20091104-5

Unlike humans, zebrafish are able to regenerate amputated appendage
Credit: Courtesy of the Salk Institute

 

ScienceDaily (Nov. 2, 2009) – The search for the holy grail of regenerative medicine — the ability to “grow back” a perfect body part when one is lost to injury or disease — has been under way for years, yet the steps involved in this seemingly magic process are still poorly understood.

Now researchers at the Salk Institute for Biological Studies have identified an essential cellular pathway in zebrafish that paves the way for limb regeneration by unlocking gene expression patterns last seen during embryonic development. They found that a process known as histone demethylation switches cells at the amputation site from an inactive to an active state, which turns on the genes required to build a copy of the lost limb.

“This is the first real molecular insight into what is happening during limb regeneration,” says first author Scott Stewart, Ph.D., a postdoctoral researcher in the lab of Juan Carlos Izpisúa Belmonte, Ph.D., who led the Salk team. “Until now, how amputation is translated into gene activation has been like magic. Finally we have a handle on a process we can actually follow.”

Their findings, which will be published in a forthcoming issue of Proceedings of the National Academy of Sciences, U.S.A., help to explain how epimorphic regeneration — the regrowing of morphologically and functionally perfect copies of amputated limbs — is controlled, an important step toward understanding why certain animals can do it and we cannot.

“Our experiments show that normal development and limb regeneration are controlled by similar mechanisms,” explains Izpisúa Belmonte, a professor in the Gene Expression Laboratory. “This finding will help us to ask more specific questions about mammalian limb regeneration: Are the same genes involved when we amputate a mammalian limb? If not, what would happen if we turned them on? And if we can affect these methylation marks in an amputated limb, what effect would that have?”

The Belmonte lab uses zebrafish, a small fish from the minnow family, to study limb regeneration. “If you amputate the tail of the zebrafish, it regenerates in about a week, seemingly with no effort and leaving no scar,” explains Stewart. “What’s more, it regenerates a perfect copy and — like growing grass — it will do this over and over again.”

Since regeneration recapitulates in broad strokes embryonic development, during which a complex multi-cellular organism develops from a handful of embryonic stem cells, the researchers began by comparing gene expression patterns between the two processes. During development, genes within specific cell types are turned on and off to trigger the necessary expression patterns that create a whole animal. Once their job is done, they lie silently till they are turned on once again following amputation.

Based on these similarities, Stewart reasoned that genes involved in regeneration may share silencing mechanisms with the ones active in embryonic stem cells. Embryonic stem cells are maintained in a ready-to-go state, “poised” for action to become whatever cell type is needed. The key to this “poised” state are histones, DNA packaging proteins that are also used as carriers for chemical modifications, such as methylation and acetylation. These chemical marks serve as “on” and “off” switches for specific genes.

Stewart discovered that the histone modifications that poise embryonic stem cell-specific genes for activation are also found on the histones near genes involved in regeneration, putting them into a ready-to-go state. “This suggests that two different gene expression programs may exist; one for normal cellular activity and one for regeneration,” explains Stewart. To test this hypothesis, the team looked at the histone marks during regeneration. As suspected, they saw a reduction in “off” switches and an increase in “on” switches in regenerating tissue, tipping the balance toward gene expression.

Delving deeper, the researchers found that enzymes that remove the “off” mark, so-called demethylases, are present in high levels in regenerating tissue. One enzyme in particular, called Kdm6b.1, is found exclusively in cells that are undergoing the regeneration process. Without Kdm6b.1, zebrafish failed to regenerate amputated fins, meaning removal of the “off” mark is a prerequisite for fin regeneration.

In the long term, the Salk researchers hope that these findings will help them understand whether we can affect the outcome of mammalian limb regeneration. In the more immediate future, the team plans to use global approaches to identify all the targets of Kdm6b.1 during regeneration, and to find out what gives the signal to turn these genes off when regeneration is complete.

