When it comes to regrowing tails, neural stem cells are the key

Salamanders tails regenerate perfectly, whereas lizard tails grow back imperfectly and mouse tails don't grow back at all.

Cut off a salamander's tail and, in a few weeks, a near-perfect replacement grows. Do the same to a lizard and a new tail will regrow, but it won't be the same as the original. By comparing tail regeneration between the two animals, researchers at the University of Pittsburgh School of Medicine found that stem cells in the spinal cord are the ultimate limiting factor.

This finding, published this week in Proceedings of the National Academy of Sciences, answers the longstanding question of why tail regeneration is perfect in the salamander and imperfect in the lizard, and may serve as a stepping stone to understanding why mice can't regenerate their tails at all.

"The traditional animal model for regeneration is the salamander," said senior author Thomas P. Lozito, Ph.D., assistant professor in Pitt's Department of Orthopaedic Surgery, Center for Cellular and Molecular Engineering and the McGowan Institute for Regenerative Medicine. "Salamanders can regenerate a wide variety of tissues -- brain, heart, parts of their eyes, limbs, tails -- but they have whole classes of molecule types and tissues that just aren't found in mammals, so we really haven't been able to apply very much of what we found in the salamander to humans."

According to Lozito, if the goal is to translate regeneration research to non-regenerating species like humans, the lizard is a much better model than the salamander. Lizards are the closest relative to mammals that can regenerate an appendage, and they have a similar genome and biochemistry. But lizards cannot regenerate lost limbs at all, and their regenerated tails are much simpler than the originals.

"You can easily tell a lizard with a regenerated tail," Lozito said. "It doesn't get anything right. The scales are different; the color pattern is different, and then when you look inside the tail, all the tissues are different. There's no bone; the skeleton is completely cartilaginous, just tubes within tubes."

Understanding what separates perfect regeneration in the salamander from imperfect regeneration in the lizard lays the groundwork for bridging the gap to non-regenerating species, Lozito said.

Lozito's lizard of choice is the mourning gecko, which has several interesting properties, including a high tolerance for transplantation.

This feature allowed his team to take neural stem cells -- the nascent precursors of neurons and glia, the non-neuronal cells that surround them -- from the salamander and insert them into the lizard's regenerating tail stump. The goal was to see what holds back tail regeneration in the lizard: the biochemical environment or the lizard's native stem cells.

They found the transplanted salamander stem cells retained their ability to differentiate into multiple cell types, including neurons. By contrast, lizard neural stem cells could become only glial cells, which don't process the messages that direct movement and feeling.

"It was a nice surprise," said lead author Aaron Sun, Ph.D., a Pitt physician-scientist trainee who completed part of his research in Lozito's lab. "And it goes to show that maybe the regenerative processes are still somewhat conserved."

But perhaps the most surprising observation, according to Sun, is that the traditionally described "neural stem cells" driving regeneration in the lizard are not "true" neural stem cells at all. Although they check many of the classic boxes, they fall short of a defining characteristic -- the ability to spring forth a diversity of cell types.

That explains why there isn't perfect tail regeneration in the lizard, Lozito said. The neural stem cells can't produce the different cell types that would be needed to recreate the asymmetries of the original spinal cord, which in turn stymies the development of bony vertebrae.

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Scarlet macaw DNA points to ancient breeding operation in Southwest

Scarlett macaw.

Somewhere in the American Southwest or northern Mexico, there are probably the ruins of a scarlet macaw breeding operation dating to between 900 and 1200 C.E., according to a team of archaeologists who sequenced the mitochondrial DNA of bird remains found in the Chaco Canyon and Mimbres areas of New Mexico.

Remains of a thriving prehistoric avian culture and breeding colony of scarlet macaws exist at the northern Mexican site of Paquimé, or Casas Grande. However, this community existed from 1250 to 1450, well after the abandonment of Chaco Canyon, and could not have supplied these birds to Southwest communities prior to the 13th century, said Richard George, graduate student in anthropology, Penn State.

Historically, scarlet macaws lived from South America to eastern coastal Mexico and Guatemala, thousands of miles from the American Southwest. Previously, researchers thought that ancestral Puebloan people might have traveled to these natural breeding areas and brought birds back, but the logistics of transporting adolescent birds are difficult. None of the sites where these early macaw remains were found contained evidence of breeding -- eggshells, pens or perches.

