SLOW BEAT, LONG LIFE
Slow heartbeat when at rest can increase the chances of living longer, says a French survey
British scientists grow artificial liver
LONDON
Scientists at an English university have grown a miniature artificial human liver in a major medical breakthrough that researchers hope could be used to test drugs, help repair damaged livers, and eventually produce entire organs for lifesaving transplants.
The organ, about the size of a thumbnail, was grown using stem cells in blood taken from umbilical cords. Prof. Colin McGuckin, who specializes in regenerative medicine, made the breakthrough with Dr. Nico Forraz at Newcastle University, the Daily Mail reported.
While other scientists have created liver cells, the Newcastle team was the first to create sizeable sections of tissue from stem cells from the umbilical cord. The pair extracted blood from the umbilical cords of newborn babies. They were then placed in a "bioreactor," which mimics the effects of weightlessness. This allows the cells to multiply more quickly. Chemicals and hormones were then added to encourage the stem cells to turn into liver tissue.
McGuckin said pharmaceutical companies and they can use the mini-livers to test new drugs. "When a drug company is developing a new drug it first tests it on human cells and then tests it on animals before beginning trials on humans. Moving from testing on animals to humans is a massive leap and there is still a risk. But by using the mini-livers we have developed there is no need to test on animals or humans."
They could potentially be used like dialysis machines, buying time for a patient's liver to repair itself or for doctors to find a replacement liver.
French, Swiss scientists discover hunger gene
GENEVA
A team of French and Swiss scientists said they had discovered a hunger gene in mice that could pave the way for treatments for obesity or alcoholism. Researchers at the University of Fribourg, Switzerland, and the Louis Pasteur University in Strasbourg, France, found that the gene allows the body to detect the sensation of hunger before meals, the Swiss university said.
The gene called "Per 2" acts throughout the body and on the brain, generating signals warning of hunger, partly based on a notion of time, the university said.
The biochemists, Urs Albrecht, a professor at Fribourg and Etienne Challet of the Louis Pasteur University, managed to diminish and even cut off the signals of hunger in their experiments.
Mice that had modified forms of the gene were unable to detect hunger until they were confronted with food, while those with the normal gene started searching for food shortly before they were due for a meal. The findings on a link between the timing of meals and the sensation of hunger was a "very promising" avenue to explore for treatment for "surplus weight, sleeping disorders, depression, or alcoholism," the university said.
The research was published in the Current Biology.
Regenerative therapy gets boost from cardiac stem cells
WASHINGTON
New research shows master cardiac stem cells may exist that can produce all three major tissues of the mammalian heart, news that could have far-reaching implications in regenerative cardiac repair. A study in the journal Cell suggests the possible stem cells' existence, and a second paper found a second type of heart cell progenitor that can make both cardiac muscle and smooth muscle in blood- vessel walls.
"It's a surprise that a single cell can give rise to all these tissues and structures in the heart," said Kenneth Chien of Massachusetts General Hospital and Harvard Medical School. "The heart may look more like blood than we thought," he added, referring to single-celled hematopoietic stem cells that give rise to all cell types found in blood.
For Howard Hughes Medical Institute investigator Stuart Orkin, who authored a companion paper from the Children's Hospital Boston: "This changes the way we think about organ development. Rather than different cell types coming together, the heart appears to develop from a common set of progenitors or stem cells. This may be a more economical method."
Chien pointed out that embryonic stem cells are difficult to use because of the danger of teratomas, cancers that can result from out-of-control growth of embryonic stem cells. "If we can get around that threat by cloning master cardiovascular stem cells, that would be a major advance," he said.
"Regenerative stem-cell therapies for heart disease will require an understanding of and an ability to manipulate the molecular mechanisms that govern the fates, differentiation, and morphogenesis of the myriad cell types that comprise the heart," wrote Daniel Garry and Eric Olson in a brief review. These studies offer a "step toward this goal" by providing "evidence for common multipotential progenitors of the three major cell types of the heart," they added.
Sea-urchin genome could shed light on human disease
WASHINGTON
Scientists have sequenced the genome of the sea urchin, an invertebrate surprisingly similar to man, a step that could help develop new treatment for diseases such as cancer.
After identifying the 23,300 genes of the Strongylocentrotus pur-puratus (California purple sea urchin) genome, researchers found humans shared 7,077 of their genes with the arguably different-looking brainless and limbless invertebrate. The genetic ties were far closer than scientists expected and make the sea urchin a closer genetic cousin of man than the worm or fruit fly, the study published in Science found.
