Researchers report initial success in promising approach to prevent tooth decay



Yüklə 257.11 Kb.
səhifə3/8
tarix01.11.2017
ölçüsü257.11 Kb.
1   2   3   4   5   6   7   8

St. Jude Children's Research Hospital

St. Jude Children's Research Hospital is internationally recognized for its pioneering work in finding cures and saving children with cancer and other catastrophic diseases. Founded by late entertainer Danny Thomas and based in Memphis, Tenn., St. Jude freely shares its discoveries with scientific and medical communities around the world. No family ever pays for treatments not covered by insurance, and families without insurance are never asked to pay. St. Jude is financially supported by ALSAC, its fund-raising organization. For more information, please visit www.stjude.org.


Viking landers may have found Martian life after all

* 22:19 23 October 2006

* NewScientist.com news service

* Mark Buchanan and David L Chandler

A flawed test on NASA’s twin Viking spacecraft may have fooled scientists into overlooking signs of life during their examination of the Martian surface 30 years ago. Researchers now say that one of the landers’ experiments was not sensitive enough to find organic molecules in the soil, despite signs of life shown by another test. Other researchers say the team may also have been fooled by the strange forms that Martian life might take.

The results from Vikings’ onboard experiments are confusing because some tests suggested the presence of organisms capable of digesting organic molecules. But a gas-chromatograph mass spectrometer (GCMS) found nothing when the soil was heated to release organic molecules, causing most scientists to doubt the results of the life-detection tests. Instead they put the soil reactivity down to the presence of peroxides or other reactive substances.

Now, a paper by Rafael Navarro-Gonzalez of the University of Mexico and others demonstrates that the GCMS instrument was incapable of detecting organic compounds even in Mars-like soils from various locations on Earth. This includes parts of Chile's Atacama desert where other tests prove that living microbes are indeed present.

In some soils – including samples taken from Rio Tinto in Spain, which contain iron compounds similar to those detected in Mars soils by NASA's rover Opportunity, the sensitivity of the GCMS was actually a million times lower than its claimed threshold for detection, says Navarro-Gonzalez.



Outstanding puzzle

Gilbert Levin, one of the Viking scientists who has long argued that the GCMS test was flawed, told New Scientist that the new study provides "strong support" to the idea that life was indeed detected on Mars.

Geophysicist Dirk Schulze-Makuch of Washington State University in Pullman, Washington, US, says the study adds to a body of evidence that increasingly leaves the Viking results open to other interpretations.

The outstanding puzzle is to explain what causes the high reactivity of the Martian soil, coupled with an apparently very low level of organics despite a constant influx of organic material from asteroids, comets and other planetary sources. Most astrobiologists assume that some mysterious oxidising material in the soil is destroying the organic material but other possibilities are emerging.

Schulze-Makuch and Joop Houtkooper of the Justus-Liebig-University in Giessen, Germany, suggest that an exotic form of Martian life might provide a tidy explanation. They propose that an organism might have evolved on the Red Planet to use a solution of water and hydrogen peroxide as an intracellular fluid, rather than just water as Earth organisms do.

Mysterious oxidant

This has the advantage of staying liquid at very cold temperatures, allowing organisms to survive in the cold Martian climate. This internal hydrogen peroxide might then be the “mysterious” oxidant.

“We just may find life to be a bit different from life on Earth,” says Schulze-Makuch. “But wouldn’t you expect that on another planet?”

Navarro-Gonzalez says further tests should be done on Mars to answer the questions once and for all. Unfortunately, none of the experiments now slated for upcoming missions could definitively reveal whether there is life in the soil, although they could prove the presence of organic compounds and identify what they are.

And there may still be time to add instruments that could look for microbial life to NASA's planned Mars Science Laboratory, set for launch in 2009, or the European Space Agency's ExoMars mission to be launched in 2011 or 2013, he said. Journal reference: Proceedings of the National Academy of Sciences (vol 103, p 16089)
Naturally occurring enzyme can break down key part of Alzheimer's plaques

Scientists have identified a naturally occurring enzyme that can break down a key component of the brain plaques characteristic of Alzheimer's disease. The finding may provide researchers with new opportunities to understand what goes wrong in the brains of Alzheimer's patients and could one day help them seek new therapies.

Researchers at Washington University School of Medicine in St. Louis showed earlier this summer that the enzyme, matrix metalloproteinase 9 (MMP-9), degrades abnormally aggregated proteins known as amyloid fibrils, a main ingredient of brain plaques. In the brain, MMP-9 is made by support cells known as astrocytes.