"We were interested in the prehistoric scarlet macaw population history and the impacts of human direct management," said George. "Especially any evidence for directed breeding or changes in the genetic diversity that could co-occur with different trade networks."

The researchers sequenced the mitochondrial DNA of 20 scarlet macaw specimens, but were only able to obtain full sequences from 14. They then directly radiocarbon-dated all 14 birds with complete or near complete genomes and found they fell between 900 and 1200 CE.

"We looked at the full mitochondrial genome of over 16,000 base pairs to understand the maternal relationships represented in the Chaco Canyon and Mimbres regions," said George.

Mitochondrial DNA exists separate from the cell nucleus and is inherited directly from the mother. While nuclear DNA combines the DNA inherited from both parents, mitochondrial DNA can show direct lineage because all siblings have the same mtDNA as their mother, and she has the same mtDNA as her own siblings and mother, all the way back through their ancestry.

Scarlet macaws in Mexico and Central America have five haplogroups -- genetically similar, but not identical mitochondrial DNA lines -- and each haplogroup has a number of haplotypes containing identical DNA lines. The researchers found that their scarlet macaws were all from haplogroup 6 and that 71 percent of the birds shared one of four unique haplotypes. They report the results of this analysis today (Aug 13) in the Proceedings of the National Academy of Sciences.

The researchers found that the probability of obtaining 14 birds from the wild and having them all come from the same haplogroup, one that is small and isolated, was extremely small. A better explanation, especially because these specimens ranged over a 300-year period, is that all the birds came from the same breeding population and that this population existed somewhere in the American Southwest or northern Mexico.

"These birds all likely came from the same source, but we don't have any way to support that assumption without examining the full genome," said George. "However, the genetic results likely indicate some type of narrow breeding from a small founder population with little or no introgression or resupply."

However, no one has found macaw breeding evidence dating to the 900 to 1200 period in the American Southwest or northern Mexico.

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The behavior of water: Scientists find new properties of H2O

Scuba diver looking at ice hole, while ice diving.

A team of scientists has uncovered new molecular properties of water -- a discovery of a phenomenon that had previously gone unnoticed.

Liquid water is known to be an excellent transporter of its own autoionization products; that is, the charged species obtained when a water molecule (H2O) is split into protons (H+) and hydroxide ions (OH?). This remarkable property of water makes it a critical component in emerging electrochemical energy production and storage technologies such as fuel cells; indeed, life itself would not be possible if water did not possess this characteristic.

Water is known to consist an intricate network of weak, directional interactions known as hydrogen bonds. For nearly a century, it was thought that the mechanisms by which water transports the H+ and OH? ions were mirror images of each other -- identical in all ways except for directions of the hydrogen bonds involved in the process.

Current state-of-the-art theoretical models and computer simulations, however, predicted a fundamental asymmetry in these mechanisms. If correct, this asymmetry is something that could be exploited in different applications by tailoring a system to favor one ion over the other.

Experimental proof of the theoretical prediction has remained elusive because of the difficulty in directly observing the two ionic species. Different experiments have only provided glimpses of the predicted asymmetry.

A team of scientists at New York University, led by Professor Alexej Jerschow and including Emilia Silletta, an NYU postdoctoral fellow, and Mark Tuckerman, a professor of chemistry and mathematics at NYU, devised a novel experiment for nailing down this asymmetry. The experimental approach involved cooling water down to its so-called temperature of maximum density, where the asymmetry is expected to be most strongly manifest, thereby allowing it to be carefully detected.

It is common knowledge that ice floats on water and that lakes freeze from the top. This is because water molecules pack into a structure with lower density than that of liquid water -- a manifestation of the unusual properties of water: the density of liquid water increases just above the freezing point and reaches a maximum at four degrees Celsius (39 degrees Fahrenheit), the so-called temperature of maximum density; this difference in density dictates that liquid is always situated below ice.

By cooling water down to this temperature, the team employed nuclear magnetic resonance methods (the same type of approach is medically in magnetic resonance imaging) to show that the difference in lifetimes of the two ions reaches a maximum value (the greater the lifetime, the slower the transport). By accentuating the difference in lifetimes, the asymmetry became glaringly clear.

As noted previously, water consists of one oxygen atom and two hydrogen atoms, but the hydrogen atoms are relatively mobile and can hop from one molecule to another, and it is this hopping that renders the two ionic species so mobile in water.

In seeking explanations for the temperature-dependent characteristics, the researchers focused on the speed with which such hops can occur.

