Tuesday, July 17, 2012

Interesting zombie blogs

There has been a lot of interest in my Zombie Protocol series so far, and for that I want to thank everyone who has wandered into the Dark Laboratory (even if you were just looking for the little girls' room).  Zombies are always hot around Comic Con, and there is always some new book or movie coming out.  It's easy to find pop culture information on the next apocalypse, but much harder to find scientific discussions about the phenomenon (hence, this blog!).

Tara Smith  had a nice piece yesterday in Science Blogs about teaching children science concepts using zombies as a backdrop (here's the link).  Disease transmission, pandemics, zombie bugs, neurobiology, and other biological topics were used to discuss what strategies the kids would use for different types of zombie outbreaks.  They also used watermelons as, um, volunteers, to compare the effectiveness of various weapons.  Where were these people when I was in school!!
Coolest logo EVER!

Anyhow, I'm also starting to include links on the right to various sources of zombie science.  Scott Kenemore's blog is doubly good as it also discusses new zombie books and movies.  He's also on the advisory board of the Zombie Research Society, which looks a little tongue-in-cheek but has some heavy hitter scientists on their Board. Coincidentally, Tara Smith is also on the Advisory Board.   Both sites have an occasional discussion about scientific literature and are worth a read.  If you know of other sites that have a scientific bent to zombie research, or any other topic that might be of interest to the Lab, please leave a note below.  Spam will, of course, be fed to the zombies...

Wednesday, July 11, 2012

The Zombie Protocol, Part 2

File:Bufotenin Structural Formulae V.1.svg
Bufotenine: Zombie Poison
With 'bath salts' in the news these days, there is suddenly a lot of interest in zombification.  If you recall, in part 1 of the Zombie Protocol, I described the role of tetrodotoxin in the creation of Haitian zombies.  There are, however, other ingredients in the zombie poison that have significant pharmacological activity.  Besides related TTX toxins from other species of fish, there can also be poisons from frogs, reptiles, and spiders.  The poison from the frog, Bufo marinus, is of particular interest as it contains bufotenine (5-hydroxy-N,N-dimethyltriptamine, or 5-OH-DMT).  Bufotenine is an alkaloid related to DMT and 5-MeO-DMT, as well as psilocin (one of the psychedelic molecules found in mushrooms).  It is also related to serotonin, a well-known neurotransmitter.
Serotonin: Important neurotransmitter
Therefore, it seems very plausible that bufotenine is present in the zombie powder to enhance the effect of the tetrodotoxin.  Remember from my last post that TTX is present at sub-lethal doses (in some studies, the amount of TTX is very low -- see Benedek and Rivier, Toxicon 27:473-480, 1989), so other components of the powder could be necessary to boost the effect of the mixture without killing the victim.  Psychoactive substances would also be very effective since the victim is likely to be conscious while under the influence of TTX.  I mentioned the Poe-like experience of being buried alive without any way to move or scream... now imagine that happening while having horrible hallucinations!  You talk about a bad trip!!

Seed pods from Mucuna pruriens (Wikapedia)
Plants known to be irritants were also added to some of the zombie powders.  In Wade's paper (abstract), he lists Urera baccifera, Dalechampia scandens, and Mucuna pruriens as some of the more common plants.  These plants all have irritating hairs or needles that cause contact dermatitis. In the case of M. pruriens, the hairs on the seed pods contain (interestingly enough) serotonin.  Why would irritants be important to a zombie poison?  Personally, I think this is one of the ingenious parts of the protocol... the irritants are there for delivery.  To pull off the zombification, a voodoo priest would have to administer this part of the poison without the victim's knowledge.  Poisoning food or using darts are quite tricky, but what about a chance encounter on the busy streets of Port-au-Prince?  You have the drug cocktail smeared on the end of a walking stick, or some other convenient device.  Following your target through the busy streets, you wait until you have a good opportunity.  He's distracted by a street vendor, so you bring the stick high and as you pass behind him, you gently poke him in the back of the neck.  He may not even notice but after you have left, he feels a burning sensation and scratches it.  The itching and burning intensifies until he scratches it raw.  The drugs are now able to enter the blood and begin the process of poisoning the victim.  He won't remember the chance encounter, but you know he will be at the hospital soon, and at the morgue not too long after that.

I know I promised zombie cucumbers in Part 2... but they will show up in Part 3, I promise.

Friday, July 6, 2012

T. gondii in the news again

     It's been bat shit crazy in the Not-So-Dark Laboratory (otherwise known as my day job), so my apologies for getting behind on the real crazy science.  One of my first posts (zombie science) talked about zombie science and the potential role of Toxoplasma gondii. T. gondii is a neurotropic protozoan parasite that has been linked to a variety of mental disorders. When rats are infected, they lose many of the behavioral adaptations that protect them from cats and aggressively try to get themselves eaten.  Sadly, the effect of T. gondii on humans seems more subtle. But there is a new paper out on the relationship between T. gondii and suicide, which provides stronger evidence that this parasite is a potentially serious global problem.
     Several recent studies have shown that T. gondii affects human behavior. A meta analysis published in 2007 (abstract) found that there is a correlation between schizophrenia and serum antibody levels against T. gondii.  The predictive power of the association was weak, since more that one third of the entire population is thought to be seropositive for T. gondii, and aside from a few ex-girlfriends and that driver on the 15 the other day, not all of them are crazy. One flaw with the meta-analysis is that it was not clear when the patients were infected relative to the onset of disease.  If they all got T. gondii after they became schizophrenic, then the association is meaningless.  The new study just published by Pedersen et al. (abstract) tries to account for that by measuring T. gondii antibody levels when women gave birth (using samples from heel-stick cards in the birth records) and then looking at the risk of depression and suicide later in their life. Seropositivity was 26.8% at delivery, consistent with the notion that 1/3 of the population has already been infected (remember that infants don't start making their own antibodies for about three months after birth, so these are the mom's antibodies).

From Pedersen et al, Arch. Gen. Psych. 2012.
Pedersen et al. found that seropositive women had a 1.53-fold greater risk of self-directed violence (ie, suicide) than seronegative.  Women with the highest antibody titers had nearly a 2-fold higher risk.  The risk is small, but significant and is also consistent with other recent studies on the relationship between T. gondii antibody titers and mental illness (for example, see this).  I'm generally not a big fan of these types of analyses, because the data could simply be a case of "true, true, and unrelated".  There is no mechanistic hypothesis for why antibodies against T. gondii would alter behavior, or whether the infection caused permanent damage to the brain.  However, evidence continues to accumulate that T. gondii infection can cause permanent changes in human behavior, and with billions of people having been infected at some point, it isn't too hard to see the beginnings of a zombie apocalypse.