Old blood can prematurely age the brains of young mice, and scientists may now be closer to understanding how. A protein located in the cells that form a barrier between the brain and blood could be partly to blame, experiments on mice suggest.
If something similar happens in humans, scientists say, methods for countering the protein may hold promise for treating age-related brain decline.
The preliminary study, published online January 3 at bioRxiv.org, focused on a form of the protein known as VCAM1, which interacts with immune cells in response to inflammation. As mice and humans age, levels of that protein circulating in the blood rise, Alzheimer researcher Tony Wyss-Coray at Stanford University and colleagues found. After injecting young mice behind an eye with plasma from old mice, the team discovered that VCAM1 levels also rose in certain parts of the blood-brain barrier, a mesh of tightly woven cells that protect the brain from harmful factors in the blood. The young mice showed signs of brain deterioration as well, including inflammation and decreased birthrates of new nerve cells. Plasma from young mice had no such effects.
Interfering with VCAM1 may help prevent the premature aging of brains. Plasma from old mice didn’t have a strong effect when injected into young mice genetically engineered to lack VCAM1 in certain blood-brain barrier cells. Nor did it affect mice treated with antibodies that blocked the activity of VCAM1. Those antibodies also seemed to help the brains of older mice that had aged naturally, the team found.
The results suggest that anti-aging treatments targeting specific aspects of the blood-brain barrier may hold promise.
These fins were made for walking, and that’s just what these fish do — thanks to wiring that evolved long before vertebrates set foot on land.
Little skates use two footlike fins on their undersides to move along the ocean floor. With an alternating left-right stride powered by muscles flexing and extending, the movement of these fish looks a lot like that of many land-based animals.
Now, genetic tests show why: Little skates and land vertebrates share the same genetic blueprint for development of the nerve cells needed for limb movement, researchers report online February 8 in Cell. This work is the first to look at the origins of the neural circuitry needed for walking, the authors say. “This is fantastically interesting natural history,” says Ted Daeschler, a vertebrate paleontologist at the Academy of Natural Sciences in Philadelphia.
“Neurons essential for us to walk originated in ancient fish species,” says Jeremy Dasen, a neuroscientist at New York University. Based on fossil records, Dasen’s team estimates that the common ancestor of all land vertebrates and skates lived around 420 million years ago — perhaps tens of millions of years before vertebrates moved onto land (SN: 1/14/12, p. 12). Little skates (Leucoraja erinacea) belong to an evolutionarily primitive group. Skates haven’t changed much since their ancestors split from the fish that evolved into land-rovers, so finding the same neural circuitry in skates and land vertebrates was surprising.
The path to discovery started when Dasen and coauthor Heekyung Jung, now at Stanford University, saw YouTube videos of the little skates walking.
“I was completely flabbergasted,” Dasen says. “I knew some species of fish could walk, but I didn’t know about these.”
Most fish swim by undulating their bodies and tails, but little skates have a spine that remains relatively straight. Instead, little skates move by flapping pancake-shaped pectoral fins and walking on “feet,” two fins tucked along the pelvis.
Measurements of the little skates’ movements found that they were “strikingly similar” to bipedal walking, says Jung, who did the work while at NYU. To investigate how that similarity arose, the researchers looked to motor nerve cells, which are responsible for controlling muscles. Each kind of movement requires different kinds of motor nerve cells, Dasen says.
The building of that neural circuitry is controlled in part by Hox genes, which help set the body plan, where limbs and muscles and nerves should go. For instance, snakes and other animals that have lost some Hox genes have bodies that move in the slinky, slithery undulations that many fish use to swim underwater.
By comparing Hox genes in L. erinacea and mice, researchers discovered that both have Hox6/7 and Hox10 genes and that these genes have similar roles in both. Hox6/7 is important for the development of the neural circuitry used to move the skates’ pectoral fins and the mice’s front legs; Hox10 plays the same role for the footlike fins in little skates and hind limbs in mice. Other genes and neural circuitry for motor control were also conserved, or unchanged, between little skates and mice. The findings suggest that both skates and mice share a common ancestor with similar genetics for locomotion.