Prior research had indicated that two main geometrical arrangements of hydrogen bonds (one associated with each ion) facilitate the hops. The researchers found that one of the arrangements led to significantly slower hops for OH? than for H+ at four degrees Celsius. Being that this is also the temperature of maximum density, the researchers felt that the two phenomena had to be linked. In addition, their results showed that molecules' hopping behavior changed abruptly at this temperature.

"The study of water's molecular properties is of intense interest due to its central role in enabling physiological processes and its ubiquitous nature," says Jerschow, the corresponding author of this study. "The new finding is quite surprising and may enable deeper understanding of water's properties as well as its role as a fluid in many of nature's phenomena."

Tuckerman, who was one of the first researchers to predict the asymmetry in the transport mechanisms and the difference in the hydrogen bond arrangements, says, "It is gratifying to have this clear piece of experimental evidence confirm our earlier predictions. We are currently seeking new ways to exploit the asymmetry between H+ and OH? transport to design new materials for clean energy applications, and knowing that we are starting with a correct model it central to our continued progress."

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Unraveling the nature of 'whistlers' from space in the lab

Scientists at the University of California, Los Angeles present research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets of radio waves that race along magnetic field lines. Appearing in the Physics of Plasmas, the study provides new insights into the nature of whistlers and space plasmas and could one day aid in the development of practical plasma technologies with magnetic fields, including spacecraft thrusters that use charged particles as fuel. This image shows the growth of a whistler mode with circular phase front and cross-field propagation.

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets of radio waves that race along magnetic field lines. This first-of-its-kind study, appearing in the Physics of Plasmas, from AIP Publishing, provides new insights into the nature of whistlers and space plasmas -- regions of energized particles trapped by Earth's magnetic fields. These studies could one day aid in the development of practical plasma technologies with magnetic fields, including spacecraft thrusters that use charged particles as fuel.

"We have discovered new effects of these so-called whistler waves," said Reiner Stenzel, an author on the paper. "These new laboratory studies will help expand our knowledge on this intriguing electromagnetic phenomenon and suggest new applications and possible inventions."

Whistler waves were first detected in the early 1900s. They were found to come from lightning interacting with Earth's magnetic fields. As they traveled through Earth's ionosphere and magnetosphere, whistlers with low tones propagate more slowly than the higher frequency whistlers. As a result, simple radio receivers were used to listen to the radio waves, and the falling pitch sounded like a whistle.

Stenzel and his co-author, Manuel Urrutia, studied the growth, propagation and decay of whistler waves in nonuniform magnetic fields in their laboratory. They discovered that these waves behaved differently than predicted by an 80-year-old theory.

These laboratory studies involved creating whistler waves with magnetic antennas inside a plasma-filled chamber. The researchers then studied the behavior and propagation of these waves in 3D space with a movable probe. This enabled the team to study how these waves propagate through 3D space as a function of time. They could also study the waves under a variety of conditions, including how they behave when exposed to both straight and circular magnetic field lines and magnetic null points -- regions where there was no field at all.

"Our laboratory experiments reveal three-dimensional wave properties in ways that simply cannot be obtained from observations in space," said Stenzel. "This enabled us to study continuous waves as well as the growth and decay of waves with amazing detail. This produced unexpected discoveries of wave reflections and of cylindrical whistler modes."

Whistler waves are considered a form of helicon waves, or low-frequency electromagnetic waves that travel in a corkscrewlike, or helixlike, pattern. When helicons interact with plasmas, they exert a pressure and torque on the electrons.

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How birds learn

Zebra finch.

Children are constantly learning new things, but whether they find it easy or hard to generalise what they have learned and apply it to new situations can depend on how they learned it. It is much the same for songbirds. In their first few months of life, they too must learn a great deal; for example, the characteristic song of their species. And like people, birds also learn in different ways. How these methods impact the ability to generalise was the subject of a study on zebra finches, conducted by a research team led by Richard Hahnloser, Professor at ETH Zurich and the University of Zurich.

In their experiments, the researchers were able to show that zebra finches can learn by observing fellow members of their species. The birds had to learn through trial and error to discriminate between two classes of birdsong, one long and one short. Without any special preparation, the median number of repetitions it took for the birds to master the task was 4,700. But if the finches were able to observe other finches as they learned this task, then it took them just 900 repetitions. In this experimental set up and for statistical reasons, 800 repetitions are required in order to evaluate the animals' performance. This means that the observing birds mastered the task almost from the very beginning.