"Nobody would've predicted that sea urchins have such a robust gene set for visual perception," said Gary Wessel, a Brown University biology professor and member of the Sea Urchin Genome Sequencing Consortium. "I've been looking at these organisms for 31 years, and now I know they were looking back at me."
Among other surprises from the project were that researchers found sea urchins have the most sophisticated innate immune system of any animal studied to date-one reason they live 100 years or more. They carry genes associated with human diseases such as muscular dystrophy and Huntington's disease.
Slower heartbeat at rest could mean longer life
PARIS
Slowing down heartbeat when at rest can increase the chances of living longer, according to a French survey carried out on more than 4,000 men over two decades.
The study by the National Health and Medical Research Institute (INSERM) showed that middle-aged men whose resting heart rate increased over five years had a much higher risk of death during the 20-year period. Men whose pulse while at rest decreased by more than seven beats a minute in five years had a decrease in mortality of 18 percent compared with those whose heartbeat remained stable. An increase of more than seven beats a minute, on the other hand, meant a 47-percent increase in mortality.
The study led by Xavier Jouven was presented at the American Heart Association's annual congress in Chicago. It was based on 4,320 city dwellers between 42 and 53 years old who were recruited between 1967 and 1972 and followed for more than 20 years. During that period, 1,018 men died from various causes, including cardiovascular disease. Other risk factors, such as age, physical activity, smoking, body mass, blood pressure, blood sugar, and total cholesterol were taken into consideration.
Pulse should be examined as systematically as heart pressure, Jouven said. "It is a health indicator that has been neglected up until now. We don't know why resting heart rate goes down or up over time. It might be related to lifestyle changes, such as less activity. We also cannot say for sure whether the increase in resting heart rate is only a marker for some other disease process or whether it is directly associated with mortality."
Stem-cell breakthrough lets blind mice see again
PARIS
Scientists in Britain have restored sight to blind mice by transplanting stem cells at a key stage of development into damaged retinas, Nature reported. The feat is being hailed as a breakthrough in stem-cell technology, which has suffered from many false dawns.
The British study focuses on replenishment of rod-like photoreceptor cells on the retina that pick up light and send a signal to the brain via the optic nerve. Photoreceptors are like the pixels in a TV or computer screen, but many times more plentiful-each eye has over a hundred million light-sensitive cells, equivalent to a thousand such screens.
These vital cells can be destroyed by diseases such as diabetes, age-related macular degeneration, and retinitis pigmentosa, leading to irreversible blindness. Millions around the world are affected by these diseases.
Scientists have tried for several years to attack this tragic problem by transplanting stem cells, the versatile immature cells that grow into various tissues of the body. Until now, though, they have met with failure. The favored source is stem cells at a very early stage of development, yet these fail for some reason to be integrated into the retina.
The British team has taken a different tack, trying cells that instead of being very immature have been allowed to grow a little toward becoming photoreceptors. They used these committed-but not yet fully differentiated-cells to restoring some vision to mice born with a genetic disease similar to retinitis pigmentosa.
The most successful cells were taken from the retinas of baby mice between three and five days old, they found.
"We worked on the theory that cells at a later stage of development might have a higher probability of success upon transplantation," said the team's coleader, Robin Ali, a professor of ophthalmology at University College London. "We show here that cells taken from the peak rod genesis stage of development, when the retina is about to be formed, can be successfully transplanted and integrate into the adult or degenerating retina."
Ali admitted he was surprised at how well the experiment had gone. "Remarkably, we found that the mature retina, previously believed to have no capacity for repair, is in fact able to support the development of new functional photoreceptors."
The next step is carry out more experiments on rodents to understand how and why this technique works, and whether the transplanted cells are safe and continue to work well over the longer term.
To accomplish the same results in humans, one obvious source would be stem cells taken from embryos, which are the most versatile stem cells of all, although their use has stirred ethical controversy, particularly in the United States.
But Ali said this might not be necessary. "Recent research has shown that a population of cells can be found on the margin of the adult retina which have stem-cell-like properties-in other words, they are capable of self-renewal," he explained. "These could be harvested through minor surgery and grown in the lab to become photoreceptor precursors before being reimplanted on the retina."
One of the most exciting discoveries has to do with timing: the best moment to use the stem cells was after they had stopped dividing, indicating they had reached the desired "precursor" stage.
That breakthrough could have implications for transplanting tissue to people who have suffered nerve-tissue damage from accidents or degenerative disease, said Thomas Reh, a structural biologist at the University of Washington. "It may be that the specific time at which the particular cell is harvested will make all the difference to its potential for integration and functional differentiation following transplantation," he said in a review of the study, also published by Nature. "Sometimes, timing is everything." M
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