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  • [♪ INTRO]

  • Very few people actually enjoy getting poked for a blood test.

  • In fact, it can be a reason some people avoid their physicians altogether.

  • And that is why scientists are thinking outside the needle

  • to create the next generation of diagnostic tests.

  • And it turns out, various secretions can tell us more about our bodies

  • than you might think, including sweat and tearsand also earwax.

  • But let us start with spit.

  • When you think of analyzing bodily fluids,

  • blood might be the first one you think about,

  • but spit gives us about the same information and without needles!

  • In fact, saliva has similar components to blood,

  • because it is partly filtered blood plasma.

  • As that fluid rushes around your body,

  • some of it is diverted from the blood into the salivary gland.

  • Then, the plasma mixes with water in the salivary glands,

  • which then gets into your mouth as saliva.

  • So, like blood, spit has antibodies and enzymes,

  • both of which are hugely valuable in making diagnoses.

  • Antibodies are made by the immune system when it detects viruses,

  • or in autoimmune conditions.

  • And enzymes are involved in basically every process in your body.

  • How much saliva someone produces, as well as the acidity of their spit,

  • can also be helpful for making diagnoses.

  • From a logistics standpoint, spit is pretty easy to collect compared to blood, as well,

  • and it's a cheap way to test larger populations without

  • any risk of spreading bloodborne pathogens.

  • Now, because spit is about 99.5% water,

  • scientists were originally concerned that it was too diluted to be useful.

  • But with advances in technology, tests are more sensitive and are able to

  • pick up on specific molecules at lower concentrations.

  • And that's come in handy.

  • Like, saliva testing has been super helpful

  • during the COVID-19 pandemic in some communities.

  • So, scientists can potentially use saliva tests to test larger populations

  • for the presence of the virus or antibodies quickly and cheaply.

  • And that is only the beginning.

  • Similarly to spit, breath is also something you produce all the time.

  • When you exhale, you release carbon dioxide,

  • but your body also releases volatile organic compounds or VOCs,

  • a huge category of compounds that are able to stay suspended in the air.

  • These volatile compounds are usually generated

  • as byproducts of normal bodily processes.

  • But the VOCs in our breath also change as our health does.

  • For instance, our bodies make nitric oxide to combat inflammation.

  • So, one way to diagnose patients with chronic inflammation in the airways,

  • like from asthma, is to measure how much nitric oxide they're breathing out.

  • Scientists can also trace VOCs to other respiratory conditions

  • like cystic fibrosis and smoking-related conditions.

  • Collecting breath is easy enough.

  • We have special devices for it that are similar to

  • the breathalyzers used to measure blood-alcohol content.

  • Then, scientists can analyze that breath

  • with gas chromatography or mass spectrometry,

  • two techniques that separate out different kinds of molecules.

  • Now, these techniques are used all the time in research,

  • so they're not uncommon.

  • But making, like, anelectrical nosefor medicine is still easier said than done.

  • It's taken almost 40 years, because collecting samples

  • and standardizing the methods has been challenging.

  • But now, with recently improved sensors,

  • scientists have been able to smell out Parkinson's disease.

  • Right now, there's no definitive diagnostic test for this condition.

  • But in a 2018 study, scientists collected the breath

  • of patients with Parkinson's symptoms and observed a spike in benzaldehyde,

  • and acetophenone was observed in a slightly higher amount.

  • It's not clear what's special about these two compounds.

  • They're just a part of the spectrum of VOCs normally in our breath.

  • But if other researchers also notice this pattern,

  • these compounds could be a marker to help diagnose Parkinson's disease.

  • There's still a long way to go before electrical noses hit the market,

  • but these results are a step in the right direction.

  • Lots of breathing is sometimes accompanied by lots of sweating,

  • which is our next bodily fluid.

  • Although we couple sweating with working out or it being hot outside,

  • we actually sweat all the time.

  • So someday, analyzing your sweat could provide doctors with real-time,

  • continuous health monitoring.

  • But for now, most of the studies have focused specifically on exercise.

  • Apart from a bunch of water, you can find electrolytes, metabolites,

  • and other small molecules like glucose in your sweat.

  • These molecules are circulating in your body all the time,

  • like, electrolytes move nutrients around your cells and also maintain your body's pH.

  • And because they're water-soluble, we lose some of them in our sweat.

  • Meanwhile, other small molecules reach the sweat

  • mainly by diffusion through the sweat glands.

