Certain marine worms spend their larval phase as little more than a tiny, transparent “swimming head.” A new study explores the genes involved in that headfirst approach to life.
A mud flat in Morro Bay, Calif., is the only known place where this one species of acorn worm, Schizocardium californicum, is found. After digging up the creatures, Paul Gonzalez, an evolutionary developmental biologist at Stanford University, raised hordes of the larvae at Stanford’s Hopkins Marine Station in Pacific Grove, Calif. Because a larva and an adult worm look so different, scientists wondered if the same genes and molecular machinery were involved in both phases of development. To find out, Gonzalez and colleagues analyzed the worm’s genetic blueprint during each phase, they report online December 8 in Current Biology.
Genes linked to trunk development were switched off during the larval phase until just before metamorphosis. Instead, most of the genes switched on were associated with head development, Gonzalez says.
The larvae hatch from eggs laid on the mud. When tides flood the area, the squishy, gel-filled animals use hairlike cilia to swim upwards to devour bits of algae. “They’re feeding machines,” Gonzalez says. He speculates that being balloon-shaped noggins, rather than wriggling noodles, may help the organisms float and feed more efficiently.
After about two months of gorging at the algae buffet, the larvae, which grow to roughly 2 millimeters across, transform and sink back into the muck. There, they eventually grow a body that can stretch up to about 40 centimeters.
Look at any map of the Atlantic Ocean, and you might feel the urge to slide South America and Africa together. The two continents just beg to nestle next to each other, with Brazil’s bulge locking into West Africa’s dimple. That visible clue, along with several others, prompted Alfred Wegener to propose over a century ago that the continents had once been joined in a single enormous landmass. He called it Pangaea, or “all lands.”
Today, geologists know that Pangaea was just the most recent in a series of mighty super-continents. Over hundreds of millions of years, enormous plates of Earth’s crust have drifted together and then apart. Pangaea ruled from roughly 400 million to about 200 million years ago. But wind the clock further back, and other supercontinents emerge. Between 1.3 billion and 750 million years ago, all the continents amassed in a great land known as Rodinia. Go back even further, about 1.4 billion years or more, and the crustal shards had arranged themselves into a supercontinent called Nuna.
Using powerful computer programs and geologic clues from rocks around the world, researchers are painting a picture of these long-lost worlds. New studies of magnetic minerals in rock from Brazil, for instance, are helping pin the ancient Amazon to a spot it once occupied in Nuna. Other recent research reveals the geologic stresses that finally pulled Rodinia apart, some 750 million years ago. Scientists have even predicted the formation of the next supercontinent — an amalgam of North America and Asia, evocatively named Amasia — some 250 million years from now. Reconstructing supercontinents is like trying to assemble a 1,000-piece jigsaw puzzle after you’ve lost a bunch of the pieces and your dog has chewed up others. Still, by figuring out which puzzle pieces went where, geologists have been able to illuminate some of earth science’s most fundamental questions. For one thing, continental drift, that gradual movement of landmasses across Earth’s surface, profoundly affected life by allowing species to move into different parts of the world depending on what particular landmasses happened to be joined. (The global distribution of dinosaur fossils is dictated by how continents were assembled when those great animals roamed.)
Supercontinents can also help geologists hunting for mineral deposits — imagine discovering gold ore of a certain age in the Amazon and using it to find another gold deposit in a distant landmass that was once joined to the Amazon. More broadly, shifting landmasses have reshaped the face of the planet — as they form, supercontinents push up mountains like the Appalachians, and as they break apart, they create oceans like the Atlantic.
“The assembly and breakup of these continents have profoundly influenced the evolution of the whole Earth,” says Johanna Salminen, a geophysicist at the University of Helsinki in Finland. Push or pull For centuries, geologists, biogeographers and explorers have tried to explain various features of the natural world by invoking lost continents. Some of the wilder concepts included Lemuria, a sunken realm between Madagascar and India that offered an out-there rationale for the presence of lemurs and lemurlike fossils in both places, and Mu, an underwater land supposedly described in ancient Mayan manuscripts. While those fantastic notions have fallen out of favor, scientists are exploring the equally mind-bending story of the supercontinents that actually existed. Earth’s constantly shifting jigsaw puzzle of continents and oceans traces back to the fundamental forces of plate tectonics. The story begins in the centers of oceans, where hot molten rock wells up from deep inside the Earth along underwater mountain chains. The lava cools and solidifies into newborn ocean crust, which moves continually away from either side of the mountain ridge as if carried outward on a conveyor belt. Eventually, the moving ocean crust bumps into a continent, where it either stalls or begins diving beneath that continental crust in a process called subduction.
