Tuesday, June 30, 2020

Study: Why Some Words May Be More Memorable Than Others



Results suggest our brains use internet search engine strategies to remember words and memories of past experiences.

Thousands of words, big and small, are crammed inside our memory banks just waiting to be swiftly withdrawn and strung into sentences. In a recent study of epilepsy patients and healthy volunteers, National Institutes of Health researchers found that our brains may withdraw some common words, like “pig,” “tank,” and “door,” much more often than others, including “cat,” “street,” and “stair.” By combining memory tests, brain wave recordings, and surveys of billions of words published in books, news articles and internet encyclopedia pages, the researchers not only showed how our brains may recall words but also memories of our past experiences.

NIH study suggests our brains may use search engine strategies to remember words and memories of our past experiences. 
Courtesy of Zaghloul lab, NIH/NINDS.

“We found that some words are much more memorable than others. Our results support the idea that our memories are wired into neural networks and that our brains search for these memories, just the way search engines track down information on the internet,” said Weizhen (Zane) Xie, Ph.D., a cognitive psychologist and post-doctoral fellow at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), who led the study published in Nature Human Behaviour. “We hope that these results can be used as a roadmap to evaluate the health of a person’s memory and brain.”

Dr. Xie and his colleagues first spotted these words when they re-analyzed the results of memory tests taken by 30 epilepsy patients who were part of a clinical trial led by Kareem Zaghloul, M.D., Ph.D., a neurosurgeon and senior investigator at NINDS. Dr. Zaghloul’s team tries to help patients whose seizures cannot be controlled by drugs, otherwise known as intractable epilepsy. During the observation period, patients spend several days at the NIH’s Clinical Center with surgically implanted electrodes designed to detect changes in brain activity.

“Our goal is to find and eliminate the source of these harmful and debilitating seizures,” said Dr. Zaghloul. “The monitoring period also provides a rare opportunity to record the neural activity that controls other parts of our lives. With the help of these patient volunteers we have been able to uncover some of the blueprints behind our memories.”

The memory tests were originally designed to assess episodic memories, or the associations – the who, what, where and how details - we make with our past experiences. Alzheimer’s disease and other forms of dementia often destroys the brain’s capacity to make these memories.

Patients were shown pairs of words, such as “hand” and “apple,” from a list of 300 common nouns. A few seconds later they were shown one of the words, for instance “hand,” and asked to remember its pair, “apple.” Dr. Zaghloul’s team had used these tests to study how neural circuits in the brain store and replay memories.

When Dr. Xie and his colleagues re-examined the test results, they found that patients successfully recalled some words more often than others, regardless of the way the words were paired. In fact, of the 300 words used, the top five were on average about seven times more likely to be successfully recalled than the bottom five.

At first, Dr. Zaghloul and the team were surprised by the results and even a bit skeptical. For many years scientists have thought that successful recall of a paired word meant that a person’s brain made a strong connection between the two words during learning and that a similar process may explain why some experiences are more memorable than others. Also, it was hard to explain why words like “tank,” “doll,” and “pond” were remembered more often than frequently used words like “street,” “couch,” and “cloud.”

But any doubts were quickly diminished when the team saw very similar results after 2,623 healthy volunteers took an online version of the word pair test that the team posted on the crowdsourcing website Amazon Mechanical Turk.

“We saw that some things – in this case, words – may be inherently easier for our brains to recall than others,” said Dr. Zaghloul. “These results also provide the strongest evidence to date that what we discovered about how the brain controls memory in this set of patients may also be true for people outside of the study.”

Dr. Xie got the idea for the study at a Christmas party which he attended shortly after his arrival at NIH about two years ago. After spending many years studying how our mental states – our moods, our sleeping habits, and our familiarity with something – can change our memories, Dr. Xie joined Dr. Zaghloul’s team to learn more about the inner-workings of the brain.

“Our memories play a fundamental role in who we are and how our brains work. However, one of the biggest challenges of studying memory is that people often remember the same things in different ways, making it difficult for researchers to compare people’s performances on memory tests,” said Dr. Xie. “For over a century, researchers have called for a unified accounting of this variability. If we can predict what people should remember in advance and understand how our brains do this, then we might be able to develop better ways to evaluate someone’s overall brain health.”

At the party, he met Wilma Bainbridge, Ph.D., an assistant professor in the department of psychology at the University of Chicago, who, at the time was working as a post-doctoral fellow at the NIH’s National Institute of Mental Health (NIMH). She was trying to tackle this same issue by studying whether some things we see are more memorable than others.

For example, in one set of studies of more than 1000 healthy volunteers, Dr. Bainbridge and her colleagues found that some faces are more memorable than others. In these experiments, each volunteer was shown a steady stream of faces and asked to indicate when they recognized one from earlier in the stream.

“Our exciting finding is that there are some images of people or places that are inherently memorable for all people, even though we have each seen different things in our lives” said Dr. Bainbridge. “And if image memorability is so powerful, this means we can know in advance what people are likely to remember or forget.”

Nevertheless, these results were limited to understanding how our brains work when we recognize something we see. At the party, Drs. Xie and Bainbridge wondered whether this idea could be applied to the recall of memories that Dr. Zaghloul’s team had been studying and if so, what would that tell us about how the brain remembers our past experiences?

In this paper, Dr. Xie proposed that the principles from an established theory, known as the Search for Associative Memory (SAM) model, may help explain their initial findings with the epilepsy patients and the healthy controls.

“We thought one way to understand the results of the word pair tests was to apply network theories for how the brain remembers past experiences. In this case, memories of the words we used look like internet or airport terminal maps, with the more memorable words appearing as big, highly trafficked spots connected to smaller spots representing the less memorable words,” said Dr. Xie. “The key to fully understanding this was to figure out what connects the words.”

To address this, the researchers wrote a novel computer modeling program that tested whether certain rules for defining how words are connected can predict the memorability results they saw in the study. The rules were based on language studies which had scanned thousands of sentences from books, news articles, and Wikipedia pages.

Initially, they found that seemingly straightforward ideas for connecting words could not explain their results. For instance, the more memorable words did not simply appear more often in sentences than the less memorable ones. Similarly, they could not find a link between the relative “concreteness” of a word’s definition and its memorability. A word like “moth” was no more memorable than a word that has more abstract meanings, like “chief.”

Instead, their results suggested that the more memorable words were more semantically similar, or more often linked to the meanings of other words used in the English language. This meant, that when the researchers plugged semantic similarity data into the computer model it correctly guessed which words that were memorable from patients and healthy volunteer test. In contrast, this did not happen when they used data on word frequency or concreteness.

Further results supported the idea that the more memorable words represented high trafficked hubs in the brain’s memory networks. The epilepsy patients correctly recalled the memorable words faster than others. Meanwhile, electrical recordings of the patients’ anterior temporal lobe, a language center, showed that their brains replayed the neural signatures behind those words earlier than the less memorable ones. The researchers saw this trend when they looked at both averages of all results and individual trials, which strongly suggested that the more memorable words are easier for the brain to find.

Moreover, both the patients and the healthy volunteers mistakenly called out the more memorable words more frequently than any other words. Overall, these results supported previous studies which suggested that the brain may visit or pass through these highly connected memories, like the way animals forage for food or a computer searches the internet.

“You know when you type words into a search engine, and it shows you a list of highly relevant guesses? It feels like the search engine is reading your mind. Well, our results suggest that the brains of the subjects in this study did something similar when they tried to recall a paired word, and we think that this may happen when we remember many of our past experiences,” said Dr. Xie. “Our results also suggest that the structure of the English language is stored in everyone’s brains and we hope that, one day, it is used to overcome the variability doctors face when trying to evaluate the health of a person’s memory and brain.”

The team is currently exploring ways to incorporate their results and computer model into the development of memory tests for Alzheimer’s disease and other forms of dementia.


Contacts and sources:
NIH/National Institute of Neurological Disorders and Stroke


Publication: Memorability of words in arbitrary verbal associations modulates memory retrieval in the anterior temporal lobe. Weizhen Xie, Wilma A. Bainbridge, Sara K. Inati, Chris I. Baker, Kareem A. Zaghloul. Nature Human Behaviour, 2020; DOI: 10.1038/s41562-020-0901-2

Researchers Identify Multiple Molecules that Shut Down SARS-Cov-2 Polymerase Reaction



SARS-CoV-2, the coronavirus causing the global COVID-19 pandemic, uses a protein called polymerase to replicate its genome inside infected human cells. Terminating the polymerase reaction will stop the growth of the coronavirus, leading to its eradication by the human host’s immune system.

Researchers at Columbia Engineering and the University of Wisconsin-Madison have identified a library of molecules that shut down the SARS-CoV-2 polymerase reaction, a key step that establishes the potential of these molecules as lead compounds to be further modified for the development of COVID-19 therapeutics. Five of these molecules are already FDA-approved for use in the treatment of other viral infections including HIV/AIDS, cytomegalovirus, and hepatitis B. The new study was published on June 18, 2020, in Antiviral Research.

