A rocky planet that circles a small star nearly 40 light-years from Earth is hot and has little or no atmosphere, a new study suggests. The finding raises questions about the possibility of atmospheres on the other orbs in the planetary system.
At the center of the system is the red dwarf star dubbed TRAPPIST-1; it hosts seven known planets with masses ranging from 0.3 to 1.4 times Earth’s, a few of which could hold liquid water (SN: 2/22/17; 3/19/18). The largest, TRAPPIST-1b, is the closest to its parent star and receives about four times the radiation Earth receives from the sun, says Thomas Greene, an astrobiologist at NASA’s Ames Research Center at Moffett Field, Calif. Like all other planets in the system, TRAPPIST-1b is tidally locked, meaning that one side of the planet always faces the star, and one side looks away. Calculations suggest that if the stellar energy falling on TRAPPIST-1b were distributed around the planet — by an atmosphere, for example — and then reradiated equally in all directions, the planet’s surface temperature would be around 120° Celsius.
But the dayside temperature of the planet is actually around 230° C, Greene and colleagues report online March 27 in Nature. That, in turn, suggests that there’s little or no atmosphere to carry heat from the perpetually sunlit side of the planet to the dark side, the team argues.
To take TRAPPIST-1b’s temperature, Greene and his colleagues used the James Webb Space Telescope to observe the planet in a narrow band of infrared wavelengths five times in 2022. Because the observations were made just before and after the planet dodged behind its parent star, astronomers could see the fully lit face of the planet, Greene says.
The team’s results are “the first ‘deep dive’ look at this planet,” says Knicole Colon, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md, who was not involved with the study. “With every observation, we expect to learn something new,” she adds.
Astronomers have long suggested that planets around red dwarf stars might not be able to hold onto their atmospheres, largely because such stars’ frequent and high-energy flares would blast away any gaseous shroud they might have during their early years (SN: 12/20/22). Yet there are some scenarios in which such flares could heat up a planet’s surface and drive volcanism that, in turn, yields gases that could help form a new atmosphere.
“To be totally sure that this planet has no atmosphere, we need many more measurements,” says Michaël Gillon, an astrophysicist at the University of Liège in Belgium who was not part of the new study. It’s possible that when observed at a wider variety of wavelengths and from other angles, the planet could show signs of a gaseous shroud and thus possibly hints of volcanism.
Either way, says Laura Kriedberg, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany, who also did not participate in the study, the new result “definitely motivates detailed study of the cooler planets in the system, to see if the same is true of them.”
Most U.S. government attempts to quantify the costs and benefits of protecting the country’s bodies of water are likely undervaluing healthy lakes and rivers, researchers argue in a new study. That’s because some clean water benefits get left out of the analyses, sometimes because these benefits are difficult to pin numbers on. As a result, the apparent value of many environmental regulations is probably discounted.
The study, published online October 8 in the Proceedings of the National Academy of Sciences, surveyed 20 government reports analyzing the economic impacts of U.S. water pollution laws. Most of these laws have been enacted since 2000, when cost-benefit analyses became a requirement. Analysis of a measure for restricting river pollution, for example, might find that it increases costs for factories using that river for wastewater disposal, but boosts tourism revenues by drawing more kayakers and swimmers. Only two studies out of 20 showed the economic benefits of these laws exceeding the costs. That’s uncommon among analyses of environmental regulations, says study coauthor David Keiser, an environmental economist at Iowa State University in Ames. Usually, the benefits exceed the costs.
So why does water pollution regulation seem, on paper at least, like such a losing proposition?
Keiser has an explanation: Summing up the monetary benefits of environmental policies is really hard. Many of these benefits are intangible and don’t have clear market values. So deciding which benefits to count, and how to count them, can make a big difference in the results. Many analyses assume water will be filtered for drinking, Keiser says, so they don’t count the human health benefits of clean lakes and rivers (SN: 8/18/18, p. 14). That’s different from air pollution cost-benefit studies, which generally do include the health benefits of cleaner air by factoring in data tracking things like doctor’s visits or drug prescriptions. That could explain why Clean Air Act rules tend to get more favorable reviews, Keiser says — human health accounts for about 95 percent of the measured benefits of air quality regulations.
