Culture

When researchers at Lund University in Sweden performed advanced analyses of sputum from the airways of severely ill Covid-19 patients, they found high levels of neutrophil extracellular traps (NETs). It is already a known fact that NETs can contribute to sputum thickness, severe sepsis-like inflammation and thrombosis. After being treated with an already existing drug, the NETs were dissolved and patients improved. The study has now been published in Molecular & Cellular Proteomics.

Using advanced fluorescence microscopy, the researchers examined sputum in the airways of three severely ill Covid-19 patients. The results showed that the samples contained large amounts of one of the immune system's most important agents against bacteria: neutrophils. Neutrophils can form neutrophil extracellular traps (NETs) to capture and neutralise pathogens - primarily bacteria but also viruses.

"We are aware that NETs contribute to sputum viscosity and severe sepsis-like inflammation as well as increase risk of thrombosis i.e. blood clots. We also see these three clinical findings in severely ill Covid-19 patients", says Adam Linder, researcher at Lund University and infectious disease physician at Skåne University Hospital.

Patients with cystic fibrosis can also suffer from increased sputum viscosity. In these cases, a DNase drug is sometimes used to degrade DNA, of which NETs are primarily composed. Could the same drug have an effect on severe Covid 19 cases? A pilot study was conducted after the researchers could see in laboratory test tubes that the DNase preparation degraded the NETs. Five severely ill Covid-19 patients, who required high-flow oxygen therapy and were on the verge of needing mechanical ventilation, were treated with the preparation.

"The patients responded very well to the treatment. Dependency on oxygen therapy diminished for all of them, and they no longer needed oxygen therapy at all after four days. None of them needed to be moved to the intensive care unit, and all of them have recovered and been discharged", says Adam Linder.

Analyses of the patients' sputum showed that they had high levels of NETs prior to the start of treatment, and that these levels were substantially reduced after treatment (see image).

"We have also examined other inflammation parameters using advanced mass spectrometry. Once the drug treatment started, the proinflammatory signalling diminished, which shows that the inflammation was subsiding. Plasma leakage and the viral load were also reduced", says Tirthankar Mohanty, researcher at Lund University.

Even if the results are positive, Adam Linder emphasises that the study is small and that additional research is needed. The researchers are consequently carrying out a phase-2, randomised clinical trial at Skåne University Hospital to examine whether aerosolised DNase (Pulmozyme) is an effective treatment for respiratory failure in conjunction with Covid-19.

"Much of what we see in patients with this pathology could be explained by NETs, but the study needs to be repeated, and in a randomised manner. We also need to know more about when the drug should be administered for the best results", concludes Adam Linder.

Hundreds of genetic drivers affect sexual and reproductive behaviour

Combined with social factors, these can affect longevity and health

An Oxford-led team, working with Cambridge and international scholars, has discovered hundreds of genetic markers driving two of life's most momentous milestones - the age at which people first have sex and become parents.

In a paper published today in Nature Human Behaviour, the team linked 371 specific areas of our DNA, called genetic variants (known locations on chromosomes), 11 of which were sex-specific, to the timing of first sex and birth. These variants interact with environmental factors, such as socioeconomic status and when you were born, and are predictors of longevity and later life disease.

The researchers conducted a Genome-Wide Association Study (GWAS), a search across the entire human genome, to see if there is a relationship between reproductive behaviour and a particular genetic variant. In the largest genomic study ever conducted to date, they combined multiple data sources to examine age at first sex (N=387,338) and birth (N=542,901) in men and women. They then calculated a genetic score, with all genetic loci combined explaining around 5-6% of the variability in the average age at sexual debut or having a first child.

Professor Melinda Mills, Director of the Leverhulme Centre for Demographic Science at the University of Oxford and Nuffield College, and the study's first author says, 'Our study has discovered hundreds additional genetic markers that shape this most fundamental part of our lives and have the potential for deeper understanding of infertility, later life disease and longevity.'

The genetic signals were driven by social factors and the environment but also by reproductive biology, with findings related to follicle-stimulating hormone, implantation, infertility, and spermatid differentiation.

Professor Mills adds 'We already knew that childhood socioeconomic circumstances or level of education were important predictors of the timing of reproduction. But we were intrigued to find literally not only hundreds of new genetic variants, but also uncover a relationship with substance abuse, personality traits such as openness and self-control, ADHD and even predictive of some diseases and longevity .'

Professor Mills says, 'We demonstrated that it is a combination of genetics, social predictors and the environment that drives early or late reproductive onset. It was incredible to see that the genetics underlying early sex and fertility were related to behavioural dis-inhibition, like ADHD, but also addiction and early smoking. Or those genetically prone to postpone sex or first birth had better later life health outcomes and longevity, related to a higher socioeconomic status in during childhood.'

Genetic factors driving reproductive behaviour are strongly related to later life diseases such as Type 2 diabetes and cardiovascular disease.

'It is exciting that the genetics underlying these reproductive behaviours may help us understand later life disease.'

Professor Mills concludes, 'Starting your sexual journey early is rooted in childhood inequality but also has links with health problems, such as cervical cancer and depression. We found particularly strong links between early sexual debut, ADHD and substance abuse, such as early age at smoking. We hope our findings lead to better understanding of teenage mental and sexual health, infertility, later life disease and treatments to help.'

Researchers have developed a more efficient platform for studying proteins that play a key role in regulating gene expression. The approach uses engineered yeast cells to produce enzyme and histone proteins, conduct biochemical assays internally, and then display the results.

"Biomedical and biotech researchers are interested in the mechanisms that allow histones to regulate gene activity," says Alison Waldman, first author of a paper on the work and a Ph.D. student at North Carolina State University. "But the conventional tools for histone research are unwieldy and slow. We wanted to develop something faster and less expensive - and we did."

In complex organisms, chromosomes are largely made up of DNA and a group of proteins called histones. These histones are important for packing the DNA into chromosomes properly, but also play a role in regulating gene expression. In other words, they help determine when and how specific genes are turned on or off.

One of the features that makes histones challenging to study is that they often have chemical modifications that, alone or in combination, alter the role the histone plays in gene expression.

"Histones essentially serve as docking sites for other proteins that influence gene expression, and the chemical modifications we see on histones play a role in determining which proteins have access to a given gene," says Balaji Rao, co-corresponding author of the paper and a professor of chemical and biomolecular engineering at NC State.

And to make matters more complicated, this is a dynamic process. A histone may have no modifications, it may retain a modification for the entire life of the cell, or modifications may be added and removed repeatedly. There is, in short, a lot going on. And enzymes are the catalysts responsible for all of those changes. Basically, enzymes are the mechanism for attaching or removing histone modifications.

So if you really want to understand what's going on with histones, you have to understand the chemical modifications. But if you want to understand the chemical modifications, you need to understand which enzymes are present and what they are doing.

Conventional methods for understanding how enzymes modify a histone involve using one of two techniques. First, you could use chemical synthesis to create enzymes and histone proteins, then conduct an assay in a test tube to see what happens. Second, you could genetically engineer one bacteria to produce an enzyme and engineer other bacteria to produce histone proteins, then harvest the relevant proteins, purify them, then conduct an assay to see what happens.

"Our technique uses a genetically modified yeast cell to produce both the enzyme and the histone," Waldman says. "The chemical modification takes place within the cell, and the resulting modified histone is sent to and displayed on the surface of the cell."

"In other words, the yeast cell makes the relevant proteins, does the assay for you, and then displays the result on top," says Albert Keung, co-corresponding author of the work and an assistant professor of chemical and biomolecular engineering at NC State.

The modified yeast platform is significantly faster than conventional techniques. For example, examining a single enzyme/histone pairing would take a couple days, instead of a week.

"But it's easier to scale up than existing techniques, so you would save substantially more time if you were looking at a lot of proteins," Keung says.

"In addition, there are some proteins that can't be made using chemical synthesis, or that can't be purified," Rao says. "Our technique doesn't require chemical synthesis or purification, which means we can look at proteins that were difficult or impossible to assay in the past."

The researchers demonstrated the utility of the technique by having engineered yeast cells produce two types of histones and a well-studied enzyme called p300, which adds a specific acetyl group modification to histones.

"We've shown that our technique works," Waldman says. "The next step is to begin expanding the modifications we're looking at and scaling up the process."

Near-death experiences are known from all parts of the world, various times and numerous cultural backgrounds. This universality suggests they may have a biological origin and purpose, but exactly what this could be has been largely unexplored.

A new study conducted jointly by the University of Copenhagen (Denmark) and the University of Liege (Belgium) and published in Brain Communications shows how near-death experiences in humans may have arisen from evolutionary mechanisms.

"Adhering to a preregistered protocol, we investigated the hypothesis that thanatosis is the evolutionary origin of near-death experiences", says Daniel Kondziella, a neurologist from Rigshospitalet, Copenhagen University Hospital.

When attacked by a predator, as a last resort defense mechanism, animals can feign death to improve their chances of survival, one example being the opossum. This phenomenon is termed thanatosis, also known as death-feigning or tonic immobility. "As a survival strategy," Daniel Kondziella adds, "thanatosis is probably as old as the fight-or-flight response."

Charlotte Martial, neuropsychologist from the Coma Science Group at ULiège explains: "We first show that thanatosis is a highly preserved survival strategy occurring at all major nodes in a cladogram ranging from insects to fish, reptiles, birds and mammals, including humans. We then show that humans under attack by big animals such as lions or grizzly bears, human predators such as sexual offenders, and 'modern' predators such as cars in traffic accidents can experience both thanatosis and near-death experiences. Furthermore, we show that the phenomenology and the effects of thanatosis and near-death experiences overlap."

