Over the past 40 years, Meyer says techniques have become not only much more sensitive and precise, but safer for researchers as they have been able to move away from using radioactive substances. "We can now measure much lower levels of substances than we could when I was a grad student," he recalls. "And with new enzyme immunoassay techniques read by a microplate reader, the work has become not only safer for researchers, but for lab workers and the environment."
To analyze cortisol levels in hair, the researchers need a sample about 3 cm long and weighing about 5 mg, that is, 10 or 12 strands. In humans, this amount cut from the scalp outward represents about three months of hormone activity as human hair grows an average 3 cm per month, Meyer notes. In his UMass Amherst lab about six undergraduates are currently learning the exacting techniques for washing and drying samples, grinding them to powder, extracting the cortisol, and conducting the enzyme immunoassay.
For the collaboration with Bechshft and colleagues, Meyer's lab received blind hair samples from 88 polar bears legally killed between 1988 and 2009 in Greenland by indigenous people who have an arrangement with researchers to provide biological samples. Cortisol will persist in hair for hundreds of years, Meyer explains.
"We have analyzed this hormone in several blind samples of polar bear hair from museum specimens that were killed and stuffed in the late 1800s, and we had no trouble measuring it 125 years later," he says. "Others have measured cortisol concentrations in Peruvian mummies 1,500 years old. It's one of the beauties of hair cortisol, you can measure it in archival specimens."
|Contact: Janet Lathrop|
University of Massachusetts at Amherst