,, August 4, 2009  —  In a finding that is a major advance in spinal cord injury research, U.S. scientists report that regenerating axons can be guided to their correct targets where they can re-form connections after spinal cord injury.

Previous research showed that severed axons — long, slender projections of a nerve cell that conduct electrical impulses — can be coaxed to regenerate into and beyond sites of spinal cord injury. But it hasn’t been clear how to guide these axons to the precise target, according to a news release from the University of California, San Diego.

In experiments on rats, researchers at the UCSD School of Medicine found that regenerating axons can be guided to the correct target using a nervous system growth factor called neurotrophin-3 (NT-3).

When the growth hormone was placed in the correct target, axons grew into it and formed electrical connections called synapses. When the growth factor was placed in the wrong target, the researchers found that the axons grew into that target as well, according to the study published online Aug. 2 in the journal Nature Neuroscience.

“The ability to guide regenerating axons to a correct target after spinal cord injury has always been a point of crucial importance in contemplating translation of regeneration therapies to humans,” senior author Dr. Mark Tuszynski, director of UCSD’s Center for Neural Repair, said in a news release.

“While our findings are very encouraging in this respect, they also highlight the complexity of restoring function in the injured spinal cord,” he said.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about spinal cord injuries.,, August 4, 2009   —   Researchers in Japan report that they’ve grown new teeth in mice with the help of bioengineered tissue, an early sign of progress in the effort to grow new organs in humans.

The research provides “convincing” proof that bioengineered teeth can be fully functional, said Dr. Fei Liu, a researcher at the Institute for Regenerative Medicine at the Texas A&M Health Science Center, who’s familiar with the findings of the study.

Liu cautioned that “the general public should be aware that this kind of research is still far from application” in humans. But in the future, he predicted, people will prefer “biological” teeth like those created by the Japanese researchers to porcelain replacement teeth because they will look better and be more functional.

The researchers behind the study wanted to find out what would happen if they took bioengineered tooth “germs” — tissue that holds the instructions to building a tooth — and transplanted it into the jawbones of mice.

What happened was that teeth developed from the bioengineered tissue. And the mice had no trouble eating with the new teeth, said Takashi Tsuji, a researcher at the Tokyo University of Science and a co-author of the study. The teeth also developed nerve fibers that could feel pain.

A report on the study appears online in the Aug. 3-7 early edition of the Proceedings of the National Academy of Sciences.

Why bother developing technology to regenerate teeth in the first place? Because it could help humans whose teeth are malformed, said Dr. Louis J. Elsas, interim chairman of the Department of Biochemistry and Molecular Biology at the University of Miami Miller School of Medicine.

“Tooth regeneration could be useful particularly in infant malformations such as cleft lip and palate, and other malformations involving teeth and bone of the oral cavity,” Elsas said.

Researchers have also discussed the possibility of using generated teeth as replacements for inlays and synthetic implants.

But Tsuji acknowledged that there’s a potential hitch on the road to generation of teeth in humans: Scientists have not found the cells in humans that are needed to start the tooth-generation process. This means they’re further along with mice.

Even so, it might eventually be possible to use a person’s own cells instead of using cells from embryos, Tsuji said.

What this might cost is unknown.

As for the future, “many researchers hope our study will be adaptable to a wide variety of organs,” Tsuji said.

The challenge for scientists will be to figure out how to generate organs that make enough connections to the body to function properly.


Interrupting Bacterial Chatter to Thwart Infection

HowardHughesMedicalInstitute, July/August 2009  —  Interfering with communication among bacteria can prevent them from mounting a unified and perhaps deadly assault on their host organism, research by Howard Hughes Medical Institute (HHMI) investigators shows. The finding suggests a different kind of medicine that could be less likely than traditional antibiotic to promote the development of drug-resistant bacteria.

The new research, published July 30, 2009, in Molecular Cell, targeted a bacterial communication process known as quorum sensing, which triggers bacteria to act collectively only once they reach sufficient numbers to make their common activity worthwhile. In the case of disease-causing bacteria, that collective action is often the release of toxins.

