Archive for the ‘Uncategorized’ Category

Within four hours of a traumatic experience, certain physiological markers—namely, sweating—are higher in people who go on to develop posttraumatic stress disorder (PTSD), according to a new study by a researcher at Case Western Reserve University and other institutions.

Around 90% of people who experience a traumatic event do not develop PTSD, according to existing data and research, making the medical community eager for better insights into the 10% who do—and for how to best treat these patients.

The study, conducted at Atlanta’s Grady Memorial Hospital, found that micro perspirations—detected non-invasively by a mobile device in an emergency department—can be plugged into a new mathematical model developed by the researchers to help predict who may be more at risk for developing PTSD.

The findings are especially important for targeting early treatment efforts and prevention of the disorder, said Alex Rothbaum, a pre-doctoral researcher in the Department of Psychological Sciences in the College of Arts and Sciences at Case Western Reserve.

“With PTSD, there is a need for more reliable and immediate patient information, especially in situations where research suggests people may underreport their own symptoms, such as with men, and those who live in violent neighborhoods or are on active duty,” said Rothbaum, a co-author of the study, which was published in the journal Chronic Stress.

“While skin is always secreting sweat, our method can discern meaningful, actionable information from perspirations too small for the naked eye to see,” he added.

The measurement differs from traditional practices to diagnose PTSD, which look for psychological differences in patients based on self-reported data and clusters of symptoms defined by the Diagnostic and Statistical Manual of Mental Disorders (often referred to as the DSM) published by the American Psychiatric Association.

“Eventually, this finding may help contribute to changes in how we diagnose and treat PTSD, pointing us toward which patients would do better in therapy, with medication, or a combination of the two—or no treatment at all,” said Rothbaum.

New testing device: less expensive, more accessible
Researchers hope the PTSD test can become available and standard in emergency departments, aided by the recent development of a practical and inexpensive device that can plug into common tablets and can measure “skin conductance response”—a measure of sweating.

Before, such tests could only be conducted on a large stand-alone machine costing upwards of $10,000. While the new device lacks the sensitivity of its more expensive counterpart, the readings it provides can be used to determine who should continue with additional testing and who is not at risk for developing PTSD.

The study—which included nearly 100 patients—was prompted, in part, by recent research showing the ineffectiveness of current methods practiced with patients immediately after traumas, known as critical incident stress debriefing and psychological debriefing.

Both the new method and model created by researchers will need to be further validated by a larger study underway with a National Institutes of Health grant.

The research
The study was co-authored with researchers at Emory University School of Medicine: Rebecca Hinrichs, Sanne J. H. van Rooij, Jennifer Stevens, Jessica Maples-Keller and Barbara O. Rothbaum; Vasiliki Michopoulos of Emory and Yerkes National Primate Research Center; Katharina Schultebraucks and Isaac Galatzer-Levy of New York University School of Medicine; Sterling Winters of Wayne State University; Tanja Jovanovic of Emory and Wayne State; and Kerry J. Ressler of Emory and Harvard/ McLean Hospital.

The research was supported by the National Institute of Mental Health and a Brain and Behavior Research Foundation NARSAD Independent Investigator Award.

Sweating is a clue into who develops PTSD—and who doesn’t

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A 7-year-old boy complaining of jaw pain was found to have 526 teeth inside his mouth, according to the hospital in India where he was treated.

The boy was admitted last month in the southern city of Chennai because of swelling and pain near his molars in his lower right jaw.

When doctors scanned and x-rayed his mouth, they found a sac embedded in his lower jaw filled with “abnormal teeth,” Dr. Prathiba Ramani, the head of Oral and Maxillofacial Pathology at Saveetha Dental College and Hospital, told CNN.

While the surgery to remove the teeth took place last month, doctors needed time to individually examine each tooth before they could confirm their findings.

After discovering the sac, two surgeons removed it from the boy’s mouth. Then Ramani’s team took four to five hours to empty the sac to confirm its contents and discovered the hundreds of teeth.

“There were a total of 526 teeth ranging from 0.1 millimeters (.004 inches) to 15 millimeters (0.6 inches). Even the smallest piece had a crown, root and enamel coat indicating it was a tooth,” she said.

