Pig kidney xenotransplantation performing optimally after 32 days in human body

Surgeons at NYU Langone Health have transplanted a genetically engineered pig kidney that continues to function well after 32 days in a man declared dead by neurologic criteria and maintained with a beating heart on ventilator support. This represents the longest period that a gene-edited pig kidney has functioned in a human, and the latest step toward the advent of an alternate, sustainable supply of organs for transplant.

The procedure, performed on July 14, 2023, and led by Robert Montgomery, MD, DPhil, the H. Leon Pachter, MD Professor of Surgery, chair of the Department of Surgery, and director of the NYU Langone Transplant Institute, was the fifth xenotransplant performed at NYU Langone. Observation is ongoing and the study will continue through mid-September 2023.

"This work demonstrates a pig kidney -- with only one genetic modification and without experimental medications or devices -- can replace the function of a human kidney for at least 32 days without being rejected," said Dr. Montgomery, who had previously performed the world's first genetically modified pig kidney transplant into a human decedent on September 25, 2021, followed by a second similar procedure on November 22, 2021. Surgeons with the Transplant Institute performed two genetically engineered pig heart transplants in summer 2022.

Removing Troublesome Gene Again Shows Promise

The first hurdle to overcome in xenotransplants is preventing so-called hyperacute rejection, which typically occurs just minutes after an animal organ is connected to the human circulatory system. By "knocking out" the gene that encodes the biomolecule known as alpha-gal -- which has been identified as responsible for a rapid antibody-mediated rejection of pig organs by humans -- immediate rejection has been avoided in all five xenotransplants at NYU Langone. Additionally, the pig's thymus gland, which is responsible for educating the immune system, was embedded underneath the outer layer of the kidney to stave off novel, delayed immune responses. The combination of modifications has been shown to prevent rejection of the organ while preserving kidney function.

To ensure the body's kidney function was sustained solely by the pig kidney, both of the transplant recipient's native kidneys were surgically removed. One pig kidney was then transplanted and started producing urine immediately without any signs of hyperacute rejection. During the observation phase, intensive care clinical staff maintained the decedent on support while the pig kidney's performance was monitored and sampled with weekly biopsies. Levels of creatinine, a bodily waste product found in the blood and an indicator of kidney function, were in the optimal range during the length of the study, and there was no evidence on biopsy of rejection.

The surgery was the latest in a larger study approved by a specific research ethics oversight board at NYU Langone and was performed after consultation with the New York State Department of Health. This important research, which study leaders say could save many lives in the future, was made possible by the family of a 57-year-old male who elected to donate his body after a brain death declaration and a circumstance in which his organs or tissues were not suitable for transplant.

LiveOnNY, the nonprofit organization that facilitates organ and tissue donation in the greater New York City area, was a critical partner in the effort to inform, support, and collaborate throughout the authorization process with the donor family.

A Big Leap Toward a New Organ Source

In the United States, there are more than 103,000 people on the waiting list for transplant, with nearly 88,000 of those waiting for a kidney, according to recent federal Organ Procurement and Transplantation Network (OPTN) data. In 2022, about 26,000 people received a kidney transplant. Meanwhile, nearly 808,000 people in the U.S. have end-stage renal disease.

"There are simply not enough organs available for everyone who needs one," said Dr. Montgomery, who received a hepatitis C-positive heart transplant himself in 2018. "Too many people are dying because of the lack of available organs, and I strongly believe xenotransplantation is a viable way to change that."

The kidney and thymus gland used in this procedure were procured from a GalSafeTM pig, an animal engineered by Revivicor, Inc., a subsidiary of United Therapeutics Corporation. In December 2020, the U.S. Food and Drug Administration (FDA) approved the GalSafe pig as a potential source for human therapeutics as well as a food source for people with alpha-gal syndrome, a meat allergy caused by a tick bite.

Less May Be More in Kidney Xenotransplants

While previous genetically engineered pig organ transplants have incorporated up to 10 genetic modifications, this latest study shows that a single-gene knockout pig kidney can still perform optimally for at least 32 days without rejection.