In addition to Stewart and Izpisúa Belmonte, Zhi-Yang Tsun, also contributed to the study.

The study was funded in part by the California Institute for Regenerative Medicine, the Fundacion Cellex, the G. Harold and Leila Y. Mathers Charitable Foundation, the Ipsen Foundation, and the National Institutes of Health.

Adapted from materials provided by Salk Institute,

ScienceDaily.com, October/November 2009  –  Biologists long have marveled at the ability of some animals to re-grow lost body parts. Newts, for example, can lose a leg and grow a new one identical to the original. Zebrafish can re-grow fins.

These animals and others also can repair damaged heart tissue and injured structures in the eye. In contrast, humans have only rudimentary regenerative abilities, so scientists hoping eventually to develop ways of repairing or replacing damaged body parts are keenly interested in understanding in detail how the process of regeneration works.

Using zebrafish as a model, researchers at the University of Michigan have found that some of the same genes underlie the process in different types of tissues. Genes involved in fin regeneration and heart repair are also required for rebuilding damaged light receptors in the eye, they found, suggesting that a common molecular mechanism guides the process, no matter what body part is damaged.

Zhao Qin a graduate student in the department of Molecular, Cellular and Developmental Biology will present the research Oct. 19 at the annual meeting of the Society for Neuroscience in Chicago. Her coauthors on the paper, which also was published in the Proceedings of the National Academy of Sciences, are professor and chair Pamela Raymond and research laboratory specialist Linda Barthel.

The researchers briefly exposed zebrafish to intense light, which destroys the light receptors in their eyes, just as staring into the sun harms human eyes. But unlike humans, who remain blinded if the damage is severe enough, zebrafish repair the damage with new nerve cells (neurons).

Where do those new cells come from? The U-M researchers suspected they develop from cells in the retina called Müller glia, known to have the ability to give rise to nerve cells, and in previous work another graduate student in Raymond’s lab confirmed the suspicion.

In the current work, Qin wanted to find what prompts Müller glia to start the regeneration process. To get at the question, she looked at patterns of gene expression in Müller glia from damaged, regenerating zebrafish retinas and from undamaged zebrafish retinas to see which genes are expressed differently in damaged and undamaged retinas.

“Of course I found a lot of genes—a total of 953,” Qin said, “but two were of particular interest.” The two genes, hspd1 and mps1, had been found in other studies to be required for fin and heart regeneration in zebrafish, and Qin’s work showed that they also were switched on in Müller glia from damaged zebrafish retinas.

“This suggests,” Raymond said, “that, although we don’t fully understand it yet, there might be a bigger molecular program, involving not just these two genes but a number of cooperating genes that are required for injury-triggered regeneration.”

The researchers received funding from the National Institutes of Health.

20091104-4

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

 

ScienceDaily (Nov. 2, 2009) – 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.

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.

In a paper published November 2 in the early edition of the journal Proceedings of the National Academy of Sciences, researchers describe how they eliminated the thermal sensitivity of chABC and developed a delivery system that allowed the enzyme to be active for weeks without implanted catheters and pumps. This work was supported by the National Institutes of Health.

“This research has made digesting scar clinically viable by obviating the need for continuous injection of chABC by thermally stabilizing the enzyme and harnessing bioengineered drug delivery systems,” said the paper’s lead author Ravi Bellamkonda, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

At physiological body temperature, chABC enzyme loses half of its enzymatic activity within one hour and their remaining functionality within three to five days. To thermostabilize the enzymes, Bellamkonda, Emory University cell biology associate professor Robert McKeon and Georgia Tech graduate student Hyun-Jung Lee mixed the enzyme with the sugar trehalose. The result — the enzyme’s activity was stabilized at internal body temperature for up to four weeks during in vitro tests.