This figure shows that the incorporation of three nucleotide analogues Carbovir-5’-Triphosphate (Car-TP), Entecavir-5’-Triphosphate (Ent-TP), and Ganciclovir-5’-Triphosphate (Gan-TP) by SARS-CoV-2 polymerase terminates the viral polymerase reaction. The reaction products were detected by MALDI-TOF mass spectrometry
Figure of the SARS-Cov-2 Polymerase Reaction
 Credit: Jingyue Ju/Columbia Engineering

The Columbia team initially reasoned that the active triphosphate of the hepatitis C drug sofosbuvir and its derivative could act as a potential inhibitor of the SARS-CoV-2 polymerase based on the analysis of their molecular properties and the replication requirements of both the hepatitis C virus and coronaviruses. Led by Jingyue Ju, Samuel Ruben-Peter G. Viele Professor of Engineering, professor of chemical engineering and pharmacology, and director of the Center for Genome Technology & Biomolecular Engineering at Columbia University, they then collaborated with Robert N. Kirchdoerfer, assistant professor of biochemistry and an expert in the study of coronavirus polymerases at University of Wisconsin-Madison’s Institute for Molecular Virology and the department of biochemistry.

In an earlier set of experiments testing the properties of the polymerase of the coronavirus that causes SARS, the researchers found that the triphosphate of sofosbuvir was able to terminate the virus polymerase reaction. They then demonstrated that sofosbuvir and four other nucleotide analogues (the active triphosphate forms of the HIV inhibitors Alovudine, Zidovudine, Tenofovir alafenamide, and Emtricitabine) also inhibited the SARS-CoV-2 polymerase with different levels of efficiency.

Using the molecular insight gained in these investigations, the team devised a strategy to select 11 nucleotide analogue molecules with a variety of structural and chemical features as potential inhibitors of the polymerases of SARS-CoV and SARS-CoV-2. While all 11 molecules tested displayed incorporation, six exhibited immediate termination of the polymerase reaction, two showed delayed termination, and three did not terminate the polymerase reaction.

Prodrug medications of five of these nucleotide analogues (Cidofovir, Abacavir, Valganciclovir/Ganciclovir, Stavudine, and Entecavir) that terminate the SARS-CoV-2 polymerase reaction are FDA-approved for the treatment of other viral infections and their safety profiles are well established. Once the potency of the drugs to inhibit viral replication in cell culture is demonstrated in future investigations, then the candidate molecules and their modified forms may be evaluated for the development of potential COVID-19 therapies.

"In our efforts to help tackle this global emergency, we are very hopeful that the structural and chemical features of the molecules we identified, in correlation with their inhibitory activity to the SARS-CoV-2 polymerase, can be used as a guide to design and synthesize new compounds for the development of COVID-19 therapeutics,” says Ju. “We are extremely grateful for the generous research support that enabled us to make rapid progress on this project. I am also grateful for the outstanding contributions made by each member of our collaborative research consortium.”





Contacts and sources:
Holly Evart
Columbia University School of Engineering and Applied Science

 Publication:A library of nucleotide analogues terminate RNA synthesis catalyzed by polymerases of coronaviruses that cause SARS and COVID-19.
Steffen Jockusch, Chuanjuan Tao, Xiaoxu Li, Thomas K. Anderson, Minchen Chien, Shiv Kumar, James J. Russo, Robert N. Kirchdoerfer, Jingyue Ju. Antiviral Research, 2020; 180: 104857 DOI: 10.1016/j.antiviral.2020.104857










Potential Mechanism for Lung Injury In COVID-19



An overactive defense response may lead to increased blood clotting, disease severity, and death from COVID-19. A phenomenon called NETosis—in which infection-fighting cells emit a web-like substance to trap invading viruses—is part of an immune response that becomes increasingly hyperactive in people on ventilators and people who die from the disease.

A team led by University of Utah Health and PEEL Therapeutics, in collaboration with Cold Spring Harbor Laboratory and Weill Cornell Medicine, report the findings in a new study published in the journal, Blood.
“This study tells us about a potential mechanism for lung injury in COVID-19 that had not previously been recognized as a possible target for treatment,” says Elizabeth Middleton, M.D., the study’s first author and a critical care specialist at U of U Health.

During COVID-19, infection fighting-cells emit Neutrophil Extracellular Traps (NETs, purple), a sticky web-like substance, to capture invading viruses.
Neutrophil Extracellular Traps (NETs)
Credit; University of Utah Health
The investigation also reports that a naturally occurring protein—originally found in umbilical cord blood—quiets this NET immune response in laboratory experiments, potentially opening new avenues for treatment.

It is estimated that up to 10% of people with COVID-19 become critically ill with respiratory distress. Causes of lung damage are a subject of intense investigation, and increasing evidence demonstrates that increased blood clotting may lead to complications caused by the disease.

Middleton, U of U Health physician-scientists and co-senior authors Christian Con Yost, M.D. and Joshua Schiffman, M.D., and colleagues, took a closer look to see if a specific immune response, called NETosis, could be involved.

As part of an immune response, white blood cells release web-like Neutrophil Extracellular Traps (NETs) to capture and kill pathogens. While typically beneficial, Yost had previously shown that overactive NETs exacerbate certain illnesses. In conditions such as overwhelming infection, NETs can clog blood vessels and lead to inflammatory tissue damage.


A research team including Elizabeth Middleton, MD, found that NETs are part of an immune response that becomes increasingly hyperactive in people on ventilators and who die from COVID-19. 
Credit: Lauren Moulton

To determine whether NETs could be responsible for complications seen in COVID-19, the team examined plasma from 33 patients, along with tracheal aspirates from the lungs. They found that NET activity correlated with disease severity.

Patients on life support and those who died from COVID-19 had significantly more signs of NET activation than patients who were not as sick or who went on to recover. The NET immune response was lower still in healthy people. NET levels also tracked with a marker for blood-oxygen levels, an independent indicator of disease severity.

Similarly, plasma from sick patients was primed to launch the NET response. When examined in laboratory experiments, plasma from COVID-19 patients triggered white blood cells from healthy patients to shoot out 50 times as many NETs as cells exposed to plasma from otherwise healthy adults.

“This study may tell us that NET levels in the blood could potentially help predict disease severity and mortality in COVID-19,” says Yost, a physician-scientist at U of U Health. “Additional information is urgently needed in this pandemic regarding how to know which patient will fare better or worse.” Larger studies will need to be done to determine whether NETs could become a biomarker for COVID-19 severity. “Importantly, we think exaggerated NETs could be a cause of morbidity and mortality in COVID-19,” Yost says.

In support of the idea, collaborators at Cold Spring Harbor Laboratory showed that blood vessels in the lungs of deceased COVID-19 patients were dotted with clumps of NET-producing cells and a critical type of blood cell for clotting, the platelets. Another recent study from U of U Health showed that platelets become hyperactive during the disease. Investigations are now underway to determine whether NETs and platelets increase the risk for blood clotting and other clinical manifestations of COVID-19.

“In COVID-19, thrombosis is a major cause of death. So, our findings tell us that we should focus on understanding more about NETs’ role in clotting in COVID-19,” Mikala Egeblad, Ph.D., a cancer researcher from Cold Spring Harbor Laboratory, says. “Thrombosis is also a major cause of death in late stage cancer, where there also can be elevated NETs in the blood. Therefore, I think that what we learn from COVID-19 will help us with other diseases, including cancer.”

Additional laboratory experiments showed that a small protein found in umbilical cord blood of newborn babies, called neonatal NET Inhibitory Factor (nNIF), quiets the hyperactive NET response in white blood cells treated with COVID-19 patient plasma. This peptide is thought to protect babies from harmful inflammation early in life, explains Schiffman, CEO of PEEL Therapeutics. His company is now evaluating whether the protein could become the basis for a clinical treatment.

“Newborns babies have a natural therapeutic in their blood to protect against these same inflammatory events that we think could be killing COVID-19 patients,” Schiffman says. “This targeted approach to stopping NETs may be more effective with less side effects than some other drugs being tested now in COVID-19 patients that block the entire immune system­­­­.”

NETs associate with small blood clots

Photomicrographs of human lung tissue taken from a patient who died of COVID-19. These are examples of the Neutrophil Extracellular Trap (NET) structures associated with small blood clots. Small blood vessels are outlined with yellow dotted lines, and NETs are identified by the presence of neutrophils (in gray), altered DNA-associated proteins (green). Platelets in the blood clots are in red. Blue color stains DNA in all cells.
Credit: Xue-Yan He and David Ng, Egeblad Lab/Cold Spring Harbor Laboratory.


