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Pink Muscles

National Museum of American History

What Makes Muscles Twitch?

Smithsonian Magazine

Calcined Muscles, Raw Material

NMNH - Anthropology Dept.

Sketch for "Corsets with Cross Muscles"

Cooper Hewitt, Smithsonian Design Museum

Jaw muscles of old world squirrels

Smithsonian Libraries
The jaw, suprahyoid, and extrinsic tongue muscles were studied in 11 genera, belonging to five tribes, of Old World squirrels. Significant variation in most of the adductor muscles is evident. The most primitive state of sciuromorphy is seen in the African tree squirrels Paraxerus and Funisciurus, especially as reflected in the anterior deep masseter. A derived state of sciuromorphy is found in five genera of Old World squirrels and perhaps evolved independently in each. Reduction of the temporalis muscle was observed in three genera, distantly related to one another. A unique arrangement of the superficial masseter is reported in the Asian giant tree squirrels, Ratufa. The arrangement of the masseter in the African pygmy squirrel, Myosciurus, is very similar to that of the South American pygmy squirrel, Sciurillus. We present hypotheses about the functional significance of these differences. In the derived state of sciuromorphy, which is found in three cases in squirrels that feed extensively on hard fruits, the anterior deep masseter is well positioned to increase the strength of the power stroke of the incisor bite. Among the pygmy squirrels, the position of the anterior deep masseter suggests that it plays a more significant role in molar chewing. (C) 1996 Wiley-Liss, Inc.

lever, muscle

National Museum of American History

Veggie Power? Artificial Muscles Made From Blinged-Out Onions

Smithsonian Magazine

Popeye made spinach famous as a muscle-building vegetable. But veggies might someday make you stronger without being eaten—when scientists use them to build a new class of artificial muscles. This week a team in Taiwan unveiled gold-plated onion cells that show promise at expanding, contracting and flexing in different directions just like real muscle tissue.

Artificial muscles have a wide range of possible applications, from helping injured humans to powering robots, and there are lots of ways to try to build them. Last year, for instance, scientists developed a set of artificial muscles from simple fishing line that could lift 100 times more than human muscles of the same size and weight. But no clearly superior way to make a fake muscle has yet emerged.

“There are artificial muscles developed using elastomers, shape memory alloys, piezoelectric composites, ion-conductive polymers and carbon nanotubes,” says Wen-Pin Shih of National Taiwan University in Taipei. “The driving mechanisms and functions are very diverse.” Some artificial muscle types are driven by pressure, such as in pneumatic systems, while others create motion through temperature changes or electrical current.   

A major challenge for artificial muscle makers has been engineering their materials to bend and contract at the same time, the way real muscles do. When someone flexes the classic “make a muscle” pose, for example, their biceps contract but also bend upwards to lift the forearm. Shih and colleagues were attempting to engineer an artificial muscle that could simultaneously bend and contract in this way, and they found that the structure and dimensions of onion skin were very similar to the microstructure they had in mind.

To put the pungent vegetable to the test, Shih's group first took a single layer of epidermal cells from a fresh, peeled onion and washed it clean with water. Then the team freeze-dried the onion to remove the water while leaving its cell walls intact. That process turned the microstructure rigid and brittle, so they treated the onion with acid to remove a cell-stiffening protein called hemicellulose and restore elasticity.

The onion layers were made to move like muscles by turning them into an electrostatic actuator. This meant coating them with gold electrodes, which conduct current. The gold was applied in two thicknesses—24 nanometers on top and 50 nanometers on bottom—to create different bending stiffnesses and make the cells flex and stretch in lifelike ways. This paired nicely with the natural tendency of onion skin to bend in different directions when subjected to different voltages due to electrostatic attraction. 

The team made muscle-like "tweezers" from onion skin cells. (Shih Lab, National Taiwan University)

Lower voltages of 0 to 50 volts caused the cells to elongate and flatten out from their original curved structure, while higher voltages of 50 to 1000 volts caused the veggie muscle to contract and bend upwards. By controlling these voltages to vary muscle movements, two of the onion arrangements were used as tweezers to grip a small cotton ball, Shih and colleagues report this week in Applied Physics Letters.

But that success required relatively high voltage, which Shih calls the concept's main drawback to date. Lower voltages are needed to control the muscle with tiny batteries or microprocessor components, which would be better suited to power implants or robot parts. “We will have to understand the configuration and mechanical properties of the cell walls better to overcome this challenge,” he notes.

The onion cells provide some advantages over previous attempts to use living muscle cells to create artificial tissue, Shih says. “Culturing cells to form a piece of muscle tissue for generating pulling strength is still very challenging,” Shih says. “People have tried to use live muscle before. But then how to keep the muscle cells alive becomes a problem. We use vegetable cells because the cell walls provide muscle strength whether the cells are alive or not.”

Durability is an issue, though: The gold plating helped shield the onion muscles, but moisture can still penetrate their cell walls and change the material properties. Shih has an idea to tackle this problem, which could soon be put to the test. “We might coat the onion artificial muscle with a very thin fluoride layer,” he says. “That will make the artificial muscle impermeable to moisture but won’t change the device softness.”

