Katherine Ralston
Katherine Ralston

Caught on Camera: An Amoeba Eating Human Cells Alive

Katherine Ralston
Katherine Ralston

Are you squeamish? Does the thought of germs and/or microscopic organisms give you the creeps? You might want to turn back now.

The Entamoeba histolytica amoeba infects 50 million people all over the world, and every year, it kills roughly 100,000 of them. Until recently, researchers weren’t sure how this microbe worked. Now, thanks to postdoctoral researcher Katherine Ralston and her team at the University of Virginia in Charlottesville, we have some unsettling insight into how the amoeba attacks its victims: It eats their cells, bit by bit, until the cells are dead.

This particular infection occurs most commonly in developing nations, after victims ingest contaminated food or water. In some parts of Bangladesh, for example, Ralston says 30 percent of children contract the amoeba at least once before their first birthday. While some victims show no symptoms at all, in others, it can cause severe dysentery and even spread to other organs—like the liver—which can be deadly. So, researchers wanted to know: What exactly happens after these microbes are ingested? How do they go on to cause disease in other parts of the body?

To get an up-close look at the action, researchers, led by Virginia’s William Petri, Jr., mixed the amoeba with human cells and observed its behavior under a microscope. Like a microscopic Pacman, almost immediately upon contact, the parasite started taking bites of and ingesting the human cells. Within about 10 minutes, the cells met their untimely death, and the amoeba moved on to its next victim. Researchers caught the whole thing on video.

Why is this process so shocking? Aside from the cringeworthy fact that a parasite is slowly eating human cells alive, researchers were also surprised because many other microbes take a somewhat less violent approach to eliminating cells, emitting something toxic to poison them. “It was thought they would kill cells like a lot of other microbes kill cells,” Ralston told mental_floss. “Instead you see them gnawing on the cell. This really physical cell death is not typical.”

Even more puzzling: The parasite isn’t using the human cells as a primary source of nourishment. “Once these cells had been killed, they stopped eating and moved on to a new cell,” Ralston says. “If it was about nutrition, they would ingest the rest of the cell as a readily available meal.” So why go through the trouble of ingesting the cells, if not for nourishment? Ralston and her team think this is a way for the parasite to invade the intestine, or perhaps a defense mechanism against immune cells sent to rescue the victim from the parasite.

But researchers needed to be sure that this gnawing process is what actually kills the cells. Could cells survive if they’d only been bitten once or twice? If they knew the cause of cell death, they could move forward developing treatments to prevent it. So they altered the microbe, inhibiting its ability to attach to the cells, and saw that indeed, the cells can endure the carnage, up to a point. “We actually found that with some inhibitors—even if we didn’t completely inhibit nibbling, just reduced it—that it allowed the human cells to live,” Ralston says. “It seems there’s a threshold. If we could block this process, that would be a potential new therapy.”

The findings appear in the April edition of the journal Nature and could lead to new treatments for Entamoeba histolytica, which is currently treatable with one class of drugs. “This changes the paradigm for this infection, “ Ralston says.

Live confocal microscopy time lapse demonstrating that bites of human cell material are internalized by the amoebae. Ingestion of bites occurs while human Jurkat cells are viable and ceases once they are dead. Human cells were pre-labeled with DiI (red; cell membrane), Flou4 (green; intracellular Ca2+); and SYTOX blue (blue; nucleic acid in permeable cells) was present in the media during imaging. Images were collected every 30 seconds and are played back at 1 frame per second


Live confocal microscopy time lapse demonstrating that human cell intracellular calcium elevation follows the ingestion of bites. Human Jurkat cells were pre-labeled with DiD (pink; cell membrane), and Flou4 (green; intracellular Ca2+). Images were collected every 20 seconds and are played back at 1 frame per second.

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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Scientists Find a Possible Link Between Beef Jerky and Mania
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Scientist have discovered a surprising new factor that may contribute to mania: meat sticks. As NBC News reports, processed meats containing nitrates, like jerky and some cold cuts, may provoke symptoms of mental illness.

For a new study, published in the journal Molecular Psychiatry, scientists surveyed roughly 1100 people with psychiatric disorders who were admitted into the Sheppard Pratt Health System in Baltimore between 2007 and 2017. They had initially set out to find whether there was any connection between certain infectious diseases and mania, a common symptom of bipolar disorder that can include racing thoughts, intense euphoria, and irritability.

While questioning participants about their diet, the researchers discovered that a significant number of them had eaten cured meats before their manic episodes. Patients who had recently consumed products like salami, jerky, and dried meat sticks were more likely to be hospitalized for mania than subjects in the control group.

The link can be narrowed down to nitrates, which are preservatives added to many types of cured meats. In a later part of the study, rats that were fed nitrate-free jerky acted less hyperactive than those who were given meat with nitrates.

Numerous studies have been published on the risks of consuming foods pumped full of nitrates: The ingredient can lead to the formation of carcinogens, and it can react in the gut in a way that promotes inflammation. It's possible that inflammation from nitrates can trigger mania in people who are already susceptible to it, but scientists aren't sure how this process might work. More research still needs to be done on the relationship between gut health and mental health before people with psychiatric disorders are told to avoid beef jerky altogether.

[h/t NBC News]

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