Friday, July 6, 2012

Hypothesis: Microbes Generate Toxins of Power - 6

Ancient Microbial Neurosurgeons
I am interrupting the flow of this series to change the expected topic, from a look at stem cells as was intended, to a look at microbial influence on the functioning of the human brain (see The Human Microbiome Congress).

Instead, this post will focus on some experimental and observational data that will bring more focus to this series.

We pause for more focus on the effects and affects that microbes have on human behavior.

Before going on into stem cell dynamics, which will still be discussed in a future post, I want to double down on the known science available which strongly supports the general premise involved in the notion that microbes can and do affect our thinking and/or our behavior.

This post will startle you, if previous ones haven't yet.

The bulk of scientific research that has been used in this series, so far, has been from microbiologists who were taking a look at primarily symbiotic relationships human cells have with microbial cells (see On The New Meaning of Being Human).

That involves microbes taking part in the development of our brains in ways that end up helping us as we help them (see Hypothesis: Microbes Generate Toxins of Power - 5).

That cooperation and peace can seem bland in some ways, possibly because of movies, television, and the like, where shoot-em-up bang-bang is the norm.

So, to grab your attention and focus on the earth-shaking reality we are talking about in this series, we will hold off on the discussion of stem cells to instead take a quick look at a parasitic microbe, one that does not have the good manners that symbiont microbes have.

That parasitic microbe is the protozoa Toxoplasma gondii ("Toxo") which, as a world renowned scientist explains, has incredible abilities:
The parasite my lab is beginning to focus on is one in the world of mammals, where parasites are changing mammalian behavior... Toxo instead has developed this amazing capacity to alter innate behavior in rodents... If you take a lab rat who is 5,000 generations into being a lab rat, since the ancestor actually ran around in the real world, and you put some cat urine in one corner of their cage, they're going to move to the other side. Completely innate, hard-wired reaction to the smell of cats, the cat pheromones. But take a Toxo-
"Complex" Is An Understatement
infected rodent, and they're no longer afraid of the smell of cats. In fact they become attracted to it. The most damn amazing thing you can ever see, Toxo knows how to make cat urine smell attractive to rats. And rats go and check it out and that rat is now much more likely to wind up in the cat's stomach. Toxo's circle of life completed.

... part of my lab has been trying to figure out the neurobiological aspects. The first thing is that it's for real. The rodents, rats, mice, really do become attracted to cat urine when they've been infected with Toxo. And you might say, okay, well, this is a rodent doing just all sorts of screwy stuff because it's got this parasite turning its brain into Swiss cheese or something. It's just non-specific behavioral chaos. But no, these are incredibly normal animals. Their olfaction is normal, their social behavior is normal, their learning and memory is normal. All of that. It's not just a generically screwy animal.

You say, okay well, it's not that, but Toxo seems to know how to destroy fear and anxiety circuits. But it's not that, either. Because these are rats who are still innately afraid of bright lights. They're nocturnal animals. They're afraid of big, open spaces. You can condition them to be afraid of novel things. The system works perfectly well there. Somehow Toxo can laser out this one fear pathway, this aversion to predator odors... Toxo preferentially knows how to home in on the part of the brain that is all about fear and anxiety, a brain region called the amygdala... Toxo knows how to get in there.

Next, we then saw that Toxo would take the dendrites, the branch and cables that neurons have to connect to each other, and shriveled them up in the amygdala. It was disconnecting circuits. You wind up with fewer cells there. This is a parasite that is unwiring this stuff in the critical part of the brain for fear and anxiety... It knows how to find that particular circuitry... Meanwhile, there is a well-characterized circuit that has to do with sexual attraction. And as it happens, part of this circuit courses through the amygdala, which is pretty interesting in and of itself, and then goes to different areas of the brain than the fear pathways... Toxo knows how to hijack the sexual reward pathway. And you get males infected with Toxo and expose them to a lot of the cat pheromones, and their testes get bigger. Somehow, this damn parasite knows how to make cat urine smell sexually arousing to rodents, and they go and check it out. Totally amazing... So what about humans? A small literature is coming out now reporting neuropsychological testing on men who are Toxo-infected, showing that they get a little bit impulsive... And then the truly astonishing thing: two different groups independently have reported that people who are Toxo-infected have three to four times the likelihood of being killed in car accidents involving reckless speeding... Maybe you take a Toxo-infected human and they start having a proclivity towards doing dumb-ass things that we should be innately averse to, like having your body hurdle through space at high G-forces. Maybe this is the same neurobiology... On a certain level, this is a protozoan parasite that knows more about the neurobiology of anxiety and fear than 25,000 neuroscientists standing on each other's shoulders... But no doubt it's also a tip of the iceberg of God knows what other parasitic stuff is going on out there. Even in the larger sense, God knows what other unseen realms of biology make our behavior far less autonomous than lots of folks would like to think.
(A Talk With Dr. Sapolsky). Bingo, remember that this series is about a hypothesis that microbes may be the source of the toxins of power that corrupt the minds of officials who inhabit offices of power.

Part of this working hypothesis has been that the work the toxins do is focused on the human amygdala (see The Toxic Bridge To Everywhere).

We now know that there are symbiont microbes who help us in countless ways, and now we also know that there are microbes that are parasites, that is, they are not concerned with our best interests.

The previous post in this series is here.

1 comment:

Randy said...

Scientific American has a piece about the Toxo: Link