Scientists Discover a New Part of the Human Body

Map of the lymphatic system: traditional (left) and as redrawn by the researchers' discovery. Image courtesy of University of Virginia Health System.

When you woke up this morning, you did so with an entirely new body part—at least in the eyes of science. You can’t see it or touch it, but it will play a crucial role in understanding neurological diseases and immunity.

Researchers at University of Virginia’s School of Medicine recently discovered a long-hidden system of vessels they've coined the “central nervous system lymphatic vessels,” which drain lymphatic fluid from the brain to the surrounding lymph nodes.

The discovery, published in Nature, has shaken up the scientific community. The study was headed by Antoine Louveau, a postdoctoral fellow in the lab of UVA’s Jonathan Kipnis, director of the Center for Brain Immunology and Glia. The team detected the vessels after Louveau developed a method for mounting a mouse’s meninges (membranes covering the brain) on a slide without ruining the delicate tissue. When he saw vessel-like patterns in the distribution of immune cells, he tested for lymphatic vessels—and the results surprised everyone. They were also able to find the vessels in human brain samples. 

This find is the neuroimmunological version of stumbling across a unicorn. Not only had the system gone undiscovered until now, but textbooks argued against its very existence. As a result, neuroimmunologists have struggled to understand the mechanisms of brain drainage and inflammation.

When all other tissues in the body become inflamed, molecules or pathogens are drained into the local lymph cells, where immune cells get activated to continue the fight. “In the brain, we thought this system didn’t exist. When we first saw those vessels, I completely freaked out," Kipnis tells mental_floss. "This discovery is as exciting as it gets.”

The deep location of these newly discovered vessels is likely what has kept them secret for so long. They’re found in the dural sinuses, which drain blood from the internal and external veins of the brain into the internal jugular veins. They’re also near a major blood vessel, which obscured them from view.

These vessels show all the “molecular hallmarks of lymphatic endothelial cells,” the researchers write. They carry fluid and immune cells from the brain in the cerebrospinal fluid, and are connected to the deep cervical lymph nodes—where immune cells enter and exit.

Kipnis cautions that because the human brain is far more complicated than a mouse brain, these new vessels need to be studied more in depth to better understand them. Nevertheless, he's excited about the role this discovery may play in understanding and treating many disorders, including multiple sclerosis (MS), Alzheimer’s, and autism: “The most important things are yet to be discovered.”

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More Studies See Links Between Alzheimer's and Herpes
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Although it was discovered in 1906, Alzheimer’s disease didn’t receive significant research attention until the 1970s. In 1984, scientists identified the plaque-like buildup of amyloid beta proteins in brain tissue that causes nerve damage and can lead to symptoms like memory loss, personality changes, and physical debility.

Now, researchers are learning why amyloid beta tends to collect in brain tissue like barnacles on a ship. It might not be rallying expressly to cause damage, but to protect the brain from another invader: the herpes simplex virus.

As The Atlantic recently noted, a number of studies have strengthened the notion that amyloid beta activity is working in response to herpes, the virus that travels along nerve pathways and typically causes cold sores around the mouth (HSV-1) or genitals (HSV-2). In a study involving mice, those engineered to produce more amyloid beta were more resistant to the herpes virus than those who were not.

But when too much amyloid beta is produced to combat the virus, the proteins can affect the brain’s neurons. And while herpes tends to target specific pathways in the body that result in external sores, it’s possible that the virus might act differently in an older population that is susceptible to more widespread infection. Roughly half of adults under age 50 in the U.S. are infected with HSV-1 and 12 percent with HSV-2, which suggests that a large swath of the population could be vulnerable to Alzheimer's disease. Two other strains of the virus, HHV-6A and HHV-7, have also been found to be more common in the brains of deceased Alzheimer’s patients than in the general population.

More research will be needed to further understand the possible relationship between the two. If more findings support the theory, then it’s possible that antiviral drugs or vaccines targeting herpes might also reduce the chances of amyloid beta buildup.

[h/t Atlantic]

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Heatwaves Can Affect Your Ability to Think Clearly and Make Decisions
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Dehydration and body odor aren't the only things to hate about oppressive heat. According to new research reported by The Guardian, living through a heatwave without relief hampers your ability to think quickly and clearly.

For their study, published recently in PLOS Medicine, researchers at the Harvard T.H. Chan School of Public Health tested the mental performance of 44 students during a heatwave in Boston in 2016. Roughly half the students were living in newer dorm buildings with central AC, with the other half living in older dorms without it.

Over 12 days, researchers had participants take cognition tests on their phones immediately after waking up. The students living without AC took about 13 percent longer to respond to the questions and their answers were about 13 percent less accurate.

The results indicate that even if high temperatures don't pose an immediate threat to someone's health, they can impair them in other ways. “Most of the research on the health effects of heat has been done in vulnerable populations, such as the elderly, creating the perception that the general population is not at risk from heat waves,” Jose Guillermo Cedeño-Laurent, research fellow at Harvard Chan School and lead author of the study, said in a statement. “Knowing what the risks are across different populations is critical considering that in many cities, such as Boston, the number of heat waves is projected to increase due to climate change.”

Summers are gradually becoming hotter and longer in Boston—a trend that can be observed throughout most of the rest of the world thanks to the rising temperatures caused by human activity. In regions with historically cold winters, like New England, many buildings, including Harvard's oldest dorms, are built to retain heat, which can extend the negative effects of a heat wave even as the weather outside starts to cool. If temperatures continue to rise, we'll have to make a greater effort to keep people cool indoors, where American adults spend 90 percent of their time.

Our thinking isn't the only thing that suffers in the stifling heat. A study published last year found that hot weather does indeed make you crankier—which may not be as bad as bombing a test, but it's not exactly not fun for the people around you.

[h/t The Guardian]

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