- Close Encounter with Saturn Moon’s Fantastic Plumage
- Out of the Blue: Islands Seen From Space
- Gene Therapy Halts Fatal Brain Disease
Posted: 06 Nov 2009 09:56 AM PST
Earlier this week, NASA's Cassini spacecraft took its deepest dive ever through the center of the icy plume shooting out from the southern pole of Saturn's moon Enceladus.
NASA reports that the spacecraft survived Monday's flyby in good health, and is now transmitting eagerly awaited data and images back to Earth. At its closest point, Cassini dipped just 60 miles above the surface of Enceladus. Although previous flybys have gotten even closer, this trip included the spacecraft's deepest foray into the south polar plume, which was discovered in 2005 and is known to contain water vapor, sodium and organic molecules.
As Cassini gathers more and more information about the composition and density of the plume, scientists hope they'll be able to identify the source of the gas. If the source is a liquid ocean underneath Enceladus' icy crust, it could harbor life if conditions are right. To fly through the plume safely, however, mission managers had to conduct extensive pre-trip studies and make sure the spacecraft didn't use too much propellant.
Cassini captured the unprocessed image above using its narrow-angle camera at a distance of about 120,000 miles away from the moon. As sunlight bounces off the moon's crescent edge, it highlights the mysterious misty plume at the southern pole.
Image: NASA/JPL/Space Science Institute
Posted: 05 Nov 2009 05:00 PM PST
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Islands are some of the most beautiful, peaceful, violent, desolate and unique places on Earth. While experiencing a tropical island from its sandy beaches, or a volcanic island from its towering peaks is wonderful, experiencing them from above can be inspiring as well.
We've collected images taken by astronauts and satellites from space of some of the most interesting islands on the planet.
Atafu Atoll, Tokelau, Pacific Ocean
Around 500 people live on Atafu Atoll, mostly in a village that can be seen on the corner in the left of the image above. Atafu is just five miles wide and is the smallest of three atolls in the Tokelau Islands, a New Zealand territory.
Atafu is made up of coral reefs that surrounded the flanks of a volcano that has since become inactive and submerged. Like many tropical atolls, Atafu is very low lying and vulnerable to sea-level rise. This photograph was taken by astronauts aboard the International Space Station in January.
Posted: 05 Nov 2009 11:00 AM PST
Scientists have used gene therapy to halt the progression of adrenoleukodystrophy, a fatal neurodegenerative disease caused by a single defective gene, in two seven-year-old boys.
It took more than a decade to refine the therapy, in which stem cells taken from the boys' bone marrow were hacked with healthy copies of the gene, then returned to their bodies. Without them, the boys would soon be dead.
"They would now be unable to speak, to walk, to communicate, to sit, to eat. They would be in an advanced stage of the disease, in a vegetative state," said Patrick Aubourg, a pediatric neurologist at France's National Institute for Health and Medical Research who led the treatment's development. "Instead they go to school. They live a normal life."
The gene at the root of adrenoleukodystropy — ALD for short — is called ABCD1, and produces a protein necessary to maintain myelin, a compound that acts as an insulator for nerve fibers in the brain and peripheral nervous system. As myelin degrades, the fibers cannot conduct electrical impulses.
The boys who received the treatment suffered from the early form of ALD, in which the defective gene is found only on the X chromosome. His story is described in a paper published Thursday in Science. Technically known as X-linked ALD, it affects boys, typically starting in childhood and killing them in two to three years. It can be treated with bone marrow transplants, but success rates are low, and toxic immune system-suppressing drugs are needed to prevent patients' bodies from rejecting foreign tissue — if, that is, a donor can even be found.
No such donor was found for the children, who had just a six-month window after diagnosis in which treatment could be started. After that, it would have been too late. So their parents turned to Aubourg's therapy, which had only been tried in laboratory animals.
One of the children — their identities remain confidential — received the treatment two and a half years ago. The other received it three years ago. In both, the disease has stopped progressing. Their brains scans show myelin damage that has stopped, and their new genes are active as ever.
