SAN DIEGO — Mice yanked out of their community and held in solitary isolation show signs of brain damage.
After a month of being alone, the mice had smaller nerve cells in certain parts of the brain. Other brain changes followed, scientists reported at a news briefing November 4 at the annual meeting of the Society for Neuroscience.
It’s not known whether similar damage happens in the brains of isolated humans. If so, the results have implications for the health of people who spend much of their time alone, including the estimated tens of thousands of inmates in solitary confinement in the United States and elderly people in institutionalized care facilities.
The new results, along with other recent brain studies, clearly show that for social species, isolation is damaging, says neurobiologist Huda Akil of the University of Michigan in Ann Arbor. “There is no question that this is changing the basic architecture of the brain,” Akil says. Neurobiologist Richard Smeyne of Thomas Jefferson University in Philadelphia and his colleagues raised communities of multiple generations of mice in large enclosures packed with toys, mazes and things to climb. When some of the animals reached adulthood, they were taken out and put individually into “a typical shoebox cage,” Smeyne said.
This abrupt switch from a complex society to isolation induced changes in the brain, Smeyne and his colleagues later found. The overall size of nerve cells, or neurons, shrunk by about 20 percent after a month of isolation. That shrinkage held roughly steady over three months as mice remained in isolation. To the researchers’ surprise, after a month of isolation, the mice’s neurons had a higher density of spines — structures for making neural connections — on message-receiving dendrites. An increase in spines is a change that usually signals something positive. “It’s almost as though the brain is trying to save itself,” Smeyne said.
But by three months, the density of dendritic spines had decreased back to baseline levels, perhaps a sign that the brain couldn’t save itself when faced with continued isolation. “It’s tried to recover, it can’t, and we start to see these problems,” Smeyne said.
The researchers uncovered other worrisome signals, too, including reductions in a protein called BDNF, which spurs neural growth. Levels of the stress hormone cortisol changed, too. Compared with mice housed in groups, isolated mice also had more broken DNA in their neurons.
The researchers studied neurons in the sensory cortex, a brain area involved in taking in information, and the motor cortex, which helps control movement. It’s not known whether similar effects happen in other brain areas, Smeyne says.
It’s also not known how the neural changes relate to mice’s behavior. In people, long-term isolation can lead to depression, anxiety and psychosis. Brainpower is affected, too. Isolated people develop problems reasoning, remembering and navigating.
Smeyne is conducting longer-term studies aimed at figuring out the effects of neuron shrinkage on thinking skills and behavior. He and his colleagues also plan to return isolated mice to their groups to see if the brain changes can be reversed. Those types of studies get at an important issue, Akil says. “The question is, ‘When is it too far gone?’”
A proton’s mass is more than just the sum of its parts. And now scientists know just what accounts for the subatomic particle’s heft.
Protons are made up of even smaller particles called quarks, so you might expect that simply adding up the quarks’ masses should give you the proton’s mass. However, that sum is much too small to explain the proton’s bulk. And new, detailed calculations show that only 9 percent of the proton’s heft comes from the mass of constituent quarks. The rest of the proton’s mass comes from complicated effects occurring inside the particle, researchers report in the Nov. 23 Physical Review Letters.
Quarks get their masses from a process connected to the Higgs boson, an elementary particle first detected in 2012 (SN: 7/28/12, p. 5). But “the quark masses are tiny,” says study coauthor and theoretical physicist Keh-Fei Liu of the University of Kentucky in Lexington. So, for protons, the Higgs explanation falls short.
Instead, most of the proton’s 938 million electron volts of mass is due to complexities of quantum chromodynamics, or QCD, the theory which accounts for the churning of particles within the proton. Making calculations with QCD is extremely difficult, so to study the proton’s properties theoretically, scientists rely on a technique called lattice QCD, in which space and time are broken up into a grid, upon which the quarks reside. Using this technique, physicists had previously calculated the proton’s mass (SN: 12/20/08, p. 13). But scientists hadn’t divvied up where that mass comes from until now, says theoretical physicist André Walker-Loud of Lawrence Berkeley National Laboratory in California. “It’s exciting because it’s a sign that … we’ve really hit this new era” in which lattice QCD can be used to better understand nuclear physics.
In addition to the 9 percent of the proton’s mass that comes from quarks’ heft, 32 percent comes from the energy of the quarks zipping around inside the proton, Liu and colleagues found. (That’s because energy and mass are two sides of the same coin, thanks to Einstein’s famous equation, E=mc2.) Other occupants of the proton, massless particles called gluons that help hold quarks together, contribute another 36 percent via their energy.
The remaining 23 percent arises due to quantum effects that occur when quarks and gluons interact in complicated ways within the proton. Those interactions cause QCD to flout a principle called scale invariance. In scale invariant theories, stretching or shrinking space and time makes no difference to the theories’ results. Massive particles provide the theory with a scale, so when QCD defies scale invariance, protons also gain mass.
The results of the study aren’t surprising, says theoretical physicist Andreas Kronfeld of Fermilab in Batavia, Ill. Scientists have long suspected that the proton’s mass was made up in this way. But, he says, “this kind of calculation replaces a belief with scientific knowledge.”
Locust: The Opera finds a novel way to doom a soprano: species extinction.
The libretto, written by entomologist Jeff Lockwood of the University of Wyoming in Laramie, features a scientist, a rancher and a dead insect. The scientist tenor agonizes over why the Rocky Mountain locust went extinct at the dawn of the 20th century. He comes up with hypotheses, three of which unravel to music and frustration.
The project hatched in 2014. “Jeff got in his head, ‘Oh, opera is a good way to tell science stories,’ which takes a creative mind to think that,” says Anne Guzzo, who composed the music. Guzzo teaches music theory and composition at the University of Wyoming. locust brought famine and ruin to farms across the western United States. “This was a devastating pest that caused enormous human suffering,” Lockwood says. Epic swarms would suddenly descend on and eat vast swaths of cropland. “On the other hand, it was an iconic species that defined and shaped the continent.” Lockwood had written about the locust’s mysterious and sudden extinction in the 2004 book Locust , but the topic “begged in my mind for the grandeur of opera.” He spent several years mulling how to create a one-hour opera for three singers about the swarming grasshopper species. Then the ghost of Hamlet’s father, in the opera “Amleto,” based on Shakespeare’s play, inspired a breakthrough. Lockwood imagined a spectral soprano locust, who haunted a scientist until he figured out what killed her kind.
