Nerves, Muscle Regenerated With Sodium Ions

Nerves, Muscle Regenerated With Sodium Ions

  12:35:00 AM    Science Lover

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Sodium gets a bad rap for contributing to hypertension and cardiovascular disease. Now biologists at Tufts University's School of Arts and Sciences have discovered that sodium also plays a key role in initiating a regenerative response after severe injury. The Tufts scientists have found a way to regenerate injured spinal cord and muscle by using small molecule drugs to trigger an influx of sodium ions into injured cells.

Tufts biologists have regenerated spinal cord and 
muscle by using a "pharmaceutical cocktail" to 
trigger an influx of sodium ions into injured cells. The 
treatment method is most directly applicable to spinal
cord repair and limb loss, which are significant problems
worldwide, but the proof-of-principle may apply to many 
complex organs and tissues. The Tufts team found that a 
localized increase in sodium ions was necessary for young 
tadpoles to regenerate their tails -- complex appendages
containing spinal cord, muscle and other tissue. Like 
human beings, who regenerate fingertips only as children, 
tadpoles lose the ability to regenerate their tail with 
age. The Tufts biologists showed that such "refractory" 
tadpoles whose tails had been removed could be induced 
to make a perfect new tail by only an hour of treatment. 
The tadpole on the left, which received the "cocktail" to 
trigger an influx of sodium ions, grew a perfectly formed tail. 
The control tadpole on the right did not regenerate. This 
approach breaks new ground in biomedicine because it 
requires no gene therapy; can be effectively administered
for some time after an injury has occurred; and is bioelectric, 
rather than chemically based. (Credit: Ai-Sun Tseng and 
Michael Levin-Tufts University)

The approach breaks new ground in the field of biomedicine because it requires no gene therapy; can be administered after an injury has occurred and even after the wound has healed over; and is bioelectric, rather than chemically based.

In a paper appearing as the cover story of the September 29, 2010, issue of the Journal of Neuroscience, the Tufts team reported that a localized increase in sodium ions was necessary for young Xenopus laevis tadpoles to regenerate their tails - complex appendages containing spinal cord, muscle and other tissue.

Like human beings, who regenerate fingertips only as children, these tadpoles lose the ability to regenerate their tail with age. Most remarkably, it was shown that such "refractory" tadpoles whose tails had been removed could be induced to make a perfect new tail by only an hour of treatment with a specific drug cocktail.

The findings have tremendous implications for treating wounds sustained in war as well as accidental injuries. The treatment method used is most directly applicable to spinal cord repair and limb loss, which are highly significant medical problems world-wide. It also demonstrates a proof-of-principle that may be applicable to many complex organs and tissues.

"We have significantly extended the effective treatment window, demonstrating that even after scar-like wound covering begins to form, control of physiological signals can still induce regeneration. Artificially causing an influx of sodium for just one hour can overcome a variety of problems, such as the decline in regenerative ability that comes with age and the effect of regeneration-blocking drugs," said Tufts Professor of Biology Michael Levin, Ph.D., corresponding author on the paper and director of the Center for Regenerative and Developmental Biology at Tufts. Co-authors were Research Associate Ai-Sun Tseng, Postdoctoral Associate Wendy S. Beane, Research Associate Joan M. Lemire, and Alessio Masi, a former post-doctoral associate in Levin's laboratory.

The transport of ions in and out of cells is regulated by electronic security doors, or gates, that let in specific ions under certain circumstances. A role for sodium current in tissue regeneration had been proposed in the past, but this is the first time the molecular-genetic basis of the ion flow has been identified, and a specific drug-based treatment demonstrated. Until now, advances in this model system had involved administering therapies before the injury was sustained.

"This is a novel, biomedically-relevant approach to inducing regeneration of a complex appendage," noted Levin.

The Tufts research established a novel role in regeneration for the sodium channel Nav1.2, a crucial component of nerve and cardiac function. It showed that local, early increase in intracellular sodium is required for initiating regeneration following Xenopus tail amputation, while molecular and pharmacological inhibition of sodium transport causes regenerative failure. The new treatment induced regeneration only of correctly-sized and patterned tail structures and did not generate ectopic or other abnormal growth.