Steven Laureys, neurologist and head of GIGA Consciousness research unit and Centre du Cerveau (ULiège, CHU Liège) is excited: "In this paper, we build a line of evidence suggesting that thanatosis is the evolutionary foundation of near-death experiences and that their shared biological purpose is the benefit of survival."

The authors propose that the acquisition of language enabled humans to transform these events from relatively stereotyped death-feigning under predatory attacks into the rich perceptions that form near-death experiences and extend to non-predatory situations.

"Of note, the proposed cerebral mechanisms behind death-feigning are not unlike those that have been suggested to induce near-death experiences, including intrusion of rapid eye movement sleep into wakefulness," Daniel Kondziella explains. "This further strengthens the idea that evolutionary mechanisms are an important piece of information needed to develop a complete biological framework for near-death experiences."

No previous work has tried to provide such a phylogenetic basis. Steven Laureys concludes, "this may also be the first time we can assign a biological purpose to near-death experiences, which would be the benefit of survival."

And Daniel Kondziella adds, "after all, near-death experiences are by definition events that are always survived, without exception."

A team of scientists has devised a more accurate way to predict the effects of climate change on plants and animals -- and whether some will survive at all.

Frequently, ecologists assess an organism's fitness relative to the climate by quantifying its functional traits.

"These are physical properties you can measure -- height, diameter, the thickness of a tree," said UC Riverside biologist Tim Higham. "We believe more information is needed to understand how living things will respond to a changing world."

The team, led by Higham, outlines an alternative model for researchers in an article published today in the journal Trends in Ecology and Evolution.

This new model incorporates the functional traits of an organism as well as environmental variables, such as temperature, habitat structure, and the speed of wind or water an organism interacts with. The team calls these "ecomechanical models."

As oceans rise, strong storms will reach farther inland. The intensity of hurricanes, and the proportion of hurricanes that reach very intense levels, will likely increase with climate change. As a result, Higham said that fluids will exert greater forces on anything in their path. These forces could cause organisms with roots, such as trees, to break or be uprooted.

"If you measure the functional traits of a tree, and we know the speed of the wind, we can predict how much bending will occur," Higham said. "At certain wind speeds, the tree will potentially come down."

The way wind disperses seeds, or how insects and birds fly in the face of strong winds, can potentially influence their fitness. When considering the fate of living things, the physics governing the way they move through space is another important factor accounted for by this new framework. In this sense, ecomechanical models are not limited to understanding the impacts of climate change.

"They can help scientists understand evolutionary patterns and how animals interact differently with their environment as they grow," Higham said.

Environmental conditions can affect how some animals attach to surfaces. For example, geckos can use their famous adhesive system to attach to smooth surfaces. However, the real-world is not often smooth. Therefore, understanding how geckos attach requires knowledge of both the animal's functional traits and the environment's texture, for example.

In order to facilitate use of this model by many different types of scientists, the research team urges the expansion of freely available online databases in which functional traits of organisms have been described in a uniform, standardized way.

This work was years in the making, the product of a working group funded by the National Science Foundation. The group is composed of 24 scientists from Arizona State University; Claremont Colleges; University of British Columbia; University of Illinois, Clark University; the University of Calgary, The State University of Northern Rio de Janeiro, Brazil; Rutgers University; University of Waterloo in Ontario, Canada; University of Washington; George Washington University; Trinity University; UC Berkeley; Cornell University; Towson University, and the American Museum of Natural History.

Many of the participating faculty identify as members of underrepresented groups in science. "Including faculty in early career stages, and from a diversity of backgrounds and lived experiences was of paramount importance to us as we created the working group," said Lara Ferry, biologist and President's Professor from Arizona State University. "We know the best results come from the collective contributions of many different perspectives."

Should these recommendations become widely adopted, the research team feels there will be profound impacts on multiple areas of biology.

"The use of ecomechanical models can help us understand the rules of life," Higham said.

NEW YORK, NY (July 1, 2021)--Lowering levels of a hormone called PTHrP can prevent metastases and improve survival in mice with pancreatic cancer and could lead to a new way to treat patients, according to a study from cancer researchers at Columbia University Vagelos College of Physicians and Surgeons and Herbert Irving Comprehensive Cancer Center and with collaborators at the University of Pennsylvania.

When patients are first diagnosed with pancreatic cancer, the cancer usually has spread to other organs. Because of these metastases, nearly all patients will succumb to their cancer within one year of diagnosis, but no drugs exist to prevent metastasis.

In an effort to find treatments, cancer researchers at Columbia--led by Anil K. Rustgi, MD, and Jason R. Pitarresi, PhD--investigated a hormone called PTHrP. Although PTHrP (parathyroid hormone-related protein) is often highly active in patients with pancreatic cancer, its role in metastasis was unclear.

Loss of PTHrP Dramatically Improves Survival in Mice

The researchers first manipulated the levels of PTHrP in mice with pancreatic cancer. Elimination of PTHrP from mice--with genetic engineering or with an antibody that targets the hormone--not only eliminated metastasis and enhanced overall survival, but also dramatically reduced the size of the initial tumors in the pancreas.

Even in mice with a highly aggressive form of pancreatic cancer, the increase in survival was dramatic, increasing from a median of 111 days to 192 days, with near complete elimination of metastases. The 73% increase in survival, the researchers say, is one of the largest observed in mice with this type of pancreatic cancer, which closely resembles human cancers.

The striking results with mice led the researchers to test the anti-PTHrP antibodies in human pancreatic cancer cells. The results from these experiments were also encouraging: Among 3D organoids derived from pancreatic cancer patients under an IRB-approved protocol, anti-PTHrP antibodies greatly reduced growth and viability of the cells.

Two-Pronged Attack on Cell Growth and Metastasis

Targeting PTHrP attacks pancreatic cancer in two ways, the researchers say. It reduces the ability of the tumor cells to transition from an epithelial state to a mesenchymal state, which is necessary for the creation of new metastases. And targeting PTHrP also prevents the growth of primary and secondary tumors.

"We think these findings provide a strong rationale for further developing anti-PTHrP therapy towards clinical trials," says Rustgi, who adds that the antibody used in the study has the potential to be used in people and credits Richard Kremer, MD, PhD, of McGill University for developing the antibodies. 

"We are hopeful that a drug targeting PTHrP could be used to treat most patients with pancreatic cancer," he says, "because the vast majority have tumors with high levels of PTHrP. There is the potential application to other cancers as well."

Potential with Other Cancers

The researchers originally began investigating PTHrP because its gene is often amplified when another nearby gene, KRAS, is amplified. KRAS has long been recognized as a cancer-promoting gene in pancreatic and other cancers. 

For patients, that may mean anti-PTHrP therapies may have potential in other cancers that are known to harbor KRAS amplifications.

For researchers, the finding also suggests a wider search for cancer-causing genes is needed.

"We feel that PTHrP may have been previously overlooked as a mere passenger gene co-amplified with KRAS, but our study shows that PTHrP has its own tumor-promoting functions," Pitarresi says. "It suggests other so-called 'passenger' genes may have bigger roles in cancer than we initially thought and should be examined more closely."  Rustgi notes "it might open up for combinatorial therapies of targeting the KRAS pathway with an antibody to PTHrP."

SAN FRANCISCO, CA--June 28, 2021--While vaccines are doing a remarkable job of slowing the COVID-19 pandemic, infected people can still die from severe illness and new medications to treat them have been slow to arise. What kills these patients in the end doesn't seem to be the virus itself, but an over-reaction of their immune system that leads to massive inflammation and tissue damage.

By studying a type of immune cells called T cells, a team of Gladstone scientists has uncovered fundamental differences between patients who overcome severe COVID-19 and those who succumb to it. The team, working together with researchers from UC San Francisco and Emory University, also found that dying patients harbor relatively large numbers of T cells able to infiltrate the lung, which may contribute to the extensive lung deterioration that is a hallmark of fatal COVID-19.

The findings, published in the scientific journal Cell Reports, could pave the way for new treatments. Currently, patients who are hospitalized for severe COVID-19 mostly receive dexamethasone, a drug used to reduce inflammation.

"Dexamethasone has been a life saver for many patients," says Gladstone Associate Investigator Nadia Roan, PhD, a senior and corresponding author of the study. "But it is not always sufficient. Our study suggests that it may also be beneficial to directly prevent excess immune cells, including inflammatory T cells, from entering the lung and causing further damage. This approach could be a good complement to anti-inflammatory treatments for COVID-19 patients in the intensive care unit."

The work could also help with disease prognosis.

"Some patients can fall seriously ill from the virus," says Warner Greene, MD, PhD, senior investigator at Gladstone and co-senior author of the study. "We are in dire need for effective ways to anticipate the course of disease, as well as to alleviate lung damage in people with severe COVID-19."

An Imbalance of T Cells

T cells are a crucial component of a successful immune response to many viruses, including SARS-CoV-2, the virus that causes COVID-19. And they are markedly depleted from the blood during severe COVID-19.

To characterize the features of the T cells that remain, the scientists obtained blood samples that had been collected from COVID-19 patients in an intensive care unit (ICU). While about half of these patients eventually recovered, the other half died of the disease. By examining samples taken at different times during the patients' stay in the ICU, the scientists were able to discern trends that they could relate to the disease outcome.

Much has already been learned about the immune response of COVID-19 patients during active infection or after convalescence. For example, studies from convalescent individuals, including Roan's own previous work, reveal how the immune system may provide long-term immunity. Less clear, however, is how the immune system may protect from severe illness or, conversely, contribute to its worsening and to death. To understand the cause of fatalities, the researchers needed to compare fatal to non-fatal severe cases.

Using CyTOF, a technique implemented in Roan's lab that distinguishes the many types of T cells circulating in the body, the scientists found profound differences between the ICU patients' T-cell response to the virus.

