On September 27th, 2017 we learned about

How chemistry lets us put pumpkin, orange or butter flavors in practically any food

It’s fall, which means every other item at my local Trader Joe’s now has pumpkin in it. Or the essence of pumpkin, at least. You know, that lovely cis-3-Hexen-1-ol (C6H12O) that your nose senses after you slice into a big, orange gourd to carve a jack-o-lantern. Or the always nostalgic dash of sabinene (C10H16) that you taste in a good pumpkin pie, and naturally, pumpkin tortilla chips, which are also a thing… These products probably do have their fair share of pumpkin puree, but sometimes smushed pumpkin isn’t even what we really expect to taste when offered a “pumpkin flavor” product. This isn’t really a problem either way, since really what’s going on pumpkin and other flavors is just some refined manipulation of how we perceive flavor in the first place. And probably sugar.

Compounds that are convincing to your nose and brain

You might not have anything labeled cis-3-Hexen-1-ol on your spice rack, but it’s actually one of the various compounds you’re likely to notice when you cut into a ripe pumpkin. Alongside a few other alcohols and aldehydes, the right ratios of these molecules hitting the right smell receptors in your nose will get your brain working to identify what is causing the aroma. With a pumpkin in front of you, that particular blend gets labeled as “fresh pumpkin smell” in your memory, although none of those compounds are terribly unique. When you taste (and smell) the food you eat, your brain is simply referencing memories of other times you’ve had those particular smell receptors get activated in some particular proportion.

Now, cis-3-Hexen-1-ol is a decently large molecule, but only one portion of it is needed to activate a smell receptor. Rather than have a receptor that can accommodate the entire molecule at once, your nose only really cares about the OH at the end. This is very convenient for chemists, who can attach that smell signifier to other compounds that may be more stable, cheaper or somehow easier to work with than what the pumpkins make themselves. It’s a concept that gets used in tons of different foods, with these artificial flavors often being mixed back into the foods they originated in.

Close control over foods’ flavors

As food production shifted to industrial scales in the early 20th century, manufacturers needed food that could survive longer in transport and on shelves, bring down costs, and also taste consistent from one helping to the next. As with pumpkins, oranges have had their chemistry parsed to see which molecules trigger the experience of “orange flavor,” so that it could be used in other products, as well as orange juice itself. By adding something like ethyl butyrate to orange juice, manufactures can be sure that a crop of bland oranges won’t tank their sales for a season. Similarly, diacetyl was added to products to give them a buttery taste, but the flavor association was so successful that creameries now spike actual butter with the compound, so that butter tastes more like what our brains think of as butter.

In the case of the deluge of seasonal pumpkin products, we also have to accept that we’re not sure what we want to taste. While cis-3-Hexen-1-ol is found in actual pumpkins, that’s not a smell you’re really looking for in your coffee or pumpkin biscotti (which is also a thing.) In those cases, the target flavor is actually pumpkin pie, which is why recipes also include sabinene for nutmeg, eugenol for cloves, and cinnamaldehyde for cinnamon. As ubiquitous as this now seems, it’s not an easy batch of flavors to get right since one person’s perfect pie might not match the expectations of someone else. This led Jelly Belly candies to even temporarily abandon their attempt at pumpkin pie flavor, at least until they embraced the variability inherent in the task by billing the candies as their “family’s” own recipe. Fortunately for manufacturers, sugar helps smooth things out considerably, as it’s certainly a flavor that our brains remember as “yummy.”

Source: The Absurd History of Artificial Flavors by Alison Herman, First We Feast

On September 20th, 2017 we learned about

Policing and preventing the burl poaching that puts redwood forests at risk

How much would you pay for a piece of a tree’s metabolic dysfunction? What if was the shape of a wall clock or coffee table? Even if you’re hesitating, there’s enough demand for what’s essentially deformed wood that national and state park rangers have begun working with police to deter poachers. The wood, known as burls, is valuable enough that so called “midnight burlers” are sneaking into parks under the cover of night, removing portions of trees and possibly putting the forest at risk.