"The ability to restore regeneration using a temporally-controllable pharmacological approach not requiring gene therapy is extremely exciting," said the researchers.

Of critical importance, they said, was the discovery that the tail could be induced to regenerate as late as 18 hours after amputation, revealing that tissues normally fated for regenerative failure still maintain their intrinsic characteristics and can be programmed to reactivate regeneration.

Amphibians such as frogs can restore organs lost during development, including the lens and tail. The frog tail is a good model for human regeneration because it repairs injury in the same way that people do: each tissue makes more of itself. (In contrast, regeneration in some other animals occurs through transdifferentiation (one cell type turns into another cell type) or adult stem cell differentiation. Furthermore, though small, the Xenopus larval tail is complex, with muscle, spinal cord, peripheral nerves and vasculature cells.

The National Institutes of Health, National Highway Traffic Safety Administration, Department of Defense and Defense Advanced Research Projects Agency funded the work.

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Genetic "Light Switches" Control Muscle Movement The technique will improve research on neuromuscular disorders and could one day help paralyzed patients.

Genetic "Light Switches" Control Muscle Movement The technique will improve research on neuromuscular disorders and could one day help paralyzed patients.

  9:57:00 AM    Science Lover

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Using light-sensitive proteins from a single-celled alga and a tiny LED "cuff" placed on a nerve, researchers have triggered the leg muscles of mice to contract in response to millisecond pulses of light.

Light movement: This image shows a cross-section of a mouse sciatic nerve genetically engineered to produce a light-sensitive protein (shown in green). Stanford researchers used this protein to trigger muscle movements in the animal’s leg.
Credit: Nature

The study, published in the journal Nature Medicine, marks the first use of the nascent technology known as optogenetics to control muscle movements. Developed by study coauthor Karl Deisseroth, an associate professor of bioengineering and of psychiatry and behavioral science at Stanford University, optogenetics makes it possible to stimulate neurons with light by inserting the gene for a protein called channelrhodopsin-2, from a green alga. When a modified neuron is exposed to blue light, the protein initiates electrical activity inside the cell that then spreads from neuron to neuron. By controlling which neurons make the protein, as well as which cells are exposed to light, scientists can control neural activity in living animals with unprecedented precision. The paper's other senior author, Scott Delp, a professor of bioengineering, mechanical engineering, and orthopedic surgery at Stanford, says that the optical control method provides "fantastic advantages over electrical stimulation" for his study of muscles and the biomechanics of human movement.

Members of Deisseroth's lab had engineered mice to produce channelrhodopsin-2 in both the central and the peripheral nervous systems. Michael Llewellyn, a former graduate student in Delp's lab, developed a tiny, implantable LED cuff to apply light to the nerve evenly. He placed the cuff on the sciatic nerves of anesthetized mice and triggered millisecond pulses of light. This caused the leg muscles of the mice to contract. When Llewellyn compared the muscle contractions stimulated by light to those generated using a similar electrical cuff, he found that the light-triggered contractions were much more similar to normal muscle activity.

Muscles are made up of two different fibers: small, slow, fatigue-resistant fibers that are typically used for tasks that require fine motor control over longer periods, and larger, faster fibers that can produce higher forces but are more fatigue-prone. In the body, the small, slow fibers are activated first, with the large, fast fibers reserved for quick bursts of power or speed. When muscles are stimulated with electrical pulses, the fast fibers activate first. With the optogenetic switch, however, the fibers were recruited in the normal, physiological order: slow fibers first, fast fibers second. By altering the intensity of the light, Llewellyn found that he could even trigger only the slow fibers--a feat not possible with electrical stimulation.