To make one locust soprano represent trillions, Guzzo challenged her music theory class to find ways of evoking the sound of a swarm. They tried snapping fingers, rattling cardstock and crinkling cellophane. But “the simplest answer was the most elegant,” Guzzo says — tasking the audience with shivering sheets of tissue paper in sequence, so that a great wave of rustling swept through the auditorium.
For the libretto, Lockwood took an unusually data-driven approach. After surveying opera lengths and word counts, he paced his work at 25 to 30 words per minute, policing himself sternly. If a scene was long by two words, he’d find two to cut. He wrote the dialogue not in verse, but as conversation, some of it a bit professorial. Guzzo asked for a few line changes. “I just couldn’t get ‘manic expressions of fecundity’ to fit where I wanted it to,” she says. Eventually, the scientist solves the mystery, but takes no joy in telling the beautiful locust ghost that humans had unwittingly doomed her kind by destroying vital locust habitat. For tragedy, Lockwood says, “there has to be a loss tinged with a kind of remorse.”
The opera, performed twice in Jackson, Wyo., will next be staged in March in Agadir, Morocco.
Martha Carlin married the love of her life in 1995. She and John Carlin had dated briefly in college in Kentucky, then lost touch until a chance meeting years later at a Dallas pub. They wed soon after and had two children. John worked as an entrepreneur and stay-at-home dad. In his free time, he ran marathons.
Almost eight years into their marriage, the pinky finger on John’s right hand began to quiver. So did his tongue. Most disturbing for Martha was how he looked at her. For as long as she’d known him, he’d had a joy in his eyes. But then, she says, he had a stony stare, “like he was looking through me.” In November 2002, a doctor diagnosed John with Parkinson’s disease. He was 44 years old.
Carlin made it her mission to understand how her seemingly fit husband had developed such a debilitating disease. “The minute we got home from the neurologist, I was on the internet looking for answers,” she recalls. She began consuming all of the medical literature she could find.
With her training in accounting and corporate consulting, Carlin was used to thinking about how the many parts of large companies came together as a whole. That kind of wide-angle perspective made her skeptical that Parkinson’s, which affects half a million people in the United States, was just a malfunction in the brain.Martha Carlin married the love of her life in 1995. She and John Carlin had dated briefly in college in Kentucky, then lost touch until a chance meeting years later at a Dallas pub. They wed soon after and had two children. John worked as an entrepreneur and stay-at-home dad. In his free time, he ran marathons.
Almost eight years into their marriage, the pinky finger on John’s right hand began to quiver. So did his tongue. Most disturbing for Martha was how he looked at her. For as long as she’d known him, he’d had a joy in his eyes. But then, she says, he had a stony stare, “like he was looking through me.” In November 2002, a doctor diagnosed John with Parkinson’s disease. He was 44 years old.
Carlin made it her mission to understand how her seemingly fit husband had developed such a debilitating disease. “The minute we got home from the neurologist, I was on the internet looking for answers,” she recalls. She began consuming all of the medical literature she could find.
With her training in accounting and corporate consulting, Carlin was used to thinking about how the many parts of large companies came together as a whole. That kind of wide-angle perspective made her skeptical that Parkinson’s, which affects half a million people in the United States, was just a malfunction in the brain. “I had an initial hunch that food and food quality was part of the issue,” she says. If something in the environment triggered Parkinson’s, as some theories suggest, it made sense to her that the disease would involve the digestive system. Every time we eat and drink, our insides encounter the outside world.
John’s disease progressed slowly and Carlin kept up her research. In 2015, she found a paper titled, “Gut microbiota are related to Parkinson’s disease and clinical phenotype.” The study, by neurologist Filip Scheperjans of the University of Helsinki, asked two simple questions: Are the microorganisms that populate the guts of Parkinson’s patients different than those of healthy people? And if so, does that difference correlate with the stooped posture and difficulty walking that people with the disorder experience? Scheperjans’ answer to both questions was yes.
Carlin had picked up on a thread from one of the newest areas of Parkinson’s research: the relationship between Parkinson’s and the gut. Other than a small fraction of cases that are inherited, the cause of Parkinson’s disease is unknown. What is known is that something kills certain nerve cells, or neurons, in the brain. Abnormally misfolded and clumped proteins are the prime suspect. Some theories suggest a possible role for head trauma or exposure to heavy metals, pesticides or air pollution. People with Parkinson’s often have digestive issues, such as constipation, long before the disease appears. Since the early 2000s, scientists have been gathering evidence that the malformed proteins in the brains of Parkinson’s patients might actually first appear in the gut or nose (people with Parkinson’s also commonly lose their sense of smell). From there, the theory goes, these proteins work their way into the nervous system. Scientists don’t know exactly where in the gut the misfolded proteins come from, or why they form, but some early evidence points to the body’s internal microbial ecosystem. In the latest salvo, scientists from Sweden reported in October that people who had their appendix removed had a lower risk of Parkinson’s years later (SN: 11/24/18, p. 7). The job of the appendix, which is attached to the colon, is a bit of a mystery. But the organ may play an important role in intestinal health.
If the gut connection theory proves true — still a big if — it could open up new avenues to one day treat or at least slow the disease.
“It really changes the concept of what we consider Parkinson’s,” Scheperjans says. Maybe Parkinson’s isn’t a brain disease that affects the gut. Perhaps, for many people, it’s a gut disease that affects the brain.