“You can avoid a lake with heavy, thick, toxic algal blooms,” Keiser says. “If you walk outside and have very polluted air, it’s harder to avoid.”
But even if people can avoid an algae-choked lake, they still pay a price for that pollution, says environmental scientist Thomas Bridgeman, director of the Lake Erie Center at the University of Toledo in Ohio. Communities that pull drinking water from a lake filled with toxic blooms of algae or cyanobacteria spend more to make the water safe to drink. Bridgeman’s seen it firsthand: In 2014, Lake Erie’s cyanobacteria blooms from phosphorus runoff shut down Toledo’s water supply for two days and forced the city to spend $500 million on water treatment upgrades.
Most of the studies surveyed by Keiser and his team were missing other kinds of benefits, too. The reports usually left out the value of eliminating certain toxic and nonconventional pollutants — molecules such as bisphenol A, or BPA, and perfluorooctanoic acid, or PFOA (SN: 10/3/15, p. 12). In high quantities, these compounds, which are used to make some plastics and nonstick coatings, can cause harm to humans and wildlife. Many studies also didn’t include discussion of how the quality of surface waters can affect groundwater, which is a major source of drinking water for many people.
A lack of data on water quality may also limit studies, Keiser’s team suggests. While there’s a national database tracking daily local air pollution levels, the data from various water quality monitoring programs aren’t centralized. That makes gathering and evaluating trends in water quality harder.
Plus, there are the intangibles — the value of aquatic species that are essential to the food chain, for example. “Some things are just inherently difficult to put a dollar [value] on,” says Robin Craig, an environmental law professor at the University of Utah in Salt Lake City. “What is it worth to have a healthy native ecosystem?… That’s where it can get very subjective very fast.”
That subjectivity can allow agencies to analyze policies in ways that suit their own political agendas, says Matthew Kotchen, an environmental economist at Yale University. An example: the wildly different assessments by the Obama and Trump administrations of the value gained from the 2015 Clean Water Rule, also known as the Waters of the United States rule.
The rule, passed under President Barack Obama, clarified the definition of waters protected under the 1972 Clean Water Act to include tributaries and wetlands connected to larger bodies of water. The Environmental Protection Agency estimated in 2015 that the rule would result in yearly economic benefits ranging from $300 million to $600 million, edging out the predicted annual costs of $200 million to $500 million. But in 2017, Trump’s EPA reanalyzed the rule and proposed rolling it back, saying that the agency had now calculated just $30 million to $70 million in annual benefits.
The difference in the conclusions came down to the consideration of wetlands: The 2015 analysis found that protecting wetlands, such as marshes and bogs that purify water, tallied up to $500 million in annual benefits. The Trump administration’s EPA, however, left wetlands out of the calculation entirely, says Kotchen, who analyzed the policy swing in Science in 2017.
Currently, the rule has gone into effect in 26 states, but is still tied up in legal challenges.
It’s an example of how methodology — and what counts as a benefit — can have a huge impact on the apparent value of environmental policies and laws.
The squishiness in analyzing environmental benefits underlies many of the Trump administration’s proposed rollbacks of Obama-era environmental legislation, not just ones about water pollution, Kotchen says. There are guidelines for how such cost-benefit analyses should be carried out, he says, but there’s still room for researchers or government agencies to choose what to include or exclude.
In June, the EPA, then under the leadership of Scott Pruitt, proposed revising the way the agency does cost-benefit analyses to no longer include so-called indirect benefits. For example, in evaluating policies to reduce carbon dioxide emissions, the agency would ignore the fact that those measures also reduce other harmful air pollutants. The move would, overall, make environmental policies look less beneficial.
These sharp contrasts in how presidential administrations approach environmental impact studies are not unprecedented, says Craig, the environmental law professor. “Pretty much every time we change presidents, the priorities for how to weigh those different elements change.”
