The fundamental research sheds light on the biomechanics of the unique hunting behavior (known as mousing), advances our understanding of animal adaptations and offers insights into snow injuries people experience during snowboarding or skiing.

The study published April 29 in the Proceedings of the National Academy of Sciences.

While there have been many studies of water birds and animals such as porpoises and dolphins diving from air into water, interactions between animals and the air-snow interface have not been well-researched. Snow has fluid-like properties when light and fluffy, and solid-like properties when compacted, such as when people make snowballs.

“The fox’s sharp snout doesn’t significantly compress the snow, it penetrates it without much resistance,” said Sunghwan Jung, the paper’s corresponding author and professor of biological and environmental engineering. Jisoo Yuk, a doctoral student in Jung’s lab, is the paper’s first author.

In the study, the authors scanned skulls of red and arctic foxes (from the Canidae family) and lynx and puma skulls (from the Felidae family) at the American Museum of Natural History in Manhattan. They 3D-printed the skulls and attached each to a sensor that measured impact force. The skulls were then dropped into both snow and water, and the researchers entered data into computer models to compare impacts of both.

Jung and colleagues found that the foxes’ sharp snouts penetrated the snow with little resistance, minimizing potential tissue damage during a headfirst dive. “Without much compression, in spite of the high-speed impact, the snow behaves like water,” Jung said. But the flat Felidae snouts compressed the snow upon impact, creating a large and potentially damaging resistance.

When mousing in snow, the fox’s long snout also allows it to reach its prey earlier, as mice are very sensitive to movements in their environment and can quickly escape. Other behavioral studies have shown that prior to pouncing, foxes shake their heads to listen to the rustling sounds of mice or other animals beneath the snow’s surface, thereby gauging the depth of the sound source.

“This is a very dangerous process, but we haven’t had reports of foxes getting injured,” Jung said.

The study was funded by the National Science Foundation.

“For the first time, the new enzyme cocktails not only remove the well-described A and B antigens, but also extended variants previously not recognized as problematic for transfusion safety. We are close to being able to produce universal blood from group B donors, while there is still work to be done to convert the more complex group A blood. Our focus is now to investigate in detail if there are additional obstacles and how we can improve our enzymes to reach the ultimate goal of universal blood production,” says Professor Maher Abou Hachem, who is the study leader at DTU and one of the senior scientists behind the discovery.

He states that the discovery is the result of combining the expertise of DTU researchers in enzymes from the human gut microbiota and Lund University researchers in carbohydrate-based blood groups and transfusion medicine.

High demand for donor blood

Human red blood cells carry specific complex sugars structures (antigens) that define the four ABO blood groups A, B, AB and O. These antigens control compatibility between donors and recipients for safe blood transfusion and organ transplantation. Donor blood is screened for disease markers and the main blood groups. It can then be stored refrigerated for up to 42 days.

The need for donor blood is high due to the elderly making up a larger proportion of the population and more patients undergoing blood-intensive medical procedures. Successfully converting A or B blood types into ABO universal donor blood can markedly reduce the logistics and costs currently associated with storing four different blood types. In addition, the development of universal donor blood will lead to an increased supply of donor blood by reducing the waste of blood approaching its expiry date.

The reason why it is necessary to remove the A and B antigens to create universal donor blood is because they can trigger life-threatening immune reactions when transfused into non-matched recipients.

The concept of using enzymes to generate universal donor blood was introduced more than 40 years ago. Since then, higher efficiency enzymes to remove the A and B antigens were discovered, but researchers are still not able to explain or abolish all immune reactions related to the blood, and therefore these enzymes are still not used in clinical practice.

Enzymes from the gut

The research groups from DTU and Lund University have gone new ways to find enzymes that can remove both the A and B blood antigens and the sugars that block them. The research teams discovered new mixtures of enzymes from the human gut bacterium Akkermansia muciniphila that feeds by breaking down the mucus, which covers the surface of the gut. It turns out that these enzymes are exceptionally efficient, as the complex sugars at the surface of the intestinal mucosa share chemical resemblance with those found at the surface of blood cells.

“What is special about the mucosa is that bacteria, which are able to live on this material, often have tailor-made enzymes to break down mucosal sugar structures, which include blood group ABO antigens. This hypothesis turned out to be correct,” says Maher Abou Hachem.

The researchers in this study tested 24 enzymes, which they used to process hundreds of blood samples.

“Universal blood will create a more efficient utilization of donor blood, and also avoid giving ABO-mismatched transfusions by mistake, which can otherwise lead to potentially fatal consequences in the recipient. When we can create ABO-universal donor blood, we will simplify the logistics of transporting and administering safe blood products, while at the same time minimizing blood waste” says Professor Martin L. Olsson, the leader of the study at Lund University.

The researchers from DTU and Lund University have applied for a patent on the new enzymes and the method for enzyme treatment and expect to make further progress on this in their new joint project over the next three and a half years. If successful, the concept needs to be tested in controlled patient trials before this can be considered for commercial production and clinical use.