"The T-cell response to SARS-CoV-2 increased in patients who were eventually discharged from the ICU and recovered," says Roan, who is also an associate professor of urology at UC San Francisco. "But in patients who eventually died, we sometimes could not detect any T-cell response, or their response decreased over time."

Differences also extended to the composition of the patients' T cells that recognize the SARS-CoV-2 virus. In particular, patients who survived harbored a growing number of T cells called Th1, which are known as important fighters of viral infection. Roan's team found molecular features on the Th1 cells that may explain why they were able to multiply in these patients.

By contrast, they found that patients who died had an elevated number of T cells secreting an inflammatory molecule that would contribute to a worsening of their lung condition. These patients also held more regulatory T cells recognizing the virus. Regulatory T cells normally help quiet down the immune response once infection subsides.

"Perhaps in these patients, regulatory T cells were activated too early and prevented effector T cells from ever mounting an adequate immune response to SARS-CoV-2," says Roan. "This could help explain the patients' paltry response to the virus."

Based on these findings, doctors might be able to predict the course of illness from the relative abundance of Th1 and regulatory T cells that recognize SARS-CoV-2 in a patient's blood.

Roan cautions, however, "Our findings show correlations, not causes. The immune system is complex, with many moving parts and possible interactions between them. Proving the cause of fatality will require further studies."

Stemming the Flow of Lung-Homing Cells

Another potential cause of fatality that the team discovered was a surge in T cells able to infiltrate the lungs of dying patients. By contrast, these cells decreased over time in the patients who recovered.

The scientists call these lung-homing cells "bystander T cells," because they are T cells that do not directly recognize the SARS-CoV-2 virus.

"Our study suggests that during severe COVID-19, bystander T cells are recruited from the blood into the lung, where they may contribute to immune-mediated pathology," says Roan.

What triggers the surge of bystander T cells in severe COVID-19 cases remains unclear, but may be in part mediated by proteins secreted by the lung that recruit these cells. Regardless, stemming their flow into the lung may help reduce lung damage and accelerate the recovery of patients with severe illness.

This approach is particularly promising, as drugs that antagonize a molecule found on the surface of the bystander T cells are already approved for the treatment of metastatic cancer.

"Our next step is to test these drugs in a mouse model of severe COVID-19," says Roan. "We hope that after further scrutiny, such drugs could rapidly be tested as adjunctive treatment for COVID-19."

The adult brain is more malleable than previously thought, according to researchers from the Interdisciplinary Center Herzliya. They trained a 50-year-old man, blind from birth, to "see" by ear, and found that neural circuits in his brain formed so-called topographic maps - a type of brain organization previously thought to emerge only in infancy. This finding reported recently in Neuroimage, sheds new light on the brain's ability for change and holds promise for helping people restore lost function, for example, after a stroke.

"The human brain is indeed more plastic during infancy, but it maintains an enormous potential for reprogramming throughout a person's life," says Prof. Amir Amedi, head of the Baruch Ivcher Institute for Brain, Cognition & Technology at IDC Herzliya, whose team conducted the study.

This research is Amedi's latest challenge to the classic theory of brain organization, according to which the brain has specialized regions, each geared to processing a particular type of sensory information - visual, auditory and so on. The theory holds that for these regions to become organized properly, we must be exposed to the relevant stimuli early in life. This view stems from seminal studies by David H. Hubel and Torsten N. Wiesel - awarded the 1981 Nobel Prize in Physiology or Medicine for this research - showing that without exposure to such stimuli during a critical period in early life, the corresponding sensory system fails to develop. After the critical period, the brain is considered to experience a progressive loss of plasticity, that is, the ability to modify itself based on novel experiences.

But over the past decade, evidence has been accumulating that the brain's sensory regions can handle stimuli outside their "specialization." In a recent review in Neuroscience and Biobehavioral Reviews, Prof. Amedi and Dr. Benedetta Heimler bring together compelling findings in healthy as well as visually- and hearing-impaired individuals, showing that sensory regions deprived of their natural input can be activated by atypical senses - for example, the visual cortex can be activated by sound or touch.

Moreover, the researchers cite studies, including those in Amedi'a lab, in which such atypical activation was achieved in adults. They call for revising the classical concept of critical periods of development: instead of a fixed time window in early life, they suggest focusing on the brain's ability to acquire specialization throughout a person's lifetime, in other words, reversing the loss of plasticity.

In the new study in Neuroimage, Amedi's team trained a man, blind from birth - identified as MaMe, by the first syllables of his first and last name - to recognize objects using a sensory substitution algorithm the lab had developed. The method, EyeMusic, converts visual stimuli into "soundscapes," sound units that convey information about geometric shapes. They convey positions on the y axis by musical pitch, and those on the x axis by time. Thus, tones of a higher pitch denote higher locations, whereas their ordering in time corresponds to their respective positioning from left to right. The researchers scanned MaMe's brain using functional magnetic resonance imaging, before the training and after he had successfully learned to recognize soundscapes.

Hofstatter describe the intriguing results: "After MaMe had learned to interpret soundscapes, his neural circuits were shown to be activated not only in the auditory cortices, but also in the occipital cortex, which receives visual stimuli in sighted people and is not expected to be activated in a congenitally blind individual". Amedi adds: "Not only that, the activation followed a pattern of topographical maps - the highly ordered manner in which external stimuli are mapped in all the sensory systems of the human brain. For example, in the visual cortex of sighted people, neighboring locations are "mapped" onto adjacent neurons, whereas places at a great distance from one another are represented by neurons that are further apart.

MaMe's scans revealed topographic maps tuned to pitch and time - or even to both concurrently - that had not existed in his brain before he'd started the training. For instance, tones of a similar pitch were represented by adjacent neurons, whereas those of radically different pitches - by neurons that were distant from one another. This is the first time topographic maps have been shown to emerge in an adult human brain.

These findings suggest that the brain's sensory regions are primed for specific computations but not specific senses, and that they can be adapted to processing novel sensory experiences.

In fact, past studies by other researchers had shown in newborn laboratory animals that it's possible to "move" the vision function to the brain's hearing region by surgically guiding nerve fibers from the visual cortex to the auditory one. The new study by Hofstetter and colleagues supplies a proof of concept that a similar transition can be done in a noninvasive manner, and in an adult, rather than infant, brain.

"Critical periods are not permanent cut-off points for developing new sensory abilities - rather, in a way, we can give the brain a second chance at any point in life," Amedi says.

He points out that EyeMusic can teach people to develop an ability that is similar to that of bats and dolphins: extracting information about geometric shapes from complex sounds. A major difference, of course, is that the animals had developed this natural ability in the course of hundreds of thousands of years of evolution, whereas in the lab, it can be acquired after a relatively short training.

"With the right technology, one can induce a speeded-up evolution of sorts in the sensory brain," Amedi says.

UNIVERSITY PARK, Pa. -- In the late 1800s, scientists were stumped by the "yellow cells" they were observing within the tissues of certain temperate marine animals, including sea anemones, corals and jellyfish. Were these cells part of the animal or separate organisms? If separate, were they parasites or did they confer a benefit to the host?

In a paper published in the journal Nature in 1882, biologist Sir Patrick Geddes of Edinburgh University proffered that not only were these cells distinct entities, but they were also beneficial to the animals in which they lived. He assigned them to a new genus, Philozoon -- from the Greek phileo, meaning 'to love as a friend,' and zoon, meaning 'animal' -- and then promptly changed his career direction to pioneer professions in urban planning and design. Over time, Geddes's scientific contributions were largely forgotten, and the Philozoon genus name was never used.

Now, more than a century after Geddes's paper was published, an international team of researchers has revisited these "yellow cells," which, after Geddes, had been determined to be photosynthetic algae in the family Symbiodiniaceae.

In a study published in the June 28 issue of the
European Journal of Phycology, the team resurrected the genus Philozoon by using modern technologies to thoroughly characterize two of the species of algae that Geddes had investigated, along with six new related ones.

"Patrick Geddes was ahead of his time in recognizing the ecological significance of the 'yellow cells' found in some animals were actually distinct entities -- micro-algal symbionts -- existing inside the animal's tissues and creating a photosynthetic animal. That was a major revelation! In fact, we now know that microorganisms live in partnership with all multicellular organisms; for example, the bacteria that comprise our human gut microbiomes are essential for our overall health," said Todd LaJeunesse, professor of biology, Penn State, and lead author of the paper. "By emending and reviving the Philozoon genus, we are honoring the work of this natural historian.

LaJeunesse and his colleagues used genetic information; outward physical, or morphological, characteristics; ecological traits; and geographic distributions to define the diversity found within the newly recognized Philozoon genus. They obtained animal samples -- including from soft and stony corals, jellyfish, and sea anemones -- from locations all over the world. They also obtained samples from Italy where Geddes first conducted his original research.

"Because our team comprises scientists from seven countries, we were able to collect all of these samples, and some during the global pandemic," said LaJeunesse. "This study highlights how the spirit of scientific discovery brings people together, even in times of hardship."

"The fact that these algae exist in animals from the Mediterranean Sea to New Zealand to Chile reminds us how widespread these symbioses are on Earth," said LaJeunesse. "Also, since most of the algae in the family Symbiodiniaceae have been thought to be mostly tropical where they are critical to the formation of coral reefs, finding and describing these new species in cold waters highlights the capacity of these symbioses to evolve and live under a broad range of environmental conditions. Life finds a way to persist and proliferate."

The team documented that at their northernmost and southernmost latitudinal extremes, Philozoon experience water temperatures that may reach winter lows of nearly 40 degrees F and summer highs of close to 90 F.

