The purpose of the Functional Outcomes Core (Core B) is to provide a standardized set of musculoskeletal assay services that will facilitate completion of the broader goals and objections of the Program Project goals and specific aims. The objective of this Program Project application is to understand how AhR activation by Kyn and its metabolites with aging induces muscle and bone loss. Each of the four projects investigates different aspects of these signaling pathways, yet all will employ similar techniques and animal models. The Functional Outcomes Core will provide each investigator with standard assay services in the areas of bone and muscle histology and histomorphometry, imaging, densitometry, biomechanics, and serum biochemistry. Dr. Meghan McGee-Lawrence will be the core director. She is a bone biologist with experience and expertise in the areas of bone histomorphometry, densitometry, and biomechanics with particular emphasis on the use of animal models in musculoskeletal research. She will be responsible for overseeing all administrative issues related to the Core B facilities, as well as supervising the collection, preparation, and distribution of bone specimens. The Core will serve as the major center for data collection related to bone and muscle metabolism, and as such represents a key component linking the individual projects. Moreover, the Core seeks to develop new technologies in support of future research activities related to the objectives of the Program Project grant.