Gut feeling London physician James Parkinson wrote “An essay on the shaking palsy” in 1817, describing six patients with unexplained tremors. Some also had digestive problems. (“Action of the bowels had been very much retarded,” he reported of one man.) He treated two people with calomel — a toxic, mercury-based laxative of the time — and noted that their tremors subsided.
But the digestive idiosyncrasies of the disease that later bore Parkinson’s name largely faded into the background for the next two centuries, until neuroanatomists Heiko Braak and Kelly Del Tredici, now at the University of Ulm in Germany, proposed that Parkinson’s disease might arise from the intestine. Writing in Neurobiology of Aging in 2003, they and their colleagues based their theory on autopsies of Parkinson’s patients. The researchers were looking for Lewy bodies, which contain clumps of a protein called alpha-synuclein. The presence of Lewy bodies in the brain is a hallmark of Parkinson’s, though their exact role in the disease is still under investigation.
Lewy bodies form when alpha-synuclein, which is produced by neurons and other cells, starts curdling into unusual strands. The body encapsulates the abnormal alpha-synuclein and other proteins into the round Lewy body bundles. In the brain, Lewy bodies collect in the cells of the substantia nigra, a structure that helps orchestrate movement. By the time symptoms appear, much of the substantia nigra is already damaged.
Substantia nigra cells produce the chemical dopamine, which is important for movement. Levodopa, the main drug prescribed for Parkinson’s, is a synthetic replacement for dopamine. The drug has been around for a half-century, and while it can alleviate symptoms for a while, it does not slow the destruction of brain cells.
In patient autopsies, Braak and his team tested for the presence of Lewy bodies, as well as abnormal alpha-synuclein that had not yet become bundled together. Based on comparisons with people without Parkinson’s, the researchers found signs that Lewy bodies start to form in the nasal passages and intestine before they show up in the brain. Braak’s group proposed that Parkinson’s disease develops in stages, migrating from the gut and nose into the nerves to reach the brain.
Neural highway Today, the idea that Parkinson’s might arise from the intestine, not the brain, “is one of the most exciting things in Parkinson’s disease,” says Heinz Reichmann, a neurologist at the University of Dresden in Germany. The Braak theory couldn’t explain how the Lewy bodies reach the brain, but Braak speculated that some sort of pathogen, perhaps a virus, might travel along the body’s nervous system, leaving a trail of Lewy bodies.
There is no shortage of passageways: The intestine contains so many nerves that it’s sometimes called the body’s second brain. And the vagus nerve offers a direct connection between those nerves in the gut and the brain (SN: 11/28/15, p. 18).
In mice, alpha-synuclein can indeed migrate from the intestine to the brain, using the vagus nerve like a kind of intercontinental highway, as Caltech researchers demonstrated in 2016 (SN: 12/10/16, p. 12). And Reichmann’s experiments have shown that mice that eat the pesticide rotenone develop symptoms of Parkinson’s. Other teams have shown similar reactions in mice that inhale the chemical. “What you sniff, you swallow,” he says.
To look at this idea another way, researchers have examined what happens to Parkinson’s risk when people have a weak or missing vagus nerve connection. There was a time when doctors thought that an overly eager vagus nerve had something to do with stomach ulcers. Starting around the 1970s, many patients had the nerve clipped as an experimental means of treatment, a procedure called a vagotomy. In one of the latest studies on vagotomy and Parkinson’s, researchers examined more than 9,000 patients with vagotomies, using data from a nationwide patient registry in Sweden. Among people who had the nerve cut down low, just above the stomach, the risk of Parkinson’s began dropping five years after surgery, eventually reaching a difference of about 50 percent compared with people who hadn’t had a vagotomy, the researchers reported in 2017 in Neurology. The studies are suggestive, but by no means definitive. And the vagus nerve may not be the only possible link the gut and brain share. The body’s immune system might also connect the two, as one study published in January in Science Translational Medicine found. Study leader Inga Peter, a genetic epidemiologist at the Icahn School of Medicine at Mount Sinai in New York City, was looking for genetic contributors to Crohn’s disease, an inflammatory bowel condition that affects close to 1 million people in the United States.
She and a worldwide team studied about 2,000 people from an Ashkenazi Jewish population, which has an elevated risk of Crohn’s, and compared them with people without the disease. The research led Peter and colleagues to suspect the role of a gene called LRRK2. That gene is involved in the immune system — which mistakenly attacks the intestine in people who have Crohn’s. So it made sense for a variant of that gene to be involved in inflammatory disease. The researchers were thrown, however, when they discovered that versions of the gene also appeared to increase the risk for Parkinson’s disease.
“We refused to believe it,” Peter says. The finding, although just a correlation, suggested that whatever the gene was doing to the intestine might have something to do with Parkinson’s. So the team investigated the link further, reporting results in the August JAMA Neurology.
In their analysis of a large database of health insurance claims and prescriptions, the scientists found more evidence of inflammation’s role. People with inflammatory bowel disease were about 30 percent more likely to develop Parkinson’s than people without it. But among those who had filled prescriptions for an anti-inflammatory medication called antitumor necrosis factor, which the researchers used as a marker for reduced inflammation, Parkinson’s risk was 78 percent lower than in people who had not filled prescriptions for the drug.
Belly bacteria Like Inga Peter, microbiologist Sarkis Mazmanian of Caltech came upon Parkinson’s disease almost by accident. He had long studied how the body’s internal bacteria interact with the immune system. At lunch one day with a colleague who was studying autism using a mouse version of the disease, Mazmanian asked if he could take a look at the animals’ intestines. Because of the high density of nerves in the intestine, he wanted to see if the brain and gut were connected in autism.
Neurons in the gut “are literally one cell layer away from the microbes,” he says. “That made me feel that at least the physical path or conduit was there.” He began to study autism, but wanted to switch to a brain disease with more obvious physical symptoms. When he learned that people with Parkinson’s disease often have a long history of digestive problems, he had his subject.
Mazmanian’s group examined mice that were genetically engineered to overproduce alpha-synuclein. He wanted to know whether the presence or absence of gut bacteria influenced symptoms that developed in the mice.
