All ETDs from UAB

Advisory Committee Chair

Dale A Dickinson

Advisory Committee Members

Michelle V Fanucchi

Julie M Gohlke

Tonia S Schwartz

Document Type

Thesis

Date of Award

2016

Degree Name by School

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

Abstract

As a necessary micronutrient, seleno-L-methionine (SeMet) exhibits a U-shaped dose-response with deficiency and toxicity leading to adverse health outcomes. Some studies suggest dietary selenium may offer protection against toxicity from other metals, but excessive dietary levels can also lead to toxicity. In addition, increased maternal age has been shown to increase the risk of adverse developmental outcomes. We hypothesize that older maternal age will increase susceptibility in offspring exposed to toxic concentrations of SeMet. The goal of this project was to evaluate the effects of SeMet treatment on lifespan and determine if the effects are altered by maternal age using Daphnia pulex as the model system. Offspring were obtained from our maternal populations (N=4) when the mothers were 8 days of age (early life brood) and when the mothers were 32 days of age (late life brood). The offspring from each brood were randomized into the 0-μg SeMet/L, 1-μg SeMet/L, and 4-μg SeMet/L treatment groups. The effect of selenium treatment on offspring from early and late life broods was quantified using lifespan measurements (N=25 per treatment) as well as resistance to heat induced stress via mortality (N=80 per treatment) and presence of offspring (N=8 per treatment). Selenium tissue content (N=4 per treatment) was measured in 5-day old and 15-day old offspring to verify selenium absorption. There were not significant differences in total Se tissue content between SeMet treatment or maternal population age groups. However, the total Se tissue content increased with increasing treatment. There was not a significant difference in lifespan or total reproduction between individuals from the 0-μg SeMet/L treatment versus 1-μg SeMet/L treatment or among maternal population age. Within the 1-μg SeMet/L treatment groups, the offspring from the later life brood began reproducing later than the offspring from the early life brood. The offspring from the highest treatment group (4-μg SeMet/L) did not reproduce and had significantly shorter lifespans in comparison to the 0-μg SeMet/L or 1-μg SeMet/L treatment groups. However, there was not a significant effect of maternal age. In response to heat induced stress, the individuals obtained from a later life brood had significantly higher rates of survival and higher presence of offspring in comparison to individuals obtained from the early life brood. However, there was not a significant effect of SeMet treatment on resistance to heat induced stress. These results suggest that, at the age rang tested, there is a detectable influence of maternal age on the effect of SeMet for the time to first reproduction and resistance to heat induced stress, but there is not a detectable influence on the total selenium tissue content or lifespan measures in Daphnia pulex.

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