Learning More About Levitation

By Jeffrey Kluger

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Not quite yet: Jerry Lewis levitates in Visit to a Small Planet, 1960

Physics always seems to want to come out and play. Just when this most technical of sciences starts to become impossibly arcane, it goes goofy on you, as it did last year with the announcement that physicists at the University of California, Berkeley, had developed a tiny working model of an invisibility cloak. This week, the physics magic shop announced yet another wonder: levitation. Really.

The ability to levitate objects is not an entirely new thing in physics. Lower the temperature of certain metals and ceramics far enough (–459°F is a good number to shoot for), and they carry electromagnetic charges far more efficiently and for a far longer time than they otherwise would. When the metals are magnetized, they become so powerful that their ability to repel one another can actually allow them to lift heavy objects off the ground. That's the elegant principle behind some kinds of magnetically levitated (maglev) trains. (See the 50 best inventions of 2008.)

But maglev takes a load of hardware and a ton of power and is useless for small, simple kinds of engineering. The new breakthrough — achieved by a joint team of researchers from the National Institutes of Health (NIH) and Harvard University and published in a paper in the journal Nature — provides an alternative.

Everything in the universe — metals, gases, dogs, doughnuts — is made of materials with positive and negative charges. Opposite charges attract each other; identical charges repel each other. What prevents us from sticking to anything with an opposite charge is that all these forces have to be properly aligned before you can see them at work. "The materials are in motion, but sometimes the dance of the charges allows them to fall in step," says NIH physicist Adrian Parsegian, one of the authors of the paper. "When that happens, you get attractive forces."

What makes things trickier still is that not all attraction is equal. Some materials are drawn much more powerfully together than others — particularly on the nano (billionth of a meter) scale. And that difference can be exploited. In the Nature experiment, the research team began by placing a microscopically small sphere of gold on a glass surface. Gold and glass get along well enough and under the right circumstances will attract. But what they both like a whole lot more is a liquid called bromobenzene. When the researchers introduced a little bromobenzene to the other two materials, they both began drawing so much of it that the gold began to rise above the glass. In effect, it levitated on a thin bromobenzene film.

O.K., it's not Houdini. The microscopic pas de deux isn't even visible to the naked eye. Still, the phenomenon is not as uncommon as it might seem. Every time you ice skate, you experience something similar, as the shared properties of skate blade against ice create a thin film of water of a very particular thickness on which you, after a fashion, levitate. What makes the Harvard and NIH work so promising is its nano scale.

Increasingly, nanoengineers are working to develop medical devices, batteries, electrical switches and more made up of microscopic parts that float above one another on thin films of other materials. This increases efficiency, reduces friction and allows the hardware to be built to finer tolerances and tinier sizes. Design them small enough, and you can put them in microscopically tiny places machinery could never go before. "When you understand the forces you're manipulating," says Parsegian, "you can design efficiently at the nanometer scale."

By any measure, that's important stuff, though as with last year's invisibility cloak, it doesn't portend magical applications in the everyday world — and won't for a long, long time. "If you're looking for a free trip for your body on quantum levitation, you're not going to get it with this," says Parsegian. Even at its most fanciful, physics, it seems, can play around for only so long before it gets back to serious work.

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Stem Cells Undo Birth Defects

By Jocelyn Rice

Repairing damage: Neural stem cells, tagged green with a fluorescent dye, have been transplanted among the brain cells (red) of a mouse born with brain damage after its mother was given heroin during pregnancy. Transplants like this one seemed to effectively reverse the cellular, biochemical, and behavioral defects suffered by heroin-damaged mice. Credit: Joseph Yanai

By injecting stem cells directly into the brain, scientists have successfully reversed neural birth defects in mice whose mothers were given heroin during pregnancy. Even though most of the transplanted cells did not survive, they induced the brain's own cells to carry out extensive repairs.

Transplanted stem cells have previously shown promise in reversing brain damage caused by strokes, as well as by neurological diseases like Parkinson's, Alzheimer's, and Huntington's. But their use in treating birth defects is relatively new. In recent years, a handful of research teams have been developing stem-cell-based therapies for rodents with real or simulated birth defects in the brain.

Joseph Yanai, director of the Ross Laboratory for Studies in Neural Birth Defects at the Hebrew University-Hadassah Medical School, in Jerusalem, says that stem-cell therapies are ideal for treating birth defects where the mechanism of damage is multifaceted and poorly understood. "If you use neural stem cells," says Yanai, "they are your little doctors. They're looking for the defect, they're diagnosing it, and they're differentiating into what's needed to repair the defect. They are doing my job, in a way."

Yanai and his colleagues began with mice that had been exposed to heroin in the womb. These mice suffer from learning deficits; when placed in a tank of murky water, for instance, they take longer than normal mice to find their way back to a submerged platform. And in their hippocampus--an area of the brain associated with memory and navigation--critical biochemical pathways are disrupted, and fewer new cells are produced.

All of those problems are swiftly resolved when the researchers inject neural stem cells derived from embryonic mice into the brains of the heroin-exposed animals. When swimming, the treated mice caught up with their normal counterparts, and their cellular and biochemical deficits disappeared. Yanai announced these findings in 2007 and 2008.