Those competing forces — pushing newborn crust away from the mid-ocean mountains and pulling older crust down through subduction — are constantly rearranging Earth’s crustal plates. That’s why North America and Europe are getting farther away from each other by a few centimeters each year as the Atlantic widens, and why the Pacific Ocean is shrinking, its seafloor sucked down by subduction along the Ring of Fire — looping from New Zealand to Japan, Alaska and Chile.
By running the process backward in time, geologists can begin to see how oceans and continents have jockeyed for position over millions of years. Computers calculate how plate positions shifted over time, based on the movements of today’s plates as well as geologic data that hint at their past locations.
Those geologic clues — such as magnetic minerals in ancient rocks — are few and far between. But enough remain for researchers to start to cobble together the story of which crustal piece went where.
“To solve a jigsaw puzzle, you don’t necessarily need 100 percent of the pieces before you can look at it and say it’s the Mona Lisa,” says Brendan Murphy, a geophysicist at St. Francis Xavier University in Antigonish, Nova Scotia. “But you need some key pieces.” He adds: “With the eyes and nose, you have a chance.”
No place like Nuna For ancient Nuna, scientists are starting to find the first of those key pieces. They may not reveal the Mona Lisa’s enigmatic smile, but they are at least starting to fill in a portrait of a long-vanished supercontinent.
Nuna came together starting around 2 billion years ago, with its heart a mash-up of Baltica (the landmass that today contains Scandinavia), Laurentia (which is now much of North America) and Siberia. Geologists argue over many things involving this first supercontinent, starting with its name. “Nuna” is from the Inuktitut language of the Arctic. It means lands bordering the northern oceans, so dubbed for the supercontinent’s Arctic-fringing components. But some researchers prefer to call it Columbia after the Columbia region of North America’s Pacific Northwest.
Whatever its moniker, Nuna/Columbia is an exercise in trying to get all the puzzle pieces to fit. Because Nuna existed so long ago, subduction has recycled many rocks of that age back into the deep Earth, erasing any record of what they were doing at the time. Geologists travel to rocks that remain in places like India, South America and North China, analyzing them for clues to where they were at the time of Nuna.
One of the most promising techniques targets magnetic minerals. Paleomagnetic studies use the minerals as tiny time capsule compasses, which recorded the direction of the magnetic field at the time the rocks formed. The minerals can reveal information about where those rocks used to be, including their latitude relative to where the Earth’s north magnetic pole was at the time.
Salminen has been gathering paleomagnetic data from Nuna-age rocks in Brazil and western Africa. Not surprisingly, given their current lock-and-key configuration, these two chunks were once united as a single ancient continental block, known as the Congo/São Francisco craton. For millions of years, it shuffled around as a single geologic unit, occasionally merging with other blocks and then later splitting away.
Salminen has now figured out where the Congo/São Francisco puzzle piece fit in the jigsaw that made up Nuna. In 1.5-billion-year-old rocks in Brazil, she unearthed magnetic clues that placed the Congo/São Francisco craton at the southeastern tip of Baltica all those years ago. She and her colleagues reported the findings in November in Precambrian Research.
It is the first time scientists have gotten paleomagnetic information about where the craton may have been as far back as Nuna. “This is quite remarkable — it was really needed,” she says. “Now we can say Congo could have been there.” Like building out a jigsaw puzzle from its center, the work essentially expands Nuna’s core.
Rodinia’s radioactive decay By around 1.3 billion years ago, Nuna was breaking apart, the pieces of the Mona Lisa face shattering and drifting away from each other. It took another 200 million years before they rejoined in the configuration known as Rodinia.
