Tapeworms and drug delivery
It's not easy living inside an intestine. But some creatures are happiest in the warm and juicy confines of other animals' digestive systems. A tapeworm called Hymenolepis diminuta, for instance, can live for years in a rat's intestine, growing up to a foot long.
One of the biggest challenges to gut living is all the churning that happens in there. Between meals, the muscles in a mammal's intestine contract rhythmically to flush out waste and bacteria. Somehow, tapeworms manage to slow down the contractions enough to stay inside. They even swim up and down the intestinal tract as food moves through.
A preserved tapeworm.
Now, scientists at the University of Wisconsin think they've discovered one of the tapeworm's secret weapons: a chemical called cyclic guanosine monophosphate, or cGMP. Research by John Oaks and colleagues suggests that cGMP helps slow intestinal contractions.
The new work may help scientists develop more effective medicines. Because molecules move more slowly through rat intestines that are infected with tapeworms, the scientists think a dash of cGMP could slow down the movement of pills after they've been swallowed. That would give the body more time to absorb medicine in the pills, letting less go to waste.
So, even though the life of a tapeworm might not sound pleasant, studying the icky parasites more might do us some good.—E. Sohn
Travis, John. 2003. A tale of the tapeworm: Parasite ploy suggests drug-delivery tactic. Science News 163(March 22):181-182. Available at http://www.sciencenews.org/20030322/fob6.asp .