In the near term, Delp says, the technology will improve the studies that his lab and others do on muscle activity in animal models of stroke, palsies, ALS, and other neuromuscular disorders. He also hopes that in time--a long time, he concedes--such optical switches could be used to help patients with physical disabilities caused by nerve damage such as stroke, spinal cord injury, or cerebral palsy. One possibility, he says, would be to use optical stimulation in place of functional electrical stimulation (FES), in which electrical current is applied to specific nerves or muscles to trigger muscle contractions. The U.S. Food and Drug Administration has already approved FES devices that can restore hand function and bladder control to some paralyzed people. However, FES can quickly lead to muscle fatigue. Delp hopes that, particularly with grasping functions, using optical stimulation might result in better fatigue resistance and perhaps finer muscle control.

"This is a brilliant study, really beautiful science," says Robert Kirsch, a bioengineer at Case Western Reserve University and associate director of the Cleveland Functional Electrical Stimulation Center; he was not involved in the research. "I think there are many [clinical implications]," he says, although, like Delp and Llewellyn, he notes that many high hurdles must be cleared--not least of which is developing a safe, effective way to deliver the channelrhodopsin-2 gene to nerve cells in humans. Otherwise, Kirsch says, "my one objection would be their implication that they've solved the fatigue problem with FES. I'm pretty sure that hasn't happened." Instead, Kirsch believes that most of the fatigue seen in FES patients is due to muscle atrophy and weakness that develop in the chronically paralyzed.

C.J. Heckman, a professor of physiology at Northwestern University's Feinberg School of Medicine, agrees: "It is true that a lot of the fatigue seen in FES patients is due to chronic muscle atrophy." But, he says, "if you could stimulate the muscles in the correct recruitment order repeatedly over time, you could potentially recover a lot of muscle function." This could help paralysis patients preserve their slow muscle fibers, "which would be a huge deal," Heckman says. This is because those fibers do a huge percentage of the work muscles do--everything from maintaining posture to typing on a keyboard.

Delp also thinks that stimulation-based exercise could be an important application for optical muscle control, as could helping wheelchair-bound people stand to reach for books or plates in a cabinet. "I'm not super-high on controlling locomotion"--that is, walking--"with either electrical or optical stimulation, though," Delp says. "It's an incredibly complicated command-and-control scheme that's really hard to coordinate."

In the meantime, Delp and Llewellyn have begun an effort to use a different light-sensitive protein, halorhodopsin, to inhibit motor nerves in mice, with the idea of treating or even curing muscle spasticity, often a serious side effect to brain or spinal injury. Current treatments are far from ideal; doctors may inject botulinum toxin into the affected muscles every few months to paralyze them, use oral medications such as Valium that affect the whole body instead of just the affected muscle, or, in the most severe cases, cut the nerves or tendons of the spastic muscle--a permanent treatment that leaves the patient with no control over that muscle. Delp hopes that genetically engineering the nerves with halorhodopsin might enable people to use light to reversibly relax muscles affected with spasticity.

"I think that's a great idea for treating spasticity," says Jerry Silver, a neuroscientist at Case Western. There may be some difficulties along the way, though, he says. Working with Case colleagues, Silver has started a company called LucCell to develop clinical applications of optogenetics. In one company project, scientists are trying to use halorhodopsin and other inhibitory opsins in animal models to turn off the muscle that controls the bladder sphincter; their ultimate goal is to restore bladder function to paralyzed people. Though they have seen some physiological changes in how the sphincter muscle behaves, they haven't been able to get it to relax enough. "We're learning it's easier to turn things on than turn things off," he says. Still, the team is persisting, looking for better ways to deliver the gene to nerve cells and for ways to increase production of the protein on the cell's surfaces.

"It all depends on the ability to get the transgene in the right place in the person's genome without causing problems," agrees Llewellyn. "It's the main obstacle."

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Single Gene Regulates Motor Neurons in Spinal Cord

Single Gene Regulates Motor Neurons in Spinal Cord

  10:49:00 AM    Science Lover

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In a surprising and unexpected discovery, scientists at NYU Langone Medical Center have found that a single type of gene acts as a master organizer of motor neurons in the spinal cord. The finding, published in the September 9, 2010 issue of Neuron, could help scientists develop new treatments for diseases such as Lou Gehrig's disease or spinal cord injury.

