In A.D. 185, Chinese records note the appearance of a “guest star” that then faded away over the span of several months. In 1572, astronomer Tycho Brahe and many others watched as a previously unknown star in the constellation Cassiopeia blasted out gobs of light and then eventually disappeared. And 30 years ago, the world witnessed a similar blaze of light from a small galaxy that orbits the Milky Way. In each case, humankind stood witness to a supernova — an exploding star — within or relatively close to our galaxy (representative border in gray, below).
Here’s a map of six supernovas directly seen by human eyes throughout history, and one nearby explosion that went unnoticed. Some were type 1a supernovas, the detonation of a stellar core left behind after a star releases its gas into space. Others were triggered when a star at least eight times as massive as the sun blows itself apart.
BOSTON — A fungus among us may tip the body toward developing asthma.
There’s mounting evidence that early exposure to microbes can protect against allergies and asthma (SN Online: 7/20/16). But “lo and behold, some fungi seem to put kids at risk for asthma,” microbiologist Brett Finlay said February 17 at a news conference during the annual meeting of the American Association for the Advancement of Science.
Infants whose guts harbored a particular kind of fungus — a yeast called Pichia — were more likely to develop asthma than babies whose guts didn’t have the fungus, Finlay reported. Studies in mice and people suggest that exposure to some fungi can both trigger and exacerbate asthma, but this is the first work linking asthma to a fungus in the gut microbiome of infants. Finlay, of the University of British Columbia in Vancouver, and his colleagues had recently identified four gut bacteria in Canadian infants that seem to provide asthma protection. To see if infants elsewhere were similarly protected by such gut microbes, he decided to look at another population of children with an asthma rate similar to Canada’s (about 10 percent). He and his colleagues sampled the gut microbes of 100 infants in rural Ecuador and followed up five years later.
The researchers identified several factors that might influence risk of developing asthma, such as exposure to antibiotics, having respiratory infections, and whether or not the infants were breastfed. Of the 29 infants in the high-risk asthma group, more than 50 percent had asthma by age 5, Finlay said.
Surprisingly, the strongest predictor of whether a child developed asthma wasn’t bacterial. It was the presence of Pichia. And the yeast wasn’t protective; it tipped the scales toward asthma.
Finlay speculated that molecules made by the fungi interact with the infants’ developing immune systems in a way that somehow increases asthma risk. It isn’t clear how the infants’ guts acquire the fungus; some species of Pichia are found in soil, others in raw milk and cheese. Finlay and his colleagues are now going to look for the fungus in Canadian children’s gut microbes..
The researchers also looked at other gut microbe‒related factors that upped the Ecuadorean children’s asthma risk. Children with access to clean water had higher asthma rates, Finlay said. While drinking clean water helps people avoid several ills such as cholera, the link to asthma highlights how some dirt can be protective, he said. “We’ve cleaned up our world too much.” This research underscores that caution should be used when generalizing about our intestinal flora. “What’s emerging is that it is very personalized,” gastroenterologist Eran Elinav of the Weizmann Institute of Science in Rehovot, Israel, said at the news conference. For example, evidence implicates some fungi in the development of inflammatory bowel disease, Elinav said, but it depends on the individual.
Scientists have constructed five more yeast chromosomes from scratch. The new work, reported online March 9 in Science, brings researchers closer to completely lab-built yeast.
“We’re doing it primarily to learn a little more about how cells are wired,” says geneticist Jef Boeke of the New York University Langone Medical Center. But scientists might also be able to tinker with a synthetic yeast cell more efficiently than a natural one, allowing more precise engineering of everything from antiviral drugs to biofuels. Boeke was part of a team that reported the first synthetic yeast chromosome in 2014 (SN: 5/3/14, p. 7). Now, several hundred scientists in five countries are working to make all 16 Saccharomyces cerevisiae yeast chromosomes and integrate them into living cells. With six chromosomes finished, Boeke hopes the remaining 10 will be built by the end of 2017.
Each synthetic chromosome is based on one of S. cerevisiae’s, but with tweaks for efficiency. Researchers cut out stretches of DNA that can jump around and cause mutations, as well as parts that code for the same information multiple times.
When the researchers put chunks of synthetic DNA into yeast cells, the cells swapped out parts of their original DNA for the matching engineered snippets.
