Horses can leap over high hurdles, gallop at speeds of up to 70 kilometers per hour and haul around up to nearly 1,000 kilograms of body weight — and all with just one big toe on each foot. Now, a new study published August 23 in Proceedings of the Royal Society B helps explain why: Streamlined digits improved horses’ strength and speed.

Along with zebras and donkeys, horses are among the few single-toed creatures in the animal kingdom. Scientists have long suspected that horses’ single, hoofed toes helped them run farther and faster over grasslands, letting them flee predators and find fresh forage. But the hypothesis that having one big toe is better than having several, biomechanically speaking, has never been directly tested.
“This study takes an important step” toward resolving why horses shed digits during their early evolution, says Karen Sears, an evolutionary biologist at UCLA.

Ancient horses had a lot of toes to lose. The dog-sized Hyracotherium, which lived about 55 million years ago, had four toes on its front feet, and three on its back feet. Merychippus, which lived about 10 million years ago, resembled a modern horse but had three toes, including one long middle digit with a protective, toenail-like hoof at the end. The only surviving horse genus, single-toed Equus, emerged about 5 million years ago.

“If you look closely, you can still see the vestigial remnants” of a bone that would have led to a side toe on a modern horse’s foot, says Brianna McHorse, a paleontologist at Harvard University.

To retrace the evolution of horse toes, McHorse and colleagues used CT scans to capture the internal structure of fossilized foot bones from 12 kinds of extinct horses. They also analyzed the feet of the closely related Central American tapir, which are oddly toed like Hyracotherium. A computer simulation then let researchers estimate how the bones would respond to the stresses of locomotion for each species, such as jumping over a hurdle or accelerating into a gallop. Then the scientists compared what happened when they applied the animal’s full body weight to just to the central toe, or spread it among multiple toes.

Side toes significantly increased the early horses’ ability to bear their own weight, the team found — the central toe of early horses would have fractured without help from other toes. As the era of modern horses approached and side toes dropped away, however, the middle toe bone grew thicker and hollower. These changes made the single-toed foot nearly as sturdy — resistant to bending and compression — as multiple toes.
As horses’ legs grew longer, the extra toes at the end of the limb would have been “like wearing weights around your ankles,” McHorse says. Shedding those toes could have helped early horses save energy, allowing them to travel farther and faster, she says. The study can’t determine what changes came first — whether bulking up the middle toe drove the loss of side toes, or the loss of side toes caused changes in the middle toe.

Horses aren’t the only animals to have lost toes or fingers to the evolutionary chopping block. “Digits have been lost many times in animals that walk, run, hop and fly,” says Kim Cooper, a biologist at the University of California, San Diego. Modeling how forces of locomotion act on an animal’s bones — living or extinct — could help scientists understand why.

The brain chemical missing in Parkinson’s disease may have a hand in its own death. Dopamine, the neurotransmitter that helps keep body movements fluid, can kick off a toxic chain reaction that ultimately kills the nerve cells that make it, a new study suggests.

By studying lab dishes of human nerve cells, or neurons, derived from Parkinson’s patients, researchers found that a harmful form of dopamine can inflict damage on cells in multiple ways. The result, published online September 7 in Science, “brings multiple pieces of the puzzle together,” says neuroscientist Teresa Hastings of the University of Pittsburgh School of Medicine.
The finding also hints at a potential treatment for the estimated 10 million people worldwide with Parkinson’s: Less cellular damage occurred when some of the neurons were treated early on with antioxidants, molecules that can scoop up harmful chemicals inside cells.

Study coauthor Dimitri Krainc, a neurologist and neuroscientist at Northwestern University Feinberg School of Medicine in Chicago, and colleagues took skin biopsies from healthy people and people with one of two types of Parkinson’s disease, inherited or spontaneously arising. The researchers then coaxed these skin cells into becoming dopamine-producing neurons. These cells were similar to those found in the substantia nigra, the movement-related region of the brain that degenerates in Parkinson’s.
After neurons carrying a mutation that causes the inherited form of Parkinson’s had grown in a dish for 70 days, the researchers noticed some worrisome changes in the cells’ mitochondria. Levels of a harmful form of dopamine known as oxidized dopamine began rising in these energy-producing organelles, reaching high levels by day 150. Neurons derived from people with the more common, sporadic form of Parkinson’s showed a similar increase but later, beginning at day 150. Cells derived from healthy people didn’t accumulate oxidized dopamine.
This dangerous form of dopamine seemed to kick off other types of cellular trouble. Defects in the cells’ lysosomes, cellular cleanup machines, soon followed. So did the accumulation of a protein called alpha-synuclein, which is known to play a big role in Parkinson’s disease.
Those findings are “direct experimental evidence from human cells that the very chemical lost in Parkinson’s disease contributes to its own demise,” says analytical neurochemist Dominic Hare, of the Florey Institute of Neuroscience and Mental Health in Melbourne, Australia. Because these cells churn out dopamine, they are more susceptible to dopamine’s potential destructive forces, he says.