The research was carried out in collaboration with PEEL Therapeutics, Cold Spring Harbor Laboratory, New York Presbyterian Hospital, and Weill Cornell Medicine and published as “Neutrophil Extracellular Traps (NETs) Contribute to Immunothrombosis in COVID-19 Acute Respiratory Distress Syndrome” on June 29, 2020, in Blood.

Support for the work came from the National Institutes of Health, University of Utah Health’s 3i Initiative, Fonds voor Wetenschappelijk Onderzoek Vlaanderen FWO, Animal Cancer Foundation, Soccer for Hope Foundation, Closer to Cure Foundation, PEEL Therapeutics, Inc., William C. and Joyce C. O’Neill Charitable Trust, the Linartz-Meier Family Foundation, and the U.S. Department of Veterans Affairs.

Disclosure of conflicts of interest: The research was carried out with funding from PEEL Therapeutics, Inc., co-authors Abegglen and Iovino are consultants for and share option holders of PEEL Therapeutics, Inc., Schiffman and co-author Caulin are employed by and share option holders of PEEL Therapeutics, Inc. Yost authors a U.S. patent held by the University of Utah for the use of NET-inhibitory peptides for which PEEL Therapeutics Inc., holds the exclusive license.


Contacts and sources:
Julie Kiefer
University of Utah Health





    

COVID-19 Causes ‘Hyperactivity’ in Blood-Clotting Cells



Changes in blood platelets triggered by COVID-19 could contribute to the onset of heart attacks, strokes, and other serious complications in some patients who have the disease, according to University of Utah Health scientists. The researchers found that inflammatory proteins produced during infection significantly alter the function of platelets, making them “hyperactive” and more prone to form dangerous and potentially deadly blood clots.

This is an image of a blood clot taken using an inverted fluorescent confocal microscope (Zeiss LSM710).Blood  clots are made up of blood cells called platelets and a protein called fibrin which adheres to platelets and forms long strands which eventually join together in the form of a mesh in order to limit blood loss from wound sites
File:3D render of a human blood clot formed in vitro under flow.jpg
Credit:   / Wikimedia Commons

They say better understanding the underlying causes of these changes could possibly lead to treatments that prevent them from happening in COVID-19 patients. Their report appears in Blood, an American Society of Hematology journal.

“Our finding adds an important piece to the jigsaw puzzle that we call COVID-19,” says Robert A. Campbell, Ph.D., senior author of the study and an assistant professor in the Department of Internal Medicine. “We found that inflammation and systemic changes, due to the infection, are influencing how platelets function, leading them to aggregate faster, which could explain why we are seeing increased numbers of blood clots in COVID patients.”

Emerging evidence suggests COVID-19 is associated with an increased risk of blood clotting, which can lead to cardiovascular problems and organ failure in some patients, particularly among those with underlying medical problems such as diabetes, obesity, or high blood pressure.
"Our finding adds an important piece to the jigsaw puzzle that we call COVID-19."Robert A. Campbell, Ph.D.

To find out what might be going on, the researchers studied 41 COVID-19 patients hospitalized at University of Utah Hospital in Salt Lake City. Seventeen of these patients were in the ICU, including nine who were on ventilators. They compared blood from these patients with samples taken from healthy individuals who were matched for age and sex.


Robert A. Campbell, Ph.D., and colleagues found that inflammatory proteins produced during COVID-19 infection significantly alter the function of platelets.
 Photo courtesy of Robert A. Campbell

Using differential gene analysis, the researchers found that SARS-CoV-2, the virus that causes COVID-19, appears to trigger genetic changes in platelets. In laboratory studies, they studied platelet aggregation, an important component of blood clot formation, and observed COVID-19 platelets aggregated more readily. They also noted that these changes significantly altered how platelets interacted with the immune system, likely contributing to inflammation of the respiratory tract that may, in turn, result in more severe lung injury.

Surprisingly, Campbell and his colleagues didn’t detect evidence of the virus in the vast majority of platelets, suggesting that it could be promoting the genetic changes within these cells indirectly.

One possible mechanism is inflammation, according to Bhanu Kanth Manne, Ph.D., one of the study’s lead authors and a research associate with the University of Utah Molecular Medicine Program (U2M2). In theory, inflammation caused by COVID-19 could affect megakaryocytes, the cells that produce platelets. As a result, critical genetic alterations are passed down from megakaryocytes to the platelets, which, in turn, make them hyperactive.

In test tube studies, the researchers found that pre-treating platelets from SARS-CoV-2 infected patients with aspirin did prevent this hyperactivity. These findings suggest aspirin may improve outcomes; however, this will need further study in clinical trials. For now, Campbell warns against using aspirin to treat COVID-19 unless recommended by your physician.

In the meantime, the researchers are beginning to look for other possible treatments.

“There are genetic processes that we can target that would prevent platelets from being changed,” Campbell says. “If we can figure out how COVID-19 is interacting with megakaryocytes or platelets, then we might be able to block that interaction and reduce someone’s risk of developing a blood clot.”




Contacts and sources:
Doug Dollemore
University of Utah Health


Publication: Platelet Gene Expression and Function in COVID-19 Patients.Robert A. Campbell, Matthew T. Rondina, Christian Con Yost, Andrew S. Weyrich, Mark J. Cody, Li Guo, Neal D. Tolley, Aaron C. Petrey, Chris J. Stubben, Jesse W Rowley, Irina Portier, Elizabeth A Middleton, Frederik Denorme, Bhanu Kanth Manne. Blood, 2020; DOI: 10.1182/blood.2020007214



    

South Pole Warming Three Times Faster Than Global Average for 30 Years



The South Pole has been warming at more than three times the global average over the past 30 years, according to research led by Ohio University professor Ryan Fogt and OHIO alumnus Kyle Clem.

Fogt, professor of meteorology and director of the Scalia Laboratory for Atmospheric Analysis, and Clem coauthored a paper with an international team of scientists published in the journal Nature Climate Change on the findings. According to the study, this warming period was mainly driven by natural tropical climate variability and was likely intensified by increases in greenhouse gas.

Fogt South Pole
Credit: Ohio University

Clem, a current postdoctoral research fellow in climate science at Victoria University of Wellington in New Zealand, is the lead author of the study and studied under Fogt for both his bachelor’s and master’s degrees at Ohio University.

“I've had a passion for understanding the weather and fascination of its power and unpredictability as far back as I can remember,” Clem said. “Working with Ryan I learned all about Antarctic and Southern Hemisphere climate, specifically how West Antarctica was warming and its ice sheet was thinning and contributing to global sea level rise. I also learned that Antarctica experiences some of the most extreme weather and variability on the planet, and due to its remote location we actually know very little about the continent, so there are constant surprises and new things to learn about Antarctica every year.”

The Antarctic climate exhibits some of the largest ranges in temperature during the course of the year, and some of the largest temperature trends on the planet, with strong regional contrasts. Most of West Antarctica and the Antarctic Peninsula experienced warming and ice-sheet thinning during the late 20th century. By contrast, the South Pole — located in the remote and high-altitude continental interior — cooled until the 1980s and has since warmed substantially. These trends are affected by natural and anthropogenic climate change, but the individual contribution of each factor is not well understood.

Clem and his team analyzed weather station data at the South Pole, as well as climate models to examine the warming in the Antarctic interior. They found that between 1989 and 2018, the South Pole had warmed by about 1.8 degrees Celsius over the past 30 years at a rate of +0.6 degrees Celcius per decade – three times the global average.

The study also found that the strong warming over the Antarctic interior in the last 30 years was mainly driven by the tropics, especially warm ocean temperatures in the western tropical Pacific Ocean that changed the winds in the South Atlantic near Antarctica and increased the delivery of warm air to the South Pole. They suggest these atmospheric changes along Antarctica’s coast are an important mechanism driving climate anomalies in its interior.

Clem and Fogt argue that these warming trends were unlikely the result of natural climate change alone, emphasizing the effects of added anthropogenic warming on top of the large tropical climate signal on Antarctic climate have worked in tandem to make this one of the strongest warming trends worldwide.

“From the very beginning, Kyle and I worked very well together and were able to accomplish more as a team than we were individually,” Fogt said. “We have published every year together since 2013, with one of our continuing collaborations being the annual State of the Climate reports. Our work on this project together each year ultimately led to this publication documenting the warming at the South Pole, however, most importantly for me, apart from being a fantastic scientist and collaborator, my family and I are both honored to consider Kyle one of our closest friends.”

