Culture

As bad as things might seem here in 2020, they could be worse: we could be living 252 million years ago during the Permian mass extinction. Volcanic eruptions and dramatic, sudden climate change killed most of the animals on land and almost everything in the oceans, setting the stage for the later rise of the dinosaurs on land and an explosion of new marine life. One kind of marine reptile, the ichthyosaurs, eventually evolved into sleek, dolphin-like predators, but scientists don't know much about early ichthyosaurs. But by CT-scanning the fossil of one of the first ichthyosaurs, scientists discovered pebble-shaped teeth hidden in its short snout. These strange teeth, probably used for crushing the shells of snails and clam-like bivalves, help illuminate the ways that early ichthyosaurs filled different roles in Triassic marine ecosystems.

"We don't know exactly the ancestry of ichthyosaurs. They're reptiles, and they're probably archosaurs--that is to say, they're more closely related to crocodiles and dinosaurs and birds than they are to lizards and snakes--but even that isn't 100%," says Olivier Rieppel, a paleontologist and Rowe Family Curator of Evolutionary Biology at Chicago's Field Museum, who co-authored a new paper on the findings in Scientific Reports. "By studying this early ichthyosaur's unusual rounded teeth, we get a better understanding of how these animals evolved and what their lifestyles were like."

The paper focuses on Cartorhynchus lenticarpus, one of the earliest and smallest ichthyosaurs ever discovered. Later ichthyosaurs were dolphin-like, with long snouts full of sharp teeth and sleek, streamlined bodies for cutting through the water. But if those ichthyosaurs looked like murder dolphins, then Cartorhynchus was kind of a seal-tadpole. Its name means "short-snouted," and its face matches its name. Cartorhynchus was only a little more than a foot long, and its flexible wrist joints suggest that it was able to come up out of the water and scoot around on land like a seal. "Ichthyosaurs became creatures of the open ocean, but the smaller species like Cartorhynchus probably lived closer to the shore and picked up invertebrates to eat from the sea floor," says Rieppel.

This new study builds on the description of Cartorhynchus by several of the same scientists in 2014, including the new paper's corresponding author, Ryosuke Motani of the University of California, Davis. "When we first described Cartorhynchus, we thought that it didn't have any teeth at all and was a suction feeder. But later on, researchers realized that it did have some teeth further back in its jaws," says Rieppel. "In this study, we took CT scans of the fossil to see the teeth that were hidden in its skull, and we found that they had an unusual pebble-like shape."

These rounded teeth were in the back of the jaws, where our molars are, and were likely used to crush small hard-shelled invertebrates like snails and clam-like bivalves. The teeth also showed wear and tear suggesting that even though the only known specimen of Cartorhynchus was just over one foot long, it was full-grown.

Armed with this new knowledge about Cartorhynchus, the researchers compared it to other early ichthyosaurs. They found that rounded teeth cropped up in several other ichthyosaur species, suggesting that the trait evolved independently more than once, rather than all round-toothed ichthyosaurs evolving from one common round-toothed ancestor. Meanwhile, many other early ichthyosaurs had pointed cone-shaped teeth.

These different tooth shapes springing up in different families gives us a glimpse of the world in which ichthyosaurs were evolving. "There were no marine reptiles prior to the Triassic," says Rieppel. "That's what makes these early ichthyosaurs so interesting--they tell us about the recovery from the mass extinction, because they entered the sea only after it." And, since most sea creatures died in the mass extinction, there was a lot of free real estate, evolutionarily speaking--lots of niches for new animals to fill. "After the mass extinction, the marine biota was nearly empty and ready to be recolonized," Rieppel explains.

Animals' teeth can tell us a lot about their lifestyles: what they were eating and how. The rapid emergence of lots of different kinds of ichthyosaurs with different kinds of teeth points to the way that they took over the oceans and played different ecological roles. It's also likely that the repeated evolution of rounded crushing teeth in ichthyosaurs like Cartorhynchus and others was driven by the evolution of hard-shelled prey that became prevalent at this time.

"Fossils are clues about what the world was like long ago," says Rieppel. "By gaining a better understanding of how these ichthyosaurs evolved, we get a better sense of how life rebounds after extinctions, and that lesson is still relevant today."

What The Viewpoint Says: The authors explain why COVID-19 presents a greater burden for immigrant communities and this article advocates for a more equitable health care system.

Authors: Jonathan Ross, M.D., M.S., of the Montefiore Health System and Albert Einstein College of Medicine in the Bronx, New York, is the corresponding author.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jamainternmed.2020.2131)

Editor's Note: The article includes conflict of interest disclosures. Please see the article for additional information, including other authors, author contributions and affiliations, conflicts of interest and financial disclosures, and funding and support.

An international study led by Nanyang Technological University, Singapore (NTU Singapore) scientists found that the global mean sea-level rise could exceed 1 metre by 2100 and 5 metres by 2300 if global targets on emissions are not achieved.

The study used projections by more than 100 international experts for the global mean sea-level changes under two climate scenarios - low and high emissions. By surveying a wide range of leaders in the field, the study offers broader assurance about its projections for the ranges of future sea-level rise.

In a scenario where global warming is limited to 2 degree Celsius above pre-industrial levels, the experts estimated a rise of 0.5 metres by 2100 and 0.5 to 2 metres by 2300. In a high-emissions scenario with 4.5 degree Celsius of warming, the experts estimated a larger rise of 0.6 to 1.3 metres by 2100 and 1.7 to 5.6 metres by 2300.

Professor Benjamin Horton, Acting Chair of NTU's Asian School of the Environment, who led the survey, said that sea-level rise projections and knowledge of their uncertainties are vital to make informed mitigation and adaptation decisions.