The researchers then used a lipid microtube-hydrogel scaffold system to deliver the thermostabilized enzymes into animals via a single injection. The scaffold provided sustained delivery of the enzyme for two weeks, with the microtubes enabling slow release and the hydrogel localizing the tubes to the lesion site. This delivery system also allowed the enzyme to diffuse deeper into the tissue than did catheter delivery.

In animal studies, the enzyme’s ability to digest the scar was retained for two weeks post-injury and scar remained significantly degraded at the lesion site for at least six weeks. The researchers also observed enhanced axonal sprouting and recovery of nerve function at the injury site when the thermostabilized enzyme was delivered.

The delivery system also enabled the combination of therapies. Animals treated with thermostabilized chABC in combination with sustained delivery of neurotrophin-3 — a protein growth factor that helps to support the survival and differentiation of neurons — showed significant improvement in locomotor function and enhanced growth of sensory axons and sprouting of fibers for the neurotransmitter serotonin.

“These results bring us a step closer to repairing spinal cord injuries, which require multiple steps including minimizing the extent of secondary injury, bridging the lesion, overcoming inhibition due to scar, and stimulating nerve growth,” added Bellamkonda, who is also deputy director of research for GTEC, a regenerative medicine center based at Georgia Tech and Emory University, and a Georgia Cancer Coalition Distinguished Cancer Scholar.

This research was funded by Award No. R01 NS043486 from the National Institute of Neurological Disorders and Stroke (NINDS) of the National Institutes of Health (NIH). The content is solely the responsibility of the principal investigator and does not necessarily represent the official view of the NINDS or the NIH.

Adapted from materials provided by Georgia Institute of Technology Research News.

20091104-3

This digitally-colorized negative-stained transmission electron micograph (TEM) depicted a number of influenza A virions. (Credit: CDC/F. A. Murphy)

ScienceDaily.com, October/November 2009  –  As the nation copes with a shortage of vaccines for H1N1 influenza, a team of Alabama researchers have raised hopes that they have found an Achilles’ heel for all strains of the flu — antioxidants.

In an article appearing in the November 2009 print issue of the FASEB Journal, they show that antioxidants — the same substances found in plant-based foods — might hold the key in preventing the flu virus from wreaking havoc on our lungs.

“The recent outbreak of H1N1 influenza and the rapid spread of this strain across the world highlights the need to better understand how this virus damages the lungs and to find new treatments,” said Sadis Matalon, co-author of the study. “Additionally, our research shows that antioxidants may prove beneficial in the treatment of flu.”

Matalon and colleagues showed that the flu virus damages our lungs through its “M2 protein,” which attacks the cells that line the inner surfaces of our lungs (epithelial cells). Specifically, the M2 protein disrupts lung epithelial cells’ ability to remove liquid from inside of our lungs, setting the stage for pneumonia and other lung problems. The researchers made this discovery by conducting three sets of experiments using the M2 protein and the lung protein they damage.

First, frog eggs were injected with the lung protein alone to measure its function. Second, researchers injected frog eggs with both the M2 protein and the lung protein and found that the function of the lung protein was significantly decreased. Using molecular biology techniques, scientists isolated the segment of the M2 protein responsible for the damage to the lung protein. Then they demonstrated that without this segment, the protein was unable to cause damage. Third, the full M2 protein (with the “offending” segment intact) and the lung protein were then re-injected into the frog eggs along with drugs known to remove oxidants. This too prevented the M2 protein from causing damage to the lung protein. These experiments were repeated using cells from human lungs with exactly the same results.

“Although vaccines will remain the first line of intervention against the flu for a long time to come, this study opens the door for entirely new treatments geared toward stopping the virus after you’re sick,” said Gerald Weissmann, M.D., Editor-in-Chief of the FASEB Journal, “and as Thanksgiving approaches, this discovery is another reason to drink red wine to your health.” 