The boy was released three days after the surgery and is expected to make a full recovery, Ramani said.

Ramani said the boy was suffering from a very rare condition called compound composite odontoma. She said what caused the condition is unclear, but it could be genetic or it could be due to environmental factors like radiation.

The boy actually may have had the extra teeth for some time. His parents told doctors that they had noticed swelling in his jaw when he was as young as 3, but they couldn’t do much about it because he would not stay still or allow doctors to examine him.

Dr. P. Senthilnathan, head of the hospital’s Oral and Maxillofacial Surgery Department and one of two surgeons who operated on the boy, detailed the procedure to CNN.

“Under general anesthesia, we drilled into the jaw from the top,” he said. “We did not break the bone from the sides, meaning reconstruction surgery was not required. The sac was removed. You can think of it as a kind of balloon with small pieces inside.”

Dr. Senthilnathan said the discovery showed it was important to seek treatment for dental issues as early as possible.

Awareness about dental and oral health was improving, he said, though access in rural areas remained problematic.

“Earlier, things like not as many dentists, lack of education, poverty meant that there was not as much awareness. These problems are still there.

“You can see people in cities have better awareness but people who are in rural areas are not as educated or able to afford good dental health.”

In Ravindrath’s case, all has turned out well; the boy now has a healthy count of 21 teeth, Dr. Senthilnathan said.

Doctors find 526 teeth in boy’s mouth after he complains of jaw pain


Frank Keutsch, Zhen Dai and David Keith (left to right) in Keutsch’s laboratory at Harvard University.

Zhen Dai holds up a small glass tube coated with a white powder: calcium carbonate, a ubiquitous compound used in everything from paper and cement to toothpaste and cake mixes. Plop a tablet of it into water, and the result is a fizzy antacid that calms the stomach. The question for Dai, a doctoral candidate at Harvard University in Cambridge, Massachusetts, and her colleagues is whether this innocuous substance could also help humanity to relieve the ultimate case of indigestion: global warming caused by greenhouse-gas pollution.

The idea is simple: spray a bunch of particles into the stratosphere, and they will cool the planet by reflecting some of the Sun’s rays back into space. Scientists have already witnessed the principle in action. When Mount Pinatubo erupted in the Philippines in 1991, it injected an estimated 20 million tonnes of sulfur dioxide into the stratosphere — the atmospheric layer that stretches from about 10 to 50 kilometres above Earth’s surface. The eruption created a haze of sulfate particles that cooled the planet by around 0.5 °C. For about 18 months, Earth’s average temperature returned to what it was before the arrival of the steam engine.

The idea that humans might turn down Earth’s thermostat by similar, artificial means is several decades old. It fits into a broader class of planet-cooling schemes known as geoengineering that have long generated intense debate and, in some cases, fear.

Researchers have largely restricted their work on such tactics to computer models. Among the concerns is that dimming the Sun could backfire, or at least strongly disadvantage some areas of the world by, for example, robbing crops of sunlight and shifting rain patterns.

But as emissions continue to rise and climate projections remain dire, conversations about geoengineering research are starting to gain more traction among scientists, policymakers and some environmentalists. That’s because many researchers have come to the alarming conclusion that the only way to prevent the severe impacts of global warming will be either to suck massive amounts of carbon dioxide out of the atmosphere or to cool the planet artificially. Or, perhaps more likely, both.

If all goes as planned, the Harvard team will be the first in the world to move solar geoengineering out of the lab and into the stratosphere, with a project called the Stratospheric Controlled Perturbation Experiment (SCoPEx). The first phase — a US$3-million test involving two flights of a steerable balloon 20 kilometres above the southwest United States — could launch as early as the first half of 2019. Once in place, the experiment would release small plumes of calcium carbonate, each of around 100 grams, roughly equivalent to the amount found in an average bottle of off-the-shelf antacid. The balloon would then turn around to observe how the particles disperse.

The test itself is extremely modest. Dai, whose doctoral work over the past four years has involved building a tabletop device to simulate and measure chemical reactions in the stratosphere in advance of the experiment, does not stress about concerns over such research. “I’m studying a chemical substance,” she says. “It’s not like it’s a nuclear bomb.”