Prof Horton said, "The complexity of sea-level projections, and the sheer amount of relevant scientific publications, make it difficult for policymakers to get an overview of the state of the science. To obtain this overview, it is useful to survey leading experts on the expected sea-level rise, which provides a broader picture of future scenarios and informs policymakers so they can prepare necessary measures."

Published in Nature Partner Journals Climate and Atmospheric Science on 8 May, the projections of sea-level rise exceed previous estimates by the International Panel on Climate Change (IPCC).

The NTU-led international study was a collaboration with researchers from The University of Hong Kong, Maynooth University (Ireland), Durham University (UK), Rowan University (USA), Tufts University (USA), and the Potsdam Institute for Climate Impact Research (Germany).

"We know that the planet will see additional sea-level rise in the future," says co-author Dr Andra Garner, Assistant Professor of Environmental Science at Rowan University in the United States of America. "But there are stark differences in the amount of sea-level rise experts project for low emissions compared to high emissions. This provides a great deal of hope for the future, as well as a strong motivation to act now to avoid the more severe impacts of rising sea levels."

"This international study is based on the informed opinions of 106 sea-level experts and underlines the critical importance of pursuing a low emissions policy to limit sea-level rise," says Dr Niamh Cahill, Assistant Professor in the Dept of Mathematics and Statistics at Maynooth University in Ireland.

The 106 experts who participated in the survey were chosen as they were among the most active publishers of scientific sea-level studies (at least six published papers in peer-reviewed journals since 2014) identified from a leading publication database.

In response to open-ended questions, the climate change experts identified the Greenland and Antarctic Ice Sheets as the greatest sources of uncertainty. These ice sheets are an important indicator of climate change and driver of sea-level rise. Satellite-based measurements show the ice sheets are melting at an accelerating rate. However, the experts also noted that the magnitude and impact of sea-level rise can be limited by successfully reducing emissions.

Dr Andrea Dutton, Professor in the Department of Geoscience at the University of Wisconsin-Madison, who is not involved in this study, says, "One of the key take-aways from this study is that our actions today can make a profound difference in how much our coastlines will retreat in the future. That knowledge is empowering because it means that we can choose a better outcome through our actions."

In nature, every species must be equipped with a strategy to be able to survive in response to danger. Plants, too, have innate systems that are triggered in response to a particular threat, such as insects feeding on them. For example, some plants sense "herbivore-derived danger signals" (HDS), which are specific chemicals in oral secretions of insects. This activates a cascade of events in the plant's defense machinery, which leads to the plant developing "resistance" to (or "immunity" against) the predator. But despite decades of research, exactly how plants recognize these signals has remained a bit of a mystery.

In a new study published in Communications Biology, a research team from Tokyo University of Science, Ehime University, Okayama University, The University of Tokyo, and Iwate Biotechnology Research Center, led by Prof Gen-ichiro Arimura, attempts to shed light on exactly how plant HDS systems work. They chose to study membrane proteins called "receptor-like kinases" (RLKs), which are found in soybean leaves. They based their study on previous evidence from plants like Arabidopsis, tobacco, and cowpea, in which RLKs play a major role in HDS systems. Prof Arimura says, "Scientists have been trying to understand the molecular mechanism of plant resistance for years, but the 'sensors' involved in plant recognition of insect pests are still not known. Thus, we wanted to get a detailed understanding of these mechanisms."

To begin with, the scientists focused on soybean RLK genes that were structurally and functionally similar to a RLK gene, which is known to trigger a danger response by recognizing "oligosaccharides" (small carbohydrate molecules) during pathogen attack. They speculated that owing to these similarities, soybean genes might also show a mechanism similar to that seen in pathogen resistance. They found 15 such genes through genetic analysis. Next, the scientists generated 15 types of Arabidopsis plants, each plant uniquely expressing only one of the 15 individual soy genes. When they tested these plants using oral secretions from the pest, they uncovered genes for two novel RLKs that showed a defense response specific to the oral secretions, called GmHAK1 and GmHAK2. These findings were unprecedented: the role of these RLKs in soybean HDS systems had never been revealed before. Moreover, when the scientists dug deeper into the mechanism of these regulatory factors in Arabidopsis, they found two proteins, a HAK homolog and PBL27 (which play a role in intracellular signaling), to be involved in this pathway. Accordingly, this confirmed what the scientists had initially expected--soybean and Arabidopsis possess similar mechanisms for "danger response."

In agriculture, it is crucial to develop strategies for pest control in crop plants to avoid incurring losses. This study takes a massive step in this direction by uncovering an important cellular mechanism that triggers defense response in plants. Manipulating this innate cellular system may even help scientists to fuel the development of new agricultural products, potentially making life easier for farmers. Prof Arimura concludes, "It has been challenging to find new pest control methods that are effective and do not harm the ecosystem in any way. Our study offers a potential solution to this problem by uncovering the details of how certain plants develop resistance."

When we find something particularly beautiful or impressive, we literally get big eyes: Our pupils dilate. The pupil controls how much light enters the eye and falls on the retina. When there is a lot of light, the pupil contracts; when there is little light, it opens again. Neuroscientists from the German Primate Center (DPZ) - Leibniz Institute for Primate Research and the European Neuroscience Institute Göttingen have now found out in a study of humans and rhesus monkeys that the movement of the pupil is not only reflexively controlled by the amount of incident light, but unconsciously also by our mind. Thus, the pupil can follow rhythms that arise in the environment. In this way, the opening of the pupil is optimally adapted to our environment which enhances perception (Journal of Neuroscience).

Sensory impressions from our environment are often rhythmic, not only when we hear, but also when we see. For example, the blue light of a passing ambulance flashes about 120 times per minute. We also react unconsciously to visual events in our environment, which can be registered by our senses as regular patterns. From these patterns our brain can, for example, deduce when the next flash of blue light will hit the eye and prepare itself for it.