Contacts and sources:
Ohio University
Publication: Record warming at the South Pole during the past three decades Kyle R. Clem, Ryan L. Fogt, John Turner, Benjamin R. Lintner, Gareth J. Marshall, James R. Miller, James A. Renwick. . Nature Climate Change, 2020; DOI: 10.1038/s41558-020-0815-z


    

Cosmic Mystery: ESO Telescope Captures the Disappearance of a Massive Star

Image of the Kinman Dwarf galaxy, also known as PHL 293B, taken with the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 in 2011, before the disappearance of the massive star. Located some 75 million light-years away, the galaxy is too far away for astronomers to clearly resolve its individual stars, but in observations done between 2001 and 2011, they detected the signatures of the massive star. These signatures were not present in more recent data.
Hubble image of the Kinman Dwarf galaxy
Credit: NASA, ESA/Hubble, J. Andrews (U. Arizona)

Using the European Southern Observatory’s Very Large Telescope (VLT), astronomers have discovered the absence of an unstable massive star in a dwarf galaxy. Scientists think this could indicate that the star became less bright and partially obscured by dust. An alternative explanation is that the star collapsed into a black hole without producing a supernova. “If true,” says team leader and PhD student Andrew Allan of Trinity College Dublin, Ireland, “this would be the first direct detection of such a monster star ending its life in this manner.”

This illustration shows what the luminous blue variable star in the Kinman Dwarf galaxy could have looked like before its mysterious disappearance.
Credit: ESO/L. Calçada

Between 2001 and 2011, various teams of astronomers studied the mysterious massive star, located in the Kinman Dwarf galaxy, and their observations indicated it was in a late stage of its evolution. Allan and his collaborators in Ireland, Chile and the US wanted to find out more about how very massive stars end their lives, and the object in the Kinman Dwarf seemed like the perfect target. But when they pointed ESO’s VLT to the distant galaxy in 2019, they could no longer find the telltale signatures of the star. “Instead, we were surprised to find out that the star had disappeared!” says Allan, who led a study of the star published today in Monthly Notices of the Royal Astronomical Society.

Located some 75 million light-years away in the constellation of Aquarius, the Kinman Dwarf galaxy is too far away for astronomers to see its individual stars, but they can detect the signatures of some of them. From 2001 to 2011, the light from the galaxy consistently showed evidence that it hosted a ‘luminous blue variable’ star some 2.5 million times brighter than the Sun. Stars of this type are unstable, showing occasional dramatic shifts in their spectra and brightness. Even with those shifts, luminous blue variables leave specific traces scientists can identify, but they were absent from the data the team collected in 2019, leaving them to wonder what had happened to the star. “It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion,” says Allan.

This animation shows what the luminous blue variable star in the Kinman Dwarf galaxy could have looked like before its mysterious disappearance.

Credit: ESO/L. Calçada

The group first turned the ESPRESSO instrument toward the star in August 2019, using the VLT’s four 8-metre telescopes simultaneously. But they were unable to find the signs that previously pointed to the presence of the luminous star. A few months later, the group tried the X-shooter instrument, also on ESO’s VLT, and again found no traces of the star.

“We may have detected one of the most massive stars of the local Universe going gently into the night,” says team-member Jose Groh, also of Trinity College Dublin. “Our discovery would not have been made without using the powerful ESO 8-metre telescopes, their unique instrumentation, and the prompt access to those capabilities following the recent agreement of Ireland to join ESO.” Ireland became an ESO member state in September 2018.

The team then turned to older data collected using X-shooter and the UVES instrument on ESO’s VLT, located in the Chilean Atacama Desert, and telescopes elsewhere.“The ESO Science Archive Facility enabled us to find and use data of the same object obtained in 2002 and 2009,” says Andrea Mehner, a staff astronomer at ESO in Chile who participated in the study. “The comparison of the 2002 high-resolution UVES spectra with our observations obtained in 2019 with ESO's newest high-resolution spectrograph ESPRESSO was especially revealing, from both an astronomical and an instrumentation point of view.”

This video starts by showing a wide-field view of a region of the sky in the constellation of Aquarius. It then zooms in to show the Kinman Dwarf galaxy, where a mysterious luminous blue variable star disappeared. The end of the video shows an artistic animation of what the star could have looked like before it disappeared.

Credit: ESO/L. Calçada, Digitized Sky Survey 2, N. Risinger (skysurvey.org), NASA, ESA/Hubble, J. Andrews (U. Arizona) Music: Konstantino Polizois

The old data indicated that the star in the Kinman Dwarf could have been undergoing a strong outburst period that likely ended sometime after 2011. Luminous blue variable stars such as this one are prone to experiencing giant outbursts over the course of their life, causing the stars’ rate of mass loss to spike and their luminosity to increase dramatically.

Based on their observations and models, the astronomers have suggested two explanations for the star’s disappearance and lack of a supernova, related to this possible outburst. The outburst may have resulted in the luminous blue variable being transformed into a less luminous star, which could also be partly hidden by dust. Alternatively, the team says the star may have collapsed into a black hole, without producing a supernova explosion. This would be a rare event: our current understanding of how massive stars die points to most of them ending their lives in a supernova.

Future studies are needed to confirm what fate befell this star. Planned to begin operations in 2025, ESO’s Extremely Large Telescope (ELT) will be capable of resolving stars in distant galaxies such as the Kinman Dwarf, helping to solve cosmic mysteries such as this one.





Contacts and sources:
Andrew Allan
Trinity College Dublin

Jose H. Groh
Trinity College Dublin

Andrea Mehner
European Southern Observatory
Bárbara Ferreira
ESO 

Publication: The possible disappearance of a massive star in the low-metallicity galaxy PHL 293B. Jennifer E Andrews, Eoin J Farrell, Ioana Boian, Nathan Smith, Andrea Mehner, Jose H Groh, Andrew P Allan. Monthly Notices of the Royal Astronomical Society, 2020; 496 (2): 1902 DOI: 10.1093/mnras/staa1629



    

New Study Showing Global Warming Has Upended 6,500 Years Of Cooling



In the past 150 years, global warming has more than undone the global cooling that occurred over the past six millennia, according to a major study published June 30 in Nature Research’s Scientific Data, “Holocene global mean surface temperature, a multi-method reconstruction approach.” The findings show the millennial-scale global cooling began approximately 6,500 years ago when the long-term average global temperature topped out at about 0.7 degrees C warmer than the mid-19th century. Since then, accelerating greenhouse gas emissions have contributed to global average temperatures that are now surpassing 1 degree C above the mid-19th century.

Four researchers of Northern Arizona University’s School of Earth and Sustainability (SES) led the study, with Regents’ Professor Darrell Kaufman as lead author and associate professor Nicholas McKay as co-author, along with assistant research professors Cody Routson and Michael Erb. The team worked in collaboration with scientists from research institutions throughout the world to reconstruct the global average temperature over the Holocene Epoch—the period following the Ice Age, beginning about 12,000 years ago.

“Before global warming, there was global cooling,” Kaufman said. “Previous work has shown convincingly that the world naturally and slowly cooled for at least 1,000 years prior to the middle of the 19th century, when the global average temperature reversed course along with the build-up of greenhouse gases. This study, based on a major new compilation of previously published paleoclimate data, combined with new statistical analyses, shows more confidently than ever that the millennial-scale global cooling began approximately 6,500 years ago.”

Earlier this year, an international group of 93 paleoclimate scientists from 23 countries—also led by Kaufman, McKay, Routson and Erb—published the most comprehensive set of paleoclimate data ever compiled for the past 12,000 years, compressing 1,319 data records based on samples taken from 679 sites globally. At each site, researchers analyzed ecological, geochemical and biophysical evidence from both marine and terrestrial archives, such as lake deposits, marine sediments, peat and glacier ice, to infer past temperature changes. Countless scientists working around the world over many decades conducted the basic research contributing to the global database.

“The rate of cooling that followed the peak warmth was subtle, only around 0.1°C per 1,000 years. This cooling seems to be driven by slow cycles in the Earth’s orbit, which reduced the amount of summer sunlight in the Northern Hemisphere, culminating in the ‘Little Ice Age’ of recent centuries,” said Erb, who analyzed the temperature reconstructions.

Image credit: Victor O. Leshyk, Northern Arizona University

Since the mid-19th century, global warming has climbed to about 1°C, suggesting that the global average temperature of the last decade (2010-2019) was warmer than anytime during the present post-glacial period.

McKay, who developed some of the statistical approaches to synthesizing data from around the world, notes that individual decades are not resolved in the 12,000-year-long temperature reconstruction, making it difficult to compare it with any recent decade.

“On the other hand, this past decade was likely cooler than what the average temperatures will be for the rest of this century and beyond, which are very likely to continue to exceed 1°C above pre-industrial temperatures,” McKay said.

“It’s possible that the last time the sustained average global temperature was 1°C above the 19th century was prior to the last Ice Age, back around 125,000 years ago when sea level was around 20 feet higher than today,” Kaufman said.

Read more about an earlier version of the database to link Arctic warming to a reduction in precipitation at mid latitudes.

