Learn about why cavities are so cold-sensitive; an ant that shrinks its brain; and why swimming makes you extra hungry. Here's why dental cavities are so sensitive to cold by Cameron Duke Bernal, L., Sotelo-Hitschfeld, P., König, C., Sinica, V., Wyatt, A., Winter, Z., Hein, A., Touska, F., Reinhardt, S., Tragl, A., Kusuda, R., Wartenberg, P., Sclaroff, A., Pfeifer, J. D., Ectors, F., Dahl, A., Freichel, M., Vlachova, V., Brauchi, S., & Roza, C. (2021). Odontoblast TRPC5 channels signal cold pain in teeth. Science Advances, 7(13), eabf5567. https://doi.org/10.1126/sciadv.abf5567 How teeth sense the cold. (2021). EurekAlert! https://www.eurekalert.org/pub_releases/2021-03/hhmi-hts032421.php There’s an ant that shrinks its brain to try to become the queen by Cameron Duke Annie, R. (2021, April 13). These Ants Shrink Their Brains for a Chance to Become Queen. The New York Times. https://www.nytimes.com/2021/04/13/science/ants-brains-queen.html Penick, C. A., Ghaninia, M., Haight, K. L., Opachaloemphan, C., Yan, H., Reinberg, D., & Liebig, J. (2021). Reversible plasticity in brain size, behaviour and physiology characterizes caste transitions in a socially flexible ant ( Harpegnathos saltator ). Proceedings of the Royal Society B: Biological Sciences, 288(1948). https://doi.org/10.1098/rspb.2021.0141 Urbani, C. B., Boyan, G. S., Blarer, A., Billen, J., & Musthak Ali, T. M. (1994). A novel mechanism for jumping in the indian antHarpegnathos saltator (Jerdon) (Formicidae, Ponerinae). Experientia, 50(S1), 63–71. https://doi.org/10.1007/bf01992052 Swimming Really Does Make You Hungrier Than Other Forms of Exercise by Ashley Hamer Harvard Health Publishing. (2021). Calories burned in 30 minutes for people of three different weights - Harvard Health. Harvard Health; Harvard Health. https://www.health.harvard.edu/diet-and-weight-loss/calories-burned-in-30-minutes-of-leisure-and-routine-activities Exercise In Cold Water May Increase Appetite, UF Study Finds. (2021). ScienceDaily. https://www.sciencedaily.com/releases/2005/05/050504225732.htm Sportscience Compeat: Swimmers: Body fat mystery! (1997). Sportsci.org. http://www.sportsci.org/news/compeat/fat.html Harmon, K. (2011, May 10). Sink or Swim: Muscle versus Fat. Scientific American. https://www.scientificamerican.com/article/muscle-versus-fat/ Follow Curiosity Daily on your favorite podcast app to learn something new every day withCody Gough andAshley Hamer — for free!
Learn about why cavities are so cold-sensitive; an ant that shrinks its brain; and why swimming makes you extra hungry.
Here's why dental cavities are so sensitive to cold by Cameron Duke
There’s an ant that shrinks its brain to try to become the queen by Cameron Duke
Swimming Really Does Make You Hungrier Than Other Forms of Exercise by Ashley Hamer
Follow Curiosity Daily on your favorite podcast app to learn something new every day with Cody Gough and Ashley Hamer — for free!
Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/why-cavities-are-so-sensitive-to-the-cold
CODY: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from curiosity-dot-com. I’m Cody Gough.
ASHLEY: And I’m Ashley Hamer. Today, you’ll learn about why dental cavities are so sensitive to cold; an ant that shrinks its brain to try to become a queen; and whether swimming really does make you hungrier than other forms of exercise.
CODY: Let’s satisfy some curiosity.
Dental cavities are agonizing. If you’ve had one, you know what I’m talking about. If you’re one of the fortunate few with perfect teeth, then you’ll just have to take my word for it. The worst part of a cavity is the pain you feel when you drink something cold. Now scientists know why cavities are so cold sensitive.
Dental cavities happen when bacteria eat away at the enamel coating of your teeth. This creates little pits in the enamel that can feel like exposed nerve endings when you eat or drink. Key words: feel like. You might be surprised to learn that up until now, scientists really didn’t have a good explanation for this type of sensitivity. Teeth have nerves, but cavities are rarely deep enough to expose them.
New research from the Howard Hughes Medical Institute provides a solid explanation for this annoying phenomenon. Researchers found that specialized cells called odontoblasts contain a cold-sensitive protein called TRPC5. Odontoblasts can be found in dentin — that’s the tooth layer that’s right below the enamel. So when a cavity exposes even the tiniest bit of dentin, those cold-sensing odontoblast proteins change shape slightly. This sends a signal to nerves much deeper into the tooth, which in turn gives your brain that unpleasant jolt of pain.