An important factor in vision is the adjustment of the pupil diameter. Smaller pupils provide a sharper image, while larger pupils allow more light to reach the retina, making it more likely that even weak stimuli will be processed at all. Pupil diameter is controlled by the pupillary reflex, which automatically, i.e. without our knowledge or intention, adjusts the pupil muscles to the incidence of light. But not all relevant environmental information is contained in the amount of incident light alone. Computations are therefore required in the brain that go beyond the capabilities of a reflex to take into account all available information. The aim of this study, funded by the German Research Foundation (DFG), was to find out whether and to what extent pupil dynamics are controlled fully automatically or whether they are also influenced by more complex rhythms in the environment.

For the investigations, pupil movements of two male rhesus monkeys (Macaca mulatta) and several test subjects of both sexes were measured using a high-speed video camera, while the subjects were shown sequences of images of human faces at a temporal frequency of two hertz. A dark background was shown between the images. The alternation of background and image causes the pupil to dilate and contract in rhythm with the images. During the experiments, the order of the images was manipulated - they were grouped in pairs so that a particular image always followed a particular other image. Thus, there are two rhythms to which the pupil reacts: a fast one (two hertz), which results from the alternation of image and background, and one at half that pace (one hertz), which results from the arrangement of the images as pairs. The sequence of the pairs is not given by the light itself, and therefore requires an additional computation of environmental rhythms in the brain. Since the luminance of the faces in all pictures as well as the dark background in the "pauses" remained unchanged, but the arrangement of the pictures varied, conclusions could be drawn about the influence of this additional computation on pupil dynamics.

In addition to the structured sequence, randomly arranged images with the same frequency (two hertz) were shown. A comparison of the results between structured and unstructured image sequences at the same image frequency shows that in both species studied the pupil follows not only the light-related rhythm of the images, but also the more complex rhythm of the pairs. Pupil movement in a slow (one hertz) rhythm keeps the pupil open longer, as if a pair should not be interrupted by the closing of the pupil. This allows more light to reach the retina. "The additional information contained in the environment thus complements the information already reaching the retina via the incident light," says Caspar Schwiedrzik, head of the junior research group "Perception and Plasticity". Furthermore, the study was able to show that this contributes to an improvement in perception, even if the test subjects are not aware that there is a rhythm in the environment. "Pupil control is therefore not purely reflexive, but is also influenced by our unconscious thoughts," adds Schwiedrzik.

A protein shredder that occurs in cell membranes of brain cells apparently also indirectly regulates the fat metabolism. This is shown by a recent study by the University of Bonn. The shredder, known as gamma-secretase, is considered a possible target for drugs against cancer and Alzheimer's disease. However, the results suggest that such agents may have long-range effects that need to be watched closely. The study has now been published in the journal "Life Science Alliance".

Every cell in the body is surrounded by a fatty film called the plasma membrane. It also contains numerous proteins that span the membrane from outside to inside and act as sensors for the cell: When they encounter certain molecules on the outside, they generate a signal on the inside of the membrane, thereby regulating certain reactions within the cell. Other membrane proteins are able to transport certain substances into the cell.

Gamma-secretase plays an important role in the release of membrane-anchored signaling proteins. But it is also a "cleaning specialist" for discarded membrane proteins: It breaks down the proteins within the cell membrane for further disposal. With this function, the secretase has been in the focus of Alzheimer's research for almost two decades: Many brain cells contain a protein called APP in their membrane. When gamma-secretase breaks down APP, one of the fragments is released into the brain fluid: the so-called Abeta peptide. This peptide is the main constituent of the plaques found in the damaged brain areas of Alzheimer's patients. "Originally, it was therefore hoped that the inhibition of gamma-secretase could slow down Alzheimer's disease," explains Prof. Dr. Jochen Walter. "Unfortunately, that hasn't proved successful so far."

Waste in the membrane

It is now known that gamma secretase exerts important roles in the functioning of cells. If it fails, cellular membranes gradually fills up with waste. This could for instance impair the effective uptake of certain molecules into the cells. The current study shows serious consequences of such a failure. The APP also plays a key role here: "When we inhibit gamma secretase in cell cultures, APP accumulates in the membranes," explains Walter's colleague Dr. Esteban Gutierrez. "This in turn hinders the absorption of so-called lipoproteins from the environment."

This mechanism triggers a fatal process. Lipoproteins are particles of proteins and fat-like molecules, the lipids. If too few of them enter the cell, the cell suspects a lipid deficiency. To remedy this, the cell increases its own lipid synthesis. "We have shown that inhibition of the causes a strong activation of a central regulator of lipid synthesis called LXR," says Gutierrez. The lipids are partially transported out of the cell; however, due to the disturbed lipoprotein uptake, the cell does not receive feedback that this measure was successful and continues to produce more lipids. This means that numerous fat droplets accumulate inside the cell over time. In excessive quantities, this leads to adiposis in the cell interior, which can disrupt important cellular functions.

"Other studies have already shown that a disruption of the lipid metabolism in the brain can also contribute to the development of Alzheimer's disease," explains Prof. Walter. "Our study points to a mechanism by which this could happen." The inhibition of gamma secretase may therefore cause an opposite effect one would expect from this measure.

Inhibition of secretase hinders the division of cancer cells

However, it is more promising in another context - the fight against cancer. The cell membrane contains proteins that stimulate cell division. If gamma-secretase is inactivated in tumor cells, these proteins are no longer released from the membrane, and thus, the cancer cells can no longer replicate as quickly. "In this case, too, the treatment causes side effects," Walter emphasizes. "As long as they are mainly confined to cancer cells, this is probably not a major problem; nevertheless, one should keep an eye on them."

