Stellar Opposites: Sky survey reveals new halo of stars
The Milky Way galaxy possesses a distinct outer halo that orbits in the opposite direction from its inner halo and the rest of the galaxy, researchers say. This second halo contains some of the most primitive stars in the universe, offering new evidence about how the galaxy formed.
Some scientists had previously suspected that a portion of the stars in the Milky Way travel in a different direction from the rest. But data on such stars were too sparse to conclude that an entire second halo existed.
Now, an international team of scientists including Timothy Beers of Michigan State University in East Lansing has discovered stronger evidence for a double halo. Beers and his colleagues analyzed more than 20,000 stars as part of the Sloan Digital Sky Survey, an astronomical effort to create a three-dimensional map of about a million galaxies.
The scientists noticed that stars more than 50,000 light-years away from the center of the Milky Way move in the opposite direction from closer ones, have distinctive chemical compositions, and travel around the galaxy at different speeds.
"It was certainly a surprise to my team how well the two populations were resolved from one another with the new data," says Beers.
Stars in the Milky Way's inner disk, where the Earth is located, orbit at 200 kilometers per second (kps). The inner halo moves in the same direction as this disk, but at 25 kps. Stars in the outer halo appear to speed around the galaxy in the opposite direction at about 50 kps.
Beers observes that the existence of small, metal-poor stars in the outer halo suggests a new story of the evolution of the galaxy.
The dense central region of the galaxy and the inner halo that surrounds it probably formed first, says Beers, as heavy, metal-rich stars clumped together to create the Milky Way. Dwarflike galaxies left behind merged together later to create the outer halo, he hypothesizes.
Though this halo formed after the inner halo, its stars are deficient in heavy metals, implying that they are older. These stars likely formed from gas that existed early in the universe, before all elements existed plentifully, says Beers.
The new findings, which appear in the Dec. 13 Nature, do not alter the inference that an invisible form of dark matter occupies the galaxy's halo region, Beers says. The stars in both halos are so far away from the center of the galaxy that their orbital velocity requires more gravity than visible matter supplies.
Rosie Wyse of Johns Hopkins University in Baltimore says the new data provide compelling statistical evidence in support of a distinct outer halo of the Milky Way. But she says questions remain about the nature and formation of the halo.
For example, the Milky Way's central bulge contains stars as old as those identified in the outer halo. Wyse says scientists must understand the relationship between this bulge and the outer halo to tell the full history of the galaxy.
"We need future, large, dedicated spectroscopic surveys of stars in our galaxy to answer the many outstanding questions," she says.
First-degree relatives - parents, siblings and children - of people with Parkinson's disease are about 50 percent more likely than relatives of healthy people to suffer depression or anxiety, a new study reports.
That relatives of people with Parkinson's have a higher risk of neurological disorders is well known, but their risk for psychiatric disorders has been unclear.
Researchers studied 1,000 first-degree relatives of 162 people with Parkinson's and 850 first-degree relatives of 147 healthy people. The team found a 45 percent increased risk for depressive disorders and a 55 percent increased risk for anxiety disorders among the Parkinson's relatives.
The study, published in the December issue of The Archives of General Psychiatry, also found that the earlier the onset of Parkinson's, the more likely a relative was to suffer depression.
ANOREXIA AND HORMONES Anorexia is 10 times as common in women as in men, and a new study suggests that female sex hormones in the womb may play a part.
Researchers used the Swedish twin registry to study 4,226 pairs of female twins, 3,451 pairs of male twins and 4,478 pairs of opposite-sex twins, all born from 1935 to 1958. They found 51 cases of anorexia among the female twins, 3 among the male twins and 36 among the opposite-sex pairs. The study was published in the December issue of The Archives of General Psychiatry.
As expected, the risk of anorexia in female twins was higher than in male twins. But in the opposite-sex twins, 16 anorexia cases, almost half, were in males. In other words, the male member of a male-female twin pair had a risk for anorexia statistically no different from the risk among females.
Studies have shown that shared family environment has little effect on the development of anorexia. Instead, the researchers theorize, the shared intrauterine environment of male-female twin pairs is what leads to the increased risk for the males. Female sex hormones may influence neurodevelopment and later risk for anorexia, they suggest, and males in that uterine environment would be similarly affected.