Better generalisation

In the next phase of the experiment, the researchers tested how well the zebra finches could solve a second, similar task, in which the birds had to distinguish between varying lengths of a different sample of birdsongs. This revealed that birds that learned the first task using trial and error from the outset could solve the second task practically right away: It took them a median of just 800 attempts. By contrast, birds that learned the first task primarily through observation needed a median value of 3,600 attempts.

"These results indicate that in zebra finches, learning by trial and error is the more robust method," summarises Hahnloser, continuing, "Birds that learned a perceptual skill through trial and error were better able to generalise and adapt that skill to new situations than those that learned it through observation."

Both learning methods have their advantages

Gagan Narula, a postdoc in Hahnloser's group and lead author of the study, points to parallels with how children and youths learn: "Active learning, which focuses on experimentation and trial and error, is becoming more and more prevalent in schools. In secondary schools, even maths is now being taught with the help of experiments."

Still, "both methods have their advantages," Hahnloser says, "but learning through observation is faster." He notes that the Swiss education system deliberately incorporates both learning methods: lectures and observation on the one hand, and experiments, exercises and homework on the other.

Differing degrees of brain involvement

Neural computer models assisted the scientists in interpreting their findings. From these model calculations, the researchers surmise that although the act of observation involves many synapses between neurons in a finch brain, these are relatively weak. In contrast, trial-and-error learning involves a smaller number of synapses, but they are much stronger, leading to an enhanced ability to generalise. Hahnloser explains: "When observing, the birds may focus on a large number of song details, many of which are irrelevant for solving the problem at hand. In the trial-and-error case, they remember fewer details but focus on the most prominent aspects of the song, such as its duration."

Whether different learning methods affect the brains of children and teenagers in the same way is still to be investigated. "In the past, research on zebra finches has repeatedly provided important clues and hypotheses for investigating neurobiological processes, in particular in relation to vocal learning," says Hahnloser. "Our latest findings in finches also lead to hypotheses that could be studied in humans to better understand social learning processes."

The experiment

For the experiment, the scientists used two adjacent birdcages separated by a partition, with a zebra finch in each cage. One of the finches had to use trial and error to learn to discriminate between two classes of birdsong. The other bird observed the learning process.

Each of the birds could see the other only by sitting on a particular perch in the cage next to a window in the partition. Because zebra finches are social animals, they were naturally drawn to this particular perch.

If the "experimenter" finch flew to that perch, it would hear one of ten variations of a zebra finch song. The samples had minimal differences in length, which was the defining property for splitting the song samples into two classes: Class A contained the five shorter song samples (lasting 0.9 to 1.0 seconds), and Class B had the five longer ones (1.03 to 1.13 seconds). One second after a sample from Class B was played, the team administered an air-puff to the bird.

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Amputees feel as though their prosthetic limb belongs to their own body

Amputees can learn to feel that their phantom limb actually grows into their prosthetic hand.

The famous idiom "seeing is believing" is not enough to help amputees with the use of their prosthetic limb. Many amputees opt out of prolonged use of their prosthetic limb because their missing limb simply does not fit their prosthesis. In other words, their own perception of the missing limb, or the brain's representation of it, does not match-up with what they see of the prosthesis.

The underlying problem is twofold. Amputees still feel their missing limb, even if it is physically gone, and this ghost limb aka phantom limb is perceived as much smaller that the lost limb. Next, the commercially available prosthetic limb does not yet provide sensory feedback other than what the patient sees, meaning that the patient has no sense of touch from the prosthetic limb and must constantly watch it for correct use.

Tricking the brain to embody the prosthetic limb

Now, in a scientific collaboration led by EPFL (Ecole polytechnique fédérale de Lausanne), scientists show that amputees can actually be convinced that the prosthetic hand belongs to their own body. They do this by going beyond the "seeing is believing" idiom based on established research on how the brain identifies what belongs to its own body. Instead of using the sense of sight alone, they used an astute combination of two senses: sight and touch. The results are published today in the Journal of Neurology, Neurosurgery & Psychiatry.