Lipids are essential building blocks of cell membranes, which control the exchange of substances and energy between a cell and its environment. Developed at the Moscow Institute of Physics and Technology, a new open-source software tool PCAlipids aims to analyze lipid behavior. The new program has been presented in a paper that comes out in print in the upcoming July 1 issue of Biochimica et Biophysica Acta -- Biomembranes.

Every living cell is surrounded by a membrane that serves a number of vital functions, from facilitating the uptake of materials essential for survival to controlling cell regulatory processes. What enables this wide range of functions is the unique structure of the membrane: almost rigid proteins incorporated in a flexible lipidic layer.

The lipid composition of membranes has been found to influence how the individual proteins and the membrane as a whole function, therefore emphasizing the importance of lipids. However, the exact molecular mechanism of lipid-protein interplay is yet to be uncovered. PCAlipids is an important step toward understanding that mechanism.

Ways to examine lipid-protein interplay in membranes

The studies of membrane proteins and lipids cannot rely on the same techniques. While a host of experimental methods are available to study protein functioning, they lack either temporal or spatial resolution for analyzing lipids. To close this gap, various computational techniques are employed.

One of them, molecular dynamics simulations, enable researchers to examine the dynamics of a molecular system with atomic precision and at a timescale of picoseconds, or trillionths of a second. In order to achieve biologically relevant temporal and spatial scales, the interatomic interactions of quantum nature are simplified to a classical representation. The method involves calculating the forces that act on each atom and solving the associated Newton's equations of motion. The set of parameters used to define interatomic forces is called a force field.

To make sure that force fields are reliable, they undergo validation: Simulation results are contrasted with actual experimental data. The force fields used to model the behavior of the protein-lipid systems in cell membranes require such validation, too. That defines the focus of the tools that aim to analyze the simulations of membrane systems: It is mainly the experimentally measurable quantities that are extracted from the simulations. Due to the limitations of experimental techniques, the currently used analyses focus on large groups of lipids, while the behavior of individual lipids does not get much attention.

New software to analyze individual lipids

Pavel Buslaev, Khalid Mustafin, and Ivan Gushchin from the MIPT Research Center for Molecular Mechanisms of Aging and Age-Related Diseases have developed an open-source script called PCAlipids that analyzes the structure of individual lipid molecules at a given moment and describes their conformational changes -- the reshaping of molecules. A method known as principal component analysis underlies the script.

"PCAlipids is a piece of software that enables describing the motion of an individual molecule. While our study focused on lipids, the method is applicable to other molecules as well," explained Buslaev, who is a researcher at the MIPT Laboratory of Structural Analysis and Engineering of Membrane Systems.

"As of now, it is not possible to experimentally measure the values analyzed by PCAlipids," he added. "However, we have proposed several experiments. Hopefully, this will lead to the development of a new experimental area. The resulting data could then be contrasted with simulated lipid behavior to refine model parameters."

PCAlipids first identifies groups of atoms moving together. Next, it defines a new basis, such that the first basis vector is associated with the collective motion that has the largest amplitude and involves the largest number of atoms. The second most important motion determines the second basis vector and so on.

The analysis that follows relies on the established basis and aims to determine the effects of various factors on the lipid molecules. For example, an additional compound can be introduced into the simulation. If that affects the first, most significant collective motions, it means the compound will have a major influence on the membrane. Otherwise, its impact will be low. The manner in which the collective motions are impacted can reveal the mechanisms behind the compound's effects.

Effects of temperature, cholesterol, and more on lipids

The team from MIPT used the new software to study the effects of temperature, cholesterol, and membrane curvature on individual lipids. These parameters have long been known to influence the behavior of the membrane as a whole, but it remained unknown how they affect individual molecules.

Lowering the temperature causes the membrane to undergo a phase transition: The lipids become largely ordered. PCAlipids helped to highlight the beginning of phase transition and quantitatively describe how the number of possible lipid structures varies as the freezing point is approached. It turned out that this number remains stable up until freezing, but the rate of transitions between these structures grows progressively slower.

Cholesterol is a crucial cell membrane component that promotes lipid ordering. PCAlipids revealed that the significant collective motions become more compact in the presence of cholesterol. The simulation also exposed the mechanism that mediates the effects of cholesterol on lipid ordering.

The cell membrane is flexible and tends to bend a lot, which is vital to its functioning. This leads to one membrane layer being convex and the other concave. Both configurations proved to accommodate the same range of possible lipid structures; however, the rate of transitions between different structures is noticeably higher in the convex layer.

The study has demonstrated that PCAlipids can be used to investigate the structure of lipid systems. The tool replicates the findings of prior research, but also reveals details that remained elusive up until now. This illustrates the potential of the new software developed at MIPT to provide insights into the processes that occur in cell membranes.

New Rochelle, NY, May 7, 2020--Tissue engineering has a unique set of tools and technologies for developing preventive strategies, diagnostics, and treatments that can play an important role during the ongoing COVID-19 pandemic. Three key areas pioneered by tissue engineers that could be applied to the current COVID-19 crisis and to future viral outbreaks are highlighted in an article published in Tissue Engineering, Part A, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers. Click here here to read the full-text article available Open Access on the Tissue Engineering website.

Alexander Tatara, MD, PhD, Massachusetts General Hospital (Boston) is author of the article entitled "The Role of Tissue Engineering in COVID-19 and Future Viral Outbreaks." Dr. Tatara emphasizes critical strengths of the field: applying engineering principles to biological systems, collaboration across disciplines, and rapid translation of technologies from the benchtop to the bedside. The three key areas of tissue engineering that could make an impact on the fight against COVID-19 are in vitro models of viral disease to better understand the mechanism of infection and to screen for potential therapeutics; drug delivery systems to better target medications and increase their bioavailability; and vaccine platforms, using biomaterials for vaccine delivery and to boost the immune response to the vaccine.