TAME A CHILD'S COUGH WITH HONEY A spoonful of honey might quiet a child's cough more effectively and safely than the most common over-the-counter cough medicine.
Researchers tested 105 children 2 to 18 with coughs from upper-respiratory infections, dividing them randomly into three groups. One received no treatment. The other received a remedy: one or two teaspoons of buckwheat honey, depending on age, or an age-appropriate dose of honey-flavored dextromethorphan. The study was supported by a grant from the National Honey Board, an industry-backed agency of the U.S. Department of Agriculture.
Using questionnaires filled out by the parents, the scientists measured cough frequency and severity, and the effect on the children's and parents' sleep. By all measures, honey provided the greatest relief.
Honey, the authors wrote in the December issue of The Archives of Pediatric and Adolescent Medicine, has well-established antioxidant and anti-microbial effects, and it might be that sweet substances of any kind help dissolve mucus in the airways and soothe the back of the throat.
In October, a U.S. Food and Drug Administration advisory panel recommended a ban on over-the-counter cold medicine intended for children under age 6.
Ian Paul, the lead author and an associate professor of pediatrics at Penn State, said parents should consider honey "as an alternative to cough medicine for children over age 1." In rare cases, honey can cause infantile botulism in children under 1.
Now an international group of researchers has found at least one reason why. BRCA1 inactivates a tumor suppressor gene known as PTEN.
Mutations occur spontaneously, but most organisms have mechanisms that can prevent the damage they might cause. PTEN has instructions to produce a protein that stops the uncontrolled cell growth of cancer.
BRCA1, the scientists reported online Sunday in Nature Genetics, prevents PTEN from doing its work.
The researchers found that inactivating the PTEN gene in mice led to the formation of the malignant tumor associated with BRCA1 mutations. Then they examined PTEN in nonhereditary breast tumors from 297 patients and tumors from 34 women who had inherited the BRCA1 mutation. In most cases, the protein that PTEN produces was undetectable in tumor cells, but clearly present in nearby normal cells.
PTEN might be a target for chemotherapy. "I am cautiously optimistic," said Ramon Parsons, the lead researcher and a professor of pathology at Columbia, "that within the next five years we'll be using drugs that are effective on the PTEN pathway."
For one heart patient, there will be no more agonizing over whether the implanted device meant to save his life might kill him instead.
On Tuesday, two months after Medtronic warned doctors and nearly a quarter-million patients that a wire, or lead, connecting their electronic defibrillators to their hearts might break, the 48-year-old patient had the lead and defibrillator removed and replaced. It required a painstaking 90-minute operation here at Morristown Memorial Hospital.
But thousands of other patients with failing hearts remain trapped in doubt. Their defibrillators are meant to deliver electric shocks to restore normal rhythms if their hearts start beating chaotically. Should they have the potentially faulty wire, or lead, removed — or leave it in place and hope it does not fail?
And if they do have it extracted, how will they pay for it? Medtronic is limiting its contribution to only a replacement lead and $800 toward each procedure, which can cost $12,500 or more. So far insurers are deciding whether to cover the replacement operation on a case-by-case basis, unless the lead has already fractured.
"This has been a nightmare," said the Morristown patient. He described his fears and agreed to let a reporter observe the procedure on the condition that his identity remained private.
The lead, called the Fidelis, is a spaghetti-thin plastic tube enclosing electrical wires and sensors. The risks of the patient's operation, besides the possibility for infection, included potential perforation of his heart and the veins in his chest. There was also a slight danger of damaging the heart valve through which the lead had been threaded in 2005, when doctors had screwed the tip into muscle in the bottom of the right ventricle of his heart. As it turned out, the procedure went relatively smoothly. Dr. Christopher Magovern, the surgeon who performed the procedure, said the patient would probably soon be back on the job as a supervisor for heating and air-conditioning projects.
Most Fidelis users will not end up needing such an operation, although all have been advised to check with their doctors. But the number of patients with the potentially faulty leads has made this the most widespread problem yet involving a heart device. And the episode has drawn renewed scrutiny to the way medical devices — particularly heart leads — are approved and regulated in this country. The episode has led to investigations in both houses of Congress.
"It seems like a good time to figure out where we are in regulating leads and what we can do better," said Daniel Schultz, director of the Food and Drug Administration's center for devices and radiological health.
