Maxim Artyomov, an immunologist at Washington University in St. Louis, told Live Science.
Hunting for a signature of healthy aging
In earlier research, the same team found that, in old lab mice, granzyme K-making cells accumulated in several tissues and were linked to inflammation. They also observed the same increase in granzyme K cells in blood samples from older adults.
In the new study, they uncovered another piece of the puzzle: a dynamic with granzyme B-producing cells.
They began by analyzing immune cells sampled from over 2,600 people ages 18 to 97, looking at the balance of granzyme K- and granzyme B-making cells. They found that people with a lower ratio of granzyme K to granzyme B cell populations were more likely to have autoimmune diseases or other chronic immune conditions.
In a second analysis, they looked at both immune cells and blood-borne proteins sampled from 329 people, using the data to pinpoint a "protein signature" linked to an abundance of granzyme B-making cells.
The balance of cells that make different granzymes may be important to how the immune system functions with age. (Image credit: RUSLANAS BARANAUSKAS/SCIENCE PHOTO LIBRARY via Getty Images)They went on to hunt for this protein signature in around 48,000 participants who'd provided data to the UK Biobank, a large database of health data from U.K.-based adults. People who were predicted to have higher levels of granzyme B-making cells based on their blood proteins had worse health outcomes in the following 17 years, with a higher risk of death and of conditions like diabetes, high blood pressure, and liver and kidney disease.
The findings might point to an aspect of immune aging that wasn't previously understood.
"I think that's really exciting," Claire Gustafson, an immunologist at the Allen Institute, said of the results. "It highlights there's potentially some novel biology that we haven't really observed before," Gustafson, who was not involved in the research, told Live Science.
However, while there's a strong association between the balance of these cell populations and disease risks, Artyomov emphasized that the study does not prove that this ratio directly causes the poor health outcomes. Further studies would be needed to understand why having more granzyme B cells is linked with poorer health.
"This observation might be just a consequence, not a cause of the disease," Artyomov noted.
It's also important to note that granzyme K-making cells in mice are not the same as granzyme K-making cells in humans. In mice, they represent a more mature, specialized stage of immune cell development, whereas in humans, granzyme B cells better fit that description, he told Live Science.
That points to a key way that immunity in mice and humans is different, which was "underappreciated" before, Gustafson said. So when we're comparing these cells in mice and humans, "we're not looking at apples to apples," she said. Scientists now specifically "need to look more into humans, as it's not reflected in animal models."
In people, immune cells' features can also vary across diverse human populations, Gustafson added. We need more data across different populations to get a "true understanding of universal immune health," she said. The K-to-B ratio may be a "novel" clue that can help scientists understand healthy aging, but more data is needed to unpack why and how that ratio is linked to healthy or unhealthy aging.
"This is kind of like the first step to be able to get there," she told Live Science.
This article is for informational purposes only and is not meant to offer medical advice.
'> Scientists have identified a 'protein signature' in blood that could predict healthy aging
The new tattoo ink is activated under UV light. (Image credit: Matter & Light, Bruns et al.)Researchers have developed a new type of tattoo ink that can be switched on and off with light, allowing colors and images embedded in the skin to be changed and even "erased" without having to go through the painful tattoo-removal process.
The system, which is being commercialized under the name PhotoTat, could eventually give people a way to conceal or change permanent body art. It could also have more practical applications, including medical tattoos that are visible only when a doctor needs to see them, researchers reported in a study published Friday (Oct. 9) in the journal Matter & Light.
"This is a tattoo that you can have, and whenever you decide you don't want it to be showing anymore, or you just don't want it there, you just turn it off," said study co-author Carson Bruns, an associate professor of biomedical engineering at the University of Colorado at Boulder. "And that's it. You don't have to turn it on again."
Working like a light switch
PhotoTat contains three primary color inks — blue, magenta and yellow — made with photochromic dyes, which are light-sensitive compounds that can change color with different wavelengths of light. These dyes are encapsulated in nanoparticles of polymethyl methacrylate (PMMA) — a medical-grade, glass-like plastic that is already used in medical implants and dermal fillers.