"In this timely work, Dr. Tatara brings a needed clinical perspective on the critical strategies that the tissue engineering field can provide to help stem the COVID-19 pandemic. This article should be a powerful resource for tissue engineering laboratories around the world," says Tissue Engineering Co-Editor-in-Chief John P. Fisher, PhD, Fischell Family Distinguished Professor & Department Chair, and Director of the NIH Center for Engineering Complex Tissues at the University of Maryland.

A rich variety of meteorological phenomena take place in the extensive hydrogen atmosphere of the planet Saturn, a world about ten times the size of the Earth. They help us to better understand those that operate in a similar way in the Earth's atmosphere. Featuring among them due to its uniqueness is the well-known "hexagon", an amazing wave structure that surrounds the planet's polar region and whose shape looks as if it had been drawn by a geometrician.

Discovered in 1980 by NASA's Voyager 1 and 2 spacecraft, it has been observed without interruption since then, despite the planet's long, strong cycle of seasons. A fast, narrow jet stream flows inside this gigantic planetary wave where winds reach maximum speeds of about 400 km/h. Yet, strangely enough, the wave itself remains almost static; in other words, it barely shifts with respect to the planet's rotation. All these properties mean that the "hexagon" is a highly attractive phenomenon for meteorologists and planet atmosphere researchers.

Cassini, which was in orbit around the planet between 2004 and 2017, took a vast quantity of images from a whole range of distances from the planet and viewing angles. In June 2015 its main camera obtained very high-resolution images of the planet's limb which are capable of solving details of between 1 and 2 km; they captured the hazes located above the clouds that shape the hexagonal wave. In addition, it used many colour filters, from ultraviolet to near infrared, thus enabling the composition of these hazes to be studied. To complete this study, images produced by the Hubble Space Telescope taken 15 days later and showing the hexagon not on the limb but seen from above were also used. "The Cassini images have enabled us to discover that, just as if a sandwich had been formed, the hexagon has a multi-layered system of at least seven mists that extend from the summit of its clouds to an altitude of more than 300 km above them," said Professor Agustín Sánchez-Lavega, who led the study. "Other cold worlds, such as Saturn's satellite Titan or the dwarf planet Pluto, also have layers of hazes, but not in such numbers nor as regularly spaced out".

The vertical extent of each haze layer is between approximately 7 and 18 km thick, and according to the spectral analysis, they contain minute particles with radii of the order of 1 micron. Their chemical composition is exotic for us, because, owing to the low temperatures in Saturn's atmosphere ranging between 120° C and 180° C below zero, they could comprise hydrocarbon ice crystallites, such as acetylene, propyne, propane, diacetylene or even butane in the case of the highest clouds.

Another aspect studied by the team is the regularity in the vertical distribution of the hazes. The hypothesis put forward is that the hazes are organised by the vertical propagation of gravity waves that produce oscillations in the density and temperature of the atmosphere, a well-known phenomenon on the Earth and on other planets. The researchers raise the possibility that it could be the very dynamics of the hexagon itself and its powerful jet stream that may be responsible for the formation of these gravity waves. On the Earth, too, waves of this type produced by the undulating jet stream travelling at speeds of 100 km/h from West to East in the mid-latitudes have been observed. The phenomenon could be similar on both planets, even though the peculiarities of Saturn mean that it is the only case in the solar system. This is an aspect that remains subject to future research.

Evidence continues to mount that the Neandertals, who lived in Europe and Asia until about 40,000 years ago, were more sophisticated people than once thought. A new study from UC Davis shows that Neandertals chose to use bones from specific animals to make a tool for specific purpose: working hides into leather.

Naomi Martisius, research associate in the Department of Anthropology, studied Neandertal tools from sites in southern France for her doctoral research. The Neandertals left behind a tool called a lissoir, a piece of animal rib with a smoothed tip used to rub animal hides to make them into leather. These lissoirs are often worn so smooth that it's impossible to tell which animal they came from just by looking at them.

Martisius and colleagues used highly sensitive mass spectrometry to look at residues of collagen protein from the bones. The method is called ZooMS, or Zooarchaeology by Mass Spectrometry. The technique breaks up samples into fragments that can be identified by their mass to charge ratio and used to reconstruct the original molecule.

Normally, this method would involve drilling a sample from the bone. To avoid damaging the precious specimens, Martisius and colleagues were able to lift samples from the plastic containers in which the bones had been stored and recover enough material to perform an analysis.

Favoring bovine ribs over deer

The results show that the bones used to make lissoirs mostly came from animals in the cattle family, such as bison or aurochs (a wild relative of modern cattle that is now extinct). But other animal bones from the same deposit show that reindeer were much more common and frequently hunted for food. So the Neandertals were choosing to use only ribs from certain types of animals to make these tools.

"I think this shows that Neandertals really knew what they were doing," Martisius said. "They were deliberately picking up these larger ribs when they happened to come across these animals while hunting and they may have even kept these rib tools for a long time, like we would with a favorite wrench or screwdriver."

Bovine ribs are bigger and more rigid than deer ribs, making them better suited for the hard work of rubbing skins without wearing out or breaking.

"Neandertals knew that for a specific task, they needed a very particular tool. They found what worked best and sought it out when it was available," Martisius said.

The results were published May 8 in Scientific Reports. Coauthors on the study are Teresa Steele, professor of anthropology and Mark Grote at UC Davis; Frido Welker, University of Copenhagen; Tamara Dogandži?, Virginie Sinet-Mathiot and Shannon McPherron, Max Planck Institute for Evolutionary Anthropology, Liepzig; William Rendu, Université de Bordeaux, France; Arndt Wilcke, Fraunhofer Institute for Cell Therapy and Immunology, Liepzig; and Marie Soressi, Leiden University, The Netherlands. The work was partly supported by the NSF.