"The brain regularly uses its senses to evaluate what belongs to the body and what is external to the body. We showed exactly how vision and touch can be combined to trick the amputee's brain into feeling what it sees, inducing embodiment of the prosthetic hand with an additional effect that the phantom limb grows into the prosthetic one," explains Giulio Rognini of EPFL's Laboratory of Cognitive Neuroprosthetics led by Olaf Blanke, in a collaboration with Silvestro Micera of EPFL and Scuola Superiore Sant'Anna in Italy. "The setup is portable and could one day be turned into a therapy to help patients embody their prosthetic limb permanently."

In two hand amputees, the scientists provided artificial tactile sensations at the tip of the index finger -- of the phantom limb -- by stimulating the patient's nerve in the stump. At the same time, the patient wore virtual reality goggles which showed the index finger of the prosthetic limb glowing in synchrony with the administered touch sensations. This combination of virtual reality with artificial tactile sensations takes the rubber-hand illusion to another level.

Both patients reported feeling as though the prosthetic hand belonged to their own body. Moreover, when asked to evaluate the position of their hands, both patients felt as though their phantom limb had extended into the prosthetic limb. Previous to the experiment, they both reported that the phantom hand was small and directly connected to the stump, as if the phantom limb had no forearm, a change in size referred to as "telescoping" in scientific jargon. In fact, their phantom limb extended during the experiment, and remained extended for up to 10 minutes afterwards.

The experiment simply requires the patient to passively observe two sensations on the fingertip, the visual glow and the artificial touch happening in synchrony, in order for embodiment and extension of the phantom limb to take place. This is the first time that the principles of multisensory integration, in particular how the brain integrates bodily multisensory information to create the coherent and compelling experience of having a body, have been tailored to provoke embodiment of the prosthetic hand and reduction of telescoping.

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Easter Island's society might not have collapsed

Examples of the Easter Island statues, or moai.

You probably know Easter Island as "the place with the giant stone heads." This remote island 2,300 miles off the coast of Chile has long been seen as mysterious -- a place where Polynesian seafarers set up camp, built giant statues, and then destroyed their own society through in-fighting and over-exploitation of natural resources. However, a new article in the Journal of Pacific Archaeology hints at a more complex story -- by analyzing the chemical makeup of the tools used to create the big stone sculptures, archaeologists found evidence of a sophisticated society where the people shared information and collaborated.

"For a long time, people wondered about the culture behind these very important statues," says Field Museum scientist Laure Dussubieux, one of the study's authors. "This study shows how people were interacting, it's helping to revise the theory."

"The idea of competition and collapse on Easter Island might be overstated," says lead author Dale Simpson, Jr., an archaeologist from the University of Queensland. "To me, the stone carving industry is solid evidence that there was cooperation among families and craft groups."

The first people arrived on Easter Island (or, in the local language, Rapa Nui) about 900 years ago. "The founding population, according to oral tradition, was two canoes led by the island's first chief, Hotu Matu'a," says Simpson, who is currently on the faculty of the College of DuPage. Over the years, the population rose to the thousands, forming the complex society that carved the statues Easter Island is known for today. These statues, or moai, often referred to as "Easter Island heads," are actually full-body figures that became partially buried over time. The moai, which represent important Rapa Nui ancestors, number nearly a thousand, and the largest one is over seventy feet tall.

According to Simpson, the size and number of the moai hint at a complex society. "Ancient Rapa Nui had chiefs, priests, and guilds of workers who fished, farmed, and made the moai. There was a certain level of sociopolitical organization that was needed to carve almost a thousand statues," says Simpson.

Recent excavations of four statues in the inner region of Rano Raraku, the statue quarry, were conducted by Jo Anne Van Tilburg of Cotsen Institute of Archaeology, UCLA and director of the Easter Island Statue Project, along with her Rapa Nui excavation team. To better understand the society that fabricated two of the statues, Simpson, Dussubieux, and Van Tilburg took a detailed look at twenty one of about 1,600 stone tools made of volcanic stone called basalt that had been recovered in Van Tilburg's excavations. About half of the tools, called toki, recovered were fragments that suggested how they were used.

For Van Tilburg, the goal of the project was to gain a better understanding of how tool makers and statue carvers may have interacted, thus gaining insight into how the statue production industry functioned. "We wanted to figure out where the raw materials used to manufacture the artifacts came from," explained Dussubieux. "We wanted to know if people were taking material from close to where they lived."

There are at least three different sources on Easter Island that the Rapa Nui used for material to make their stone tools. The basalt quarries cover twelve square meters, an area the size of two football fields. And those different quarries, the tools that came from them, and the movement between geological locations and archaeological sites shed light on prehistoric Rapa Nui society.