“If you cut off those lines of communication, you have just individuals acting and you don’t get the benefit of the collective, coordinated behavior.”

Bonnie L. Bassler

Virulent bacteria do not want to begin secreting toxins too soon, or the host’s immune system will quickly eliminate the nascent infection, explains HHMI investigator Bonnie Bassler, who led the research. So they use quorum sensing to count themselves, and launch their attack only when they reach a sufficiently high number. This way, the bacteria are more likely to overpower the immune system.

Quorum sensing is much like coordinating an army, says Bassler, who is at Princeton University. “These are the lines of communication from the generals to the crowd that make something happen. If you cut off those lines of communication, you have just individuals acting and you don’t get the benefit of the collective, coordinated behavior.”

The process gives bacteria some of the same advantages that multicellular organisms have, she adds. “You have all these cells doing the same thing at the same time, and the whole organism-the collective-benefits.”

To measure their own numbers, bacteria produce, release, and detect chemical signals called autoinducers. As a population of bacteria grows, it releases more autoinducer into its environment. When individuals detect that a threshold level of autoinducer is present, they change their behavior – by releasing a toxin, for example.

Bassler and her colleagues disrupted these lines of communication by interfering with molecules called acyl-homoserine lactone (AHL) autoinducers, which drive quorum sensing among a kind of bacteria known as Gram-negative bacteria. Gram-negative bacteria include Pseudomonas, E. coli and Salmonella, and other disease-causing microbes. In the study, the team focused on Chromobacterium violaceum, which rarely infects human, but can be lethal to other organisms. C. violaceum lends itself to studies of quorum sensing because it produces a readily detected, bright purple dye when it detects that its population has reached a critical mass.

Gram-negative bacteria have two types of receptors that detect AHL, ultimately triggering changes in the activity of the microbes’ virulence genes. One receptor type, LuxR, binds with the partner AHL autoinducer inside the cell; the other, LuxN, binds with its cognate AHL molecule outside the cell. The researchers developed inhibitors that each interfered with both receptor types.

Bassler says the team based its work on earlier research from her lab that screened 35,000 chemicals at the Broad Institute in Cambridge, Mass., co-founded by HHMI investigator Stuart L. Schreiber. That screen identified 15 chemicals that could interfere with LuxN-type receptors, inhibiting AHL quorum sensing.

Team member Lee Swem then had what Bassler called an inspired idea: to determine whether these same chemicals could also interfere with the LuxR-type receptors, even though the two types of receptors are evolutionarily unrelated and work by very different means and reside in different sub-cellular locations.

The researchers took one promising candidate from the Broad Institute screen and tweaked the chemical’s molecular structure to yield a host of similar chemicals, including two even stronger inhibitors, chlorothiolactone (CTL) and chlorolactone (CL).

“Lo and behold, they worked,” Bassler says of the chemicals’ impact on LuxR-type receptors. “That was quite remarkable because we didn’t have any evidence that they [the inhibitors] could get inside of the cell. So Lee’s work showed that the inhibitors could work from both the outside and the inside.”

The most potent of these inhibitors, CL, protected the roundworm Caenorhabditis elegans from death due to C. violaceum infection, without itself causing any apparent ill effects, the researchers found.

The experiment shows that interfering with quorum sensing may provide an alternative to traditional antibiotics, Bassler says, and circumvent the problem of resistance that antibiotics foster by killing off susceptible bacteria but allowing resistant ones to survive and propagate. 


About Bonnie L. Bassler PhD: 

Until recently, the ability of bacteria to communicate with one another was considered an anomaly that occurred only among a few marine bacteria. It is now clear that group talk is the norm in the bacterial world, and understanding this process is important for fighting deadly strains of bacteria and for understanding communication between cells in the human body.

Bonnie Bassler has discovered that bacteria communicate with a chemical language. This process, called quorum sensing, allows bacteria to count their numbers, determine when they have reached a critical mass, and then change their behavior in unison to carry out processes that require many cells acting together to be effective.