New Rochelle, NY, May 7, 2020--A new paper identifies the critical need for ) on the ability of the COVID-19 virus to infect certain animal species, the transmissibility of infection between humans and those animals, and the impact infection could have on food security and the economy. The article, which focuses on companion animals, livestock and poultry, working animals such as military service dogs, and zoo species, is published in Vector-Borne and Zoonotic Disease, a peer-reviewed publication from Mary Ann Liebert, Inc., publishers. Click here to read the full-text article free on the Vector-Borne and Zoonotic Disease website.

The authors identify three urgent issues to consider: the potential for domesticated animals to transmit infection to humans and to contribute to community spread of disease; the impact on food security, economy, and trade if livestock and poultry are affected by coronavirus; and the effect on national security if the virus infects military service dogs and impairs their sense of smell, often used for tracking and to detect explosives and narcotics.

Tracey McNamara, DVM, DACVP, NAPf, Western University of Health Sciences (Pomona, CA), Juergen Richt, DVM PhD, Kansas State University (Manhattan, Kansas) and Larry Glickman, VMD, DrPH, Purdue University (West Lafayette, IN) coauthored the article entitled "A Critical Needs Assessment for Research in Companion Animals and Livestock Following the Pandemic of COVID-19 in Humans."

Stringent studies are needed, with robust data collection, and not just anecdotal evidence. Dogs, cats, lions, and tigers have all already tested positive for the COVID-19 virus. Studies are needed on the transmissibility of the virus between animal species and between animals and humans, on the best diagnostic tests available for companion animals and livestock, and on how COVID-19 is expressed in animals.

"The potential for zoonotic SARS-CoV-2 to infect companion animals has been a topic of much discussion," says Stephen Higgs, PhD, Editor-in-Chief of Vector-Borne and Zoonotic Diseases and Director, Biosecurity Research Institute, Kansas State University, Manhattan, KS. "With over 3 million cases of COVID-19 and over a quarter of a million deaths worldwide so far since January, it is vital that we understand the risks posed by domestic animals as a possible source for human infection. This review, brings all of what we know about SARS-CoV-2, pets, and other animals to our readership."

One of the most important tools in stopping the spread of the novel coronavirus, SARS-CoV-2, is rapid, reliable and relatively cheap diagnostic testing at the point of care. Scientists in Europe recently evaluated the frontline capabilities of a commercially available, 15-minute disposable antigen test to detect COVID-19 infections.

Their findings, reported in Frontiers in Medicine, suggest the test could be useful as part of a broader triage strategy for slowing down the virus, which has infected more than seven million people and caused about 250,000 deaths as of May 4.

"The detection of viral infections in patients attending primary care centres would allow healthcare workers to rapidly identify new outbreak foci and define quarantine measures for high viral shedders and/or suspect patients to limit the spread of the epidemic," the authors wrote.

The two-phase study examined the sensitivity and specificity of the new test during its development stage in the lab and later on using real-world biological samples from more than 300 previously infected patients.

Overall accuracy was 82 percent in the latter setting, with an overall sensitivity (how often a test correctly generates a positive result) of 57.6 percent and an overall specificity (how often a test correctly generates a negative result) of 99.5 percent.

In other words, the test was able to detect COVID-19 infections in about six out of 10 people, and it was nearly perfect in determining when an infection was not present. The test was more sensitive in patients with higher viral loads, positively identifying an infection in about seven out of 10 people.

The authors say the test -- quicker, cheaper and less complicated but not as sensitive as reverse transcription-polymerase chain reaction (RT-PCR) assays, which ID the virus based on its genetic material -- could be used to help screen patients during peak periods of the pandemic. Eventually, it could also be especially useful in screening higher-risk populations such as healthcare workers, they said.

The COVID-19 Ag Respi-Strip® test was developed by Belgian company Coris BioConcept, which specializes in rapid diagnostic kits for detecting respiratory and gastrointestinal pathogens like viruses and bacteria.

The test from Coris BioConcept is a type of immunochromatographic assay, or lateral flow test, which detects the presence or absence of a particular substance. Most people may be familiar with another type of lateral flow assay -- a pregnancy test.

In the case of the COVID-19 Ag Respi-Strip, the antigen test uses a sample from a nasopharyngeal swab, which looks like a long, flexible Q-tip that enters through one nostril and extends down the nasal passage close to a person's outer ear.

An antigen test works by looking for proteins on the surface of the virus. Coris BioConcept partly based the test on previous virology research on SARS-CoV-1, which caused the 2002-03 SARS epidemic. In fact, the two are so similar that the COVID-19 Ag Respi-Strip cannot differentiate between SARS-CoV-1 and -2.

The authors estimate the 15-minute antigen test, which can be conducted at point-of-care facilities following a few user-friendly protocols, could reduce the number of laboratory tests using RT-PCR by more than 13 percent.

They also note that the special material, reagents and trained personnel needed to perform molecular tests limits the number of assays that can be done quickly and at scale, especially in poorer countries.

"A major usefulness of the COVID-19 Ag Respi-Strip test would be in the low- and middle income countries, where molecular assays are available in very few laboratories, mainly only in capital cities," according to the authors.

They warn, however, that COVID-19 Ag Respi-Strip is not intended to be a stand-alone test but used as part of a broader testing strategy.

Millions of people around the world use acid suppressants called proton pump inhibitors for conditions like heartburn, gastritis and stomach ulcers. Researchers at Karolinska Institutet in Sweden now report that how the long-term use of these drugs could increase the risk of developing dementia. Their results are published in the journal Alzheimer's & Dementia.

"We've been able to show that proton pump inhibitors affect the synthesis of the neurotransmitter acetylcholine, which plays a significant part in conditions such as Alzheimer's disease," says Taher Darreh-Shori, senior researcher at the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet. "Since there's no effective treatment for the disease, it's important to avoid risk factors. We therefore want to draw attention to this so that the drugs aren't used needlessly for a long time."

