For the return of Linkage after a week’s dormancy, here’s an interesting paper from the journal Proceedings of the Natural Academy of Sciences – PNAS, in scientific shorthand – a quickfire roundup.
As one of the most popular addictive substances in the world, tobacco has drawn a lot of research attention. Scientists have long sought the mechanisms by which tobacco – whether smoked, chewed or snuffed – affects the brain, creating its powerful dependence in users and the massive profits and public health problems therein. That happens to be the sub-field in which I did my graduate research, but that’s only part of why a paper this week from scientists at Duke and Wake Forest caught my eye. Measuring nicotine concentrations in the brain while a human subject smokes a cigarette? Pretty cool. Doing it with radioactive cigarettes? Extra cool.
Don’t worry – this process isn’t going to turn anybody into some kind of chain-smoking Hulk. The method was a variation on positron emission tomography, more commonly known as PET scans, used regularly by hospitals to obtain high-quality real-time medical images. In a typical PET scan, the patient drinks or is injected with a radioactive tracer, a safe isotope that allows the scanning machine to map internal organs so doctors can find tumors, measure drug metabolism, or observe brain activity.
In this study, researchers gave test subjects cigarettes loaded with radioactive nicotine – a normal carbon on the nicotine was replaced with a radioactive carbon isotope. The substitution allowed them to track the movement of nicotine in real time as a subject smoked, following it along its path from mouth to lungs to brain. When they did this, two surprises were found: 1) Nicotine concentrations in the brain rise gradually over the course of a cigarette, not in spikes corresponding to each “puff,” and 2) Under controlled circumstances, regular smokers actually achieve lower brain nicotine concentrations than casual smokers.
That latter finding has to do, strangely, with the absorption of nicotine from the lungs to blood, which was found to be slower in heavy smokers. But not to be thwarted, the smokers compensate by taking deeper puffs of their cigarettes, the researchers found, offsetting the slower absorption. The main application of that knowledge is to other studies of nicotine in the brain that are trying to simulate the natural concentrations experienced after a cigarette – like my old experiments which tested the effects of nicotine on a slice of rat brain kept alive for several hours in a dish. But for everyone else, at least now you know what a brain on cigarettes looks like, without the use of egg metaphors.
I want to link to almost every post Jonah Lehrer makes on his blog (and often do through my twitter account), but this one on creativity, brain hemisphere damage and the effects of marijuana is even a cut above his usual musings. Bonus insight from Vaughan Bell at Mind Hacks, making this a big old jam session of my favorite science bloggers.
Emil Coccaro, chair of psychiatry at the University of Chicago Medical Center, appeared in a Wall Street Journal article about when having a foul temper becomes a psychiatric condition called intermittent explosive disorder. Watch out for an article on Coccaro’s IED research appearing here soon.
We’ve talked a lot here about using DNA sequences as a clinical tool for cancer treatment. This New York Times article suggests that the answers may reside in mitochondrial, rather than nuclear, DNA.
Our own Jerry Coyne blogs about the viral science photo of the week, the all-black king penguin. And talks to the Associated Press about the poor quality of two popular biology textbooks for home-schooled kids.
Speaking of Coyne, science and religion are increasingly antagonistic bedfellows, but this article by Dave Munger in Seed gives a good overview of one scientific DMZ where they can reasonably intersect: the study of why religious beliefs evolved in humans.