Stress and Reproduction

The research project I am working on in the Alberts Lab examines how drought, and the stress caused by drought, can affect pregnancy and conception in wild baboons. We are specifically studying the wild baboon population in Amboseli National Park in Kenya. Like humans, baboons are fertile and mate year-round, rather than having a breeding season. This, then, begs the question: Why do female baboons not become pregnant each cycle? One potential reason could be stress-level, caused by environmental factors such as drought.

In the lab, I am using radioimmunoassays to detect the level of glucocorticoid, a stress hormone, in fecal samples collected from the baboon population in Amboseli. Radioimmunoassay, developed by Rosalyn Yallow, uses competitive binding between antibodies and antigens to determine the concentration of antigens (in this case, glucocorticoid). A set amount of radioactively-tagged glucocorticoid is mixed with an antibody and the two bind. Then,  a small amount of the fecal sample, which has been purified and concentrated into a liquid which contains the glucocorticoid, is added to the mixture. The radioactively tagged glucorticoid and the non-radioactive glucocorticoid from the sample compete to bind to the antibody. The antigens that have not bound to the antibody precipitate out of the solution, and the supernatant is removed. Then, the amount of radioactivity in the precipitate is counted by a gamma counter. The more radioactive the precipitate is, the less glucocorticoid hormone from the sample is present, meaning that this sample had less glucocorticoid originally. From this, we can extrapolate how much of the stress hormone was in the sample. Fecal samples collected in Amboseli are labeled with the name of the individual and the time and date of the sample. Using this information, data collected in the field about the reproductive cycle phase of the female baboon, and the glucocorticoid levels determined in the lab, we can look at the relationship between stress and reproduction.

Wild Baboons in Amboseli National Park (Source: http://amboselibaboons.nd.edu/publications/)

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