The takeaway is that “vertebrates are all very similar to each other,” says Daeschler. “Evolution works by tinkering. We’re all using what we inherited — a tinkered version of circuitry that began 400-plus million years ago.”
Orangutan numbers on the Southeast Asian island of Borneo plummeted from 1999 to 2015, more as a result of human hunting than habitat loss, an international research team finds.
Over those 16 years, Borneo’s orangutan population declined by about 148,500 individuals. A majority of those losses occurred in the intact or selectively logged forests where most orangutans live, primatologist Maria Voigt of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and colleagues report February 15 in Current Biology. “Orangutan killing is likely the number one threat to orangutans,” says study coauthor Serge Wich, a biologist and ecologist at Liverpool John Moores University in England. Humans hunt the forest-dwelling apes for food, or to prevent them from raiding crops, the investigators say. People also kill adult orangutans to steal their babies for the international pet trade.
Between 70,000 and roughly 100,000 orangutans currently live on Borneo, Wich says. That’s substantially higher than previous population estimates. The new figures are based on the most extensive survey to date, using ground and air monitoring of orangutans’ tree nests. Orangutans live only on Borneo and the island of Sumatra and are endangered in both places.
Still, smaller orangutan populations in deforested areas of Borneo — due to logging or conversion to farm land — experienced the severest rates of decline, up to a 75 percent drop in one region.
Satellite data indicate that Borneo’s forest area has already declined by about 30 percent from 1973 to 2010. In the next 35 years, Voigt’s team calculates that further habitat destruction alone will lead to the loss of around 45,000 more of these apes. “Add hunting to that and it’s a lethal mix,” Wich says. But small groups of Bornean orangutans living in protected zones and selectively logged areas will likely avoid extinction, the researchers say.
While the drama of human heart transplants has grasped the public interest, kidney transplants are ahead in the field…. Although only three little girls are now surviving liver transplants, the liver is a promising field for replacement…. The donor, of course, must be dead; no one can live without his liver. — Science News, March 2, 1968
Update Kidney patients, who could receive organs from family members, had up to a 75 percent one-year survival rate in 1968. Liver recipients were less lucky, having to rely on unrelated, postmortem donations. Liver patients’ immune systems often attacked the new organ and one-year survival was a low 30 percent. Cyclosporine, an immune-suppressing drug available since 1983, has made a big difference. Now, about 75 percent of adults are alive three years after surgery, and children’s odds are even better. The liver is still a must-have organ, and the need for donor livers has climbed. Today, the options have expanded, with split-liver transplants and partial transplants from living donors.
The first known pedestrian fatality involving a fully autonomous self-driving car will most likely raise questions about the vehicles’ safety.
But “until we know what happened, we can’t really know what this incident means” for the future of self-driving vehicles, says Philip Koopman, a robotics safety expert at Carnegie Mellon University in Pittsburgh. Only when we know more about the crash, including details on the actions of the pedestrian as well as data logs from the car, can we make judgments, he says. The incident took place late Sunday night when a self-driving car operated by Uber hit and, ultimately, killed a woman crossing the street in Tempe, Ariz. Early reports indicate that a human safety driver was at the wheel, and the car was in autonomous mode. In response, Uber has suspended testing of its fleet of self-driving cars in Tempe and other cities across the nation. The National Transportation Safety Board is investigating, the New York Times reports.
The NTSB has previously conducted an investigation into the 2016 death of a man who was driving a partly autonomous Tesla, concluding that the driver ignored multiple safety warnings.
Self-driving cars already face high levels of mistrust from other motorists and potential passengers. In a AAA survey in 2017, 85 percent of baby boomers and 73 percent of millennials reported being afraid to ride in self-driving cars (SN Online: 11/21/17).
It is widely accepted by experts such as Koopman that autonomous cars will eventually be safer drivers than the average person, because the vehicles don’t get distracted, among other things. But proving that safety may be time-consuming. A 2016 study by Nidhi Kalra, an information scientist at the RAND Corporation in San Francisco, found that self-driving cars might have to drive on roads for decades to statistically prove their superior safety. When — or if — self-driving cars are proven safer than human drivers, the vehicles will still have to contend with other questions, such as whether to take steps to protect passengers or pedestrians in a collision (SN: 12/24/16, p. 34).