For example, one process commonly controlled by quorum sensing is virulence. Virulent bacteria do not want to begin secreting toxins too soon, or the host’s immune system will quickly eliminate the nascent infection. Instead, Bassler explained, using quorum sensing, the bacteria count themselves and when they reach a sufficiently high number, they all launch their attack simultaneously. This way, the bacteria are more likely to overpower the immune system. Quorum sensing, Bassler says, allows bacteria to act like enormous multicellular organisms. She has shown that this same basic mechanism of communication exists in some of the world’s most virulent microbes, including those responsible for cholera and plague.

Working with Vibrio harveyi, a harmless marine bacterium that glows in the dark, Bassler and her colleagues discovered that this bacterium communicates with multiple chemical signaling molecules called autoinducers (AIs). Some of these molecules allow V. harveyi to talk to its own kind, while one molecule-called AI-2-allows the bacterium to talk to other bacterial species in its vicinity. Bassler showed that a gene called luxS is required for production of AI-2, and that hundreds of species of bacteria have this gene and use AI-2 to communicate. This work suggests that bacteria have a universal chemical language, a type of “bacterial Esperanto” that they use to talk between species.

Bassler’s research opens up the possibility for new strategies for combating important world health problems. Her team is currently working to find ways to disrupt the LuxS/AI-2 discourse so the bacteria either cannot talk or cannot listen to one another. Such strategies have potential use as new antimicrobial therapies.

Her interest in bacterial communication grew from her curiosity about how information flows among cells in the human body, and she is convinced she will find parallels between the bacterial systems and those in higher organisms. “We have a chance to learn something fundamental in bacteria about chemical communication,” Bassler said. “If we can understand the rules or paradigms governing the process in bacteria, what we learn could hold true in higher organisms.”

Bassler won a 2002 MacArthur Fellowship, which she said provided tremendous validation for her group’s research, recognizing that they are working on a problem that is much larger than a glow-in-the-dark bacterium. She was also chosen as the 2004 Inventor of the Year by the New York Intellectual Property Law Association for her idea that interfering with the AI-2 language could form the basis of a new type of broad-spectrum antibiotic. “The fantasy is to make one pill that works against all kinds of bacteria,” she said.

Dr. Bassler is also Squibb Professor and Director of Graduate Studies in the Department of Molecular Biology at Princeton University.

Bonnie Bassler studies the molecular mechanisms that bacteria use to communicate with one another, and her aims include combating deadly bacterial diseases and understanding cell signaling in higher organisms., August 4, 2009  —  Bacterial infection is a major health threat to patients with severe burns and other kinds of serious wounds such as traumatic bone fractures. Recent studies have identified an important new weapon for fighting infection and healing wounds: insulin.

Now, using tiny nanodiamonds, researchers at Northwestern University have demonstrated an innovative method for delivering and releasing the curative hormone at a specific location over a period of time. The nanodiamond-insulin clusters hold promise for wound-healing applications and could be integrated into gels, ointments, bandages or suture materials.

Localized release of a therapeutic is a major challenge in biomedicine. The Northwestern method takes advantage of a condition typically found at a wound site — skin pH levels can reach very basic levels during the repair and healing process. The researchers found that the insulin, bound firmly to the tiny carbon-based nanodiamonds, is released when it encounters basic pH levels, similar to those commonly observed in bacterially infected wounds. These basic pH levels are significantly greater than the physiological pH level of 7.4.

The results of the study were published online July 26 by the journal Biomaterials.

“This study introduces the concept of nanodiamond-mediated release of therapeutic proteins,” said Dean Ho, assistant professor of biomedical engineering and mechanical engineering at the McCormick School of Engineering and Applied Science. Ho led the research. “It’s a tricky problem because proteins, even small ones like insulin, bind so well to the nanodiamonds. But, in this case, the right pH level effectively triggers the release of the insulin.”

A substantial amount of insulin can be loaded onto the nanodiamonds, which have a high surface area. The nanodiamond-insulin clusters, by releasing insulin in alkaline wound areas, could accelerate the healing process and decrease the incidence of infection. Ho says this ability to release therapeutics from the nanodiamonds on demand represents an exciting strategy towards enhancing the specificity of wound treatment.

