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Scientists Pinpoint Brain Cells That Signal When To Stop Eating

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Nature employs a lot of checks and balances to keep life running smoothly. For example: When an animal’s stomach is full, its brain tells it to stop eating (although you might not be able to tell from watching your dog at dinnertime). Scientists say they’ve found the exact group of brain cells responsible for that “stop eating!” message—and what happens when those cells are damaged. Their report was published in the journal Science.

Many call obesity an epidemic. But what we often overlook are the myriad factors that can lead to a person becoming and staying overweight or obese. It’s not a matter of simply deciding to eat less; genetics, gut bacteria, hormones, socioeconomic status, chemical exposure, and, now, this little bundle of brain cells, have all been implicated.

The discovery of the brain’s satiety (or fullness) center was a happy accident. A team of researchers were studying the enzymes that boost or weaken synapses, the connections between brain cells. They focused their attention on an enzyme called OGT, which is known to affect how the body uses sugar and insulin.

To find out the relationship between OGT and synapses, the researchers switched off the OGT-encoding genes in a group of adult laboratory mice. Another group of mice went about their genetic business as usual. All the mice were allowed to eat as much as they wanted.

Before the researchers even began their tests, the OGT-deficient mice had doubled in weight. As the study continued, those mice continued to expand to twice their size every three weeks. And it wasn’t muscle they were gaining; it was fat, all over their bodies.

Image Credit: Johns Hopkins Medicine

The scientists began monitoring how often and how much the mice were eating. Both groups ate about 18 meals a day, but the mice in the experimental group lingered over their food and ate more calories at every meal than their control-group counterparts. The researchers then cut the chubby mice off, limiting their diet to reasonable portions. In the absence of extra calories, the mice stopped gaining weight, which suggests that the problem lay in their satiety signaling.

"These mice don't understand that they've had enough food, so they keep eating," co-author Olof Lagerlöf said in a press statement.

The thing is, the hippocampus and cortex—the areas deprived of OGT in the experimental group—aren’t generally associated with eating. So the researchers wondered if changes had occurred elsewhere in the rodents’ brains. The researchers euthanized the mice, removed their brains, and looked at thin slices of brain tissue under a high-powered microscope. They were looking for a region with a notable absence of OGT, and they found it, in a little bundle of nerve cells called the paraventricular nucleus (PVN).

Unlike the hippocampus and cortex, the PVN is known for affecting appetite and eating. But like any part of the brain, the PVN needs healthy synapses in order to do its job, and the researchers found that synapses in the fat rodents’ PVNs were in bad shape. The OGT-deficient mice had three times fewer PVN synapses than the control group.

"That result suggests that, in these cells, OGT helps maintain synapses," co-author Richard Huganir said. "The number of synapses on these cells was so low that they probably aren't receiving enough input to fire. In turn, that suggests that these cells are responsible for sending the message to stop eating."

The researchers confirmed their theory, so they tried boosting the synapses instead of wearing them down. Sure enough, mice with strong PVN synapses decreased their food intake by 25 percent.

"There are still many things about this system that we don't know," Lagerlöf said, "but we think that glucose works with OGT in these cells to control 'portion size' for the mice. We believe we have found a new receiver of information that directly affects brain activity and feeding behavior, and if our findings bear out in other animals, including people, they may advance the search for drugs or other means of controlling appetites."

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Beyond the Label: How to Pick the Right Medicines For Your Cold and Flu Symptoms
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The average household spends an annual total of $338 on various over-the-counter medicines, with consumers making around 26 pharmacy runs each year, according to 2015 data from the Consumer Healthcare Products Association. To save cash and minimize effort (here's why you'd rather be sleeping), the Cleveland Clinic recommends avoiding certain cold and flu products, and selecting products containing specific active ingredients.

Since medicine labels can be confusing (lots of people likely can’t remember—let alone spell—words like cetirizine, benzocaine, or dextromethorphan), the famous hospital created an interactive infographic to help patients select the right product for them. Click on your symptom, and you’ll see ingredients that have been clinically proven to relieve runny or stuffy noses, fevers, aches, and coughs. Since every medicine is different, you’ll also receive safety tips regarding dosage levels, side effects, and the average duration of effectiveness.

Next time you get sick, keep an eye out for these suggested elements while comparing products at the pharmacy. In the meantime, a few pro tips: To avoid annoying side effects, steer clear of multi-symptom products if you think just one ingredient will do it for you. And while you’re at it, avoid nasal sprays with phenylephrine and cough syrups with guaifenesin, as experts say they may not actually work. Cold and flu season is always annoying—but it shouldn’t be expensive to boot.

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Why You Might Not Want to Order Tea or Coffee On Your Next Flight
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A cup of tea or coffee at 40,000 feet may sound like a great way to give yourself an extra energy boost during a tiring trip, but it might be healthier to nap away your fatigue—or at least wait until hitting ground to indulge in a caffeine fix. Because, in addition to being tepid and watery, plane brew could be teeming with germs and other harmful life forms, according to Business Insider.

Multiple studies and investigations have taken a closer look at airplane tap water, and the results aren’t pretty—or appetizing. In 2002, The Wall Street Journal conducted a study that looked at water samples taken from 14 different flights from 10 different airlines. Reporters discovered “a long list of microscopic life you don’t want to drink, from Salmonella and Staphylococcus to tiny insect eggs," they wrote.

And they added, "Worse, contamination was the rule, not the exception: Almost all of the bacteria levels were tens, sometimes hundreds, of times above U.S. government limits."

A 2004 study by the U.S. Environmental Protection Agency (EPA) found that water supplies on 15 percent of 327 national and international commercial aircrafts were contaminated to varying degrees [PDF]. This all led up to the 2011 Aircraft Drinking Water Rule, an EPA initiative to make airlines clean up. But in 2013, an NBC investigation found that at least one out of every 10 commercial U.S. airplanes still had issues with water contamination.

Find out how airplane water gets so gross, and why turning water into coffee or tea isn’t enough to kill residual germs by watching Business Insider’s video below.

[h/t Business Insider]

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