Journal reference:

  • 1. Ahmed Lazrak, Karen E. Iles, Gang Liu, Diana L. Noah, James W. Noah, and Sadis Matalon. Influenza virus M2 protein inhibits epithelial sodium channels by increasing reactive oxygen species. The FASEB Journal, 2009; DOI: 10.1096/fj.09-135590

Adapted from materials provided by Federation of American Societies for Experimental Biology

FierceHealthCare.com, November 2, 2009  —  A new strain of methicillin-resistant Staphylococcus aureus (MRSA) is emerging, which poses a grave threat to anyone who contracts it. Researchers with Henry Ford Hospital say the USA600 strain is partially immune to vancomycin, though the drug has proved effective in treating MRSA in the past.

According to research presented at the annual meeting of the Infectious Diseases Society of America, half of the USA600-infected patients in the study died within a month, a death rate which is a staggering five times that of those infected with known MRSA strains. Ordinarily, 11 percent of patients infected with MRSA die within 30 days.

Researchers aren’t sure, however, if USA600 is causing deaths on its own. Another factor may be the age of the patients, as those with the strain were, on average, 64 years old, as compared with 52 years old for other MRSA-infected people.

Type that causes blood stream infections can be quickly fatal, study finds

20091104-2SUNDAY, Nov. 1 (HealthDay News) — New research holds bad news for health officials worried about a potentially lethal infection called MRSA that haunts hospitals: A strain that infects the bloodstream is five times more deadly than other strains.

To make matters worse, the USA600 strain appears to be at least partially immune to an antibiotic that’s used to treat the condition, the researchers have found.

A full half of patients infected with the strain died within a month, according to a study scheduled to be presented at the annual meeting of the Infectious Diseases Society of America, held Oct. 29 to Nov. 1 in Philadelphia. That’s nearly five times the death rate of other people infected with MRSA, and 10 to 30 percent of those who acquire MRSA infections in the bloodstream die within a month, the study found.

MRSA, or methicillin-resistant Staphylococcus aureus, causes infections in the skin and bloodstream. It can also infect surgical wounds and cause pneumonia. In most cases, it sickens people in the hospital, but cases are becoming more common outside the health-care community, according to information in a news release from the Henry Ford Health System.

Researchers think it’s possible that the USA600 strain is unique. But they don’t know if other factors — such as the age of patients — could be at play.

Those who developed the USA600 strain tended to be older than those who acquired other MRSA strains, averaging 64 compared with 52 years old, the study noted.

“While many MRSA strains are associated with poor outcomes, the USA600 strain has shown to be more lethal and cause high mortality rates,” Dr. Carol Moore, the study’s lead author and a research investigator at the Henry Ford Hospital’s division of infectious diseases, said in the news release.

“In light of the potential for the spread of this virulent and resistant strain and its associated mortality,” she said, “it is essential that more effort be directed to better understanding this strain to develop measures for managing it.”

MRSA is challenging to treat because strains can be immune to many medications. The USA600 strain appears to be more immune than other strains to the drug vancomycin, which often still has the power to vanquish MRSA.

More information

The U.S. Centers for Disease Control and Prevention has more about MRSA.

More study needed to discern if difference is due to intensive care overuse or underuse

20091104-1 FRIDAY, Oct. 30 (HealthDay News) — Dying hospital patients in the United States are nearly five times more likely to spend their last days in the intensive care unit than patients in England, finds a new study, and U.S. patients over age 85 are eight times more likely to be in the ICU when they die.

That’s the conclusion of Columbia University researchers who compared data from England and from seven states (Florida, Massachusetts, New Jersey, New York, Texas, Virginia and Washington).

Of all patients discharged from the hospital, 2.2 percent in England received intensive care, compared to 19.3 percent in the United States, according to the report published in the Nov. 1 issue of the American Journal of Respiratory and Critical Care Medicine.

The death rate among patients who received intensive care in England was nearly three times higher than in the United States (19.6 percent versus 7.4 percent). However, only 10.6 percent of hospital deaths in England involved the ICU, compared with 47.1 percent in the United States. Among patients over 85, 1.3 percent in England received ICU care, compared with 11 percent of those in the United States, the researchers found. Rates of ICU care for young adults and children were similar in both countries.

