Research Highlights

Our pick of the latest scientific literature

Palaeontology

Ancient bird gland gives up its chemical secrets

Molecules used to preen feathers identified in 48-million-year-old fossil.

Organic molecules extracted from a 48-million-year-old fossilized bird are the remains of lipids produced by a gland involved in feather maintenance.

Previous studies have suggested that structures found in fossilized birds from Germany’s Messel Pit fossil site are preserved uropygial glands, which secrete oil for preening the feathers.

Shane O’Reilly at the Massachusetts Institute of Technology in Cambridge and his colleagues analysed one bird fossil using mass spectroscopy, and identified a range of alkenes, alkanes and complex lipid molecules in the purported gland. Comparisons with uropygial secretions from modern birds suggest that the preserved molecules are the chemically altered remains of wax esters used to maintain feathers. This shows that even lipid-rich soft tissues can be preserved over geological time scales, the authors say.

 

Medical research

Stretchy implants for growing bodies

Technology could one day reduce operations on children.

Implants that can stretch as a child grows could reduce the need for repeated operations.

Pedro del Nido and Jeffrey Karp at Harvard Medical School in Boston, Massachusetts, and their colleagues designed a surgical implant that adapts to growing tissues. They placed a biodegradable polymer core inside a braided sleeve, which is designed to stretch and thin out as the core degrades.

The group tested the device on the side of the left shin bone of three young rats and found that it guided normal growth. By contrast, fixed-size implants in three other rats restricted shin growth. The team also found that the device could support normal growth of heart valves in piglets, in a procedure mimicking surgery to repair leaking valves. Tweaking the braid design and the speed of the core’s degradation tunes the rate of elongation, the researchers say, and could lead to devices that minimize the need for repeated, risky surgery on growing children.

Climate sciences

Volcanoes stirred conflict in ancient Egypt

Disruption of Nile flooding, plus social stress, has been linked to revolts in the Ptolemaic dynasty.

Volcanic eruptions may have triggered conflict in ancient Egypt, by disrupting annual flooding of the Nile.

Egyptians in the time of the Ptolemaic dynasty, which ruled from 305 to 30 bc, depended heavily on summer flooding for crop production.

Francis Ludlow of Trinity College Dublin, and his colleagues analysed ice-core data, which preserves evidence of ancient volcanic eruptions, as well as historic measurements of the Nile from the Nilometer building in Cairo and written records of the time. These data, and modelling based on climatic impacts of modern volcanism, suggest that ancient eruptions disrupted the annual Nile flood. This in turn both helped to trigger revolts against the empire and forced it to halt wars in which it was engaged, say the authors. They caution that other social factors were also important in these events, including high levels of taxation and ethnic tensions.

Physics

A new way to measure electron charge asymmetry

Watching particles wobble helps pin down shape of their electric field.

The electron is believed to be a pointlike particle. According to the standard model of particle physics, there should be virtually no asymmetry in an electron’s electric field — that is, its electric dipole moment should be close to zero. But some theories predict a larger charge imbalance, and hence a larger dipole moment.

By placing molecules in an electric field and seeing whether the electrons within them ‘wobble’ on their axes, like spinning tops, physicists hope to determine whether a non-zero dipole moment exists. Although they have not yet proved that it does, they have managed to place an upper bound on its size. The most precise limit so far has been determined using beams of neutral molecules.

Now, William Cairncross at the University of Colorado, Boulder, and his collaborators have introduced a second technique, based on trapping molecular ions. Their first results, using ionic hafnium fluoride, came within a factor of two of the best previous estimates and give an electric dipole moment of less than 1.3 × 10−28 e cm, meaning, in effect, that they found no dipole moment.

The loss of large herbivores, such as elephants, from modern ecosystems could mean the loss of a vital ecosystem service.

The loss of large herbivores, such as elephants, from modern ecosystems could mean the loss of a vital ecosystem service. Mike Fisher/EyeEm/Getty

Ecology

Rise of plant-eating dinosaurs spread nutrients across the globe

Coal deposits show the importance of large animals’ faeces.

The rise of huge herbivores around 300 million years ago significantly increased the availability of nutrients globally as the animals defecated waste far from where they ate.

