Humans and all other mammals get our clotting power from cells called platelets, said Mark Kahn, the study's senior author. These small, flat cells are crucial for our survival because our blood circulates at constant high pressure - more so than in fish, lizards, and other cold-blooded creatures. That means human blood does not just leak from cuts, but spurts.
Most platelets made in human blood live and die without doing anything, but when damage occurs, exposed proteins call collagen prompt a cascade of reactions that makes them sticky and clumpy.
That's good if you just cut yourself slicing a bagel. But it's bad if there's a rupture of artery plaque, which can lead to a deadly blockage.
Birds also have high blood pressure and need a clotting system, but they use much larger cells with a nucleus called thrombocytes. Do these pose the same cardiovascular danger as platelets?
No one had collected data on the instance of bird heart disease, so the researchers did experiments comparing chicken and human blood.
The easy part was getting the human blood. For chicken blood, the team sent colleague Alec Schmaier to a South Philadelphia market that sold live chickens. Schmaier went dozens of times, each time buying a chicken, drawing blood from the wing, and then having the chicken killed and butchered so it could become dinner for someone in the group.
Comparing the two types of clotting cells, they found both capable of manufacturing a similar set of proteins, except that birds made little to none of two proteins that are important for sticking platelets to one another.