“These numbers need to be interpreted with caution as the differences in mortality for ICU patients likely reflect the higher severity of illness of patients admitted in the first place in England,” lead author Dr. Hannah Wunsch, an assistant professor of anesthesiology and critical care medicine, said in a news release from the American Thoracic Society. “The data do bring up the interesting question of how much intensive care is beneficial. Doing more may not always be better,” she added.

“In England, there is universal health care through the National Health Service, and there is also much lower per-capita expenditure on intensive care services when compared to the U.S.,” Wunsch said. “The use of intensive care in England is limited by supply to a greater degree than it is in the U.S. and there are consequently implicit and explicit decisions regarding who gets those limited services. We wished to examine what different decisions are made,” she explained.

“Whether less intensive care for very elderly patients who are dying is a form of rationing or is actually better recognition of what constitutes appropriate care at the end of life warrants further research,” Wunsch said. “These findings highlight the urgent need to understand whether there is overuse of intensive care in the U.S., or under-use in England.”

More information

The American Thoracic Society has more about critical care.

While methicillin-resistant Staphylococcus aureus (MRSA) is already known to be a huge problem within hospitals, fewer professionals realize that it’s also becoming a serious threat for the public at large, according to a new report. This is grim news, given that some non-hospital strains of MRSA may be even worse than the hospital-based variety.

In 2005, there were about 18,650 hospital deaths caused by approximately 94,360 invasive MRSA infections, according to projections by CDC researchers. In fact, MRSA has apparently become the leading cause of skin and soft-tissue infections among U.S. emergency department patients. To date, 85 percent of those were healthcare-related, according to a study, in Journal of the American Medical Association.

However, the number of MRSA infections contracted in other ways–such as in prisons or among athletes is growing at a brisk clip.

A study of the disinfectant Byotrol at Glasgow Royal Infirmary in Scotland shows that the sanitizer cut down on the spread of methicillin-resistant Staphylococcus aureus (MRSA) by 75 percent. Recently, a study published in Infection Control and Hospital Epidemiology underscored the danger that both patients and healthcare workers face from community-acquired MRSA, a potentially deadly, antibiotic-resistant staph infection. Byotrol could help stem the spread of the bug. “Byotrol is said to be different from other disinfectants because it leaves a film on surfaces which prevents bacteria from attaching themselves and reproducing. The bugs become exhausted and agents in the disinfectant then kill them,” reports Science Daily.

NewScientist.com, by Eugenie Samuel Reich  —  In February 2003, astronomers involved in the search for extraterrestrial intelligence (SETI) pointed the massive radio telescope in Arecibo, Puerto Rico, at around 200 sections of the sky.

The same telescope had previously detected unexplained radio signals at least twice from each of these regions, and the astronomers were trying to reconfirm the findings. The team has now finished analysing the data, and all the signals seem to have disappeared. Except one, which has got stronger.

This radio signal, now seen on three separate occasions, is an enigma. It could be generated by a previously unknown astronomical phenomenon. Or it could be something much more mundane, maybe an artefact of the telescope itself.

But it also happens to be the best candidate yet for a contact by intelligent aliens in the nearly six-year history of the SETI@home project, which uses programs running as screensavers on millions of personal computers worldwide to sift through signals picked up by the Arecibo telescope.

Absorb and emit

“It’s the most interesting signal from SETI@home,” says Dan Werthimer, a radio astronomer at the University of California, Berkeley (UCB) and the chief scientist for SETI@home. “We’re not jumping up and down, but we are continuing to observe it.”

Named SHGb02+14a, the signal has a frequency of about 1420 megahertz. This happens to be one of the main frequencies at which hydrogen, the most common element in the universe, readily absorbs and emits energy.