"The abilities of these Philozoons to withstand a wide range of temperatures is likely due to their diversification during the cooler periods of the late Pliocene and most recent Pleistocene epochs," said LaJeunesse. "This adaptation to a range of temperatures could protect them and the animals with which they associate from some of the effects of climate change, at least in the near term. Similarly, adaptation to high latitude environments may condition Philozoon species to tolerating future increases in atmospheric carbon dioxide, which could also help make them resilient to some of the effects of ocean acidification."

He added that careful identification and categorization of these symbiotic algae is essential to understanding the biology and evolution of marine animals that rely on these organisms for their survival.

"The advanced molecular-genetic techniques available to us today have substantially improved our ability to study and understand these microbes," said Pilar Casado-Amezúa, researcher, HyT Association, Spain. "Our new study lays the groundwork for extensive research on the ecological role of animal-algal mutualisms in temperate marine ecosystems."

LaJeunesse noted that although there were a handful of other scientists during the late 1800s that were investigating these 'yellow cells' it was Geddes who unequivocally recognized the full significance of the evidence before him.

He explained, "In describing the associations between the cells and the host animals, Geddes called them 'animal lichens' and eloquently wrote, 'Such an association is far more complex than that of the fungus and alga in the lichen, and indeed stands unique in the physiology as the highest development, not of parasitism, but of the reciprocity between the animal and vegetable kingdoms.' Geddes vigorously contended that these algae were symbiotic in nature. Now, more than a century after their discovery, the true identities of these algae are finally being properly characterized."

Giving women in India's Madhya Pradesh state greater digital control over their wages encouraged them to enter the labor force and liberalized their beliefs about working women, concluded a new study co-authored by Yale economists Rohini Pande and Charity Troyer Moore.

The study, published in the American Economic Review, found that a relatively simple intervention directed to poor women -- providing them access to their own bank accounts and direct deposit for their earnings from a federal workfare program, along with basic training on how to use local bank kiosks -- increased the amount they worked, both in the government program and for other employers.

The women who had access to the banking resources were more likely to report in surveys that a working woman made "a better wife" and that husbands with working wives were better spouses and providers. They also were less likely to say women who work outside the home bear social costs for it.

The study points to the role of gender norms in India's low and declining rate of women in the workforce and it also demonstrates that boosting women's control of their finances can expand their autonomy, said Pande, the Henry J. Heinz II Professor of Economics in Yale's Faculty of Arts and Sciences.

"Economics research often assumes that a country's men and women embrace the same cultural norms, but our study highlights the fact that norms can be differently experienced and held within the same country or culture," said Pande, who is also director of Yale's Economic Growth Center. "Improving a woman's access to her earnings should cause her to work less because she can make the same amount of money with less effort. That we found women work more suggests that some women would prefer to work but are potentially being constrained by social stigma perceived by their husbands' -- specifically, that working wives diminish their husband's social status."

India experienced a period of strong economic growth between 2005 and 2018 with declining fertility rates and gains in education for women, but the rate of female labor force participation fell from 32% to 21% during that period. However, one-third of Indian housewives say in surveys that they are interested in working outside the home. Bringing these latent workers into the workforce would contribute substantially to the country's economic growth, Pande said.

Working in northern Madhya Pradesh, a region marked by particularly restrictive gender norms, the research team collaborated with government and banking partners to enable direct deposit of women's wages from the federal workfare program into their own bank accounts rather than into a male-controlled household account. They conducted a randomized controlled trial covering 197 village clusters and surveyed a total of 4,300 women. The villages were divided among a control group and four treatment groups, only one of which received bank accounts, direct deposit, and training. The researchers refer to this group as being "digitally empowered."

The study found an overall increase in labor supply among digitally empowered women compared to women who only received a bank account. They were 28% more likely to have participated in the workfare program during the past year than were the women who only received a bank account and 13% more likely to report any paid work in the previous month, according to the findings. The digitally empowered group also earned 24% more (950 rupees) annually from the private sector, which is notable given that the direct deposit was only linked to workfare wages and private-sector work often is paid in cash.

"The fact that digitally empowered women were earning more in the private sector suggests that having more control of their earnings spread into other aspects of their lives, giving them the ability to negotiate with other household members to work more outside their homes," said Troyer Moore, director of South Asia economics research at Yale's MacMillan Center for International and Area Studies. "It tells us that a simple policy intervention has altered a cultural norm, which is very exciting."

The researchers separated the sample into two groups: women who had worked in the government program before, and those who had not. In surveys, women in the latter group reported having less decision-making power, and that their husbands were more likely to associate a working wife with social stigma. The data showed that while the increases in work outside the home trailed off among those who had previously worked in the program by the study's third year, it persisted for the socially constrained group, demonstrating that the intervention had the most durable impact on women facing the greatest barriers to work.

Study participants were surveyed to measure their thoughts about working and non-working women. The results showed that, compared to women who received only bank accounts, digitally empowered women liberalized their personal beliefs about women's work.

While researchers were conducting the study, the Indian government began scaling up direct deposit of workfare wages into female-owned accounts nationwide, but the effort involved neither targeted outreach to eligible women nor any systematic account training, key elements of the most successful intervention that the study identified, the researchers said.

"We look forward to working with government partners to scale up the policy intervention in a manner that maximizes the benefits to women," Troyer Moore said.

Based on fossil finds, we know that the vast majority of species that once inhabited the earth have become extinct. For example, there are about 5,500 mammal species living on the planet today, but we know of at least 160,000 fossil species, so for every mammal species living today, there are at least 30 extinct ones. We therefore know with great certainty that the lineages of living things come and go along immense time scales. But what factors cause these lineages to come into being and disappear is still an unsolved question.

To investigate this problem more closely, the research team focused on a charismatic group: the proboscideans, which include today's elephants, but also the extinct mammoths, mastodons and dinotheria. The history of the proboscideans is one of glory and decline. Although today there are only three species of elephants left in Asia and Africa, we know fossil more than 180 species of these animals, which also inhabited Europe, South America and North America. "In the past, more than 30 species of these giants lived on the planet at the same time, and many ecosystems were so productive and ecologically complex that it was not uncommon for three or more species of proboscideans to live together in the same ecosystem," explains Juan López Cantalapiedra, a researcher at the University of Alcalá in Spain and lead author of the new study.

However, as the researchers were able to show, proboscideans were not always so diverse. In the first 30 million years of their history, the group was limited to Africa and Arabia, which together formed an isolated continent that was not connected to Asia as it is today. Until then, the evolution of these animals was quite slow and the few existing species were ecologically quite similar. But about 22 million years ago, Afro-Arabia connected with Eurasia and the proboscideans spread all over the world. The new challenges faced by the lineages scattered outside Afro-Arabia caused the ecology of the group to multiply. Species emerged with different, highly diverse tooth shapes, including strange, shovel-shaped tusks. "This ecological diversity reduced competition between species and allowed several of them to live together in the same ecosystem at the same time," points out Fernando Blanco, a researcher at the Museum für Naturkunde Berlin. This marked the beginning of the golden age of proboscideans. "If the link between Afro-Arabia and Eurasia had not happened, or had happened at a different time, the evolutionary history of proboscideans would have been radically different," Blanco adds.

The new study also revealed the factors that determined the group's ultimate decline. Seven million years ago, modern savannah ecosystems spread across all continents, and because of this change, many proboscideans adapted to life in forested areas disappeared. At the same time, however, new forms appeared that were able to feed on less nutritious plant material such as wood and especially grass, which is typical of savannas. Today's elephants are among these evolutionary newcomers.

About 3 million years ago, the rules of the game changed again with the onset of the ice ages. In Eurasia and Africa, the extinction rate quintupled. But as the researchers were able to show, the extinction rate rose even further in Eurasia and America 160,000 and 75,000 years ago, respectively. Were humans responsible for this debacle? "At that time, Homo sapiens had not yet made it to these continents," Cantalapiedra explains. The analyses showed that the different phases of extinction were linked to the decline and rapid fluctuations in global temperatures as a result of the ice ages. "The impact of our ancestors probably contributed to the extinction of the few surviving species, such as the woolly mammoth, a little later."

Boulder, Colo., USA: The Geological Society of America regularly publishes
articles online ahead of print. GSA Bulletin topics include
multiple articles about the dynamics of China and Tibet; the end-Permian
terrestrial extinction paradigm in South Africa; prehistoric lava flows
from the urban district of Catania (Etna volcano, Italy); the debated
origins of granite, and “a tale of two Tweefonteins.” You can find these
articles at

https://bulletin.geoscienceworld.org/content/early/recent

.

Authigenic berthierine and incipient chloritization in shallowly buried
sandstone reservoirs: Key role of the source-to-sink context

Maxime Virolle; Benjamin Brigaud; Daniel Beaufort; Patricia Patrier; Eid
Abdelrahman ...