"We've now gathered more evidence to show that, at least in kidneys, just eliminating the gene that triggers a hyperacute rejection may be enough along with clinically approved immunosuppressive drugs to successfully manage the transplant in a human for optimal performance -- potentially in the long-term," said Dr. Montgomery.

The NYU Langone team used standard transplant immunosuppression medications combined with enhanced screening of porcine cytomegalovirus (pCMV) in the donor pig to ensure safety. Recent studies have shown pCMV may affect organ performance and potentially trigger organ failure. No pCMV was detected after 32 days, and close surveillance of porcine endogenous retrovirus (PERV), along with six other viruses of interest, was performed.

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Heredity and environment account for people's love of nature

Humans have a positive view of nature. But is this due to an approach we have learned while growing up, or is it something we are born with? The answer is 'Both', according to researchers at the University of Gothenburg and the Swedish University of Agricultural Sciences. Our love of nature is highly individual and should influence how we plan our cities, say the researchers.

It is well known that nature has a positive effect on people. In cities in particular, studies have shown that trees and other greenery contribute to people's wellbeing. However, experts do not agree on the reasons behind this phenomenon, known as biophilia.

Some believe that it is natural for humans to feel an automatic positive attachment because human development has occurred in nature. Others argue that there is no evidence for this, and that influences during our childhood determine how we view nature.

A wide range of factors involved

Researchers from the University of Gothenburg and the Swedish University of Agricultural Sciences (SLU) have reviewed several studies within this field that examine both innate factors and what individuals experience during their lives, primarily as children. In a new scientific article, the researchers conclude that both heredity and environment influence an individual's attitude to nature, but that a wide range of factors also influence how love of nature is expressed.

"We have been able to establish that many people have an unconscious positive experience of nature," says Bengt Gunnarsson, Professor Emeritus of Environmental Science at the University of Gothenburg. "But the biophilia hypothesis should be modified to link the variation in individuals' relationships with nature to an interaction between heredity and environmental influence."

Nature mean different things

This is because people react differently to nature. In a Japanese study, subjects were asked to walk in a forest and in a city while their heartbeat was measured. This showed that positive emotions while walking in a forest increased in 65% of people. Thus, far from everyone had a positive perception of nature. Another environmental psychology study found that research subjects are unconsciously drawn to nature instead of cities, and that this attraction was reinforced in those whose childhood was rich in nature.

"An additional study on identical and non-identical twins showed that a genetic component influences an individual's positive or negative relationship with nature," continues Bengt. "But the study also highlighted the importance of environment in terms of attitudes towards nature."

Moreover, nature can mean completely different things to different people. Some enjoy parks with lawns and planted trees, while others prefer being in the wilderness. The researchers believe that this variation is also determined by both heredity and environment.

"So it's important that we don't standardise nature when planning greenery in our towns and cities," adds Marcus Hedblom, a researcher at SLU and co-author of the article. "We shouldn't replace wild greenery with a park and assume that it will be good for everyone."

Urban nature brings many benefits

In today's urban planning, densification has been a common way to achieve a more sustainable city. This can sometimes come into conflict with efforts to offer nature in cities. A large number of studies suggest that urban parks and green spaces contribute to increased physical activity and recovery from stress. The greenery in our cities is also important in other respects. Trees can clean the air and provide shade to create a tolerable urban climate on hot days.

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Scientists discover external protein network can help stabilize neural connections

The Noelin family of secreted proteins bind to the external portion of AMPA glutamate receptors and stabilize them on the neuronal cellular membrane, a process necessary for transmission of full-strength signals between neurons, according to a study in mice from the National Eye Institute (NEI) and the University of Freiberg, Germany. Without this external, stabilizing protein network, the AMPA receptors are no longer retained at the synapse, leading to weak, short-lived synaptic signals. The findings not only provide insight into processes such as learning and memory but also the development of blinding conditions like glaucoma. The study was published in the journal Neuron. NEI is part of the National Institutes of Health.

"This study shows that Noelins have a crucial job in supporting synapse function in the brain and other neural tissues like the eye's retina," said Stanislav Tomarev, Ph.D., chief of NEI's Section on Retinal Ganglion Cell Biology and co-senior author of the report.