Previous models have predicted this phenomenon, but empirical evidence has been lacking. Christopher Doughty of Northern Arizona University in Flagstaff looked at data on coal deposits from 323 to 299 million years ago, a period before large herbivores walked the planet. He compared these to coal from the Cretaceous period 145 to 66 million years ago, when the largest herbivores ever — the sauropods — roamed Earth.

Concentrations of nutrients vital to plants and animals were on average 136% higher in coal produced by vegetation from the Cretaceous than in coal laid down before the big herbivores appeared. These nutrients were also more widely distributed. But there was no significant difference between the two data sets in the distribution of aluminium, which is shifted around through the weathering of rocks over time and not by animals. 

This finding indicates that ongoing reductions in the populations of large herbivores, such as forest elephants, could also impoverish ecosystems.

Cancer

Cancer cells recycle ammonia waste to grow

Tumours dodge toxic effects by turning the by-product into amino acids.

Breast cancer cells can reuse their ammonia waste to grow, research suggests.

Toxic ammonia by-products from healthy cells are generally removed from the body as urea, through the liver. But many tumours lack the blood vessels needed to tap into the excretory system, so ammonia builds up in the surrounding area.

Now Marcia Haigis at Harvard Medical School in Boston, Massachusetts, and her colleagues report that ammonia accumulates around tumours and is used by their cells to synthesize amino acids. Breast cancer cells can efficiently metabolize up to 57% of nearby ammonia into useful glutamate, which is then used to build amino acids such as proline and aspartate, they found.

This recycling means that breast cancer cells avoid the toxic effects of ammonia by converting the compound into usable nitrogen, a necessary agent for rapid growth.

The New Zealand sea lion (Phocarctos hookeri) is an endangered species and is in decline. Tobias Bernhard/Getty

Conservation biology

Covering up the by-catch problem

‘Exclusion devices’ seem to mask the impact of trawling on marine mammals.

Devices designed to release endangered New Zealand sea lions when they are caught by fishing boats may be concealing the negative effects of trawling. 

Many fishing boats are equipped with such devices, which release unintentionally caught animals. Stefan Meyer at the University of Otago in Dunedin, New Zealand, and his colleagues looked at the frequency of contact between sea lions (Phocarctos hookeri) and squid trawl nets in waters around the Auckland Islands, and at the number of pups produced, between 1995 and 2015. 

Although the number of sea lions recorded as caught declined after 2001, when exclusion devices were installed, the birthrate of these animals did not increase. Modelling suggests that 35% of the annual variation in pup production was due to encounters between sea lions and fishing vessels. The team suggests that sea lions released by exclusion devices probably die shortly afterwards, or fail to reproduce, owing to injuries caused by the devices.

Chemistry

Rare drug made in major amounts

Total synthesis of complicated natural molecule could overcome supply problem.

A scarce but potent natural product that has shown promise as a medicine has been synthesized in the lab.

Bryostatin 1 is a candidate drug for treating HIV/AIDS, Alzheimer’s disease and cancer. But it is notoriously difficult to harvest from the wild. The US National Cancer Institute had an initial stock of only 18 grams, which was extracted from 13 metric tonnes of a marine organism called Bugula neritina.

Paul Wender at Stanford University in California and his colleagues used convergent synthesis to produce different sections of the complicated multi-ringed structure separately, which they then assembled to create more than 2 grams of the desired molecule. The longest production sequence for a single section consisted of 19 separate reactions, as part of an overall recipe of 29 steps in total. The average yield was more than 80% per step, for an overall yield of 4.8%. The authors note that the only previously reported synthesis of bryostatin 1 had 57 steps. 

Immunology

Immune cells go home to die

Neutrophil white blood cells can end up back in the bone marrow once their job is done.

Neutrophils are white blood cells produced in the bone marrow that can fight infection and inflammation by ingesting harmful microorganisms. But some evidence has suggested that if neutrophils do not die in a wound, they might leave and cause inflammation elsewhere in the body. 

Now researchers have found that the cells sometimes return to the bone marrow and self-destruct.

