photo of Tomato Frog, copyright Shedd Aquarium

One frog, one possible cure lost




From Medieval Magic to Modern Medicine page 3

Not all frogs being studied are toxic. Little African clawed frogs (Xenopus laevis) are as much a staple in research labs as white mice, as well as being popular pets. A few years ago, a researcher noticed that his lab frogs quickly recovered from a surgical procedure even though they were returned to their aquariums without treatment. His scientific curiosity aroused, he discovered that the frogs' skin secretes a remarkable antimicrobial compound that disinfects everything it touches.

The secret of the secretion is a peptide, one of a family of small proteins that kill bacteria by rupturing their cell membranes. Potential applications of a synthetic derivative of the peptide, named magainin, seem to be limitless, from a plaque-fighting toothpaste additive to a nontoxic glue for human organ surgery. Among the most exciting possibilities are drugs to treat ovarian cancer and malignant melanoma, the deadliest form of skin cancer.

These pharmaceutical discoveries have occurred at the same time that many frog and toad species are jeopardized by habitat destruction, particularly tropical rain forest species. All Dendrobates and Phyllobates species are classified as threatened. Scientists are concerned that other species harboring chemicals with the potential of epibatidine or magainin will disappear before they can be studied - or perhaps even before they are discovered.

Australia's gastric brooding frog (Rheobatrachus silus) offered hope to people suffering from stomach ulcers. Discovered only in 1973, the species' females confounded zoologists by swallowing their fertilized eggs and incubating them in their stomachs. While the tadpoles were developing, the females did not eat and somehow shut off the production of gastric acids. The tiny froglets "hatched" by being spit up. Researchers speculated that whatever function enabled the frogs to brood their young without digesting them might have applications in treating stomach ailments.

In the spring of 1980, as researchers pursued the mysteries of the species' digestive mechanisms, the gastric brooders and another frog native to the same area did not make their annual appearance in the streams to breed. They have not been seen since and apparently are extinct. The search for a new medicine came to a dead end.

- This article reprinted with permission from the Shedd Aquarium





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