Such dramatic results were surprising, considering that just a fraction of a percent of the transplanted stem cells survived inside the mice's brains. But they are consistent with an emerging consensus of how adult stem cells perform their many functions through so-called bystander or chaperone effects. Beyond simply generating replacements for damaged cells, stem cells seem to produce signals that spur other cells to carry out normal organ maintenance and initiate damage control.

"The chaperone effect is an important aspect of stem-cell biology that's simply been under-recognized," says Evan Snyder, who directs the Stem Cell Research Center at the Burnham Institute for Medical Research, in California, and whose research group coined the term in 2002. "That actually may be the low-hanging fruit in the stem-cell field--taking advantage of this, and not the cell-replacement aspect that we always thought would be the key to stem-cell biology in regenerative medicine."

Cesar Borlongan, a professor and vice chairman for research in the department of neurosurgery at the University of South Florida College of Medicine, uses a different model to explore the use of stem-cell treatment for brain-damaged infants. By deliberately restricting blood and oxygen flow to the brains of newborn rats, he and his colleagues simulate the effects of an infant stroke--a devastating event that causes untreatable brain injury in newborn humans.

Much like Yanai, Borlongan found that injecting stem cells into the compromised rats' brains reversed some of the behavioral deficits seen before treatment. For example, the treated rats could balance for longer time periods on a rotating rod.

To bring this kind of therapy closer to clinical tests in humans, Borlongan has experimented with administering the stem cells intravenously. Last July, in the online version of the Journal of Cerebral Blood Flow and Metabolism, he and his colleagues announced that transplanted stem cells produced the same result in rats regardless of whether they were given intravenously or injected directly into the brain.

Yanai has had similar success with intravenous administration in his heroin-exposure model, which he plans to announce at this year's annual meeting of the International Society for Stem Cell Research, in Barcelona.

The injected stem cells are able to migrate from the bloodstream to the brain for two reasons, says Borlongan. First, the injured brain sends out chemical signals that recruit the cells. And second, brain damage can compromise the blood-brain barrier, which normally regulates which substances can cross the threshold into the brain.

Not everyone is enthusiastic about the intravenous approach, however. Darwin Prockop, director of the Institute for Regenerative Medicine at Texas A&M Health Science Center College of Medicine, cautions that the injected cells can lodge in other organs--particularly the lungs--causing unwanted and even deadly side effects. And according to Evan Snyder, it may be unnecessary to go in through the bloodstream; his group has not seen any major risks associated with direct brain injection, a route that he considers to be clinically feasible in humans.

But all of these therapies involve introducing foreign cells into the body, and therefore, run the risk of provoking a potentially dangerous immune response. In most studies to date, the treated rodents are dosed with powerful immunosuppressants. Yanai is currently exploring personalized treatments to circumvent this issue: cells are extracted from the animal to be treated, coaxed to return to a stem-cell-like state, and then transplanted. Because they originate in the treated animal, the cells are recognized as "self" and ignored by the immune system.

Recently, Borlongan has found that immunosuppressants are unnecessary in the infant-stroke model. Because he treats the rodents at a very young age, their still-immature immune systems appear relatively unfazed by the transplanted stem cells. Borlongan notes that a low-level immune response may actually be useful: by cutting down on the number of cells that survive in the long term, it may reduce the chance that injected cells will reproduce uncontrollably and form tumors.

Nonetheless, according to Prockop, the risk of tumors is a serious concern with any stem-cell-based therapy. And while he is optimistic about the future of cell therapies for treating a wide variety of diseases, he urges caution and conscience when considering severe birth defects. "The big danger is that you can take a child who may be doomed to die in a few years, and make that child a lifelong invalid who needs continuing nursing care," he says. "So the prospects, if you think about them hard, are extremely worrisome. If you don't get a complete cure, you may be causing more harm than good."

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Love spray being developed by scientists

By Richard Alleyne, Science Correspondent

It may not be the most romantic gesture but scientists are developing drugs that can boost that most human of emotions.

They are studying the brain chemistry responsible for the complex feelings that draw us to a particular member of the opposite sex and help keep us monogamous.

Animal testing is beginning to shed light on the complex neural and genetic components of love in the same way they have led to pharmaceutical therapies for anxiety, phobias and post-traumatic stress disorders.

The behavioural scientist Professor Larry Young, of Emory University, Georgia, writing in the journal Nature, said: "For one thing, drugs that manipulate brain systems at whim to enhance or diminish our love for another may not be far away."

Experiments have already shown a nasal squirt of the hormone oxytocin enhances trust and tunes people into others' emotions.

Websites are marketing products such as Enhanced Liquid Trust, a cologne-like mixture of oxytocin and chemical scents called pheromones "designed to boost the dating and relationship area of your life".

Prof Young said: "Although such products are unlikely to do anything other than boost users' confidence, studies are under way in Australia to determine whether an oxytocin spray might aid traditional marital therapy."

Prof Young said: "The hormone interacts with the reward and reinforcement system driven by the neuro-transmitter dopamine – the same circuitry that drugs such as nicotine, cocaine and heroine act on in humans to produce euphoria and addiction.

"Dopamine-related reward regions of the human brain are active in mothers viewing images of their child. Similar activation patterns are seen in people looking at photographs of their lovers."

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