Some astronomers have argued that extraterrestrials trying to advertise their presence would be likely to transmit at this frequency, and SETI researchers conventionally scan this part of the radio spectrum.

SHGb02+14a seems to be coming from a point between the constellations Pisces and Aries, where there is no obvious star or planetary system within 1000 light years. And the transmission is very weak.

“We are looking for something that screams out ‘artificial’,” says UCB researcher Eric Korpela, who completed the analysis of the signal in April. “This just doesn’t do that, but it could be because it is distant.”

Unknown signature

The telescope has only observed the signal for about a minute in total, which is not long enough for astronomers to analyse it thoroughly. But, Korpela thinks it unlikely SHGb02+14a is the result of any obvious radio interference or noise, and it does not bear the signature of any known astronomical object.

That does not mean that only aliens could have produced it. “It may be a natural phenomenon of a previously undreamed-of kind like I stumbled over,” says Jocelyn Bell Burnell of the University of Bath, UK.

It was Bell Burnell who in 1967 noticed a pulsed radio signal which the research team at the time thought was from extraterrestrials but which turned out to be the first ever sighting of a pulsar.

There are other oddities. For instance, the signal’s frequency is drifting by between eight to 37 hertz per second. “The signal is moving rapidly in frequency and you would expect that to happen if you are looking at a transmitter on a planet that’s rotating very rapidly and where the civilisation is not correcting the transmission for the motion of the planet,” Korpela says.

This does not, however, convince Paul Horowitz, a Harvard University astronomer who looks for alien signals using optical telescopes. He points out that the SETI@home software corrects for any drift in frequency.

Fishy and puzzling

The fact that the signal continues to drift after this correction is “fishy”, he says. “If [the aliens] are so smart, they’ll adjust their signal for their planet’s motion.”

The relatively rapid drift of the signal is also puzzling for other reasons. A planet would have to be rotating nearly 40 times faster than Earth to have produced the observed drift; a transmitter on Earth would produce a signal with a drift of about 1.5 hertz per second.

What is more, if telescopes are observing a signal that is drifting in frequency, then each time they look for it they should most likely encounter it at a slightly different frequency. But in the case of SHGb02+14a, every observation has first been made at 1420 megahertz, before it starts drifting. “It just boggles my mind,” Korpela says.

The signal could be an artefact that, for some reason, always appears to be coming from the same point in the sky. The Arecibo telescope has a fixed dish reflector and scans the skies by changing the position of its receiver relative to the dish.

When the receiver reaches a certain position, it might just be able to reflect waves from the ground onto the dish and then back to itself, making it seem as if the signal was coming from space.

“Perhaps there is an object on the ground near the telescope emitting at about this frequency,” Korpela says. This could be confirmed by using a different telescope to listen for SHGb02+14a.  Read more at: http://www.newscientist.com/article/dn6341

 

There is also the possibility of fraud by someone hacking the SETI@home software to make it return evidence for an extraterrestrial transmission. However, SHGb02+14a was seen on two different occasions by different SETI@home users, and those calculations were confirmed by others.

Then the signal was seen a third time by the SETI@home researchers. The unusual characteristics of the signal also make it unlikely that someone is playing a prank, Korpela says. “As I can’t think of any way to make a signal like this, I can’t think of any way to fake it.”

David Anderson, director of SETI@home, remains sceptical but curious about the signal. “It’s unlikely to be real but we will definitely be re-observing it.” Bell Burnell agrees that it is worth persisting with. “If they can see it four, five or six times it really begins to get exciting,” she says.

It is already exciting for IT engineers Oliver Voelker of Logpoint in Nuremberg, Germany and Nate Collins of Farin and Associates in Madison, Wisconsin, who found the signal.

Collins wonders how his bosses will react to company computers finding aliens. “I might have to explain a little further about just how much I was using [the computers],” he says.  Read more at: http://www.newscientist.com/article/mg18524911.600-13-things-that-do-not-make-sense.html?page=1