“Investigating the patterns of natural temperature changes over space and time helps us understand and quantify the processes that cause climate to change, which is important as we prepare for the full range of future climate changes due to both human and natural causes,” Routson said. “Our future climate will largely depend on the influence of human factors, especially the build-up of greenhouse gases. However, future climate will also be influenced by natural factors, and it will be complicated by the natural variability within the climate system. Future projections of climate change will be improved by better accounting for both anthropogenic and natural factors.”

The reconstruction of past global temperature is the outgrowth of several NAU research projects aimed at understanding the causes and effects of natural climate variability, work that was funded through more than $1.2 million in grants from the National Science Foundation. The team was recently awarded another $678,000 in grants from the NSF for related work extending through 2023.



Contacts and sources:
Kerry Bennett
Northern Arizona University

Publication: Holocene global mean surface temperature, a multi-method reconstruction approach. Darrell Kaufman, Nicholas McKay, Cody Routson, Michael Erb, Christoph Dätwyler, Philipp S. Sommer, Oliver Heiri, Basil Davis. Scientific Data, 2020; 7 (1) DOI: 10.1038/s41597-020-0530-7


    

Chicxulub Asteroid or Massive Volcanic Eruptions: Dinosaur Killer Named



Modelling of the Chicxulub asteroid impact 66 million years ago shows it created a world largely unsuitable for dinosaurs to live in.

The asteroid, which struck the Earth off the coast of Mexico at the end of the Cretaceous era 66 million years ago, has long been believed to be the cause of the demise of all dinosaur species except those that became birds.

Top image (Ankylosaurus magniventris drinking as the asteroid strikes)
Dinosaur drinking with an asteroid in the background
Credit: Fabio Manucci

However, some researchers have suggested that tens of thousands of years of large volcanic eruptions may have been the actual cause of the extinction event, which also killed off almost 75% of life on Earth.

Now, a research team from Imperial College London, the University of Bristol and University College London has shown that only the asteroid impact could have created conditions that were unfavourable for dinosaurs across the globe.

They also show that the massive volcanism could also have helped life recover from the asteroid strike in the long term. Their results are published today in Proceedings of the National Academy of Sciences.

The only plausible explanation

Lead researcher Dr Alessandro Chiarenza, who conducted this work whilst studying for his PhD in the Department of Earth Science and Engineering at Imperial, said: “We show that the asteroid caused an impact winter for decades, and that these environmental effects decimated suitable environments for dinosaurs. In contrast, the effects of the intense volcanic eruptions were not strong enough to substantially disrupt global ecosystems.

“Our study confirms, for the first time quantitatively, that the only plausible explanation for the extinction is the impact winter that eradicated dinosaur habitats worldwide.”

 Extinction simulation (gif)

via GIPHY   Credit: : Alfio Alessandro Chiarenza 

The asteroid impact left no suitable habitats for dinosaurs, whereas the volcanic activity (Deccan pulse) left some habitable areas.

The asteroid strike would have released particles and gases high into the atmosphere, blocking out the Sun for years and causing permanent winters. Volcanic eruptions also produce particles and gases with Sun-blocking effects, and around the time of the mass extinction there were tens of thousands of years of eruptions at the Deccan Traps, in present-day India.

To determine which factor, the asteroid or the volcanism, had more climate-changing power, researchers have traditionally used geological markers of climate and powerful mathematical models. In the new paper, the team combined these methods with information about what kinds of environmental factors, such as rainfall and temperature, each species of dinosaur needed to thrive.

They were then able to map where these conditions would still exist in a world after either an asteroid strike or massive volcanism. They found that only the asteroid strike wiped out all potential dinosaur habitats, while volcanism left some viable regions around the equator.
Helping new life evolve

Co-lead author of the study Dr Alex Farnsworth, from the University of Bristol, said: “Instead of only using the geologic record to model the effect on climate that the asteroid or volcanism might have caused worldwide, we pushed this approach a step forward, adding an ecological dimension to the study to reveal how these climatic fluctuations severely affected ecosystems.”

Impact from space
 Credit: Gabriele Chiarenza

Co-author Dr Philip Mannion, from University College London, added: “In this study we add a modelling approach to key geological and climate data that shows the devastating effect of the asteroid impact on global habitats. Essentially, it produces a blue screen of death for dinosaurs.”

Although volcanoes release Sun-blocking gases and particles, they also release carbon dioxide, a greenhouse gas. In the short term after an eruption, the Sun-blockers have a larger effect, causing a ‘volcanic winter’. However, in the longer term these particles and gases drop out of the atmosphere, while carbon dioxide stays around and builds up, warming the planet.

After the initial drastic global winter caused by the asteroid, the team’s model suggests that in the longer term, volcanic warming could have helped restore many habitats, helping new life that evolved after the disaster to thrive.

Dr Chiarenza said: “We provide new evidence to suggest that the volcanic eruptions happening around the same time might have reduced the effects on the environment caused by the impact, particularly in quickening the rise of temperatures after the impact winter. This volcanic-induced warming helped boost the survival and recovery of the animals and plants that made through the extinction, with many groups expanding in its immediate aftermath, including birds and mammals.”




Contacts and sources:
Hayley Dunning
Imperial College London


Publication: ‘Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction’ by Alfio Alessandro Chiarenza, Alexander Farnsworth, Philip D. Mannion, Daniel J. Lunt, Paul Valdes, Joanna V. Morgan, Peter A. Allison is published in Proceedings of the National Academy of Sciences.



    

Monday, June 29, 2020

Recently Banned in France: Commons Food Additive Inflames Color in Mice



A common food additive, recently banned in France but allowed in the U.S. and many other countries, was found to significantly alter gut microbiota in mice, causing inflammation in the colon and changes in protein expression in the liver, according to research led by a University of Massachusetts Amherst food scientist.

Titanium dioxide (TiO2), an insoluble white powder, is used extensively in many commercial products, including paint, cosmetics, plastics, paper, and food, as an anticaking or whitening agent. It is produced and used in the workplace in varying particle-size fractions, including fine and ultrafine sizes. The number of U.S. workers currently exposed to TiO2 dust is unknown.

“I think our results have a lot of implications in the food industry and on human health and nutrition,” says lead author Hang Xiao, professor and Clydesdale Scholar of Food Science. “The study confirmed a strong linkage between foodborne titanium dioxide nanoparticles (TiO2 NPs) and adverse health effects.”

Titanium dioxide nanoparticles
File:TEM-image-of-Degussa-P25-TiO-sub2sub-nanoparticles.jpg
Credit: Kun-Ching Cho et. al. "Synthesis and Characterization of a Photoelectrode with a Novel 3D Structure for Dye-Sensitized Solar Cells", International Journal of Photoenergy doi:10.1155/2014/913108 / Wikimedia Commons

Along with colleagues at UMass Amherst and in China, Xiao published the research in Small, a weekly, peer-reviewed, interdisciplinary journal that covers nanotechnology.

Gut microbiota, which refers to the diverse and complex community of microorganisms in the gut, plays a vital role in human health. An imbalance of gut microbiota has been associated with a range of health issues, including inflammatory bowel disease, obesity and cardiovascular disease.

Human exposure to foodborne TiO2 NPs comes primarily from a food additive known as E171, which is made up of different-size particles of TiO2, including one-third or more that are nanoscale. E171, which makes products look whiter and more opaque, is found in such food as desserts, candy, beverages and gum. E171 exposure is two to four times higher in U.S. children than in adults, one study has found.

Smaller than 100 nanometers, foodborne nanoscale particles may have unique physiological properties that cause concern. “The bigger particles won’t be absorbed easily, but the smaller ones could get into the tissues and accumulate somewhere,” Xiao says.

In their study, Xiao and his team fed either E171 or TiO2 NPs to two populations of mice as part of their daily diet. One population was fed a high-fat diet similar to that of many Americans, two-thirds of whom are obese or overweight; the other group of mice was fed a low-fat diet. The mice fed a high-fat diet eventually became obese, while the mice on the low-fat diet did not.

“In both the non-obese mice and obese mice, the gut microbiota was disturbed by both E171 and TiO2 NPs,” Xiao says. “The nanosized particles caused more negative changes in both groups of mice.” Moreover, the obese mice were more susceptible to the adverse effects of TiO2 NPs, causing more damage in obese mice than in non-obese ones.

The researchers found TiO2 NPs decreased cecal levels of short-chain fatty acids, which are essential for colon health, and increased pro-inflammatory immune cells and cytokines in the colon, indicating an inflammatory state.

To evaluate the direct health impact of gut microbiota disrupted by TiO2 NP, Xiao and colleagues conducted a fecal transplant study. They gave mice antibiotics to clear out their original gut microbiota and then transplanted fecal bacteria from the TiO2 NP-treated mice to the antibiotic-treated mice. “The results support our hypothesis that including TiO2 NPs in the diet disrupts the homeostasis of the gut microbiota,” Xiao says, “which in turn leads to colonic inflammation in the mice.