The dyes change their molecular structure when exposed to specific wavelengths of light. A 365-nanometer ultraviolet (UV) LED can activate pigments in around two to three seconds, Bruns said. Once activated, the colors can persist for hours to days under typical indoor lighting. But once the wearer exposes their skin to the bright outdoor sun, the colors disappear in seconds, erased by the intense light.
That makes the tattoo unique, as the pigment itself remains in the skin but the tattoo's appearance changes. Bruns and his team found that all three PhotoTat channels remained switchable in the skin for between 1.4 and 2.2 years.
Tattooing yourself for science
The three colors enable someone to activate different portions of a tattoo using different wavelengths of light. That means the magenta part of the tattoo might be turned on with green light, while the yellow pigment would be activated by blue light. This allows the wearer to customize their design and coloration to whatever they want at the moment — from a purple cherry to a yellow group of hearts.
That feature makes PhotoTat appealing for "people who love tattoos and have lots of tattoos, but just want something kind of fun and playful to add," Bruns told Live Science.
Bruns has tested each iteration of PhotoTat's inks on his own skin. His art is arranged in a series of tattooed scales, with different ink formations in individual scales.
"I gave myself these scales on purpose because they're each sort of a container for an experiment," Bruns said. The result, he joked, resembles a "magical mermaid trick," with some scales appearing out of nowhere and others changing color when activated.
The technology can also be combined with conventional tattoo ink. A permanent black ink design, for example, could contain hidden PhotoTat elements that appear only when activated.
The new tattoos could be appealing to people who want tattoos but are hesitant about their permanence, as well as to people who love their tattoos but occasionally need to conceal them because of work, social expectations or family, Bruns said.
"It's going to be on for most of the time, but just for this one moment, I'm going to turn it off for you grandma, for example," Bruns said.
Medical tattoos
Bruns thinks the tattoos could be helpful in a medical setting, too. Patients undergoing radiation therapy, for example, sometimes receive permanent tattoos that help doctors precisely align radiation beams. While useful, those marks remain after the treatment, reminding the patient of their experience. These would make such markings invisible if a patient wants them to be.
PhotoTat could potentially allow similar markings to be switched on during surgery and hidden afterward.
Bruns has spent several years developing other smart tattoos for medical applications, including a dosimeter-type tattoo that measures the amount of UV radiation a wearer experiences, along with a tattoo that changes color when the wearer is exposed to dangerous gamma radiation.
A cancer patient receives radiation treatment, guided by laser lines and a tattoo on their skin. (Image credit: The Washington Post via Getty Images)"It's not for you and me, but if you're like an astronaut or a nuclear engineer, they have to wear these dosimeters," Bruns said. "So, we have like a dosimeter tattoo that sort of puts that in your skin."
So far, Bruns and a fellow tattoo artist, have only commercialized the purple PhotoTat ink, after running the ink through a series of third-party medical tests.
The tests showed the purple is safe for use, and available to order, but it isn't cheap at $100 for a small bottle. Bruns hopes as more research is done, he can bring the other colors to market and lower the production cost, so the technology is more accessible.
'> Cool chemistry trick allows new tattoos to 'turn on and off'
generals. The lighthouse was built on the island of Pharos around 280 B.C. and stood more than 328 feet (100 meters) tall. Some ancient writers, such as Pliny the Elder, considered it among the wonders of the world, and it continued to be used into the Middle Ages, until earthquakes and erosion resulted in its destruction and disappearance beneath the sea.
While the lighthouse was modified over time, it would have had a statue, possibly of Zeus, at the top holding an oil lamp that helped guide mariners.
The newly discovered bronze signet ring has an image depicting the Lighthouse of Alexandria. (Image credit: Christoph Gerigk©Franck Goddio/Hilti Foundation)Whoever was wearing a signet ring could have used it to make an impression on soft materials, such as clay and wax, to create a seal. The discovery of the ring in the remains of the palace at Antirhodos suggests that the palace was used for administrative functions related to the lighthouse, representatives of IEASM said in the statement.
Even though the ring's engraving is somewhat worn, it likely depicts the lighthouse, said Doris Behrens-Abouseif, a professor emeritus of history of art and archaeology at the University of London who has written about the lighthouse but was not part of the research team.