Abstract:
Chlorite is recognized worldwide as a key mineral that inhibits the
development of quartz cement in deeply buried sandstone reservoirs.
Iron-rich chlorite is mainly formed by the transformation of a precursor
clay mineral; however, few studies have focused on the early stages before
the crystallization of chlorite. This study analyzed shallowly buried
(400−1000 m) coastal sandstones from within the Wealden Group of the Paris
Basin. Berthierine, a 7 Å trioctahedral clay mineral belonging to the
serpentine group, approximatively with same chemistry as chlorite but a
different crystal structure, has been identified in a 900-m-deep well but
not in a 400−600-m-deep well. Berthierine has mainly been observed as clay
coatings around detrital grains with a typical honeycomb texture.
Nanopetrographic observations suggest that the honeycomb textural
organization of the clay particles found in deeper buried sandstone
reservoirs (>1500 m) is acquired from a berthierine precursor at shallow
depths. However, small amounts of quartz overgrowths are observed on the
surface of detrital grains at shallow depths and low temperature (below 40
°C), and it is believed that precursor berthierine coatings are primarily
responsible for the inhibition of quartz overgrowths before Fe-rich
chlorite is formed. This suggests that the key mineral primarily
controlling the reservoir quality of deeply buried sandstone reservoirs is
berthierine rather than iron-rich chlorite, which challenges the commonly
accepted assertion that chlorite coating is the main process that inhibits
quartz overgrowths. The source-to-sink context of the Paris Basin during
the Early Cretaceous was decisive with respect to the supply of sands and
berthierine clay precursors (in particular kaolinite and iron-rich,
hydroxy-interlayered clay minerals) to the center of the basin.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35865.1/605739/Authigenic-berthierine-and-incipient

Subduction initiation-induced rapid emplacement of garnet-bearing
peridotites at a nascent forearc: Petrological and Os-Li isotopic
evidence from the Purang ophiolite, Tibet

Xiao-Han Gong; Ji-Feng Xu; Ren-Deng Shi; Ben-Xun Su; Qi-Shuai Huang ...

Abstract:
Garnet-bearing peridotites commonly occur in the deeper parts of mature or
thickened oceanic lithosphere, and are rarely exhumed and emplaced onto the
seafloor. The Purang ophiolitic peridotites in south Tibet contain rare
symplectite pseudomorphs after garnet, offering a unique window into the
still poorly understood evolution of the deep oceanic lithosphere. Here,
integrated petrologic and Os-Li isotopic data are used to constrain the
evolution and dynamics of emplacement for these garnet peridotite
protoliths. The Purang peridotites show wide variations of chemical
compositions (spinel Cr#: 0.2−0.8) and Os model ages (up to 2.0 Ga), thus
representing a piece of heterogeneous oceanic mantle lithosphere. Dunite
channels show two distinctive groups of Cr# of spinels and Os-isotope
compositions, with the low- to medium-Cr# (0.2−0.6) and high-Cr# (0.7−0.8)
dunites reflecting the reaction of host lherzolites/harzburgites with
percolating mid-ocean ridge basalt−like and boninitic melts, respectively.
This confirms recent subduction initiation-related melt percolation in the
Purang peridotites. Coexisting olivines and pyroxenes in the peridotites
show systematic Li elemental and isotopic disequilibrium, suggesting fast
cooling of the peridotites to Li closure temperature shortly after the melt
percolations, likely during exhumation of the peridotites onto the
seafloor. This supports a close link between subduction initiation and
tectonic emplacement of the Purang peridotites. Combined with other
geological evidence, we suggest the Purang peridotites may originate from
the deep part of old, thick oceanic lithosphere of the Neo-Tethys. This
thick oceanic lithosphere was progressively weakened and thinned likely
during widespread plume-lithosphere interaction, triggering the
transformation of garnet peridotite protoliths to spinel peridotites.
Subsequently, initiation of a new subduction zone along the lithospheric
weakness caused rapid ascent and emplacement of the Purang peridotites at a
nascent forearc.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35960.1/604591/Subduction-initiation-induced-rapid-emplacement-of

A tale of two Tweefonteins: What physical correlation, geochronology,
magnetic polarity stratigraphy, and palynology reveal about the
end-Permian terrestrial extinction paradigm in South Africa

Robert A. Gastaldo; Johann Neveling; John W. Geissman; Sandra L. Kamo;
Cindy V. Looy

Abstract:
The contact between the Daptocephalus to Lystrosaurus declivis (previously Lystrosaurus)
Assemblage Zones (AZs) described from continental deposits of the Karoo
Basin was commonly interpreted to represent an extinction crisis associated
with the end-Permian mass-extinction event at ca. 251.901 ± 0.024 Ma. This
terrestrial extinction model is based on several sections in the Eastern
Cape and Free State Provinces of South Africa. Here, new stratigraphic and
paleontologic data are presented for the Eastern Cape Province, in
geochronologic and magnetostratigraphic context, wherein lithologic and
biologic changes are assessed over a physically correlated stratigraphy
exceeding 4.5 km in distance. Spatial variation in lithofacies demonstrates
the gradational nature of lithostratigraphic boundaries and depositional
trends. This pattern is mimicked by the distribution of vertebrates
assigned to the Daptocephalus and L. declivis AZs where
diagnostic taxa of each co-occur as lateral equivalents in landscapes
dominated by a Glossopteris flora. High-precision U-Pb zircon
(chemical abrasion-isotope dilution-thermal ionization mass spectrometry)
age results indicate maximum Changhsingian depositional dates that can be
used as approximate tie points in our stratigraphic framework, which is
supported by a magnetic polarity stratigraphy. The coeval nature of
diagnostic pre- and post-extinction vertebrate taxa demonstrates that the L. declivis AZ did not replace the Daptocephalus AZ
stratigraphically, that a biotic crisis and turnover likely is absent, and
a reevaluation is required for the utilization of these biozones here and
globally. Based on our data set, we propose a multidisciplinary approach to
correlate the classic Upper Permian localities of the Eastern Cape Province
with the Free State Province localities, which demonstrates their
time-transgressive nature.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35830.1/604557/A-tale-of-two-Tweefonteins-What-physical

Paleomagnetic dating of prehistoric lava flows from the urban district
of Catania (Etna volcano, Italy)

Andrea Magli; Stefano Branca; Fabio Speranza; Gilda Risica; Gaia Siravo ...

Abstract:
Determining the ages of past eruptions of active volcanoes whose slopes
were historically inhabited is vitally important for investigating the
relationships between eruptive phenomena and human settlements. During its
almost three-millennia-long history, Catania—the biggest city lying at the
toe of Etna volcano—was directly impacted only once by the huge lava flow
emplaced during the A.D. 1669 Etna flank eruption. However, other lava
flows reached the present-day Catania urban district in prehistoric ages
before the founding of the city in Greek times (729/728 B.C., i.e.,
2679/2678 yr B.P.). In this work, the Holocene lava flows of Barriera del
Bosco, Larmisi, and San Giovanni Galermo, which are exposed in the Catania
urban district, were paleomagnetically investigated at 12 sites (120
oriented cores). Paleomagnetic dating was obtained by comparing flow-mean
paleomagnetic directions to updated geomagnetic reference models for the
Holocene. The Barriera del Bosco flow turns out to represent the oldest
eruptive event and is paleomagnetically dated to the 11,234−10,941 yr B.P.
and 8395−8236 yr B.P. age intervals. The mean paleomagnetic directions from
the San Giovanni Galermo and Larmisi flows overlap when statistical
uncertainties are considered. This datum, along with geologic, geochemical,
and petrologic evidence, implies that the two lava flows can be considered
as parts of a single lava field that erupted in a narrow time window
between 5494 yr B.P. and 5387 yr B.P. The emplacement of such a huge lava
flow field may have buried several Neolithic settlements, which would thus
explain the scarce occurrence of archaeological sites of that age found
below the town of Catania.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B36026.1/602750/Paleomagnetic-dating-of-prehistoric-lava-flows

Migmatite and leucogranite in a continental-scale exhumed strike-slip
shear zone: Implications for tectonic evolution and initiation of
shearing

Junyu Li; Shuyun Cao; Xuemei Cheng; Franz Neubauer; Haobo Wang ...

Abstract:
Plutons within continental strike-slip shear zones bear important
geological processes on late-stage plate transpression and
continent-continent collision and associated lateral block extrusion.
Where, when, and how intrusions and shearing along transpressional
strike-slip shear zones respond to plate interactions, however, are often
debated. In this study, we investigated migmatite associated leucogranite
and pegmatite from the exhumed >1000-km-long Ailao Shan–Red River
left-lateral strike-slip shear zone in Southeast Asia that was active
during India-Eurasia plate convergence. Most zircons from the migmatites
and leucogranitic intrusions present inherited core-rim structure. The
depletion of rare earth element patterns and positive Eu anomalies suggest
that leucosomes and leucogranites are the result of crustal anatexis.
Zircon rims from the foliated migmatites and leucogranites record U-Pb ages
of 41−28 Ma, revealing the timing of the Cenozoic crustal anatexis event
along this strike-slip shear zone. Ages of the magmatic zircons from the
unfoliated pegmatites provide the timing of the termination of a
high-temperature tectono-thermal event and ductile left-lateral shearing at
26−23 Ma. The Cenozoic crustal anatexis along the Ailao Shan–Red River
strike-slip shear zone indicates that thickened crust underneath the shear
zone involved previously subducted crust. We propose that the Cenozoic
thermal state has an important effect on the crustal anatexis and thus on
the rheological behavior of the lithosphere by thermal weakening, which
plays an essential role in localizing the initiation of the deep-seated
lower-crustal shear zone.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35988.1/602751/Migmatite-and-leucogranite-in-a-continental-scale

The impact of a tear in the subducted Indian plate on the Miocene
geology of the Himalayan-Tibetan orogen

