Zika disrupts cellular processes to impair brain development

VANCOUVER — Zika virus’s tricks for interfering with human brain cell development may also be the virus’s undoing.

Zika infection interferes with DNA replication and repair machinery and also prevents production of some proteins needed for proper brain growth, geneticist Feiran Zhang of Emory University in Atlanta reported October 19 at the annual meeting of the American Society of Human Genetics.

Levels of a protein called p53, which helps control cell growth and death, shot up by 80 percent in human brain cells infected with the Asian Zika virus strain responsible for the Zika epidemic in the Americas, Zhang said. The lab dish results are also reported in the Oct. 14 Nucleic Acids Research. Increased levels of the protein stop developing brain cells from growing and may cause the cells to commit suicide.
A drug that inactivates p53 stopped brain cells from dying, Zhang said. Such p53 inhibitors could help protect developing brains in babies infected with Zika. But researchers would need to be careful giving such drugs because too little p53 can lead to cancer.

Zika also makes small RNA molecules that interfere with production of proteins needed for DNA replication, cell growth and brain development, Zhang said. In particular, a small viral RNA called vsRNA-21 reduced the amount of microcephalin 1 protein made in human brain cells in lab dishes. The researchers confirmed the results in mouse experiments. That protein is needed for brain growth; not enough leads to the small heads seen in babies with microcephaly. Inhibitors of the viral RNAs might also be used in therapies, Zhang suggested.

With climate change, grizzly bears may hibernate less

Rocky Mountain hikers might need to start packing more bear spray: Climate change may reduce the time that grizzly bears spend in hibernation — leaving them more time to scare the crap out of any humans wandering in their territory.

Scientists aren’t really concerned about bear hibernation because of unwary hikers, of course. It’s because hibernation is an important time of year for a grizzly bear. By going into hibernation and suppressing their metabolisms, the bears can reduce the amount of energy they expend by some 85 percent and more easily get through months when food supplies are short and weather is bleak. Plus, this is when pregnant females give birth and start raising their young. Disrupt hibernation time and a bear is set for a bad — and potentially deadly — year.

And then there’s the fact that in some places, grizzly bears aren’t doing so well. That’s true in Alberta, Canada, where the bears, already low in number, have been threatened by habitat loss and human hunters and have low reproductive rates.

Karine Pigeon of Laval University in Quebec City and colleagues wanted to know whether they should add climate change to that list of threats. But first they needed more information about the factors that drive the bears into and out of their dens. The bears don’t go into or leave hibernation on specific dates (apparently they don’t use our calendar system), so how do they know when it’s time to hibernate?

To find out, the team captured 15 male and 58 female grizzly bears from 1999 to 2011 in an area along the Alberta-British Columbia border northwest of Calgary. The bears were weighed and measured and fitted with tracking collars. Because the signals from the collars couldn’t be tracked from inside the bears’ dens, the researchers knew when the animals entered and left hibernation. The scientists also collected information about the local weather and the availability of berries, one of the bears’ preferred foods.

No single factor explained the dates on which the grizzlies entered and left hibernation, but some were more important than others, the team reports in the October Behavioral Ecology and Sociobiology. Pregnant females, for instance, entered their dens on average two weeks earlier than males, and the ones that had given birth and had cubs emerged two weeks later. This matched what scientists know about bear denning habits, which are thought to promote the cubs’ safety and development.

The end of hibernation tended to be linked to weather and elevation. A bear denning at high elevation in a year in which spring arrived late would stay snug and warm in its den for longer than a grizzly lower down and when spring arrived early.
The den entry date, though, wasn’t tied to weather. It was partially linked to the availability of food: When there were plenty of tasty berries available, grizzlies tended to stay out and keep eating.

And this is where there’s a problem regarding climate change, the researchers note. Because if longer autumns promote the plentiful production of berries, and earlier springs are bringing milder conditions that prompt bears to leave their dens, then grizzlies may hibernate less. That could have repercussions for females with cubs, the researchers note, because it may lead to smaller, more vulnerable cubs being led out into the open — where humans or other bears could kill them.