There are "thousands of coins from Alexandria showing a similar depiction of the lighthouse," she told Live Science in an email. Those coins date to the Ptolemaic or Roman (29 B.C. to A.D. 395) periods, she noted.
Behrens-Abouseif added that she wasn't familiar enough with rings from Alexandria to comment on whether this is the only ring that contains this image.
Other scholars told Live Science that they, too, believe that this ring depicts the lighthouse, with two scholars noting that it may feature smoke coming from a lamp at top.
The "most interesting thing about the new signet ring engraved gem is an asymmetrical feature at its peak," which "may depict a plume of smoke from the oil lamp in the hand of the crowning statue," Andrew Chugg, an independent researcher who wrote the book "The Pharos Lighthouse in Alexandria: Second Sun and Seventh Wonder of Antiquity" (Routledge, 2024), said in an email.
Margaret Miles, a professor emeritus of art history and classics at the University of California, Irvine, also noticed the possible plume of smoke. Miles noted in an email that this "ring could have been used as a signet ring by a merchant from Alexandria who used the profile of the [lighthouse] to signal his location in Alexandria. The lighthouse was famous, so it became a symbol of the city."
Research off the coast of Alexandria over the past few years, including the discovery of 22 massive blocks, has revealed more information about the lighthouse, including how exactly it looked, which is helping researchers who are trying to digitally reconstruct it.
Are you a fan of mummies and hieroglyphs? Find out with our ancient Egypt quiz!
'> Bronze ring with Lighthouse of Alexandria engraving discovered at palace on submerged island in Egypt
The scientists outlined their findings about the robot's feat, which it achieved Nov. 17, 2024, in a study published Sept. 23 in the journal Nature.
This achievement represented a new milestone in overcoming a critical limitation for quadruped robots: endurance. Although four-legged robots can cross difficult terrain that wheeled machines struggle to traverse (like stairs and rugged trails), their endurance has been limited because powering multiple joints while repeatedly lifting and stabilizing the machine's body consumes huge amounts of energy.
"Unlike wheeled robots, quadrupeds continuously expend energy at their joints to support body weight and incur kinetic energy losses during intermittent foot-ground contact," the researchers wrote in the study.
RAIBO2's race was a demanding real-world trial. It took place during the Sangju Dried-Persimmon Marathon, with the bot racing alongside human participants. The route covered two 50-meter [164 feet] elevation climbs, with slopes of up to 10 degrees. Those kinds of gradients put increased strain on the robot's energy resources, stress-testing the bot's battery management capabilities, the scientists said.
RAIBO2 had previously run a 26.7-mile (43 km), GPS-guided route across a flat athletic field, which it knocked out in 4 hours, 40 minutes on one charge. However, an earlier marathon attempt across uneven terrain against other competitors had to be aborted around the 23-mile (37 km) mark after the robot's battery ran out. The robot's developers attributed that shortfall in part to frequent pace changes as the machine attempted to adjust to the pace of nearby runners.
To compensate, the team boosted the robot's battery capacity by 33% and tinkered with the control system, including implementing joint-stiffness control at the actuator. This allowed the bot to soften its leg when it had to absorb an impact or it needed a stable, forceful push-off. After the adjustments, RAIBO2 expanded to a maximum range of 41.6 miles (67 km) on a single charge, albeit on straight paths, according to the researchers.
Another key metric was RAIBO2's total cost of transport — a measure of the energy required to move a body over a given distance, with lower values indicating less energy expended. Researchers reported that RAIBO2 achieved a total cost of transport of 0.25, compared with a human benchmark of 0.37. The researchers said their machine was the first quadruped robot to surpass that figure.
The team attributed that efficiency to several optimizations across RAIBO2's software and hardware. Especially vital were its lightweight mechanical components, which were capable of transmitting kinetic energy from its joints with very little interference. They also credited a low-loss motor-driving circuit and, on the software side, a locomotion policy specifically streamlined to limit energy use. The system was also trained using the team's simulation environment, called RaiSim, which includes models of slopes, stairs and icy roads.
Like many electric vehicles, RAIBO2 can regenerate some battery by capturing kinetic energy, particularly while traveling downhill. That capability allows it to offset some of the energy it expends while climbing, though it doesn't eliminate the extra cost of hilly terrain.