Yeast is a eukaryote — it stores its DNA in a nucleus, like human cells do. Eventually, this research could produce synthetic chromosomes for more complicated organisms, Boeke says, but such feats are still far in the future.
NEW ORLEANS — The tiniest electronic gadgets have nothing on a new data-storage device. Each bit is encoded using the magnetic field of a single atom — making for extremely compact data storage, although researchers have stored only two bits of data so far.
“If you can make your bit smaller, you can store more information,” physicist Fabian Natterer of the École Polytechnique Fédérale de Lausanne in Switzerland said March 16 at a meeting of the American Physical Society. Natterer and colleagues also reported the result in the March 9 Nature. Natterer and colleagues created the minuscule magnetic bits using atoms of holmium deposited on a surface of magnesium oxide. The direction of each atom’s magnetic field served as the 1 or 0 of a bit, depending on whether its north pole was pointing up or down.
Using a scanning tunneling microscope, the scientists could flip an atom’s magnetic orientation to switch a bit from 0 to 1. To read out the data, the researchers measured the current running through the atom, which depends on the magnetic field’s orientation. To ensure that the change in current observed after flipping a bit was due to a reorientation of the atom’s magnetic field, the team added bystander iron atoms to the mix and measured how the holmium atoms’ magnetic fields affected the iron atoms.
The work could lead to new hard drives that store data at much greater densities than currently possible. Today’s technologies require 10,000 atoms or more to store a single bit of information.
Natterer also hopes to use these mini magnets to construct materials with fine-tuned magnetic properties, building substances a single atom at a time. “You can play with them. It’s like Lego,” he says.
Glass frogs often start life with some tender care from a source scientists didn’t expect: frog moms.
Maternal care wouldn’t be news among mammals or birds, but amphibian parenting intrigues biologists because dads are about as likely as moms to evolve as the caregiver sex. And among New World glass frogs (Centrolenidae), what little parental care there is almost always is dad’s job — or so scientists thought, says Jesse Delia of Boston University. Months of strenuous nights searching streamside leaves in five countries, however, have revealed a widespread world of brief, but important, female care in glass frogs. In examining 40 species, Delia and Laura Bravo-Valencia, now at Corantioquia, a government environmental agency in Santa Fe de Antioquia, Colombia, found that often mothers lingered over newly laid eggs for several hours. By pressing maternal bellies against the brood, moms hydrated the jelly-glop of eggs and improved offspring chances of survival, Delia, Bravo-Valencia and Karen Warkentin, also of BU, report online March 31 in the Journal of Evolutionary Biology.
Glass frogs take their name from see-through skin on their bellies and, in certain cases, transparent organ tissues. (Some have clear hearts that reveal blood swishing through.) These frogs aren’t exactly obscure species, but until this field project, which stretched over six rainy seasons, female care in the family was unknown.
Female glass frogs may not cuddle their eggs for long, but it’s enough to matter, the researchers found. As is common in frogs, the mothers don’t drink with their mouths but absorb water directly through belly skin into a bladder. Moms pressing against a mass of newly laid eggs caused the protective goo to swell — perhaps by osmosis or peeing — and the mass to quadruple in size. For some of the glass frogs in the study, the youngsters were on their own once mom left. But at least hydration created an unpleasant amount of slime for a predator to bite through before getting to frog embryos. Night-hunting katydids in captivity, when offered a choice, barely nibbled at a hydrated mass of frog offspring, concentrating instead on eating an unhydrated clutch. In the field, when researchers removed about two dozen moms from their clutches in two species, mortality at least doubled to around 80 percent. Predators and dehydration caused the most deaths.
There are still more than 100 glass frog species that Delia and Bravo-Valencia haven’t yet watched in the wild. But the researchers did track down maternal care in 10 of 12 genera. Such a widespread form of maternal care probably evolved in the ancestor of all glass frogs, the researchers propose after analyzing glass frog family trees several ways.
In contrast, prolonged care from glass frog dads — rehydrating the egg mass as needed and fighting off predators such as hungry spiders — seems to have arisen independently later, at least twice. Across evolution in the animal kingdom, “usually we don’t see transitions from female to male care,” Delia says. “The pattern we found is completely bizarre.”