The results, reported in Cell in 2016, showed that when the mice were raised germ free — meaning their insides had no microorganisms — they showed no signs of Parkinson’s. The animals had no telltale gait or balance problems and no constipation, even though their bodies made alpha-synuclein (SN: 12/24/16 & 1/7/17, p. 10). “All the features of Parkinson’s in the animals were gone when the animals had no microbiome,” he says.
However, when gut microbes from people diagnosed with Parkinson’s were transplanted into the germ-free mice, the mice developed symptoms of the disease — symptoms that were much more severe than those in mice transplanted with microbes from healthy people.
Mazmanian suspects that something in the microbiome triggers the misfolding of alpha-synuclein. But this has not been tested in humans, and he is quick to say that this is just one possible explanation for the disease. “There’s likely no one smoking gun,” he says.
Microbial forces If the microbiome is involved, what exactly is it doing to promote Parkinson’s? Microbiologist Matthew Chapman of the University of Michigan in Ann Arbor thinks it may have something to do with chemical signals that bacteria send to the body. Chapman studies biofilms, which occur when bacteria form resilient colonies. (Think of the slime on the inside a drain pipe.)
Part of what makes biofilms so hard to break apart is that fibers called amyloids run through them. Amyloids are tight stacks of proteins, like columns of Legos. Scientists have long suspected that amyloids are involved in degenerative diseases of the brain, including Alzheimer’s. In Parkinson’s, amyloid forms of alpha-synuclein are found in Lewy bodies.
Despite amyloids’ bad reputation, the fibers themselves aren’t always undesirable, Chapman says. Sometimes they may provide a good way of storing proteins for future use, to be snapped off brick by brick as needed. Perhaps it’s only when amyloids form in the wrong place, like the brain, that they contribute to disease. Chapman’s lab group has found that E. coli bacteria, part of the body’s normal microbial population, produce amyloid forms of some proteins when they are under stress.
When gut bacteria produce amyloids, the body’s own cells could also be affected, wrote Chapman in 2017 in PLOS Pathogens with an unlikely partner: neurologist Robert Friedland of the University of Louisville School of Medicine in Kentucky. “This is a difficult field to study because it’s on the border of several fields,” Friedland says. “I’m a neurologist who has little experience in gastroenterology. When I talked about this to my colleagues who are gastroenterologists, they’ve never heard that bacteria make amyloid.” Friedland and collaborators reported in 2016 in Scientific Reports that when E. coli in the intestines of rats started to produce amyloid, alpha-synuclein in the rats’ brains also congealed into the amyloid form. In their 2017 paper, Chapman and Friedland suggested that the immune system’s reaction to the amyloid in the gut might have something to do with triggering amyloid formation in the brain.
In other words, when gut bacteria get stressed and start to produce their own amyloids, those microbes may be sending cues to nearby neurons in the intestine to follow suit. “The question is, and it’s still an outstanding question, what is it that these bacteria are producing that is, at least in animals, causing alpha-synuclein to form amyloids?” Chapman says.
Head for a cure There is, in fact, a long list of questions about the microbiome, says Scheperjans, the neurologist whose paper Martha Carlin first spotted. So far, studies of the microbiomes of human patients are largely limited to simple observations like his, and the potential for a microbiome connection has yet to reach deeply into the neurology community. But in October, for the second year in a row, Scheperjans says, the International Congress of Parkinson’s Disease and Movement Disorders held a panel discussing connections to the microbiome.
“I got interested in the gastrointestinal aspects because the patients complained so much about it,” he says. While his study found definite differences in the bacteria of people with Parkinson’s, it’s still too early to know how that might matter. But Scheperjans hopes that one day doctors may be able to test for microbiome changes that put people at higher risk for Parkinson’s, and restore a healthy microbe population through diet or some other means to delay or prevent the disease. One way to slow the disease might be shutting down the mobility of misfolded alpha-synuclein before it has even reached the brain. In Science in 2016, neuroscientist Valina Dawson and colleagues at Johns Hopkins University School of Medicine and elsewhere described using an antibody to halt the spread of bad alpha-synuclein from cell to cell. The researchers are working now to develop a drug that could do the same thing.
The goal is to one day test for the early development of Parkinson’s and then be able to tell a patient, “Take this drug and we’re going to try to slow and prevent progression of disease,” she says.
For her part, Carlin is doing what she can to speed research into connections between the microbiome and Parkinson’s. She quit her job, sold her house and drained her retirement account to pour money into the cause. She donated to the University of Chicago to study her husband’s microbiome. And she founded a company called the BioCollective to aid in microbiome research, providing free collection kits to people with Parkinson’s. The 15,000 microbiome samples she has collected so far are available to researchers.
Carlin admits that the possibility of a gut connection to Parkinson’s can be a hard sell. “It’s a difficult concept for people to wrap their head around when you are taking a broad view,” she says. As she searches for answers, her husband, John, keeps going. “He drives, he runs biking programs in Denver for people with Parkinson’s,” she says. Anything to keep the wheels turning toward the future.One way to slow the disease might be shutting down the mobility of misfolded alpha-synuclein before it has even reached the brain. In Science in 2016, neuroscientist Valina Dawson and colleagues at Johns Hopkins University School of Medicine and elsewhere described using an antibody to halt the spread of bad alpha-synuclein from cell to cell. The researchers are working now to develop a drug that could do the same thing.
The goal is to one day test for the early development of Parkinson’s and then be able to tell a patient, “Take this drug and we’re going to try to slow and prevent progression of disease,” she says.
For her part, Carlin is doing what she can to speed research into connections between the microbiome and Parkinson’s. She quit her job, sold her house and drained her retirement account to pour money into the cause. She donated to the University of Chicago to study her husband’s microbiome. And she founded a company called the BioCollective to aid in microbiome research, providing free collection kits to people with Parkinson’s. The 15,000 microbiome samples she has collected so far are available to researchers.