Twisted tissue in tree tumors

You’ve probably seen a burl at some point, as they’re not uncommon on large trees. Thanks to an injury or just exposure to infected soil, a tree will become infected with bacteria like Agrobacterium tumefaciens or fungi like Exobasidium vaccinii. The pathogen will alter the plant’s DNA, causing the metabolism speed up growth in one part of the tree, essentially resulting in a large, woody tumor. As the growth gets bigger, it can bulge out from a tree trunk, sometimes ending up with a larger diameter than the tree itself. Trees can survive with one or multiple burls for many years, although there is evidence that they’re a bit of a drain on the tree’s health, as burl-carrying trees tend to die earlier than their burl-free kin.

While the trees don’t benefit from growing burls, woodworkers love them. When cut open, burls reveal a much more chaotic, randomized structure than healthy trunk. The wood grain in a burl is swirled and uneven, often containing multiple shades of color, and can be polished for rather spectacular effect. Importantly, it’s also just very different from healthy wood, and that rarity is what’s making it valuable enough for poachers to steal, even out of State and National parks.

Blocking the burlers

California’s redwood forests have been targeted by poachers for the last few years. Morning patrols would turn up massive trees with enormous holes chopped out of their trunks. With over a hundred thousand acres of forest to patrol, there’s been little hope of catching thieves red-handed, as the poachers can cut a burl and deliver it to a buyer in a single night. The wood buyers are somewhat complacent, but aside from weird delivery hours, there hasn’t been a clear way for them to obviously know when a burl has been illegally harvested.

That might be changing though, as rangers and law enforcement have been trying new tactics to slow down the poaching. Careful mapping of which trees were attacked revealed that poachers aren’t picking the best or most hidden burls, but simply targeting trees close to the road. This has allowed rangers to better plan their patrols, reducing the amount of territory they might need to guard each night. After a tree is poached, advances in DNA analysis may soon make it easy to identify which tree a particular burl came from. By making the wood traceable, wood buyers may need to become a little more thoughtful about where their supplies come from.

Fighting for the forest

While trees generally do better without burls, preventing poachers from cutting them off is good news, especially for redwoods. While the burls represent a metabolic disorder, they’re also packed with nutrients. Losing a dense ball of nutrients isn’t great for the adult tree, but it’s also bad for redwoods’ suckers. When the young trees try to start growing, a missing burl robs them of a considerable source of nutrients, hurting the forest’s natural rejuvenation. Additionally, since many poachers are working with chainsaws as quickly as possible in the middle of the night, the cuts to remove the burls are often rough and haphazard, raising the remaining tree’s risk of new infections.

It should be noted that not all burled wood is obtained illegally. Many woodworkers harvest burls from less vulnerable species of tree, and do so in a more responsible way. As demand, and prices, rise, more midnight burlers are likely to try to pass their goods off as legitimate. At this point, it’s in everyone’s interest to make sure the poached wood is kept out of the market, and our living rooms.

My kids said: Maybe if the poachers know that they’re hurting the redwood trees they’ll stop.

That would be fantastic. Unfortunately, poaching markets seem to be tied not just to demand from buyers, but also to downturns in other parts of the economy. Chances are, many poachers feel like they don’t have a lot of choices, and a few thousand dollars for some stolen wood seems like the easiest answer.

Source: How Forest Forensics Could Prevent the Theft of Ancient Trees by Lyndsie Bourgon, Smithsonian

On September 3rd, 2017 we learned about

Your body’s efforts to cool down use up a lot of extra energy

Living through history can be exhausting, especially when that history concerns heat waves. My kids and I have spent the last few days scrambling to avoid the record-setting temperatures that recently cooked the Bay Area. While we thankfully avoided serious health concerns like heat stroke or severe dehydration, there were plenty of moments where the most sensible course of action seemed to be to lie on the ground in front of a fan and hope for the best. Part of this was psychological, but part of it was because living in extreme heat is simply hard work for your body. While it’s a passive process for the most part, sweating buckets can burn some calories, even without any exercise.

