Welcome to the third installment of “Dissertation Diaries.” This week, we will focus on Bradley Pedro, a fifth-year biology doctoral candidate in the Romero Lab at Tufts!
Pedro earned his bachelor’s degree in biology at the University of Massachusetts Amherst and, prior to his research at Tufts, he worked as a laboratory technician in cell biology at Massachusetts General Hospital. During his time as an undergraduate student, Pedro conducted research on migratory birds, so his work at MGH represented a substantial shift. “I got a lot of good technical skills [at MGH], but looking for PhDs, I wanted to kind of go back to working with animals,” he said.
The Romero Lab as a whole studies the vertebrate stress response. The vertebrate stress response is a set of responses that have evolved to help animals survive in predatory environments. When organisms perceive stressors, they shift their focus away from regular activities (i.e. growth and reproduction) toward those that work to increase their survival (i.e. avoiding predators). “[The stress response] is actually a pretty broad and complex thing, and essentially, we want to better understand how animals react or cope with stress,” Pedro said.
For most of their studies done on wild animals, the lab brings creatures into captivity in order to perform experiments on them. Relocating organisms from their natural habitats to a laboratory setting, however, acts as a major stressor.
To counteract this, Pedro’s first project in the Romero Lab involved replicating wild conditions in a laboratory environment to minimize the effects of stress. Using this setup, he studied corticosterone levels in wild house sparrows, a common but invasive bird species. In birds, corticosterone is a steroid hormone that promotes physiological and behavioral responses to stress to increase survival rates, analogous to cortisol in humans. However, he noted that accumulation of these hormones can contribute to DNA damage.
Similar to his first project, Pedro is studying stress in house sparrows. However, his current thesis revolves around connecting the risk response regulators and behavior that helps these species survive. Risk response regulators are signaling molecules and hormones that regulate how organisms respond to stress. In house sparrows, the hypothalamic pituitary adrenal axis is an output system that manages the stress response, which controls release of corticosterone from the adrenal gland. This HPA axis is activated as a response to physical and psychological stressors.
“I really track flights in response to different startles… As a marker of physiology, I track body surface temperature changes,” Pedro said. “So I do a lot of work with thermal cameras to track temperature changes of the beak.”
As stress responses are associated with changes in body temperature, thermal imaging can measure these physiological responses in a non-invasive manner.
An initial stress or fight-or-flight response shifts blood away from peripheral areas and toward core tissues to initiate a reaction. For example, your hands may become pale and cold in response to a stressful situation as blood flows toward your heart, brain and essential muscles.
“But for a bird, that’s the beak, so they kind of shunt blood away from the beak and towards, like, flight muscles and [the] heart, so I actually see decreases in beak temperature during stress,” Pedro explained.
Although transferring some animals to captivity is necessary for conservation purposes, the process is often challenging as chronic stress is a major concern; studying stress responses is necessary to conclude whether some species will or will not adjust to captive conditions. In birds, increasing corticosterone is associated with a lower ability to adjust to short-term captivity.
Although Pedro’s research is centered around house sparrows, there are small connections that can be made to humans as well. In general, animal models are significant in a physiological context for understanding how humans might handle stress or any possible damage that accumulates with stress. “So you can look at, you know, tissue-level damage that occurs from stress and all sorts of stuff that we necessarily wouldn’t look at in humans,” Pedro added.
However, working toward a Ph.D. is a challenging route filled with trial and error. After multiple years as a doctoral candidate, Pedro shared, “Results not being what you predict, that’s just a part of science… You have a hypothesis, you test it, it’s not what you expect. I think that’s still interesting to put out into the world.”
Although there is room for error, research also often takes longer than initially planned. From this, “you really learn how to be flexible and deal with things not going right the first time or the third time” said Pedro.
Despite the lengthy process, Pedro mentioned that he enjoys the ability to have creative freedom for his research. “So with the topic as broad as ‘better understanding the stress response,’ I’ve really gotten to come up with interesting experiments and test interesting hypotheses on my own,” Pedro said, “And that’s been actually a really fun aspect, is being able to be creative under a very broad research umbrella.”
Pedro also shared a piece of advice for undergraduate students interested in pursuing a Ph.D., “Try and get involved in research while you’re here.” Establishing the foundational skills can set you up for success in the research field. “If you start and you don’t like that topic anymore, that’s fine. It’s part of the learning process. … You don’t need to have it all figured out, but at least a general direction is good.” Following Pedro’s advice, embrace the uncertainty as part of the process: What seems like an error today could lead you toward a breakthrough tomorrow.
