Dr. Tyrone Hayes

The Teratogenic Effects of Atrazine.

-Review articles for Endocrine Disruptions by Hayes et al

– Hayes TB. Welcome to the revolution: integrative biology and assessing the impact of endocrine disruptors on environmental and public health. Integr Comp Biol. 2005 Apr;45(2):321-9

-Main research articles on Atrazine by Hayes et. al. (Main presentation article):

-Hayes TB, Khoury V, Narayan A, Nazir M, Park A, Brown T, Adame L, Chan E, Buchholz D, Stueve T, Gallipeau S. Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis). Proc Natl Acad Sci U S A. 2010 Mar 9;107(10):4612-7.

-Past Research articles to support main paper (please look at and potentially use for question generation):

-Hayes TB, Stuart AA, Mendoza M, Collins A, Noriega N, Vonk A, Johnston G, Liu R, Kpodzo D. Characterization of atrazine-induced gonadal malformations in African clawed frogs (Xenopus laevis) and comparisons with effects of an androgen antagonist (cyproterone acetate) and exogenous estrogen (17beta-estradiol):

Support for the demasculinization/feminization hypothesis. Environ Health Perspect. 2006 Apr;114 Suppl1:134-41.

-Hayes TB, Case P, Chui S, Chung D, Haeffele C, Haston K, Lee M, Mai VP, Marjuoa Y, Parker J, Tsui M. Pesticide mixtures, endocrine disruption, and amphibian declines: are we underestimating the impact? Environ Health Perspect. 2006 Apr;114 Suppl 1:40-50.

-Hayes T, Haston K, Tsui M, Hoang A, Haeffele C, Vonk A. Herbicides: feminization of male frogs in the wild. Nature. 2002 Oct 31;419(6910):895-6.

Question 1: About Dr. Tyrone Hayes

Briefly tell us a bit about yourself, your career path over the years, and specifically what brought you to begin working on the developmental mechanisms behind evolutionary adaptations?

Michael Barresi

Question 2: Mechanisms Of Atrazine Action

In your 2006 paper on pesticide mixtures, you mention many studies that used pesticide concentrations 10,000x the low concentration used in your studies. Your low dosages are relevant, as they are what occur in the environment and actually can be useful in looking at pesticide impact on wildlife. Why did these others studies use such high concentrations? Obviously a very potent dose of chemical will affect development in some way but those results won’t actually help understand what is going on in the environment.

Sarah Gaffney

Question 5: 

What do you think causes the deviation between SSP and hermaphrodism in male frogs treated with thesame dose of atrazine? Why do some develop ovarian tissue while others produce only testes even though there are many?

Claire Maesner

Question 7: 

(2010 PNAS): Have you or any of your colleagues conducted studies on the transgenerational effects of atrazine? If not, would this type of study hold any value in the work that is currently being done?

Kristine Trotta