This image shows the pattern of motor neuron 
innervation in the body of a mouse embryo. 
(Credit: Image courtesy of Heekyung Jung)

The "master organizer" is a member of the Hox family of genes, best known for controlling the overall pattern of body development. By orchestrating a cascade of gene expression in the early embryo, Hox genes allow for the creation of an animal's overall structure and body part orientation. Scientists first discovered the genes in fruit flies but they have since detected Hox activity in mammals. Humans harbor 39 such genes and 21 have been identified as coordinating motor neurons in the spinal cord.

"We knew that there were 21 Hox genes that determine how connections are made between motor neurons in the spinal cord and muscles in the limbs," says Jeremy S. Dasen, PhD, an associate professor in the Departments of Physiology and Neuroscience at NYU Langone Medical Center and a Howard Hughes Medical Institute Early Career Scientist. "But what was surprising to us in this study was that a single Hox gene acts as a global organizer of motor neurons and their connections. The next step will be to see how Hoxc9 in motor neurons affect motor behaviors such as walking and breathing."

In mammals, many hundreds of motor neurons are needed to control the variety of muscle cells used to coordinate movement. Proper function depends on each of these neurons in the embryo finding its way from the spinal cord to the group of muscles that it is equipped to control. Dr. Dasen and his colleagues have been working to discover the blueprint for this motor neuron diversity.

For this study, scientists studied mice with a mutation in Hoxc9 gene. They analyzed the molecular markers that distinguished between motor neurons in the limb and thoracic area and discovered mutation of Hoxc9 transformed the thoracic motor neurons into limb motor neurons. In a series of biochemical experiments they further showed that Hoxc9 orchestrates gene expression in motor neurons by repressing the Hox genes dedicated to limb coordination.

"What we are trying to understand is how the nervous system is wired to control movements such as breathing and walking and see how genetic programs can further control these circuits in terms of exploring this paradigm as a way at looking at the vital circuits of the body," adds Dr. Dasen.

Co-authors of the study include Heekyung Jung, Julie Lacombe, and Jonathan Grinstein of NYU Langone Medical Center. The research was done in collaboration with researchers at Columbia University Medical Center, Massachusetts Institute of Technology and Memorial Sloan Kettering Cancer Center.

The study was supported by a grant from the National Institutes of Health in Bethesda, Maryland.

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Spinal Injury: Nerve Connections Regenerated

Spinal Injury: Nerve Connections Regenerated

  9:50:00 AM    Science Lover

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Researchers for the first time have induced robust regeneration of nerve connections that control voluntary movement after spinal cord injury, showing the potential for new therapeutic approaches to paralysis and other motor function impairments.

New research points the way toward a 
potential therapy to induce 
regeneration of nerve connections 
following spinal cord injury. 
(Credit: iStockphoto/Feng Yu)

In a study on rodents, the UC Irvine, UC San Diego and Harvard University team achieved this breakthrough by turning back the developmental clock in a molecular pathway critical for the growth of corticospinal tract nerve connections.

They did this by deleting an enzyme called PTEN (a phosphatase and tensin homolog), which controls a molecular pathway called mTOR that is a key regulator of cell growth. PTEN activity is low early during development, allowing cell proliferation. PTEN then turns on when growth is completed, inhibiting mTOR and precluding any ability to regenerate.

Trying to find a way to restore early-developmental-stage cell growth in injured tissue, Zhigang He, a senior neurology researcher at Children's Hospital Boston and Harvard Medical School, first showed in a 2008 study that blocking PTEN in mice enabled the regeneration of connections from the eye to the brain after optic nerve damage.

He then partnered with Oswald Steward of UCI and Binhai Zheng of UCSD to see if the same approach could promote nerve regeneration in injured spinal cord sites. Results of their study appear online in Nature Neuroscience.

