SCOTT DETROW, HOST:
It is time now for our science news roundup from Short Wave, NPR's science podcast. And I am joined by the show's two hosts, Regina Barber and Emily Kwong. Hello.
EMILY KWONG, BYLINE: Hi, Scott.
REGINA BARBER, BYLINE: Hey.
DETROW: Always happy to be in a Short Wave roundup.
KWONG: We love having you.
BARBER: Yes, definitely.
DETROW: As always, you have brought us three science stories that caught your attention this week. What are they?
KWONG: Why our craving for dessert begins in our brains.
DETROW: OK.
BARBER: How elephant seals are helping scientists monitor ocean health.
KWONG: And lastly, finding water in the desert fog.
DETROW: All interesting. Obviously we need to start with dessert.
KWONG: I agree.
BARBER: Totally.
KWONG: I'm that kind of person. What is your favorite kind of dessert, Scott?
DETROW: Key lime pie.
KWONG: Classy.
BARBER: Boo.
DETROW: Wait, what?
BARBER: I don't like it.
KWONG: All right, we're not going to debate that right here, right now. All desserts are considered. But I posed this exact same question to scientist Henning Fenselau - he said gummy bears.
DETROW: OK.
BARBER: Correct.
KWONG: Which makes (laughter) - which makes sense...
DETROW: I'm fine with both.
KWONG: Which makes sense, you two, because Henning is from Bonn, Germany, the town where Haribo gummy candies began.
DETROW: Yeah.
HENNING FENSELAU: This is from my hometown, so I'm still a big fan of it, maybe driven by my childhood, I don't know (laughter).
KWONG: They say research is mesearch (ph). OK. So now, Henning is research group leader at the Max Planck Institute for Metabolism Research, and in a new study in the journal Science, his team investigates how our bodies can crave sugar even when our stomachs are full.
DETROW: I, along with so many others, have had that happen so many times.
KWONG: Yeah.
DETROW: Like, why? What is going on? Why are our bodies telling us to do this?
BARBER: Scott, it's our brains. So one of the ways our body signals that we're full involves these satiety neurons, and they're located in this part of our brain called the hypothalamus. But sugar seems to hijack that system in an interesting way.
KWONG: Yeah, to say the least. So to study how this works, Henning and his colleagues turned to mice, which have similar brains to us, and researchers fed mice to the point of fullness and then gave them sugar. And they noticed that those same neurons signaling satiety were also triggering the release of naturally occurring opiates called beta-endorphins, and this flood of opiates in the mouse brain triggered a feeling of reward.
DETROW: So let me make sure I'm following that, OK? So their brains are signaling they're full...
KWONG: Yeah.
DETROW: ...But they're still, at the same time, tripping more brain wires that are saying, eat more sugar.
BARBER: Yes.
KWONG: Yes. So when the researchers blocked this pathway, the mice seemed less interested in sugar.
DETROW: Interesting.
BARBER: Yeah.
KWONG: And then, Henning and his colleagues found the same pathways in humans by looking at donated brain tissue and scanning brains of volunteers who sat in an fMRI machine and were fed a sugar solution through a tube.
DETROW: So my first question is how do I stop being a radio host and do this instead, take part in these researches? But beyond that...
BARBER: Impossible to answer.
DETROW: ...My other question - are there any hypotheses here for why our brains are set up this way?
KWONG: Well, it is consistent with what we know about sugar for survival. Sugar, it signals to our brain, oh, this food is full of energy. It's easy to metabolize. Of course, excess sugar is bad for us, so Henning now wants to know how much this pathway contributes to overeating, does it lead to the development of obesity and can this discovery be built into weight-loss drugs?
DETROW: OK. Let's talk seals next. I hear some of them are doing science now?
BARBER: Yeah, they're trying to take my job.
DETROW: It's OK, 'cause we're all going to the sugar-eating jobs.
BARBER: That's right (laughter).
KWONG: Yeah (laughter).
BARBER: Researchers figured out a way to measure the health of parts of the ocean by tracking and weighing elephant seals.
DETROW: Help me make this connection a little more. Is this - what does seal weight have to do with ocean health? Like, is this if the seals are eating enough food, we're in good shape?
BARBER: It's something like that, yeah.
DETROW: OK.
BARBER: Because elephant seals, especially the mothers, eat a lot of fish. So how much these moms weigh can tell scientists how many fish there are that year, which has ripple effects for everything that eats those fish and everything that gets eaten by the fish.