Flying forward is hard enough, but flying nowhere, just hovering, is so much harder. Most bats and birds can manage the feat for only a few frantic seconds.
Hovering means losing a useful aerodynamic shortcut, says aerospace engineer and biologist David Lentink of Stanford University. As a bat or bird flies forward, its body movement sends air flowing around the wings and providing some cheap lift. For animals on the scale of bats and birds, that’s a big help. Without that boost, “you’re going to have to move all the air over your wings by moving it with your wings,” he says. The energy per second you’re consuming to stay in place by flapping your wings back and forth like a hummingbird “is gigantic.” So how do vertebrates in search of nectar, for whom a lot of energy-sucking hovering is part of life, manage the job? For the first direct measurements of the wingbeat forces that make hovering possible, Lentink’s Ph.D. student Rivers Ingersoll spent three years creating a flight chamber with exquisitely responsive sensors in the floor and ceiling. As a bird or bat hovers inside, the sensors can measure — every 200th of a second — tremors even smaller than a nanometer caused by air from fluttering wings. Once the delicate techno-marvel of an instrument was perfected, the researchers packed it into 11 shipping cases and sent it more than 6,000 kilometers to the wilds of Costa Rica. “Very difficult,” Ingersoll acknowledges. The Las Cruces Research Station is great for field biology, but it’s nothing like a Stanford engineering lab. Every car turning into the station’s driveway set off the wingbeat sensors. And even the special thick-walled room that became the machine’s second home warmed up enough every day to give the instrument a fever. Babying the instrument as best he could, Ingersoll made direct measurements for 17 hovering species of hummingbirds and three bats, including Pallas’s long-tongued bats (Glossophaga soricina). “Their up-pointy noses made me think of rhino faces,” he says. Pallas’s bats specialize in nectar sipping much as hummingbirds do. Comparing wingbeats, bat vs. bird, revealed differences, though. Hummers coupled powerful downstrokes and recovery upstrokes that twist part of the wings almost backward. The twist supplied about a quarter of the energy it takes to keep a bird aloft, the researchers report in the September 26 Science Advances. The two kinds of nectar bats got a little more lift from the upstroke than did a bat that eats fruit instead of strenuously hovering for nectar. Yet even the specialist nectar bats relied mostly on downstrokes: powerful, deeply angled downstrokes of really big wings.
Those bat wings span proportionally more area than hummer wings. So the bats get about the same hovering power per gram of body weight that hummingbirds do. Supersizing can have its own kind of high-tech design elegance.
SAN DIEGO — A sleepless night can leave the brain spinning with anxiety the next day.
In healthy adults, overnight sleep deprivation triggered anxiety the next morning, along with altered brain activity patterns, scientists reported November 4 at the annual meeting of the Society for Neuroscience.
People with anxiety disorders often have trouble sleeping. The new results uncover the reverse effect — that poor sleep can induce anxiety. The study shows that “this is a two-way interaction,” says Clifford Saper, a sleep researcher at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston who wasn’t involved in the study. “The sleep loss makes the anxiety worse, which in turn makes it harder to sleep.” Sleep researchers Eti Ben Simon and Matthew Walker, both of the University of California, Berkeley, studied the anxiety levels of 18 healthy people. Following either a night of sleep or a night of staying awake, these people took anxiety tests the next morning. After sleep deprivation, anxiety levels in these healthy people were 30 percent higher than when they had slept. On average, the anxiety scores reached levels seen in people with anxiety disorders, Ben Simon said November 5 in a news briefing.
What’s more, sleep-deprived people’s brain activity changed. In response to emotional videos, brain areas involved in emotions were more active, and the prefrontal cortex, an area that can put the brakes on anxiety, was less active, functional MRI scans showed.
The results suggest that poor sleep “is more than just a symptom” of anxiety, but in some cases, may be a cause, Ben Simon said.
The cabbage tree emperor moth has wings with tiny scales that absorb sound waves sent out by bats searching for food. That absorption reduces the echoes that bounce back to bats, allowing Bunaea alcinoe to avoid being so noticeable to the nocturnal predators, researchers report online November 12 in the Proceedings of the National Academy of Sciences.
