JOSEPH M. CASTO

Adjunct Assistant Professor of Neurobiology, Illinois State University
Assistant Director, Research Ethics & Compliance

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Field Endocrinology and Ecological Immunology

Some of the lab's research focuses on the interaction between steroid hormones and fitness in free-living and captive birds. Much of this research is conducted via collaborations with investigators at other universities.

Individual variation in hormone responsiveness. While it is well known that a bird, when in different physiological conditions, exhibits very different endocrine profiles (within-individual variation), it has been incredibly difficult to determine whether wild birds exhibit consistent between-individual variation in steroidogenic capacity or in unperturbed levels of circulating steroids. This is due to variability in techniques used to measure steroids and to the unavoidable consequences that capture and handling have on circulating levels of steroid hormones. In an attempt to overcome some of these obstacles, we have begun to investigate between-individual variation in steroidogenesis in response to a challenge injection of gonadotropin releasing hormone (GnRH). Birds show greater than two-fold elevations in circulating testosterone in response to the challenge. The testosterone response peaks at approximately 30 min and returns to baseline by 2 hours. Given the ease with which this technique translates to the field it holds great promise for investigating individual differences in steroid responsiveness. (Collaborator: Ellen Ketterson, Jodie Jawor & Joel McGlothlin).

The influence of dominance relationships on immune function in European starlings. Immune function of birds is influenced by a variety of factors including levels of circulating hormones such as sex steroids and glucocorticoids. Dominance relationships in birds also covary with circulating levels of these hormones. In this research project we are investigating whether dominance behavior is associated with variation in immune function as assessed by various measures of avian immunity. (Collaborator: Greg Demas)

JOSEPH M. CASTO
Adjunct Assistant Professor of Neurobiology, Illinois State University Assistant Director, Research Ethics & Compliance

	University Links Biology Homepage CAS Homepage ISU Homepage RSP Homepage Research Compliance Quick Links Casto's Homepage POENB Publications Research Students CINF	Field Endocrinology and Ecological Immunology Some of the lab's research focuses on the interaction between steroid hormones and fitness in free-living and captive birds. Much of this research is conducted via collaborations with investigators at other universities. Individual variation in hormone responsiveness. While it is well known that a bird, when in different physiological conditions, exhibits very different endocrine profiles (within-individual variation), it has been incredibly difficult to determine whether wild birds exhibit consistent between-individual variation in steroidogenic capacity or in unperturbed levels of circulating steroids. This is due to variability in techniques used to measure steroids and to the unavoidable consequences that capture and handling have on circulating levels of steroid hormones. In an attempt to overcome some of these obstacles, we have begun to investigate between-individual variation in steroidogenesis in response to a challenge injection of gonadotropin releasing hormone (GnRH). Birds show greater than two-fold elevations in circulating testosterone in response to the challenge. The testosterone response peaks at approximately 30 min and returns to baseline by 2 hours. Given the ease with which this technique translates to the field it holds great promise for investigating individual differences in steroid responsiveness. (Collaborator: Ellen Ketterson, Jodie Jawor & Joel McGlothlin). The influence of dominance relationships on immune function in European starlings. Immune function of birds is influenced by a variety of factors including levels of circulating hormones such as sex steroids and glucocorticoids. Dominance relationships in birds also covary with circulating levels of these hormones. In this research project we are investigating whether dominance behavior is associated with variation in immune function as assessed by various measures of avian immunity. (Collaborator: Greg Demas)