Normal Limits

"Chance is the very guide of life"

"In practical medicine the facts are far too few for them to enter into the calculus of probabilities... in applied medicine we are always concerned with the individual" -- S. D. Poisson

November 02, 2005

NYT - Parasitic Hairworm Charms Grasshopper Into Taking It for a Swim

Nicholas Wade (NYT Science Desk):
The parasite, known as a hairworm, lives and breeds in fresh water. But it spends the early part of its life cycle eating away the innards of the grasshoppers and crickets it infects.

When it is fully grown, it faces a difficult problem, that of returning to water. So it has evolved a clever way of influencing its host to deliver just one further service -- the stricken grasshopper looks for water and dives in.

The original article Biron et al 2005 in Proceedings of the Royal Society Series B. Note that this was studied with a proteomics approach.
The larva of the wasp Hymenoepimecis spp, a parasite of the orb-weaving spider, somehow convinces its host to weave a unique and durable platform for the larva's cocoon (Eberhard 2000 in Nature, a fascinating article with pics).

The parasite Toxoplasma gondii has a unique, seemingly paradoxical cycle involving the cat and the mouse. In order to accelerate this process, it alters the olfaction of the host mouse, such that the mouse is drawn to the smell of cats. This is specific and does not disturb the rest of the mouse host's olfaction. (See Robert Sapolsky article in Scientific American, also collected in his latest book Monkey Luv).

Finally, something to think about is the recent finding of fetal microchimerism in the brain. This is a jaw-dropping study from the National University of Singapore, Chinese Pharmaceutical University, Osaka University, and The Institute of MCB in Singapore. In this study, Tan et al 2005 in Stem Cells showed that in the pregnant lab mouse, fetal cells find their way into the maternal circulation, take residence in the mother's brain, and grow into neuron-like or glia-like cells. In some regions of the mother mouse's brain as much as 1/1000 of the neurons are of fetal origin. I will not be surprised if in a follow-up study these neurons and glia are found to be participate in maternal CNS function, long after the fetus has been delivered.

Bill Cosby:
"No matter how calmly you try to referee, parenting will eventually produce bizarre behavior, and I'm not talking about the kids. Their behavior is always normal."

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