Rui Wang; Roberto F. Weinberg; Di-Cheng Zhu; Zeng-Qian Hou; Zhi-Ming Yang

Abstract:
The Yadong-Gulu Rift, cutting across the Gangdese belt and Himalayan
terranes, is currently associated with a thermal anomaly in the mantle and
crustal melting at 15−20 km depth. The rift follows the trace of a tear in
the underthrusted Indian continental lithospheric slab recognized by high
resolution geophysical methods. The Miocene evolution of a 400-km-wide band
following the trace of the tear and the rift, records differences
interpreted as indicative of a higher heat flow than its surroundings. In
the Gangdese belt, this band is characterized by high-Sr/Y granitic
magmatism that lasted 5 m.y. longer than elsewhere and by the highest
values of εHf(i) and association with the largest porphyry Cu-Mo
deposits in the Gangdese belt. Anomalously young magmatic rocks continue
south along the rift in the Tethyan and Higher Himalayas. Here, a
300-km-wide belt includes some of the youngest Miocene Himalayan
leucogranites; the only occurrence of mantle-derived mafic enclaves in a
leucogranite; young mantle-derived lamprophyre dikes; and the youngest and
hottest migmatites in the Higher Himalayas. These migmatites record a
history of rapid exhumation contemporaneous with the exhumation of Miocene
mafic eclogite blocks, which are unique to this region and which were both
heated to >800 °C at ca. 15−13 Ma, followed by isothermal decompression.
We suggest that the prominent tear in the Indian lithosphere, sub-parallel
to the rift, is the most likely source for these tectono-thermal anomalies
since the Miocene.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B36023.1/602752/The-impact-of-a-tear-in-the-subducted-Indian-plate

The timeline of prolonged accretionary processes in eastern Central
Asian Orogenic Belt: Insights from episodic Paleozoic intrusions in
central Inner Mongolia, North China

Lingling Yuan; Xiaohui Zhang; Zhili Yang

Abstract:
Updating magmatic profile in crucial constituent terranes across the
Central Asian Orogenic Belt presents a key to chronicling the timeline of
prolonged accretionary processes and termination of the Paleo-Asian Ocean
in the northern China−southern Mongolia tract. Here we performed a
systematic geochronological and geochemical study on a spectrum of
Paleozoic intrusions from the Erenhot region in central Inner Mongolia,
North China, within the hinterland of the tract, with four distinct
magmatic episodes unraveled. Combining these episodes with the previously
documented events from contiguous regions defines two major
tectono-magmatic cycles. The early Paleozoic cycle (500−450 Ma) evolved
from initial fluid-fluxed tholeiitic and calc-alkaline granitoids to
melt-fertilized mafic-intermediate magmatism. It appears to experience the
initiation and maturation of a Western Pacific-type intra-oceanic arc
system that culminated in ridge subduction. The late Paleozoic cycle
expanded in magmatic expression from sporadic Late Devonian (373−365 Ma)
calc-alkaline intermediate-felsic pulses through Early-Middle Carboniferous
(356−320 Ma) medium to high-K calc-alkaline flare-up to a Late
Carboniferous−Early Permian (310−277 Ma) province of diverse lithologies.
These magmatic episodes seem to encompass a complete active continental
arc−back-arc system that spanned from resuming oceanic plate subduction
through slab rollback and backarc rifting to ridge-trench collision and
backarc basin closure. Featuring a Rodinia-aged terrane affinity and a
representative Paleozoic magmatic profile, the Erenhot region provides an
optimal site for correlating the evolution of mosaic terranes in southern
Mongolia and northern China, and for evaluating the coupled evolution of
shifting tectonic regimes and plural crustal generation mechanisms within a
retreating accretionary orogen.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35907.1/602753/The-timeline-of-prolonged-accretionary-processes

Pure sediment-derived granites in a subduction zone

Jian Xu; Xiao-Ping Xia; Qiang Wang; Christopher J. Spencer; Chun-Kit Lai
...

Abstract:
The Earth is unique in the Solar System due to significant volumes of
granite in the lithosphere. However, the origins of granites are still
highly debated, especially sediment-derived granites, which are often
treated as a geochemical end-member of the continental crust. In the Yunnan
region of South China, we identify the occurrence of pure sediment-derived
granite in a subduction system. The suite of strongly peraluminous granite
reported herein is interpreted to represent pure metasedimentary melts
based on their whole-rock elemental and Sr-Nd-B and zircon Hf-O isotopic
compositions. These Late Permian−Early Triassic (ca. 254−248 Ma) granites
are characterized by radiogenically enriched Sr, Nd, and Hf isotopic
signatures. They show δ11B and δ18O signatures akin
to those of continental shales. Geochemical modeling indicates no
contributions from the mantle that can be detected. Considering the
regional tectonic evolution, these granites are suggested to be formed in a
subduction zone by decompression melting of rapidly exhumed back-arc
sediments. We posit that decompression melting was triggered by widespread
extension and thinning of the crust prompted by rollback of the subducting
oceanic crust. These granites thus provide evidence that granite formation
in subduction zones does not necessarily contribute to crustal growth.
These subduction-related pure sediment-derived granites have different
elemental ratios and contents (e.g., Al2O3/TiO 2 and Yb) from the Himalayan leucogranites. Considering their
source compositions (e.g., pelitic rocks), which are similar to those of
the Himalayan leucogranites, these differences are likely due to their
higher formation temperature and lower pressure despite a great similarity
in isotopic compositions. Identification of pure sediment-derived, strongly
peraluminous granites (SPGs) in subduction systems provides an important
geodynamic mechanism for crustal anatexis, which can both geochemically and
tectonically complement their collisional counterparts identified in the
Himalayas.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B36016.1/602698/Pure-sediment-derived-granites-in-a-subduction

Mafic-ultramafic intrusion formed by multi-stage evolution of hydrous
basaltic melts

Qi-Wei Li; Jun-Hong Zhao; Mei-Fu Zhou; Jian-Feng Gao

Abstract:
The magmatic processes beneath the active continental margins are very
complicated and affect structures and compositions of the arc roots.
Neoproterozoic igneous rocks are widely distributed around the margins of
the Tarim Block in NW China. The Xingdier mafic-ultramafic intrusion is a
composite body, located at the northern margin of the Tarim Block, and
consists of gabbro, pyroxenite, and peridotite units. The gabbro unit has a
secondary ion mass spectrometry zircon U-Pb age of 727 ± 5 Ma. Rocks from
the Xingdier intrusion have a large range of MgO (12.9−32.8 wt%) and SiO 2 (43.0−57.9 wt%), and low K2O+Na2O
(0.11−2.25 wt%) contents. They have right inclined chondrite-normalized
rare earth element patterns with (La/Yb)N ratios of 2.2−8.6.
Their primitive mantle normalized trace element patterns show arc-affinity
geochemical features characterized by enrichment in Rb, Ba, Th, U, and Pb
and depletion in Nb, Ta, and Ti. They have variable initial 87
Sr/86Sr ratios (0.7063−0.7093), εNd(t) values (−2.9 to −7.8),206Pb/204Pb (17.08−17.80), 207Pb/ 204Pb (15.42−15.49), and 208Pb/204Pb
ratios (37.48−38.05), forming an evolution trend from the peridotite unit
to the gabbro and pyroxenite units. Clinopyroxene in the three units is
chemically similar to those formed in hydrous magmas. The spinel inclusions
in olivine from the peridotite unit show unmixing texture and have high Al
contents and oxygen fugacity of ∼FMQ+1. Therefore, the parental magma was
probably derived from a lithospheric mantle enriched by slab-derived
fluids. Rocks from the gabbro and peridotite units are proposed to have
been derived from olivine-normative melts, whereas rocks from the
pyroxenite unit are cumulates from the quartz-normative melts. Such
contrasting parental magmas resulted from variable degrees of crustal
contamination and fractional crystallization in the arc root.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35920.1/601081/Mafic-ultramafic-intrusion-formed-by-multi-stage

Origin of syn-collisional granitoids in the Gangdese orogen: Reworking
of the juvenile arc crust and the ancient continental crust

Yu-Wei Tang; Long Chen; Zi-Fu Zhao; Yong-Fei Zheng

Abstract:
Granitoids at convergent plate boundaries can be produced either by partial
melting of crustal rocks (either continental or oceanic) or by fractional
crystallization of mantle-derived mafic magmas. Whereas granitoid formation
through partial melting of the continental crust results in reworking of
the pre-existing continental crust, granitoid formation through either
partial melting of the oceanic crust or fractional crystallization of the
mafic magmas leads to growth of the continental crust. This category is
primarily based on the radiogenic Nd isotope compositions of crustal rocks;
positive εNd(t) values indicate juvenile crust whereas negative
εNd(t) values indicate ancient crust. Positive εNd(t)
values are common for syn-collisional granitoids in southern Tibet, which
leads to the hypothesis that continental collision zones are important
sites for the net growth of continental crust. This hypothesis is examined
through an integrated study of in situ zircon U-Pb ages and Hf isotopes,
whole-rock major trace elements, and Sr-Nd-Hf isotopes as well as mineral O
isotopes for felsic igneous rocks of Eocene ages from the Gangdese orogen
in southern Tibet. The results show that these rocks can be divided into
two groups according to their emplacement ages and geochemical features.
The first group is less granitic with lower SiO2 contents of
59.82−64.41 wt%, and it was emplaced at 50−48 Ma in the early Eocene. The
second group is more granitic with higher SiO2 contents of
63.93−68.81 wt%, and it was emplaced at 42 Ma in the late Eocene. The early
Eocene granitoids exhibit relatively depleted whole-rock Sr-Nd-Hf isotope
compositions with low (87Sr/86Sr)i ratios
of 0.7044−0.7048, positive εNd(t) values of 0.6−3.9, ε Hf(t) values of 6.5−10.5, zircon εHf(t) values of
1.6−12.1, and zircon δ18O values of 5.28−6.26‰. These isotopic
characteristics are quite similar to those of Late Cretaceous mafic arc
igneous rocks in the Gangdese orogen, which indicates their derivation from
partial melting of the juvenile mafic arc crust. In comparison, the late
Eocene granitoids have relatively lower MgO, Fe2O3,
Al2O3, and heavy rare earth element (HREE) contents
but higher K2O, Rb, Sr, Th, U, Pb contents, Sr/Y, and (La/Yb) N ratios. They also exhibit more enriched whole-rock Sr-Nd-Hf
isotope compositions with high (87Sr/86Sr) i ratios of 0.7070−0.7085, negative εNd(t) values of
−5.2 to −3.9 and neutral εHf(t) values of 0.9−2.3, and
relatively lower zircon εHf(t) values of −2.8−8.0 and slightly
higher zircon δ18O values of 6.25−6.68‰. An integrated
interpretation of these geochemical features is that both the juvenile arc
crust and the ancient continental crust partially melted to produce the
late Eocene granitoids. In this regard, the compositional evolution of
syn-collisional granitoids from the early to late Eocene indicates a
temporal change of their magma sources from the complete juvenile arc crust
to a mixture of the juvenile and ancient crust. In either case, the
syn-collisional granitoids in the Gangdese orogen are the reworking
products of the pre-existing continental crust. Therefore, they do not
contribute to crustal growth in the continental collision zone.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35928.1/601082/Origin-of-syn-collisional-granitoids-in-the

Mantle source of tephritic porphyry in the Tarim Large Igneous Province
constrained from Mg, Zn, Sr, and Nd isotope systematics: Implications
for deep carbon cycling

Weiliang Kong; Zhaochong Zhang; Zhiguo Cheng; Bingxiang Liu; M. Santosh ...