‘A Most Improbable Journey’ offers scientific take on human history

Most people do not marvel much at sand. We may enjoy how it feels under our bare feet, or get annoyed when someone tracks it into the house. But few of us see those quartz grains the way geologist Walter Alvarez does — as the product of 4.5 billion years of improbable cosmic and geologic events that defined the course of human history.

Sandy beaches exist because silicon — a relatively rare element in the solar system — happened to become concentrated on Earth during the solar system’s early days, Alvarez, of the University of California, Berkeley, writes in A Most Improbable Journey. While powerful solar particles swept lighter, gaseous elements toward the outer planets, more massive, mineral-forming elements such as silicon, magnesium and iron were left behind for Earth. Later on, in the molten crucibles between Earth’s colliding tectonic plates, these elements formed the raw materials for pivotal human inventions, including stone tools, glass and computer chips.
The 4.5 billion years of history that led to a computer chip is just one of many stories of scientific happenstance that Alvarez presents. Best known for proposing that an asteroid impact killed off the dinosaurs, Alvarez argues that rare, unpredictable cosmic, geologic and biological events — what he calls “contingencies” — are key to understanding the human condition.

Fans of Bill Bryson’s A Short History of Nearly Everything will appreciate Alvarez’s enthusiastic, clearly written tour of contingencies that have shaped our world, starting with the origins of life on Earth. No matter how distant the event, Alvarez quickly zeroes in on its eventual impact on people: For instance, the formation of oceanic crust helped expose rich deposits of copper ore on Cyprus, later an epicenter of the Bronze Age. A catastrophic Ice Age flood formed the English Channel in which the Spanish Armada would later sink. And ancient rivers in North America smoothed the terrain of the westward trail for American pioneers in covered wagons.

Not all of Alvarez’s arguments are convincing — his claim in the final chapter that every individual is a “contingency” in his or her own right, given how many other people could have been born instead, feels more flattering than important. Still, it’s hard to argue with his observation that impulsive human actions can transform the planet just as much as earthquakes, asteroids and other difficult-to-predict, occasionally world-changing phenomena.

Critics of this macro view, described in academia as “Big History,” say that the approach sacrifices important nuance and detail. At roughly 200 pages of text, however, A Most Improbable Journey does not claim to be a comprehensive account of history or a replacement for more detailed, focused examinations of the past. Instead, it makes a compelling case for Big History as a fun, perspective-stretching exercise — a way to dust off familiar topics and make them sparkle.

Muon surplus leaves physicists searching for answers

Muons, electrons’ heftier cousins, rain down through the Earth’s atmosphere in numbers higher than physicists expect. The discrepancy could simply point to a gap in physicists’ understanding of the nitty-gritty physics of particle interactions, or perhaps something unexpected is going on, such as the creation of a new state of matter.

When cosmic rays — spacefaring protons or atomic nuclei — smash into the atmosphere at ultrahigh energies, they launch a cascade of many other types of particles, including muons. New observations made at the Pierre Auger Observatory detect about 30 percent more muons than simulations predict, scientists report October 31 in Physical Review Letters.
The Auger observatory, located in Argentina, uses telescopes to observe faint light from particle showers in the atmosphere, and detects particles that reach the ground using tanks of water. By comparing simulated particle showers to real data, and allowing for possible miscalibration of their detectors, the scientists concluded that the predicted numbers of muons don’t match up with reality. Hints of the muon excess have been popping up since the ’90s, says physicist Thomas Gaisser of the University of Delaware. But the new measurement is “a better job, which confirms the excess compared to what’s predicted by the models.”

The ultrahigh energy cosmic rays that the researchers analyzed probe physics at energies 10 times those reached at the world’s most powerful particle accelerator, the Large Hadron Collider, potentially allowing scientists to detect new phenomena. But, says Spencer Klein of the Lawrence Berkeley National Laboratory in California, “it’s premature to say that this is something really interesting.” He suggests that the discrepancy could simply be due to an incomplete grasp of the physics of how protons and neutrons inside a nucleus behave when nuclei collide. The complexities of that behavior could result in particles that eventually decay into more muons than scientists naïvely expected, thus explaining the glut.