Why females started hanging around their eggs at all fascinates Hope Klug, an evolutionary biologist at the University of Tennessee at Chattanooga who studies parental care. In frogs, with eggs mostly fertilized externally, females could easily leave any care to dad.
“Parental care is perhaps more common and diverse in animals than we realize,” she says. “We just might have to look a little bit harder for it.”
When it comes to smelling pretty, petunias are pretty pushy.
Instead of just letting scent compounds waft into the air, the plants use a particular molecule called a transporter protein to help move the compounds along, a new study found. The results, published June 30 in Science, could help researchers genetically engineer many kinds of plants both to attract pollinators and to repel pests and plant eaters.
“These researchers have been pursuing this transporter protein for a while,” says David Clark, an expert in horticultural biotechnology and genetics at the University of Florida in Gainesville. “Now they’ve got it. And the implications could be big.” Plants use scents to communicate (SN: 7/27/02, p. 56). The scent compounds can attract insects and other organisms that spread pollen and help plants reproduce, or can repel pests and plant-eating animals. The proteins found in the new study could be used to dial the amount of scent up or down so that plants can attract more pollinators or better protect themselves. Currently unscented plants could be engineered to smell, too, giving them a better shot at reproduction and survival, Clark says. Plants get their scents from volatile organic compounds, which easily turn into gases at ambient temperatures. Petunias get their sweet smell from a mix of benzaldehyde, the same compound that gives cherries and almonds their fruity, nutty scent, and phenylpropanoids, often used in perfumes.
But nice smells have a trade-off: If these volatile compounds build up inside a plant, they can damage the plant’s cells. About two years ago, study coauthor Joshua Widhalm, a horticulturist at Purdue University in West Lafayette, Ind., and colleagues used computer simulations to look at the way petunias’ scent compounds moved. The results showed that the compounds can’t move out of cells fast enough on their own to avoid damaging the plant. So the researchers hypothesized that something must be shuttling the compounds out.
In the new study, led by Purdue biochemist Natalia Dudareva, the team looked for genetic changes as the plant developed from its budding stage, which had the lowest levels of volatile organic compounds, to its flower-opening stage, with the highest levels. As flowers opened and scent levels peaked, the gene PhABCG1 went into overdrive; levels of the protein that it makes jumped to more than 100 times higher than during the budding stage, the researchers report.
The team then genetically engineered petunias to produce 70 to 80 percent less of the PhABCG1 protein. Compared with regular petunias, the engineered ones released around half as much of the scent compounds, with levels inside the plant’s cells building to double or more the normal levels. Images of the cells show that the accumulation led to deterioration of cell membranes.
A lot of work has been done to identify the genes and proteins that generate scent compounds, says Clark. But this appears to be the first study to have identified a transporter protein to shuttle those compounds out of the cell. “That’s a big deal,” he says.
Galaxies may grow by swiping gas from their neighbors.
New simulations suggest that nearly half the matter in the Milky Way may have been siphoned from the gas of other galaxies. That gas provides the raw material that galaxies use to build their bulk. The finding, scheduled to appear in the Monthly Notices of the Royal Astronomical Society, reveals a new, unexpected way for galaxies to acquire matter and could give clues to how they evolve. “These simulations show a huge amount of interaction among galaxies, a huge dance that’s going on,” says astronomer Romeel Davé of the University of Edinburgh. That dance, and the subsequent exchange of atoms, could be what establishes a galaxy’s character — whether it’s small or big, elliptical or spiral, quiet or bursting with star formation. If the simulation results are confirmed with observations, it could be a major advancement in understanding galaxy formation, Davé says.
It makes sense that much of the material in one galaxy actually came from other galaxies, says study coauthor Claude-André Faucher-Giguère, a theoretical astrophysicist at Northwestern University in Evanston, Ill. “Still, the result was really unexpected,” he says.
Astronomers thought galaxies got their matter in two main ways. First, atoms clumped together to form stars and then galaxies, not long after the Big Bang about 13.8 billion years ago. Then some of those atoms were eventually ejected by supernovas but rained back onto the same galaxy, recycling the gas again and again.