Recent research suggests that Rodinia may not have looked much different than Nuna, though. The Mona Lisa in its second incarnation may still have looked like the portrait of a woman — just maybe with a set of earrings dangling from her lobes. of Carleton University in Ottawa, Canada, recently explored the relative positions of Laurentia and Siberia between 1.9 billion and 720 million years ago, a period that spans both Nuna and Rodinia. Ernst’s group specializes in studying “large igneous provinces” — the huge outpourings of lava that build up over millions of years. Often the molten rock flows along sheetlike structures known as dikes, which funnel magma from deep in the Earth upward.
By using the radioactive decay of elements in the dike rock, such as uranium decaying to lead, scientists can precisely date when a dike formed. With enough dates on a particular dike, researchers can produce a sort of bar code that is unique to each dike. Later, when the dikes are broken apart and shifted over time, geologists can pinpoint the bar codes that match and thus line up parts of the crust that used to be together.
Ernst’s team found that dikes from Laurentia and Siberia matched during four periods between 1.87 billion and 720 million years ago — suggesting they were connected for that entire span, the team reported in June in Nature Geoscience. Such a long-term relationship suggests that Siberia and Laurentia may have stuck together through the Nuna-Rodinia transition, Ernst says.
Other parts of the puzzle tend to end up in the same relative locations as well, says Joseph Meert, a paleomagnetist at the University of Florida in Gainesville. In each supercontinent, Laurentia, Siberia and Baltica knit themselves together in roughly the same arrangement: Siberia and Baltica nestle like two opposing knobs on one end of Laurentia’s elongated blob. Meert calls these three continental fragments “strange attractors,” since they appear conjoined time after time.
It’s the outer edges of the jigsaw puzzle that change. Fragments like north China and southern Africa end up in different locations around the supercontinent core. “I call those bits the lonely wanderers,” Meert says.
Getting to know Pangaea While some puzzle-makers try to sort out the reconstructions of past supercontinents, other geologists are exploring deeper questions about why big landmasses come together in the first place. And one place to look is Pangaea.
“Most people would accept what Pangaea looks like,” Murphy says. “But as soon as you start asking why it formed, how it formed and what processes are involved — then all of a sudden you run into problems.” Around 550 million years ago, subduction zones around the edges of an ancient ocean began dragging that oceanic crust under continental crust. But around 400 million years ago, that subduction suddenly stopped. In a major shift, a different, much younger seafloor began to subduct instead beneath the continents. That young ocean crust kept getting sucked up until it all disappeared, and the continents were left merged in the giant mass of Pangaea.
Imagine in today’s world, if the Pacific stopped shrinking and all of a sudden the Atlantic started shrinking instead. “That’s quite a significant problem,” Murphy says. In unpublished work, he has been exploring the physics of how plates of oceanic and continental crust — which have different densities, buoyancies and other physical characteristics — could have interacted with one another in the run-up to Pangaea.
Supercontinent breakups are similarly complicated. Once all the land amasses in a single big chunk, it cannot stay together forever. In one scenario, its sheer bulk acts as an electric blanket, allowing heat from the deep Earth to pond up beneath it until things get too hot and the supercontinent splinters (SN: 1/21/17, p. 14). In another, physical stressors pull the supercontinent apart.
Peter Cawood, a geologist at the University of St. Andrews in Fife, Scotland, likes the second option. He has been studying mountain ranges that arose when the crustal plates that made up Rodinia collided, pushing up soaring peaks where they met. These include the Grenville mountain-building event of about 1 billion years ago, traces of which linger today in the eroded peaks of the Appalachians. Cawood and his colleagues analyzed the times at which such mountains appeared and put together a detailed timeline of what happened as Rodinia began to break apart.
They note that crustal plates began subducting around the edges of Rodinia right around the time of its breakup. That sucking down of crust caused the supercontinent to be pulled from all directions and eventually break apart, Cawood and his colleagues wrote in Earth and Planetary Science Letters in September. “The timing of major breakup corresponds with this timing of opposing subduction zones,” he says. The future is Amasia That stressful situation is similar to what the Pacific Ocean finds itself in today. Because it is flanked by subduction zones around the Ring of Fire, the Pacific Plate is shrinking over time. Some geologists predict that it will vanish entirely in the future, leaving North America and Asia to merge into the next supercontinent, Amasia. Others have devised different possible paths to Amasia, such as closing the Arctic Ocean rather than the Pacific.