But, says Auger physicist Glennys Farrar of New York University, scientists have unsuccessfully tried to explain the muon surplus using standard physics for many years. “That’s in a way the most convincing reason to think that there may be new physics.” An explanation Farrar favors is a phenomenon in which a new state of matter appears at high energies. In such a state, large numbers of gluons — particles that transmit the strong nuclear force — may behave collectively, like photons in sync in a laser. If enough energy is pumped in by the cosmic rays, the gluons could “start to develop a life of their own,” Farrar says. The gluons might then gang up into hypothetical particles called glueballs, which could decay into particles that produce more muons.

New analysis boosts case for smaller proton

Editor’s Note: After this article was published, Horbatsch and colleagues discovered an error in their analysis, which weakened the conclusions. The new calculation of the proton radius falls in between the two previous estimates, and therefore does not add much additional support for the smaller proton.

A spat over the size of the proton just got a bit more complicated.

Measurements of the proton’s radius disagree, with one group of scientists saying it’s smaller than the accepted estimate. Now, a new analysis of old data bolsters the case for a small proton. But the result may dash hopes that the discrepancy could point the way to new physics.
Scientists at York University in Toronto and the Autonomous University of Barcelona reanalyzed data from a 2010 electron scattering experiment at the Mainz Microtron in Germany, in which physicists bombarded protons with electrons and observed how the electrons ricocheted. That scattering, under the influence of the protons’ spheres of positive charge, allows scientists to tease out the size of a proton. The updated estimate came up small, the scientists report November 1 on arXiv.org.

“I think it’s not going to be easy for the proponents of a relatively large proton radius to just discuss this away,” says physicist Randolf Pohl of the Max Planck Institute of Quantum Optics in Garching, Germany. “But I’m not convinced that people will accept it.”

Until several years ago, scientists’ various techniques for sizing up the proton were in agreement. Electron scattering studies like the Mainz experiment implied the same size proton as a second technique, which involves studying the energy levels of hydrogen atoms. These estimates indicated that the proton’s radius was about 0.88 quadrillionths of a meter. But in 2010, a new technique caused a kerfuffle. Measurements of the proton radius using muonic hydrogen — a hydrogen atom with its electron replaced by a heavier relative called a muon — pegged the proton to a size 4 percent smaller than the other estimates (SN: 7/31/10, p. 7).

The flaw among the three techniques might seem likely to lie with the one outlier, the muon experiment. But “there’s actually quite a bit of certainty about those results,” says physicist Marko Horbatsch of York University, a coauthor of the new paper. So Horbatsch and colleagues decided to revisit electron scattering instead, using a subset of the data from the Mainz experiment. Horbatsch’s team focused on glancing collisions where the electron altered its course only slightly. Those collisions are the most essential for determining the proton radius. Then the researchers used theoretical calculations to account for effects that occur in more extreme collisions. Their analysis revealed a slightly scaled-down proton.

If the result is reinforced by future electron scattering measurements, the hydrogen atom data that resulted in the larger-sized proton would still require explanation. But it would also mean that the discrepancy won’t lead to new insights about the universe. Under the standard model of particle physics, muons and electrons should be identical except for mass. Physicists had hoped that the black sheep status of the muonic hydrogen experiment indicated something was different about muons. Agreement of the electron scattering and muonic hydrogen experiments eliminates that possible explanation.
The new analysis is “undoubtedly sensible,” says physicist Judith McGovern of the University of Manchester. “I’m a bit surprised no one has done it before. In fact, I’m a bit surprised I haven’t done it before.”

But that doesn’t mean scientists are fully convinced. MIT physicist Jan Bernauer, one of the authors of the original electron scattering result, says he doesn’t think the puzzle will be solved by reanalysis of existing data. “I’m positive that new data are needed.”