"Basalt is a grayish rock that doesn't look like anything special, but when you look at the chemical composition of the basalt samples from different sources, you can see very subtle differences in concentrations of different elements," explains Dussubieux. "Rock from each source is different because of the geology of each site."

Dussubieux led the chemical analysis of the stone tools. The archaeologists used a laser to cut off tiny pieces of stone from the toki and then used an instrument called a mass spectrometer to analyze the amounts of different chemical elements present in the samples. The results pointed to a society that Simpson believes involved a fair amount of collaboration.

"The majority of the toki came from one quarry complex -- once the people found the quarry they liked, they stayed with it," says Simpson. "For everyone to be using one type of stone, I believe they had to collaborate. That's why they were so successful -- they were working together."

To Simpson, this level of large-scale cooperation contradicts the popular narrative that Easter Island's inhabitants ran out of resources and warred themselves into extinction. "There's so much mystery around Easter Island, because it's so isolated, but on the island, people were, and still are, interacting in huge amounts," says Simpson. While the society was later decimated by colonists and slavery, Rapa Nui culture has persisted. "There are thousands of Rapa Nui people alive today -- the society isn't gone," Simpson explains.

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Parker Solar Probe launches on historic journey to touch the sun

The United Launch Alliance Delta IV Heavy rocket is seen in this long exposure photograph as it launches NASA's Parker Solar Probe to touch the Sun, Sunday, Aug. 12, 2018 from Launch Complex 37 at Cape Canaveral Air Force Station, Florida. Parker Solar Probe is humanity’s first-ever mission into a part of the Sun’s atmosphere called the corona. Here it will directly explore solar processes that are key to understanding and forecasting space weather events that can impact life on Earth.

Hours before the rise of the very star it will study, NASA's Parker Solar Probe launched from Florida Sunday to begin its journey to the Sun, where it will undertake a landmark mission. The spacecraft will transmit its first science observations in December, beginning a revolution in our understanding of the star that makes life on Earth possible.

Roughly the size of a small car, the spacecraft lifted off at 3:31 a.m. EDT on a United Launch Alliance Delta IV Heavy rocket from Space Launch Complex-37 at Cape Canaveral Air Force Station. At 5:33 a.m., the mission operations manager reported that the spacecraft was healthy and operating normally.

The mission's findings will help researchers improve their forecasts of space weather events, which have the potential to damage satellites and harm astronauts on orbit, disrupt radio communications and, at their most severe, overwhelm power grids.

"This mission truly marks humanity's first visit to a star that will have implications not just here on Earth, but how we better understand our universe," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate. "We've accomplished something that decades ago, lived solely in the realm of science fiction."

During the first week of its journey, the spacecraft will deploy its high-gain antenna and magnetometer boom. It also will perform the first of a two-part deployment of its electric field antennas. Instrument testing will begin in early September and last approximately four weeks, after which Parker Solar Probe can begin science operations.

"Today's launch was the culmination of six decades of scientific study and millions of hours of effort," said project manager Andy Driesman, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. "Now, Parker Solar Probe is operating normally and on its way to begin a seven-year mission of extreme science."

Over the next two months, Parker Solar Probe will fly towards Venus, performing its first Venus gravity assist in early October -- a maneuver a bit like a handbrake turn -- that whips the spacecraft around the planet, using Venus's gravity to trim the spacecraft's orbit tighter around the Sun. This first flyby will place Parker Solar Probe in position in early November to fly as close as 15 million miles from the Sun -- within the blazing solar atmosphere, known as the corona -- closer than anything made by humanity has ever gone before.

Throughout its seven-year mission, Parker Solar Probe will make six more Venus flybys and 24 total passes by the Sun, journeying steadily closer to the Sun until it makes its closest approach at 3.8 million miles. At this point, the probe will be moving at roughly 430,000 miles per hour, setting the record for the fastest-moving object made by humanity.

Parker Solar Probe will set its sights on the corona to solve long-standing, foundational mysteries of our Sun. What is the secret of the scorching corona, which is more than 300 times hotter than the Sun's surface, thousands of miles below? What drives the supersonic solar wind -- the constant stream of solar material that blows through the entire solar system? And finally, what accelerates solar energetic particles, which can reach speeds up to more than half the speed of light as they rocket away from the Sun?

