Stem Cells Make Mouse Myelin
Scientists have used human stem cells to repair the damaged spinal cords of paralyzed mice.
The scientists, working at the University of California, Irvine, injected stem cells from the human nervous system into mice they had paralyzed nine days earlier. Four months later, the mice could use their hind legs normally again. To prove that the stem cells did the healing, the scientists later injected a toxin that killed off the human cells, and the mice were paralyzed again.
This isn't the first time scientists have used stem cells to repair rodent spines. But it's a step farther than researchers have gone before. The researchers expected the fetal neural stem cells they injected to form new nerve cells in the mice. But they also formed oligodendrocytes, a type of cell that forms myelin, and that's all new.
What's myelin? And why does it matter? Myelin is an insulating coating, or sheath, around your nerve fibers. It's critical to those fibers' ability to conduct electrical signals, through which your nervous system delivers messages around your body. Diseases that mess with myelin, such as multiple sclerosis, cause sensory and motor problems--and can even lead to paralysis. If new treatments could make new myelin, that could be as important as making nerve cells themselves.
Take a cartoon tour of stem cell science
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Singing Sands Stump Science
Believe it or not, sand dunes can sing. And stumped scientists want to know how.
A 9th-century Chinese manuscript tells of a time when people "would climb Mt. Ming-Sha-Shan and slide together down the sand. The sound made by the sliding was like the rolling of thunder." Marco Polo, crossing the Gobi Desert in the 13th century, heard singing sands, too, which filled the air "with the sounds of all kinds of musical instruments, and also of drums and the clash of arms." Even Charles Darwin puzzled over sand music in Chile.
The music, which only about 30 dunes in the entire world make, can be heard for miles and sound as loud as a low-flying airplane. Songs can last for as long as 15 minutes.
Now, scientists are getting closer to explaining the mystery. French scientists have discovered that grains of singing sand are different from ordinary ones. They're round, with a smooth coating of silicon, iron, and manganese. With this coating, even small amounts of sand can sing. But once it wears away, the sand loses its voice.
Scientists suspect that during sand avalanches, the cascading grains jostle each other and vibrate at a synchronized frequency. Soon the whole face of the dune vibrates in step like the membrane of a gigantic loudspeaker, producing a low, unearthly tune. And unearthly may be exactly right. Astronomers and geologists believe that the sands of Mars may be even more alive with the sound of music than the singing sands of Earth.
"No pessimist ever discovered the secret of the stars,
or sailed an uncharted land, or opened a new doorway for the human spirit."
--Helen Keller
Site of the Week:
To Infinity and Beyond!
In January 2004, President Bush told NASA to "explore space and extend a human presence across our solar system." The first goal: put humans back on the moon by 2020.
This week, NASA unveiled its plan to make President Bush's 2020 vision a reality--and put up a fabulous website designed to tell you how NASA's rocket scientists plan to get it done. Check out the site, including the video of four astronauts riding a rocket to the moon.
But don't be surprised if the technology looks old hat. NASA administrator Mike Griffin calls the plan "Apollo on steroids" and won't apologize for dusting off what worked more than three decades ago. Says Griffin, "The physics of atmospheric entry haven't changed recently."
Steve Sampson and Michael Himick
September 23, 2005
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