The new simulations showed a third way galaxies could score gas. Powerful supernova explosions would eject atoms, in the form of gas, far from their home galaxies into intergalactic space. Those atoms would then travel through space, pushed toward other galaxies by galactic winds that move at several hundred kilometers per second. When the particles neared a galaxy’s gravitational pull, they would get sucked in, where they would serve as the basis for stars, planets, dust and other material in their new galactic home. Still, this exchange of atoms is extremely difficult to spot in space because the gas atoms, don’t give off light like stars do. Faucher-Giguère and colleagues spotted the exchange in computer simulations that show how galaxies formed just after the Big Bang and how they have evolved over time. The team tracked gas atoms as they moved through the model universe, formed stars and then were ejected from galaxies as those stars exploded.
In the simulations, up to half of the atoms in large galaxies were pulled in from other galaxies. Because more massive galaxies have more gravity, they tended to pull atoms from the ejected material of small galaxies. The exchange appears to take billions of years as atoms travel the vast space between galaxies, the team notes.
“It’s that not surprising to see a galaxy kick out matter, which is then pulled in by other galaxies,” Davé says. What is surprising, he says, is the amount of material that’s transferred. Before seeing the simulations, he would have guessed that about 5 percent of gas was transferred among galaxies this way. “To see that it is up to 50 percent is pretty remarkable,” he says.
Already, astronomers are searching for evidence of this material-swapping behavior among galaxies. Faucher-Giguère and colleagues, working with researchers using the Hubble Space Telescope, hope to observe intergalactic transfer of gas among galaxies soon.
When you’re pregnant, especially for the first time, you have to make a lot of decisions. Will coffee remain a part of your life? Where are you going to give birth? What are you going to name the baby? What values will you teach him? Do you really need a baby spa bathtub?
Before my first daughter arrived, an instructor at a birth class threw me a curveball: Was I planning on banking my baby’s umbilical cord blood? For much of pregnancy, the umbilical cord is the lifeline of a fetus, tethering it to the placenta. Snaking through the nearly 2-feet-long cord, there’s a vein ferrying nutrients and oxygen from mom’s blood (via the placenta), plus two arteries carrying oxygen- and nutrient-depleted blood from the fetus back to mom. Because mother’s blood and fetal blood don’t actually mix much, the blood in the placenta and umbilical cord at birth belongs mainly to the fetus.
That fetal blood holds all sorts of interesting — and potentially therapeutic — cells and molecules. This realization has, in some cases, changed the way the umbilical cord and placenta are handled during birth. Instead of tossing it aside, some doctors, scientists and parents are choosing to bank this fetal blood — harvesting it from the baby’s umbilical cord and placenta, freezing it and storing it away for later.
Proponents of cord blood banking are convinced that instead of being medical waste, the fetal cells within are biological gold. In this post, and the two that follow, I’ll take a look at the evidence for those claims, and sort through some of the questions that arise as parents consider whether to bank their baby’s cord blood.
Back in the 1980s, umbilical cord blood caught the attention of researchers who suspected that the often-discarded tissue could be a valuable source of shape-shifting stem cells. These cells, which can become several different types of blood cells, are similar to the specialized stem cells found in bone marrow that can churn out new blood cells. Such stem cells are found in adult blood, too, but not as abundantly. In 1988, a 5-year-old named Matthew with a rare type of anemia received umbilical cord blood cells from his newborn sister, who didn’t have the disease. That transfer, called an umbilical cord blood transplant, worked, and the boy was soon free of the disease.
At the time, researchers didn’t know much about the properties of the cells found in umbilical cord blood. But research has zoomed forward, illuminating more about the contents of this young blood.
Of particular interest are the flexible hematopoietic stem cells important in that initial transplant. In certain cases, transplanting these cells might be able to reboot a person’s body and get rid of a disease-related defect. Cord blood transplants are similar to bone marrow transplants. A person with leukemia, for instance, might have his own cancerous blood cells wiped out with chemotherapy and radiation. Healthy, non-cancerous stem cells from a donor can then repopulate the blood.
Extracting stem cells from bone marrow requires surgery under anesthesia; extracting them from the blood requires taking a drug to stimulate their production. And in order to work, these stem cell donations need to come from a person who carries a similar pattern of proteins on the outsides of his or her cells, a molecular calling card known as HLA type. Stem cells found in cord blood don’t need to be as closely matched to work. Because these cells are so flexible, there’s more wiggle room between donor and recipient. That’s particularly good news for people of certain ethnic minorities who often have trouble finding matched stem cell transplant donors.