Nevertheless, the experiment will be the first to fly under the banner of solar geoengineering. And so it is under intense scrutiny, including from some environmental groups, who say such efforts are a dangerous distraction from addressing the only permanent solution to climate change: reducing greenhouse-gas emissions. The scientific outcome of SCoPEx doesn’t really matter, says Jim Thomas, co-executive director of the ETC Group, an environmental advocacy organization in Val-David, near Montreal, Canada, that opposes geoengineering: “This is as much an experiment in changing social norms and crossing a line as it is a science experiment.”

Aware of this attention, the team is moving slowly and is working to set up clear oversight for the experiment, in the form of an external advisory committee to review the project. Some say that such a framework, which could pave the way for future experiments, is even more important than the results of this one test. “SCoPEx is the first out of the gate, and it is triggering an important conversation about what independent guidance, advice and oversight should look like,” says Peter Frumhoff, chief climate scientist at the Union of Concerned Scientists in Cambridge, Massachusetts, and a member of an independent panel that has been charged with selecting the head of the advisory committee. “Getting it done right is far more important than getting it done quickly.”

Joining forces
In many ways, the stratosphere is an ideal place to try to make the atmosphere more reflective. Small particles injected there can spread around the globe and stay aloft for two years or more. If placed strategically and regularly in both hemispheres, they could create a relatively uniform blanket that would shield the entire planet (see ‘Global intervention’). The process does not have to be wildly expensive; in a report last month, the Intergovernmental Panel on Climate Change suggested that a fleet of high-flying aircraft could deposit enough sulfur to offset roughly 1.5 °C of warming for around $1 billion to $10 billion per year1.

Most of the solar geoengineering research so far has focused on sulfur dioxide, the same substance released by Mount Pinatubo. But sulfur might not be the best candidate. In addition to cooling the planet, the aerosols generated in that eruption sped up the rate at which chlorofluorocarbons deplete the ozone layer, which shields the planet from the Sun’s harmful ultraviolet radiation. Sulfate aerosols are also warmed by the Sun, enough to potentially affect the movement of moisture and even alter the jet stream. “There are all of these downstream effects that we don’t fully understand,” says Frank Keutsch, an atmospheric chemist at Harvard and SCoPEx’s principal investigator.

The SCoPEx team’s initial stratospheric experiments will focus on calcium carbonate, which is expected to absorb less heat than sulfates and to have less impact on ozone. But textbook answers — and even Dai’s tabletop device — can’t capture the full picture. “We actually don’t know what it would do, because it doesn’t exist in the stratosphere,” Keutsch says. “That sets up a red flag.”

SCoPEx aims to gather real-world data to sort this out. The experiment began as a partnership between atmospheric chemist James Anderson of Harvard and experimental physicist David Keith, who moved to the university in 2011. Keith has been investigating a variety of geoengineering options off and on for more than 25 years. In 2009, while at the University of Calgary in Canada, he founded the company Carbon Engineering, in Squamish, which is working to commercialize technology to remove carbon dioxide from the atmosphere. After joining Harvard, Keith used research funding he had received from Microsoft co-founder Bill Gates, to begin planning the experiment.

Keutsch, who got involved later, is not a climate scientist and is at best a reluctant geoengineer. But he worries about where humanity is heading, and what that means for his children’s future. When he saw Keith talk about the SCoPEx idea at a conference after starting at Harvard in 2015, he says his initial reaction was that the idea was “totally insane”. Then he decided it was time to engage. “I asked myself, an atmospheric chemist, what can I do?” He joined forces with Keith and Anderson, and has since taken the lead on the experimental work.

An eye on the sky
Already, SCoPEx has moved farther along than earlier solar geoengineering efforts. The UK Stratospheric Particle Injection for Climate Engineering experiment, which sought to spray water 1 kilometre into the atmosphere, was cancelled in 2012 in part because scientists had applied for patents on an apparatus that could ultimately affect every human on the planet. (Keith says there will be no patents on any technologies involved in the SCoPEx project.) And US researchers with the Marine Cloud Brightening Project, which aims to spray saltwater droplets into the lower atmosphere to increase the reflectivity of ocean clouds, have been trying to raise money for the project for nearly a decade.