Scientists have sought these answers for more than 60 years, but the investigation requires sending a probe right through the unrelenting heat of the corona. Today, this is finally possible with cutting-edge thermal engineering advances that can protect the mission on its daring journey.

"Exploring the Sun's corona with a spacecraft has been one of the hardest challenges for space exploration," said Nicola Fox, project scientist at APL. "We're finally going to be able to answer questions about the corona and solar wind raised by Gene Parker in 1958 -- using a spacecraft that bears his name -- and I can't wait to find out what discoveries we make. The science will be remarkable."

Parker Solar Probe carries four instrument suites designed to study magnetic fields, plasma and energetic particles, and capture images of the solar wind. The University of California, Berkeley, U.S. Naval Research Laboratory in Washington, University of Michigan in Ann Arbor, and Princeton University in New Jersey lead these investigations.

Parker Solar Probe is part of NASA's Living with a Star program to explore aspects of the Sun-Earth system that directly affect life and society. The Living with a Star program is managed by the agency's Goddard Space Flight Center in Greenbelt, Maryland, for NASA's Science Mission Directorate in Washington. APL designed and built, and operates the spacecraft.

The mission is named for Eugene Parker, the physicist who first theorized the existence of the solar wind in 1958. It's the first NASA mission to be named for a living researcher.

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Experts highlight ebola vaccine progress and suggest next steps

April 3, 2017: Study volunteer receives an inoculation at Redemption Hospital in Monrovia, Liberia on the opening day of PREVAC, a Phase 2 Ebola vaccine trial in West Africa.

Despite promising advances, important scientific questions remain unanswered in the effort to develop a safe and effective Ebola vaccine, according to members of an international Ebola research consortium. In a Viewpoint published in The Lancet, the experts review the current field of Ebola vaccine candidates and clinical trials and highlight key gaps in knowledge that need to be addressed by future research.

Researchers at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, are among the Viewpoint's authors. All authors are with the Partnership for Research on Ebola VACcination (PREVAC). In addition to NIAID, the partnership, established in 2017, comprises experts from the French National Institute of Health and Medical Research (Inserm), the London School of Hygiene & Tropical Medicine (LSHTM), the West African Clinical Research Consortium and their collaborators. PREVAC is currently conducting a Phase 2 clinical trial in Guinea, Liberia, Sierra Leone and Mali to evaluate three Ebola vaccination strategies in people one year and older.

Ebola virus disease remains a public health threat -- the Democratic Republic of the Congo (DRC) already has experienced two Ebola outbreaks in 2018 -- underscoring the need for continued efforts to develop an effective vaccine. The authors note that 36 trials of Ebola vaccine candidates have been completed and another 14 are active, according to clinicaltrials.gov. The rVSV-ZEBOV experimental vaccine, which has been deployed in the DRC, is the only candidate with some clinical efficacy data, which were obtained in a clinical trial in Guinea conducted during the 2014-2016 Ebola outbreak in Guinea.

After reviewing the status of four additional vaccine candidates under study (Ad26.ZEBOV, MVA-BN-Filo, chAd3-EBO-Z, and the GamEvac-Combi vaccine), the authors highlight areas where more research is required. Specifically, they note the need for more data in pregnant women, children and immunocompromised populations, including people infected with HIV and the elderly. Additionally, they say more research is needed on the durability and rapidity of immune responses generated by various vaccine approaches. The experts also call for studies to identify reliable correlates of protection (the specific and measurable part of an immune response that would indicate a person is protected from Ebola) as well as large-scale trials to fully evaluate the safety and efficacy of experimental vaccines.

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Marine mammals lack functional gene to defend against popular pesticide

As marine mammals evolved to make water their primary habitat, they lost the ability to make a protein that defends humans and other land-dwelling mammals from the neurotoxic effects of a popular man-made pesticide, according to new research from the University of Pittsburgh School of Medicine.

As marine mammals evolved to make water their primary habitat, they lost the ability to make a protein that defends humans and other land-dwelling mammals from the neurotoxic effects of a popular human-made pesticide, according to new research from the University of Pittsburgh School of Medicine.

The implications of this discovery, announced today in Science, led researchers to call for monitoring our waterways to learn more about the impact of pesticides and agricultural run-off on marine mammals, such as dolphins, manatees, seals and whales. The research also may shed further light on the function of the gene encoding this protein in humans.

