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Scientific Studies Using Mice May Be Hard to Replicate Due to Gut Microbes
Scientists are concerned that the results of studies using mice may be affected by gut bacteria.
Mice and other rodents are a staple of laboratory research. In fact, mice are the most commonly used vertebrate species. They are popular because you can get them easily and cheaply, they are small, reproduce quickly, share 99% of their genes with humans, and can be utilized to study genetic human diseases. But studies that rely on mice may potentially be difficult to replicate due to the differing gut contents of the rodents.
Laura McCabe, a physiologist from Michigan State University (MSU), found that the laboratory mice they were using had different microbes in their guts. This skewed the results of their experiments on how a particular drug affects bone density since the drug's effects varied based on what was inside each mouse. Some mice lost bone density while some gained it.
A "microbiome" is a term used to refer to gut bacteria but also to other inhabitants of the gut, like viruses, fungi, and protozoa. The impact of the microbiome on varying experimental data has been coming under increased scrutiny in the scientific community.
"We didn’t know to look for it before,” said MSU's veterinarian Clair Hankenson to Science Magazine.
To try to standardize what's inside the mice, it has been relatively standard procedure for scientists to be careful in controlling where the mice come from - looking to get animals from the same vendor, keeping them in sterile environments, trying to account for any other factors.
Yet, this approach may not be achieving the desired effect. The gut bacteria in mice can change for reasons like a change in their diet, a new stress, or where and how they were kept by the vendors. For instance, in one instance, mice from one vendor were found lacking segmented filamentous bacteria (SFB), which were shown to help mice make crucial antibodies and immune cells. The presence or absense of this bacteria could affect studies of inflammatory response.
A worker observes white rats at an animal laboratory of a medical school in Chongqing Municipality, China. (Photo by China Photos/Getty Images)
One line of thinking also looks at whether it may not be a good idea to keep lab environments super-sterile. By cleaning, labs might be wiping out some of the microbial variety that make mice good subjects for studying human diseases in the first place. A 2016 study, led by immunologist David Masopust from the University of Minnesota, Twin Cities, found that mice bought from a pet store ended up exhibiting diseases like hepatitis and phenumonia, which have generally been eradicated from lab mice. Exposure to the diseases killed off a chunk of the lab mice but allowed others to build up immunity, thus becoming more realistic stand-ins for the human immune system, according to the scientists.
Another lab doing immunology studies has tried this approach with success. “My lab is incredibly excited about this,” said Stephen McSorley, an immunologist from the University of California, Davis, School of Veterinary Medicine. Their lab bought a “dirty” colony of mice that normally serve as zoo animals. This approach, however, has some detractors as well, as it goes against the usual cleanliness-obsessed culture at most labs.
As scientists zero in on the importance of factors that might be influencing the microbiomes of lab mice, they are looking for more ways to account for them in the research. Among proposed ways to counteract the gut’s influences is controlling for the diets of the mice and any potential exposure to antibiotics, including fecal microbiome analysis with the data, testing multiple types of microbiomes, and designing studies that separate the effects of microbial genes from the genes of their animal hosts.
Innovation in manufacturing has crawled since the 1950s. That's about to speed up.
Health officials in China reported that a man was infected with bubonic plague, the infectious disease that caused the Black Death.
- The case was reported in the city of Bayannur, which has issued a level-three plague prevention warning.
- Modern antibiotics can effectively treat bubonic plague, which spreads mainly by fleas.
- Chinese health officials are also monitoring a newly discovered type of swine flu that has the potential to develop into a pandemic virus.
Bacteria under microscope
needpix.com<p>Today, bubonic plague can be treated effectively with antibiotics.</p><p style="margin-left: 20px;">"Unlike in the 14th century, we now have an understanding of how this disease is transmitted," Dr. Shanthi Kappagoda, an infectious disease physician at Stanford Health Care, told <a href="https://www.healthline.com/health-news/seriously-dont-worry-about-the-plague#Heres-how-the-plague-spreads" target="_blank">Healthline</a>. "We know how to prevent it — avoid handling sick or dead animals in areas where there is transmission. We are also able to treat patients who are infected with effective antibiotics, and can give antibiotics to people who may have been exposed to the bacteria [and] prevent them [from] getting sick."</p>
This plague patient is displaying a swollen, ruptured inguinal lymph node, or buboe.
Centers for Disease Control and Prevention<p>Still, hundreds of people develop bubonic plague every year. In the U.S., a handful of cases occur annually, particularly in New Mexico, Arizona and Colorado, <a href="https://www.cdc.gov/plague/faq/index.html" target="_blank">where habitats allow the bacteria to spread more easily among wild rodent populations</a>. But these cases are very rare, mainly because you need to be in close contact with rodents in order to get infected. And though plague can spread from human to human, this <a href="https://www.healthline.com/health-news/seriously-dont-worry-about-the-plague#Heres-how-the-plague-spreads" target="_blank">only occurs with pneumonic plague</a>, and transmission is also rare.</p>
A new swine flu in China<p>Last week, researchers in China also reported another public health concern: a new virus that has "all the essential hallmarks" of a pandemic virus.<br></p><p>In a paper published in the <a href="https://www.pnas.org/content/early/2020/06/23/1921186117" target="_blank">Proceedings of the National Academy of Sciences</a>, researchers say the virus was discovered in pigs in China, and it descended from the H1N1 virus, commonly called "swine flu." That virus was able to transmit from human to human, and it killed an estimated 151,700 to 575,400 people worldwide from 2009 to 2010, according to the Centers for Disease Control and Prevention.</p>There's no evidence showing that the new virus can spread from person to person. But the researchers did find that 10 percent of swine workers had been infected by the virus, called G4 reassortant EA H1N1. This level of infectivity raises concerns, because it "greatly enhances the opportunity for virus adaptation in humans and raises concerns for the possible generation of pandemic viruses," the researchers wrote.
SEAL training is the ultimate test of both mental and physical strength.
- The fact that U.S. Navy SEALs endure very rigorous training before entering the field is common knowledge, but just what happens at those facilities is less often discussed. In this video, former SEALs Brent Gleeson, David Goggins, and Eric Greitens (as well as authors Jesse Itzler and Jamie Wheal) talk about how the 18-month program is designed to build elite, disciplined operatives with immense mental toughness and resilience.
- Wheal dives into the cutting-edge technology and science that the navy uses to prepare these individuals. Itzler shares his experience meeting and briefly living with Goggins (who was also an Army Ranger) and the things he learned about pushing past perceived limits.
- Goggins dives into why you should leave your comfort zone, introduces the 40 percent rule, and explains why the biggest battle we all face is the one in our own minds. "Usually whatever's in front of you isn't as big as you make it out to be," says the SEAL turned motivational speaker. "We start to make these very small things enormous because we allow our minds to take control and go away from us. We have to regain control of our mind."
Is focusing solely on body mass index the best way for doctor to frame obesity?
- New guidelines published in the Canadian Medical Association Journal argue that obesity should be defined as a condition that involves high body mass index along with a corresponding physical or mental health condition.
- The guidelines note that classifying obesity by body mass index alone may lead to fat shaming or non-optimal treatments.
- The guidelines offer five steps for reframing the way doctors treat obesity.