Study: 'Mighty mice' stayed strong in space with gene treatment
Targeting a signaling pathway in mice helped them retain muscle and bone mass aboard the International Space Station, according to a new study.
- Losing bone and muscle mass in space is a major health concern for astronauts.
- In a recent study, scientists genetically altered mice and sent them to the International Space Station.
- The genetically altered mice retained — or even gained — muscle and bone mass, while a control group suffered significant losses.
Living in microgravity aboard the International Space Station (ISS) might seem like it'd be gentle on the human body, but it's not. Without gravity, the musculoskeletal system starts to atrophy because it no longer needs to support any weight. And even though regular exercise in space keeps astronauts in decent shape, bone and muscle loss remains a major health concern for long-term space missions.
A new study published in the Proceedings of the National Academy of Sciences suggests that targeting a specific signaling pathway in the body can help prevent bone and muscle loss in space.
The study involved sending 40 mice to the ISS for a month-long stay. Eight of the mice were missing the gene for myostatin, a protein known to inhibit muscle growth. Another eight mice were given a treatment that suppresses myostatin and the protein activin A, which also helps to regulate muscle mass. The rest of the mice (24) were left untreated as a control group.
Comparison of bone density loss between the mice groups.
(Image credit: Se-Jin Lee)
Upon return to Earth, the untreated mice showed significant losses in muscle mass and bone density. But the mice missing the myostatin gene retained almost all of their muscle and bone mass. What's more, the mice that received the gene-inhibiting treatment actually gained bone and muscle mass. The researchers observed similar results among a separate group of mice that were given the same set of treatments on Earth.
"These findings show that blocking the activities of these hormones does work to enhance both muscle and bone even when mice are unable to bear weight," study authors Se-Jin Lee and Emily L. Germain-Lee told CNN.
"One thing that we found somewhat surprising is how resilient mice are even when subjected to all of the stresses associated with space travel. We knew that mice had been sent to space in the past, but we still found it remarkable that after spending a month at the ISS, they seemed to resume normal activity very quickly after returning to Earth."
Treatments like these could protect astronauts on future long-term space missions. After all, studies show that spending just 16 to 28 weeks in space can cause a 3.5-percent loss in bone density, so space agencies are understandably concerned about the health risks of sending astronauts on a three-year mission to Mars.
Applications on Earth
The researchers also noted that "this strategy may be effective in preventing or treating muscle and bone loss not only in astronauts on prolonged missions but also in people with disuse atrophy on Earth, such as in older adults or in individuals who are bedridden or wheelchair-bound from illness."
Still, the experiment was done on mice, so it's not clear whether the treatment would have the same effects on humans. It's also unclear what other side effects the treatment might have on humans. Answering these questions will take some time.
"We're years away," Germain-Lee told Phys Org. "But that's how everything is when you go from mouse to human studies."
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The idea of 'absolute time' is an illusion. Physics and subjective experience reveal why.
- Since Einstein posited his theory of general relativity, we've understood that gravity has the power to warp space and time.
- This "time dilation" effect occurs even at small levels.
- Outside of physics, we experience distortions in how we perceive time — sometimes to a startling extent.
Physics without time<p>In his book "The Order of Time," Italian theoretical physicist Carlo Rovelli suggests that our perception of time — our sense that time is forever flowing forward — could be a highly subjective projection. After all, when you look at reality on the smallest scale (using equations of quantum gravity, at least), time vanishes.</p><p style="margin-left: 20px;">"If I observe the microscopic state of things," writes Rovelli, "then the difference between past and future vanishes … in the elementary grammar of things, there is no distinction between 'cause' and 'effect.'"</p><p>So, why do we perceive time as flowing <em>forward</em>? Rovelli notes that, although time disappears on extremely small scales, we still obviously perceive events occur sequentially in reality. In other words, we observe entropy: Order changing into disorder; an egg cracking and getting scrambled.</p><p>Rovelli says key aspects of time are described by the second law of thermodynamics, which states that heat always passes from hot to cold. This is a one-way street. For example, an ice cube melts into a hot cup of tea, never the reverse. Rovelli suggests a similar phenomenon might explain why we're only able to perceive the past and not the future.</p><p style="margin-left: 20px;">"Any time the future is definitely distinguishable from the past, there is something like heat involved," Rovelli wrote for the <a href="https://www.ft.com/content/ce6ef7b8-429a-11e8-93cf-67ac3a6482fd" target="_blank"><em>Financial Times</em></a>. "Thermodynamics traces the direction of time to something called the 'low entropy of the past', a still mysterious phenomenon on which discussions rage."</p>
The strange subjectivity of time<p>Time moves differently atop a mountain than it does on a beach. But you don't need to travel any distance at all to experience strange distortions in your perception of time. In moments of life-or-death fear, for example, your brain would release large amounts of adrenaline, which would speed up your internal clock, causing you to perceive the outside world as moving slowly.<br></p><p>Another common distortion occurs when we focus our attention in particular ways.</p><p style="margin-left: 20px;">"If you're thinking about how time is <em>currently</em> passing by, the biggest factor influencing your time perception is attention," Aaron Sackett, associate professor of marketing at the University of St. Thomas, told <em><a href="https://gizmodo.com/why-does-time-slow-down-and-speed-up-1840133782" target="_blank">Gizmodo</a></em>.<em> "</em>The more attention you give to the passage of time, the slower it tends to go. As you become distracted from time's passing—perhaps by something interesting happening nearby, or a good daydreaming session—you're more likely to lose track of time, giving you the feeling that it's slipping by more quickly than before. "Time flies when you're having fun," they say, but really, it's more like "time flies when you're thinking about other things." That's why time will also often fly by when you're definitely <em>not</em> having fun—like when you're having a heated argument or are terrified about an upcoming presentation."</p><p>One of the most mysterious ways people experience time-perception distortions is through psychedelic drugs. In an interview with <a href="https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-exploding-commonsense-notions-order-of-time-interview" target="_blank"><em>The Guardian</em></a>, Rovelli described a time he experimented with LSD.</p><p style="margin-left: 20px;">"It was an extraordinarily strong experience that touched me also intellectually," he said. "Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more. It was a total subversion of the structure of reality."<br></p><p>It seems few scientists or philosophers believe time is completely an illusion.</p><p style="margin-left: 20px;">"What we call <em>time</em> is a rich, stratified concept; it has many layers," Rovelli told <em><a href="https://physicstoday.scitation.org/do/10.1063/PT.6.4.20190219a/full/" target="_blank">Physics Today</a>.</em> "Some of time's layers apply only at limited scales within limited domains. This does not make them illusions."</p>What <em>is</em> an illusion is the idea that time flows at an absolute rate. The river of time might be flowing forever forward, but it moves at different speeds, between people, and even within your own mind.
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