Genetically Edited Hercules Dogs Can Pack on Extra Muscles

Smithsonian Magazine

From the country that brought you genetically altered micropigs, comes another announcement that pushes the limits of gene editing. A Chinese team from Guangzhou Institutes of Biomedicine and Health recently presented the world with a pair of super-muscled beagles: Hercules and Tiangou.

Already other research groups have tweaked the genes of monkeys, goats, rabbits and even human embryonic cells using a relatively new technology called CRISPR—a system that uses enzymes to cut and paste select segments of DNA. 

Using this method, researchers disabled the gene that codes for myostatin, a protein produced by muscle cells that actually blocks muscle growth. This mutation has cropped up on its own, without scientists wielding gene editing tools, in the beef cattle breed Belgian Blue, racing whippets and humans.

The team injected the gene editor system into 35 beagle embryos. Of the 27 puppies born, only two had the edited genes. Hercules has the mutation in most, but not all of his cells. Yet at four months, the changes were most evident in Tiangou—named for a mythological dog from Chinese legend that eats the sun during an eclipse—who sported more muscular thighs than her unedited sister, reports Tina Hesman Saey for Science News. But now at 14 months, both pups have packed on muscle.

The beagles have "more muscles and are expected to have stronger running ability, which is good for hunting, police (military) applications," one of the researchers Liangxue Lai tells Antonio Regalado of Technology Review. But the ultimate goal of this work is to raise animals with genetic alterations that mimic human diseases like Parkinson's, George Dvorsky reports for Gizmodo. Lai and colleagues published their work earlier this month in the Journal of Molecular and Cell Biology.

They don’t plan to create specialized pets, but that doesn’t mean other groups won’t try, reports Regalado for Technology Review. Given that another Chinese research group is selling genetically edited mini pigs, pets wouldn't be out of the realm of possibility.

While, the micropigs’ genes were tweaked using a different kind of gene editing enzyme, the CRISPR system is considered more powerful and precise. That means even more possibilities. Regalado writes:

[A]t least some researchers think that gene-edited dogs could put a furry, friendly face on the technology. In an interview this month, George Church, a professor at Harvard University who leads a large effort to employ CRISPR editing, said he thinks it will be possible to augment dogs by using DNA edits to make them live longer or simply make them smarter.

The low rate of success for the dogs (two out of 27 puppies) shows that the technology has a ways to go before designer pets are readily available. But the debate is already boiling over the ethics of such gene editing. And as the technology improves, that debate will only intensify. 

levers, muscle, gravity

National Museum of American History

Muscle Beach

Smithsonian Magazine

In the beginning, it really wasn't about muscles. It was about fitness and fun. The focus of attention at the original Muscle Beach, back in the 1930s, '40s and '50s, was acrobats strong young men and women who did somersaults and handstands, built human towers and threw each other around. Later the venue moved to another Muscle Beach in Venice, and the emphasis shifted to bodybuilding.

But in the good old days, huge crowds gathered in Santa Monica to watch muscle men bench-press bathing beauties instead of barbells. The colorful cast of characters included Paula Boelsems, who taught an elephant how to water-ski; George Eiferman, who played a trumpet with one hand while lifting weights with the other; and Abbye "Pudgy" Stockton, a dainty acrobat who was the first great female weightlifter. A number of other Santa Monica regulars have long since become household names, including Vic Tanny, Jack LaLanne and Joe Gold, all of whom made fitness their business.

The original Muscle Beach was a sunny universe, a place of cheerful optimism that had a certain sweetness to it. The message it sent the world was largely that there was a connection between body and mind--that the body, in fact, could rule the mind. It was, Jack LaLanne once said, "such a perfect place to show kids that anything was possible." A lot of people today are in bodybuilding for money and fame. Old-timers complain that it's not as much fun as it used to be. "Every day," the aging acrobat Glenn Sundby remembers, "was a day to look forward to."

heart, artificial; pouch, muscle-powered

National Museum of American History

heart, artificial; pouch, muscle-powered

National Museum of American History

Muscle Tussle

National Museum of American History

The Ultra-Strong Robotic Muscles of the Future Could Be Made From Fishing Line

Smithsonian Magazine

The next artificial muscle, for either robotics or medical applications, will need to be strong, and it will need to be flexible. Right now, carbon nanotubes reign supreme as the strongest artificial muscle, while materials such as spider silk come in as close possible seconds. But now a new material breakthrough has entered the artificial muscle arena, and it could beat its competitors down. And this muscle is made out of fishing line, of all things. 

Here's i09 on the discovery

How do you get muscle out of a fishing line? First, you have to create tension that can be released.

It's a simple process that goes by an equally simple moniker: "twist insertion."

One end of a high-strength polymer fiber (like a 50 pound test-line, for example, available at pretty much any sporting goods store) is held fast, while the other is weighted and twisted. Twist a little and the line becomes an artificial "torsional" muscle that exerts energy by spinning. Twist a lot, however, and something interesting happens: the cord coils over on itself, creating an ordered series of stacking loops.