MMP-9 is already well-known because of its links to cancer metastases, vascular disease, arthritis and other pathologies. Scientists called the new link to Alzheimer's encouraging, noting that previously identified enzymes only degrade a smaller, nonaggregated component of Alzheimer's plaques.

"We already knew of three enzymes that break down amyloid beta (Abeta), a protein fragment that clumps together with itself to form the fibrils," says Jin-Moo Lee, M.D., Ph.D., assistant professor of neurology. "But the thinking up until now had been that Abeta might be clumping together so tightly that the fibrils were indestructible."

In a new study, appearing October 25 in The Journal of Neuroscience, Lee's group found that disabling the mouse gene for MMP-9 increased levels of Abeta in the spaces between brain cells. The finding proves that MMP-9 contributes to clearance of Abeta from extracellular spaces and suggests its dysfunction could potentially contribute to the development of Alzheimer's.

"MMP-9 and other enzymes like it are secreted from brain support cells and active in the spaces outside of cells, and that's where we saw an increase in Abeta levels in the mice that lacked the gene for MMP-9," Lee notes. "That's relevant to Alzheimer's because all the amyloid plaques are extracellular, and the formation of the plaques seems to be related to an elevated level of Abeta that accumulates over time in those spaces."

In earlier studies, Lee's lab analyzed the production of MMP-9 in astrocytes. They found astrocytes close to amyloid plaques increased their MMP-9 production. Imaging studies also showed that MMP-9 levels increased around blood vessels laden with amyloid.

"Astrocytes become activated around plaques as they develop, and then eventually form a wall surrounding the plaques," he says.

Lee's results have led him to formulate a provocative but as yet unproven theory about an old mystery of Alzheimer's disease: why plaques continue to increase in number over time but only grow to a certain size.

"Even though everything we know about the fibrils suggests they should constantly grow, plaques reach a mature size and stop growing," Lee says. "It's possible that production of MMP-9 and other similar substances by support cells in the brain is establishing a balance that prevents the plaques from growing beyond a certain size."

To follow up, Lee plans to crossbreed mice lacking MMP-9 with a line of mice genetically modified to develop an Alzheimer's-like condition. Scientists want to see if removing MMP-9 causes the mice to develop Alzheimer's more quickly.

In a parallel project that will test MMP-9's potential as a therapeutic, Lee and his collaborators will use viruses to alter production of MMP-9 in the mouse model. Researchers want to learn if increasing levels of the enzyme present in the brain can delay onset of Alzheimer's.
News Release - heic0616: Hubble yields direct proof of stellar sorting in a globular cluster

A seven year study with the NASA/ESA Hubble Space Telescope has provided astronomers with the best observational evidence yet that globular clusters sort out stars according to their mass, governed by a gravitational billiard ball game between stars. Heavier stars slow down and sink to the cluster’s core, while lighter stars pick up speed and move across the cluster to its periphery. This process, called “mass segregation”, has long been suspected for globular star clusters, but has never before been directly seen in action.

Imagine trying to understand how a football game works based on just a few fuzzy snapshots of the game in play. This is the just the kind of challenge faced by astronomers trying to understand the dynamics of the swarm of stars in the globular star clusters that orbit our Milky Way Galaxy. The NASA/ESA Hubble Space Telescope has provided the best observational evidence to date that globular clusters sort stars according to their mass, governed by a gravitational billiard ball game between stars. Heavier stars slow down and sink to the cluster's core, while lighter stars pick up speed and move out across the cluster to its periphery. This process, called mass segregation, has long been suspected for globular star clusters, but has never been seen in action directly before.

A typical globular cluster contains several hundred thousand stars. Although the density of stars is very small at the outskirts of such clusters, near the centre it can be more than 10,000 times higher than in the local vicinity of our Sun. If we lived in such a crowded region of space, the night sky would be ablaze with 10,000 stars, all closer to us than the nearest star to the Sun, Alpha Centauri, which is 4.3 light-years away (or approximately 215,000 times the distance between Earth and the Sun). Just as bumps and jostles are much more likely in a crowded commuter train, so are encounters between stars in a densely populated cluster more likely than here in our quiet stellar backwater. These encounters can be as dramatic as collisions or even mergers. Theory predicts that the cumulative result of many such encounters is mass segregation, but the crowded conditions make it extremely difficult to identify individual stars accurately.