Neurons pass signals from one cell to the next via synapses, specialized connection points between the two cells. The main excitatory synapses in the brain are glutamatergic, meaning that they use the chemical messenger glutamate to transmit their signals across the synapse. The presynaptic "sending" cell emits glutamate, which travels across the synaptic cleft and is sensed by glutamate receptors on the postsynaptic "receiving" cell. These glutamate receptors are ion channels; when the channels sense glutamate, they open, generating a new neuronal signal within the postsynaptic cell. In order to generate a strong signal, sufficient receptors must be present in the correct location of the cell's surface at the synapse.

In a new study, a team of researchers led by Tomarev and Bernd Fakler, M.D., University of Freiberg, used biochemical and genetic methods to explore the complex network of extracellular proteins maintaining the localization of AMPA-type glutamate receptors at neural synapses.

The researchers first took mouse brain tissue, and isolated cellular membranes and their attached proteins. Using mass spectroscopy and specialized analytic techniques, the team worked out which proteins were associating with AMPA receptors in these membranes. The Noelin family of proteins (primarily Noelin 1, but also Noelins 2 and 3, also known as Olfactomedins 1, 2, and 3, respectively), were strongly associated with the AMPA receptors. The researchers also found secreted and membrane-anchored proteins like Neuritin and Brorin, which are known to be present at synapses.

To better understand how the Noelins help regulate neuronal activity, the researchers developed mice lacking all three Noelin proteins. Without Noelins present, synapses in the mouse hippocampus had many fewer AMPA glutamate receptors. And when the researchers attempted to stimulate neurons lacking Noelins, the neuronal signals were much lower than normal.

However, the neuronal signals weren't just lower. One of the key steps in memory formation is long-term neuron signaling, also known as long-term potentiation. This is achieved through recruitment and stabilization of additional glutamate receptors at the synapse over time, leading to a sustained signal through the neuron. In the brains of mice lacking Noelins, this stabilization didn't take place, meaning that not only were the neural signals low, they were short-lived as well.

"While this first study showed the Noelins' role in the brain, these proteins are highly prevalent in the retina as well," Tomarev said. "Our next task is to understand how changes in these secreted protein networks contribute to the development of retinal disorders, including glaucoma."

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New type of star gives clues to mysterious origin of magnetars

Magnetars are the strongest magnets in the Universe. These super-dense dead stars with ultra-strong magnetic fields can be found all over our galaxy but astronomers don't know exactly how they form. Now, using multiple telescopes around the world, including European Southern Observatory (ESO) facilities, researchers have uncovered a living star that is likely to become a magnetar. This finding marks the discovery of a new type of astronomical object -- massive magnetic helium stars -- and sheds light on the origin of magnetars.

Despite having been observed for over 100 years, the enigmatic nature of the star HD 45166 could not be easily explained by conventional models, and little was known about it beyond the fact that it is one of a pair of stars, is rich in helium and is a few times more massive than our Sun.

"This star became a bit of an obsession of mine," says Tomer Shenar, the lead author of a study on this object published today in Science and an astronomer at the University of Amsterdam, the Netherlands. "Tomer and I refer to HD 45166 as the 'zombie star'," says co-author and ESO astronomer Julia Bodensteiner, based in Germany. "This is not only because this star is so unique, but also because I jokingly said that it turns Tomer into a zombie."

Having studied similar helium-rich stars before, Shenar thought magnetic fields could crack the case. Indeed, magnetic fields are known to influence the behaviour of stars and could explain why traditional models failed to describe HD 45166, which is located about 3000 light-years away in the constellation Monoceros. "I remember having a Eureka moment while reading the literature: 'What if the star is magnetic?'," says Shenar, who is currently based at the Centre for Astrobiology in Madrid, Spain.

Shenar and his team set out to study the star using multiple facilities around the globe. The main observations were conducted in February 2022 using an instrument on the Canada-France-Hawaii Telescope that can detect and measure magnetic fields. The team also relied on key archive data taken with the Fiber-fed Extended Range Optical Spectrograph (FEROS) at ESO's La Silla Observatory in Chile.