THE WOODLANDS, Texas — A new map of flat, light-colored streaks and splotches on the moon links the features to a few large impacts that spread debris all over the surface. The finding suggests that some of the moon’s history might need rethinking.
Planetary scientist Heather Meyer, now at the Lunar and Planetary Institute in Houston, used data from NASA’s Lunar Reconnaissance Orbiter to make the map, the most detailed global look at these light plains yet. Previous maps had been patched together from different sets of observations, which made it hard to be sure that features that looked like plains actually were. Astronomers originally assumed that the light plains were ancient lava flows from volcanoes. But rocks brought back from one of these plains by Apollo 16 astronauts in 1972 did not have volcanic compositions. That finding led some scientists to suspect the plains, which cover about 9.5 percent of the lunar surface, came from giant impacts.
Meyer’s map supports the impact idea. Most of the plains, which are visible across the whole moon, seem to originate from debris spewed from the Orientale basin, a 930-kilometer-wide bowl in the moon’s southern hemisphere that formed about 3.8 billion years ago. “It looks like there’s just a giant splat mark,” Meyer says. About 70 percent of the lunar plains come from either Orientale or one other similar basin, she reported March 22 at the Lunar and Planetary Science Conference. “What this is telling us,” she says, “is these large basins modified the entire lunar surface at some point.” The map also shows that some small impact craters up to 2,000 kilometers from Orientale have been filled in with plains material. That’s potentially problematic, because planetary scientists use the number of small impact craters to estimate the age of the lunar surface. If small craters have been erased by an impact half a moon away, that could mean some of the surface is older than it looks, potentially changing scientists’ interpretations of the moon’s history (SN: 6/11/16, p. 10).
China’s first space station, Tiangong-1, is expected to fall to Earth sometime between March 31 and April 1. No fooling.
Most of the 10.4-meter-long station will burn up as it zooms through Earth’s atmosphere. But some parts will survive and reach the ground, according to the European Space Agency’s Space Debris Office. No one can be sure where or when those pieces will hit. Even within hours of the station reaching the atmosphere, the final hit zone predictions will cover thousands of kilometers. ESA predicts that any latitude between 42.8° N (so as far north as Chicago) and 42.8° S (down to Tasmania) is fair game. The geometry of the station’s orbit means that the edges of that zone are more likely to be hit than the equator. Much of that area is oceans or uninhabited. “The personal probability of being hit by a piece of debris from Tiangong-1 is actually 10 million times smaller than the yearly chance of being hit by lightning,” according to ESA. (If you’re wondering, the annual chance of getting zapped in the United States is 1 in 1,083,000.) Launched in 2011, Tiangong-1 — which means Heavenly Palace — was visited twice by Chinese astronauts, in 2012 and in 2013. The craft was supposed to last only two years, and China put it into sleep mode after the second visit to prepare to steer it back to Earth for a controlled reentry. But in March 2016, the Chinese space agency announced that they had lost contact with the craft and expected it to reenter the atmosphere sometime in 2017 Reentry is unlikely to be dangerous, but it will look cool. The disintegrating space station will blaze through the sky like a fireball. ESA and the Chinese space agency are running daily updates on the station’s location, so check back to see if it will be visible where you are.
PHOENIX — A new, breathable material that can also block biological or chemical threats could offer comfortable protection for people working in contaminated environments or dangerous military zones.
The bottom layer of the material, described April 3 at the Materials Research Society spring meeting, features carbon nanotube pores embedded within a flexible synthetic polymer film. These pores are just a few nanometers across — too small for bacterial or viral cells to squeeze through, but wide enough for sweat to escape. The top layer offers further protection. It is made of another, spongy polymer that normally allows water and other molecules to pass through. But when the polymer comes into contact with G-series nerve agents — the family of toxic chemicals that includes sarin gas — it flattens into a dense sheet that seals over the carbon nanopores underneath. The polymer can be restored to its original state by soaking it in a high-pH chemical broth.