Astronomers needed Hubble’s pinpoint resolution to trace the motions of many thousands of stars in a single globular cluster. Highly accurate speeds have been measured for almost 15,000 stars at the very centre of the nearby globular cluster 47 Tucanae – one of the densest globular clusters in the southern hemisphere. 23 of these stars are of a very rare type known as "blue stragglers": unusually hot and bright stars thought to be the product of collisions between two normal stars.



This photo was taken by the Japanese astrophotographer Akira Fujii and shows a wide-angle view of the globular cluster 47 Tucanae and the Small Magellanic Cloud. Credit: Akira Fujii

The slower measured velocities of the blue straggler stars agree with the predictions of mass segregation. In particular, a comparison between blue stragglers (that have twice the mass of the average star) and other stars shows that, as expected, they do move more slowly than the more typical, lighter stars.

Georges Meylan of the École Polytechnique Federale de Lausanne (EPFL) in Sauverny, Switzerland and collaborators took ten sets of multiple images of the central region (within about 6 light-years of the centre) of 47 Tucanae using Hubble’s Wide Field and Planetary Camera 2 and the newer Advanced Camera for Surveys. Images were taken at regular intervals over nearly seven years. Extremely small position changes could be measured over time by carefully measuring the positions of as many as 130,000 stars in every one of these “snapshots”, revealing the motions of the stars across the sky.

The velocities of 15,000 stars were measured precisely. This is the largest sample of velocities ever gathered for a globular cluster in the Milky Way by any technique with any instrument. The results were also used to look for the gravitational pull of a black hole to check whether one exists in the cluster’s core. The measured stellar motions have ruled out the presence of a very massive black hole.

The study would have been impossible without Hubble’s sharp vision. From the ground, the smearing effect of the Earth’s atmosphere blurs the individual images of the numerous stars in the crowded cluster core. The typical angular motion of even the normal stars in the centre of 47 Tucanae was found to be just over one ten millionth of a degree (equivalent to the angular size of a 10 cent coin seen from 7,000 kilometres away) per year.

To take full advantage of these exquisite Hubble images, astronomers developed entirely new data analysis methods that eventually provided measurements of proper motions (velocities) that corresponded to changes in the positions of stars at the level of about 1/100th of a pixel (picture-element) on Hubble’s digital cameras.


Vital Signs

Safety: ICE on Cellphones: An Acronym for Emergencies

By ERIC NAGOURNEY

A simple acronym entered into people’s cellphone listings, ICE, can help emergency room doctors who are trying to track down a patient’s family.

It stands for In Case of Emergency, and a report presented at a recent gathering of the American Conference of Emergency Physicians said doctors should encourage their patients to start using it.

“We are always faced with situations where patients come into the emergency room and for one reason or another are not able to communicate with us,” said the author of the report, Dr. Dennis McKenna of the Albany Medical Center.

Traditionally, hospital workers have searched for a wallet and then tried to find relatives through the identification inside - a slow and not always successful method.

But with cellphones so common, Dr. McKenna said, hospitals now often search through cellphone address books for clues about whom to contact. While efforts to teach people to add an emergency contact listing have begun, doctors can do more to popularize the idea, he said.

For the study, researchers surveyed more than 400 emergency room patients and the people accompanying them and asked if they knew about ICE entries and if they would be willing to use them.

Although about a sixth of those surveyed said they had heard of the idea, less than a tenth had the listing on their phones. When hospital staff members offered instructions or help, however, more than half of those who had phones with them agreed to put the listing in.


Vital Signs

Performance: Researchers Test Meditation’s Impact on Alertness

By ERIC NAGOURNEY

Meditation is often credited with helping people feel more focused and energetic, but are the benefits measurable?

A new study suggests that they are. When researchers tested the alertness of volunteers, they found that the practice proved more effective than naps, exercise or caffeine. The results were presented at a recent conference of the Society for Neuroscience.

The researchers, led by Prashant Kaul of the University of Kentucky, took 12 students who did not meditate and taught them the basics in two short sessions.

Then, over a series of weeks, the students were asked to come in and take a test devised to measure skills like reaction time. The tests involved a series of visual cues on a display screen that the volunteers had to react to by pushing the correct button.

The students were asked to take the tests in mid- to late afternoon, when people tend to be sleepiest. They did so before and after 40 minutes of meditating, napping or exercising, or after taking caffeine. Napping produced poor results, presumably because of “sleep inertia,” the researchers said.

