-β signalling in animals. ES products from T. spiralis are shown to be capable of interacting directly with mammalian cell receptors and utilise their receptors to control gene expression in vitro. This presents the possibility that these TGF-β ligands may play a part in the formation and maintenance of the host-parasite complex.

No description available.

by Tam Chi Hang, Frankie. / "August 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 162-174). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The infectious first-stage larvae of the nematode Trichinella spiralis is an intracellular parasite of altered skeletal muscle. Invasion of the muscle cell initiates a series of morphological changes in the host muscle cell which ultimately results in a specialized unit called the nurse cell. The completed nurse cell consists of a collagenous capsule, matrix of altered sarcoplasm, and a circulatory rete. The purpose of this study was to determine the types of collagen present in the nurse cell capsule. Additionally, the presence of the gl ycoproteins, laminin and tenascin was determined. This study also sought to demonstrate the location of the selected extracellular matrix proteins within the capsule. Nurse cells were isolated from infected host muscle by sequential protease treatment with pronase, collagenase, and hyaluronidase. Nurse cells were digested with pepsin to produce characteristic pepsin-resistant triple helical fragments of collagen. The nurse cellpepsin digest was characterized by SDS-page, under reduced and nonreduced conditions, with type VI collagen and the ala2a3 chains of type XI collagen. Frozen tissue sections of infected and non-infected rat diaphragms were screened with specific polyclonal antibodies against types I, m, IV, V/Xl, and VI collagen, laminin, and tenascin. Indirect immunofluorescence using FITC secondary antibodies was used to locate the protein in the capsule and host tissue. SDS-page of the nurse cell-pepsin digest produced an electrophoretic pattern of resistant fragments characteristic for types I, III, IV, V, and VI collagen. Additionally, fragments migrated with an apparent molecular weight expected for pepsin resistant fragments of laminin. Indirect immunofluorescence showed types I, III, IV, and VI collagen, and laminin were distributed throughout the capsule. Serum No. 4876, which recognizes type V /XJ collagen, localized to the larvae. Tenascin failed to stain the nurse cell or host tissue. The results show that the capsule is a heterogenic structure with types I, III, IV, V, and VI collagens, and laminin distributed throughout the structure. The immunolocalization of Serum No. 4876 to the larvae suggests that a nematode collagen shares an amino acid sequence in common with mammalian type V /XI collagen.

Neutrophils accumulate around Trichinella spiralis larvae encysted in skeletal muscle cells of the host. The magnitude of the neutrophil infiltration follows a pattern relating to the stage of infection of T.spiralis. This study was performed to determine if there are factors chemotactic for neutrophils present in the sera of mice infected with T.spiralis, and if present, to compare the chemotactic potential of sera from several time points during the infection. Female MRL++ mice hosted the T.spiralis infection and provided neutrophils for all experiments. The chemotactic potentials of sera were tested by placing 150 ul of serum collected at zero, four, 11, or 28 days following initial infection of the mouse with T.spiralis, into the bottom well of a modified Boyden chamber called a deep well chemotaxis chamber. Next a PVP-free polycarbonate micropore membrane with a pore size of 5 um was placed over the bottom well. The top chamber was then fastened to the bottom well and filled with a neutrophil suspension which was obtained by gradient layer centrifugation using the NIM • 2 step gradient reagent system. A cover glass was placed over the opening of the top well and the entire apparatus was incubated at 37°C under 5% C02 in a humidified incubator for four hours. Following the incubation cells which had migrated through to the bottom well were counted using a hemocytometer and the membranes were stained with Diff Quick. The results demonstrate that there are factors present in the sera of mice infected with T.spiralis that elicit the chemotactic response of neutrophils in vivo. This work also demonstrates that sera from mice infected 11 and 28 days are significantly more chemotactic for neutrophils than are sera from uninfected mice and mice infected four days. These findings correlated with the histologic appearance of the infected skeletal muscle at four, 11 and 28 days post infection as determined by other members of our laboratory. The chemokines IL-8 and KC, and other chemotactic factors such as C5a are discussed as potential mediators of the neutrophil chemotaxis found in this experiment.

Thèse de doctorat : Parasitologie : Paris 12 : 2005. / Thèse uniquement consultable au sein de l'Université Paris 12 (Intranet). Titre provenant de l'écran-titre. Bibliogr. : 192 réf.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 121-131).

published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

No description available.