“They have this stealth coating on their body surfaces which absorbs the sound,” says study coauthor Marc Holderied, a bioacoustician at the University of Bristol in England. “We now understand the mechanism behind it.”
Bats sense their surroundings using echolocation, sending out sound waves that bounce off objects and return as echoes picked up by the bats’ supersensitive ears (SN: 9/30/17, p. 22). These moths, without ears that might alert them to an approaching predator, have instead developed scales of a size, shape and thickness suited to absorbing ultrasonic sound frequencies used by bats, the researchers found. The team shot ultrasonic sound waves at a single, microscopic scale and observed it transferring sound wave energy into movement. The scientists then simulated the process with a 3-D computer model that showed the scale absorbing up to 50 percent of the energy from sound waves.
What’s more, it isn’t just wings that help such earless moths evade bats. Other moths in the same family as B. alcinoe also have sound-absorbing fur, the same researchers report online October 18 in the Journal of the Acoustical Society of America. Holderied and his colleagues studied the fluffy thoraxes of the Madagascan bullseye moth and the promethea silk moth, and found that the fur also absorbs sound waves through a different process called porous absorption. In lab tests, the furry-bellied moths absorbed as much as 85 percent of the sound waves encountered. Researchers suspect that the equally fluffy cabbage tree emperor moth also has this ability.
Other moths that have ears can hear bats coming, and can quickly swerve out of the way of their predators, dipping and diving in dizzying directions (SN: 5/26/18, p. 11). Some moths also have long tails on their wings that researchers suspect can be twirled to disrupt bats’ sound waves (SN: 3/21/15, p. 17). Still other moths produce toxins to fend off foes.
Having sound-absorbent fur and scales “might require a lot less energy in terms of protection from the moth’s side,” says Akito Kawahara, an evolutionary biologist at the Florida Museum of Natural History in Gainesville who was not involved with the study. “It’s a very different kind of passive defense system.”
Holderied and his colleagues hope next to study how multiple scales, locked together, respond to ultrasonic sound waves. The findings could one day help in developing better soundproofing technology for sound engineers and acousticians.
Screwworms, the first pest to be eliminated on a large scale by the use of the sterile male technique, have shown an alarming increase, according to U.S. and Mexican officials…. The screwworm fly lays its eggs in open wounds on cattle. The maggots live on the flesh of their host, causing damage and death, and economic losses of many millions of dollars. — Science News, November 23, 1968
Update Though eradicated in the United States in 1966, screwworms reemerged two years later, probably coming up from Mexico. Outbreaks in southern U.S. states in 1972 and in Florida in 2016 were both handled with the sterile male technique, considered one of the most successful approaches for pest control. Males are sterilized with radiation, then released into a population to breed with wild counterparts; no offspring result. The method has been used with other pests, such as mosquitoes, which were dropped by drones over Brazil this year as a test before the technology is used against outbreaks like the Zika virus.
A physicist, a gamer and two editors walk into a bar. No, this isn’t the setup for some joke. After work one night, a few Science News staffers tried out a new board game, Subatomic. This deck-building game combines chemistry and particle physics for an enjoyable — and educational — time.
Subatomic is simple to grasp: Players use quark and photon cards to build protons, neutrons and electrons. With those three particles, players then construct chemical elements to score points. Scientists are the wild cards: Joseph J. Thomson, Maria Goeppert-Mayer, Marie Curie and other Nobel laureates who discovered important things related to the atom provide special abilities or help thwart other players. The game doesn’t shy away from difficult or unfamiliar concepts. Many players might be unfamiliar with quarks, a group of elementary particles. But after a few rounds, it’s ingrained in your brain that, for example, two up quarks and one down quark create a proton. And Subatomic includes a handy booklet that explains in easy-to-understand terms the science behind the game. The physicist in our group vouched for the game’s accuracy but had one qualm: Subatomic claims that two photons, or particles of light, can create an electron. That’s theoretically possible, but scientists have yet to confirm it in the lab.