Although SCoPEx could be the first solar geoengineering experiment to fly, Keith says other projects that have not branded themselves as such have already provided useful data. In 2011, for example, the Eastern Pacific Emitted Aerosol Cloud Experiment pumped smoke into the lower atmosphere to mimic pollution from ships, which can cause clouds to brighten by capturing more water vapour. The test was used to study the effect on marine clouds, but the results had a direct bearing on geoengineering science: the brighter clouds produced a cooling effect 50 times greater than the warming effect of the carbon emissions from the researchers’ ship2.

Keith says that the Harvard team has yet to encounter public protests or any direct opposition — aside from the occasional conspiracy theorist. The challenge facing researchers, he says, stems more from a fear among science-funding agencies that investing in geoengineering will lead to protests by environmentalists.

To help advance the field, Keith set a goal in 2016 of raising $20 million to support a formal research programme that would cover not just the experimental work, but also research into modelling, governance and ethics. He has raised around $12 million so far, mostly from philanthropic sources such as Gates; the pot provides funding to dozens of people, largely on a part-time basis.

Keith and Keutsch also want an external advisory committee to review SCoPEx before it flies. The committee, which is still to be selected, will report to the dean of engineering and the vice-provost for research at Harvard. “We see this as part of a process to build broader support for research on this topic,” Keith says.

Keutsch is looking forward to having the guidance of an external group, and hopes that it can provide clarity on how tests such as his should proceed. “This is a much more politically challenging experiment than I had anticipated,” he says. “I was a little naive.”

SCoPEx faces technical challenges, too. It must spray particles of the right size: the team calculates that those with a diameter of about 0.5 micrometres should disperse and reflect sunlight well. The balloon must also be able to reverse its course in the thin air so that it can pass through its own wake. Assuming the team is able to find the calcium carbonate plume — and there is no guarantee that they can — SCoPEx needs instruments that can analyse the particles and, it is hoped, carry samples back to Earth.

“It’s going to be a hard experiment, and it may not work,” says David Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado. In the hope that it will, Fahey’s team has provided SCoPEx with a lightweight instrument that can reliably measure the size and number of particles that are released. The balloon will also be equipped with a laser device that can monitor the plume from afar. Other equipment that could collect information on the level of moisture and ozone in the stratosphere could fly on the balloon as well.

Up to the stratosphere
Keutsch and Keith are still working out some of the technical details. Plans with one balloon company fell through, so they are now working with a second. And an independent team of engineers in California is working on options for the sprayer. To simplify things, the SCoPEx group plans to fly the balloon during the spring or autumn, when stratospheric winds shift direction and — for a brief period — calm down, which will make it easier to track the plume.

For all of these reasons, Keutsch characterizes the first flight as an engineering test, mainly intended to demonstrate that everything works as it should. The team is ready to spray calcium carbonate particles, but could instead use salt water to test the sprayer if the advisory committee objects.

Keith still thinks that sulfate aerosols might ultimately be the best choice for solar geoengineering, if only because there has been more research about their impact. He says that the possibility of sulfates enhancing ozone depletion should become less of a concern in the future, as efforts to restore the ozone layer through pollutant reductions continue. Nevertheless, his main hope is to establish an experimental programme in which scientists can explore different aspects of solar geoengineering.

There are a lot of outstanding questions. Some researchers have suggested that solar geoengineering could alter precipitation patterns and even lead to more droughts in some regions. Others warn that one of the possible benefits of solar geoengineering — maintaining crop yields by protecting them from heat stress — might not come to pass. In a study published in August, researchers found that yields of maize (corn), soya, rice and wheat3 fell after two volcanic eruptions, Mount Pinatubo in 1991 and El Chichón in Mexico in 1982, dimmed the skies. Such reductions could be enough to cancel out any potential gains in the future.