Carlin admits that the possibility of a gut connection to Parkinson’s can be a hard sell. “It’s a difficult concept for people to wrap their head around when you are taking a broad view,” she says. As she searches for answers, her husband, John, keeps going. “He drives, he runs biking programs in Denver for people with Parkinson’s,” she says. Anything to keep the wheels turning toward the future.
Race should no longer be used to describe populations in most genetics studies, a panel of experts says.
Using race and ethnicity to describe study participants gives the mistaken impression that humans can be divided into distinct groups. Such labels have been used to stigmatize groups of people, but do not explain biological and genetic diversity, the panel convened by the U.S. National Academies of Sciences, Engineering and Medicine said in a report on March 14. In particular, the term Caucasian should no longer be used, the committee recommends. The term, coined in the 18th century by German scientist Johann Friedrich Blumenbach to describe what he determined was the most beautiful skull in his collection, carries the false notion of white superiority, the panel says.
Worse, the moniker “has also acquired today the connotation of being an objective scientific term, and that’s what really led the committee to take objection with it,” says Ann Morning, a sociologist at New York University and a member of the committee that wrote the report. “It tends to reinforce this erroneous belief that racial categories are somehow objective and natural characterizations of human biological difference. We felt that it was a term that … should go into the dustbin of history.”
Similarly, the term “black race” shouldn’t be used because it implies that Black people are a distinct group, or race, that can be objectively defined, the panel says.
Racial definitions are problematic “because not only are they stigmatizing, they are historically wrong,” says Ambroise Wonkam, a medical geneticist at Johns Hopkins University and president of the African Society of Human Genetics. Race is often used as a proxy for genetic diversity. But “race cannot be used to capture diversity at all. Race doesn’t exist. There is only one race, the human race,” says Wonkam, who was not involved with the National Academies’ panel.
Race might be used in some studies to determine how genetic and social factors contribute to health disparities (SN: 4/5/22), but beyond that race has no real value in genetic research, Wonkam adds.
Researchers could use other identifiers, including geographical ancestry, to define groups of people in the study, Wonkam says. But those definitions need to be precise.
For instance, some researchers group Africans by language groups. But a Bantu-speaking person from Tanzania or Nigeria where malaria is endemic would have a much higher genetic risk of sickle cell disease than a Bantu-speaking person whose ancestors are from South Africa, where malaria has not existed for at least 1,000 years. (Changes in genes that make hemoglobin can protect against malaria (SN: 5/2/11), but cause life-threatening sickle cell disease.) Genetic studies also have to account for movements of people and mixture between multiple groups, Wonkam says. And labeling must be consistent for all groups in the study, he says. Current studies sometimes compare continent-wide racial groups, such as Asian, with national groups, such as French or Finnish, and ethnic groups, such as Hispanic.
An argument for keeping race in rare cases Removing race as a descriptor may be helpful for some groups, such as people of African descent, says Joseph Yracheta, a health disparities researcher and the executive director of the Native BioData Consortium, headquartered on the Cheyenne River Sioux reservation in South Dakota. “I understand why they want to get rid of race science for themselves, because in their case it’s been used to deny them services,” he says.
But Native Americans’ story is different, says Yracheta, who was not part of the panel. Native Americans’ unique evolutionary history have made them a valuable resource for genetics research. A small starting population and many thousands of years of isolation from humans outside the Americas have given Native Americans and Indigenous people in Polynesia and Australia some genetic features that may make it easier for researchers to find variants that contribute to health or disease, he says. “We’re the Rosetta stone for the rest of the planet.”
Native Americans “need to be protected, because not only are our numbers small, but we keep having things taken away from us since 1492. We don’t want this to be another casualty of colonialism.” Removing the label of Indigenous or Native American may erode tribal sovereignty and control over genetic data, he says.
The panel does recommend that genetic researchers should clearly state why they used a particular descriptor and should involve study populations in making decisions about which labels to use.
That community input is essential, Yracheta says. The recommendations have no legal or regulatory weight. So he worries that this lack of teeth may allow researchers to ignore the wishes of study participants without fear of penalty.
Still seeking diversity in research participants Genetics research has suffered from a lack of diversity of participants (SN: 3/4/21). To counteract the disparities, U.S. government regulations require researchers funded by the National Institutes of Health to collect data on the race and ethnicity of study participants. But because those racial categories are too broad and don’t consider the social and environmental conditions that may affect health, the labels are not helpful in most genetic analyses, the panel concluded.
Removing racial labels won’t hamper diversity efforts, as researchers will still seek out people from different backgrounds to participate in studies, says Brendan Lee, who is president of the American Society of Human Genetics. But taking race out of the equation should encourage researchers to think more carefully about the type of data they are collecting and how it might be used to support or refute racism, says Lee, a medical geneticist at Baylor College of Medicine in Houston, who was not part of the panel.
The report offers decision-making tools for determining what descriptors are appropriate for particular types of studies. But “while it is a framework, it is not a recipe where in every study we do A, B and C,” Lee says.
Researchers probably won’t instantly adopt the new practices, Lee says. “It is a process that will take time. I don’t think it is something we can expect in one week or one evening that we’ll all change over to this, but it is a very important first step.”
Off the Pacific coast of Costa Rica sits a deep-sea chimera of an ecosystem. Jacó Scar is a methane seep, where the gas escapes from sediment into the seawater, but the seep isn’t cold like the others found before it. Instead, geochemical activity gives the Scar lukewarm water that enables organisms from both traditionally colder seeps and scalding hot hydrothermal vents to call it home.
One resident of the Scar is a newly identified species of small, purplish fish called an eelpout, described for the first time on January 19 in Zootaxa. This fish is the first vertebrate species found at the Scar and could help scientists understand how the unique ecosystem developed. Jacó Scar was discovered during exploration of a known field of methane seeps off the Costa Rican coast and named for the nearby town of Jacó. It is “a really diverse place” with many different organisms living in various microhabitats, says Lisa Levin, a marine ecologist at Scripps Institution of Oceanography in La Jolla, Calif.