DETROW: How do you weigh a seal?
KWONG: According to lead researcher Roxanne Beltran, a huge pulley system, basically. They wait for pregnant females to return from their monthslong foraging trip to beaches on the California coast, where they give birth and bond with their pups. Then, using binoculars and cameras, the scientists identify previously tagged seals they want to weigh, and then they weigh them.
ROXANNE BELTRAN: It sounds so simple, but weighing a 500-kilogram elephant seal is a lot of work. You have to sedate the seal and then take five people to roll the seal into a sling to be suspended in midair from a tripod hanging from a scale so we can read that mass.
KWONG: So rude.
DETROW: (Laughter).
KWONG: Can you imagine coming back for dinner - dessert, perhaps - and then someone's like...
BARBER: Yep.
KWONG: ...Hop on the scale?
BARBER: Every day.
KWONG: But anyway, using this method, scientists have weighed seals 600 times in the last two decades.
DETROW: Hear me out. What if instead of weighing seals, they just did, like, a fish census?
BARBER: Yeah, they can't (laughter). So this is part of the ocean that scientists have, like, a really hard time getting information from. It's called the Twilight Zone.
DETROW: Oh.
BARBER: One of my favorite shows. It's hundreds to thousands of feet below the surface, and Roxanne says not knowing the true number of fish in these dark depths is a problem.
BELTRAN: Our counts of fishes range by about 10 orders of magnitude, and we don't know how those numbers fluctuate year after year, and that's what the seals were able to tell us.
KWONG: Roxanne's team published all of these details in the journal Science. So in addition to being a barometer for fish populations, seal health can also teach us about the health of the ocean in general, which is important for climate regulation, food security and local economies.
DETROW: Dessert - check. Seals - check.
BARBER: Yes.
DETROW: Next - collecting water from fog, which does not strike me as a new thing, right?
KWONG: No.
DETROW: OK.
KWONG: It's not new. So fog collection is, like, an old technique, and scientists have been studying it for at least 40 years. But all of that data came from small villages. And now, a new study in the journal Frontiers in Environmental Science shows that fog could be a viable source of drinking water in a big city, too.
BARBER: So this study - it's very cool. It focuses on Alto Hospicio, a city of over 140,000 people in the Atacama Desert in Chile. This is one of the driest deserts in the world, so it's a prime spot to test out fog collection.
DETROW: How does this actually work? Like, is this similar to, like, collecting condensation?
BARBER: A little bit.
DETROW: OK.
BARBER: Fog is created when large masses of warm air travel from the ocean over the land, and when that warm, wet air hits cold air in the desert - boom - you got fog. Then people can use meshes, nets or even leaves to condense the fog, collect it in jugs or buckets, which are now full of fresh water.
DETROW: How much of an impact could this make on a city's water supply?
KWONG: Well, after collecting data at various, like, fog collection sites for a year, the researchers used a computer model to map how much water could be collected from fog over this whole region. And they found that fog could supply hundreds of thousands of liters of drinking water per week, enough to supplement the water demands of under-resourced parts of the city.
BARBER: The lead author of the study, Virginia Carter, of Universidad Mayor in Chile, considers desert fog a sustainable water source. She pointed out that Alto Hospicio struggles in terms of infrastructure, budget and green spaces. So ultimately, Virginia wants to take this data to city officials so they can make fog collection a reality across the city for drinking water, green spaces and food gardens.
DETROW: You know what we just did there?
BARBER: What?
DETROW: We went from dessert to desert.
KWONG: (Laughter).
DETROW: Waka waka (ph).
BARBER: He spells...
KWONG: (Laughter) I can't...
BARBER: He spells, he hosts - he's Scott Detrow.
DETROW: (Laughter) That's Emily Kwong and Regina Barber from NPR's science podcast Short Wave, which you can follow for new discoveries, everyday mysteries and the science behind the headlines. Thanks to both of you.
BARBER: Thanks, Scott.
KWONG: Thank you.
BARBER: Thanks so much.
(SOUNDBITE OF MUSIC)
BARBER: You ever thought about hosting a science podcast?
DETROW: I would love to.
BARBER: You have the brain. He has the experiment - like, I-can-design-an-experiment brain. Is it just the glasses?
DETROW: It's the glasses, yeah.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
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