“Speculation about the future supercontinent Amasia is exactly that, speculation,” says geologist Ross Mitchell of Curtin University in Perth, Australia, who in 2012 helped describe the mechanics of how Amasia might arise. “But there’s hard science behind the conjecture.”
For instance, Masaki Yoshida of the Japan Agency for Marine-Earth Science and Technology in Yokosuka recently used sophisticated computer models to analyze how today’s continents would continue to move atop the flowing heat of the deep Earth. He combined modern-day plate motions with information on how that internal planetary heat churns in three dimensions, then ran the whole scenario into the future. In a paper in the September Geology, Yoshida describes how North America, Eurasia, Australia and Africa will end up merged in the Northern Hemisphere.
No matter where the continents are headed, they are destined to reassemble. Plate tectonics says it will happen — and a new supercontinent will shape the face of the Earth. It might not look like the Mona Lisa, but it might just be another masterpiece.
Marijuana’s medical promise deserves closer, better-funded scientific scrutiny, a new state-of-the-science report concludes.
The report, released January 12 by the National Academies of Sciences, Engineering and Medicine in Washington, D.C., calls for expanding research on potential medical applications of cannabis and its products, including marijuana and chemical components called cannabinoids.
Big gaps in knowledge remain about health effects of cannabis use, for good or ill. Efforts to study these effects are hampered by federal classification of cannabis as a Schedule 1 drug, meaning it has no accepted medical use and a high potential for abuse. Schedule 1 status makes it difficult for researchers to access cannabis. The new report recommends reclassifying the substance to make it easier to study. Recommendations from the 16-member committee that authored the report come at a time of heightened acceptance of marijuana and related substances. Cannabis is a legal medical treatment in 28 states and the District of Columbia. Recreational pot use is legal in eight of those states and the District.
“The legalization and commercialization of cannabis has allowed marketing to get ahead of science,” says Raul Gonzalez, a psychologist at Florida International University in Miami who reviewed the report before publication. While the report highlights possible medical benefits, Gonzalez notes that it also underscores negative consequences of regular cannabis use. These include certain respiratory and psychological problems.
A 2015 survey indicated that around 22 million people in the United States ages 12 and older ingested some form of cannabis in the last month, mainly as a recreational drug. Roughly 10 percent of those people reported using cannabis solely for medical reasons and 36 percent reported a mix of recreational and medical use.
“This growing acceptance, accessibility and use of cannabis and its derivatives have raised important public health concerns,” says committee chair Marie McCormick, a Harvard T.H. Chan School of Public Health pediatrician.
She and her committee colleagues considered more than 10,700 abstracts of studies on cannabis’s health effects published between January 1, 1999, and August 1, 2016. The committee gave special weight to research reviews published since 2011. Cannabis and cannabinoids show medical potential, the report concludes. Evidence indicates that these substances substantially reduce chronic pain in adults. Cannabis derivatives ingested in pills by multiple sclerosis patients temporarily reduce self-reported muscle spasms (SN: 6/19/10, p. 16). Cannabinoids also help to prevent and lessen chemotherapy-induced nausea and vomiting in adults.
Less conclusive evidence suggests cannabis and cannabinoids improve sleep for adults with sleep apnea, fibromyalgia, chronic pain and multiple sclerosis, the report says.
“If cannabis was to be classified as a medicine, then it needs to be rigorously tested like all other medicines,” says pharmacologist Karen Wright of Lancaster University in England. She hopes the new report spurs researchers to develop standards for the chemical composition of cannabis products tested as possible medical treatments. Despite cannabis’s medical promise, scientists have more questions than answers about how its use influences physical and mental health.
