science snippets

I’ve been fooling around with the Bloglines blog feature, and considering turning it into a sidebar feed for this site. But then again, why not just make a second MT blog? In the meantime, I thought I’d recycle a few entries here.

scissors icon Developmental patterning: this one’s for PZM. Double-segment periodicity underlies ‘odd’ segment generation in centipedes
Apparently, centipedes have between 15 and 191 pairs of legs, and the number is always odd, and we don’t know why. The paper to which this story refers indicates that segments are defined in pairs in the developing centipede embryo, and each segment develops a pair of legs. So why odd, and not even? The authors speculate that development of the forcipules (“poison claws”, which are modified legs) reduces the resulting even number by one, resulting in an odd number. So the actual mystery mechanism in question is, what programs the forcipule development?
Bah. I just read the abstract, and the real story is how the co-ordinated expression of two different genes lays down a pattern of single-segment periodicity. That’ll teach me to blog from the report not the paper.
Heh. Update to the update: the single segment periodicity is probably laid down in cycles that generate two segments each, and the generation of odd numbers of leg pairs may indeed be due to the extension of this process as far as the segments containing forcipule, genitals and so on. So the report was right, but (I found it) confusing. That’ll teach me to trespass on Prof Myers’ territory.

scissors icon German science newsfeed. If you read German, this newsfeed, which I found by browsing science-related feeds at, is quite often well ahead of the English language feeds on my blogroll. For instance: yawning chimpanzees (German feed July 24, English feed July 26), the oncomouse patent (German feed July 6, English feed July 26) and the world’s smallest fish (German feed July 7, English feed July 21).
Note that this works even for pretty feeble values of “read German”. I can get the gist of most stories without help, but need translation help and/or a dictionary to actually understand what’s going on. In fact, I originally added the feed to motivate me to pick up learning German again.

scissors iconColour perception is not innate, but acquired after birth.
The abstract is here. Monkeys raised for a year under monochromatic lights showed clear differences in their colour vision compared to those raised under normal conditions. I wonder how this relates to colour-related learning in humans with colour deficient vision (like, say, me).

scissors icon Gene therapy reaches muscles throughout body, reverses muscular dystrophy. The paper will be in the August Nature Medicine, the abstract is available here.
Researchers at the Muscular Dystrophy Cooperative Research Center at the University of Washington School of Medicine have built an adeno-associated virus vector which specifically, and without eliciting an immune response, delivered an engineered dystrophin gene to every skeletal muscle, and the heart, of adult dystrophic mice. (Disruption of dystrophin production causes Duchenne muscular dystrophy in humans; without reading the paper, I assume the mouse is a knockout/similar model of the same disorder.) One injection of the viral vector caused a “dramatic improvement” in the animals’ dystrophy.
Not only is this an important proof of principle for muscle-targeted gene therapy, it may be useful in other genetic disorders which do not even involve muscle tissue but simply require widespread expression of the therapeutic gene.
Something else that’s good to see: the director of the MDCRC stressed that “the paper represents one discovery on the long path to any clinical applications in people [and] that there are a number of scientific challenges and regulatory requirements along the way, so any tests on humans are many years in the future” — and the reporter included those quotes.

scissors icon Chagas parasite invades genome (abstract here).
Trypanosoma cruzi kinetoplast DNA sequences end up in the host genome, opening up the possibility of some pretty freaky horizontal transfer of genetic information, plus influence on host evolution via mutation and creation of recombination hotspots. The article doesn’t say “first time ever documented outside of retroviruses” so I guess other instances are known — but I’d never heard of them.

scissors icon ET first contact ‘within 20 years’
Heh. Bullshit. Publicity seeking bullshit. (Don’t get me wrong though, I *love* SETI and related goals/ideas; if this guy can bring in funding, more power to his bullshit generator.)