Paul Kubes at the University of Calgary in Canada and his colleagues used fluorescence imaging to track the activity of these cells in mice with damage to the liver. They watched as neutrophils infiltrated wounds and cleaned up DNA fragments, as expected. But 24 hours later, many of the cells had returned to the bone marrow and initiated their own deaths. This round trip could be essential for the resolution of inflammation, the authors say.

How the Sun’s corona can be millions of degrees hotter than its surface has been a mystery.

How the Sun’s corona can be millions of degrees hotter than its surface has been a mystery. NASA/SDO

Astronomy and astrophysics

Tiny, fleeting flares might heat Sun’s corona

Short-lived ‘nanoflares’ could explain why the Sun’s outer atmosphere can be several million degrees hotter than its surface.

Fleeting ‘nanoflares’ that are too small to see directly could explain why the Sun’s outer atmosphere, or corona, can be millions of degrees hotter than its surface. 

Giant eruptions of ionized gas occasionally release energy into the Sun’s outer layers, but this happens too rarely to explain the zone’s usual temperature of 1 million to 3 million kelvin.

Shin-nosuke Ishikawa at the Japan Aerospace Exploration Agency in Kanagawa and his colleagues looked for another potential source of heat: a plethora of small, short-lived explosions. The team compared X-ray observations of a region of the Sun made using a research rocket with data on the same area collected by the US Geostationary Operational Environmental Satellite. Although no distinct flares were indicated by the satellite data, the X-ray maps showed a faint emission, suggestive of a small amount of plasma at an extraordinary 10 million kelvin. The presence of nanoflares could explain this finding, say the authors. They add that the results will constrain models of how these flares could be distributed.

The huge South Pole-Aitken basin on the Moon was created by a massive impact around 4 billion years ago.

The huge South Pole-Aitken basin on the Moon was created by a massive impact around 4 billion years ago. NASA/GSFC/DLR/Arizona State Univ./Lunar Reconnaissance Orbiter

Planetary science

Moon mantle’s make-up revealed

Huge asteroid impact on far side ejected rocks from deep under the crust.

The surprising composition of the Moon’s upper mantle — the layer below the crust — is revealed by ancient asteroid-impact debris.

Planetary scientists have long searched for olivine on the Moon, because this mineral is commonly found in Earth’s upper mantle. They thought that huge asteroid impacts would have punched through to the lunar mantle, leaving olivine scattered around the surface.

Jay Melosh at Purdue University in West Lafayette, Indiana, and his colleagues used computer simulations to show that one such impact — which created the 2,500-kilometre-wide South Pole-Aitken basin — blasted into the Moon to a depth of at least 100 kilometres. Debris from this farside impact would have scattered across the surrounding highlands, the simulations show.

But that area is covered by a different mineral: low-calcium pyroxene. So the Moon’s mantle must be mostly made of low-calcium pyroxene, the team argues — not olivine, as long thought.

Ice formed six-leaved-clover patterns on hydrophobic surfaces, and sunflower-like arrangements on hydrophilic ones.

Ice formed six-leaved-clover patterns on hydrophobic surfaces, and sunflower-like arrangements on hydrophilic ones. J. Liu et al./PNAS

Physics

Watching how surface properties affect ice growth

Water-repellent surfaces trigger formation of crystals shaped like six-leaved-clover.

Ice crystals grow on solid surfaces in two distinctly different ways, depending on the degree to which the surface attracts or repels water. Jianjun Wang at the Chinese Academy of Sciences in Beijing and his colleagues triggered ice formation using silver iodide nanoparticles, and watched as crystals formed on hydrophilic and hydrophobic surfaces.

When ice formed on the former, it grew along the surface, producing sunflower-like patterns (bottom). On the latter, it minimized its contact with the substrate by growing away from the surface at an angle, and forming six-leaved-clover shapes (top). 

Although the influence of factors such as temperature and humidity on ice formation has been well studied, the influence of surface properties is less well understood. The new findings could inform the design of surfaces that need to repel ice, such as windscreens.

This ceramic gear is part of a pump that can move molten tin at temperatures of 1,400 °C.

This ceramic gear is part of a pump that can move molten tin at temperatures of 1,400 °C. Christopher Moore/Georgia Tech

Materials science

Ceramic pump is hot-tin proof 

Machine withstands molten metal at more than 1,000 °C.