Encouragingly, studies reviewed by the committee suggest that smoking marijuana, unlike smoking cigarettes, does not increase the chances of developing lung, head and neck cancers. But pot’s relationship to other cancers — as well as to heart attacks, strokes and diabetes — is unclear. And few or no findings support the use of cannabis to treat Tourette’s syndrome, post-traumatic stress disorder, cancer, epilepsy (SN Online: 4/13/15) or other medical ailments.
Evidence does not conclusively link marijuana smoking to respiratory diseases such as asthma. But regular pot use tends to accompany increased chronic bronchitis episodes and an intensified cough and phlegm production, at least until smoking stops.
Cannabis smoke may deter infection-related inflammation in the body. But data are sparse on whether cannabis or its derivatives influence immune responses in healthy people or those with HIV.
There are some clear downsides to consuming marijuana and related substances, the new report adds. Solid scientific support exists for a link between cannabis use and later development of psychotic disorders such as schizophrenia. A moderate relationship exists between cannabis use and the development of addictions to alcohol, tobacco and illegal drugs.
Fairly strong evidence points to learning, memory and attention problems immediately after smoking marijuana. Limited data, however, tie pot use to academic problems, dropping out of school, unemployment or lowered income in adulthood.
An asteroid bombardment that some say triggered an explosion of marine animal diversity around 471 million years ago actually had nothing to do with it.
Precisely dating meteorites from the salvo, researchers found that the space rock barrage began at least 2 million years after the start of the Great Ordovician Biodiversification Event. So the two phenomena are unrelated, the researchers conclude January 24 in Nature Communications.
Some scientists had previously proposed a causal link between the two events: Raining debris from an asteroid breakup (SN: 7/23/16, p. 4) drove evolution by upsetting ecosystems and opening new ecological niches. The relative timing of the impacts and biodiversification was uncertain, though. Geologist Anders Lindskog of Lund University in Sweden and colleagues examined 17 crystals buried alongside meteorite fragments. Gradual radioactive decay of uranium atoms inside the crystals allowed the researchers to accurately date the sediment layer to around 467.5 million years ago. Based in part on this age, the researchers estimate that the asteroid breakup took place around 468 million years ago. That’s well after fossil evidence suggests that the diversification event kicked off.
Other forces such as climate change and shifting continents instead promoted biodiversity, the researchers propose.
Locked inside a human brain protein, the hallucinogenic drug LSD takes an extra-long trip.
New X-ray crystallography images reveal how an LSD molecule gets trapped within a protein that senses serotonin, a key chemical messenger in the brain. The protein, called a serotonin receptor, belongs to a family of proteins involved in everything from perception to mood.
The work is the first to decipher the structure of such a receptor bound to LSD, which gets snared in the protein for hours. That could explain why “acid trips” last so long, study coauthor Bryan Roth and colleagues report January 26 in Cell. It’s “the first snapshot of LSD in action,” he says. “Until now, we had no idea how it worked at the molecular level.” But the results might not be that relevant to people, warns Cornell University biophysicist Harel Weinstein.
Roth’s group didn’t capture the main target of LSD, a serotonin receptor called 5-HT2A, instead imaging the related receptor 5-HT2B. That receptor is “important in rodents, but not that important in humans,” Weinstein says.
Roth’s team has devoted decades to working on 5-HT2A, but the receptor has “thus far been impossible to crystallize,” he says. Predictions of 5-HT2A’s structure, though, are very similar to that of 5-HT2B, he says.
LSD, or lysergic acid diethylamide, was first cooked up in a chemist’s lab in 1938. It was popular (and legal) for recreational use in the early 1960s, but the United States later banned the drug (also known as blotter, boomer, Purple Haze and electric Kool-Aid).
It’s known for altering perception and mood — and for its unusually long-lasting effects. An acid trip can run some 15 hours, and at high doses, effects can linger for days. “It’s an extraordinarily potent drug,” says Roth, a psychiatrist and pharmacologist at the University of North Carolina School of Medicine in Chapel Hill. Scientists have known for decades that LSD targeted serotonin receptors in the brain. These proteins, which are also found in the intestine and elsewhere in the body, lodge within the outer membranes of nerve cells and relay chemical signals to the cells’ interiors. But no one knew exactly how LSD fit into the receptor, or why the drug was so powerful.