Once the observations were in, Shenar asked co-author Gregg Wade, an expert on magnetic fields in stars at the Royal Military College of Canada, to examine the data. Wade's response confirmed Shenar's hunch: "Well my friend, whatever this thing is -- it is definitely magnetic."

Shenar's team had found that the star has an incredibly strong magnetic field, of 43,000 gauss, making HD 45166 the most magnetic massive star found to date. "The entire surface of the helium star has a magnetic field almost 100,000 times stronger than Earth's," explains co-author Pablo Marchant, an astronomer at KU Leuven's Institute of Astronomy in BelgiumThis observation marks the discovery of the very first massive magnetic helium star. "It is exciting to uncover a new type of astronomical object," says Shenar, "especially when it's been hiding in plain sight all along."

Moreover, it provides clues to the origin of magnetars, compact dead stars laced with magnetic fields at least a billion times stronger than the one in HD 45166. The team's calculations suggest that this star will end its life as a magnetar. As it collapses under its own gravity, its magnetic field will strengthen, and the star will eventually become a very compact core with a magnetic field of around 100 trillion gauss -- the most powerful type of magnet in the Universe.

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America's wealthiest 10% responsible for 40% of US greenhouse gas emissions

A new study, led by the University of Massachusetts Amherst, reveals that the wealthiest Americans, those whose income places them in the top 10% of earners, are responsible for 40% of the nation's total greenhouse gas emissions. The study, published in  PLOS Climate, is the first to link income, especially income derived from financial investments, to the emissions used in generating that income. The authors suggest that policymakers adopt taxes focused on shareholders and the carbon intensity of investment incomes in order to equitably meet the goal of keeping the global temperature to 1.5 C of warming.

Scientists and environmentalists have long known that consumption -- the amount and kind of food we eat, the vehicles we drive and all the stuff we buy -- is closely linked to greenhouse gas emission. Traditional environmental policy has then sought to either limit consumption or guide it into more environmentally friendly avenues: replacing red meat with plant-based diets or swapping a gas-guzzler for an electric vehicle.

"But," says Jared Starr, a sustainability scientist at UMass Amherst and the lead author of the new study, "consumption-based approaches to limiting greenhouse gas emissions are regressive. They disproportionately punish the poor while having little impact on the extremely wealthy, who tend to save and invest a large share of their income. Consumption-based approaches miss something important: carbon pollution generates income, but when that income is reinvested into stocks, rather than spent on necessities, it isn't subject to a consumption-based carbon tax."

"What happens," Starr asks, "when we focus on how emissions create income, rather than how they enable consumption?"

An answer to that seemingly simple question, however, is fraught with difficulty, because though it's relatively easy to capture a snapshot of wages and salaries -- the main sources of income for 90% of Americans -- it has been very difficult to get a sense of the investment income that makes up a large source of the richest Americans' wealth.

To solve this problem, Starr and his colleagues looked at 30 years' worth of data, drawing first on a database containing over 2.8 billion inter-sectoral financial transfers and following the flow of carbon and income through these transactions. This allowed them to calculate two different values: supplier-based and producer-based greenhouse gas emissions of income.

Supplier-based emissions are those created by industries that supply fossil fuels to the economy. For instance, the operational emissions released by fossil fuel companies are actually quite low, but they make enormous profits by selling oil to others who will burn it.

Producer-based emissions are those directly released by the operation of the business itself -- like a coal-fired power plant.

With these two figures in hand, Starr and his co-authors then linked their emissions data with another database containing detailed demographic and income data for over 5 million Americans. This database parses out income sources differentiating active income -- the wages or salaries earned through employment -- from the passively generated investment income.

Not only did the team find that over 40% of U.S. emissions were attributable with the income flows of the top 10%, they also discovered that the top 1% of earners alone generate 15 -- 17% of the nation's emissions. In general, white, non-Hispanic households had the highest emission-linked income and Black households the lowest. Emissions tended to increase with age, peaking with the 45-54 age group, before declining.

The team also identified "super emitters" with extremely high emissions intensity. These are almost exclusively among the top 0.1% of households, which are overrepresented in the fields of finance, real estate and insurance, manufacturing, and mining and quarrying.

