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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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Space
Mysterious 'Hypatia Stone' Is Like Nothing Else in Our Solar System
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In 1996, Egyptian geologist Aly Barakat discovered a tiny, one-ounce stone in the eastern Sahara. Ever since, scientists have been trying to figure out where exactly the mysterious pebble originated. As Popular Mechanics reports, it probably wasn't anywhere near Earth. A new study in Geochimica et Cosmochimica Acta finds that the micro-compounds in the rock don't match anything we've ever found in our solar system.

Scientists have known for several years that the fragment, known as the Hypatia stone, was extraterrestrial in origin. But this new study finds that it's even weirder than we thought. Led by University of Johannesburg geologists, the research team performed mineral analyses on the microdiamond-studded rock that showed that it is made of matter that predates the existence of our Sun or any of the planets in the solar system. And, its chemical composition doesn't resemble anything we've found on Earth or in comets or meteorites we have studied.

Lead researcher Jan Kramers told Popular Mechanics that the rock was likely created in the early solar nebula, a giant cloud of homogenous interstellar dust from which the Sun and its planets formed. While some of the basic materials in the pebble are found on Earth—carbon, aluminum, iron, silicon—they exist in wildly different ratios than materials we've seen before. Researchers believe the rock's microscopic diamonds were created by the shock of the impact with Earth's atmosphere or crust.

"When Hypatia was first found to be extraterrestrial, it was a sensation, but these latest results are opening up even bigger questions about its origins," as study co-author Marco Andreoli said in a press release.

The study suggests the early solar nebula may not have been as homogenous as we thought. "If Hypatia itself is not presolar, [some of its chemical] features indicate that the solar nebula wasn't the same kind of dust everywhere—which starts tugging at the generally accepted view of the formation of our solar system," Kramer said.

The researchers plan to further probe the rock's origins, hopefully solving some of the puzzles this study has presented.

[h/t Popular Mechanics]

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Ocean Waves Are Powerful Enough to Toss Enormous Boulders Onto Land, Study Finds
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During the winter of 2013-2014, the UK and Ireland were buffeted by a number of unusually powerful storms, causing widespread floods, landslides, and coastal evacuations. But the impact of the storm season stretched far beyond its effect on urban areas, as a new study in Earth-Science Reviews details. As we spotted on Boing Boing, geoscientists from Williams College in Massachusetts found that the storms had an enormous influence on the remote, uninhabited coast of western Ireland—one that shows the sheer power of ocean waves in a whole new light.

The rugged terrain of Ireland’s western coast includes gigantic ocean boulders located just off a coastline protected by high, steep cliffs. These massive rocks can weigh hundreds of tons, but a strong-enough wave can dislodge them, hurling them out of the ocean entirely. In some cases, these boulders are now located more than 950 feet inland. Though previous research has hypothesized that it often takes tsunami-strength waves to move such heavy rocks onto land, this study finds that the severe storms of the 2013-2014 season were more than capable.

Studying boulder deposits in Ireland’s County Mayo and County Clare, the Williams College team recorded two massive boulders—one weighing around 680 tons and one weighing about 520 tons—moving significantly during that winter, shifting more than 11 and 13 feet, respectively. That may not sound like a significant distance at first glance, but for some perspective, consider that a blue whale weighs about 150 tons. The larger of these two boulders weighs more than four blue whales.

Smaller boulders (relatively speaking) traveled much farther. The biggest boulder movement they observed was more than 310 feet—for a boulder that weighed more than 44 tons.

These boulder deposits "represent the inland transfer of extraordinary wave energies," the researchers write. "[Because they] record the highest energy coastal processes, they are key elements in trying to model and forecast interactions between waves and coasts." Those models are becoming more important as climate change increases the frequency and severity of storms.

[h/t Boing Boing]

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