In their studies, Ho and his colleagues showed that the insulin was very tightly bound to the nanodiamonds when in an aqueous solution near the normal physiological pH level. Measurements of insulin function revealed that the protein was virtually inactive when bound to the nanodiamonds — a beneficial property for preventing excess or unnecessary drug release.

Upon increasing the pH to the basic levels commonly observed in the skin during severe burns, the researchers confirmed the insulin was released from the nanodiamond clusters and retained its function. Exploiting this pH-mediated release mechanism may provide unique advantages for enhanced drug delivery methods.

The researchers also found the insulin slowly and consistently released from the nanodiamond clusters over a period of several days.

Insulin accelerates wound healing by acting as a growth hormone. It encourages skin cells to proliferate and divide, restores blood flow to the wound, suppresses inflammation and fights infection. Earlier investigations have confirmed an increase in alkalinity of wound tissue, due to bacterial colonization, to levels as high as pH 10.5, the pH level that promoted insulin release from the nanodiamonds in the Northwestern study.

Ho’s group next will work on integrating the nanodiamond-insulin complexes into a gel and conducting preclinical studies. The researchers also will investigate different areas of medicine in which the nanodiamond-insulin clusters could be used.

Nanodiamonds have many advantages for biomedical applications. The large surface area allows a large amount of therapeutic to be loaded onto the particles. They can be functionalized with nearly any type of therapeutic, including small molecules, proteins and antibodies. They can be suspended easily in water, an important property in biomedicine. The nanodiamonds, each being four to six nanometers in diameter, are minimally invasive to cells, biocompatible and do not cause inflammation, a serious complication. And they are very scalable and can be produced in large quantities in uniform sizes.

By harnessing the unique surface properties of the nanodiamonds, Ho and his colleagues have demonstrated that the nanodiamonds serve as platforms that can successfully bind, deliver and release several classes of therapeutics, which could impact a broad range of medical needs.

Ho’s research group also has studied nanodiamonds for applications in cancer therapy. They demonstrated that nanodiamonds are capable of releasing the chemotherapy agent Doxorubicin in a sustained and consistent manner. (Ho is a member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University.)

In addition to using the nanodiamonds in their particle form, Ho’s group has developed devices that harness the slow drug-release capabilities of the nanodiamonds. More recently, his team has shown that nanodiamonds are effective in dispersing insoluble drugs in water, boosting their potential for broader applications in medicine.

Source : Northwestern University

August 3, 2009, By Gabe Mirkin MD  —  Athletes in endurance events practice a training technique called “living high, training low”. Many years ago, scientists noticed that people who live in the mountains, where the air contains lower levels of oxygen, have higher than normal blood oxygen levels. A limiting factor in events that require endurance is the time it takes to move oxygen from the lungs into the muscles. Since more than 98 percent of the oxygen in the blood is bound to red blood cells, people with high numbers of red blood cells should have higher levels of oxygen and therefore have more oxygen available for their muscles, giving them greater endurance. It appears that living and training at high altitude would improve performance even more, so theoretically, all long distance runners, cross country skiers, bicycle racers and other athletes in endurance sports would benefit from living and training at high altitudes.

However, you can’t train as intensely in the mountains where oxygen is sparse. Lack of oxygen during hard exercise slows you down. One group of researchers decided to see if living at high altitudes would increase red blood cell concentration, and training at low altitude would allow the athletes to take harder workouts. Eleven trained middle-distance runners were tested before an 18-day training session in which they slept in special low-oxygen pressure chambers and trained at sea level with oxygen-rich air (Journal of Applied Physiology, January 2006). The tests were repeated 15 days after the training. The athletes who lived high and trained low had higher maximal oxygen uptakes, higher maximal aerobic power and lower resting heart rates than the control group. The blood of these athletes could carry more oxygen, and the oxygen concentration in their bloodstream would return to normal earlier after intense competitions so their performance would improve.

Barometric pressure chambers are available for about $8000, so serious endurance athletes can “sleep high” and train wherever they live.