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*Dissertation Defense Announcement: To: The George Mason University Community* *Neeraja Podugu PhD Biosciences Candidate * *Date: Monday November 1, 2010 Time: 11:00 a.m. Place: George Mason University ** Room 249, Bull Run Hall Prince William campus <http://www.gmu.edu/resources/visitors/findex.html> Dissertation Chair: Dr. James D. Willett Committee members: Dr. Yuntao Wu, Dr. Jenefir Isbister, Dr. Jennifer Weller * *Title: "Stress Related Changes in Purine, Tyrosine and Trytophan Metabolites of /Caenor/*/*habditis Elegans**"*/ A copy of the dissertation is on reserve in the Johnson Center Library, Fairfax campus. The doctoral project will not be read at the meeting, but should be read in advance. All members of the George Mason University community are invited to attend. /ABSTRACT:/ /Caenorhabditis elegans /has been used as a model organism in many areas of research over the last few decades. This research investigated stress related changes in /C.elegans/ following exposure to different components of /B.anthracis /and varying dosages of lead acetate. Metabolites of purine, tyrosine and tryptophan pathways of /C.elegans/ were measured using/ /high profile liquid chromatography coupled with electrochemical detection. Perturbations in metabolites of these pathways in /C.elegans /were measured and compared to the metabolites of the untreated. /C.elegans / cultures grown under axenic and monoxenic conditions responded differently to the same stressors. The results from this research support the hypothesis that a relationship exists between the initial stress response and the subsequent changes in the metabolic constituents of purine, tyrosine and/or tryptophan pathways of /C.elegans/. The exposure of axenic mixed cultures of /C.elegans /to a /Bacillus anthracis/ three- toxin combination resulted in an acute response showing perturbations in purine, tyrosine and tryptophan pathways. Increasing the concentration of lead affected growth in axenic young, reproductive processes in axenic middle aged after 1.5 days of exposure whereas the adult /C.elegans/ lysed. Perturbations in analytes of purine, tyrosine and tryptophan, as well as unknown analytes specific to the life stage and dosage of lead treatment, were observed. Axenic and monoxenic /C.elegans/ demonstrated time and dose-dependent responses to lead exposure. Axenic /C.elegans/ cultures responded to biological stressors and lead acetate more rapidly than monoxenic cultures, suggesting that axenic cultures could provide a superior model system for measuring acute stress responses. ###