The mastermind behind Subatomic is John Coveyou, who has a master’s degree in energy, environmental and chemical engineering. As the founder and CEO of Genius Games , he has created six other games, including Ion ( SN: 5/30/15, p. 29 ) and Linkage ( SN: 12/27/14, p. 32 ). Next year, he’ll add a periodic table game to the list . Because Science News has reviewed several of his games, we decided to talk with Coveyou about where he gets his inspiration and how he includes real science in his products. The following discussion has been edited for length and clarity. SN: When did you get interested in science?
Coveyou: My mom was mentally and physically disabled, and my dad was in and out of prison and mental institutions. So early on, things were very different for me. I ended up leaving home when I was in high school, hopscotching around from 12 different homes throughout my junior and senior year. I almost dropped out, but I had a lot of teachers who were amazing mentors. I didn’t know what else to do, so I joined the army. While I was in Iraq, I had a bunch of science textbooks shipped to me, and I read them in my free time. They took me out of the environments I was in and became extremely therapeutic. A lot of the issues we face as a society can be worked on by the next generation having a command of the sciences. So I’m very passionate about teaching people the sciences and helping people find joy in them.
SN: Why did you start creating science games?
Coveyou: I was teaching chemistry at a community college, and I noticed that my students were really intimidated by the chemistry concepts before they even came into the classroom. They really struggled with a lot of the basic terminology. At the same time, I’ve been a board gamer pretty much my whole life. And it kind of hit me like, “Whoa, wait a second. What if I made some games that taught some of the concepts that I’m trying to teach my chemistry students?” So I just took a shot at it. The first couple of games were terrible. I didn’t really know what I was doing, but I kept at it.
SN: How do you test the games?
Coveyou: We first test with other gamers. Once we’re ready to get feedback from the general public, we go to middle school or high school students. Once we test a game with people face-to-face, we will send it across the world to about 100 to 200 different play testers, and those vary from your hard-core gamers to homeschool families to science teachers, who try it in the classroom.
SN: How do you incorporate real science into your games?
Coveyou: I pretty much always start with a science concept in mind and think about how can we create a game that best reflects the science that we want to communicate. For all of our upcoming games, we include a booklet about the science. That document is not created by Genius Games. We have about 20 to 30 Ph.D.s and doctors across the globe who write the content and edit each other. That’s been a real treat to actually show players how the game is accurate. We’ve had so many scientists and teachers who are just astonished that we created something like this that was accurate, but also fun to play.
Voyager 2 has entered interstellar space. The spacecraft slipped out of the huge bubble of particles that encircles the solar system on November 5, becoming the second ever human-made craft to cross the heliosphere, or the boundary between the sun and the stars.
Coming in second place is no mean achievement. Voyager 1 became the first spacecraft to exit the solar system in 2012. But that craft’s plasma instrument stopped working in 1980, leaving scientists without a direct view of the solar wind, hot charged particles constantly streaming from the sun (SN Online: 9/12/13). Voyager 2’s plasma sensors are still working, providing unprecedented views of the space between stars.
“We’ve been waiting with bated breath for the last couple of months for us to be able to see this,” NASA solar physicist Nicola Fox said at a Dec. 10 news conference at the American Geophysical Union meeting in Washington, D.C.
NASA launched the twin Voyager spacecraft in 1977 on a grand tour of the solar system’s planets (SN: 8/19/17, p. 26). After that initial tour was over, both spacecraft continued travelling through the bubble of plasma that originates at the sun. “When Voyager was launched, we didn’t know how large the bubble was, how long it would take to get [to its edge] and whether the spacecraft could last long enough to get there,” said Voyager project scientist Edward Stone of Caltech.
For most of Voyager 2’s journey, the spacecraft’s Plasma Science Experiment measured the speed, density, temperature, pressure and other properties of the solar wind. But on November 5, the experiment saw a sharp drop in the speed and the number of solar wind particles that hit the detector each second. At the same time, another detector started picking up more high-energy particles called cosmic rays that originate elsewhere in the galaxy. Those measurements suggest that Voyager 2 has reached the region where the solar wind slams into the colder, denser population of particles that fill the space between stars. Voyager 2 is now a little more than 18 billion kilometers from the sun.