Levin was on one of the first expeditions to the Scar but wasn’t involved in the new study. She recalls the team finding and collecting one of the fish during this early excursion, but the researchers didn’t recognize it as a new species.
Several more specimens were snagged during later submersible dives. Charlotte Seid, an invertebrate biologist at Scripps who is working on a checklist of organisms found at the Costa Rican seeps, brought the fishy finds to ichthyologist Ben Frable, also of Scripps, for formal identification.
Frable says he knew the fish was an eelpout. They look exactly as one would expect based on their name: like frowning eels, though they aren’t true eels. But he was having trouble determining what type. Eelpouts are a diverse family of fish comprised of nearly 300 species that can be found all over the world at various ocean depths.
Because the physical differences between species can be subtle, they are “kind of a tricky group” to identify, Frable says. “I just was not really getting anywhere.” So the team turned to eelpout expert Peter Rask Møller of the Natural History Museum of Denmark in Copenhagen, sending him X-rays, pictures and eventually one of the fish specimens.
Møller narrowed the enigmatic eelpout to the genus Pyrolycus, meaning “fire wolf.” Turns out, the tool, called a dichotomous key, that Frable had been using to identify the specimens was outdated, made before Pyrolycus was described in 2002. “I did not know that genus existed,” Frable says.
Because the other two known Pyrolycus species live far away in the western Pacific and have different physical features, the team dubbed the mystery fish P. jaco — a new species.
The first eelpouts most likely evolved in cold waters, Frable says, but many have since made their home in the scalding waters of hydrothermal vents. Of the 24 known fish species that live only at hydrothermal vents, “13 of them are eelpouts,” Frable says. The new finding raises questions about how the known Pyrolycus species came to live so far apart. It may have to do with the fact that methane seeps are more common than previously thought on the ocean floor, and if some are lukewarm like Jacó Scar, the new species could have used them as refuges while moving east.
And by comparing P. jaco to its vent-living relatives, researchers may be able to figure out how it adapted to live in the tepid waters of the Scar — which may provide clues to how other species living there did too.
The eelpout is part of a medley of other species that form Jacó Scar’s composite ecosystem, along with, for example, clams typically found at cold seeps and bacteria found at hydrothermal vents. Jacó Scar is a “mixing bowl” of species found in other parts of the world, Seid says. Figuring out how this eclectic bunch interacts “is part of the fun.”
Just a few powerful storms in Antarctica can have an outsized effect on how much snow parts of the southernmost continent get. Those ephemeral storms, preserved in ice cores, might give a skewed view of how quickly the continent’s ice sheet has grown or shrunk over time.
Relatively rare extreme precipitation events are responsible for more than 40 percent of the total annual snowfall across most of the continent — and in some places, as much as 60 percent, researchers report March 22 in Geophysical Research Letters. Climatologist John Turner of the British Antarctic Survey in Cambridge and his colleagues used regional climate simulations to estimate daily precipitation across the continent from 1979 to 2016. Then, the team zoomed in on 10 locations — representing different climates from the dry interior desert to the often snowy coasts and the open ocean — to determine regional differences in snowfall.
While snowfall amounts vary greatly by location, extreme events packed the biggest wallop along Antarctica’s coasts, especially on the floating ice shelves, the researchers found. For instance, the Amery ice shelf in East Antarctica gets roughly half of its annual precipitation — which typically totals about half a meter of snow — in just 10 days, on average. In 1994, the ice shelf got 44 percent of its entire annual precipitation on a single day in September.
Ice cores aren’t just a window into the past; they are also used to predict the continent’s future in a warming world. So characterizing these coastal regions is crucial for understanding Antarctica’s ice sheet — and its potential future contribution to sea level rise. Editor’s note: This story was updated April 5, 2019, to correct that the results were reported March 22 (not March 25).
Editor’s note: On April 10, the Event Horizon Telescope collaboration released a picture of the supermassive black hole at the center of galaxy M87. Read the full story here.
We’re about to see the first close-up of a black hole.
The Event Horizon Telescope, a network of eight radio observatories spanning the globe, has set its sights on a pair of behemoths: Sagittarius A*, the supermassive black hole at the Milky Way’s center, and an even more massive black hole 53.5 million light-years away in galaxy M87 (SN Online: 4/5/17). In April 2017, the observatories teamed up to observe the black holes’ event horizons, the boundary beyond which gravity is so extreme that even light can’t escape (SN: 5/31/14, p. 16). After almost two years of rendering the data, scientists are gearing up to release the first images in April.
Here’s what scientists hope those images can tell us.
What does a black hole really look like? Black holes live up to their names: The great gravitational beasts emit no light in any part of the electromagnetic spectrum, so they themselves don’t look like much.
But astronomers know the objects are there because of a black hole’s entourage. As a black hole’s gravity pulls in gas and dust, matter settles into an orbiting disk, with atoms jostling one another at extreme speeds. All that activity heats the matter white-hot, so it emits X-rays and other high-energy radiation. The most voraciously feeding black holes in the universe have disks that outshine all the stars in their galaxies (SN Online: 3/16/18). The EHT’s image of the Milky Way’s Sagittarius A, also called SgrA, is expected to capture the black hole’s shadow on its accompanying disk of bright material. Computer simulations and the laws of gravitational physics give astronomers a pretty good idea of what to expect. Because of the intense gravity near a black hole, the disk’s light will be warped around the event horizon in a ring, so even the material behind the black hole will be visible. And the image will probably look asymmetrical: Gravity will bend light from the inner part of the disk toward Earth more strongly than the outer part, making one side appear brighter in a lopsided ring.
Does general relativity hold up close to a black hole? The exact shape of the ring may help break one of the most frustrating stalemates in theoretical physics.
The twin pillars of physics are Einstein’s theory of general relativity, which governs massive and gravitationally rich things like black holes, and quantum mechanics, which governs the weird world of subatomic particles. Each works precisely in its own domain. But they can’t work together.