Proton pump inhibitors (PPIs) work by blocking the pumps that transport acidic hydrogen ions from the cells that form the mucosa. When the pumps are out of action, there is a reduction in acid and, ultimately, the corrosive damage it does to tissue. Population studies have previously shown higher rates of dementia in people using PPIs (see background material), but what form such a connection could take has remained unknown - until now.

First, the researchers used 3D computer simulations to examine how six PPI variants based on different active substances interacted with an enzyme called choline acetyletransferase, the function of which is to synthesize the neurotransmitter acetylcholine. As a neurotransmitter, acetylcholine is needed for passing signals among nerve cells, but this only works if enough of the substance is produced. The simulations showed that all the tested drugs were able to bind with the enzyme.

The researchers then analysed the effect of this binding. They found that all the drugs inhibited the enzyme, resulting in a reduced production of acetylcholine, where the stronger the binding, the stronger the inhibitory effect. Drugs based on the active substances omeprazole, esomeprazole, tenatoprazole and rabeprazole had the greatest affinity and were therefore the strongest inhibitors of the enzyme, while the variants pantoprazole and lansoprazole were the weakest (see illustration).

Complementary studies are now needed to examine whether these laboratory observations represent what occurs in the body. However, Darreh-Shori is already advising against the overuse of PPIs.

"Special care should be taken with the more elderly patients and those already diagnosed with dementia," he says. "The same also applies to patients with muscle weakness diseases such as ALS, as acetylcholine is an essential motor neurotransmitter. In such cases, doctors should use the drugs that have the weakest effect and prescribe them at lowest dose and for as short a time as possible."

"I would, however, like to stress that the correct use of the drugs is safe also in the elderly, as long as the drugs are used for a limited time and when they're really needed, as our nervous system is pretty flexible when it comes to tolerating short-term impact," he adds.

The research was financed by several bodies, including the Alzheimer's Association (USA), the Swedish Research Council, the Loo & Hans Osterman Foundation and Karolinska Institutet. See the scientific article for a full list of financiers.

Most everyone knows that humid heat is harder to handle than the "dry" kind. And recently, some scientists have projected that later in the century, in parts of the tropics and subtropics, warming climate could cause combined heat and humidity to reach levels rarely if ever experienced before by humans. Such conditions would ravage economies, and possibly even surpass the physiological limits of human survival.

According to a new study, the projections are wrong: such conditions are already appearing. The study identifies thousands of previously rare or unprecedented bouts of extreme heat and humidity in Asia, Africa, Australia, South America and North America, including in the U.S. Gulf Coast region. Along the Persian Gulf, researchers spotted more than a dozen recent brief outbreaks surpassing the theoretical human survivability limit. The outbreaks have so far been confined to localized areas and lasted just hours, but they are increasing in frequency and intensity, say the authors. The study appears this week in the journal Science Advances.

"Previous studies projected that this would happen several decades from now, but this shows it's happening right now," said lead author Colin Raymond, who did the research as a PhD. student at Columbia University's Lamont-Doherty Earth Observatory. "The times these events last will increase, and the areas they affect will grow in direct correlation with global warming."

Analyzing data from weather stations from 1979 to 2017, the authors found that extreme heat/humidity combinations doubled over the study period. Repeated incidents appeared in much of India, Bangladesh and Pakistan; northwestern Australia; and along the coasts of the Red Sea and Mexico's Gulf of California. The highest, potentially fatal, readings, were spotted 14 times in the cities of Dhahran/Damman, Saudi Arabia; Doha, Qatar; and Ras Al Khaimah, United Arab Emirates, which have combined populations of over 3 million. Parts of southeast Asia, southern China, subtropical Africa and the Caribbean were also hit.

The southeastern United States saw extreme conditions dozens of times, mainly near the Gulf Coast in east Texas, Louisiana, Mississippi, Alabama and the Florida Panhandle. The worst spots: New Orleans and Biloxi, Miss. Such conditions also reached inland into Arkansas and along the southeastern coastal plain.

Not surprisingly, incidents tended to cluster on coastlines along confined seas, gulfs and straits, where evaporating seawater provides abundant moisture to be sucked up by hot air. In some areas further inland, moisture-laden monsoon winds or wide areas of crop irrigation appear to play the same role.

Prior climate studies failed to recognize most past incidents because climate researchers usually look at averages of heat and humidity measured over large areas and over several hours at a time. Raymond and his colleagues instead drilled directly into hourly data from 7,877 individual weather stations, allowing them to pinpoint shorter-lived bouts affecting smaller areas.

Humidity worsens the effects of heat because humans cool their bodies by sweating; water expelled through the skin removes excess body heat, and when it evaporates, it carries that heat away. The process works nicely in deserts, but less well in humid regions, where the air is already too laden with moisture to take on much more. Evaporation of sweat slows. In the most extreme instances, it could stop. In that case, unless one can retreat to an air-conditioned room, the body's core heats beyond its narrow survivable range, and organs begin to fail. Even a strong, physically fit person resting in the shade with no clothes and unlimited access to drinking water would die within hours.

Meteorologists measure the heat/humidity effect on the so-called "wet bulb" Centigrade scale; in the United States, these readings are often translated into "heat index" or "real-feel" Fahrenheit readings. Prior studies suggest that even the strongest, best-adapted people cannot carry out normal outdoor activities when the wet bulb hits 32 C, equivalent to a heat index of 132 F. Most others would crumble well before that. A reading of 35 -- the peak briefly reached in the Persian Gulf cities -- is considered the theoretical survivability limit. That translates roughly to a heat index of 160 F. (The heat index actually ends at 127 F, so these readings are literally off the charts.) "It's hard to exaggerate the effects of anything that gets into the 30s," said Raymond.

