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Approaches for assessing the presence and impact of thyroid hormone disrupting chemicals in Delphinid cetaceans

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dc.contributor.advisor Mark E. Hahn. en_US Montie, Eric Wilson en_US
dc.contributor.other Woods Hole Oceanographic Institution. en_US 2007-10-19T21:05:49Z 2007-10-19T21:05:49Z 2006 en_US 2006 en_US
dc.description Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2006. en_US
dc.description This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. en_US
dc.description Includes bibliographical references. en_US
dc.description.abstract Cetacean blubber is a primary site for lipid storage, which the animal utilizes during periods of energetic stress. It is important to understand how the blubber responds to factors such as ontogeny, water temperature, reproductive status, and nutritional state because blubber is also the primary bioaccumulation site for persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs). During periods of lipid mobilization such as lactation, PCBs from the blubber are mobilized into the circulatory system and may cause toxic effects. One particular toxic mechanism may include the induction of cytochrome P450 enzymes in the integument and liver, which could enhance the biotransformation of PCBs to hydroxylated metabolites (OH-PCBs). OH-PCBs may then interfere with thyroid hormone dependent neurodevelopment. The goals of these studies were to investigate the relationships between lipid dynamics and PCB effects and to devise a quantitative approach to assess neurodevelopment in delphinid cetaceans. Blubber morphology, cytochrome P450 1A1 (CYP1A1) expression in the skin-blubber biopsy, blubber and plasma PCBs, and plasma OH-PCBs were assessed in bottlenose dolphins (Tursiops truncatus). en_US
dc.description.abstract (cont.) In addition, magnetic resonance (MR) images of the post-mortem brain in situ were obtained from Atlantic white-sided dolphin (Lagenorhynchus acutus) specimens. These results showed that: 1) Factors such as ontogeny, water temperature, and reproductive status affected blubber morphology in bottlenose dolphins. In response to warmer water, the lipid content of the blubber decreased and this appeared to involve loss of lipids from adipocytes in the middle blubber layer. Similar to the effects of starvation on blubber morphology, lactation decreased adipocyte size predominantly in the deeper blubber, 2) CYP1A1 levels in the deep blubber were significantly related to the total plasma TEQ98 concentrations, adipocyte shrinkage, and plasma OH-PCB levels, 3) Through in situ MR imaging of stranded, Atlantic white-sided dolphin specimens, the size of brain structures that depend on thyroid hormones for maturation could be measured accurately. Future studies can use this technique, coupled with chemical analysis of brain regions, to determine if thyroid hormone disrupting chemicals in delphinid cetaceans are associated with changes in the size of brain structures. en_US
dc.description.statementofresponsibility by Eric Wilson Montie. en_US
dc.format.extent 303 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.subject /Woods Hole Oceanographic Institution. Joint Program in Oceanography/Applied Ocean Science and Engineering. en_US
dc.subject Biology. en_US
dc.subject Woods Hole Oceanographic Institution. en_US
dc.subject.lcsh Delphinidae en_US
dc.title Approaches for assessing the presence and impact of thyroid hormone disrupting chemicals in Delphinid cetaceans en_US
dc.type Thesis en_US Ph.D. en_US
dc.contributor.department Joint Program in Oceanography/Applied Ocean Science and Engineering. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Biology. en_US
dc.contributor.department Woods Hole Oceanographic Institution. en_US
dc.identifier.oclc 85870722 en_US

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