preliminary validation of a short‐term morphological assay to evaluate adverse effects on amphibian metamorphosis and thyroid function using xenopus laevis

Fort, Douglas J.; Rogers, Robert L.; Morgan, Lisa A.; Miller, Mark F.; Clark, Patrick A.; White, Jonathan; Paul, Robbin R.; Stover, Enos L.

doi:10.1002/1099-1263(200009/10)20:5<419::aid-jat708>3.3.co;2-1

Cited by 20 publications

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“…The herbicide acetochlor, for which amphibian TRs and TTRs had no significant affinity (Yamauchi et al 2002, Ishihara et al 2003a, altered TH-dependent gene expression and amphibian metamorphosis (Cheek et al 1999, Veldhoen & Helbing 2001, Crump et al 2002. Xenopus tadpoles previously exposed to methoprene did not respond to exogenously added T 4 (Fort et al 2000), although Xenopus TR and TTR showed no significant affinity for this chemical (Yamauchi et al 2002). However, there have been few reports that focus on processes other than competitive binding of EDCs to TTR and TR in the thyroid system.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of 3,5,3′-triiodothyronine (T3)-uptake system of tadpole red blood cells: effect of endocrine-disrupting chemicals on cellular T3 response

Shimada¹,

Yamauchi²

2004

Journal of Endocrinology

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We characterized the 3,5,3 --triiodothyronine (T 3 )-uptake system on the plasma membrane of Rana catesbeiana tadpole red blood cells (RBCs) 125 I]T 3 uptake by 2-fold at 3·2 µM. When RBCs were cultured with 10 nM T 3 at 25 C for 2 days in the presence of monodansylcadaverine, ethinylestradiol, ioxynil or dicofol at the defined concentrations, these compounds inhibited significantly the induction of the thyroid hormone receptor gene by T 3 . However, not all chemicals competed with T 3 binding to the receptor at the same concentrations. Our results raise the possibility that the T 3 -uptake system on the plasma membrane of the tadpole RBCs could be a candidate target site for some EDCs and can modulate cellular T 3 response.

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Section: Introductionmentioning

confidence: 99%

Characteristics of 3,5,3′-triiodothyronine (T3)-uptake system of tadpole red blood cells: effect of endocrine-disrupting chemicals on cellular T3 response

Shimada¹,

Yamauchi²

2004

Journal of Endocrinology

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“…In terms of culture, different approaches may be considered. For example, the specific process of tail resorption can be monitored by culturing tadpoles at relatively low densities such as in multiple replicates for 16 to 18 d from stage 58 to 66 during which time the rate of tail resorption is measured (Fort et al, 2000). Low densities of ca.…”

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confidence: 99%

“…First, the rate of tail resorption is naturally variable in whole organism culture (Fort et al, 2000;Fort et al, 2001b), which reduces the sensitivity and predictability of this endpoint. Second, this process occurs in the later stage of metamorphosis, when the thyroid is fully active and at its peak early in the climatic period.…”

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confidence: 99%

“…For example, tadpoles exposed to the goitrogen methimizole develop enlarged thyroid glands that are visible under low magnification in the transparent Xenopus tadpole (Fort et al, 2000). In this case, the thyroid gland can be digitally photographed and the size quantified by photodigitization.…”

mentioning

confidence: 99%

“…As originally proposed by Fort et al (2000), this assay primarily quantitatively evaluated the rate of tail resorption in X. laevis, although maturation of the skin and forelimb development were noted anecdotally. Due to higher than acceptable levels of variability in the rate of tail resorption, the assay has been modified somewhat to increase robustness.…”

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Detailed Review Paper on Amphibian Metamorphosis Assay for the Detection of Thyroid Active Substances

2004

OECD Series on Testing and Assessment

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Preexposure to ultraviolet B radiation and 4‐tert‐octylphenol affects the response of Rana pipiens tadpoles to 3,5,3′‐triiodothyronine

Croteau

Duarte‐Guterman

Lean

et al. 2010

Enviro Toxic and Chemistry

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Exposure to multiple environmental stressors is negatively impacting the health of amphibians worldwide. Increased exposure to ultraviolet B radiation (UVBR) and chemical pollutants may affect amphibian populations by disrupting metamorphosis; however, the actual mechanisms by which these stressors affect development remain unknown. Because amphibian metamorphosis is controlled by thyroid hormones (TH), changes in developmental rates by environmental stress suggest a disruption of the thyroid system. Tadpoles were chronically exposed to environmental levels of UVBR (average of 0.15 W/m2) and 4-tert-octylphenol (OP; 10 nM), alone and combined, prior to being challenged to exogenous TH triiodothyronine (T3; 5 or 50 nM). This experimental approach was taken to determine whether exposure to these stressors affects the ability of T3 to elicit specific molecular and morphological responses. Exposure to OP increased mRNA levels of thyroid receptors (TRs) alpha and beta, deiodinase type 2 (D2), and corticotropin releasing hormone in the brain and of D2 in the tail of tadpoles. 4-tert-octylphenol also enhanced T3-induced expression of D2 in the brain. The combination of UVBR and OP affected the expression of TR alpha in the brain and the responses of TR alpha and beta genes to T3 in the tail, demonstrating the importance of considering the effects of multiple stressors on amphibians. Tadpoles exposed to UVBR were developmentally delayed and exhibited slowed tail resorption and accelerated hindlimb development following exposure to T3. Together, these findings indicate that UVBR alters the rate of development and TH-dependent morphological changes at metamorphosis, and that exposure to UVBR and/or OP disrupts the expression of genes important for development and the biological action of T3 in peripheral tissues. Our group is the first to demonstrate that environmental levels of UVBR and/or OP can affect the thyroid system of amphibians.

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preliminary validation of a short‐term morphological assay to evaluate adverse effects on amphibian metamorphosis and thyroid function using xenopus laevis

Cited by 20 publications

References 0 publications

Characteristics of 3,5,3′-triiodothyronine (T3)-uptake system of tadpole red blood cells: effect of endocrine-disrupting chemicals on cellular T3 response

Characteristics of 3,5,3′-triiodothyronine (T3)-uptake system of tadpole red blood cells: effect of endocrine-disrupting chemicals on cellular T3 response

Detailed Review Paper on Amphibian Metamorphosis Assay for the Detection of Thyroid Active Substances

Preexposure to ultraviolet B radiation and 4‐tert‐octylphenol affects the response of Rana pipiens tadpoles to 3,5,3′‐triiodothyronine

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