In some ways, hawks hunt like humans

A hunter’s gaze betrays its strategy. And looking at what an animal looks at when it’s hunting for prey has revealed foraging patterns in humans, other primates — and now, birds.

Suzanne Amador Kane of Haverford College in Pennsylvania and her colleagues watched archival footage of three raptor species hunting: northern goshawks (Accipiter gentilis), Cooper’s hawks (A. cooperii) and red-tailed hawks (Buteo jamaicensis). They also mounted a video camera to the head of a goshawk to record the bird’s perspective (a technique that’s proved useful in previous studies of attack behavior). The team noted how long birds spent fixating on specific points before giving up, moving their head and, thus, shifting their gaze.

When searching for prey, raptors don’t turn their heads in a predictable pattern. Instead, they appear to scan and fixate randomly based on what they see in their environment, Kane and her colleagues report November 16 in The Auk. In primates, a buildup of sensory information drives foraging animals to move their eyes in similar patterns.

Though the new study only examines three species and focuses on head tracking rather than eye tracking, Kane and her colleagues suggest that the same basic neural processes may drive search decisions of human and hawk hunters.

Cretaceous bird find holds new color clue

A 130-million-year-old bird holds a clue to ancient color that has never before been shown in a fossil.

Eoconfuciusornis’ feathers contain not only microscopic pigment pods called melanosomes, but also evidence of beta-keratin, a protein in the stringy matrix that surrounds melanosomes, Mary Schweitzer and colleagues report November 21 in the Proceedings of the National Academy of Sciences.

Together, these clues could strengthen the case for inferring color from dinosaur fossils, a subject of debate for years (SN: 11/26/16, p. 24). Schweitzer, a paleontologist at North Carolina State University in Raleigh, has long pointed out that the microscopic orbs that some scientists claim are melanosomes may actually be microbes. The two look similar, but they have some key differences. Microbes aren’t enmeshed in keratin, for one.

In Eoconfuciusornis’ feathers, Schweitzer and colleagues found round, 3-D structures visible with the aid of an electron microscope. And a molecular analysis revealed bundles of skinny fibers, like the filaments of beta-keratin in modern feathers. The authors don’t speculate on the bird’s color, but they do offer a new way to support claims for ancient pigments.

“Identifying keratin is key to ruling out a microbial source for microbodies identified in fossils,” they write.

Ice gave Pluto a heavy heart

Pluto’s heart might carry a heavy burden.

Weight from massive deposits of frozen nitrogen, methane and carbon monoxide, built up billions of years ago, could have carved out the left half of the dwarf planet’s heart-shaped landscape, researchers report online November 30 in Nature.

The roughly 1,000-kilometer-wide frozen basin dubbed Sputnik Planitia was on display when the New Horizons spacecraft tore past in July 2015 (SN: 12/26/15, p. 16). Previous studies have proposed that the region could be a scar left by an impact with interplanetary debris (SN: 12/12/15, p. 10).

Sputnik Planitia sits in a cold zone, a prime location for ice to build up, planetary scientist Douglas Hamilton of the University of Maryland in College Park and colleagues calculate. Excess ice deposited early in the planet’s history would have led to a surplus of mass. Gravitational interactions between Pluto and its largest moon, Charon, slowed the planet’s rotation until that mass faced in the opposite direction from Charon. Once Charon became synced to Pluto’s rotation — it’s always over the same spot on Pluto — gravity would have held Sputnik Planitia in Pluto’s cold zone, attracting even more ice. As the ice cap grew, the weight could have depressed Pluto’s surface, creating the basin that exists today.

Gut microbe mix may spark Parkinson’s

For clues to Parkinson’s brain symptoms, a gut check is in order.

Intestinal microbes send signals that set off the disease’s characteristic brain inflammation and motor problems in mice, researchers report December 1 in Cell. Doctors might someday be able to treat Parkinson’s by fixing this bacterial imbalance.