"Until now, such robust nerve regeneration has been impossible in the spinal cord," said Steward, anatomy & neurobiology professor and director of the Reeve-Irvine Research Center at UCI. "Paralysis and loss of function from spinal cord injury has been considered untreatable, but our discovery points the way toward a potential therapy to induce regeneration of nerve connections following spinal cord injury in people."

According to Christopher & Dana Reeve Foundation data, about 2 percent of Americans have some form of paralysis resulting from spinal cord injury, which is due primarily to the interruption of connections between the brain and spinal cord.

An injury the size of a grape can lead to complete loss of function below the level of injury. For example, an injury to the neck can cause paralysis of arms and legs, loss of ability to feel below the shoulders, inability to control the bladder and bowel, loss of sexual function, and secondary health risks including susceptibility to urinary tract infections, pressure sores and blood clots due to an inability to move the legs.

"These devastating consequences occur even though the spinal cord below the level of injury is intact," Steward noted. "All these lost functions could be restored if we could find a way to regenerate the connections that were damaged."

He and his colleagues are now studying whether the PTEN-deletion treatment leads to actual restoration of motor function in mice with spinal cord injury. Further research will explore the optimal timeframe and drug-delivery system for the therapy.

Kai Liu, Yi Lu, Andrea Tedeschi, Kevin Kyungsuk Park, Duo Jin, Bin Cai, Bengang Xu and Lauren Connolly of Harvard; Jae Lee of UCSD; and Rafer Willenberg and Ilse Sears-Kraxberger of UCI also contributed to the study, which was supported by the Wings for Life Spinal Cord Research Foundation, the Craig H. Neilsen Foundation, the International Spinal Research Trust, the National Institute of Neurological Disorders & Stroke, and a private contribution to the Reeve-Irvine Research Center.

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Brainstem, Spinal Cord Images Hidden in Michelangelo’s Sistine Chapel Fresco

Brainstem, Spinal Cord Images Hidden in Michelangelo’s Sistine Chapel Fresco

  10:50:00 AM    Science Lover

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Michelangelo, the 16th century master painter and accomplished anatomist, appears to have hidden an image of the brainstem and spinal cord in a depiction of God in the Sistine Chapel's ceiling, a new study by Johns Hopkins researchers reports. These findings by a neurosurgeon and a medical illustrator, published in the May Neurosurgery, may explain long controversial and unusual features of one of the frescoes' figures.

The odd depiction of God's neck in "Separation 
of Light From Darkness" (A) bears a striking 
resemblance to a brainstem, seen in tissue from 
a cadaver (B) and outlined in the painting (C). 
(Credit: Image courtesy of Neurosurgery.)

Michelangelo is known to have dissected numerous cadavers starting in his teenage years, these anatomic studies aiding him in creating extremely accurate depictions of the human figure in his sculptures and paintings, notably the statue of David in Florence and paintings of God and other figures from the Book of Genesis in the Vatican's Sistine Chapel in Rome.

Although the vast majority of subjects in this painting are considered anatomically correct, art historians and scholars have long debated the meaning of some anatomical peculiarities seen on God's neck in the part of the painting known as Separation of Light From Darkness. In this image, the neck appears lumpy, and God's beard awkwardly curls upward around his jaw.

"Michelangelo definitely knew how to depict necks -- he knew anatomy so well," says Rafael Tamargo, M.D., a professor in the Department of Neurosurgery at the Johns Hopkins University School of Medicine. "That's why it was such a mystery why this particular neck looked so odd."

To investigate, Tamargo enlisted the help of his Hopkins colleague Ian Suk, B.Sc., B.M.C., a medical illustrator and associate professor in the Department of Neurosurgery. Together, the researchers realized that the unusual features in the neck strongly resemble a brainstem, the portion of tissue at the base of the brain that connects to the spinal cord.

"It's an unusual view of the brainstem, from the bottom up. Most people wouldn't recognize it unless they had extensively studied neuroanatomy," says Suk.