The researchers said RAIBO2 has more than three times the travel range per charge of existing quadruped robots, with a total battery capacity of 2,016 watt-hours. It's in part because of that capacity increase that the team now estimates that the robot could travel up to 15.5 miles (25 km) farther than its marathon stint, up to a total of 41.6 miles (67 km).
That kind of endurance could broaden the roles for quadruped robots in places where wheeled models are impractical, the developers added in the study. For example, they could be useful in disaster zones and mountainous areas, where a sufficiently mobile, high-endurance robot could carry cameras, sensors or communications gear across uneven terrain.
'> South Korean 'robot dog' became first to run a marathon on a single battery charge — now we know how Proteins constantly access DNA, loading up the information written in its code and taking that data away to be turned into new proteins for the cell. But these methyl groups can act as tiny roadblocks that stop that process in its tracks.
These groups are one type of "epigenetic marker," which collectively help to control gene activity, and their arrangement on DNA changes predictably as animals age, study co-author Blaise Mariner, a bioinformatician at Arizona State University, told Live Science. Across many studies and species, including humans, scientists have used this data to build epigenetic clocks that track animals' biological ages.
Dogs happen to be a great species for studying aging. Their owners devotedly track what they eat, how they live, and how their health changes over time. So Mariner and his colleagues built epigenetic clocks using DNA in blood samples taken from 894 dogs enrolled in the long-term Dog Aging Project based at the University of Washington.
These samples revealed how the dogs' immune cells aged. These cells patrol the whole body, so "they're a really good measure of systemic aging," study co-author Noah Snyder-Mackler, a genomicist at Arizona State University, told Live Science.
The team found that changes in DNA methylation closely tracked biological aging, in that the dogs with older-than-expected epigenetic ages had a higher risk of death from any cause. Once they looked at how different sizes of dogs aged, clear differences emerged.
"Using our biomarker, this epigenetic clock, big dogs were aging a little bit faster per year of life than small dogs," Snyder-Mackler said.
A key epigenetic change linked to larger body size was the loss of methyl groups at stretches of DNA called transposable elements. Also called "jumping genes," these elements can potentially move around the genome, but the methyl groups help stop them from doing so. But when that methylation is lost, the jumping genes can become too active and end up damaging other genes and causing inflammation, a key process that ramps up with age.
In short, the new data suggests that out-of-control jumping genes may contribute to big dogs' faster aging.
Researchers created epigenetic clocks based on data from 894 dogs. (Image credit: Josh Hawley via Getty Images)In aging dogs, the team found that some regions of the genome with few chemical tags became more methylated, while other areas that had been choked with methyl groups gradually lost them. Additionally, at least in terms of their epigenetics, dogs' immune cells appear to become more similar to one another as they age. Mariner said this "loss of cell identity" is a key hypothesis for what happens to the body as it ages.
Immune cells are carefully specialized for different roles, such as preventing cancer or killing viruses. As these cells become more similar to one another, they become less able to fulfill their specialized roles, studies suggest.
Humans have bred big dogs for size, and Snyder-Mackler said this push for large body size may have come at a cost.
"Their bodies have to make this trade-off between really rapid growth and maintenance of that," he said, "versus investment in the immune system and integrity of the organism." For now, that idea is a hypothesis, though, as the current study doesn't directly address why big dogs' epigenetic aging has come to be this way.
Now, the team wants to build more informative clocks as the Dog Aging Project recruits more pooches to follow for longer periods. Snyder-Mackler said the team's data currently explains only part of how dogs' epigenetic ages vary. "What we really want to know is, what explains the rest of that variation?" he said.
The team was keen to build predictive models that might help dog owners anticipate their pets' age-related health concerns, Snyder-Mackler added.
What we learn about dogs from these studies may help us understand human aging, too. That's partly because dogs get some of the same diseases we do, but it's chiefly because they share humans' living spaces and environments.
"We're going to start looking, at the molecular level, [at] how these environmental exposures or experiences impact health and aging in dogs, which is going to be directly translatable to humans who are living in those same exact environments," Snyder-Mackler said.
"Most people love dogs," he added. "That means we can get a lot of really good data on them."
'> Big dogs age faster at an epigenetic level, new study finds