A ceramic pump can transport liquid tin heated to 1,400 °C, the highest temperature any liquid has been pumped at so far.

Molten metals offer an attractive option for transporting thermal energy, but finding materials that can contain them at extreme temperatures is tricky.

Asegun Henry at the Georgia Institute of Technology in Atlanta and his team made a mechanical pump entirely from ceramics including Shapal — a mixture of aluminium and boron nitrides. Ceramics had been considered too brittle for such use, but the team was able to pump liquid tin through the machine for three days at temperatures averaging 1,200 °C. The carefully engineered ceramics held fast under mechanical pressures and did not react with the flowing metal, even when temperatures peaked at 1,400 °C. 

Ceramic pumps could be used to store and redistribute heat energy that is a waste product of many industrial activities, the authors say.

This artist’s impression shows the ring system of Haumea that was discovered earlier this year.

This artist’s impression shows the ring system of Haumea that was discovered earlier this year. IAA-CSIC/UHU

Astronomy and astrophysics

A ring far beyond Pluto

Dwarf planet Haumea joins select list of Solar System bodies with rings.

The dwarf planet Haumea, which orbits 1.9 billion kilometres beyond Neptune, has a ring — the first object beyond the orbit of Neptune known to have such a feature.

A team led by Jose Ortiz from the Institute of Astrophysics of Andalusia in Spain combined observations taken by multiple telescopes of changes in light intensity as Haumea passed in front of a star. Dips in the light just before and after the main bulk of Haumea obscured the distant star indicated the presence of a dense, narrow ring encircling the planet’s equator. The team estimate the ring’s radius at 2,287 kilometres and width at 70 kilometres. Only two other minor planets have been observed with rings: Chariklo and Chiron, which orbit the Sun between Jupiter and Neptune.

The observations also enabled the team to calculate that Haumea is about one-third as dense as Earth and shaped like a rugby ball.

Climate sciences

Dry summers ahead for US–Mexico border region

Higher abundance of carbon dioxide in the atmosphere means less rainfall for northwest Mexico.

Summer in northwestern Mexico and the southwestern United States is expected to become palpably drier as a result of rising atmospheric carbon dioxide levels.

Abundant summer rain over parts of this region is crucial for replenishing the limited local water supply. But scientists have been uncertain how climate change might affect the seasonal monsoon rainfall, owing to the coarse resolution and inconsistency of models of atmospheric circulation. 

Using an improved climate model that accounts for small-scale atmospheric processes such as convection, Salvatore Pascale of Princeton University in New Jersey and his colleagues found that summer rainfall in the region would drop by up to 40% in response to doubling CO2 levels. The projected weakening of the North American monsoon, the authors suggest, is driven mainly by rising global sea surface temperatures, which tend to suppress rain-generating atmospheric convection. More climate-adaptation measures and better freshwater management will be needed across the region, the researchers say.

Diseases

Historical data chart malaria’s decline

Millions of blood samples provide comprehensive picture of disease in sub-Saharan Africa.

The largest-ever data set of malaria prevalence in sub-Saharan Africa reveals a long-term decline in the debilitating and often deadly disease.

Robert Snow at the Kenya Medical Research Institute in Nairobi and his colleagues gathered data from the past 115 years on the prevalence of malaria parasite Plasmodium falciparum. The data set includes the results of 7.8 million blood samples collected across almost 37,000 locations. The team found that the malaria infection rate has generally declined in sub-Saharan Africa, from 40% of those examined in 1900–29 to 24% in 2010–15.

There were two periods of rapid decline in infection, coinciding with the introduction of two major anti-malarial compounds between 1945 and 1949, and the widespread introduction between 2005 and 2009 of bed nets treated with insecticides and a new combination drug treatment.

Resurgence of the disease between 1985 and 2004 can be attributed to the spread of drug resistance, unusual weather events and a lack of investment in prevention. 

The team notes that large areas of West and Central Africa still experience high rates of malaria transmission, and warn against crediting the most recent decline in malaria prevalence to human intervention alone.

When the signals from blood vessels are dimmed, lymph vessels can be seen in primate brains on magnetic resonance imaging scans.