Roth and colleagues’ work shows the drug hunkered deep inside a pocket of the receptor, grabbing onto an amino acid that acts like a handle to pull down a lid. It’s like a person holding the door of a storm cellar closed during a tornado, Roth says.
When the team did additional molecular experiments, tweaking the lid’s handle so that LSD could no longer hang on, the drug slipped out of the pocket faster than when the handle was intact. That was true whether the team used receptor 5-HT2B or 5-HT2A, Roth says. (Though the researchers couldn’t crystallize 5-HT2A, they were able to grow the protein inside cells in the lab for use in their other experiments.) The results suggest that LSD’s grip on the receptor is what keeps it trapped inside. “That explains to a great extent why LSD is so potent and why it’s so long-lasting,” Roth says.
David Nutt, a neuropsychopharmacologist at Imperial College London, agrees. He calls the work an “elegant use of molecular science.”
Weinstein remains skeptical. The 5-HT2A receptor is the interesting one, he maintains. A structure of that protein “has been needed for a very long time.” That’s what would really help explain the hallucinogenic effects of LSD, he says.
The sound of someone slurping coffee or crunching an apple can be mildly annoying — but it leaves some people seething. These people aren’t imagining their distress, new research suggests. Anger and anxiety in response to everyday sounds of eating, drinking and breathing come from increased activity in parts of the brain that process and regulate emotions, scientists report February 2 in Current Biology.
People with this condition, called misophonia, are often dismissed as just overly sensitive, says Jennifer Jo Brout, a clinical psychologist not involved with the study. “This really confirms that it’s neurologically based,” says Brout, founder of the Sensory Processing and Emotion Regulation Program at Duke University Medical Center. Researchers played sounds to 20 people with misophonia and 22 people without. Some sounds were neutral, such as rain falling. Others, like a wailing baby, were annoying to both groups of people but didn’t cause a misophonic response. A third set were sounds known to cause distress in people with misophonia — chewing and breathing noises.
MRI brain scans showed that both groups of people reacted similarly to the neutral and annoying sounds. But misophonics responded far more dramatically to the chewing and breathing. They showed more activity in their anterior insular cortex, a brain structure involved in emotional processing. Scientists found structural differences, too — more connections from the anterior insular cortex to structures like the amygdala and the hippocampus, which also help with processing emotions. People with misophonia also showed increased heart rate and skin conductivity. That’s the same sort of flight-or-fight response that gets triggered when facing a wild animal or a public speaking engagement. Sounds most people ignore in their day-to-day listening create a very strong emotional response in misophonics, says study coauthor Sukhbinder Kumar, a cognitive neuroscientist at Newcastle University in Newcastle upon Tyne, England. Their brains are ascribing extra importance to certain sounds. But it’s still unclear why only specific sounds cause a reaction.
The topic of time is both excruciatingly complicated and slippery. The combination makes it easy to get bogged down. But instead of an exhaustive review, journalist Alan Burdick lets curiosity be his guide in Why Time Flies, an approach that leads to a light yet supremely satisfying story about time as it runs through — and is perceived by — the human body.
Burdick doesn’t restrict himself to any one aspect of his question. He spends time excavating what he calls the “existential caverns,” where philosophical questions, such as the shifting concept of now, dwell. He describes the circadian clocks that keep bodies running efficiently, making sure our bodies are primed to digest food at mealtimes, for instance. He even covers the intriguing and slightly insane self-experimentation by the French scientist Michel Siffre, who crawled into caves in 1962 and 1972 to see how his body responded in places without any time cues. In the service of his exploration, Burdick lived in constant daylight in the Alaskan Arctic for two summery weeks, visited the master timekeepers at the International Bureau of Weights and Measures in Paris to see how they precisely mete out the seconds and plunged off a giant platform to see if time felt slower during moments of stress. The book not only deals with fascinating temporal science but also how time is largely a social construct. “Time is what everybody agrees the time is,” one researcher told Burdick. That subjective truth also applies to the brain. Time, in a sense, is created by the mind. “Our experience of time is not a cave shadow to some true and absolute thing; time is our perception,” Burdick writes. That subjective experience becomes obvious when Burdick recounts how easily our brains’ clocks can be swayed. Emotions, attention (SN: 12/10/16, p. 10) and even fever can distort our time perception, scientists have found.