Suk adds that the strategically placed brainstem might also explain another unusual feature of the painting. In this same image, God is depicted in a red robe with an odd tubular structure depicted in the chest. Although God wears the same red robe in other images in the fresco, this tubular structure is absent elsewhere. The structure has the right placement, shape, and size to be a spinal cord, say the researchers, suggesting another piece of hidden anatomy in the artwork.

Tamargo and Suk explain that, if their proposition is correct, it wouldn't be the first time that such concealed anatomical depictions have been proposed to exist in the Sistine Chapel's ceiling. In 1990, Frank Lynn Meshberger, an obstetrician based in Indiana, published a paper suggesting that the shroud surrounding the image known as the Creation of Adam strongly resembles an anatomically correct brain.

"It looks like the central nervous system may have been too good a motif to use only once," Tamargo says.

The two researchers plan to continue searching for other hidden pieces of anatomy elsewhere in the Sistine Chapel painting.

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Spinal Cord Regeneration Enabled By Stabilizing, Improving Delivery Of Scar-degrading Enzyme

Spinal Cord Regeneration Enabled By Stabilizing, Improving Delivery Of Scar-degrading Enzyme

  9:18:00 PM    Science Lover

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Researchers have developed an improved version of an enzyme that degrades the dense scar tissue that forms when the central nervous system is damaged. By digesting the tissue that blocks re-growth of damaged nerves, the improved enzyme -- and new system for delivering it -- could facilitate recovery from serious central nervous system injuries.

Image showing the extent of new nerves (green) that regenerated after treatment with the enzyme. (Credit: Image courtesy of Ravi Bellamkonda)

 
The enzyme, chrondroitinase ABC (chABC), must be supplied to the damaged area for at least two weeks following injury to fully degrade scar tissue. But the enzyme functions poorly at body temperature and must therefore be repeatedly injected or infused into the body.

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Chronic Spinal Cord Injury

Chronic Spinal Cord Injury

  11:45:00 AM    Science Lover

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Scientists at the University of California, San Diego School of Medicine report that regeneration of central nervous system axons can be achieved in rats even when treatment delayed is more than a year after the original spinal cord injury.

Mark Tuszynski, MD, PhD. (Credit: Image courtesy of University of California - San Diego)

"The good news is that when axons have been cut due to spinal cord injury, they can be coaxed to regenerate if a combination of treatments is applied," said lead author Mark Tuszynski, MD, PhD, professor of neurosciences and director of the Center for Neural Repair at UC San Diego, and neurologist at the Veterans Affairs San Diego Health System. "The chronically injured axon is not dead."

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Face Recognition: The Eyes Have It

Face Recognition: The Eyes Have It

  10:15:00 PM    Science Lover

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Our brain extracts important information for face recognition principally from the eyes.
(Credit: iStockphoto/Cristian Ardelean)

Our brain extracts important information for face recognition principally from the eyes, and secondly from the mouth and nose, according to a new study from a researcher at the University of Barcelona. This result was obtained by analyzing several hundred face images in a way similar to that of the brain.

Imagine a photograph showing your friend's face. Although you might think that every single detail in his face matters to recognize him, numerous experiments have shown that the brain prefers a rather coarse resolution instead, irrespective of the distance at which a face is seen. Until now, the reason for this was unclear. By analyzing 868 male and 868 female face images, the new study may explain why.

The results indicate that the most useful information is obtained from the images if their size is around 30 x 30 pixels. Moreover, images of eyes give the least "noisy" result (meaning that they convey more reliable information to the brain compared to images of the mouth and nose), suggesting that face recognition mechanisms in the brain are specialized to the eyes.

This work complements a previously conducted study published in PLoS One, which found that artificial face recognition systems have the best recognition performance when processing rather small face images – meaning that machines should do it just like humans.
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Journal reference:

1. Keil et al. "I Look in Your Eyes, Honey": Internal Face Features Induce Spatial Frequency Preference for Human Face Processing. PLoS Computational Biology, 2009; 5 (3): e1000329 DOI: 10.1371/journal.pcbi.1000329

Adapted from materials provided by Public Library of Science, via EurekAlert!, a service of AAAS.

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