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Thesis (Ph. D.)--University of Adelaide, 1984. / Includes bibliographical references.

Diss.--Bonn, 1824. / "Die XV Maii MDCCCXXIV"

The initiation of further development is fundamental to the infectious processes of parasitic nematodes. I have examined early developmental activation of Trichinella spiralis larvae during host invasion, with particular emphasis on gene regulation and the timing of events. Using a novel approach, changes in tissue specific transcriptional activity were observed in live larvae during the infectious process with the fluorescent nucleic acid dyes SYTO12 and acridine orange. Simultaneously, the metabolic switch from anaerobic metabolism, characteristic of the infective stage, to aerobic metabolism, as found in the enteral stages, was tracked by measuring activities of the key regulatory enzymes phosphoenolpyruvate carboxykinase and pyruvate kinase, as well as isocitrate dehydrogenase (NADP) activity, and used as a co-indicator for developmental activation. Both metabolic enzyme activities and transcription patterns were found to change in response to host death, liberation from the nurse cell, and exposure to components of the host stomach environment. The role of amphidial neurones in developmental regulation was examined using FITC based labelling, and at least part of the initial developmental processes were discovered to be under amphidial control. Changes to the surface properties of larvae during the process of infection were monitored using the fluorescent lipid probe PKH26, and gave evidence for temporal regulation of activation-related alterations of larval structure and/ or physiology. Further, RNA fingerprinting was carried out to identify specific genes associated with, or regulating, developmental activation. Some putatively differentially expressed transcripts were identified, but could not be completely characterised to date. The results give a clear indication that the activation processes of T. spiralis infective larvae occur at a much earlier time than previously thought, and are stimulated upon liberation of the larvae from the nurse cell inside the host stomach. Further, regulation of development appears to be under transcriptional control, and tissue specific transcription is initiated early during the infectious process, perhaps immediately after release from the nurse cell.

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No description available.

Inoculation experiments were carried out to determine the relation between bark moisture level of certain host species and their susceptibility to facultative parasites. In these experiments, cuttings of 1-to 3-year old host material and the mycelial mat of the pathogens contained in an agar cylinder were used. In the first instance, fungi that were known or found in association with bark lesions were considered: these were Cryptodiaporthe salicella (Fr.) Petrak on Salix scouleriana Barratt (Scouler willow), Dactylosporium sp. and Fusarium sp. on Acer macrophyllum Pursh. (broadleaf maple, Libertella sp. on Cornus stolonifera (Michx.) var. occidentalis (T. and G.) C. L. Hitchc. (western dogwood), Melanconis sp. on Alnus rubra Bong. (red alder). The results demonstrated that fungi normally associated with lesions of living host material proved to be pathogenic when the relative turgidity of the host bark was lowered from the field level of above 80 per cent to the range of 69 to 77 per cent. Secondly, an attempt was made to determine if correlation existed between bark moisture level and canker development by fungi not known, and not found to occur in association with lesions of some hosts. The following fungi and hosts were considered: C. salicella on red alder (Alnus rubra Bong), trembling aspen (Populus tremuloides Michx.), bitter cherry (Prunus emarginata Dougl.), black cottonwood (Populus trichocarpa Torrey and Gray), western dogwood (Cornus stolonifera var. occidentalis), and on broadleaf maple (Acer macrophyllum Pursh.); Fusarium sp. on red alder, bitter cherry, western dogwood, and on Scouler willow; Libertella sp. on red alder, bitter cherry, broadleaf maple, and on Scouler willow; Melanconis sp. on bitter cherry, western dogwood, broadleaf maple and on Scouler willow. It was shown that all of these parasites extended their host ranges, to varying extent when the bark moisture level was reduced to levels within the range of 69 to 77 per cent, or in some instances to the range of 41 to 67 per cent of saturation. Cuttings with as low bark moisture levels as 41 per cent appeared to be viable as indicated by the production of roots and (or) shoots. / Science, Faculty of / Botany, Department of / Graduate

Fasciola hepatica was studied in outbred rats to determine of infection would cause an increase phospholipase B activity and the percentage of periperal blood eosinophilis. A second experiment was performed to investigate eosinophilis.