The initial research project is funded by the Independent Research Fund Denmark (Technology and Production Sciences, FTP), the Swedish Research Council, ALF grants from the Swedish government and county councils as well as the Knut and Alice Wallenberg Foundation and Research Fund Denmark, Natural Sciences, FNU), while the new continued project is funded by the Novo Nordisk Foundation, Interdisciplinary Synergy Programme.

FACTS:

Donorblood

In Scandinavia, the four main blood types are distributed with approximately 40-45 percent blood type A, the majority of whom are so-called RhD positive and 10-15 percent RhD negative, followed by blood type O with about 40 percent, B with about 10 percent and AB with about 5 percent. Red blood cells from blood group O are the only type that can be used by all receiving patients regardless of ABO type.

Bacterium from the gut

Akkermansia muciniphila is a bacterium found abundantly in the guts of most healthy humans. This bacterium can break down mucus in the gut and produces beneficial compounds such as the short-chain fatty acid propionate, in addition to exerting beneficial effects on body weight and metabolic markers.

It is estimated that up to 85% of stars exist in binary star systems, some even in systems with three or more stars. These stellar pairs are born together out of the same molecular cloud from a shared abundance of chemical building blocks, so astronomers would expect to find that they have nearly identical compositions and planetary systems. However, for many binaries that isn’t the case. While some proposed explanations attribute these dissimilarities to events occurring after the stars evolved, a team of astronomers have confirmed for the first time that they can actually originate from before the stars even began to form.

Led by Carlos Saffe of the Institute of Astronomical, Earth and Space Sciences (ICATE-CONICET) in Argentina, the team used the Gemini South telescope in Chile, one half of the International Gemini Observatory, supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab. With the new, precise Gemini High Resolution Optical SpecTrograph (GHOST) the team studied the different wavelengths of light, or spectra, given off by a pair of giant stars, which revealed significant differences in their chemical make-up. “GHOST’s extremely high-quality spectra offered unprecedented resolution,” said Saffe, “allowing us to measure the stars’ stellar parameters and chemical abundances with the highest possible precision.” These measurements revealed that one star had higher abundances of heavy elements than the other. To disentangle the origin of this discrepancy, the team used a unique approach.

Previous studies have proposed three possible explanations for observed chemical differences between binary stars. Two of them involve processes that would occur well into the stars’ evolution: atomic diffusion, or the settling of chemical elements into gradient layers depending on each star’s temperature and surface gravity; and the engulfment of a small, rocky planet, which would introduce chemical variations in a star’s composition.

The third possible explanation looks back at the beginning of the stars’ formation, suggesting that the differences originate from primordial, or pre-existing, areas of nonuniformity within the molecular cloud. In simpler terms, if the molecular cloud has an uneven distribution of chemical elements, then stars born within that cloud will have different compositions depending on which elements were available at the location where each formed.

So far, studies have concluded that all three explanations are probable; however, these studies focused solely on main-sequence binaries. The ‘main-sequence’ is the stage where a star spends most of its existence, and the majority of stars in the Universe are main-sequence stars, including our Sun. Instead, Saffe and his team observed a binary consisting of two giant stars. These stars possess extremely deep and strongly turbulent external layers, or convective zones. Owing to the properties of these thick convective zones, the team was able to rule out two of the three possible explanations.

The continuous swirling of fluid within the convective zone would make it difficult for material to settle into layers, meaning giant stars are less sensitive to the effects of atomic diffusion — ruling out the first explanation. The thick external layer also means that a planetary engulfment would not change a star’s composition much since the ingested material would rapidly be diluted — ruling out the second explanation. This leaves primordial inhomogeneities within the molecular cloud as the confirmed explanation. “This is the first time astronomers have been able to confirm that differences between binary stars begin at the earliest stages of their formation,” said Saffe.

“Using the precision-measurement capabilities provided by the GHOST instrument, Gemini South is now collecting observations of stars at the end of their lives to reveal the environment in which they were born,” says Martin Still, NSF program director for the International Gemini Observatory. “This gives us the ability to explore how the conditions in which stars form can influence their entire existence over millions or billions of years.”

Three consequences of this study are of particular significance. First, these results offer an explanation for why astronomers see binary stars with such different planetary systems. “Different planetary systems could mean very different planets — rocky, Earth-like, ice giants, gas giants — that orbit their host stars at different distances and where the potential to support life might be very different,” said Saffe.

Second, these results pose a crucial challenge to the concept of chemical tagging — using chemical composition to identify stars that came from the same environment or stellar nursery — by showing that stars with different chemical compositions can still have the same origin.

Finally, observed differences previously attributed to planetary impacts on a star’s surface will need to be reviewed, as they might now be seen as having been there from the very beginning of the star’s life.

“By showing for the first time that primordial differences really are present and responsible for differences between twin stars, we show that star and planet formation could be more complex than initially thought,” said Saffe. “The Universe loves diversity!”