The Search for Extraterrestrial Life

07 December 2003
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This week Simon Goodwin joins The Naked Scientists to discuss the search for extraterrestrial life, the SETI (Search for Extraterrestrial Intelligence) Project, and whether we have found any real evidence for the existence of alien neighbours.

In this episode

Bears Hold Key To Osteoporosis Prevention

Black Bears seem to be unique amongst hibernating animals because they have the unique ability to stop their bones from thinning during their long winter sleep, suggesting that they may hold the key to preventing bone thinning diseases, like osteoporosis, in humans. Usually, any period of prolonged inactivity, without weight-bearing exercise, including being immobile, elderly or even going into space, can lead to significant bone loss. But by studying the metabolism of hibernating bears, Seth Donahue and his colleagues from Michigan Technological University have found that, unlike people and other animals, bears keep laying down new bone even when they are inactive. The researchers think that this is because, unlike most hibernating animals, bears don't urinate or defecate so they have no way to get rid of waste calcium from the body – so instead they put it into their bones. To find out how they do this the researchers are now looking for differences between humans and bears amongst some of the key hormones that regulate bone density and calcium metabolism. This may lead to new therapies for the prevention or reversal of human bone loss. Osteoporosis is a serious problem with 50% of women and 25% of men over the age of 50 suffering a fracture because of it.

SEA SLUG - Elysia crispata

- Nature's Own Genetically Modified Slug

The sacoglossan sea slug has stolen genes and chloroplasts from the algae it eats.

Nature's Own Genetically Modified Slug

You've heard of the body-snatchers, but what about the gene-snatchers?

Biologists at the University of South Florida studying the DNA blueprint of the sacoglossan sea slug (Elysia crispata) were surprised to find that the slug appears to have stolen some of its genes from the algae it eats.

Algae are tiny water plants that, like plants on land, contain chloroplasts, nature's solar cells, which they use to harness sunlight to make energy. When the slugs eat the algae the cells lining their intestines pick up the chloroplasts, intact, and use them.

In fact, if you shine light on the slug it produces oxygen and takes up carbon dioxide, like a plant does!

The chloroplasts survive inside the slug cells for several months and even continue to make proteins. And it was when they studied the slug's DNA blueprint, that researcher Skip Pierce and his team found the slug carried a gene coding specifically for one of these chloroplast proteins.

So how did the slug steal the gene? At the moment the team aren't sure, but they suspect that a virus might be responsible.

The team hope that by learning how nature has produced its own genetically modified slug (which contains algae genes !) we might be able to use the same molecular subterfuge to improve our current gene therapy techniques.

Spray on Contraceptives

The world's first female contraceptive spray will begin trials in Australia next year. The idea behind the spray is to reduce the doses of contraceptive needed to be effective and to deliver a steady supply of the drug- a synthetic version of the sex hormone progestin. One of the problems with the oral contraceptive or pill, is that the concentration of the hormone in the body peaks after taking the pill and drops off very rapidly, so that women need to take the pill at the same time each day to make sure the levels of progestin stay high enough to be effective. The pill also needs to pack quite a high dose of hormone to maintain high enough levels in the blood for 24 hours. The contraceptive spray behaves in a similar way to water-resistant sunscreens, which modify the structure of the outer layer of skin allowing the chemicals to penetrate. Once under the skin the hormone collects in a reservoir and then slowly and steadily defuses into the bloodstream. By using lower concentrations of hormone in the spray, it should hopefully reduce the various possible side effects that are associated with taking the pill. Breast feeding women could also use it knowing that any hormone that was secreted into milk would be broken down in their baby's gut.

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