Schultz will head an FDA delegation at a meeting in Boston on Thursday. The conference was arranged by Dr. William H. Maisel, the director of the Medical Device Safety Institute, a research arm of the Beth Israel Deaconess Medical Center in Boston. At the session, regulators, doctors and device companies plan to share information and proposals for changing the way heart devices are approved and then monitored after they reach the market.
The $5.6 billion global market for defibrillators stalled last year and has rebounded only slightly since then. The industry has been clouded by design defects and sometimes lax quality control, and by product recalls that included Guidant defibrillators in 2005 that were linked to seven deaths.
Sales in the United States, which accounted for more than $4 billion of last year's total, have also been damped by data indicating that as many as 80 percent of patients getting defibrillators never end up needing a life-saving jolt from them. The devices can cost $30,000 or more.
On Oct. 15 Medtronic reported that the Fidelis lead was fracturing at a higher rate than the Quattro, a thicker lead it had been rapidly displacing since being introduced in 2004. Data suggested that 2.3 percent of Fidelis implants fracture within 30 months, meaning more than 5,000 likely malfunctions among the estimated 235,000 patients with the leads.
Medtronic said that Fidelis fractures, which could prevent the defibrillator from firing when needed, had been linked in reports it received to five deaths. The fractures, which disrupted the lead's sensing mechanism, also caused numerous unnecessary shocks.
So far, the business impact has been less that Medtronic had originally forecast. Last month, the company — which gets close to 40 percent of its revenue from defibrillators, heart pacemakers and related products — said overall sales had risen 2 percent in the past year to $3.12 billion in its fiscal second quarter ending Oct. 26.
Medtronic said the 11 days of business in the quarter after the Fidelis warning had resulted in $130 million in lost sales. There was an additional $31 million in write-offs and other costs, like mailing notifications to patients and doctors. The company has directly contacted 175,000 patients about Fidelis and "virtually all of the rest" through their hospitals and doctors, according to Robert Clark, a spokesman.
The company moved so swiftly to shift customers back to the older Quattro lead that it now expects the total lost sales to end up below the $150 million to $250 million shortfall it had forecast.
"The data supplied by companies always underestimates failure rates, but if no other shoe drops, Fidelis won't be an issue," said Dr. Raymond Schaerf, a surgeon at Providence St. Joseph Medical Center in Burbank, California.
Such thinking has buoyed Medtronic's stock. The shares had fallen about 20 percent, to $45.25, on Nov. 19 from the $56.33 level at which they closed Oct. 12, the last trading day before the recall was announced. But more recently the stock has rebounded somewhat, closing Wednesday at $49.99, up 25 cents.
One reason for Wall Street's relief is the widespread agreement among doctors that most patients whose Fidelis leads have not already fractured are better off simply leaving them in place. The caveat is that the defibrillators need to be reprogrammed and monitored, to improve the odds of catching any developing fractures early.
Schaerf, who has been extracting device leads for various reasons since 1990, said he had removed the Fidelis from six patients in response to the warning in October. But he has also turned away 10 Fidelis patients who wanted replacement procedures that he thought did not justify the risk.
Others, like Dr. Robert Rea, the director of implantable devices at the Mayo Clinic in Rochester, Minnesota, said that many patients are reassured by wireless monitoring technology embedded in many Medtronic defibrillators. Devices with that technology can be remotely checked for signs of malfunctions via the Internet, through a free Medtronic service called CareLink.
But some patients and their families are seeking second opinions. A woman outside Detroit, who has been sharing her concerns with a reporter, said last week that her husband had his Fidelis lead reprogrammed to safer settings by a Medtronic representative during a recent visit to the doctor who had implanted the defibrillator. But she said she still planned to take her husband for a second checkup at the Cleveland Clinic by Dr. Bruce Wilkoff, one of the nation's busiest lead extractors.
"Maybe nothing will happen, but if it does I want him to be a patient of someone known to be a high-volume expert," the woman said. She requested anonymity for herself and her husband because she did not want to risk offending his local doctor.
Medtronic said in October that it would provide free replacement leads and up to $800 toward medical expenses. But that offer covered only patients with leads that had actually fractured.
Last month, the company extended that coverage to patients without fractures, in cases where doctors advise removing the leads because of the patient's specific medical condition. But in the end, Clark said, the group of patients without fractures who nonetheless need leads removed should be "very small."