The study also measured levels of TiO2 in human stool samples, finding a wide range. Xiao says further research is needed to determine the health effects of long-term – such as life-long and multigenerational – exposure to TiO2 NPs.

Contacts and sources:
 Hang Xiao
University of Massachusetts Amherst

Publication: Foodborne Titanium Dioxide Nanoparticles Induce Stronger Adverse Effects in Obese Mice than Non‐Obese Mice: Gut Microbiota Dysbiosis, Colonic Inflammation, and Proteome Alterations. Xiaoqiong Cao, Yanhui Han, Min Gu, Hengjun Du, Mingyue Song, Xiaoai Zhu, Gaoxing Ma, Che Pan, Weicang Wang, Ermin Zhao, Timothy Goulette, Biao Yuan, Guodong Zhang, Hang Xiao. Small, 2020; 2001858 DOI: 10.1002/smll.202001858


    

Common Cold Virus Can Cause Heart Attacks

Patrick Calhoun (left) and mentor James Smyth, an associate professor at the Fralin Biomedical Research Institute at VTC, conducted first-of-its-kind research applying human adenovirus to induced pluripotent stem cell derived-cardiomyocytes – human skin cells converted to heart cells -- that determined the virus disrupts the electrical system that keeps the heart beating regularly, sometimes causing sudden cardiac death.
Patrick Calhoun and James Smyth in the Smyth Lab at the Fralin Biomedical Research Institute.
Credit: Virginia Tech

Virginia Tech researchers studying how a usually benign virus attacks the human heart with sometimes fatal consequences determined that the virus disrupts the heart’s electrical system – and with dual impacts not previously recognized.

Patrick Calhoun, a postdoctoral associate, and his mentor, James Smyth, an associate professor at the Fralin Biomedical Research Institute at VTC, found that adenovirus not only uncouples electrical signaling pathways in the heart, but it also impairs the cells’ ability to make new communication channels.

Researchers made their findings via first-of-their-kind experiments to observe adenovirus effects on human heart cells in a culture dish.

“This is the first time we’re putting this human virus on human heart cells to see what it does in the context of infected heart muscle cells,” Smyth said. “That’s the real power of this.”

The study was published June 2 in The FASEB Journal, an international publication of the Federation of American Societies for Experimental Biology.

The discovery may increase understanding of arrythmias, which are problems of the heart’s electrical signaling that can lead to arrest of the heart’s coordinated beating and even sudden cardiac death. The research in the Smyth laboratory focuses on ventricular arrhythmia that are potentially the most dangerous, but such electrical disturbances can affect all chambers of the heart. Atrial fibrillation, the most common type of arrhythmia, affects more than 2 million people in the United States, according to the National Heart, Lung, and Blood Institute of the National Institutes of Health.

Heart muscle cells communicate with each other via channels called gap junctions. Formed by proteins called connexins, gap junctions create a bridge between two cells for sharing electrical signals that enable heart muscle cells to beat in concert – but gap junctions can also alert neighboring cells they are under attack by a virus.

Previous work in Smyth’s lab found that acute infections caused by adenovirus reduced levels of a key gap junction protein, connexin43.

Adenovirus, which typically can cause a common cold, has a far more dangerous impact if it reaches the heart. When the virus commandeers gap junctions, it can slow production of connexin43, disturbing the electrical system that keeps a heart beating properly, leading to arrythmias and sometimes sudden cardiac death.

A transmission electron micrograph captures new adenovirus particles assembling in honeycomb-shaped arrays in an infected cell in one of the Smyth lab’s experiments. The viral proteins assemble in paracrystalline groupings in the nucleus. “The arrays are really amazing and man-made looking,” Smyth said. “Viral progeny are formed in these ‘factories.’”
Credit: Virginia Tech

Calhoun performed specific experiments that confirmed that the virus can effectively hijack the system that heart muscle cells use to communicate. Similar research is often performed using mouse models, but previously scientists lacked an effective model for adenovirus and the human heart.

Calhoun innovated a diagnostic technique using induced pluripotent stem cell derived-cardiomyocytes – human skin cells converted to heart cells. He applied adenovirus to those and watched what happened.

He saw what he expected – the virus took over the gap junctions for its own replication purposes – but he saw something else he didn’t expect.

“I realized there were two distinct processes going on here, with the virus giving a double hit to the cell’s ability to communicate with its neighbors” Calhoun said. “Firstly, it was rapidly closing existing channels, and secondly it was shutting down the cells’ ability to make new ones.”

Smyth and Calhoun took particular interest in how the virus halted connexin43 creation and gap junction formation. The virus switched a protein pathway classically described as making new connexin to suppressing connexin instead. Smyth sees promise in learning more about how the virus made that change.

“We might learn something very new about the molecular biology there that’s causing that switch,” said Smyth, who is also an associate professor of biological sciences in the Virginia Tech College of Science and of basic science education in the Virginia Tech Carilion School of Medicine.

“The research has some limitations for extending the findings to the living heart because it’s done in vitro – in a dish outside of the human body – but still has tremendous value,” Smyth said. "Fundamental studies provide the footing for the translational research that discovers therapeutics and diagnostic methods that improve people’s health.

“They give us pointers and clues as to what to look for,” Smyth continued.

“This research goes beyond viral infection with the hope that we can generate new therapeutic interventions for diseased hearts,” Calhoun said. “We’re essentially learning from adenovirus to find the most efficient ways to stop, rather than cause, arrhythmias.”

Calhoun’s research formed a significant part of his recently defended doctoral dissertation. It’s complemented by the work of Rachel Padget, another researcher in Smyth’s lab who was recently awarded a National Institutes of Health fellowship to develop a first-ever mouse model to investigate how adenovirus attacks the heart.

Calhoun, originally from Niceville, Florida, has been mentored by Smyth for more than five years. A U.S. Army veteran, Calhoun began his academic career at Virginia Western Community College in Roanoke, Virginia, before transferring to Virginia Tech.

This month he’ll begin work as a postdoctoral fellow at Johns Hopkins School of Medicine in Baltimore, where he’ll continue his study of cardiac health.

Smyth, an investigator in the Fralin Biomedical Research Institute’s Center for Heart and Reparative Medicine Research, is the senior author on the paper. Calhoun’s research was funded by an American Heart Association grant awarded in 2018.



Contacts and sources:
Matt Chittum
Virginia Tech

Publication: Adenovirus targets transcriptional and posttranslational mechanisms to limit gap junction function Patrick J. Calhoun, Allen V. Phan, Jordan D. Taylor, Carissa C. James, Rachel L. Padget, Michael J. Zeitz, James W. Smyth. . FASEB Journal, 2020 DOI: 10.1096/fj.202000667R


    

Ancient Maya Reservoirs Contained Toxic pollution



Reservoirs in the heart of an ancient Maya city were so polluted with mercury and blue-green algae that the water likely was undrinkable.


Researchers from the University of Cincinnati found toxic levels of pollution in four central reservoirs in Tikal, an ancient Maya city that dates back to the third century B.C. in what is now northern Guatemala.

UC’s findings suggest droughts in the ninth century likely contributed to the depopulation and eventual abandonment of the city.

“The conversion of Tikal’s central reservoirs from life-sustaining to sickness-inducing places would have both practically and symbolically helped to bring about the abandonment of this magnificent city,” the study concluded.

The ancient Maya city of Tikal in northern Guatemala thrived from the second to ninth centuries. UC researchers found evidence of water pollution that help explain why the city was abandoned.
 Photo/Jimmy Baum/Unsplash

A geochemical analysis found that two reservoirs nearest the city palace and temple contained extremely high and toxic levels of mercury that UC researchers traced back to a pigment the Maya used to adorn buildings, clayware and other goods. During rainstorms, mercury in the pigment leached into the reservoirs where it settled in layers of sediment over the years.

The study was published in the Nature journal Scientific Reports.

Archaeologists and anthropologists have been trying to figure out what happened to the Maya for 100 years.

Unravelling a mystery


UC’s diverse team was composed of anthropologists, geographers, botanists, biologists and chemists. They examined layers of sediment dating back to the ninth century when Tikal was a flourishing city.

Previously, UC researchers found that the soils around Tikal during the ninth century were extremely fertile and traced the source to frequent volcanic eruptions that enriched the soil of the Yucatan Peninsula.

“Archaeologists and anthropologists have been trying to figure out what happened to the Maya for 100 years,” said David Lentz, a UC professor of biological sciences and lead author of the study.

UC graduate student Brian Lane climbs out of the Perdido Reservoir.
  Photo/Nicholas Dunning



For the latest study, UC researchers sampled sediment at 10 reservoirs within the city and conducted an analysis on ancient DNA found in the stratified sediment of four of them.

