Tuesday, January 31, 2006

Crunch time for Keith.

Well, I intended to run with the club for their Tuesday night run, and tried to get down to Armand Bayou Elementary by 7:00, but apparently, I don't know where that is. I drove around for a while, and eventually found it, but by then it was already 7:15, and they were out of sight. So I meandered around for 4.5 miles without my watch.

It's crunch time for me at work. I've got two weeks left to turn in the written portion of my qualifying exam (I'm a grad student in biology). I have to design a set of experiments, completely from scratch, on a subject that has nothing to do with the research I'm actually involved in. At first I didn't think it was a good idea to ask students to present their proposal on a completely different field, because it just seemed like a huge waste of time to read tons of papers that aren't really related to your work. But I've actually enjoyed the break from the cutthroat world of Learning and Memory research (I'm not kidding - it really is a rough crowd to work with). I'm supposed to write this up as a 10 page "grant proposal," and then defend it in front of my committee next month.

The topic I chose was to test the recently proposed hypothesis that the mechanism by which migratory birds can sense the magnetic field is based on modulation of the light sensitivity of the birds' photoreceptors. The idea is that the biochemical pathway that underlies phototransduction (conversion of light energy to electrical activity in a neuron) is less efficient when the photoreceptor is aligned with the magnetic field than when it is perpendicular. So, with the retina being curved in a half-ball shape at the back of the eye, some photoreceptors are parallel, and some are off-parallel, and so there would be a bright spot in the bird's visual field in the direction of the magnetic field lines. So, North would look brighter, and East and West not so much.

There is a model for the physics behind this effect, which is also part of the proposal. Hopefully this topic is interesting enough to keep my committee focused on the topic, rather than bored and focused on testing the thickness of my skin.

This is what I learned today - just in case you need this information at some point:
  • You can discriminate between opsin based and non-opsin based phototransduction by Vitamin A depletion.
  • No one does Vitamin B2 depletion in the same way, which sucks because it would really help me. It might be lethal.
  • There is evidence for a photo-active non-opsin based photoreceptor in birds.

I also learned that asking people if they want to see under my bandage is funny only to me.

Rock on.


Lisaleese said...

That is cool. So, your built in compass for birds is for them to follow the bright light.. "Cross over children, go into the light..."

Now - what is the connection of using certain vitamins to check for the photoreceptors?

Dave Smart said...

Interesting, the bird eyes are perpendicular to magnetic north, hence brighter light. I once heard that there was a stone in the bird sinus that lead them to magnetic north, but never researched it. I wonder how they got conditioned to fly south for the winter and north for the summer? Or how a Purple Martin can find its way from Sao Paulo, Brazil to my backyard every year?