Burdick delves deep into several neuroscientific theories of how time runs through the brain (SN: 7/25/15, p. 20). Here, the story narrows somewhat in an effort to thoroughly explain a few key ideas. But even amid these details, Burdick doesn’t lose the overarching truth — that for the most part, scientists simply don’t know the answers. That may be because there is no one answer; instead, the brain may create time by stitching together a multitude of neural clocks. After reading Why Time Flies, readers will be convinced that no matter how much time passes, the mystery of time will endure.
Integrated circuits made of germanium instead of silicon have been reported … by researchers at International Business Machines Corp. Even though the experimental devices are about three times as large as the smallest silicon circuits, they reportedly offer faster overall switching speed. Germanium … has inherently greater mobility than silicon, which means that electrons move through it faster when a current is applied. — Science News, February 25, 1967
UPDATE: Silicon circuits still dominate computing. But demand for smaller, high-speed electronics is pushing silicon to its physical limits, sending engineers back for a fresh look at germanium. Researchers built the first compact, high-performance germanium circuit in 2014, and scientists continue to fiddle with its physical properties to make smaller, faster circuits. Although not yet widely used, germanium circuits and those made from other materials, such as carbon nanotubes, could help engineers make more energy-efficient electronics.
WASHINGTON — It has been used by an assassin wielding a poisoned umbrella and sent in a suspicious letter to a president.
Ricin, the potent toxin and bioterrorism agent, has no antidote and can cause death within days. But a cocktail of antibodies could one day offer victims at least a slim window for treatment.
A new study presented February 7 at the American Society for Microbiology’s Biothreats meeting reveals a ricin antidote that, in mice, works even days after exposure to the toxin. Another presented study offers a potential explanation for how such an antidote might work. Doctors need some way to deal with ricin poisoning, said Patrick Cherubin, a cell biologist at the University of Central Florida in Orlando. Immunologist Nicholas Mantis agreed: “There is no specific treatment or therapy whatsoever.”
Though ricin has an innocuous origin (it’s found in castor beans), the poison is anything but harmless. It’s dangerous and relatively easy to spread — rated by the U.S. Centers for Disease Control and Prevention as a category B bioterrorism agent, just behind the highest-risk category A agents such as anthrax, plague and Ebola.
Ricin poisoning is rare but has featured in some high-profile cases. In 1978, Bulgarian writer Georgi Markov was hit in the thigh with a ricin-poisoned pellet shot from an umbrella gun. A few days later, he was dead. In 2013, a letter addressed to President Barack Obama tested positive for granules of the deadly toxin. A Texas woman had ordered castor bean seeds and lye online, for a do-it-yourself approach to making ricin. No one was injured.
Symptoms of ricin poisoning depend on how the toxin enters the body, and how much gets in. Inhaling ricin can make breathing so difficult the skin turns blue. Ingesting ricin can cause diarrhea, vomiting and seizures. Death can come as soon as 36 hours after exposure.
Ricin is known as an RIP — a scary-sounding acronym that stands for ribosome-inactivating protein, said Mantis, of the New York State Department of Health in Albany. In the cell, ribosomes serve as tiny protein factories. After ricin exposure, “the whole machinery comes to a screeching halt,” Mantis said. For cells, shutting down protein factories for too long is a death sentence. Scientists have developed two vaccines for ricin, though neither is available yet for use in humans. A vaccine may be “good for soldiers going into the field,” said biochemist Ohad Mazor of the Israel Institute for Biological Research in Ness Ziona. But unvaccinated people are out of luck. Mazor and colleagues developed a new treatment that could potentially help. The treatment is a mixture of three proteins called neutralizing antibodies; they grab onto ricin and don’t easily let go. With antibodies hanging onto its back, ricin has trouble slipping into cells and wreaking its usual havoc. Even 48 hours after inhaling ricin, roughly 73 percent of mice, 22 out of 30, treated with the antibodies survived, the team reported at the meeting and in a paper published in the March 1 Toxicon. Untreated mice died within a week.