Keith says the science so far suggests that the benefits could well outweigh the potential negative consequences, particularly compared with a world in which warming goes unchecked. The commonly cited drawback is that shielding the Sun doesn’t affect emissions, so greenhouse-gas levels would continue to rise and the ocean would grow even more acidic. But he suggests that solar geoengineering could reduce the amount of carbon that would otherwise end up in the atmosphere, including by minimizing the loss of permafrost, promoting forest growth and reducing the need to cool buildings. In an as-yet-unpublished analysis of precipitation and temperature extremes using a high-resolution climate model, Keith and others found that nearly all regions of the world would benefit from a moderate solar geoengineering programme. “Despite all of the concerns, we can’t find any areas that would be definitely worse off,” he says. “If solar geoengineering is as good as what is shown in these models, it would be crazy not to take it seriously.”

There is still widespread uncertainty about the state of the science and the assumptions in the models — including the idea that humanity could come together to establish, maintain and then eventually dismantle a well-designed geoengineering programme while tackling the underlying problem of emissions. Still, prominent organizations, including the UK Royal Society and the US National Academies of Sciences, Engineering, and Medicine, have called for more research. In October, the academies launched a project that will attempt to provide a blueprint for such a programme.

Some organizations are already trying to promote discussions among policymakers and government officials at the international level. The Solar Radiation Management Governance Initiative is holding workshops across the global south, for instance. And Janos Pasztor, who handled climate issues under former UN secretary-general Ban Ki-moon, has been talking to high-level government officials around the world in his role as head of the Carnegie Climate Geoengineering Governance Initiative, a non-profit organization based in New York. “Governments need to engage in this discussion and to understand these issues,” Pasztor says. “They need to understand the risks — not just the risks of doing it, but also the risks of not understanding and not knowing.”

One concern is that governments might one day panic over the consequences of global warming and rush forward with a haphazard solar-geoengineering programme, a distinct possibility given that the costs are cheap enough that many countries, and perhaps even a few individuals, could probably afford to go it alone. These and other questions arose earlier this month in Quito, Ecuador, at the annual summit of the Montreal Protocol, which governs chemicals that damage the stratospheric ozone layer. Several countries called for a scientific assessment of the potential effects that solar geoengineering could have on the ozone layer, and on the stratosphere more broadly.

If the world gets serious about geoengineering, Fahey says that there are plenty of sophisticated experiments that researchers could do using satellites and high-flying aircraft. But for now, he says, SCoPEx will be valuable — if only because it pushes the conversation forward. “Not talking about geoengineering is the greatest mistake we can make right now.”

Nature 563, 613-615 (2018)

doi: 10.1038/d41586-018-07533-4

BY MARKHAM HEID

If you’re the type who dons new duds without washing them first, there’s a chance you may pay a price for it a few days later. A red, itchy, painful price.

Allergic contact dermatitis is an immune system-related reaction to an allergen that has come into contact with your skin. It causes a delayed reaction: a rash that appears a few days after exposure, and then can last for weeks. “When we see allergic contact dermatitis from clothing, it’s usually from disperse dyes,” says Dr. Susan Nedorost, a professor of dermatology at Case Western Reserve University and director of the dermatitis program at University Hospitals Cleveland Medical Center. Disperse dyes are primarily used in synthetic clothing materials like polyester and nylon, Nedorost says. And they may be present at higher levels in a brand-new, unwashed article of clothing.

Nedorost says that sweating and friction can cause disperse dye to leach out of clothing. Synthetic workout gear—the shiny, stretchy, water-repelling materials that are so popular nowadays—are often the culprit when she treats people for allergic contact dermatitis. “If a patient comes in and has a rash around the back of the neck and along their sides around their armpits, the first question I ask is what they wear when they work out,” she says.

It’s not clear how common disperse-dye allergies are among the general public. But there is one way to limit your risk for bad reactions: “By washing new clothing, you might remove a little extra dye and so have a lower exposure,” Nedorost says.

In very rare cases, taking this step could even prevent the development of a new allergy. If enough of the dye leached onto a skinned knee or other open wound, she says, that could activate the immune system and create a lasting sensitivity.

Allergic rashes aren’t the only health issue associated with clothing chemicals. In a 2014 study, a group of researchers from Stockholm University in Sweden tested 31 clothing samples purchased at retail stores, and that were “diverse in color, material, brand, country of manufacture, and price, and intended for a broad market.” They found a type of chemical compound called “quinoline” (or one of its derivatives) in 29 of the 31 samples, and the levels of this chemical tended to be especially high in polyester garments. Quinoline is used in clothing dyes, and the U.S. Environmental Protection Agency has classified it as a “possible human carcinogen” based on some studies linking it to “tumor-initiating activity” in mice—though the agency also states that no human studies have been conducted to assess the cancer-causing potential of quinoline.

