JUANA SUMMERS, HOST:
It's time now for our science news roundup from Short Wave, NPR's science podcast. I'm joined here in studio by the show's two hosts, Regina Barber and Emily Kwong. Hi, y'all.
EMILY KWONG, BYLINE: Hi, Juana.
REGINA BARBER, BYLINE: Hey.
SUMMERS: So I know that you've brought us three science stories that caught your attention this week. Tell us what they are.
BARBER: The mutation that makes orange cats orange.
KWONG: And a bike sensor that can help map safer routes.
BARBER: And the connection between gum disease and heart problems.
SUMMERS: Well, I mean, obviously we've got to start with these orange cats.
KWONG: Yeah, the greatest cats of all time. That is a fact, according to my orange tabby, Zuko.
(SOUNDBITE OF CAT MEOWING)
BARBER: My blonde orange boy Benny (ph) also agrees - maybe not the other three cats. But our boss also has two orange cats, Tang (ph) and Dorito (ph). Both of them are males, too.
SUMMERS: Guys, I have to tell you something. I also have an orange cat.
REGINA BARBER AND EMILY KWONG, BYLINE: What?
SUMMERS: And guess what? Also a boy.
BARBER: (Laughter).
KWONG: OK, this is perfect because approximately 80% of orange cats are males, and it's something researchers and cat enthusiasts...
BARBER: Yes.
KWONG: ...Have long noticed.
BARBER: (Laughter).
KWONG: Scientists suspected the reason may be that orange color is a sex-linked trait, meaning the mutation responsible for that ginger hue is found on their sex chromosomes - specifically their X chromosome.
BARBER: Male cats, just like male humans, have an X and Y chromosome, so any male cat with this mutation ends up orange. Female cats need the mutation on both of their X chromosomes to be fully orange, which is statistically less likely. So nearly all calico and tortoiseshell cats are female because this mutation is found on only one of their X chromosomes.
SUMMERS: Interesting. So were they right? Was the mutation on the X chromosome?
KWONG: Yes. They found the mutation. They found its location. It's a single deletion on the X chromosome which causes a nearby gene to be expressed in pigment cells, so cat hair color. This mutation was independently located by two teams of scientists, one led by Hiro Sasaki in Japan and another by Chris Kaelin at Stanford University. Both papers were published in the journal Current Biology this week.
BARBER: So no orange cats were harmed in the pursuit of this genetic mystery.
SUMMERS: Well, that's good.
BARBER: In fact, study author Greg Barsh says that the Stanford team partnered with cat lovers and community scientists to gather DNA samples from dozens of different orange cats.
GREG BARSH: It's an example, I think, of how scientists and the public can work together to not only uncover cool things, but also learn important aspects about biology.
SUMMERS: Interesting. But what about other orange animals, like tigers or orangutans? Are their orange colors linked to their sex chromosomes, too?
BARBER: So actually, no. Their orange color arises from regular chromosomes known as autosomes.
SUMMERS: Proving what we always knew - orange cats really are that special.
KWONG: They're so special. We all know this. And in case you were wondering, all orange cats do share the same mutation. Meaning, Juana, there was a first orange cat.
SUMMERS: Love that. All right, let's move on to the next one and talk about sensors on bikes. I know standard bikes do not have them, but scientists are making these to help those of us that bike not get hit by cars?
BARBER: Yes, Juana. I just bought a bike. I just started biking. I don't want to get hit by a car. So I was very interested in the study where, like, computer scientists created a system called ProxiCycle. It's a sensor to monitor how close cars get to cyclists. The scientists deployed the sensor on 15 bikes over the span of two months in Seattle, Washington.
KWONG: So this bike sensor costs less than $25 to make. It attaches to the left handlebar. And in this study, these 15 cyclists took 240 rides with the sensor and recorded over 2,000 close passes, though thankfully no collisions. And the researchers presented these findings at the Conference on Human Factors in Computing Systems in Japan.