"This research gives us insight into the way that income and investments obscure emissions responsibility," says Starr. "For example, 15 days of income for a top 0.1% household generates as much carbon pollution as a lifetime of income for a household in the bottom 10%. An income-based lens helps us focus in on exactly who is profiting the most from climate-changing carbon pollution, and design policies to shift their behavior."

In particular, Starr and his colleagues point to income and shareholder-based taxation -- rather than taxing consumables.

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The modern sea spider had started to diversify by the Jurassic, study finds

An extremely rare collection of 160-million-year-old sea spider fossils from Southern France are closely related to living species, unlike older fossils of their kind.

These fossils are very important to understand the evolution of sea spiders. They show that the diversity of sea spiders that still exist today had already started to form by the Jurassic.

Lead author Dr Romain Sabroux from the University of Bristol's School of Earth Sciences, said: "Sea spiders (Pycnogonida), are a group of marine animals that is overall very poorly studied.

"However, they are very interesting to understand the evolution of arthropods [the group that includes insects, arachnids, crustaceans, centipedes and millipedes] as they appeared relatively early in the arthropod tree of life. That's why we are interested in their evolution.

"Sea spider fossils are very rare, but we know a few of them from different periods. One of the most remarkable fauna, by its diversity and its abundance, is the one of La Voulte-sur-Rhône that dates back to the Jurassic, some 160 million years ago."

Unlike older sea spider fossils, the La Voulte pycnogonids are morphologically similar (but not identical) to living species, and previous studies suggested they could be closely related to living sea spider families. But these hypotheses were restricted by the limitation of their observation means. As it was impossible to access what was hidden in the rock fossils, Dr Sabroux and his team travelled to Paris and set out to investigate this question with cutting-edge approaches.

Dr Sabroux explained: "We used two methods to reinvestigate the morphology of the fossils: X-ray microtomography, to 'look inside' the rock, find morphological features hidden inside and reconstruct a 3D model of the fossilised specimen; and Reflectance Transformation Imaging, a picture technic that relies on varied orientation of the light around the fossil to enhance the visibility of inconspicuous features on their surface.

"From these new insights, we drew new morphological information to compare them with extant species," explained Dr Sabroux.

This confirmed that these fossils are close relatives to surviving pycnogonids. Two of these fossils belong to two living pycnogonid families: Colossopantopodus boissinensis was a Colossendeidae while another, Palaeoendeis elmii was an Endeidae. The third species, Palaeopycnogonides gracilis, seems to belong to a family that has disappeared today.

"Today, by calculating the difference between the DNA sequences of a sample of species, and using DNA evolution models, we are able to estimate the timing of the evolution that bind these species together," added Dr Sabroux.

"This is what we call a molecular clock analysis. But quite like a real clock, it needs to be calibrated. Basically, we need to tell the clock: 'we know that at that time, that group was already there.' Thanks to our work, we now know that Colossendeidae, and Endeidae were already 'there' by the Jurassic."

Now, the team can use these minimal ages as calibrations for the molecular clock, and investigate the timing of Pycnogonida evolution. This can help them understand, for example, how their diversity was impacted by the different biodiversity crises that distributes over the Earth history.

They also plan to investigate other pycnogonid fossil faunae such as the fauna of Hunsrück Slate, in Germany, which dates from the Devonian, some 400 million years ago.

With the same approach, they will aim to redescribe these species and understand their affinities with extant species; and finally, to replace in the tree of life of Pycnogonida all the pycnogonid fossils from all periods.

Dr Sabroux added: "These fossils give us an insight of sea spiders living 160 million years ago.

"This is very exciting when you have been working on the living pycnogonids for years.

"It is fascinating how these pycnogonids look both very familiar, and very exotic. Familiar, because you can definitely recognize some of the families that still exist today, and exotic because of small differences like the size of the legs, the length of the body, and some other morphological characteristics that you do not find in modern species.

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Iceman Ötzi: Dark skin, bald head, Anatolian ancestry

A research team has used advanced sequencing technology to analyze Ötzi's genome to obtain a more accurate picture of the Iceman's appearance and genetic origins.