When researchers treated neurons carrying a mutation that causes inherited Parkinson’s with several different types of antioxidants, the damage was lessened. To work in people, antioxidants would need to cross the blood-brain barrier, a difficult task, and reach the mitochondria in the brain. And this would need to happen early, probably even before symptoms appear, Krainc says.

“Without this human model, we would not have been able to untangle the pathway,” Krainc says. In dishes of mouse neurons with Parkinson’s-related mutations, dopamine didn’t kick off the same toxic cascade, a difference that might be due to human neurons containing more dopamine than mice neurons. Dopamine-producing neurons in mice and people “have some very fundamental differences,” Krainc says. And those differences might help explain why discoveries in mice haven’t translated to treatments for people with Parkinson’s, he says.

Over the past few decades, scientists have been accumulating evidence that oxidized dopamine can contribute to Parkinson’s disease, Hastings says. Given that knowledge, the new results are expected, she says, but still welcome confirmation of the idea.

These toxic cellular events occurred in lab dishes, not actual brains. “Cell cultures aren’t the perfect re-creation of what’s going on in the human brain,” Hare cautions. But these types of experiments are “the next best thing for monitoring the chemical changes” in these neurons, he says.

The largest marsupial to ever walk the Earth just got another accolade: It’s also the only marsupial known to migrate seasonally.

Diprotodon optatum was a massive wombat-like herbivore that lived in what’s now Australia and New Guinea during the Pleistocene, until about 40,000 years ago. Now, an analysis of one animal’s teeth suggests that it undertook long, seasonal migrations like those made by zebras and wildebeests in Africa.

Animals pick up the chemical element strontium through their diet, and it leaves a record in their teeth. The ratio of different strontium isotopes varies from place to place, so it can provide clues about where an animal lived. Strontium isotope ratios in an incisor from one D. optatum revealed a repeating pattern. That suggests the animal migrated seasonally — it moved around, but generally hit up the same rest stops each year, researchers report September 27 in the Proceedings of the Royal Society B.

It’s the first evidence to show a marsupial — living or extinct — migrating in this way, says study coauthor Gilbert Price, a paleoecologist at the University of Queensland in Brisbane, Australia. It’s not clear exactly why this mega-marsupial might have migrated, but an analysis of the carbon isotopes in its teeth suggests it ate a fairly limited diet. So it might have migrated to follow food sources that popped up seasonally in different places, the authors suggest.

A 26-year-old woman felt something in her left eye. For days, she couldn’t shake the sensation. But this was no errant eyelash or dive-bombing gnat.

A week after that first irritation, the Oregon resident pulled a translucent worm, about a centimeter long, from her eye. With that harrowing feat, she became the first ever reported case of a human infestation with the cattle eyeworm, Thelazia gulosa. “This is a very rare event and exciting from a parasitological perspective,” says medical parasitologist Richard Bradbury of the U.S. Centers for Disease Control and Prevention in Atlanta. “Perhaps not so exciting if you are the patient.”
Over 20 days, she and her doctors removed 14 worms from her infected eye, researchers report online February 12 in the American Journal of Tropical Medicine and Hygiene. After that, no more irritation.

T. gulosa is a nematode found in North America, Europe, Australia and central Asia. It infects the large, watchful eyes of cattle. The worm spends its larval stage in the abdomen of the aptly named face fly, Musca autumnalis. As the fly feasts on tears and eye secretions, it spreads the nematode larva, which then grow into adult worms.

Two other Thelazia species are known to infect humans, but rarely. There have been more than 160 cases reported for one species in Europe and Asia, and only 10 cases in North America, by a species found in dogs. This new perpetrator was not expected to be seen in a human, Bradbury says.