Both layers together are still less than half the thickness of a sheet of paper, and could be laid over fabrics without putting the wearer at risk of overheating. That’s an improvement over the typical protective gear that’s permanently sealed against contaminants, said study coauthor Francesco Fornasiero, a chemical engineer at Lawrence Livermore National Laboratory in California.
In early testing, the material completely blocked out dengue virus cells, as well as 90 percent of the chemical diethyl chlorophosphate, used as a stand-in for toxic nerve agents. The researchers are working to make the material even more impervious to dangerous chemicals, Fornasiero said.
About 50 million years ago, a monitor lizard in what is now Wyoming perceived the world through four eyes. Saniwa ensidens is the only known jawed vertebrate to have had two eyelike photosensory structures at the top of the head, in addition to the organs we commonly think of as eyes, researchers report April 2 in Current Biology.
The structures are called the pineal and parapineal organs. Among animals alive today, only the jawless fish called a lamprey has both structures. But many modern reptiles have a so-called third eye, the pineal organ. The researchers examined fossils collected 150 years ago by Yale University students. Scans of the fossils using a technique called X-ray computed tomography revealed spaces in the skull for both the third and fourth eye.
What the ancient lizard did with these organs isn’t known, but some modern vertebrates use the amplified photosensitivity they glean from the pineal glands to navigate. S. ensidens may have been able to perceive polarized light and use the angle of the sun like a compass, as some modern lizards do. Or it may have navigated using Earth’s magnetic field, much like some amphibians and migratory birds.
A new kind of plastic can, when exposed to the right chemicals, break down into the same basic building blocks that it came from and be rebuilt again and again. The recyclable material is more durable than previous attempts to create reusable plastics, researchers report inthe April 27 Science.
Designing plastics that can be easily reused is one line of attack against the global plastic waste problem. Only about 10 percent of plastic ever made gets recycled, according to a 2017 study in Science Advances. But the material is so cheap and useful that hundreds of millions of tons of it keeps getting churned out each year. A major impediment to plastic recycling is that most plastics degrade into molecules that aren’t immediately useful. Transforming those molecules back into plastic or into some other product requires many chemical reactions, which makes the recycling process less efficient. And while biodegradable plastics have become popular in recent years, they break down only if the right microbes are present. More often than not, these plastics end up lingering in landfills or floating in the ocean. Creating plastics that could be broken down into their building blocks and reused without additional processing and purifying could help reduce the pollution buildup.
But designing such a plastic polymer is a balancing act, says Michael Shaver, a polymer chemist at the University of Edinburgh who wasn’t part of the study. Polymers are long chains of small molecules, called monomers, that link together like beads on a string. Monomers that need extreme temperatures or too much chemical coaxing to join up into polymers might not be practical building blocks. And resulting polymers need to be stable up to a high enough temperature that, say, pouring hot coffee into a cup made of them won’t destabilize the chains and make the plastic melt into a sticky puddle. Polymer chemist Jianbo Zhu and his colleagues at Colorado State University in Fort Collins set out to solve this challenge. The team had had some luck in the past creating a polymer that could be broken down into its starting molecules. But the resulting plastics created by their lab and others on the same track were too soft and temperature-sensitive to have much practical use. This time, Zhu and his colleagues modified one of their previous creations, a small ringed molecule, by adding another ring in a way that braced the molecule into a particular conformation. That rigidity helped the monomers quickly link together at room temperature into polymer chains that are heat-stable. Then, when exposed to certain mild chemicals or high enough heat, the polymers degraded back into monomers. The researchers were able to repeat this cycle several times, showing that, in theory, the polymer could be infinitely recyclable.
While each monomer is locked into a particular conformation, not all of them have the same shape even though they’re made from the same chemical recipe. Mixing two different conformations of monomers created an even stronger plastic, says Zhu.
“This is probably the best system out there,” Shaver says.
Still, it’s not perfect yet: Zhu and his colleagues plan to tinker with the monomer design more in the future to make the resulting plastic a bit less brittle. Eventually, they hope to commercialize the product.