Caffeine helped, and exercise was unpredictable.

Earlier studies have found that people are awake while meditating but that their brains undergo changes similar to patterns found in sleep. Some studies have found that people who meditate a lot report sleeping less, so the researchers were curious to see if meditation could serve the same function as sleep. The results support the idea that it can.

In fact, when some of the students were asked to skip a night’s sleep and then take the test, the researchers said, meditation was even more helpful.

They said they did not know if caffeine and meditation combined would be even better.


Where the Doctors Recognize Leprosy

By DONALD G. McNEIL Jr.

The patient looked sheepish as he showed Louis N. Iannuzzi the new burn on his leg, the skin puckering where it was seared.

It was a classic injury for a leprosy victim, said Mr. Iannuzzi, the physical therapist for the leprosy clinic at Bellevue Hospital in New York. The man, a middle-aged Pakistani immigrant who works as a motorcycle mechanic, had not been able to feel a hot tailpipe when it touched him.

“He’s a tough case,” Mr. Iannuzzi said. “He’ll touch an engine manifold and not know it’s hot. He’s always kneeling, and he gets pressure ulcers.”



The mechanic was suffering from more advanced leprosy than most patients who come to the clinic, which allowed a reporter to visit on the condition that no patients be named.

The mechanic’s eyebrows were gone, his nose had flattened slightly, and his toes were just nubs - not a result of dropping off, as is popularly believed, but because they had been injured so often that the body had reabsorbed some of the bone.



A patient’s feet are cared for in the leprosy clinic at Bellevue Hospital. Loss of feeling in toes can lead to repeated injuries.

Despite the notion that leprosy is inevitably disfiguring, he was the only patient at the New York Hansen’s Disease Clinic at Bellevue on a recent Tuesday who looked unusual. Although the disease is famous for the “leonine faces” of its victims, modern antibiotics can prevent that effect.

None of the Bellevue patients have leprosy as a consequence of AIDS treatment, said the clinic’s director, Dr. William Levis. But that could change, Dr. Levis said, because the clinic draws immigrants from countries where both diseases are widespread.

The clinic - one of 16 in a national network overseen by the Department of Health and Human Services - has about 400 patients and sees about 25 of them on two mornings a week in the hospital’s dermatology department. Most of the work involves adjusting drug regimens and treating the consequences of long-lasting nerve damage like the motorcycle mechanic’s.

Almost all American leprosy cases are in immigrants, and on a recent morning at the clinic, the patients were from Pakistan, India, Guyana, Brazil, the Philippines and the Dominican Republic. But a handful of cases have probably been transmitted domestically, experts believe, so as of 2003, leprosy was officially considered endemic to the Northeastern United States. (It existed in the South in the 19th century.)

The mechanic has lived in the United States for 20 years. When he first went to a hospital in Pakistan, about 25 years ago, he said, “they said I have nothing.”

But the disease grew gradually worse, he said, deadening his hands so that he frequently cut himself, and covering his face with bumps and making his eyebrows fall out.

About five years ago, he said, he was at last sent to the Bellevue clinic.

“Now, thanks God, I am 1,000 percent better,” he said.

Dr. Levis said the disease often went undiagnosed. “We’ve had patients see up to 16, 17 physicians before they’re sent here,” he said. “I had one patient, a Chinese woman who’d lived in Brooklyn for 40 years. She had severe loss of feeling, she was going blind, she wasn’t diagnosed in all that time. Doctors just don’t recognize it.”

Another patient, an engineering student from Guyana, said that when he went to an emergency room one night after a reaction to antibiotics and explained what he was being treated for, “everybody knew nothing.”

“Everybody that came to see me that night was basically dressed in a spacesuit,” the student added.

Only when the hospital’s infection-control chief was consulted the next day, he said, did the staff stop treating him as if he were infectious. Leprosy is transmitted only through long, close contact, and is not thought to be transmissible at all once a patient has been on antibiotics for three days.

The student said he looks much better now. His earlobes, once distended by nodules, have shrunk to near-normal size. The nerve damage has abated, he rarely stumbles and he has regained enough feeling in his feet to be able to drive again. His girlfriend and his family are understanding. At work and at school, he said, “they notice the scarring, the nodules, but they don’t ask.”

“I say I’m being treated and getting better,” he went on. “I don’t say what for.” He fears explaining, he added, “because they’d say, ‘Wow, I can’t believe it.’ ”

“They’d look at me in a different way,” he said. “And I imagine they’d be afraid of me.”

