Prion diseases are neurodegenerative, attacking the brain. Could they be responsible for the recent wave of Zombie attacks across the globe? Original photo: digitalsextant.

But what if there existed a substance that acted like a virus or bacteria but wasn’t living? Medicine made a revolutionary leap during the time of Louis Pasteur in the mid 1800's. The inventor of food pasteurization and one of the founding fathers of microbiology – he was able to prove germ theory. Food spoiled and organisms got sick because of the growth of bacteria and viruses within them. Within sterile environments, viruses and bacteria could be killed off and food could be preserved or organisms could recover from illness or infection. Sterilization works on living micro-organisms. Prions, however, are not living organisms.

Prions are infectious proteins. For unknown reasons, these proteins refold abnormally and cause a domino effect in surrounding proteins which in turn mutate into stable structures. Prions will then cause tissue damage and cell death to surrounding areas. Prion diseases are neurodegenerative, attacking the brain and are characterized by "holes" in the tissue. The incubation time for Prion diseases is quite long. They usually surface later in life but after they surface, the diseases are rapid and fatal. Such examples of Prion diseases include Mad Cow Disease in cattle, Scrapie in sheep and Fatal Familial Insomnia in humans. FFI is a disease that literally takes away the ability to sleep and in a few months leads to death. The Book “The Family That Couldn’t Sleep” by journalist D.T. Max follows a family in Italy that passes this disease from one generation to the next over subsequent centuries.

Prions have been and still are a medical mystery. What causes them to mutate and aggressively eat away at the brain? How can they be stopped? Because they are not living they are highly resistant to sterilization methods. While viruses and bacteria can be eradicated on equipment through heat, radiation or chemical reagents, Prions are strongly immune. Maybe Zombies are not so far off after all – lurking in the shadow of medicine has been a mutation that is resistant, brain-eating and neither alive or dead. It has some serious similarities to the zombies I have watched over and over again on the big screen.

If you want to learn more about Prions and their history, check out Down to a Science’s next reading group which is focusing on the book The Family that Couldn’t Sleep or check out the book Deadly Feasts: The "Prion" Controversy and the Public's Health by Richard Rhodes. And one more thing – Happy Halloween!

So we visited zookeeper Andrea Dougall at the Oakland Zoo to learn about their Malayan and Island Flying Fox. Both are a type of fruit bat, and I couldn’t readily see the difference between them. There are many fascinating things that Andrea taught us about these bats that we couldn't fit into our two minute segment (and honestly, this producer wouldn't mind making a half hour special on these critters!). For instance, they have a lot of blood vessels in their wing tissue, so they make excellent thermo-regulators. If the bat is cold, he wraps himself up in his wings so that the heat from his blood vessels can keep him warm. Likewise, when it's hot out the bats flap their wings to cool off.

When Andrea told us that bats are the only mammals that can have sustained flight by flapping their wings, someone said "but what about the flying squirrel?" Nope– they glide.

These bats don't actually swallow the fruit that they eat, instead they chew it into small pieces, push it up against the roof of their mouth to ring out the juice, which they then swallow, and spit out the leftovers. This is something that Andrea reminded me of when I told her I'd like to take one of these cute critters home as a pet… the amount of rotten fruit pulp that you have to pick up is really unappealing. Plus, of course, it would be illegal.

Perhaps the most intriguing thing to me is the simple fact that these animals spend all of their time hanging upside down. I asked Andrea about that too– how is it possible that they wouldn't experience some sort of leg fatigue and let go of their grip? She told me what's in the scientific literature on other kinds of bats (and we're assuming it applies to fruit bats as well). The deal is that the tendon of the muscle that flexes the claw passes through a tough sheath that consists of 19-50 rings, oriented at an angle so that the inside surface is ridged. So there's some ratchet-action going on in the sheath that holds the claw in a grasping position even after the muscle has relaxed, and it's the tension on that tendon from the body weight that holds the ratchet in place. When the bat wants to move, the tension is released and therefore the claw releases its hold. So basically, the clenched position is the "at rest" position, and the releasing of the foot is the part that takes energy.

If you haven't yet, I highly suggest you make a trip over to the Oakland Zoo to see these highly captivating animals for yourself.

Watch the Cool Critters: Fruit Bats television story report online. Also, if you’d like to see close-up photos of these bats, please visit our photo set over on Flickr.