Abstract:
The nature and source of magmatism associated with large igneous provinces
(LIPs) remain disputed. Here we investigate the role of recycled materials
that contributed to mantle heterogeneity in the Tarim Large Igneous
Province (TLIP) in China through integrated Zn−Mg−Sr−Nd isotopes of a rare
tephritic rock suite. The Sr−Nd isotopes [(87Sr/86Sr)i = 0.70368−0.70629; εNd(t) = −0.25−4.64] and δ 26Mg values (−0.23‰ to −0.34‰) of the tephritic porphyries are
consistent with a normal mantle origin. In contrast, the whole rock and
pyroxene phenocrysts yield δ66Zn values of +0.28‰ to +0.46‰ and
+0.30‰ to +0.39‰, which are slightly heavier than those of the terrestrial
mantle (+0.16 ± 0.06‰) and mid-oceanic-ridge basalts (MORBs) (+0.27 ±
0.05‰). We exclude the possibility that the heavy Zn isotopes of the
Wajilitag tephritic porphyries are caused by magmatic processes such as
fractional crystallization and partial melting and correlate the isotopic
features to the role of altered oceanic crust along with magnesite in the
mantle source. The Wajilitag tephritic porphyry displays trace-element
patterns similar to those of the melts from natural hornblendite,
especially those of hornblendite + peridotite. Additionally, the
geochemical characteristics such as enrichment in Nb and Ta, depletion in
K, high TiO2, and constant Na2O/K2O ratios
also suggest that the tephritic porphyries were derived from an
amphibole-bearing source contributed by altered oceanic crust along with
sedimentary carbonates. Our study provides insight into the contribution of
subducted materials to the mantle heterogeneity beneath the TLIP and
highlights the role of subduction in the deep carbon cycle and subducted
slab-lithosphere-plume interaction in the generation of LIPs.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35902.1/600886/Mantle-source-of-tephritic-porphyry-in-the-Tarim

Sedimentology, geochronology, and provenance of the late Cenozoic
“Yangtze Gravel”: Implications for Lower Yangtze River reorganization
and tectonic evolution in southeast China

Ping Wang; Hongbo Zheng; Yongdong Wang; Xiaochun Wei; Lingyu Tang ...

Abstract:
The evolution of the Yangtze River, the longest river in Asia, provides a
spectacular example for understanding the Cenozoic interaction between
tectonics, climate, and surficial processes. The oldest Lower Yangtze
deposits, characterized by ∼100-m-thick sequences of unconsolidated
conglomerate, sandstone, and siltstone, referred to as “Yangtze Gravel,”
have been recently dated >23 Ma, indicating a pre-Miocene establishment
of a through-going river. However, the link between river integration and
tectonic evolution has never been established due to the limited study of
these sediments. Here, we report sedimentology, geochronology, and
provenance of the Yangtze Gravel based on 17 stratigraphic sections exposed
along the Lower Yangtze River. Our new chronostratigraphic results,
including 40Ar/39Ar ages from the overlying basalt and fossil-based
stratigraphic correlation, suggest an early-middle Miocene age for these
sediments. Detailed analysis of lithofacies reveals several sequences of
coarse-grained channel-belt deposits (channel fills and bars), indicating
braided alluvial deposition across the Jianghan Basin, North Jiangsu-South
Yellow Sea Basin, and East China Sea Shelf Basin. This ancient Lower
Yangtze River is further characterized by petrography and detrital zircon
U-Pb geochronology results which show similar provenance and erosion
pattern as the present-day Yangtze River. However, the ancient river in
early-middle Miocene is an alluvial, bedload-dominated braided river with
higher stream power and a more prolonged course flowing into the East China
Sea Shelf Basin. These differences between ancient and modern Lower Yangtze
River reflect varied climate and paleogeography in southeast China during
the late Cenozoic. Compared with the Paleogene red-colored, halite-bearing,
Ephedripite pollen-dominated, lacustrine deposits in Jianghan Basin and
North Jiangsu-South Yellow Sea Basin, the deposition of yellow to
green-colored, coarse-grained, arboreal pollen, and wood-dominated Yangtze
Gravel indicates a drainage reorganization from hydrologically closed lakes
to a through-going river system during late Oligocene to early Miocene.
During Paleogene, rift basins were filled by alluvial and
fluvial-lacustrine deposition with restricted flow distance and local
sources. From late Oligocene to early-middle Miocene, the post-rift
subsidence opens a path for the ancient Lower Yangtze River connecting the
Jianghan Basin, North Jiangsu-South Yellow Sea Basin, and East China Sea
Shelf Basin. We attribute the drainage reorganization of the Lower Yangtze
River to be a surficial response to Cenozoic tectonics, particularly the
western Pacific subduction, in southeast China. The deposition of the
widespread, coarse-grained Yangtze Gravel is probably due to the combined
effects of catchment expansion and strong monsoonal climate in East Asia.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35851.1/600887/Sedimentology-geochronology-and-provenance-of-the

Thermotectonic events recorded by U-Pb geochronology and Zr-in-rutile
thermometry of Ti oxides in basement rocks along the P2 fault, eastern
Athabasca Basin, Saskatchewan, Canada

E. Adlakha; K. Hattori

Abstract:
Basement rocks below the Athabasca Basin, Saskatchewan, have been intensely
altered through paleoweathering and multiple hydrothermal events, including
the formation of world-class unconformity-type uranium deposits. Here, we
demonstrate the utility of Ti-oxide thermochronology for identifying
thermotectonic events in these altered rocks leading to uranium
mineralization along basement structures. Rutile grains along the P2 fault,
a major fault in the eastern Athabasca Basin, exhibit 207Pb/ 206Pb ages of ca. 1850−1700 Ma, with a weighted mean of 1757 ± 6
Ma (mean square of weighted deviation [MSWD] = 1.4, n = 116). The
older ages (~1770 Ma) record regional metamorphism reaching a
temperature of 875 °C during the Trans-Hudson orogeny. Pb diffusion
modeling indicates that metamorphic rutile should exhibit cooling ages of
1760−1750 Ma. Rutile grains showing young ages, ~1750 Ma, reflect
isotopic resetting during regional asthenospheric upwelling between 1770
and 1730 Ma related to the emplacement of the Kivalliq igneous suite to the
north. This thermotectonic event (temperature ~550 °C) promoted
hydrothermal activity to produce silicified rocks, i.e., “quartzite,” along
the P2 fault, which later focused mineralizing fluids for unconformity-type
uranium deposits. The young rutile ages also indicate that the basement
rocks remained hot until 1700 Ma, providing the maximum age for the
deposition of the Athabasca sediments. Anatase yields a concordia age of
1569 ± 31 Ma (MSWD = 0.30, n = 5), which is within uncertainty of
the oldest ages for uraninite of the McArthur River deposit. This age
corresponds to the incursion of basinal fluids in the basement along the P2
fault during uranium mineralization.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35820.1/600747/Thermotectonic-events-recorded-by-U-Pb

Superposition of Cretaceous and Cenozoic deformation in northern Tibet:
A far-field response to the tectonic evolution of the Tethyan orogenic
system

Ye Wang; Xuanhua Chen; Yaoyao Zhang; Zheng Yin; Andrew V. Zuza ...

Abstract:
Although the Cenozoic Indo-Asian collision is largely responsible for the
formation of the Tibetan plateau, the role of pre-Cenozoic structures in
controlling the timing and development of Cenozoic deformation remains
poorly understood. In this study we address this problem by conducting an
integrated investigation in the northern foreland of the Tibetan plateau,
north of the Qilian Shan-Nan Shan thrust belt, NW China. The work involves
field mapping, U-Pb detrital-zircon dating of Cretaceous strata in the
northern foreland of the Tibetan plateau, examination of growth-strata
relationships, and construction and restoration of balanced cross sections.
Our field mapping reveals multiple phases of deformation in the area since
the Early Cretaceous, which was expressed by northwest-trending folding and
northwest-striking thrusting that occurred in the early stages of the Early
Cretaceous. The compressional event was followed immediately by extension
and kinematically linked right-slip faulting in the later stage of the
Early Cretaceous. The area underwent gentle northwest-trending folding
since the late Miocene. We estimate the magnitude of the Early Cretaceous
crustal shortening to be ∼35%, which we interpret to have resulted from a
far-field response to the collision between the Lhasa and the Qiangtang
terranes in the south. We suggest that the subsequent extension in the
Early Cretaceous was induced by orogenic collapse. U-Pb dating of detrital
zircons, sourced from Lower Cretaceous sedimentary clasts from the north
and the south, implies that the current foreland region of the Tibetan
plateau was a topographic depression between two highland regions in the
Early Cretaceous. Our work also shows that the Miocene strata in the
foreland region of the northern Tibetan plateau was dominantly sourced from
the north, which implies that the rise of the Qilian Shan did not impact
the sediment dispersal in the current foreland region of the Tibetan
plateau where this study was conducted.