  • And to keep track of them, some scientists are trying to use

  • a battery-free, wireless sensor.

  • A sensor like this could tell you all kinds of things about your body.

  • Like, the glucose in sweat can be correlated to how much glucose is in your blood.

  • And scientists have taken advantage of that

  • to determine if glucose is present in sweat during exercise.

  • Meanwhile, the levels of electrolytes and pH of sweat can

  • provide information on how hydrated someone is while exercising,

  • and let them know if they need a water break.

  • Scientists have also tracked lactate.

  • Lactate is generated when you do demanding exercises, like sprinting,

  • in cases where cells aren't all getting enough oxygen,

  • so some of them start functioning without it.

  • To measure when this switch happens,

  • scientists measure the amount of lactate produced and diffused into the sweat,

  • which could be used as an indicator of physical stress.

  • All of these physiological aspects in conjunction

  • give a well-rounded view of someone's body while exercising.

  • Another bodily fluid that doesn't involve needles is tears.

  • Like sweat, we produce tears all the time, but they mostly get drained into the nose.

  • That doesn't mean, though, that we cannot learn from them.

  • So, tears are mostly made out of water and salt.

  • But there's also more to them.

  • Like saliva, tears have a composition that's pretty similar to blood.

  • They form from blood plasma that gets filtered through the lacrimal glands.

  • So they're an excellent candidate for testing for

  • things you might otherwise look for in blood.

  • For example, the amount of glucose in tears can be correlated to

  • the amount in blood, making it a great candidate for folks with diabetes

  • who want to minimize needles.

  • To harness this property, scientists designed special contact lenses with sensors.

  • Having sensors on your eyeball might not sound like a fun time,

  • but the sensors are embedded in something called hydrogel,

  • a kind of polymer that's soft and squishy like gelatin,

  • so it's more like a regular contact lens.

  • That helps with comfort, but it's also why these contacts work.

  • If the sensors in the lens sense any glucose around, the gel will shrink or swell.

  • And as it does, light will travel through it differently,

  • so the contact lens will actually change color.

  • As glucose concentration increases, you can see the color changing from green,

  • to blue, and then to yellow-red.

  • Fancy contact lenses aren't the only application here, though.

  • Other scientists are directly collecting tears to diagnose breast cancer.

  • The technology is called TearExo, and in it,

  • researchers use a glass chip with an antibody that detects cancer exosomes.

  • Exosomes are little packages that are secreted and passed on to other cells.

  • They often carry proteins, and different types of RNA and DNA

  • used to exchange information between cells.

  • It's like contactless pickup.

  • Food in a bag arrives at your door, and then you bring it into your home cell.

  • Exosomes from cancer cells also have multiple membrane proteins

  • that aren't found in normal vesicles.

  • So If the exosomes from cancer cells are present in the tears,

  • the device will recognize those proteins and tell you in 10 minutes.

  • Finally, most of these techniques so far show us a snapshot in time.

  • But what if a doctor wants to know something about your health from last month?

  • Well, there's an often-overlooked secretion that can tell you just thatearwax!

  • In 2017, it was found that earwax can say a lot about you,

  • from the food you've eaten to exposure to environmental pollutants.

  • That's because similarly to other secretions,

  • earwax contains volatile organic compounds.

  • Here, they're trapped in the oils that form the wax,

  • and can be analyzed in a similar way to the VOCs in your breath.

  • But the big differences are that earwax accumulates over time,

  • storing up a record of VOCs.

  • Also, since the earwax is snuggled in the ear canal,

  • it's protected from other contaminants like perfume, sweat, or cosmetics.

  • So, earwax has been used to diagnose metabolic disorders

  • even before traditional techniques.

  • And these are just some of the overlooked secretions

  • that can tell you a lot about your body, no poking required.

  • And if research keeps going like this, these tests might be the norm in the future.

  • Thanks for watching this episode of SciShow!

  • We've made thousands of educational videos over the years,

  • and we've been able to offer them for free because of our patrons on Patreon.

  • So, to all our patrons, thank you for what you do to make SciShow happen.

  • If you're not a patron but you want to learn more about how to be one

  • so that you can be the reason that we can do this,

  • you can go to Patreon.com/SciShow.

  • [♪ OUTRO]

[♪ INTRO]

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The Secrets Hidden in Your Tears, Earwax, and Other Secretions

  • 38 2
    joey joey に公開 2021 年 06 月 29 日
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