Thursday, July 29, 2010

Good olden tyme science (now with Squid Axon videos!)

Isis posted an awesome video of physiologist John Severinghaus discussing his work on altitude, while working on White Mountain Research Station. Very interesting, and from this neurogeek's perspective, a part of physiology that I know little about.

It got me thinking about the great old experiments in my own subfield of ion channels and electrical excitability. I'm a big fan of going back and actually, you know, reading the foundational literature in the field. That's just me, I don't expect everyone to love it, but I always wonder at how clearly those greats viewed things, and how much their work shapes the later development of the field (especially with regards to what questions are considered important).

For electrophysiology, this leads to One Prep, One Prep to Rule Them All:


As most biologists likely learned at some point in school, the squid giant axon provided the system that Alan Hodgkin and Andrew Huxley used to analyze the basis of the action potential. Nowadays though, I'd gather there aren't many electrophysiologists who have actually seen the axon or it's beautiful action potential in real life. I know I haven't.

Luckily, we have our own kick ass old science videos. Back in the 1970s, J.B. Gilpin-Brown at the Marine Biological Laboratory in Plymouth, England, filmed a movie called "The Squid and its Giant Nerve Fiber". Now, the entire work has sadly been lost, but there are some parts which have been saved. These videos are available at the Bio 300 course site taught at Smith College, and they include J.Z. Young dissecting out the giant nerve (which he was the first to describe). If you're interested in this kind of stuff, I highly recommend you go check them out (Quicktime needed).

My favorite video is the one aboutvoltage clamping the squid axon. Here are some stills I captured from it:

Figure 1:The squid axon action potential. A thing of beauty, no doubt. Complete with hot oscilloscope action (yeah, that ain't digital!). Note the afterhyperpolarization.

Figure 2: Here, Alan Hodgkin, Nobel Laureate, prepares to ACTUALLY DO AN EXPERIMENT ZOMG!!! He's picking up the axon and getting ready to insert the electrode. I know, sorry, it's an old white d00de, wearing a vest and tie ferchrissakes. But I'll admit that I love his papers.

Figure 3: A family of voltage step currents, showing the early inward sodium current followed by the delayed outward potassium currents (responsible for the membrane depolarization and repolarization, respectively). IT'S EXACTLY LIKE THE DAMNED TEXTBOOKS! Hell, I think it might be the textbook figure. Note the slight deviation in the voltage clamp (pesky series resistance; now that's a post for another day), and the potassium tail currents.

Phew, ok, sorry to get all hot and bothered. Beautiful currents will do that to me. Now I need to get to my own electrophysiology. But these are awesome. Anybody got any more old science videos to share? I love this stuff.

1 comment:

Anonymous said...

beautiful. thanks