Sunday, January 29, 2006

Luminescent Owls

So I was having my usual midday walk through McCorkle Place on campus when I saw something pretty neat - a hawk chasing an owl! The big grey owl flew into a large hole in the ancient Davie Poplar and the hawk, dropping the pursuit, flew up into the branches of another tree. Where upon it was then chased off by yet another hawk that swooped in after it. Usually it's quite cool to just see one hawk soaring around, so this was something else. I was also amused to see the complete absence of any squirrels in the park, as it is usually knee-deep with them. I imagine there wouldn't be any people out walking if there were a couple of hungry tigers and a grizzly bear prowling around. After another couple of hours of coding I went back out for another walk and found the owl was still perched in the same large hole in the poplar tree. Convinced it would stay there for a few more minutes, I went to go get Val and his camera, and we got the following picture (Ok Val hasn't sent the picture yet - I'll add it when he does).

So I then go googling around to learn about owls, and I found something that I thought was really amusing. Everyone probably heard about the Will o' the Wisp when they were kids - stories of mysterious glowing lights that would float over the countryside at night. Well, while browsing through the articles on the Owl Pages I found this: A Review of accounts of luminosity in Barn Owls Tyto alba. He is arguing that bioluminescent owls are to explain for the Will o' the Wisp myth! Why would the owls be glowing? The first explanation proposed is that from time to time the owls will get bioluminescent organic material in their feathers from roosting in old trees that have luminescent bacteria or fungi growing in them (like Foxfire - see picture below).

The article linked to above then goes on to suggest that this is not the correct explanation, but rather that some owls are naturally bioluminescent. This seems a great deal less plausible to me than foxfire-smeared owls, although it isn't completely inconceivable. Genome sequencing is going be much cheaper in the future (I look forward to having mine decoded), and by the 2020s most animals and plants (and a lot of the fungi and bacteria) should be sequenced, so perhaps at that point you could just go over to google and simply ask "Hey, are there any owl genes that could code for bioluminescent proteins, or are perhaps a mutation or two away from doing so?" and get a quick answer (I suspect it would be no in this case).

So, have any glowing owls actually existed over the centuries, out swooping after field mice in the cool night air, to the bewilderment of onlooking European peasants? It's a charming idea, but it might just be the result of an overactive ornithological imagination. Then again, I wouldn't be surprised if they do exist - the earth, at 510 million square kilometers in surface area, is a rather large place, and is filled with all sorts of fascinating creatures.

Monday, January 09, 2006

RNA interference

2006 started out rather badly for me, as I was sick as a dog when the ball dropped (specifically, a dog with an adenovirus infection). Now a week later I feel mostly better, but I'm still coughing a good bit, especially when I try to go to sleep. Anyways this has gotten me interested in current research for curing diseases, and in particular a new technique that I had heard about for the first time earlier in 2005: RNA interference. It is a very neat technique that has apparently been around for hundreds of millions of years in eukaryotes - helping them to fight viruses and aiding in gene regulation - but we only discovered it existed quite recently.

Here's the idea. In general a virus will slither up to a healthy cell and insert it's genetic code (either DNA or RNA) into it, and this code will then instruct the cell's ribosomes to produce the proteins needed to construct many more copies of the virus. Some viruses belong to the double stranded RNA (dsRNA - see virus classification) group, which insert complementary strands of their RNA into the cell, and many other viruses use dsRNA during their life cycle. The presence of dsRNA in a cell is a sign of viral attack, since the normal messenger RNA (mRNA) produced in the nucleus is single stranded, and fittingly it is this dsRNA that the cell's RNA interference mechanism uses to fight back against the viral infection. When the Dicer enzyme finds a long dsRNA segment, it will cut out a short chunk from it, around 20 base pairs long, thus destroying the original dsRNA (the short excised segments are called small interfering RNA - siRNA). Furthermore, other proteins will then join with the siRNA segment, forming a RNA-induced silencing complex (RISC). The RISC molecule becomes activated when one half of the siRNA double strand is peeled off (which requires some energy to break the hydrogen bonds). Now the activated RISC will check with other messenger RNA strands, and if it finds a sequence that complements it's own siRNA strand then it will chop that mRNA segment in two, destroying it. Thus introducing a dsRNA segment that corresponds to a particular gene into a cell will result in the suppression of that gene, a surprising result if one doesn't know about the mechanism that lies behind it (as it was at first - gene therapies that were intended to increase the purple pigmentation in petunias ended up producing white flowers...).

RNA interference should allow for all sorts of great targeted attacks against the bacteria and viruses that stalk us. Any pathogen that attacks us will necessarily use genes that we don't - thus we should be able silence those genes, and the illness as well, by introducing the corresponding dsRNA segments. That said, while initial trials have shown promising results and more are in the pipeline, we probably won't see widespread RNAi therapies for another 10 or so years, as they will have to go through FDA approval and so forth. In the near term the most exciting aspect of RNAi will be it's use in decoding the genome: essentially by targeting one gene at a time and turning it off with RNAi and seeing the resulting effects in the cell, you can figure out what that gene does.

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