All ETDs from UAB

Advisory Committee Chair

Julia M Gohlke

Advisory Committee Members

Michelle V Fanucchi

Mickie L Powell

Document Type

Thesis

Date of Award

2014

Degree Name by School

Master of Science in Public Health (MSPH) School of Public Health

Abstract

Methylmercury (MeHg) is a known neurotoxicant and bioaccumulates in fish, with exposure to humans in utero being of highest concern. Iron deficiency (ID) accounts for approximately 50% of anemia cases. Anemia is estimated to affect 1.62 billion people worldwide, and is particularly problematic during pregnancy and early life. Previous studies have shown that ID exacerbates toxicity associated with exposure to metals, including lead, manganese, and cadmium. The overall purpose of this thesis research is to investigate the interaction between a low-iron (Fe) diet and early-life exposure to MeHg in Daphnia pulex. I hypothesized when D. pulex are fed a low-Fe diet, the toxicity associated with early exposure to MeHg will increase. D. pulex were fed a standard and low-Fe diet with freshwater algae, Ankistrodesmus falcatus, cultured in a standard or low-Fe media. Early-life exposure to MeHg (1600 ng/l) was administered (for 24 hrs in the first 72 hrs. of life), and its effects on lifespan, maturation time, average brood size, and reproduction rate were evaluated. In addition, the effects of low-Fe diet and MeHg exposure on lipid storage were measured using image analysis of Oil Red O (ORO) staining and were also examined through biochemical quantification of total triacylglycerol (TAG). Results suggest that D. pulex that are fed a standard Fe diet had no significant difference in lifespan or reproduction (average brood size and reproduction rate) compared to Daphnia on a low-Fe diet. Also, there was no difference in maturation time between low and standard-Fe diets of Daphnia as well as between MeHg exposed and vehicle exposed Daphnia fed either diets. However, we observed a significant delay when Daphnia were exposed to either the vehicle or MeHg compared to the no exposure control. Image analysis for lipids stained with ORO suggests an interactive effect of diet and MeHg exposure, with MeHg exposure increasing lipid storage particularly in D. pulex fed a low-Fe diet. Measurement of TAG by using a commercially available kit were not consistent with the ORO results, possibly due to variation introduced from pooled samples and interference from free glycerol in D. pulex.

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