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Title: Studies on the role of reactive forms of oxygen and nitrogen in insect immunity, with special reference to triatomine-trypanosome interactions
Author: Whitten, M. M. A.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
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The purpose of this study was to investigate the immunological role of superoxide (O2-) and nitric oxide (NO) production in the cockroach, Blaberus discoidalis, and in the host-parasite interactions in the triatomine bugs, Rhodnius prolixus and Dipetalogaster maximus, which are vectors for the Chagas' disease agent, Trypanosoma cruzi. R. prolixus is also a host for the insect pathogen, Trypanosoma rangeli. Induction of O2- generation in response to various in vitro elecitors was observed in the haemocytes and hameolymph of these insects, and additionally in R. prolixus and D. maximus by injecting different strains of T. rangeli or T. cruzi. In B. discoidalis, inhibitor studies identified the source of this O2- as NADPH oxidase, and through Western blotting, the first direct evidence for NADPH oxidase in an invertebrate, was obtained using R. prolixus haemocytes. Inducible NOS activity was indicated by NO oxidation products in R. prolixus haemolymph following trypanosome injections, and by diaphorase staining in B. discoidalis haemocytes. Higher levels of O2- and NO production and melanization in R. prolixus were, in general, associated with lower parasitaemias, suggesting that products of these pathways are determinants of infectivity in the R. prolixus - trypanosome model. Enzyme inhibition assays verified the involvement of NADPH oxidase and NOS in R. prolixus anti-trypanosome defence, and of NADPH oxidase in B. discoidalis antibacterial activity. In vitro assays demonstrated the toxicity of NO and reactive oxygen species to T. rangeli. Finally, T. rangeli antioxidant defences were characterised and quantified in vitro, and suggested that iron-form superoxide dismutase, and especially peroxidase, may be important in determining trypanosome survival.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available