The results are as striking as any previously delivered by gene therapy, a biotechnological technique that after nearly two decades of anticipation has largely failed to deliver on its lab-bench promise — though that may be changing.
"There is reason to think that this will last for the rest of their lives," said gene therapist Nathalie Cartier of NIHMR, the study's lead author.
In 1993, when Aubourg discovered how to duplicate the ABCD1 gene in a laboratory, he envisioned adding it to blood stem cells, which give rise to the different types of blood cells — including, critically, the cells that make myelin. Every new cell would produce the correct protein. The ALD would disappear.
This type of approach is one example of gene therapy, a technique that even now is highly experimental, and was more experimental then. The first "vector" used by Aubourg — a virus engineered to carry new genes into target cells — succeeded in delivering its payload just .001 percent of the time. Even this miniscule success rate was enough to improve symptoms in mouse models of ALD, but he didn't trust it to work in people.
Aubourg went back to the drawing board. He used a new vector made from a human immunodeficiency virus from which the genome had been removed, leaving only HIV's cell-penetrating shell. Inside this he put the new ABCD1 gene, and a string of DNA that helps it fuse with target chromosomes.
The new vector, called a lentivirus, didn't work all the time, but it was far more efficient than the old one. In the two boys who received the treatment, 15 percent of the stem cells in their bone marrow now possess a copy of the healthy ABCD1 gene. These cells are essentially immortal, and should provide a steady supply of healthy myelin-producing cells in perpetuity.
"Even this low-end number is high enough," said Aurora Pujol, an ALD researcher at Spain's IDIBELL Research Institute. She knew the two boys when they were patients at a hospital in Spain, waiting in vain for bone marrow transplants, and connected them to Aubourg's laboratory. "They did a great job."
The boys did not escape unscathed, and still suffer from some cognitive difficulties. And though no side effects have been observed, far more testing is needed to be certain that the treatment is safe. "The risk is never zero," said Auborg.
Indeed, gene therapy is still best-known for its high-profile failures. In 1999, 18-year-old Jesse Gelsinger died during tests of a gene therapy for a rare metabolic disorder. In 2003, two French children receiving treatment for severe immune deficiencies developed leukemia.
But with the recent success of a gene therapy for blindness, and the refinement of new, apparently more reliable methods, gene therapy may have turned a corner.
"This is an important step forward for ALD, but not only for ALD," said Pujol. "The lentiviral vector approach can be applied to other single-gene diseases."
Jeffrey Rothstein, a Johns Hopkins gene therapist who specializes in Lou Gehrig's disease, warned against extrapolating too much from the early ALD results. "It's great that it worked, but that doesn't guarantee success in other diseases," he said.
But University of Pennsylvania bioethicist Art Caplan, who has followed gene therapy since its beginning, shared some of Pujol's excitement.
"I think this is the beginning of a turnaround," he said. "It took a long time to move from animal research to clinical success. It took more than a decade to get anywhere. But these breakthroughs show that this long-touted technology is about to produce clinical benefits."
Image: Over the course of two years, the breakdown of myelin in a boy with ALD who did not receive the therapy (above) and one who did, from Science.
Citation: "Hematopoietic Stem Cell Gene Therapy with a Lentiviral Vector in X-Linked Adrenoleukodystrophy." By Nathalie Cartier, Salima Hacein-Bey-Abina, Cynthia C. Bartholomae, Gabor Veres, Manfred Schmidt, Ina Kutschera, Michel Vidaud, Ulrich Abel, Liliane Dal-Cortivo, Laure Caccavelli, Nizar Mahlaoui, Véronique Kiermer, Denice Mittelstaedt, Céline Bellesme, Najiba Lahlou, François Lefrère, Stéphane Blanche, Muriel Audit, Emmanuel Payen, Philippe Leboulch, Bruno l'Homme, Pierre Bougnères, Christof Von Kalle, Alain Fischer, Marina Cavazzana-Calvo, Patrick Aubourg. Science, Vol. 326 No. 5954, November 5, 2009.
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