When the signals from blood vessels are dimmed, lymph vessels can be seen in primate brains on magnetic resonance imaging scans. M. Absinta et al./eLife (CC0 1.0)

Neuroscience

Scans light up the ‘drain pipes’ in human and monkey brains

Discovery follows previous finding of lymphatic systems in rodents.

Waste-removal ‘drain pipes’ have been observed in the brains of humans and non-human primates for the first time.

Lymphatic vessels in the brain were first hypothesized in 1816, but they were not seen until 2015, when researchers working in mice found them in the meninges — membranes that protect the brain.

Lymphatic vessels are hard to spot because they closely resemble blood vessels. Using a magnetic dye in combination with high-resolution magnetic resonance imaging (MRI), Daniel Reich of the US National Institutes of Health in Bethesda, Maryland, and his team were able to dim the signal from blood vessels while scanning the brain, thus revealing a network of lymph vessels in humans and marmoset monkeys.

Because it used MRI, the technique has immediate application for studying how these drainage vessels affect a variety of neurological disorders, the researchers say.

Genomics

Ancient encounters of the Neanderthal kind

New genomes from ancient hominids further entangle their respective family trees.

All humans whose ancestors lived outside Africa carry pieces of Neanderthal DNA. Two ancient-genome studies now suggest that human and Neanderthal populations may have mated more often than was previously thought.

A team led by Kay Prüfer and Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, generated a high-quality genome sequence from 50,000-year-old remains of a Neanderthal female found in Vindija Cave in Croatia. Her genome, like one previously sequenced from Neanderthal remains found in a Siberian cave, contain traces of gene flow from Homo sapiens. But the Neanderthals who left their mark on modern humans were more closely related to the Croatian individual than to her Siberian relative. 

Another team, led by Eske Willerslev at the Natural History Museum of Denmark in Copenhagen, sequenced 5 genomes from a 34,000-year-old Homo sapiens burial site in Russia. One individual carried more Neanderthal ancestry than do non-Africans today, possibly also reflecting additional mating episodes between humans and Neanderthals.

Despite claims of recent sightings in Tasmania, most researchers think the thylacine died out decades ago.

Despite claims of recent sightings in Tasmania, most researchers think the thylacine (Thylacinus cynocephalus) died out decades ago. Popperfoto/Getty

Zoology

Drought drove Tasmanian tiger from Australian mainland

Genomes of extinct marsupial predator reveal ancient family history.

The last known Tasmanian tiger, or thylacine, died in 1936 on the island for which it was named. But, by then, the animal had been extinct on the Australian mainland for more than 3,000 years.

Jeremy Austin and his colleagues at the University of Adelaide in Australia collected samples from thylacine (Thylacinus cynocephalus) museum specimens. They sequenced DNA contained in cell structures called mitochondria for 51 animals, including 15 from mainland Australia. Mapping of the relationships between animals suggests that there were two separate mainland populations — a larger, more genetically diverse population in the west and a smaller, less-diverse population in the east and Tasmania — that diverged about 30,000 years ago.

When Europeans settled on Tasmania in the 1800s, the thylacine population seems to have been expanding after long being kept small and genetically similar by centuries-long drought. This severe dry spell could have contributed to the species’ extinction on the mainland, where it was more severe.

New Content Item

Budgies come in two distinct colour combinations; now researchers think they have worked out why. Getty

Genetics

Pinpointing pigment genes for parrot pets

Enzyme identified that makes budgies yellow and green or blue and white.

Researchers have identified the genetic trait that controls whether the parrots widely known as budgerigars (Melopsittacus undulatus), or budgies, will be yellow and green or blue and white.

By sequencing DNA from 234 budgies, Carlos Bustamante at Stanford University in California and his colleagues determined that a pigment that gives yellow feathers their colour is linked to an enzyme called MuPKS. Yeast expressing the enzyme turned the same bright yellow as the parrot feathers. The researchers found that a single amino-acid substitution in MuPKS halted its activity, making feathers blue and white in some birds.

MuPKS does exist in the genomes of other bird species, but it is expressed at a rate hundreds to thousands of times higher in parrots. And that’s why, for example, we don’t see any crows or chickens in vibrant blues or yellows, the authors say.