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Mystery Solved: The Source Of Pain In "Phantom" Limbs


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Mystery Solved: The Source of Pain in "Phantom" Limbs

One of the great medical mysteries is the source of phantom-limb syndrome. Doctors have been puzzled for centuries by patients who, after losing an arm or a leg, continue to feel sensation--and even excruciating pain--in the lost limb. For some time, neuroscientists have suspected that the pain was a side effect of the brain's attempts to reorganize itself following a major disruption in sensory input. But researchers at Vanderbilt University in Nashville report the surprising discovery that this reorganization is causing significant growth of new brain cells in amputees.

Their finding, reported in the Proceedings of the National Academy of Sciences, builds on the discovery in the past year that adult mammals can grow new brain cells, an activity that scientists once thought ceased after childhood. If this neuronal growth can be harnessed, cures may be possible not only for phantom-limb pain but for severed spinal cords.

The Vanderbilt researchers based their studies on monkeys that had had an arm amputated. Knowing that the nerves of each body part connect to a specific region in the brain, the researchers injected tracer elements into the animals' chins. When they examined the brains, they found the tracer in brain regions connected to the hand and arm as well as to the face. There was clear evidence, they say, that neurons from the face area of the brain had grown extensive new connections to the hand area. This, they say, may explain why people who lose an arm often report that when they are touched on the face it feels as if the sensation comes from the missing limb.Edited by Catherine ArnstReturn to top

A Thumb's-Up for St. John's Wort--with Caveats

Herbal remedy St. John's Wort has received an official seal of approval--sort of. In a new set of guidelines for the treatment of depression published on May 2, the American College of Physicians-American Society of Internal Medicine (ACP-ASIM) says St. John's wort may be effective in treating mild depression over the short term.

The perennial herb is frequently taken in Europe for anxiety and depression, but U.S. doctors have been largely dismissive, on the grounds that too little is known about its effectiveness. However, several European studies indicate that it may alleviate depression, including a large German study reported last December in the British Medical Journal. The ACP-ASIM, which publishes treatment guidelines for a wide range of ailments, continues to recommend traditional antidepressants such as tricyclics and selective serotonin reuptake inhibitors, but it does acknowledge that St. John's wort is more effective than a placebo in treating depression.

The recommendation comes with plenty of caveats. The group notes that there is no federal regulation of the herb, no good studies compare it to other antidepressants, and it can interfere with blood-thinning medications. "We'll have to see more evidence-based studies," says Dr. Herbert H. Waxman, head of education at ACP-ASIM.Edited by Catherine ArnstReturn to top

Nuclear Waste: It's in the Timing

Nuclear plants typically stow waste in steel drums that are encased in concrete. But no one has done tests to find out just how much wear and tear the concrete can withstand before it erodes enough to create a potential hazard because of leaks. So Massachusetts Institute of Technology has figured out a way to compress 300 years' worth of stress into a year in an effort to develop safer containers.

Led by Franz-Josef Ulm, a team of civil engineers has developed a process that accelerates the aging process of concrete. The researchers bathe the material in a highly concentrated solution of ammonium nitrate that leaches the calcium out of the concrete--just as water would in a much slower process--until it is as ridden with holes as Swiss cheese.

The engineers then subject the weathered concrete to increased pressure and other stresses and measure how it responds. The team is currently using the data to develop a computer model that can predict, based on specific environmental conditions such as temperature, humidity, and water intrusion, what the concrete will do on timescales of 300 to 1,000 years. "This knowledge will help us intervene before a worst-case scenario arises," says Ulm. He also plans to use it to develop concrete mixes that are more durable.By Ellen Licking; Edited by Catherine ArnstReturn to top


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