“It’s quite an exciting piece of work,” says John Cryan, a neuroscientist at University College Cork in Ireland who wasn’t involved in the study. “The relationship between the brain and gut for Parkinson’s has been bubbling up for many years.” The new research, he says, “brings the microbiome really into the forefront for the first time.”
Parkinson’s affects more than 10 million people worldwide, and roughly 70 percent of those patients also have gastrointestinal issues like constipation. Sometimes the GI symptoms show up years before the muscle weakness and other neurological problems. Several recent studies in humans have suggested a link between gut microbes and Parkinson’s. But it wasn’t clear whether intestinal microbes were actually causing the disease, says study coauthor Sarkis Mazmanian, a microbiologist at Caltech. “What our study adds is a functional, mechanistic role for the microbiome.”

Mazmanian’s team studied mice that produced too much alpha-synuclein, the protein that’s believed to cause Parkinson’s when it clumps in the brain. Mice with extra alpha-synuclein acted like they had Parkinson’s: They traversed a narrow beam more slowly, they couldn’t grip as well to a pole and they struggled to pull stickers off their noses. Their brains showed signs of inflammation, too. But when the researchers raised the same type of mice to be germ-free —that is, to not have any gut microbes — the animals acted less sick.

Those mice were still producing boatloads of alpha-synuclein, but the protein wasn’t clumping in their brains. And without the clumps, the mice didn’t have the unsteady gait and muscle weakness typical of Parkinson’s.

In another experiment, the researchers transferred gut microbes from Parkinson’s patients into germ-free mice making too much alpha-synuclein. Those mice developed motor problems when tested 6 or 7 weeks after the transfer, but mice who got microbes from healthy humans were fine.

“Even though the mice that received the healthy microbiota received hundreds of bacteria, they didn’t get the disease,” says Mazmanian. That suggests it’s not the presence or absence of bacteria that triggers Parkinson’s, but the specific composition of the microbial cocktail.
Alpha-synuclein clumps can move from the gut to the brain, a recent study showed. Now, it seems that gut bacteria themselves are also sending important signals.

Researchers are now trying to figure out which signals — and which microbes —are throwing off the balance.

Fecal samples from the mice implanted with bacteria from Parkinson’s patients had higher than normal levels of certain intestinal bacteria. That could be sparking symptoms, says Caltech microbiologist Tim Sampson, who also worked on the study. “I’m interested in trying to understand if there are potential pathogenic microbes that might be individually driving the disease,” he says. “Once we’ve figured that out we’ll be able to understand whether we can remove that group of organisms or block them.”

Abnormally low levels of other bacteria could also factor in. The analyses aren’t large enough to firmly conclude which microbes are particularly important players. But if scientists can figure out what those missing beneficial bacteria are, Mazmanian says, targeted probiotic therapy might be a treatment option in the future.

Aging-associated diseases like Parkinson’s are tricky to study in mice, cautions Stanford University microbiologist Justin Sonnenburg. “They’re typically the result of decades of accumulations of problems,” whereas the mice in the current study were just a couple months old. So the findings will need to be validated in human studies before influencing treatments. Still, he says, “it’s a really important contribution to the growing list of ways that gut microbes can alter our health.”

Graphene Silly Putty detects pitter-patter of spider footsteps

Graphene-infused Silly Putty forms an electrical sensor that is sensitive enough to detect the gentle caresses of spider feet walking across it.

Mixing graphene, or atom-thick sheets of carbon, and polysilicone, the substance found in the children’s toy Silly Putty, made it conduct electricity. Its electrical resistance was highly sensitive to pressure: Squishing the putty caused the graphene sheets within to shift and disconnect, impeding the flow of electricity.

When placed on a person’s neck over the carotid artery, the putty could monitor pulse and blood pressure via changes in the material’s resistance. The putty could also detect breathing and finger motions. To illustrate just how sensitive the sensor was, scientists coaxed a small spider to walk over the putty; the sensor registered the spider’s footfalls, researchers report December 9 in Science.