05 April 2013

Porcupine Quills

Welcome back. Do you remember my blog post on how dental visits have changed since we of the older persuasion were strapped into the dental chair and tortured unmercifully as youths? (see Dental Check-Up Time) It was there that I exposed the hypodermic needles used in those years: non-disposable, blunt and barbed.

I always thought the barbs on those needles were to heighten the pain and avert a last second escape: Not so; at least the part about pain. The barbs probably made the needles go in easier. That’s what Harvard Medical School researchers found with porcupine quills.
 

Porcupines
North American porcupine,
National Park Kejimkujik,
Nova Scotia, Canada.
(photo by Jeroen Moss,
www.wildlifeweb.nl)

Not only was I in dread of our family dentist in my youth, I also feared encountering a porcupine. I believed what cartoons and other kids told me about a porcupine’s ability to shoot quills if I got too close. Porcupine poppycock!

Just as I learned that dentists are our friends and need no longer be feared, I also learned that these rodents can only release their quills on contact with you or with that poor, brave, barking dog that will learn to keep its distance. Porcupines also lose quills like we lose hair, which quills are--long, hard hairs.

And wow, do porcupines have a lot of quills; something like 30,000. But with 29 different species of porcupine in the temperate and tropical Americas, Africa, Asia and Southern Europe, there are significant differences. Regarding quills, for example, the North American porcupine quills are tipped with several hundred barbs. African porcupine quills are much longer, but they’re smooth.


North American porcupine quills (centimeters).
African porcupine quills are 3 to 5 times longer.
(photo by Jeroen Moss, www.wildlifeweb.nl)
Quill Penetration and Removal

Here’s the news from Harvard. Although those African quills are smooth and the North American quills are barbed, our home team quills needed only about half the force to penetrate samples of pig skin.

If that doesn’t impress you, try this: Comparing barbed quills with barbed quills that had been sanded to a smooth surface, the researchers found the barbed quills required only about half the force to penetrate the pig skin.

Still not enough, eh? OK. The piece de resistance: The North American barbed quills needed only about half the force (56 percent) of a comparable diameter hypodermic needle to poke the pig skin.

While the barbs facilitated the going in part, you won’t be astounded to learn they greatly impeded the coming out part. Testing showed that, once embedded, the barbed quills were about four times harder to remove. That’s either ouch! or hmmm...how can we make use of that?

Wrap Up

Overall, the findings may lead to improved or new medical devices, ranging from needles and surgical instruments for penetration or vascular tunneling to tissue adhesives. Like other ideas that have been inspired by biological mechanisms or laws, the findings may also impact other fields. That’s pretty exciting. Thanks for stopping by.

P.S.

- Research paper in Proceedings of the National Academy of Sciences:
http://www.pnas.org/content/109/52/21289
- Article on research in Science
http://news.sciencemag.org/sciencenow/2012/12/porcupine-quills-reveal-their-pr.html?ref=hp
- Article on research in Discover:
https://blogs.discovermagazine.com/notrocketscience/2012/12/11/why-porcupine-quills-slide-in-with-ease-but-come-out-with-difficulty/#.UUTZk1es-So
- Wikipedia write up on porcupines:
http://en.wikipedia.org/wiki/Porcupine

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