One potentially vulnerable group includes patients with a congenital thickening of the heart muscle known as hypertrophic cardiomyopathy. Their condition can put more stress on the lead, which may increase the likelihood a lead fracture. And they are usually younger than the typical heart-failure patient, so they face higher odds of eventual fractures simply because they are likely to have the leads in place longer.
Dr. Robert Hauser, a Minneapolis cardiologist, is trying to organize a registry of major hospitals to track the performance of Fidelis and other leads in cardiomyopathy patients with defibrillators. He says he hopes to have preliminary data from at least eight hospitals in January.
Doctors are also concerned about patients who have dual-purpose implants that serve as both defibrillators and pacemakers and that rely on Fidelis leads for both functions. The patient Magovern treated on Tuesday had such a Medtronic device. Because of his cardiomyopathy, the patient had undergone previous heart operations that left him dependent on a pacemaker and later a dual-purpose implant to continuously stimulate his heart.
For such patients, a fracture that stops Fidelis from gently pacing the heart is an even more certain death sentence, Magovern said, than a fracture that stops it from delivering a defibrillating shock. Still, Magovern and the implant specialists he works with at Morristown Memorial, are advising most patients not to rush to have their leads removed.
And he, for one, is practicing what he preaches. Magovern's wife has a defibrillator with a Fidelis lead. For now, she is leaving it in place.
Parasites that breed in fish farms kill so many juvenile wild salmon that they threaten the survival of fish populations in some rivers and streams, Canadian researchers are reporting.
The researchers studied pink salmon in an area north of Vancouver Island, British Columbia. But they said their findings, and earlier studies of the effects of farm-borne parasites on wild salmon, are so damning that they challenge the practice of net-pen aquaculture over all. In these farms, fish grow in anchored underwater cages that function as feedlots. The parasitic sea lice prey on juvenile wild salmon when they swim past these fish pens on their way from inland rivers to the ocean.
The researchers, from the University of Alberta and elsewhere, are reporting their findings in Friday's issue of the journal Science.
But not everyone accepts this view of sea lice. According to Fisheries and Oceans Canada, a government agency responsible for developing aquaculture while safeguarding wild fish stocks, "no direct cause and effect" has been established between sea lice prevalence and salmon mortality. The agency says sea lice prevalence is "a complex ecosystem puzzle" in need of further study.
Brian Riddell, an ecologist with the agency, said in an interview that factors including fishing practices, logging and climate change can affect salmon abundance and added that it would be a mistake "to become overly focused on a single point."
The researchers concede their calculations show juvenile salmon death rates from sea lice infestation can range widely, but said they were typically about 80 percent. At that rate, they calculated that some local populations will be effectively extinct in four salmon generations - about eight years.
"If nothing changes, we are going to lose these fish," said Martin Krkosek, a fisheries ecologist at the University of Alberta who led the work.
Ray Hilborn, a fisheries biologist from the University of Washington who was not involved in the study but is familiar with its findings, called the data persuasive and said they raise "serious concerns about proposed aquaculture for other species such as cod, halibut and sablefish."
"These high density fish farms are natural breeding grounds for pathogens," not necessarily limited to sea lice, he said in an interview. He noted, however, that the study involved pink salmon, not species like sockeye or chinook, which are usually larger, and presumably less vulnerable to sea lice. Pink salmon are the most abundant salmon species in the northern Pacific.
The researchers said they used Canadian government fishing data from 1970 to the present on pink salmon (Oncorhynchus gorbuscha) to construct models of fish abundance in the Broughton Archipelago, an area that has seen dramatic increases in fish farms.
Sea lice normally occur in the open ocean, where they bite fish and feed on them, creating open lesions that can interfere with the fishes' osmotic balance with seawater. In nature, juvenile salmon do not ordinarily encounter them until they are large enough to survive a modest infestation. But the parasites proliferate in fish pens, which are typically placed in near-shore areas juvenile fish must traverse on their way to sea.
As these and other researchers have previously reported, the young fish, small and thin-skinned, can become so heavily infested they turn into secondary sources of infection when they reach the ocean, before succumbing to the parasites themselves. But this study is the first to predict such large scale losses of wild fish from farm-bred sea lice.
Mark Lewis, a mathematic ecologist at the University of Alberta and another of the researchers, said in a statement issued by the university that containing the farms in closed pens or moving them offshore, away from rivers, might reduce the problem.
