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
  
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 Caenorhabditis 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.

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.