This took a long time to discover because studying tooth structure is incredibly hard. Enamel is the hardest material on the body, and dentin’s no slouch either. Attempts to cut these materials often ends up with the enamel shattering and the blood vessels and nerves being reduced to a useless pulp.
But this research team discovered all of this without breaking a single tooth open. Instead, they bred special mice that couldn’t produce that cold-sensitive odontoblast protein. They recorded brain activity in those mice and in a group of normal mice as they exposed their little teeth to the cold. They found that the mice without the protein didn’t react to the cold at all.
Here’s the neatest thing about the finding: it actually adds some scientific credence to an old home remedy for toothaches. See, clove oil has been used as a dental pain remedy for centuries. It contains a chemical that works by blocking that cold-sensitive protein, which prevents it from sending that cold signal to a nerve. Pretty cool, I’d say.
When it comes to brains, bigger is better… isn’t it? At least we have a tendency to think so. But the Indian jumping ant might be inclined to disagree. Scientists just discovered that these ants can actually shrink their own brains and then regrow them.
Now why would they do that? It comes down to the structure of their societies. See, Indian jumping ants are a special case among ants. For one, they’re huge. On average, they can be an inch long — that’s two and a half centimeters — and of course, they jump. But that’s not all that makes them unique in the ant world. Most insects that live in colonies have strict caste systems. Queens and workers are born into their jobs, and if you’re born as a worker? Well, it’s a life of tunnel digging and carrying food along pheromone trails for you. If you don’t like that, then tough luck.
Indian jumping ant societies are a lot like these other insect societies, but with one key difference: any worker ant can become queen. When a spot opens for the top job, the workers can apply. (All worker ants, by the way, are female. In the ant world, males are basically just there for reproduction.)
The queen-application process is rough, and these ants have to put their minds into it. I mean that very literally. They have to shrink their brains, because well, brains are expensive to maintain. This frees up the energy to grow enormous ovaries that are five times their original size. Physical changes like this are what scientists refer to as phenotypic plasticity, or the ability to change physical form in response to environmental factors.
When they have fully morphed, the battle royale begins. That’s right, the ants with the shrunken brains and swollen ovaries form a temporary social caste called the “gamergates,” where each individual tries to outlast the others in a sort of insect wrestlemania (although I’m envisioning more of a Royal Rumble, if you want to get technical). This conflict can last as long as 40 days with as many as 10 ants emerging victorious. The winners get to spend the rest of their lives making babies.
The ants that don’t win? They undergo another remarkable transformation. Their ovaries shrink, their brains regrow, and they just return to their jobs.
So, to summarize: workers who want to be queen have to shrink their brains, grow their ovaries, and submit to a 40-day cagematch, all with the possibility that they’ll just go back to being workers again. Yikes. And you thought college applications were tough!
We've all heard you're not supposed to swim right after you eat (which is a myth, by the way). But have you ever wondered why you're hungrier after swimming than after running or biking? It turns out there's a scientific reason — and it could benefit swimmers in the long run.
Though it may feel like swimming burns more calories than other exercises, which would explain the increase in appetite, that's not the case. Swimming burns about the same number of calories as running and biking do, depending on the pace. But a 2005 study conducted by the University of Florida provided an important clue as to why you're ready to eat a horse when you get out of the pool: people tend to eat more calories after exercising in cold water than in warm water. In the study, students who exercised in cold water ate 44 percent more calories. That means that it might come down to temperature. Swimming in a pool makes you colder than exercising in the open air, and that may be to blame for your increase in appetite. This could be because feeling cold constricts your blood vessels, which may prevent the release of hormones that would normally make you less hungry — akin to why an animal eats more when preparing for winter hibernation.
And it’s not just casual swimmers who get hungry. In fact, studies have shown that collegiate swimmers have higher body fat levels than their runner counterparts. It seems like that body fat gives swimmers an advantage. More body fat makes for smoother curves, which provide less resistance in the water. Fat is also less dense than muscle, which gives it more buoyancy and helps keep swimmers' bodies afloat.
But if weight loss is your goal? Don’t be scared to swim. Aquatic aerobics are particularly effective for those who are overweight and accustomed to sedentary lifestyles since they're easier on the joints than running. You could also take a brisk walk after you swim to raise your body temperature before grabbing a post-workout snack. In any case, it's a good idea to have healthy foods with low calorie counts and lots of protein on hand. Just please, don't eat a horse.
Let’s recap what we learned today to wrap up. Starting with
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CODY: Today’s writers were Cameron Duke and Ashley Hamer, who’s also our managing editor.
ASHLEY: Our producer and audio editor is Cody Gough.
CODY: Join us again tomorrow and we’ll help you GROW your brain, not shrink it… well okay, I don’t know that we’ll actually alter the physical size of your brain. But still! You can at least join us again tomorrow to learn something new in just a few minutes.
ASHLEY: And until then, stay curious!