Sediment from the reservoirs nearest Tikal’s central temple and palace showed evidence of cyanobacteria. Consuming this water, particularly during droughts, would have made people sick even if the water were boiled, Lentz said.

“We found two types of blue-green algae that produce toxic chemicals. The bad thing about these is they’re resistant to boiling. It made water in these reservoirs toxic to drink,” Lentz said.

UC researchers said it is possible but unlikely the Maya used these reservoirs for drinking, cooking or irrigation.

“The water would have looked nasty. It would have tasted nasty,” said Kenneth Tankersley, an associate professor of anthropology in UC’s College of Arts and Sciences. “There would have been these big blue-green algae blooms. Nobody would have wanted to drink that water.”

UC biologist David Lents said archaeologist and anthropologists have been trying for decades to understand why ancient Maya cities such as Tikal were abandoned. UC's research is contributing to the answer
 Photo/Joseph Fuqua/UC Creative + Brand

Precious resources

Researchers found lower but still toxic levels of mercury in sediments from more distant reservoirs called Perdido and Corriental, which also would have provided drinking water for city residents during the ninth century.

The towering city of Tikal rises above the rainforest

. Photo/David Lentz

Today, Tikal is a national park and a UNESCO World Heritage site. Researchers believe a combination of economic, political and social factors prompted people to leave the city and its adjacent farms. But the climate no doubt played a role, too, Lentz said.

“They have a prolonged dry season. For part of the year, it’s rainy and wet. The rest of the year, it’s really dry with almost no rainfall. So they had a problem finding water,” Lentz said.

Co-author Trinity Hamilton, now an assistant professor of biology at the University of Minnesota, worked on the analysis of ancient DNA from cyanobacteria that sank to the reservoir bottom and was buried by centuries of accumulated sediment.

“Typically, when we see a lot of cyanobacteria in freshwater, we think of harmful algal blooms that impact water quality,” Hamilton said.

UC geography professor Nicholas Dunning has conducted several research projects on the ancient Maya at places such as Tikal.
Photo/Joseph Fuqua/UC Creative + Brand



Reservoirs near the temple and palace likely would have been impressive landmarks, much like the reflecting pool at the National Mall is today.

“It would have been a magnificent sight to see these brightly painted buildings reflected off the surface of these reservoirs,” said co-author Nicholas Dunning, head of geography in UC’s College of Arts and Sciences.

A model of Tikal at the National Museum of Archaeology and Ethnography in Guatemala City shows the impressive palace and temple reservoirs that fronted the city. UC researchers found toxic levels of mercury and cyanobacteria in two central reservoirs of Tikal.
Photo/Nicholas Dunning/UC



“The Maya rulers conferred to themselves, among other things, the attribute of being able to control water. They had a special relationship to the rain gods,” Dunning said. “So the reservoir would have been a pretty potent symbol.”


UC’s Tankersley said one popular pigment used on plaster walls and in ceremonial burials was derived from cinnabar, a red-colored mineral composed of mercury sulfide that the Maya mined from a nearby volcanic feature known as the Todos Santos Formation.

A close examination of the reservoir sediment using a technique called energy dispersive X-ray fluorescence spectrometry found that mercury did not leach into the water from the underlying bedrock. Likewise, Tankersley said, UC ruled out another potential source of mercury — volcanic ash that fell across Central America during the frequent eruptions. The absence of mercury in other nearby reservoirs where ash would have fallen ruled out volcanoes as the culprit.


Instead, Tankersley said, people were to blame.

“That means the mercury has to be anthropogenic,” Tankersley said.


With its bright red color, cinnabar was commonly used as a paint or pigment across Central America at the time.

“Color was important in the ancient Maya world. They used it in their murals. They painted the plaster red. They used it in burials and combined it with iron oxide to get different shades,” Tankersley said.

UC associate professor Kenneth TankersleyPhoto/Provided



“We were able to find a mineral fingerprint that showed beyond a reasonable doubt that the mercury in the water originated from cinnabar,” he said.

Tankersley said ancient Maya cities such as Tikal continue to captivate researchers because of the ingenuity, cooperation and sophistication required to thrive in this tropical land of extremes.

“When I look at the ancient Maya, I see a very sophisticated people with a very rich culture,” Tankersley said.

UC’s team is planning to return to the Yucatan Peninsula to pursue more answers about this remarkable period of human civilization.


Featured image at top: UC researchers Nicholas Dunning, left, Vernon Scarborough and David Lentz set up equipment to take sediment samples during their field research at Tikal. Photo/Liwy Grazioso Sierra

.

Contacts and sources:
Michael Miller
University of Cincinnati




    

What Were They Smoking? Non-Tobacco Plant Identified In Ancient Pipe For First Time






People in what is now Washington State were smoking Rhus glabra, a plant commonly known as smooth sumac, more than 1,400 years ago.


Replica pipes used to experimentally "smoke" tobacco and other native plants in WSU laboratories for the study. The charred residue is then extracted, chemically "fingerprinted", and compared to residue of ancient archaeological pipes.
A row of pipes being used in a study.
Credit: Washington State University

The discovery, made by a team of Washington State University researchers, marks the first-time scientists have identified residue from a non-tobacco plant in an archeological pipe.

Unearthed in central Washington, the Native American pipe also contained residue from N. quadrivalvis, a species of tobacco not currently grown in the region but that is thought to have been widely cultivated in the past. Until now, the use of specific smoking plant mixtures by ancient people in the American Northwest had only been speculated about.

“Smoking often played a religious or ceremonial role for Native American tribes and our research shows these specific plants were important to these communities in the past,” said Korey Brownstein, a former WSU Ph.D. student now at the University of Chicago and lead author of a study on the research in the journal Frontiers in Molecular Biosciences. “We think the Rhus glabra may have been mixed with tobacco for its medicinal qualities and to improve the flavor of smoke.”

Korey Brownstein 
Credit: Washington State University

The discovery was made possible by a new metabolomics-based analysis method that can detect thousands of plant compounds or metabolites in residue collected from pipes, bowls and other archeological artifacts. The compounds can then be used to identify which plants were smoked or consumed.

“Not only does it tell you, yes, you found the plant you’re interested in, but it also can tell you what else was being smoked,” said David Gang, a professor in WSU’s Institute of Biological Chemistry and a co-author of the study. “It wouldn’t be hyperbole to say that this technology represents a new frontier in archaeo-chemistry.”

Previously, the identification of ancient plant residues relied on the detection of a limited number of biomarkers, such as nicotine, anabasine, cotinine and caffeine. Gang said the issue with this approach is while the presence of a biomarker like nicotine shows tobacco was smoked it doesn’t distinguish which species it was.

“Also, if you are only looking for a few specific biomarkers, you aren’t going to be able to tell what else was consumed in the artifact,” Gang said.

In addition to identifying the first non-tobacco plant smoked in an archaeological pipe, the WSU researchers’ work also helps elucidate the complex evolution of tobacco trade in the American Northwest.

Shannon Tushingham and David Gang

Credit: Washington State University

Analysis of a second pipe that was used by people living in Central Washington after Euro-American contact revealed the presence of a different tobacco species, N. rustica, which was grown by native peoples on the east coast of what is now the United States.

“Our findings show Native American communities interacted widely with one another within and between ecological regions, including the trade of tobacco seeds and materials,” said Shannon Tushingham, an assistant professor of anthropology at WSU and co-author of the study. “The research also casts doubt on the commonly held view that trade tobacco grown by Europeans overtook the use of natively-grown smoke plants after Euro-American contact.”

Moving forward, the WSU researchers’ work could ultimately help scientists studying ancient societies in the Americas and elsewhere around the globe identify which plant species ancient people were consuming, providing important information about the evolution of drug use and similar plant-human dynamics.

Dr. Korey Brownstein with Native American students planting indigenous tobacco species at Washington State University.

Credit: Washington State University

Closer to home, the WSU team is also putting their work to use helping confirm connections between ancient plant management practices from before the arrival of Western settlers with cultural traditions of modern indigenous communities such as the Nez Perce. The researchers shared their work with members of the tribe who also used some of the seeds from the study to grow some of the pre-contact tobacco. The smoking of tobacco is a sacred tradition for Native American groups including the Nez Perce, Colville and other northwest Tribes and before now it was impossible to tell which kind of tobacco their ancestors smoked.

“We took over an entire greenhouse to grow these plants and collected millions of seeds so that the Nez Perce people could reintroduce these native plants back onto their land,” Brownstein said. “I think these kinds of projects are so important because they help build trust between us and tribal communities and show that we can work together to make discoveries.”