Dr. Riddell said the Canadian government is working with fish farmers to reduce sea lice infestations. One idea, he said, is to feed the penned fish medicated food. "That is something we know can be effective," he said. But, he added, that approach raises other environmental concerns. "Anything not taken up by the fish goes to the bottom of the ocean or can leach into the water, potentially affecting other marine life," he said.
Daniel Pauly, a fisheries researcher at the University of British Columbia who was not connected to the work, said in a statement that if fish farm entrepreneurs do not act to reduce sea lice infestations they will, in effect, shift the cost of their operations "on the wild salmon and the public."
The authors of the new report said their findings show action should be taken quickly. It might take 10 salmon generations to accumulate large sets of data on the effects of farm-related parasite infestations, they said in their report, and that "greatly exceeds the predicted time to extinction."
Pregnant women do not tip over, and researchers say an evolutionary curve has a lot to do with the reason.
Anthropologists studying the human spine have found that women's lower vertebrae evolved in ways that reduce back pressure during pregnancy, when the mass of the abdomen grows by nearly one-third and the center of mass shifts forward considerably. That increases pressure on the spinal column, strains the muscles and generally reduces stability.
Even without the benefit of advanced study in biomechanics, women tend to deal with the shift - and avoid tumbling over like a bowling pin - by leaning back. But the solution to one problem creates another, since it puts even more pressure on the spine and muscles.
And that, report researchers from Harvard University and the University of Texas in the current issue of the journal Nature, is where evolution enters the story.
The lower spine in humans had already developed a unique forward curve that helps compensate for the extra pressures that arose when the primate ancestors went from moving around on four limbs to walking upright. Researchers looked for an additional mechanism that might have compensated for the increased strain of pregnancy as well.
What they found, said Katherine Whitcome, a post-doctoral fellow at Harvard and the lead author of the paper, was evidence that evolution had produced a stronger and more flexible lower spine for women. After studying 19 pregnant subjects, Whitcome found that the lumbar, or lower back, curve in women extends across three vertebrae, as opposed to two in men. And the connecting points between vertebrae are relatively larger in women and shaped differently in ways that make the stack more stable and less prone to bones shifting out of alignment or breaking.
Since the engine of evolution runs on the passage of genes from one generation to the next, pregnancy is a critical moment. Without that adaptation, Whitcome said, women would have been in considerably greater pain during pregnancy and might not have been able to forage effectively or escape predators, ending the pregnancy and the genetic line as well.
Working at the University of Texas with Liza Shapiro, an associate professor of anthropology who studies the primate spine, Whitcome found that the differences between male and female spines do not show up in chimpanzees. That suggested that the changes occurred in response to the problems caused by walking upright.
When she moved on to Harvard and started working with Daniel Lieberman, an anthropologist with expertise in primate fossils, she was able to examine two sets of fossilized vertebrae for the telltale signs of evolved flexibility. Of the two samples, she found the three-vertebra arrangement in one and not in the other. As it happened, separate evidence from those skeletons suggested strongly that the extra-curvy spine belonged to a female and the other belonged to a male.
"It was very exciting" to have the fossilized pieces of the puzzle fall into place, Whitcome said.
As solutions go, the forward spine is only partly successful, Shapiro said, since women still commonly complain of back trouble and pain during pregnancy. Even the basic forward curve that promotes balance in upright walking is "not a structurally ideal solution," she said, since it can lead to instability and even fractured vertebrae.
And that is the difference between the way that evolution works and the way that actual designers do their job, Whitcome said: nature tinkers.
"A designer wouldn't build something that has a tendency to fracture your vertebrae," she said.
For natural selection to favor one feature over another, "it doesn't have to be an ideal solution," she said. "It just has to be better."
If evolution provided relief for women in pregnancy, one might ask, what about the equally awkward morphology of men with beer guts?
"You're not the first one to ask this," Shapiro said with a laugh, and said that their research shows that "men would not be as well adapted to a beer gut than a woman."
Whitcome noted that in terms of the time that the evolutionary shift occurred, some two million years ago, "finding extra calories wasn't likely," so an early hominid primate with a potbelly would have been quite a rarity.
Anthropology has extensively explored the evolution of the female hip bones, which expanded over time to accommodate the evolutionary growth of the heads of human babies. But Shapiro said that pregnancy and the lower spine constituted new ground for evolutionary biology.
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