SUMMERS: OK, so other than terrifying these bike riders - and to be clear, this sounds absolutely terrifying - what did these cars zooming too close to the riders tell researchers?
KWONG: Interestingly enough, Seattle has collected bike collision data for the last 20 years, and this study compared five years of that data to the research team's two months of close passes, and the datasets matched pretty well. This tells us that close passes - so when a car comes close to a bike - that might be a good indicator of your chances of an actual collision in that section of the road.
BARBER: And that might seem like an obvious connection to make, but the lead researcher, Joe Breda at the University of Washington, has surveyed cyclists and found that people who were, like, new to city biking weren't all that good at, like, gauging how safe routes were. And that's where this sensor could help. Like, he just wants to encourage more people to bike.
JOE BREDA: Can we lower the barrier of entry to cycling by creating a map of where is it safe or unsafe to bike before any accidents actually happen?
SUMMERS: OK, right - that map. You said the sensor might be helpful in mapping safer bike routes, which would be super helpful. But how would it work?
KWONG: Joe says the next step is to deploy these sensors in more cities on more bikes. He also wants this to be accessible to as many people as possible, perhaps by making the software and design eventually open source.
BARBER: And, you know, Juana, we've gotten so used to, like, maps when we're driving, like, people's devices telling companies like Google where traffic is, allowing them to reroute themselves. Imagine something like that for cyclists, where all of this, like, crowdsource data from the sensors can feed into a map that helps, like, find safer bike routes.
SUMMERS: I mean, that does sound pretty incredible.
BARBER: Agreed.
KWONG: The power of science.
SUMMERS: Indeed. All right, last story of the day. There is a connection between gum disease and heart health?
KWONG: Yes. So people with gum disease could have a higher risk of heart failure or stroke, which we've known, but a recent study in the journal Circulation offers even more insight on the gum disease-heart connection and specifically the link between gum disease and atrial fibrillation.
SUMMERS: I watch too many medical shows, so I know this one. That's AFib, right? Like an irregular...
KWONG: Yes.
SUMMERS: ...Rapid heart rhythm?
BARBER: Right. AFib is common, affecting about 10 million U.S. adults. And now AFib isn't necessarily life-threatening, but it can be dangerous, especially for older people. And gum disease is also really common. It affects nearly half of U.S. adults.
SUMMERS: I did not know that. So tell us, how are they connected?
KWONG: Well, this topic was a special interest to one of the study authors, Shunsuke Miyauchi. He's a cardiologist at Hiroshima University in Japan. Both his parents happen to be dentists. So even though Shunsuke works with hearts, he said he's always paid attention to people's oral care.
BARBER: To study the connection, his team infected mice with a bacteria associated with gum disease and found that these mice developed AFib more easily than those without the bacteria. They also saw that mouth bacteria migrated to the heart, like, in mice and in humans.
KWONG: Though David Wu at the Harvard School of Dental Medicine, who wasn't involved with the study, says the way the mice were infected with the bacteria could have made it easier to spread through the bloodstream.
BARBER: Still, like, once the bacteria reaches the heart, the study authors think it may lead to tissue scarring or inflammation, which may contribute to all sorts of other problems like AFib.
SUMMERS: That's really interesting. So I wonder, does this just mean we should all be taking extra special care of our teeth - brushing more, brushing better?
KWONG: Yes.
BARBER: Yes.
(LAUGHTER)
BARBER: Elizabeth Jackson is a cardiologist at University of Alabama at Birmingham, and she was not involved in the study, but she said it highlights the importance of, like, good dental care and, like, healthy living overall, like exercise, healthy food.
ELIZABETH JACKSON: We know that all the things that help reduce inflammation are good for the heart, and they clearly are good for other parts of us.
KWONG: Everyone we spoke to hopes this study encourages greater collaboration between dentistry and medicine to keep people's gums and hearts healthy.
SUMMERS: 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, both of you.
BARBER: Thank you.
KWONG: Thank you, Juana.
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