Ulrika Nilsson, a member of the Stockholm University group and a professor of analytical chemistry, also calls out nitroanilines and benzothiazoles, two more chemical compounds that turn up in clothing and that lab and animal evidence has linked to potential adverse health effects, including cancer. While some of these chemicals may remain locked away in the fibers of your clothing, others may slowly work their way out onto your skin or into the air you breathe as your clothing ages and degrades. Unfortunately, Nilsson says, “these chemicals are so far not well studied regarding skin uptake or related health effects” in humans, so it’s not clear whether exposure to these chemicals in your clothing could make you sick.

David Andrews, a senior scientist with the nonprofit Environmental Working Group who has investigated the use of chemicals in the textile industry, says clothing is often treated with stain-repellents, color-fasteners, anti-wrinkle agents, softness-enhancers, and any number of other chemical treatments. Clothing manufacturers don’t have to disclose any of these to customers, and many of the chemicals, including a popular type of waterproofing chemical called fluorosurfactants (often referred to as PFAS), have little or no research backing their safety. Not only could these chemicals pose health risks to people, but they also end up in the air and water supplies, where they could do further harm.

“It’s always in your best interest to wash clothing before wearing,” he says. Nilsson agrees, saying washing new clothes “reduces the content of chemicals,” especially residual chemicals that may be left over from the manufacturing process.

But even so, that doesn’t prevent clothing chemicals from breaking down and leaching out of your clothing and onto your skin or into the air your breathe. And, unfortunately, there’s no easy way to point people toward clothing items that may be safer, Andrews says. Some of the research on clothing suggests synthetic materials may be treated with more chemicals than natural fibers such as cotton. But there’s really no label indicator or certification that signals a garment is chemical-free, he says.

“What’s maddening for the consumer is that you buy a shirt that says ‘100% cotton,’ and yet you’re given no information about any of the chemicals or additives that have been used.”

https://time.com/5631818/wash-new-clothes/

By Michael Marshall

Blobs of simple carbon-based compounds could have been the precursors to the first living cells. A new study suggests that such droplets could have formed quickly and easily on the young Earth.

“We were able to find these interesting microdroplet structures that could be synthesised from prebiotically available resources,” says Tony Jia of the Tokyo Institute of Technology in Japan. “Maybe they weren’t the direct precursors to modern cells, but perhaps they could have had some effect or had a role in the emergence of initial life.”

All modern cells are surrounded by an outer wall called a membrane, which is made of long chain-like molecules called lipids. Given the ubiquity of these membranes, many researchers studying how life began have made simple membrane-lined spheres, which they say could mimic the first simple cells.

The droplets Jia and his colleagues made are different. “They don’t have an outer layer,” says Jia. “In that sense they’re membrane-less.”

The first cells?
The team made them from simple chemicals called alpha-hydroxy acids. These are made by the same processes that create amino acids, suggesting they were present on the early Earth, says team member Kuhan Chandru of the National University of Malaysia. “You can find them in meteorites as well.” He showed in 2018 that alpha-hydroxy acids link up to form complex molecules at a wide range of temperatures.

In the new study, the team simply dissolved the acids in water, then left them to dry out at 80 °C for a week – mimicking the conditions near a hot volcanic pond.

The acids turned into a thick jelly, because they had again formed complex molecules. When the researchers added water, the jelly formed hundreds of droplets a few micrometres across. Further experiments showed that crucial biological molecules, including protein and RNA, could enter the droplets and still perform their functions.

Cells without walls
Membrane-less droplets were a key element of the first popular hypothesis for life’s origin, which was set out by Russian biologist Alexander Oparin in the 1920s. However, the idea fell out of favour when it emerged that all cells have membranes.

The idea is now being re-assessed, says Kate Adamala of the University of Minnesota in Minneapolis. She suspects that life went through a “membrane-less stage” and that membranes only arose later.