View article:

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35944.1/600737/Superposition-of-Cretaceous-and-Cenozoic

WILMINGTON, Del. (June 29, 2021) - A new report finds that 509,025 (9.17%) public high school students in 24 states experienced homelessness in spring 2019 -- three times the number recognized by the states' education agencies. This under-recognition creates gaps in funding and services needed by this vulnerable population.

Researchers from Nemours Children's Health and the University of Pennsylvania analyzed data from the Centers for Disease Control and Prevention (CDC) for public schools across 24 states and 12 school districts. During spring 2019, more than 9% of public high school students experienced homelessness during a 30-day period in the 24 states. The rate was even higher in the 12 school districts, analyzed separately, where nearly 14% of students reported homelessness.

The report's authors believe the discrepancy between the CDC's data, collected through the Youth Risk Behavior Surveillance System (YRBSS), and the state and local school agency homelessness estimates is likely due to the more comprehensive nature and complex sampling design of the YRBSS. The YRBSS is an anonymous set of surveys conducted in public high schools every two years. The report analyzed data from all states and school districts that opted to ask about student housing and homelessness for the 2019 YRBSS.

Homelessness was more likely among students who were male, LGBT (lesbian, gay, bisexual, transgender), Black/African American, Hispanic/Latinx, or Native American/Hawaiian. Students who experienced homelessness reported higher rates of sexual victimization, physical victimization, and having been bullied. Even when controlling for other risk factors, students who experienced homelessness reported higher rates of severe suicidality, hard drug use, alcohol abuse, risky sexual behavior, and poor grades.

"Even before the COVID-19 pandemic, we saw high rates of homelessness in public high school students and strong links between homelessness and other harmful experiences," said the report's lead author, Danielle Hatchimonji, PhD, of Nemours' Center for Healthcare Delivery Science. "The pandemic's impact on financial and housing stability will have even broader, ripple effects on mental health and academic functioning -- effects that will continue to disproportionately harm students of color."

Dan Treglia, PhD, of the University of Pennsylvania, a co-author on the report and a homelessness expert, explained, "The CDC housing data let us fully recognize the magnitude and depth of youth homelessness in the United States. By acknowledging its extent, we can begin to address the underlying problems and continue to improve systems to identify and serve these students across local school districts and states."

The report makes several recommendations, including prioritizing funding for the federal McKinney-Vento education programs designed to identify and address student homelessness and better sharing of information across service sectors, including housing, education, substance abuse, and mental health. The report also emphasizes the need to reduce poverty and systemic racism and heterosexism, which place students from marginalized groups at higher risk of homelessness.

Hatchimonji added, "That any student experiences homelessness is unacceptable. That homelessness is so much more common among students of color and LGBT students underscores our shared obligation to promote equity and safety, especially for basic needs and human rights."

"We know from other studies that many students who experience homelessness show resilience," said senior author J. J. Cutuli, PhD, of Nemours' Center for Healthcare Delivery Science. "We also know that resilience happens because of relationships and other supports in their lives. Promoting resilience means supporting families, educators, and others in the lives of teens who make sure homelessness does not get in the way."

A study by Stanford University School of Medicine investigators hints that people with COVID-19 may experience milder symptoms if certain cells of their immune systems "remember" previous encounters with seasonal coronaviruses -- the ones that cause about a quarter of the common colds kids get.

These immune cells are better equipped to mobilize quickly against SARS-CoV-2, the coronavirus responsible for COVID-19, if they've already met its gentler cousins, the scientists concluded.

The findings may help explain why some people, particularly children, seem much more resilient than others to infection by SARS-CoV-2, the coronavirus that causes COVID-19. They also might make it possible to predict which people are likely to develop the most severe symptoms of COVID-19.

The immune cells in question, called killer T cells, roam through the blood and lymph, park in tissues and carry out stop-and-frisk operations on resident cells. The study, published online July 1 in Science Immunology, showed that killer T cells taken from the sickest COVID-19 patients exhibit fewer signs of having had previous run-ins with common-cold-causing coronaviruses.

Discussions about immunity to COVID-19 often center on antibodies -- proteins that can latch onto a virus before it's able to infect a vulnerable cell. But antibodies are easily fooled, said Mark Davis, PhD, a professor of microbiology and immunology; director of Stanford's Institute for Immunity, Transplantation and Infection; and a Howard Hughes Medical Institute investigator. Davis is the study's senior author.

"Pathogens evolve quickly and 'learn' to hide their critical features from our antibodies," said Davis, who is also the Burt and Marion Avery Family Professor. But T cells recognize pathogens in a different way, and they're tough to fool.

Our cells all issue real-time reports on their inner state of affairs by routinely sawing up some samples of each protein they've made lately into tiny pieces called peptides and displaying those peptides on their surfaces for inspection by T cells.

When a killer T-cell's receptor notices a peptide on a cell's surface that doesn't belong there -- for example, it's from a protein produced by an invading microorganism -- the T cell declares war. It multiplies furiously, and its numerous offspring -- whose receptors all target the same peptide sequence -- fire up to destroy any cell carrying these telltale-peptide indications of that cell's invasion by a pathogenic microbe.

Some of the original killer T cell's myriad daughter cells enter a more placid state, remaining above the fray. These "memory T cells" exhibit heightened sensitivity and exceptional longevity. They persist in the blood and lymph often for decades, ready to spring into action should they ever cross paths with the peptide that generated the wave of T-cell expansion that begat them. That readiness can save valuable time in stifling a previously encountered virus or a close cousin.

As the pandemic progressed, Davis mused: "A lot of people get very sick or die from COVID-19, while others are walking around not knowing they have it. Why?"

To find out, the study's first author, postdoctoral fellow Vamsee Mallajosyula, PhD, first confirmed that some portions of SARS-CoV-2's sequence are effectively identical to analogous portions of one or more of the four widespread common-cold-causing coronavirus strains. Then he assembled a panel of 24 different peptide sequences that were either unique to proteins made by SARS-CoV-2 or also found on similar proteins made by one or more (or even all) of the seasonal strains.

The researchers analyzed blood samples taken from healthy donors before the COVID-19 pandemic began, meaning they'd never encountered SARS-CoV-2 -- although many presumably had been exposed to common-cold-causing coronavirus strains. The scientists determined the numbers of T cells targeting each peptide represented in the panel.

They found that unexposed individuals' killer T cells targeting SARS-CoV-2 peptides that were shared with other coronaviruses were more likely to have proliferated than killer T cells targeting peptides found only on SARS-CoV-2. The T cells targeting those shared peptide sequences had probably previously encountered one or another gentler coronavirus strain -- and had proliferated in response, Davis said.

Many of these killer T cells were in "memory" mode, he added.

"Memory cells are by far the most active in infectious-disease defense," Davis said. "They're what you want to have in order to fight off a recurring pathogen. They're what vaccines are meant to generate."

Killer T cells whose receptors target peptide sequences unique to SARS-CoV-2 must proliferate over several days to get up to speed after exposure to the virus, Davis said. "That lost time can spell the difference between never even noticing you have a disease and dying from it," he said.

To test this hypothesis, Davis and his colleagues turned to blood samples from COVID-19 patients. They found that, sure enough, COVID-19 patients with milder symptoms tended to have lots of killer-T memory cells directed at peptides SARS-CoV-2 shared with other coronavirus strains. Sicker patients' expanded killer T-cell counts were mainly among those T cells typically targeting peptides unique to SARS-CoV-2 and, thus, probably had started from scratch in their response to the virus.

"It may be that patients with severe COVID-19 hadn't been infected, at least not recently, by gentler coronavirus strains, so they didn't retain effective memory killer T cells," Davis said.

Davis noted that cold-causing seasonal coronavirus strains are rampant among children, who rarely develop severe COVID-19 even though they're just as likely to get infected as adults are.

"Sniffles and sneezes typify the daycare setting," he said, "and coronavirus-caused common colds are a big part of the reason. As many as 80% of kids in the United States get exposed within the first couple of years of life."

Davis and Mallajosyula have filed, through Stanford's Office of Technology Licensing, for patents on the technology used in this study.

Davis is a member of Stanford Bio-X, the Stanford Cardiovascular Institute, the Stanford Maternal and Child Health Research Institute, the Stanford Cancer Institute and the Stanford Wu Tsai Neurosciences Institute.

In a new Editorial, Peter Heeger, Christian Larsen, and Dorry Segev discuss recent evidence - including a recent Science Immunology study by Hector Rincon-Arevalo and colleagues - that points to a diminished immune response to COVID-19 vaccines among organ transplant recipients and others on immunosuppressive drug regimens. The authors note that this presents challenges at both the individual and population levels, since current vaccine protocols may not provide adequate protection to immunosuppressed patients - who could, in turn, become reservoirs for new and dangerous variants of the virus. As such, Heeger, Larsen, and Segev argue that developing vaccination strategies for transplant recipients should be a high priority in the next wave of research focused on fighting COVID-19. "The global scientific response to the SARS-CoV-2 pandemic has been a marvel," the researchers write. "But vulnerable populations remain, and there is no time to rest in the last mile. The full force of scientific effort is still needed to provide immune protection for those who remain at risk from this deadly virus and to control the reservoir to prevent fertile fields for mutations that put the entire population at risk."