"We need to determine if marine mammals are, indeed, at an elevated risk of serious neurological damage from these pesticides because they biologically lack the ability to break them down, or if they've somehow adapted to avoid such damage in an as-yet undiscovered way," said senior author Nathan L. Clark, Ph.D., associate professor in Pitt's Department of Computational and Systems Biology, and the Pittsburgh Center for Evolutionary Biology and Medicine. "Either way, this is the kind of serendipitous finding that results from curiosity-driven scientific research. It is helping us to understand what our genes are doing and the impact the environment can have on them."

Clark and lead author Wynn K. Meyer, Ph.D., a postdoctoral associate in his laboratory, knew from previous research by other scientists that some genes behind smelling and tasting lost their function during the evolution of marine mammals. They set out to see what other genes conserved in land-dwelling mammals had lost function in marine mammals.

By analyzing DNA sequences from five species of marine mammals and 53 species of terrestrial mammals, the team found that Paraoxonase 1 (PON1), was the gene that best matched the pattern of losing function in marine mammals while retaining function in all terrestrial mammals. PON1 even beat out several genes responsible for smell and taste, senses that marine mammals don't rely on much.

In humans and other terrestrial mammals, PON1 reduces cellular damage caused by unstable oxygen atoms. It also protects us from organophosphates, some of which are pesticides that kill insects -- which lack PON1 -- by disrupting their neurological systems.

Clark and Meyer worked with Joseph Gaspard, Ph.D., director of science and conservation at the Pittsburgh Zoo & PPG Aquarium, and Robert K. Bonde, Ph.D., now a scientist emeritus at the U.S. Geological Survey's Wetland and Aquatic Research Center, to obtain marine mammal blood samples from U.S. and international scientists and conservation biologists. Collaborators at the University of Washington reacted blood samples from several marine mammals with an organophosphate byproduct and observed what happened. The blood did not break down the organophosphate byproduct the way it does in land mammals, indicating that, unless a different biological mechanism is protecting the marine mammals, they would be susceptible to "organophosphate poisoning," a form of poisoning that results from the buildup of chemical signals in the body, especially the brain.

In an attempt to learn why marine mammals lost PON1 function, the researchers traced back when the function was lost in three different groups of marine mammals. Whales and dolphins lost it soon after they split from their common ancestor with hippopotamuses 53 million years ago; manatees lost it after their split from their common ancestor with elephants 64 million years ago. But some seals likely lost PON1 function more recently, at most 21 million years ago and possibly in very recent times.

"The big question is, why did they lose function at PON1 in the first place?" said Meyer. "It's hard to tell whether it was no longer necessary or whether it was preventing them from adapting to a marine environment. We know that ancient marine environments didn't have organophosphate pesticides, so we think the loss might instead be related to PON1's role in responding to the extreme oxidative stress generated by long periods of diving and rapid resurfacing. If we can figure out why these species don't have functional PON1, we might learn more about the function of PON1 in human health, while also uncovering potential clues to help protect marine mammals most at risk."

As an example of the potential real-world consequences of losing function at PON1, the researchers explain in their scientific manuscript that in Florida, "agricultural use of organophosphate pesticides is common and runoff can drain into manatee habitats. In Brevard County, where 70 percent of Atlantic Coast manatees are estimated to migrate or seasonally reside, agricultural lands frequently abut manatee protection zones and waterways."

The scientists believe the next step is to launch a study that directly observes marine mammals during and shortly after periods of excess agricultural organophosphate run-off. Such a project would require increased monitoring of marine mammal habitats, as well as testing of tissues from deceased marine mammals for evidence of organophosphate exposure. The most recent estimate the research team could find of organophosphate levels in manatee habitats in Florida is a decade old, Clark said.

"Marine mammals, such as manatees or bottlenose dolphins, are sentinel species -- the canary in the coal mine," said Clark. "If you follow their health, it will tell you a lot about potential environmental issues that could eventually affect humans."

Additional authors on this research include Jerrica Jamison, Raghavendran Partha, M.Tech., Amanda Kowalczyk, B.S., Charles Kronk, B.S., and Maria Chikina, Ph.D., all of Pitt; Rebecca Richter, B.S., Judit Marsillach, Ph.D., and Clement E. Furlong, Ph.D., all of the University of Washington; Stacy E. Woods, Ph.D., M.P.H., of Johns Hopkins University; Daniel E. Crocker, Ph.D., of Sonoma State University; and Janet M. Lanyon, Ph.D., of the University of Queensland.

Read more at Science Daily