Both droplets and membrane-based cells are a container for life’s components. This is crucial, says Adamala, because it keeps all the parts together, creating an individual organism from what would otherwise be a mess of chemicals.

But membranes are such good barriers that the first cells would have struggled to get food in and waste out, Adamala argues. So at the very beginning, membrane-less droplets would be better. “You don’t have to be shut off from the environment, because those droplets are permeable and you can have things diffusing in and out of them.”

Journal reference: PNAS, DOI: 10.1073/pnas.1902336116

Read more: https://www.newscientist.com/article/2210671-early-life-on-earth-may-have-existed-as-miniature-droplets-of-jelly/#ixzz5uVl0RAI6

by Ed Cara

People who only occasionally fall down an internet rabbit hole on their smartphones late at night might be able to rest easier—at least according to the results of a new study in mice. Researchers found that short bursts of light exposure at night won’t necessarily disrupt your internal clock, including sleep habits.

The researchers used mice to study the circadian rhythm. In both mice and humans, the circadian rhythm is primarily controlled by the brain’s suprachiasmatic nucleus (SCN), a tiny region found in the hypothalamus. One crucial aspect of the SCN involves regulating our sleep/wake, or light/dark, cycle. It’s long been thought that any kind of light exposure our eyes take in affects the SCN, and thus, can affect our sleep.

“Light information comes into the SCN, and that’s what synchronizes all of the body’s clocks to the light/dark cycle,” said lead author Tiffany Schmidt, a neurogeneticist at Northwestern, in a release from the university. “This one master pacemaker makes sure everything is in sync.”

Schmidt and her team wanted to test this long-held theory that the SCN responds to any light exposure. So they bred mice that had light-sensitive nerve cells in the retina that were only capable of communicating with the SCN. Then they exposed these mice to light for short periods of time.

Because mice, unlike people, are nocturnal, the light should have made them want to fall asleep. But they instead just carried out on with their day, sleeping and waking as normal. Their body temperature, which fluctuates predictably before, during, and after sleep, also followed the same pattern seen in mice with normal circadian rhythms.

What this could mean, according to the authors, is that our brains respond to acute light—meaning brief exposures to light—through a different neural pathway than what’s used for long periods of light exposure, a pathway that doesn’t involve the SCN.

“If these two effects—acute and long-term light exposure—were driven through the same pathway, then every minor light exposure would run the risk of completely shifting our body’s circadian rhythms,” Schmidt said.

The findings will be published this week in the journal eLife.

Mice and their brains aren’t a perfect proxy for people, obviously. And even if the same general principle does apply to us, Schmidt and her team say there’s no clear lead on where these other pathways could exist in the brain. And there’s undoubtedly a point where being exposed to light late at night too long or too often can start to affect our internal clock—even if where that point lies is still a mystery right now. There needs to be a lot much research studying these questions and others.

What is clear, the authors cautioned, is that chronic nighttime light exposure, and the disruptions to our sleep it can cause, can be very bad for health. In other words, don’t use this study as an excuse to start regularly binge-watching Netflix till 4 a.m.

“Light at the wrong time of day is now recognized as a carcinogen,” Schmidt said. “We want people to feel alert while they are exposed to light without getting the health risks that are associated with shifted circadian rhythms, such as diabetes, depression and even cancer.”

https://gizmodo.com/checking-your-phone-at-night-wont-necessarily-throw-off-1836603924


A mouse exploring one of the custom hologram generators used in the experiments at Stanford. By stimulating particular neurons, scientists were able to make engineered mice see visual patterns that weren’t there.

By Carl Zimmer

In a laboratory at the Stanford University School of Medicine, the mice are seeing things. And it’s not because they’ve been given drugs.

With new laser technology, scientists have triggered specific hallucinations in mice by switching on a few neurons with beams of light. The researchers reported the results on Thursday in the journal Science.

The technique promises to provide clues to how the billions of neurons in the brain make sense of the environment. Eventually the research also may lead to new treatments for psychological disorders, including uncontrollable hallucinations.

“This is spectacular — this is the dream,” said Lindsey Glickfeld, a neuroscientist at Duke University, who was not involved in the new study.