Ötzi's genome was decoded for the first time more than ten years ago. This was also the first time the genome of a mummy had been sequenced. The results provided important insights into the genetic makeup of prehistoric Europeans. Advances in sequencing technology have now enabled a research team from the Max Planck Institute for Evolutionary Anthropology and Eurac Research to reconstruct Ötzi's genome more accurately. The results of this recent analysis refine the Iceman's genetic picture: compared to other contemporary Europeans, Ötzi's genome has an unusually high proportion of genes in common with those of early farmers from Anatolia. And, contrary to previous findings, at the time of his death, Ötzi had advanced hair loss and may have even been bald. Furthermore, his skin was darker than previously thought. Ötzi's genes also show a predisposition to diabetes and obesity.

The genetic makeup of most present-day Europeans has resulted mainly from the admixture of three ancestral groups: western hunter-gatherers gradually merged with early farmers who migrated from Anatolia about 8,000 years ago and who were later on joined by Steppe Herders from Eastern Europe, approximately 4,900 years ago.

The initial analysis of the Iceman's genome revealed genetic traces of these Steppe Herders. However, the refined new results no longer support this finding. The reason for the inaccuracy: the original sample had been contaminated with modern DNA. Since that first study, not only have sequencing technologies advanced enormously, but many more genomes of other prehistoric Europeans have been fully decoded, often from skeletal finds. This has made it possible to compare Ötzi's genetic code with his contemporaries. The result: among the hundreds of early European people who lived at the same time as Ötzi and whose genomes are now available, Ötzi's genome has more ancestry in common with early Anatolian farmers than any of his European counterparts.

Ötzi's ancestry and appearance

The research team concludes that the Iceman came from a relatively isolated population that had very little contact with other European groups. "We were very surprised to find no traces of Eastern European Steppe Herders in the most recent analysis of the Iceman genome; the proportion of hunter-gatherer genes in Ötzi's genome is also very low. Genetically, his ancestors seem to have arrived directly from Anatolia without mixing with hunter gatherer groups," explains Johannes Krause, head of the Department of Archaeogenetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, and co-author of the study.

The study also yielded new results about Ötzi's appearance. His skin type, already determined in the first genome analysis to be Mediterranean-European, was even darker than previously thought. "It's the darkest skin tone that has been recorded in contemporary European individuals," explains anthropologist Albert Zink, study co-author and head of the Eurac Research Institute for Mummy Studies in Bolzano: "It was previously thought that the mummy's skin had darkened during its preservation in the ice, but presumably what we see now is actually largely Ötzi's original skin color. Knowing this, of course, is also important for the proper conservation of the mummy."

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Using supernovae to study neutrinos' strange properties

In a new study, researchers have taken an important step toward understanding how exploding stars can help reveal how neutrinos, mysterious subatomic particles, secretly interact with themselves.

One of the less well-understood elementary particles, neutrinos rarely interact with normal matter, and instead travel invisibly through it at almost the speed of light. These ghostly particles outnumber all the atoms in the universe and are always passing harmlessly through our bodies, but due to their low mass and lack of an electric charge they can be incredibly difficult to find and study.

But in a study published today in the journal Physical Review Letters, researchers at The Ohio State University have established a new framework detailing how supernovae -- massive explosions that herald the death of collapsing stars -- could be used as powerful tools to study how neutrino self-interactions can cause vast cosmological changes in the universe.

"Neutrinos only have very small rates of interaction with typical matter, so it's difficult to detect them and test any of their properties," said Po-Wen Chang, lead author of the study and a graduate student in physics at Ohio State. "That's why we have to use astrophysics and cosmology to discover interesting phenomena about them."

Thought to have been important to the formation of the early universe, neutrinos are still puzzling to scientists, despite having learned that they originate from a number of sources, such as in nuclear reactors or the insides of dying stars. But by calculating how self-interactions would affect the neutrino signal from Supernova 1987A, the nearest supernova observed in modern times, researchers found that when neutrinos do interact with themselves, they form a tightly coupled fluid that expands under relativistic hydrodynamics -- a branch of physics that deals with how flows impact solid objects in one of two different ways.

