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Gut microbes help hibernating ground squirrels emerge strong and healthy in spring – Phys.org

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Ground squirrels spend the end of summer gorging on food, preparing for hibernation. They need to store a lot of energy as fat, which becomes their primary fuel source underground in their hibernation burrows all winter long.

While hibernating, ground squirrels enter a state called torpor. Their metabolism drops to as low as just 1% of summer levels and their body temperature can plummet to close to freezing. Torpor greatly reduces how much energy the animal needs to stay alive until springtime.

That long fast comes with a downside: no new input of , which is crucial to maintain the body’s tissues and organs. This is a particular problem for muscles. In people, long periods of inactivity, like prolonged bed rest, lead to muscle wasting. But muscle wasting is minimal in hibernating animals. Despite as much as six to nine months of inactivity and no protein intake, they preserve muscle mass and performance remarkably well—a very handy adaptation that helps ensure a successful breeding season come spring.

How do hibernators pull this off? It’s been a real head-scratcher for hibernation biologists for decades. Our research team tackled this question by investigating how hibernating animals might be getting a major assist from the microbes that live in their guts.

A nitrogen-recycling system

We knew from previous research that a hibernator’s gastrointestinal system undergoes dramatic changes in its structure and function from summer feeding to winter fasting. And it’s not only the animals who are fasting all winter long—their are, too. Along with our microbiology collaborators, we figured out that winter fasting changes the gut microbiome quite a bit.

And then we wondered … could gut microbes play a functional role in the process of hibernation itself? Could certain bacteria help keep muscle and other tissues working when the mostly immobile animals aren’t eating?

Biologists had previously identified a clever trick in ruminant animals, such as cattle, that helps them survive times when protein intake in the diet is low or protein needs are especially high, such as during pregnancy. A process called urea nitrogen salvage allows the animal to recoup nitrogen—a critical ingredient for building protein—that would otherwise be excreted in urine as the waste product . Instead, the urea’s nitrogen is retained in the body and used to make amino acids, the building blocks of proteins.

<div data-thumb="https://scx1.b-cdn.net/csz/news/tmb/2022/gut-microbes-help-hibe-1.jpg" data-src="https://scx2.b-cdn.net/gfx/news/2022/gut-microbes-help-hibe-1.jpg" data-sub-html="The 13-lined ground squirrel shows minimal signs of muscle wasting, even after hibernating for up to six months. Credit: Robert Streiffer, CC BY“>
<img src="https://scx1.b-cdn.net/csz/news/800a/2022/gut-microbes-help-hibe-1.jpg" alt="Gut microbes help hibernating ground squirrels emerge strong and healthy in spring" title="The 13-lined ground squirrel shows minimal signs of muscle wasting, even after hibernating for up to six months. Credit: Robert Streiffer, CC BY“>
The 13-lined ground squirrel shows minimal signs of muscle wasting, even after hibernating for up to six months. Credit: Robert Streiffer, CC BY

This salvage operation depends on the chemical breakdown of urea molecules to release their nitrogen. But here’s the kicker: Chemical breakdown of urea requires urease, an enzyme that animals do not produce. So how does a cow, for instance, get that nitrogen out of urea?

It turns out certain microbes that are normal residents of animals’ guts can do just that. They make the urease enzyme and use it to chemically split urea molecules, freeing up the nitrogen, which becomes part of ammonia molecules. Microbes then absorb ammonia and use it to make new protein for themselves.

Peculiarities of the ruminant digestive system allow those animals to benefit greatly from this process. But for other animals—like hibernators and us—it was less clear whether and how the urea nitrogen could make its way into the animals’ bodies to support protein synthesis.

This was our challenge as scientists: Could we demonstrate urea nitrogen recycling in hibernators and show that it is particularly helpful to them the longer they fast?

Our experimental game plan

Using the 13-lined ground squirrel, we designed experiments to investigate key steps in urea nitrogen salvage.

First, we injected into the squirrel’s bloodstream urea molecules in which the two were replaced by a heavier form of nitrogen that naturally occurs only in tiny amounts in the body.

We were able to follow these heavier nitrogen atoms as the injected urea moved from the blood into the gut, then as microbial urease broke down the urea into its component parts, and finally into the squirrels’ tissue metabolites and proteins. Wherever we saw higher levels of the heavier form of nitrogen, we knew that urea was the source of the nitrogen, and therefore gut microbes had to be responsible for getting the urea nitrogen back into the animals’ bodies.

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Every few weeks, hibernating squirrels arouse temporarily, as seen in this time-lapse video. They don’t eat or drink or leave the burrow, but the short increase in body temperature lets enzymes like urease do their jobs.

To confirm that the microbes were doing the nitrogen recycling, we compared squirrels that had normal gut microbiomes to squirrels that didn’t. We treated some animals with antibiotics to reduce gut microbes at three times of the year: summer; early winter, when they were one month into fasting and hibernation; and late winter, whwithen they were four months into fasting and hibernation.

In squirrels with normal microbiomes, we saw evidence of urea nitrogen salvage at each step of the process that we tested. But squirrels with depleted microbiomes displayed minimal urea nitrogen salvage. Our observations confirmed that this process was indeed dependent on the gut microbes’ ability to break down urea and liberate its nitrogen in the hibernators’ guts. Hibernators’ liver and muscle tissue incorporated the most urea nitrogen during late winter—that is, the longer they’d been hibernating and without food.

We also found that the ground squirrels contribute to this remarkable symbiosis. During hibernation, their gut cells increase production of proteins called urea transporters. These molecules are lodged in intestinal cell membranes and shepherd urea from the blood into the gut where the microbes that contain urease are found. This assist means that what little urea the animal makes during hibernation has an easier route to the gut.

Finally, we found that it wasn’t just squirrels who benefited from this process. The microbes too were using the urea nitrogen to build their own proteins, showing that urea nitrogen salvage provides both parties with this important molecular building block during the long winter fast.

Could this kind of symbiosis help humans?

This example of hibernator-microbe symbiosis has potential clinical applications. For example, undernourishment, which affects millions of people globally, leads to a progressive decline in and compromises health. Sarcopenia, which is muscle wasting that is a natural part of aging, impairs mobility and makes people more susceptible to injury. A detailed understanding of how the hibernator salvage system is most effective when the risk of tissue loss and muscle wasting is greatest could lead to new therapeutics to help people in similar situations.

Another potential application is in human spaceflight, during which crew members experience high rates of muscle atrophy because of a microgravity-induced suppression of muscle protein synthesis. Even the extensive exercise regime that astronauts undertake to offset this is insufficient. A microbiome-based countermeasure that facilitates muscle protein synthesis similar to the process we have observed in hibernators may be worth investigating.

These applications, though theoretically possible, are a long way from delivery. But studies in the 1990s demonstrated that humans are capable of recycling small amounts of urea nitrogen with the help of their gut microbes. So the necessary machinery is in place—it just needs to be optimized.


Explore further

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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