Previous antibody treatments for ricin work well only if mice are treated within hours after exposure, Mazor said. For poisoned humans, that may not be long enough to diagnose the problem. Mazor doesn’t know how his antibodies might work in people, but he’d like to follow up his mouse work with studies in monkeys or pigs.
Scientists haven’t figured out exactly how antibodies help animals recover, but another study presented at the meeting offers a clue. Cherubin and colleagues added ricin to monkey cells in a dish, and then tracked how much protein was manufactured by the cells.
At high enough levels, ricin exposure shuttered the factories as expected. But when researchers stopped exposing cells to the toxin, protein synthesis started up again and cells recovered. “You need ongoing toxin delivery to eventually kill the cell,” Cherubin said. It’s possible that antibody treatments could cut off ricin delivery to cells, letting them bounce back from poisoning, said study coauthor Ken Teter, also a cell biologist at the University of Central Florida.
Helium — the recluse of the periodic table — is reluctant to react with other elements. But squeeze the element hard enough, and it will form a chemical compound with sodium, scientists report.
Helium, a noble gas, is one of the periodic table’s least reactive elements. Originally, the noble gases were believed incapable of forming any chemical compounds at all. But after scientists created xenon compounds in the early 1960s, a slew of other noble gas compounds followed. Helium, however, has largely been a holdout. Although helium was known to hook up with certain elements, the bonds in those compounds were weak, or the compounds were short-lived or electrically charged. But the new compound, called sodium helide or Na2He, is stable at high pressure, and its bonds are strong, an international team of scientists reports February 6 in Nature Chemistry.
As a robust helium compound, “this is really the first that people ever observed,” says chemist Maosheng Miao of California State University, Northridge, who was not involved with the research.
The material’s properties are still poorly understood, but it is unlikely to have immediate practical applications — scientists can create it only in tiny amounts at very high pressures, says study coauthor Alexander Goncharov, a physicist at the Carnegie Institution for Science in Washington, D.C. Instead, the oddball compound serves as inspiration for scientists who hope to produce weird new materials at lower pressures. “I would say that it’s not totally impossible,” says Goncharov. Scientists may be able to tweak the compound, for example, by adding or switching out elements, to decrease the pressure needed.
To coerce helium to link up with another element, the scientists, led by Artem Oganov of Stony Brook University in New York, first performed computer calculations to see which compounds might be possible. Sodium, calculations predicted, would form a compound with helium if crushed under enormously high pressure. Under such conditions, the typical rules of chemistry change — elements that refuse to react at atmospheric pressure can sometimes become bosom buddies when given a squeeze.
So Goncharov and colleagues pinched small amounts of helium and sodium between a pair of diamonds, reaching pressures more than a million times that of Earth’s atmosphere, and heated the material with lasers to temperatures above 1,500 kelvins (about 1200° Celsius). By scattering X-rays off the compound, the scientists could deduce its structure, which matched the one predicted by calculations. “I think this is really the triumph of computation,” says Miao. In the search for new compounds, computers now allow scientists to skip expensive trial-and-error experiments and zero in on the best candidates to create in a laboratory.
Na2He is an unusual type of compound known as an electride, in which pairs of electrons are cloistered off, away from any atoms. But despite the compound’s bizarre nature, it behaves somewhat like a commonplace compound such as table salt, in which negatively charged chloride ions alternate with positively charged sodium. In Na2He, the isolated electron pairs act like negative ions in such a compound, and the eight sodium atoms surrounding each helium atom are the positive ions.
“The idea that you can make compounds with things like helium which don’t react at all, I think it’s pretty interesting,” says physicist Eugene Gregoryanz of the University of Edinburgh. But, he adds, “I would like to see more experiments” to confirm the result.
The scientists’ calculations also predicted that a compound of helium, sodium and oxygen, called Na2HeO, should form at even lower pressures, though that one has yet to be created in the lab. So the oddball new helium compound may soon have a confirmed cousin.