“General relativity as it is and quantum mechanics as it is are incompatible with each other,” says physicist Lia Medeiros of the University of Arizona in Tucson. “Rock, hard place. Something has to give.” If general relativity buckles at a black hole’s boundary, it may point the way forward for theorists.
Since black holes are the most extreme gravitational environments in the universe, they’re the best environment to crash test theories of gravity. It’s like throwing theories at a wall and seeing whether — or how — they break. If general relativity does hold up, scientists expect that the black hole will have a particular shadow and thus ring shape; if Einstein’s theory of gravity breaks down, a different shadow.
Medeiros and her colleagues ran computer simulations of 12,000 different black hole shadows that could differ from Einstein’s predictions. “If it’s anything different, [alternative theories of gravity] just got a Christmas present,” says Medeiros, who presented the simulation results in January in Seattle at the American Astronomical Society meeting. Even slight deviations from general relativity could create different enough shadows for EHT to probe, allowing astronomers to quantify how different what they see is from what they expect. Do stellar corpses called pulsars surround the Milky Way’s black hole? Another way to test general relativity around black holes is to watch how stars careen around them. As light flees the extreme gravity in a black hole’s vicinity, its waves get stretched out, making the light appear redder. This process, called gravitational redshift, is predicted by general relativity and was observed near SgrA* last year (SN: 8/18/18, p. 12). So far, so good for Einstein.
An even better way to do the same test would be with a pulsar, a rapidly spinning stellar corpse that sweeps the sky with a beam of radiation in a regular cadence that makes it appear to pulse (SN: 3/17/18, p. 4). Gravitational redshift would mess up the pulsars’ metronomic pacing, potentially giving a far more precise test of general relativity.
“The dream for most people who are trying to do SgrA* science, in general, is to try to find a pulsar or pulsars orbiting” the black hole, says astronomer Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va. “There are a lot of quite interesting and quite deep tests of [general relativity] that pulsars can provide, that EHT [alone] won’t.”
Despite careful searches, no pulsars have been found near enough to SgrA* yet, partly because gas and dust in the galactic center scatters their beams and makes them difficult to spot. But EHT is taking the best look yet at that center in radio wavelengths, so Ransom and colleagues hope it might be able to spot some.
“It’s a fishing expedition, and the chances of catching a whopper are really small,” Ransom says. “But if we do, it’s totally worth it.” How do some black holes make jets? Some black holes are ravenous gluttons, pulling in massive amounts of gas and dust, while others are picky eaters. No one knows why. SgrA* seems to be one of the fussy ones, with a surprisingly dim accretion disk despite its 4 million solar mass heft. EHT’s other target, the black hole in galaxy M87, is a voracious eater, weighing in at between about 3.5 billion and 7.22 billion solar masses. And it doesn’t just amass a bright accretion disk. It also launches a bright, fast jet of charged subatomic particles that stretches for about 5,000 light-years.
“It’s a little bit counterintuitive to think a black hole spills out something,” says astrophysicist Thomas Krichbaum of the Max Planck Institute for Radio Astronomy in Bonn, Germany. “Usually people think it only swallows something.”
Many other black holes produce jets that are longer and wider than entire galaxies and can extend billions of light-years from the black hole. “The natural question arises: What is so powerful to launch these jets to such large distances?” Krichbaum says. “Now with the EHT, we can for the first time trace what is happening.”
EHT’s measurements of M87’s black hole will help estimate the strength of its magnetic field, which astronomers think is related to the jet-launching mechanism. And measurements of the jet’s properties when it’s close to the black hole will help determine where the jet originates — in the innermost part of the accretion disk, farther out in the disk or from the black hole itself. Those observations might also reveal whether the jet is launched by something about the black hole itself or by the fast-flowing material in the accretion disk.
Since jets can carry material out of the galactic center and into the regions between galaxies, they can influence how galaxies grow and evolve, and even where stars and planets form (SN: 7/21/18, p. 16).
“It is important to understanding the evolution of galaxies, from the early formation of black holes to the formation of stars and later to the formation of life,” Krichbaum says. “This is a big, big story. We are just contributing with our studies of black hole jets a little bit to the bigger puzzle.”
Editor’s note: This story was updated April 1, 2019, to correct the mass of M87’s black hole; the entire galaxy’s mass is 2.4 trillion solar masses, but the black hole itself weighs in at several billion solar masses. In addition, the black hole simulation is an example of one that uphold’s Einstein’s theory of general relativity, not one that deviates from it.
We live in a sea of neutrinos. Every second, trillions of them pass through our bodies. They come from the sun, nuclear reactors, collisions of cosmic rays hitting Earth’s atmosphere, even the Big Bang. Among fundamental particles, only photons are more numerous. Yet because neutrinos barely interact with matter, they are notoriously difficult to detect.
The existence of the neutrino was first proposed in the 1930s and then verified in the 1950s (SN: 2/13/54). Decades later, much about the neutrino — named in part because it has no electric charge — remains a mystery, including how many varieties of neutrinos exist, how much mass they have, where that mass comes from and whether they have any magnetic properties. These mysteries are at the heart of Ghost Particle by physicist Alan Chodos and science journalist James Riordon. The book is an informative, easy-to-follow introduction to the perplexing particle. Chodos and Riordon guide readers through how the neutrino was discovered, what we know — and don’t know — about it, and the ongoing and future experiments that (fingers crossed) will provide the answers.
It’s not just neutrino physicists who await those answers. Neutrinos, Riordon says, “are incredibly important both for understanding the universe and our existence in it.” Unmasking the neutrino could be key to unlocking the nature of dark matter, for instance. Or it could clear up the universe’s matter conundrum: The Big Bang should have produced equal amounts of matter and antimatter, the oppositely charged counterparts of electrons, protons and so on. When matter and antimatter come into contact, they annihilate each other. So in theory, the universe today should be empty — yet it’s not (SN: 9/22/22). It’s filled with matter and, for some reason, very little antimatter.
Science News spoke with Riordon, a frequent contributor to the magazine, about these puzzles and how neutrinos could act as a tool to observe the cosmos or even see into our own planet. The following conversation has been edited for length and clarity.