Intriguingly, Voyager 2’s measurements of cosmic rays and magnetic fields — which Voyager 1 could still make when it crossed the boundary — did not exactly match up with Voyager 1’s observations. “That’s what makes it interesting,” Stone said. The variations are probably from the fact that the two spacecraft exited the heliosphere in different places, and that the sun is at a different part of its 11-year activity cycle than it was in 2012. “We would have been amazed if they had looked the same.”
The Voyagers probably have between five and 10 years left to continue exploring interstellar space, said Voyager project manager Suzanne Dodd from NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
“Both spacecraft are very healthy if you consider them senior citizens,” Dodd said. The biggest concern is how much power they have left and how cold they are — Voyager 2 is currently about 3.6° Celsius, close to the freezing point of its hydrazine fuel. In the near future, the team will have to turn off some of the spacecraft’s instruments to keep the craft operating and sending data back to Earth.
“We do have difficult decisions ahead,” Dodd said. She added that her personal goal is to see the spacecraft last until 2027, for a total of 50 years in space. “That would be fantastic.”
WASHINGTON – A months-long heat wave that scorched the Tasman Sea beginning in November of 2017 is the latest example of an extreme event that would not have happened without human-caused climate change.
Climate change also increased the likelihood of 15 other extreme weather events in 2017, from droughts in East Africa and the U.S. northern Plains states to floods in Bangladesh, China and South America, scientists reported December 10 at a news conference at the American Geophysical Union’s fall meeting. The findings were also published online December 10 in a series of studies in a special issue of the Bulletin of the American Meteorological Society. One study, of wildfires in Australia, was inconclusive on whether climate change influenced the event. And for the first time, none of the extreme events studied was determined to be the product of natural climate variability.
The findings mark the second year in a row — and only the second time — that scientists contributing to this special issue have definitively linked human-caused climate change with specific extreme weather events (SN: 1/20/18, p. 6). To the editors of the special issue, this latest tally is representative of the new normal in which the world finds itself.
“Many events were found to have appreciable climate change input; that’s not itself a surprise,” said Martin Hoerling, a special editor of the issue, at the news conference. “We are in a world that is warmer than it was in the 20th century, and we keep moving away from that baseline….”
“Nature is unfolding itself in front of our eyes,” added Hoerling, a research meteorologist with the U.S. National Oceanic and Atmospheric Administration in Boulder, Colo. Marine heat waves Several marine heat waves have struck the Tasman Sea, located between Australia and New Zealand, in the last decade, including a severe heat wave during the Southern Hemisphere summer of 2015 to 2016. But the 2017–2018 event extended across a much broader area, encompassing the entire sea. At its most severe point, temperatures increased to at least 2 degrees Celsius above average in the ocean, devastating the region’s iconic kelp forests and contributing to record-breaking summer temperatures in New Zealand.
Climate change was also responsible for another marine heat wave off the coast of East Africa that lasted from March to June 2017, according to a separate study. That marine heat wave, which the researchers found could not have happened in a preindustrial climate, also may have contributed to a drought in East Africa that caused food shortages for millions of people in the Horn of Africa, including 6 million in Somalia alone. The hot sea surface temperatures, the researchers found, doubled the probability that such a drought would occur.
“Any given extreme event might occur, but the severity of the events, that’s really what has changed. And it’s going to continue to change,” says Karsten Haustein, a climate scientist at the University of Oxford who is part of a research group that specializes in such climate attribution studies. Haustein is a coauthor on a study included in the collection that found that climate change dramatically increased the likelihood — by as much as 100 percent — of a six-day rainstorm that inundated Bangladesh in March 2017. The rainfall, which caused a flash flood, occurred before the onset of the monsoon season and proved devastating to farmers, Haustein says.