Hard numbers are tricky to pin down, but between that first transplant in 1988 and 2015, an estimated 35,000 umbilical cord blood transplants had been performed globally. That number includes people treated for leukemia and other types of cancer, blood disorders and immune diseases. And the utility of umbilical cord cells may stretch well beyond the disorders that the cells are currently being used for. “If you read the literature, it’s pretty exciting,” says pediatrician and immunologist William Shearer of Baylor College of Medicine and Texas Children’s Hospital.
Some researchers suspect that umbilical cord blood contains other cells that may have therapeutic effects beyond the blood. Specialized immune cells may be able to tweak brain function, for instance. Trials around the world are studying umbilical cord blood’s capabilities in a wide range of diseases (see Table 2 here): Cerebral palsy, autism, diabetes and lupus are currently under investigation. The cells are even being tested for an ameliorating role in Alzheimer’s disease and other neurodegenerative conditions.
After injections with their own umbilical cord blood, 63 children with cerebral palsy improved on motor skills, on average. And a clinical trial to see whether cord blood transplants improve symptoms of children with autism spectrum disorder should wrap up in the summer of 2018, says pediatric researcher and clinician Joanne Kurtzberg of Duke University, who helped establish a not-for-profit umbilical cord bank in North Carolina. (A small but optimistic pilot study has already been completed.)
The potential powers of these cells have researchers excited. But what that scientific hope means for expectant parents facing decisions about cord blood banking is far from clear. For all of the promise, there are lots of reasons why umbilical cord cells may turn out to be less useful than thought. Read my next post for more about these potential drawbacks.
Greenland is melting rapidly, but some glaciers are disappearing faster than others. A new map of the surrounding seafloor helps explain why: Many of the fastest-melting glaciers sit atop deep fjords that allow Atlantic Ocean water to melt them from below.
Researchers led by glaciologist Romain Millan of the University of California, Irvine analyzed new oceanographic and topographic data for 20 major glaciers within 10 fjords in southeast Greenland. The mapping revealed that some fjords are several hundred meters deeper than simulations of the bathymetry suggested, the researchers report online March 25 in Geophysical Research Letters. These troughs allow warmer and saltier waters from deeper in the ocean to reach the glaciers and erode them. Other glaciers are protected by shallow sills, or raised seafloor ledges. These sills act as barriers to the deep, warm water, the new seafloor maps show. The researchers compared their findings with observations of glacier melt from 1930 to 2017, and found that the fastest-melting glaciers tended to be those more exposed to melting from below. The study uses data from two NASA missions — Operation IceBridge, which measures ice thickness and gravity from aircraft, and Oceans Melting Greenland, or OMG, which uses sonar and gravity instruments to map the shape and depth of the seafloor close to the ice front. The OMG mission also involves dropping hundreds of probes into the ocean each year to measure temperature and salinity at different depths. Scientists have long suspected Greenland’s melting may be accelerated by the ocean (SN Online: 7/6/11), but needed data on fjord depth and glacier thickness to prove it.
The high-resolution OMG datasets, in particular, reveal bumps and troughs in the seafloor that were previously unknown, says glaciologist Andy Aschwanden at the University of Alaska Fairbanks, who was not involved with the study. “Those small details can make quite a difference to when a glacier will retreat.”
Just a few tweaks to a bacterial enzyme make it a lean, mean plastic-destroying machine.
One type of plastic, polyethylene terephthalate, or PET, is widely used in polyester clothing and disposable bottles and is notoriously persistent in landfills. In 2016, Japanese scientists identified a new species of bacteria, Ideonella sakaiensis, which has a specialized enzyme that can naturally break down PET.
Now, an international team of researchers studying the enzyme’s structure has created a variant that’s even more efficient at gobbling plastic, the team reports April 17 in Proceedings of the National Academy of Sciences.
The scientists used a technique called X-ray crystallography to examine the enzyme’s structure for clues to its plastic-killing abilities. Then, they genetically tweaked the enzyme to create small variations in the structure, and tested those versions for PET-degrading performance. Some changes made the enzyme work even better. Both the original version and the mutated versions could break down both PET and another, newer bio-based plastic called PEF, short for polyethylene-2,5-furandicarboxylate. With a little more engineering, these enzymes could someday feast at landfills.