SN: In the first chapter, you list eight unanswered questions about neutrinos. Which is the most pressing to answer?
Riordon: Whether they’re their own antiparticles is probably one of the grandest. The proposal that neutrinos are their own antiparticles is an elegant solution to all sorts of problems, including the existence of this residue of matter we live in. Another one is figuring out how neutrinos fit in the standard model [of particle physics]. It’s one of the most successful theories there is, but it can’t explain the fact that neutrinos have mass. SN: Why is now a good time to write a book about neutrinos?
Riordon: All of these questions about neutrinos are sort of coming to a head right now — the hints that neutrinos may be their own antiparticles, the issues of neutrinos not quite fitting the standard model, whether there are sterile neutrinos [a hypothetical neutrino that is a candidate for dark matter]. In the next few years, a decade or so, there will be a lot of experiments that will [help answer these questions,] and the resolution either way will be exciting.
SN: Neutrinos could also be used to help scientists observe a range of phenomena. What are some of the most interesting questions neutrinos could help with?
Riordon: There are some observations that simply have to be done with neutrinos, that there are no other technological alternatives for. There’s a problem with using light-based telescopes to look back in history. We have this really amazing James Webb Space Telescope that can see really far back in history. But at some point, when you go far enough back, the universe is basically opaque to light; you can’t see into it. Once we narrow down how to detect and how to measure the cosmic neutrino background [neutrinos that formed less than a second after the Big Bang], it will be a way to look back at the very beginning. Other than with gravitational waves, you can’t see back that far with anything else. So it’ll give us sort of a telescope back to the beginning of the universe.
The other thing is, when a supernova happens, all kinds of really cool stuff happens inside, and you can see it with neutrinos because neutrinos come out immediately in a burst. We call it the “cosmic neutrino bomb,” but you can track the supernova as it’s going along. With light, it takes a while for it to get out [of the stellar explosion]. We’re due for a [nearby] supernova. We haven’t had one since 1987. It was the last visible supernova in the sky and was a boon for research. Now that we have neutrino detectors around the world, this next one is going to be even better [for research], even more exciting.
And if we develop better instrumentation, we could use neutrinos to understand what’s going on in the center of the Earth. There’s no other way that you could probe the center of the Earth. We use seismic waves, but the resolution is really low. So we could resolve a lot of questions about what the planet is made of with neutrinos.
SN: Do you have a favorite “character” in the story of neutrinos?
Riordon: I’m certainly very fond of my grandfather Clyde Cowan [he and Frederick Reines were the first physicists to detect neutrinos]. But Reines is a riveting character. He was poetic. He was a singer. He really was this creative force. I mentioned [in the book] that they put this “SNEWS” sign on their detector for “supernova early warning system,” which sort of echoed the ballistic missile early warning systems at the time [during the Cold War]. That’s so ripe.
For the first time, astronomers have caught a glimpse of shock waves rippling along strands of the cosmic web — the enormous tangle of galaxies, gas and dark matter that fills the observable universe.
Combining hundreds of thousands of radio telescope images revealed the faint glow cast as shock waves send charged particles flying through the magnetic fields that run along the cosmic web. Spotting these shock waves could give astronomers a better look at these large-scale magnetic fields, whose properties and origins are largely mysterious, researchers report in the Feb. 17 Science Advances. Finally, astronomers “can confirm what so far has only been predicted by simulations — that these shock waves exist,” says astrophysicist Marcus Brüggen of the University of Hamburg in Germany, who was not involved in the new study.
At its grandest scale, our universe looks something like Swiss cheese. Galaxies aren’t distributed evenly through space but rather are clumped together in enormous clusters connected by ropy filaments of dilute gas, galaxies and dark matter and separated by not-quite-empty voids (SN: 10/3/19).
Tugged by gravity, galaxy clusters merge, filaments collide, and gas from the voids falls onto filaments and clusters. In simulations of the cosmic web, all that action consistently sets off enormous shock waves in and along filaments.
Filaments make up most of the cosmic web but are much harder to spot than galaxies (SN: 1/20/14). While scientists have observed shock waves around galaxy clusters before, shocks in filaments “have never been really seen,” says astronomer Reinout van Weeren of Leiden University in the Netherlands, who was not involved in the study. “But they should be basically all around the cosmic web.”
Shock waves around filaments would accelerate charged particles through the magnetic fields that suffuse the cosmic web (SN: 6/6/19). When that happens, the particles emit light at wavelengths that radio telescopes can detect — though the signals are very weak. A single shock wave in a filament “would look like nothing, it’d look like noise,” says radio astronomer Tessa Vernstrom of the International Centre for Radio Astronomy Research in Crawley, Australia.
Instead of looking for individual shock waves, Vernstrom and her colleagues combined radio images of more than 600,000 pairs of galaxy clusters close enough to be connected by filaments to create a single “stacked” image. This amplified weak signals and revealed that, on average, there is a faint radio glow from the filaments between clusters.
“When you can dig below the noise and still actually get a result — to me, that’s personally exciting,” Vernstrom says.
The faint signal is highly polarized, meaning that the radio waves are mostly aligned with one another. Highly polarized light is unusual in the cosmos, but it is expected from radio light cast by shock waves, van Weeren says. “So that’s really, I think, very good evidence for the fact that the shocks are likely indeed present.” The discovery goes beyond confirming the predictions of cosmic web simulations. The polarized radio emissions also offer a rare peek at the magnetic fields that permeate the cosmic web, if only indirectly.
“These shocks,” Brüggen says, “are really able to show that there are large-scale magnetic fields that form [something] like a sheath around these filaments.”
He, van Weeren and Vernstrom all note that it’s still an open question how cosmic magnetic fields arose in the first place. The role these fields play in shaping the cosmic web is equally mysterious.
“It’s one of the four fundamental forces of nature, right? Magnetism,” Vernstrom says. “But at least on these large scales, we don’t really know how important it is.”