Legal liability The new issue highlights how the field of climate attribution science overall has crossed a critical threshold when it comes to liability, Lindene Patton, a strategic advisor at the Earth & Water Law Group in Washington, D.C., who specializes in climate attribution, said at the news conference. Although climate change was not found to be definitively to blame in most of the studies, it very likely was responsible for or intensified the impacts of nearly every extreme event examined in the issue — and that level of statistical certainty is enough to be legally important, Patton said. “The sufficiency of certainty differs in a court of law and in science. Perfection is not required; you just need to know if it’s more likely than not.”
The threat of liability may not be the ideal way to achieve more environment-friendly policies — but there is a precedent for it, she noted. “We clearly saw the emergence of liability in the 1970s with pollution” as a precursor to pollutant legislation.
BAMS Editor in Chief Jeff Rosenfeld acknowledges that in a world where real-time attribution studies of events such as 2018’s Hurricane Florence are becoming more common (SN Online: 9/13/18), the detailed, retrospective analyses of the BAMS special issue that lag by a year may seem a bit slow. “The funny thing is, initially, we considered it fast response,” he says.
But he thinks the looming question of climate liability highlights why the slower, more deliberate BAMS studies will continue to remain relevant, even in the swiftly changing climate of attribution science. “The people who are decision makers want numbers. They want risk factors.”
A new soft, wireless implant may someday help people who suffer from overactive bladder get through the day with fewer bathroom breaks.
The implant harnesses a technique for controlling cells with light, known as optogenetics, to regulate nerve cells in the bladder. In experiments in rats with medication-induced overactive bladders, the device alleviated animals’ frequent need to pee, researchers report online January 2 in Nature.
Although optogenetics has traditionally been used for manipulating brain cells to study how the mind works, the new implant is part of a recent push to use the technique to tame nerve cells throughout the body (SN: 1/30/10, p. 18). Similar optogenetic implants could help treat disease and dysfunction in other organs, too. “I was very happy to see this,” says Bozhi Tian, a materials scientist at the University of Chicago not involved in the work. An estimated 33 million people in the United States have overactive bladders. One available treatment is an implant that uses electric currents to regulate bladder nerve cells. But those implants “will stimulate a lot of nerves, not just the nerves that control the bladder,” Tian says. That can interfere with the function of neighboring organs, and continuous electrical stimulation can be uncomfortable.
The new optogenetic approach, however, targets specific nerves in only one organ and only when necessary. To control nerve cells with light, researchers injected a harmless virus carrying genetic instructions for bladder nerve cells to produce a light-activated protein called archaerhodopsin 3.0, or Arch. A stretchy sensor wrapped around the bladder tracks the wearer’s urination habits, and the implant wirelessly sends that information to a program on a tablet computer. If the program detects the user heeding nature’s call at least three times per hour, it tells the implant to turn on a pair of tiny LEDs. The green glow of these micro light-emitting diodes activates the light-sensitive Arch proteins in the bladder’s nerve cells, preventing the cells from sending so many full-bladder alerts to the brain. John Rogers, a materials scientist and bioengineer at Northwestern University in Evanston, Ill., and colleagues tested their implants by injecting rats with the overactive bladder–causing drug cyclophosphamide. Over the next several hours, the implants successfully detected when rats were passing water too frequently, and lit up green to bring the animals’ urination patterns back to normal.
Shriya Srinivasan, a medical engineer at MIT not involved in the work, is impressed with the short-term effectiveness of the implant. But, she says, longer-term studies may reveal complications with the treatment.
For instance, a patient might develop an immune reaction to the foreign Arch protein, which would cripple the protein’s ability to block signals from bladder nerves to the brain. But if proven safe and effective in the long term, similar optogenetic implants that sense and respond to organ motion may also help treat heart, lung or muscle tissue problems, she says.
Optogenetic implants could also monitor other bodily goings-on, says study coauthor Robert Gereau, a neuroscientist at Washington University in St. Louis. Hormone levels and tissue oxygenation or hydration, for example, could be tracked and used to trigger nerve-altering LEDs for medical treatment, he says.
