Animals experience stress in many forms, prompted by a lion ifyou are a deer, El Ni�o if you are an iguana -- and exams ifyou are a student. What helps all animals to manage stress and inturn gain balance is the stress hormone cortisone.
Associate Biology Professor Michael Romero has been studyingstress for several years, and thanks in part to him, physiologistshave changed the way they see stress. According to the establisheddogma, cortisone acts to increase glucose levels in the blood. Butthat notion has been overthrown by Romero's research.
The original understanding of cortisone's role came from studiesdone on fasted animals in the 1960s. In contrast, Romero's studieswere done on fed animals.
His results, which were presented at the International Symposiumon Avian Endocrinology in June 2004 in Scottsdale, Ariz., showedthat cortisone does not act to increase blood glucose levels,prompting a reevaluation of our understanding of cortisone.
Why study stress? "The hormonal levels can indicate the healthof an animal and by extension the overall health of a population,"Romero said. From humans to birds to iguanas, animals manageexcessive stress by releasing cortisone.
For example, students coping with a stressful stimulus like anexam release cortisone to both recover from that stressor, and toprepare for upcoming stressors, like a job interview.
Thus, the amount of cortisone in the body of an animal indicateshow much stress it is under. Accordingly, cortisone levels inmarine iguanas in the Galapagos Islands were used to assess thehealth of the population after an oil spill in the area. (The studywas published in a 2001 issue of Science Magazine.)
The study was an unconventional overlap between ecology andphysiology. In the past, conservation biology focused on two areasto predict the health of a population: looking at the actualnumbers of the population, and looking at the population'sbehavior.
"The problem with looking at numbers is that by the time yourealize that the numbers have gone down, it might be too late to doanything," Romero said. "So we took the middle path and saw thephysiology of the animals to predict any impacts on thepopulation."
Romero had a special reason for choosing to study the stressphysiology of wild animals. "It is difficult to study stress inhumans because the three main causes of stress -- namely famine,predator attacks and inclement weather --was never faced by amodern western human," Romero said. "So the best way to understandthe role of cortisone in managing stress will be to study wildanimals that face the above stressors."
Romero's studies have the potential to provide new insights intothe fundamentals of vertebrate biology. Romero sees his work assomething that will improve our basic understanding of the biologyof stress.
Romero also hopes his research will influence the biomedicalcommunity. "We have no idea why cortisone is released in the firstplace," he said. "The study is mainly foundation work. You cannotfix a problem unless you know that something is broken."
The idea of studying stress in wild animals occurred to Romerowhile he was studying for his doctorate at Stanford.
Most of the experiments done on laboratory rats were done duringthe day; because rats are nocturnal animals, experiments done onthem during the day did not accurately simulate the natural stressresponse of the rats.
Romero wanted instead to do experiments on the rats during thenight. However, rats' viability as experimental animals hasdecreased because they are not naturally selected.
"Laboratory rats have undergone generations of artificialselection, in contrast to the starlings which are caught from thewild," Romero said. Instead, he began working with starlings.
"[Starlings] may better represent the physiological responses tostress exhibited by naturally selected populations such as humans,"biology graduate student Nicole Cyr said.
Based on his work with the starlings, Romero found that thehormones released during stress have varying effects over the24-hour period of day and night. "If it is daytime, the stressresponse of animals will be to flee," Romero said. "The nighttimeresponse will be completely different, like to freeze."
The results of Romero's study were published in the AmericanJournal of Physiology in 2001.
Since the physiology of stress in birds is similar to that ofmammals, the study has given considerable insight into human stressphysiology as well. But Romero acknowledges that we have a ways togo.
"In conditions when we are continuously stressed, the cortisonelevels can be so high so as to inhibit different parts ofphysiology -- maybe even shutting down the immune system," Romerosaid. "In terms of the current knowledge of stress, it is toodifficult to understand any stress related event likestress-induced eating."
Only more research, Romero said, will give us a betterunderstanding of the stress physiology.