In the case of what's called a "burst outflow," the team theorizes that much like popping a highly pressurized balloon in the vacuum of space would push energy outward, a burst produces a neutrino fluid that moves in all directions. The second case, described as a "wind outflow," imagines a highly pressurized balloon with many nozzles, wherein neutrinos escape at a more constant flow rate, similar to a jet of steady wind.

While the wind-outflow theory is more likely to take place in nature, said Chang, if the burst case is realized, scientists could see new observable neutrino signatures emitted from supernovae, allowing unprecedented sensitivity to neutrino self-interactions.

One of the reasons it's so vital to understand these mechanisms is that if neutrinos are acting as a fluid, that means they are acting together, as a collective. And if the properties of neutrinos are different as a collective than individually, then the physics of supernovae could experience changes too. But whether these changes are due solely to the burst case or the outflow case remains to be seen.

"The dynamics of supernovae are complicated, but this result is promising because with relativistic hydrodynamics we know there's a fork in the road in understanding how they work now," said Chang.

Still, further research needs to be done before scientists can cross off the possibility of the burst case happening inside supernovae as well.

Despite these uncertainties, the study is a huge milestone in answering the decades-old astrophysical issue of how neutrinos actually scatter when ejected from supernovae, said John Beacom, co-author of the study and a professor of physics and astronomy at Ohio State. This study found that in the burst case, unprecedented sensitivity to neutrino self-interactions is possible even with sparse neutrino data from SN 1987A and conservative analysis assumptions.

"This problem has lain basically untouched for 35 years," said Beacom. "So even though we were not able to completely solve how neutrinos affect supernovae, what we're excited about is that we were able to make a substantial step forward."

Down the road, the team hopes their work will be used as a stepping stone to further investigate neutrino self-interactions. Yet because only about two or three supernovae happen per century in the Milky Way, it's likely researchers will have to wait decades more to collect enough new neutrino data to prove their ideas.

"We're always praying for another galactic supernova to happen somewhere and soon, but the best we can do is try to build on what we know as much as possible before it happens," said Chang.

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Oceans release microplastics into the atmosphere

Tiny plastic particles can be found in the sea air even far from coasts, according to a study recently published in the journal Nature Communications. The microplastics come from partly unexpected sources.

Microplastic particles are present in the marine atmosphere even in remote parts of the world. These tiny particles come from land sources but are also re-emitted into the atmosphere from the sea, a study by a team of German and Norwegian researchers led by Dr Barbara Scholz-Böttcher of the University of Oldenburg has shown. The scientists analysed air samples taken from various sites along the Norwegian coast all the way up to the Arctic region. The results have now been published in the scientific journal Nature Communications.

"With our study, we present data on the mass load of different types of plastic in the marine atmosphere for the first time," said Isabel Goßmann, a doctoral candidate at the University of Oldenburg's Institute for Chemistry and Biology of the Marine Environment (ICBM) and first author of the paper. The research team collected the samples during an expedition with the Research Vessel Heincke in 2021. The northernmost destination was Bear Island, the most southerly island of the Svalbard archipelago which lies halfway between the mainland and the archipelago's largest island, Spitsbergen. The team used two different devices to collect air samples. The devices actively pumped in air and were mounted on the bow of the research vessel at a height of twelve metres.

Different types of plastics identified

The scientists analysed the air samples using pyrolysis-gas chromatography-mass spectrometry. With this method they were able to identify and quantify the different types of plastics in the atmosphere through thermal degradation and selective analysis. They then performed model calculations and reconstructed the sources and distribution paths of the particles, each of which is just a few thousandths of a millimetre in size.

The analysis revealed the omnipresence of polyester particles. Polyethylene terephthalate particles, which presumably entered the atmosphere in the form of textile fibres, were detected in all samples. Other plastic types were also present, including polypropylene polycarbonate and polystyrene. Tire wear particles, the tiny debris abraded from tires during driving and especially braking, were identified as another major source of microplastics. The researchers measured concentrations of up to 37.5 nanograms (one nanogram = one-billionth of a gram) of microplastics per cubic metre of air. "These pollutants are ubiquitous. We find them even in remote polar regions," Goßmann stressed.