The study found that worldwide, wet-bulb readings approaching or exceeding 30C on the wet bulb have doubled since 1979. The number of readings of 31-- previously believed to occur only rarely -- totaled around 1,000. Readings of 33 -- previously thought to be almost nonexistent -- totaled around 80.

A heat wave that struck much of the United States last July maxed out at about 30C on the wet bulb, translating into heat indexes approaching 115 F in places; the highest was 122 F, in Baltimore, Md., and a similar wave hit in August. The waves paralyzed communities and led to at least a half-dozen deaths, including those of an air-conditioning technician in Phoenix, Az., and former National Football League lineman Mitch Petrus, who died in Arkansas while working outside.

It was a modest toll; heat-related illnesses already kill more U.S. residents than any other weather-related hazard including cold, hurricanes or floods. An investigation last year by the website InsideClimate News revealed that cases of heat stroke or heat exhaustion among U.S. troops on domestic bases grew 60 percent from 2008 to 2018. Seventeen soldiers died, almost all in the muggy U.S. Southeast. High-humidity heat waves in Russia and Europe, where far fewer people have air conditioning, have killed tens of thousands.

"We may be closer to a real tipping point on this than we think," said Radley Horton, a Lamont-Doherty research scientist and coauthor of the paper. Horton coauthored a 2017 paper projecting that such conditions would not take hold until later in the century.

While air conditioning may blunt the effects in the United States and some other wealthy countries, there are limits. Before the new study, one of the previously highest heat/humidity events ever reported was in the Iranian city of Bandar Mahshahr, which almost reached a 35C wet-bulb reading on July 31, 2015. There were no known deaths; residents reported staying inside air-conditioned vehicles and buildings, and showering after brief sojourns outside. But Horton points out that if people are increasingly forced indoors for longer periods, farming, commerce and other activities could potentially grind to a halt, even in rich nations-a lesson already brought home by the collapse of economies in the face of the novel coronavirus.

In any case, many people in the poorer countries most at risk do not have electricity, never mind air conditioning. There, many rely on subsistence farming requiring daily outdoor heavy labor. These facts could make some of the most affected areas basically uninhabitable, says Horton.

Kristina Dahl, a climatologist at the Union of Concerned Scientists who led a study last year warning of increasing future heat and humidity in the United States, said the new paper shows "how close communities around the world are to the limits." She added that some localities may already be seeing conditions worse than the study suggests, because weather stations do not necessarily pick up hot spots in dense city neighborhoods built with heat-trapping concrete and pavement.

Steven Sherwood, a climatologist at the Australia's University of New South Wales, said, "These measurements imply that some areas of Earth are much closer than expected to attaining sustained intolerable heat. It was previously believed we had a much larger margin of safety."

The study was coauthored by Tom Matthews, a lecturer in climate science at Loughborough University in the United Kingdom. Colin Raymond is now a postdoctoral researcher at NASA's Jet Propulsion Laboratory.

Flies that cannot take to the air respond by sleeping more as they learn to adapt to their flightlessness, according to a study from Washington University School of Medicine in St. Louis. The findings, published May 8 in Science Advances, suggest that sleep may be an evolutionary tool that helps animals adapt to challenging new situations.

"We know that sleep is involved in creativity and insight," said senior author Paul Shaw, PhD, a professor of neuroscience. "Have you ever slept on a problem, and when you wake up you've found the answer? Anxiety keeps people up at night, but if you find yourself in a dangerous environment, or in a situation that you don't know how to deal with, sleep may be exactly what you need to respond to it effectively."

Fruit flies' sleep looks a lot like people's. Baby flies need a lot of sleep, but as they get older, their need for sleep diminishes. Flies become more alert with caffeine and drowsier with antihistamines. And if you keep a fly awake one day, it will sleep more the next.

These similarities suggest that the sleep habits of flies might shed light on the sleep habits of people. To explore the relationship between challenging circumstances and sleep, Shaw and staff scientist and first author Krishna Melnattur, PhD, took away flies' ability to fly.

Baby flies must expand their wings in the first half hour or so after emerging from pupal cases, or their wings will not develop properly. The researchers placed some newly emerged flies in tiny containers so they could not expand their wings, and they genetically modified other flies so that the insects' wings failed to expand. Both scenarios rendered the young flies permanently flightless. The researchers also grounded older flies by disabling their wings. In all cases, faced with the inability to fly, the animals slept more than usual.

In subsequent experiments, the researchers traced the neurological circuit that signals to the brain that the wings aren't functioning and triggers the impulse to sleep more.

"When we identified the neurons that were activated when we cut or glued the wings of adult flies, they turned out to be the same neurons involved in the normal developmental process of wing expansion after emergence," Melnattur said.

The fact that wing injury and normal wing development are linked to sleep through the same neurological circuitry makes sense from an evolutionary standpoint, the researchers said. The circuit is active in young flies because their developing brains need sleep as the animals expand their wings, learn to fly and begin to navigate the world around them.

"And then the whole circuit can get reactivated later in life when something happens that forces a fly to adapt to a new normal," Shaw said. "Suddenly, its brain needs to be as flexible as when it was young. It can no longer fly, but it still needs to get food, it needs to compete for mates, it needs to avoid dying. We think that sleep amplifies the brain plasticity the fly needs to survive."

Shaw and Melnattur are planning experiments to determine whether increased sleep helps flightless flies survive. Their findings also may provide clues to why some people sleep more than others and why some sleep disorders arise.

"There's huge variation in sleep time among people," Shaw said. "Some people need five hours a night; some need nine. Sleep is an ancient process, and we've evolved mechanisms to change our sleep-wake balance to help us meet our needs. If these mechanisms get inappropriately activated, say by a traumatic event that triggers post-traumatic stress disorder, it can create a situation in which you're sleeping too much or too little and it's no longer matching up with your needs, and then you have a sleep disorder."