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Regulation of elements of the thyroi...

The University of Texas at Austin., Marine Science.

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Regulation of elements of the thyroid hormone and corticosteroid systems by stress, hormone treatment, and atrazine during ontogeny of red drum (Sciaenops ocellatus).

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Regulation of elements of the thyroid hormone and corticosteroid systems by stress, hormone treatment, and atrazine during ontogeny of red drum (Sciaenops ocellatus)./
Author:	Applebaum, Scott Lee.
Description:	129 p.
Notes:	Adviser: B. Scott Nunez.
Contained By:	Dissertation Abstracts International69-08B.
Subject:	Agriculture, Fisheries and Aquaculture. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3326617
ISBN:	9780549774310

Regulation of elements of the thyroid hormone and corticosteroid systems by stress, hormone treatment, and atrazine during ontogeny of red drum (Sciaenops ocellatus).
Applebaum, Scott Lee.

Regulation of elements of the thyroid hormone and corticosteroid systems by stress, hormone treatment, and atrazine during ontogeny of red drum (Sciaenops ocellatus). - 129 p.

Adviser: B. Scott Nunez.

Thesis (Ph.D.)--The University of Texas at Austin, 2008.

Survival of teleost larvae requires growth and development which depend upon endocrine processes. In this dissertation I have examined the ontogeny of elements of the thyroid hormone (TH) and corticosteroid (CS) systems in red drum (Sciaenops ocellatus). Basal cortisol production was first detected 3 days post-hatch (DPH) and a cortisol stress response was present from 6 DPH forward. Changes in steroidogenic enzyme mRNA (CYP11B and CYP21) levels did not correlate with these events. The time necessary to reach peak cortisol levels as well as return to basal levels declined as larvae developed. A second set of studies examined ontogenetic patterns in levels of mRNAs encoding thyroid (soTRalpha and soTRbeta) and corticosteroid (soGR) hormone receptors and assessed the regulation of these mRNAs by exogenous triiodothyronine (T3) and cortisol. soTRalpha, soTRbeta and soGR were expressed in all stages of red drum examined. soTRalpha levels increased during the time when surging TH levels have been reported. soTRbeta levels did not differ significantly during development. soGR levels were strongly correlated with those ofsoTRalpha. T3 up-regulated soTRalpha and soTRbeta levels in 7 DPH, but not older larvae. Cross-regulation of receptor mRNAs by exogenous treatment with T3 or cortisol was not observed. Finally, I assessed the influence of a common herbicide, atrazine, on receptor mRNA, TH levels and growth of red drum. In two experiments, red drum exposed to environmentally relevant levels of atrazine did not alter hormone receptor mRNA levels, or TH content. However, atrazine did depress growth in some instances. In conclusion, the expression patterns of hormone receptor mRNA in embryos suggests receptor proteins could be activated by maternal hormones prior to the onset of endogenous hormone production. A correlation between soTRalpha and soGR mRNA levels suggests coordinated function of TH and CS systems, although regulatory interactions between these systems were not evident under the conditions in this study. Patterns in soTRalpha and soTRbeta mRNA levels support an important role for TH in the larval to juvenile transformation of red drum larvae. The results also support growing evidence indicating atrazine exposure effects larval growth and may impact their survival in the wild.

ISBN: 9780549774310Subjects--Topical Terms:

1020913
Agriculture, Fisheries and Aquaculture.

Regulation of elements of the thyroid hormone and corticosteroid systems by stress, hormone treatment, and atrazine during ontogeny of red drum (Sciaenops ocellatus).
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245 1 0 $a Regulation of elements of the thyroid hormone and corticosteroid systems by stress, hormone treatment, and atrazine during ontogeny of red drum (Sciaenops ocellatus).
300 $a 129 p.
500 $a Adviser: B. Scott Nunez.
500 $a Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4503.
502 $a Thesis (Ph.D.)--The University of Texas at Austin, 2008.
520 $a Survival of teleost larvae requires growth and development which depend upon endocrine processes. In this dissertation I have examined the ontogeny of elements of the thyroid hormone (TH) and corticosteroid (CS) systems in red drum (Sciaenops ocellatus). Basal cortisol production was first detected 3 days post-hatch (DPH) and a cortisol stress response was present from 6 DPH forward. Changes in steroidogenic enzyme mRNA (CYP11B and CYP21) levels did not correlate with these events. The time necessary to reach peak cortisol levels as well as return to basal levels declined as larvae developed. A second set of studies examined ontogenetic patterns in levels of mRNAs encoding thyroid (soTRalpha and soTRbeta) and corticosteroid (soGR) hormone receptors and assessed the regulation of these mRNAs by exogenous triiodothyronine (T3) and cortisol. soTRalpha, soTRbeta and soGR were expressed in all stages of red drum examined. soTRalpha levels increased during the time when surging TH levels have been reported. soTRbeta levels did not differ significantly during development. soGR levels were strongly correlated with those ofsoTRalpha. T3 up-regulated soTRalpha and soTRbeta levels in 7 DPH, but not older larvae. Cross-regulation of receptor mRNAs by exogenous treatment with T3 or cortisol was not observed. Finally, I assessed the influence of a common herbicide, atrazine, on receptor mRNA, TH levels and growth of red drum. In two experiments, red drum exposed to environmentally relevant levels of atrazine did not alter hormone receptor mRNA levels, or TH content. However, atrazine did depress growth in some instances. In conclusion, the expression patterns of hormone receptor mRNA in embryos suggests receptor proteins could be activated by maternal hormones prior to the onset of endogenous hormone production. A correlation between soTRalpha and soGR mRNA levels suggests coordinated function of TH and CS systems, although regulatory interactions between these systems were not evident under the conditions in this study. Patterns in soTRalpha and soTRbeta mRNA levels support an important role for TH in the larval to juvenile transformation of red drum larvae. The results also support growing evidence indicating atrazine exposure effects larval growth and may impact their survival in the wild.
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