When you do this to a piece of fishing line, researchers discovered, it turns into an artificial tensile muscle that can contract, just like our own muscles, i09 says. To test the fishing line's strength, the researchers applied hot and cold temperatures—a standard means of testing material properties—which caused the artificial muscle to contract and relax. In this way, they could coax four interwoven artificial muscles into lifting 30-pound weights, for example. Sewing thread, they also found, demonstrates similar properties when treated this way.

After performing a number of tests, the researchers found that the artificial muscles could "generate about seven horsepower of mechanical power per kilogram of polymer fiber," i09 writes. The study authors put this into perspective: that means the fishing line can "lift loads over 100 times heavier than can human muscle of the same length and weight" and can perform mechancial work about equivalent to that of a jet engine. 

How Artificial Muscles Could Transform the Lives of Some Military Veterans

Smithsonian Magazine

Injury is a sad fact of military service, especially in wartime. According to a study performed by scientists at the Uniformed Services University of the Health Sciences, by far the most frequent is soft tissue injuries to skin, fat and muscle.

Of these, muscle damage is particularly difficult to heal. Beyond a certain size—about one cubic centimeter—the body simply cannot do it. As a result, people experiencing this kind of trauma, called volumetric muscle loss, lose function of the muscle, and experience deformation, scar tissue or contracted muscles.

According to a study from 2015 in the Journal of Rehabilitation Research and Development (a peer-reviewed publication put out by the Department of Veterans Affairs), volumetric muscle loss is typically permanent.

“The current primary standard of care for [volumetric muscle loss] injuries is physical rehabilitation,” says Benjamin Corona, lead author of the study. “The documented cases available do not indicate significant functional recovery unless energy returning orthoses [braces or other devices] are used. Physical rehabilitation alone will not promote regeneration of the lost tissue.”

Corona and his team of researchers looked at the records of more than 500 service members who were discharged from the military due to injuries between 2001 and 2007. They found that most broken bones sustained in combat result in open wounds, and that while the bone can often be repaired, the muscle is left damaged. Service members who sustained broken bones are often disqualified from service not because of the break, but because of disability due to the soft-tissue wound.

“Despite a tremendous amount of attention given to bone healing after type III open tibia fracture, based on the current findings it is appropriate to conclude that soft-tissue complications make the majority contribution to disability of salvaged limbs,” the authors wrote. “The development of therapies addressing [volumetric muscle loss] has the potential to fill a significant void in orthopedic care.”

Historically, the best course of treatment was to use a flap of muscle, either from a different part of the body or rotated from a connected muscle, to cover the wound. This helps to heal, but cannot provide the normal use of an uninjured muscle, and so the limb where the injury occurred is often permanently disabled.

“There have been a lot of attempts to replace lost muscle,” says Li Ting Huang, a staff scientist at Acelity, a biotech company that provides regenerative technology to the Department of Defense. “Those [muscle flap transfers] generally don’t work too well, because for a muscle to function it needs the enervation, it needs to have nerves running through it. So you need to kind of reconnect all of the nerves and blood vessels as well, to keep the implanted muscle alive and functioning. This is something that is very difficult to do.”

Huang is leading a new muscle regeneration technology project, which aims to modify the company’s existing technology to solve volumetric muscle loss.

“The main thing is, obviously there’s the large unmet clinical need for a product like this, especially for the patient population that we’re looking at, for military servicemen and women,” says Huang.

Acelity rebranded a couple of years ago, but its core businesses are in wound regeneration, and its products can be found in military and veteran’s hospitals, as well as public ones, and even in war zones. Primarily, they include negative pressure wound therapy (which draws out fluid and brings blood to the wound), webs of organic material called tissue matrices for skin wound recovery, and a preservation solution that keeps the tissue matrices viable for up to two years.

Those matrices are what Huang is jumping off from as she builds her muscle regeneration technology.

She starts with a pig muscle, and uses a proprietary process that strips the tissue of all cell components, which can cause inflammation or even be rejected by the body. The resulting material, called an acellular muscle matrix, looks eerily like real muscle, complete with texture and fibers, except it is pale and almost translucent.

Then, the matrix is surgically implanted, taking care to align it to match the existing tissue. With rehabilitation and therapy to help the existing muscle tissue grow, Huang argues it can mend the muscle back together.

A more recent paper in Biomaterials by Corona examines the use of acellular matrices in healing volumetric muscle loss. His conclusion is less rosy, concluding that while muscle recovery occurs, it is not to such a degree as to offer the power needed for the muscle to operate. “The existing data do not support the capacity of acellular biological scaffolds to promote a physiologically meaningful volume of skeletal muscle tissue,” Corona and co-author Sarah Greising wrote. That said, they add that “acellular biological scaffolds remain a vital tool for VML repair that should continue to be developed in conjunction with other biomaterial, biological, and rehabilitative therapeutic strategies.”

Huang says she has gotten the process to work in rats. Next comes larger animals, and she isn’t keen to speculate farther than that, though she says she is working to expand the size of the matrices, which were originally about six centimeters square.

“Personally, for me, this project has been one of the most satisfying projects I’ve worked on,” she says. “Especially since it can help a patient population that has sacrificed so much for our country.”

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