In the early 2000s, Dr. Karl Deisseroth, a psychiatrist and neuroscientist at Stanford, and other scientists engineered neurons in the brains of living mouse mice to switch on when exposed to a flash of light. The technique is known as optogenetics.

In the first wave of these experiments, researchers used light to learn how various types of neurons worked. But Dr. Deisseroth wanted to be able to pick out any individual cell in the brain and turn it on and off with light.

So he and his colleagues designed a new device: Instead of just bathing a mouse’s brain in light, it allowed the researchers to deliver tiny beams of red light that could strike dozens of individual brain neurons at once.

To try out this new system, Dr. Deisseroth and his colleagues focused on the brain’s perception of the visual world. When light enters the eyes — of a mouse or a human — it triggers nerve endings in the retina that send electrical impulses to the rear of the brain.

There, in a region called the visual cortex, neurons quickly detect edges and other patterns, which the brain then assembles into a picture of reality.

The scientists inserted two genes into neurons in the visual cortices of mice. One gene made the neurons sensitive to the red laser light. The other caused neurons to produce a green flash when turned on, letting the researchers track their activity in response to stimuli.

The engineered mice were shown pictures on a monitor. Some were of vertical stripes, others of horizontal stripes. Sometimes the stripes were bright, sometimes fuzzy. The researchers trained the mice to lick a pipe only if they saw vertical stripes. If they performed the test correctly, they were rewarded with a drop of water.

As the mice were shown images, thousands of neurons in their visual cortices flashed green. One population of cells switched on in response to vertical stripes; other neurons flipped on when the mice were shown horizontal ones.

The researchers picked a few dozen neurons from each group to target. They again showed the stripes to the mice, and this time they also fired light at the neurons from the corresponding group. Switching on the correct neurons helped the mice do better at recognizing stripes.

Then the researchers turned off the monitor, leaving the mice in darkness. Now the scientists switched on the neurons for horizontal and vertical stripes, without anything for the rodents to see. The mice responded by licking the pipe, as if they were actually seeing vertical stripes.

Anne Churchland, a neuroscientist at Cold Spring Harbor Laboratory who was not involved in the study, cautioned that this kind of experiment can’t reveal much about a mouse’s inner experience.

“It’s not like a creature can tell you, ‘Oh, wow, I saw a horizontal bar,’” she said.

Dr. Churchland said that it would take more research to better understand why the mice behaved as they did in response to the flashes of red light. Did they see the horizontal stripes more clearly, or were they less distracted by misleading signals?

One of the most remarkable results from the study came about when Dr. Deisseroth and his colleagues narrowed their beams of red light to fewer and fewer neurons. They kept getting the mice to lick the pipe as if they were seeing the vertical stripes.

In the end, the scientists found they could trigger the hallucinations by stimulating as few as two neurons. Thousands of other neurons in the visual cortex would follow the lead of those two cells, flashing green as they became active.

Clusters of neurons in the brain may be tuned so that they’re ready to fire at even a slight stimulus, Dr. Deisseroth and his colleagues concluded — like a snowbank poised to become an avalanche.

But it doesn’t take a fancy optogenetic device to make a few neurons fire. Even when they’re not receiving a stimulus, neurons sometimes just fire at random.

That raises a puzzle: If all it takes is two neurons, why are we not hallucinating all the time?

Maybe our brain wiring prevents it, Dr. Deisseroth said. When a neuron randomly fires, others may send signal it to quiet down.

Dr. Glickfeld speculated that attention may be crucial to triggering the avalanche of neuronal action only at the right times. “Attention allows you to ignore a lot of the background activity,” she said.

Dr. Deisseroth hopes to see what other hallucinations he can trigger with light. In other parts of the brain, he might be able to cause mice to perceive more complex images, such as the face of a cat. He might be able to coax neurons to create phantom sounds, or even phantom smells.

As a psychiatrist, Dr. Deisseroth has treated patients who have suffered from visual hallucinations. In his role as a neuroscientist, he’d like to find out more about how individual neurons give rise to these images — and how to stop them.

“Now we know where those cells are, what they look like, what their shape is,” he said. “In future work, we can get to know them in much more detail.”