The young woman had been horseback riding near cattle farms in Gold Beach, Oregon, which may explain her face-to-face with the fly.
“It is just unfortunate for the patient,” Bradbury says, “that she was not able to swish away that one infected fly quickly enough from her eye.”

AUSTIN, Texas — Babies’ stroke-damaged brains can pull a mirror trick to recover.

A stroke on the left side of the brain often damages important language-processing areas. But people who have this stroke just before or after birth recover their language abilities in the mirror image spot on the right side, a study of teens and young adults shows. Those patients all had normal language skills, even though as much as half of their brain had withered away, researchers reported February 17 at the annual meeting of the American Association for the Advancement of Science.
Researchers so far have recruited 12 people ages 12 to 25 who had each experienced a stroke to the same region of their brain’s left hemisphere just before or after birth. People who have this type of stroke as adults often lose their ability to use and understand language, said study coauthor Elissa Newport, a neurology researcher at Georgetown University Medical Center in Washington, D.C.

MRI scans of healthy siblings of the stroke patients showed activity in language centers in the left hemisphere of the brain when the participants heard speech. The stroke patients showed activity in the exact same areas — just on the opposite side of the brain.

It’s well established that if an area of the brain gets damaged, other brain areas will sometimes compensate. But the new finding suggests that while young brains have an extraordinary capacity to recover, there might be limits on which areas can pinch-hit.

“When you look at a very well-defined population, recovery takes place in a very particular set of regions,” said Newport. Young children usually show language activity in the same areas on both sides of their brain, Newport noted, and the left side becomes more dominant over time. But in the case of a major stroke to the left side, the corresponding areas on the right side of the brain might already be primed to take over.

Two newly discovered giant viruses have the most comprehensive toolkit for assembling proteins found in any known virus. In a host cell, the viruses have the enzymes needed to wrangle all 20 standard amino acids, the building blocks of life.

Researchers dubbed the viruses Tupanvirus deep ocean and Tupanvirus soda lake, combining the name of the indigenous South American god of thunder, Tupan, with the extreme environment where each type of virus was found. The giant viruses are among the largest of their kind — up to 2.3 micrometers in length — which is about 23 times as long as a particle of HIV, the scientists report February 27 in Nature Communications.
Tupanviruses can infect a wide range of hosts, such as protists and amoebas, but pose no threat to humans, the researchers say.

Viruses are considered nonliving, but the genetic complexity of giant viruses has some scientists questioning that categorization. Each Tupanvirus, for example, has a massive genetic instruction book with roughly 1.5 million base pairs of DNA, more than what some bacteria have, says coauthor Bernard La Scola, a virologist at Aix-Marseille University in France.

But other scientists say giant viruses aren’t so different from their smaller kin. Research by Frederik Schulz, with the Department of Energy Joint Genome Institute in Walnut Creek, Calif., suggests these microscopic behemoths are regular viruses that acquired extra genes from hosts and should not be classified as life.

Tupanviruses don’t settle the controversy, but they do challenge our preconceptions of what life is, La Scola says.

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.

Ancient surgeons may have practiced dangerous skull-opening procedures on cows before operating on people.

A previously excavated cow skull from a roughly 5,400- to 5,000-year-old settlement in France contains a surgically created hole on the right side, a new study finds. No signs of bone healing, which start several days after an injury, appear around the opening. One or more people may have rehearsed surgical techniques on a dead cow, or may have tried unsuccessfully to save a sick cow’s life in what would be the oldest known case of veterinary surgery, researchers conclude online April 19 in Scientific Reports.

Evidence of skull surgery on humans, whether for medical or ritual reasons, goes back about 11,000 years (SN: 5/28/16, p. 12). Ancient surgeons needed to know how and where to scrape away bone without harming brain tissue and blood vessels. So practicing bone removal on cows or other animals is plausible.

The ancient cow’s skull opening, shaped almost in a square and framed by scrape marks, resembles two instances of human skull surgery from around the same time in France, say biological anthropologists Fernando Ramirez Rozzi of CNRS in Montrouge, France, and Alain Froment of IRD-Museum of Man in Paris. Microscopic and X-ray analyses found no fractures or splintered bone that would have resulted from goring by another cow’s horn. No damage typical of someone having struck the cow’s head with a club or other weapon appeared, either.