Dr. Levis concurred. Though the disease is curable, and not transmissible when a victim is in treatment, the special stigma of the word “leper” remains.

“People used to be warehoused for life for this,” Dr. Levis said. “We don’t recommend revealing it.”



Government Panel Recommends Shingles Vaccine

By THE ASSOCIATED PRESS

An influential government advisory panel recommended that Americans 60 and older be vaccinated against shingles, an excruciatingly painful rash caused by the same virus that causes chickenpox. The recommendations of the panel, the Advisory Committee on Immunization Practices, are usually accepted by federal health officials, and they influence insurance companies’ decisions on which vaccinations to cover. No vaccine was available until May, when the Food and Drug Administration licensed Zostavax, made by Merck & Company. The vaccine is a modified version of Merck’s chickenpox vaccine for children, with a live virus that is 14 times more potent.



Doctors Say Slow Action on Stents Leads to Heart Deaths

By BARNABY J. FEDER

WASHINGTON, Oct. 26 - Although a few thousand Americans might be dying needlessly from overuse of heart stents, prominent cardiologists said Thursday that far more are being killed each year by the failure of doctors to promptly clear coronary arteries and install stents when patients arrive at a hospital during a heart attack.

Stents are tiny mesh cylinders that are placed in arteries to keep blood flowing after blood vessels have been cleared of plaque.

The doctors, at a convention here, noted that study after study has shown that clearing the blockages through the technique used by the stenters increases the survival rates of people who have had heart attacks, compared with relying on clot-busting drugs like tPA and streptokinase.

But tens of thousands of Americans each year go to hospitals that do not have the catherization labs where stents are implanted. Instead, they are given drugs rather than being transferred to other medical centers that have stenting capabilities.

And at small hospitals that do have the capability, but do not have stenting experts on hand in the evening or on weekends, patients often receive the drugs if they do not arrive during weekday hours.

“Survival should not be dependent on going to the right hospital,” said Dr. William O’Neill , a nationally known cardiologist who recently became executive dean of clinical affairs at the University of Miami School of Medicine.

He and other doctors have called for a nationwide policy of transferring patients, if necessary, so they can be quickly stented, an approach shown to be effective in Sweden and Denmark.

The stent doctors, mostly specialists called interventional cardiologists, are not alone on the issue. The American Heart Association has also been pushing for more cooperation among hospitals to ensure that more emergency stenting occurs.

Dr. O’Neill is here for the annual gathering of doctors who specialize in use of stents and similar technologies for treating heart disease.

Much of the talk at this meeting, the Transcather Cardiovascular Therapeutics show at the Washington Convention Center, has involved emerging evidence that the newest and most popular type of stents - ones with drug coatings - pose a long-term risk of potentially fatal blood clots.

For Dr. O’Neill and some others here, that risk does not offset the far greater dangers they say that people who have had heart attacks face if they do not get immediate artery-clearing treatment.

The rescue procedure begins with angioplasty, in which a catheter is inserted in the patient’s groin and threaded through the circulatory system to the blockage. A balloon is then inflated to clear the plaque.

In 90 percent of the cases, the next step is inserting a stent to keep the artery open while the patient recovers. But the more crucial step, Dr. O’Neill and others say, is the balloon inflation.

The type of heart attacks that occur when fatty plaques break loose in arteries and shut down blood flow to the heart is known as acute myocardial infarction. It strikes about 400,000 Americans annually and is a leading cause of death in many other developed nations.

The model for what should be done throughout the nation, Dr. O’Neill said, has been set up by the Minneapolis Heart Institute at Abbott Northwestern Hospital. Dr. Timothy Henry, who organized that system, told the audience in a crowded meeting room Thursday afternoon that he was tired of hearing that such programs could only be set up only in small countries like Denmark.

Dr. Henry’s group began in 2002 by developing a standardized treatment plan for hospitals within 60 miles. A second ring reaching out 120 miles has a second plan, using different drugs to help patients survive until they can be transferred to the Heart Institute’s high-volume catheter lab or other primary hospitals. More than two-thirds are ferried by air.

Dr. Henry presented data showing that the system has been able to produce the same mortality rates for patients within all the zones, even though it often takes as long as two hours for those furthest away to get their blockages cleared and stented after reaching the initial hospital.



Dostları ilə paylaş:
1   2   3   4   5   6   7   8


Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©muhaz.org 2017
rəhbərliyinə müraciət

    Ana səhifə