Developmental stress and stress physiology

Research Interests

 

 

We are interested in how an individual’s phenotype, beyond its genetic programming, is shaped by maternal cues, stress hormones, and nutritional and toxicological stressors.

 

Our research has examined how early exposures to stress hormone and toxicants affect health of individuals. The first sign of distress is a rise in plasma glucocorticoids (GCs), including corticosterone and cortisol. This is thought to increase fitness of individuals by facilitating behaviors and physiology to escape from and withstand the stressful situation. However, GCs can be detrimental when chronically elevated, as GCs slow down growth and disrupt neurogenesis. This cost-benefit balance is especially important for altricial species where extensive development takes place outside of the protection of the womb or egg. We conducted a series of experiments to determine how suboptimal incubation temperatures and early exposure to GCs, mercury, or nutritional stress affect stress physiology in several song birds. We found that young hatched from eggs that were incubated at suboptimal temperature transiently increases adrenocortical responses to capture and handling stress. In contrast, early exposure to mercury through nestling diet and maternal deposition of mercury into eggs suppresses adrenocortical responses to handling stress. Food restriction often elevates GCs in birds. When nestlings are food restricted during nestling period did not alter growth rate. In contrast, food restriction during a juvenile period increased somatic growth, body fat, and immune function.

 

We are also interested in the effects of developmental stress on gene expression and epigenetic modification related to stress physiology. 

 

For more details, please click below for related articles on the topic.

 

Kriengwatana B, Wada H, Macmillan A, MacDougall-Shackleton SA (2013). Juvenile nutritional stress affects growth rate, adult organ mass, and innate immune function in zebra finches (Taeniopygia guttata). Physiological and Biochemical Zoology 86 (6): 769-781.

Wada H, Bergeron CM, McNabb FMA, Todd BD, Hopkins WA (2011). Dietary mercury has no observable effects on thyroid-mediated processes and fitness-related traits in wood frogs. Environmental Science & Technology 45: 7915–7922.

Bergeron CM, Bodinof CM, Budischak SA, Wada H, Unrine JM, Hopkins WA (2011). Counterbalancing effects of maternal mercury exposure during different stages of early ontogeny. Environmental Pollution 409: 4746-4752.

Wada H, Cristol DA, McNabb FMA, and Hopkins WA (2009). Suppressed adrenocortical responses and triiodothyronine levels in birds near a mercury-contaminated river. Environmental Science and Technology 43, 6031-6038.


 

 

Developmental stress and neural plasticity

In birds, the egg provides a nutritionally stable environment, but does not fully shield the embryos against temperature variations, maternal hormones, or toxicant deposits. After hatching, nestlings may also face nutritional stress. It has been proposed that birdsong qualities reflect the quality of early-life conditions: a male bird that could not cope with stressors during critical brain developmental stages will sing poorly – and will have poor reproductive success.

 

Consequently, songbirds provide an excellent animal model to study the effects of early life adversity on brain development because of 1) the role of hormones in the neuronal turnover in the song control regions of the brain and 2) the well-described, specialized relationship between song (a measurable, learned behavior) and brain anatomy. Lines of evidence showed that dietary restriction, corticosterone, as well as diseases all lead to lower quality songs and reduced size of the song nuclei in the brain.

In my laboratory we investigate the mechanisms underlying the effects of early life stressors on song nuclei.

 

For more details, please click below for related articles on the topic.

 

Wada H, Newman AEM, Hall ZJ, Soma KK, MacDougall-Shackleton SA (2014). Effects of corticosterone and DHEA on doublecortin immunoreactivity in the song control system and hippocampus of adult song sparrows. Developmental Neurobiology 74(1): 52–62.

Wada H and Breuner CW (2010). Developmental changes in neural corticosteroid receptor capacity in altricial nestlings. Journal of Developmental Neurobiology 70, 853-861.

Assistant Professor

Department of Biological Sciences

Auburn University

 

 

Contact info

 

Office: 314 Rouse LSB

Lab: 005, 004 & 002 Rouse LSB

 

Office Telephone : ​+1 334-844-1338

Lab Telephone: +1 334-844-1685

Fax : +1 334-844-1645
Email : haruka@auburn.edu

Mailing address
 
Department of Biological Sciences

101 Rouse Life Science Building

Auburn AL, 36849