Contacts and sources: 
annon Tushingham / Will Ferguson
Washington State University



    

SDO Ten Year Time Lapse Video of the Sun Condensed and Ten Things We Learned


As of June 2020, NASA’s Solar Dynamics Observatory – SDO – has now been watching the Sun non-stop for over a full decade. From its orbit in space around Earth, SDO has gathered 425 million high-resolution images of the Sun, amassing 20 million gigabytes of data over the past 10 years. This information has enabled countless new discoveries about the workings of our closest star and how it influences the solar system.

With a triad of instruments, SDO captures an image of the Sun every 0.75 seconds. The Atmospheric Imaging Assembly (AIA) instrument alone captures images every 12 seconds at 10 different wavelengths of light. This 10-year time lapse showcases photos taken at a wavelength of 17.1 nanometers, which is an extreme ultraviolet wavelength that shows the Sun’s outermost atmospheric layer – the corona. Compiling one photo every hour, the movie condenses a decade of the Sun into 61 minutes. The video shows the rise and fall in activity that occurs as part of the Sun’s 11-year solar cycle and notable events, like transiting planets and eruptions. The custom music, titled “Solar Observer,” was composed by musician Lars Leonhard

This 10-year time lapse of the Sun at 17.1 nanometers (an extreme ultraviolet wavelength that shows the Sun’s outermost atmospheric layer – the corona) shows the rise and fall of the solar cycle and notable events, like transiting planets and solar eruptions.

Credits: NASA’s Goddard Space Flight Center/SDO

While SDO has kept an unblinking eye pointed toward the Sun, there have been a few moments it missed. The dark frames in the video are caused by Earth or the Moon eclipsing SDO as they pass between the spacecraft and the Sun. A longer blackout in 2016 was caused by a temporary issue with the AIA instrument that was successfully resolved after a week. The images where the Sun is off-center were observed when SDO was calibrating its instruments.

In February 2020, NASA’s Solar Dynamics Observatory — SDO — is celebrating its 10th year in space. Over the past decade the spacecraft has kept a constant eye on the Sun, studying how the Sun creates solar activity and drives space weather — the dynamic conditions in space that impact the entire solar system, including Earth.

Since its launch on Feb. 11, 2010, SDO has collected millions of scientific images of our nearest star, giving scientists new insights into its workings. SDO’s measurements of the Sun — from the interior to the atmosphere, magnetic field, and energy output — have greatly contributed to our understanding of our closest star. SDO’s images have also become iconic — if you’ve ever seen a close up of activity on the Sun, it was likely from an SDO image.


SDO and other NASA missions will continue to watch our Sun in the years to come, providing further insights about our place in space and information to keep our astronauts and assets safe.


1) Fantastic Flares

SDO has witnessed countless astounding flares — giant outbursts of plasma released from the solar surface — many of which have become iconic images of the ferocity our nearest star. In its first year and a half, SDO saw nearly 200 solar flares, which allowed scientists to spot a pattern. They noticed that around 15% of the flares had a “late phase flare” that would follow minutes to hours after the initial flare. By studying this special class, scientists gained a better understanding of just how much energy is produced when the Sun erupts.
2) Solar Tornadoes

In February 2012, SDO captured images showing strange plasma tornados on the solar surface. Later observations found these tornadoes, which were created by magnetic fields spinning the plasma, could rotate at speeds up to 186,000 miles per hour. On Earth tornadoes only reach speeds of 300 miles per hour.

This video, assembled from images taken by NASA’s SDO spacecraft, shows possible plasma tornadoes over a 30-hour period.

Credits: NASA's Goddard Space Flight Center]

3) Giant Waves

The churring sea of plasma on the solar surface can create giant waves that travel around the Sun at up to 3 million miles per hour. Theses waves, named EIT waves after an instrument of the same name on the Solar and Heliophysics Observatory spacecraft that first discovered them, were imaged at high resolution by SDO in 2010. The observations showed for the first time how the waves move across the surface. Scientists suspect these waves are driven by coronal mass ejections, which spew clouds of plasma off the surface of the Sun into the solar system.
4) Combustible Comets

Over the years, SDO has watched two comets fly by the Sun. In December 2011, scientist watched as Comet Lovejoy managed to survive the intense heating as it passed 516,000 miles above the solar surface. Comet ISON in 2013 didn’t survive its encounter. Through observations such as these, SDO has provided scientists with new information about how the Sun interacts with comets.



Comet Lovejoy is seen here exiting from behind the right side of the sun, after an hour of travel through its closest approach to the sun. By tracking how the comet interacts with the sun's atmosphere, the corona, and how material from the tail moves along the sun's magnetic field lines, solar scientists hope to learn more about the corona. This movie was filmed by the Solar Dynamics Observatory (SDO) in 171 angstrom wavelength, which is typically shown in yellow.

Credits: NASA/SDO



5) Global Circulation

Having no solid surface, the entire Sun is continually flowing due to the intense heat trying to escape and the rotation of the Sun. Moving about at the mid-latitudes are large-scale circulation patterns called Meridonial circulation. SDO’s observations revealed that these circulations are much more complex than scientists initially thought and are linked to sunspot production. These circulation patterns may even explain why at times one hemisphere might have more sunspots than another.
6) Predicting the Future

The Sun’s outpouring of material from coronal mass ejections, or CMEs, and the solar wind speed across the solar system. When they interact with Earth’s magnetic environment, they can induce space weather, which can be hazardous to spacecraft and astronauts. Using data from SDO, NASA scientists have worked on modeling the path of a CME as it moves across the solar system in order to predict its potential effect on Earth. The long baseline of solar observations has also helped scientists form additional machine-learning models to try to predict when the Sun might release a CME.

7) Coronal Dimmings

The Sun’s wispy superheated outer atmosphere — the corona — sometimes dims. Scientists studying coronal dimming have found that they are linked to CMEs, which are the main drivers of the severe space weather events that can damage satellites and harm astronauts. Using a statistical analysis of the large number of events seen with SDO, scientists were able to calculate the mass and velocity of Earth-directed CMEs — the most dangerous type. By linking coronal dimming to the size of CMEs, scientists hope to be able to study the space weather effects around other stars, which are too distant to directly measure their CMEs.

8) Death and Birth of a Solar Cycle

With a decade of observations, SDO has now seen nearly a complete 11-year solar cycle. Starting near the beginning of Solar Cycle 24, SDO watched as the Sun’s activity ramped up to solar maximum and then faded to the current ongoing solar minimum. These multiyear observations help scientists understand signs that signal the decline of one solar cycle and the onset of the next.
9) Polar Coronal Holes

At times the Sun’s surface is marked by large dark patches called coronal holes where extreme ultraviolet emission is low. Linked to the Sun’s magnetic field, the holes follow the solar cycle, increasing at the solar maximum. When they form at the top and the bottom on the Sun they’re called polar coronal holes and SDO scientists were able to use their disappearance to determine when the Sun’s magnetic field reversed — a key indicator of when the Sun reaches solar maximum.

This image from NASA’s Solar Dynamics Observatory on March 16, 2015, shows two dark spots, called coronal holes. The lower coronal hole, a polar coronal hole, was one of the biggest observed in decades.


Credits: NASA/SDO



10) New Magnetic Explosions

At the end of the decade in December 2019, SDO observations enabled scientists to discover a whole new type of magnetic explosion. This special type — called spontaneous magnetic reconnection (versus previously observed more general forms of magnetic reconnection) — helped confirm a decades-old theory. It also may help scientists understand why the solar atmosphere is so hot, better predict space weather, and lead to breakthroughs in controlled fusion and lab plasma experiments.

Forced magnetic reconnection, caused by a prominence from the Sun, was seen for the first time in images from NASA’s Solar Dynamics Observatory, or SDO. This image shows the Sun on May 3, 2012, with the inset showing a close-up of the reconnection event imaged by SDO’s Atmospheric Imaging Assembly instrument, where the signature X-shape is visible.


Credits: NASA/SDO/Abhishek Srivastava/IIT(BHU)




All instruments on SDO are still in good order, with the potential to stay functioning for another decade.



Capturing an image in 10 different wavelengths of light every 12 seconds, NASA’s Solar Dynamics Observatory — SDO — has provided an unprecedentedly clear picture of how massive explosions on the Sun grow and erupt ever since its launch on Feb. 11, 2010. The imagery is also captivating, allowing one to watch the constant ballet of solar material through the Sun's atmosphere, the corona. This year marks the 10th anniversary of SDO's launch and the start of its decade watching the Sun.

Credits: NASA's Goddard Space Flight Center

In its 10th year, SDO will be joined by a new joint ESA-NASA mission, Solar Orbiter. With an inclined orbit, Solar Orbiter will be able to see the polar regions for which SDO has limited coverage. Solar Orbiter also has complementary instruments that will allow the two missions to work together to create 3D images of structures below the visible surface of the Sun, giving scientists an even greater understanding of solar activity in the years to come.







Contacts and sources:
Mara Johnson-Groh
NASA’s Goddard Space Flight Center