Science Update - Giraffes, Vaccines and Salmon

Chelsea - Sure! This one is an audio question:

Matthew - Why is it that giraffes don't have a stroke when they bend down to get a drink of water?

Chelsea - Excellent question, Matthew. Why don't giraffes have strokes when bending over? Well, we talked to giraffe circulation expert Alan Hargens of the University of California - San Diego. He explained that their brains and spinal cords are surrounded by fluid, just like ours. When they bend over, that fluid rushes to their heads, and squeezes the swelling blood vessels from the outside.

Alan - So when they bend head-down to, say, for example, drink water, the elevation of blood pressure due to the head-down tilt could be counteracted, one for one, by the increase in cerebro-spinal fluid pressure. WALD: Even so, he says giraffes generally don't keep their heads down for long, even when they're sleeping.

Bob - Fascinating. Thanks, Chelsea. Here's another. After hearing about threatened salmon populations, Merrie Smith from Mendocino, California, called to ask why we catch and eat salmon before they've spawned, rather than after. We asked University of Alberta salmon expert Martin Krkosek. He says that when salmon reach their spawning streams, they stop eating and metabolize their own flesh for fuel. On top of that, competing for mates and digging nests for eggs takes its toll.

Martin - So by the time they're actually spawning, and after they spawn, their bodies are really worn out, from fighting with each other, from digging, and they're also usually heavily infected with fungus; they're generally just really gross.

Bob - Very ecological-but not very palatable. Thanks, Merrie. One last one, Chelsea?

Chelsea - OK. Listener Luci Levesque from Augusta, Maine, heard that vaccines are made in fermenters, devices normally associated with beer. She asks, what's the connection? Good question! We turned to microbiologist Agnes Day of Howard University College of Medicine.

Agnes - The principle of using a fermenter is the same for beer as it is for vaccine production.

Chelsea - She tells us that a fermenter is simply a device that grows microorganisms on a large scale. In beer, those microorganisms are the yeast that convert sugars into alcohol. But in vaccine production, they are disabled versions of the disease-causing bacteria or viruses that will ultimately form the basis of the vaccines.

Bob - Thanks, Chelsea. We hope you naked people and all your fans stay warm and have a very happy holiday. Until next time, I'm Bob Hirshon…

Chelsea - And I'm Chelsea Wald, for AAAS, The Science Society.