Until now, little was known about microplastics pollution levels including tire wear particles in the marine atmosphere. "There are only a handful of studies on the concentration of these pollutants in the air," said team leader Scholz-Böttcher. "Our model calculations indicate that the microplastics in the marine atmosphere come from direct sources on the land as well as from the sea," she added. The team posits that plastic particles floating near the sea surface enter the atmosphere via sea spray and bursting air bubbles produced during stormy weather, for example.

Ships are also a source of microplastics

Microplastics find their way into seawater via rivers, but also through the atmosphere -- particles are washed out of the atmosphere by rain, for example. Another potential source is ship traffic: in an earlier study, a team led by Scholz-Böttcher demonstrated that in the open North Sea, the paint and coatings used on ships is the main source of microplastics. In the current study, chemicals such as polyurethanes and epoxy resins typically used in paints and coatings for ships were also found in the air samples.

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Genetically modified neural stem cells show promising therapeutic potential for spinal cord injury

A research team co-led by City University of Hong Kong (CityU) and The University of Hong Kong (HKU) has recently made a significant advancement in spinal cord injury treatment by using genetically modified human neural stem cells (hNSCs). They found that specifically modulating a gene expression to a certain level in hNSCs can effectively promote the reconstruction of damaged neural circuits and restore locomotor functions, offering great potential for new therapeutic opportunities for patients with spinal cord injury.

Traumatic spinal cord injury is a devastating condition that commonly results from accidents such as falls, car crashes or sport-related injuries. Spinal neurons with long axons play critical roles in transmitting signals between the brain and the rest of the body, controlling our movement and sensory perception. Spinal cord injury causes irreversible damage to neurons and axons, which significantly interrupts signal transmission, hence leading to defective locomotion and somatosensory functions.

"Currently, there are no effective clinical management or treatment regimens for patients with spinal cord injury, often leaving them with lifelong disabilities," explained Professor Jessica Liu Aijia, Assistant Professor in the Department of Neuroscience at CityU and the co-leader of the research. "While recent progress has been made in promoting spinal cord regeneration through transplantation of hNSCs derived from human induced pluripotent stem cells, the degree of functional recovery obtained has been modest. This is largely due to the hostile micro-environment around the lesion site, such as the formation of barrier-like structures called astroglial scars and the lack of neurotrophic factors in adults for neuronal differentiation. These factors hinder functional neuronal regeneration, resulting in prolonged repairing and limited functional recovery."

A gene -- SOX9 was reported with a high-level expression at the injury site in previous studies, and the gene itself is the leading cause of the glial scars' formation and the hindrance of neuronal survival and differentiation. To overcome the adverse effects of the post-injury micro-environment, the joint-research team engineered the transplanted neural stem cells with a graded reduction of SOX9 by approximately 50%.

The genetically modified hNSCs expressing half-dose of SOX9 resulted in robust neuronal differentiation and maturation (a process by which immature cells in the nervous system become specialised nerve cells) after transplantation in a hostile microenvironment, promoting neural circuits reconstruction in the spinal cord within a shorter period of time. It also remarkably reduced glial scar accumulation, facilitating long-distance axon outgrowth. The team recorded a large number of axons extending more than 35mm at 3 months post-graft, while relatively less in number with shorter extensions to 25mm with non-modified neural stem cells.

To further explore the therapeutic effects of the modified hNSCs in treating spinal cord injury, the research team used a severe spinal cord injury rat model to evaluate the locomotion recovery after transplantation, including grid walking and consecutive walk. The former recorded limb coordination, such as the capability to grasp a grid rung with correct placement, and the latter recorded stepping patterns to demonstrate their gait and fingertip motor ability.

Compared to rats' graft with non-modified hNSCs, rats' graft with SOX9 gene-modified hNSCs performed much better in placing their affected hind paws on the grid, with fewer misdirected steps after 10 weeks post-injury. In addition, these treated rats demonstrated a good gait with clear paw position and toe movement when walking across a metre-long narrow corridor.

"Our findings reveal a new treatment direction by using a genetically modified strategy to alter the grafts' response to the deleterious microenvironment in vivo after injury, improving cell tolerance to the niche and self-differentiation potential. This brings a new treatment direction for repairing damaged spinal cord," said Professor Liu.

Read more at Science Daily