Extra work for overheated endotherms

Your body has a few tricks it employs to try and control your temperature. When it’s cold, you’ll likely notice things like shivering to get your muscles to generate some heat, but cooling down can sometimes be more subtle. For example, your body will dilate blood vessels to get more blood near the surface of your skin, leaving you looking a little pinker than usual. That blood is carrying more heat towards the outer surface of your body to keep your core cooler, and ideally let the surrounding air wick some warmth away. Many animals have special anatomy to maximize this trick, but humans have to make due with activated blood vessels, which is more work than when you’re feeling cool.

Even if you don’t actively choose to sweat, it’s not an effortless process. Your body is rerouting water to your skin for a very effective cooling process, but it has to boost your metabolic rate to do so. This means that your heart works harder, and you may push yourself closer to dehydration to cool down. Dehydration alone can cause fatigue, so it’s easy for it to wear you out when you’re drying out to cool down.

Finally, all this heat can require actual repairs. Ultraviolet light from the Sun can of course cause damage to your skin, and while a bad burn may feel like it just sits there for ever, your body starts trying to repair itself right away. In addition to trying save cells, burned skin also demands more of your body’s water reserves, increasing your dehydration risk even more.

Help yourself beat the heat

So feeling tired at the end of a hot day makes sense, even beyond the way that intense heat can sap your will to function. If you can’t just take a siesta until things start to cool off in the evening, consider assisting your body in its efforts to lower your temperatures. Aside from moving to a cooler environment, drink lots of water to avoid dehydration, throwing in some salty snacks to help retain that water. You can also help maximize the effect of your heat-pumping blood vessels by trying to cool your blood as it circulates, putting a cool, damp washcloth on your neck, wrists, feet or other key anatomy. You probably won’t feel fresh as a daisy at the end of the day, but it should help you get the most from the effort your body is putting into keeping you cool.

Source: Why Does Being in the Heat Make Us Feel Tired? by Laura Geggel, Live Science

On August 30th, 2017 we learned about

Caffeine curtails your mouth’s ability to sense sweets

Science has discovered a great way to keep my kids away from soda (and coffee.) Even though the caffeine in these drinks feels like it amps us up, it’s actually doing so by blocking activity in your adenosine receptors. That’s not going to scare my kids away from caffeinated drinks, but they were a bit worried by the fact that it also suppresses our ability to taste sweet flavors. For an eight- and a four-year-old, no amount of alertness is worth the satisfaction of sugar, even if that drink has sugar itself.

This effect was tested in a lab with coffee alone. All participants were offered coffee sweetened with the same amount of sugar, then asked to rate how alert they felt, and what they thought of the coffee’s flavor. What these folks didn’t know was that all the coffee was originally decaffeinated, and only the experimental group’s beverages had 200 milligrams of caffeine added back in. This allowed researchers to control exactly how much caffeine was being ingested, and rule out differences in flavor between regular and decaffeinated grounds.

Half the sugar and all the caffeine

Test participants who had recaffeinated coffee consistently rated it as tasting less sweet than people who drank straight decaf. Nobody caught on to the difference in the beans though, as just about every participant felt that they were perked up by their beverage, suggesting that there was a placebo effect at play. Even if that placebo was somehow slowing adenosine receptors in people’s brains, nothing was blocking their taste receptors.

The concern here is that caffeinated folks might crave the sugary sensation that they’re not tasting, even though they’re still eating it. Rather than settle for less, they may compensate for the perceived lack of sugar by eating more, upping their calorie count without really being aware of what’s going on. Since my wife and I are theoretically gatekeepers on our kids’ sugar intake, they’ve decided not to risk missing out on the sugary snacks they’re allowed to enjoy, and made pledges to avoid soda (and my coffee.)

My third grader asked: So when my cousin drinks those sodas he can’t taste dessert as well?

That’s the gist of this experiment. The first sip of a soda should be delightfully sweet, but as the caffeine kicks in, taste receptors would be temporarily blocked and the drink would taste just a bit less sugary. So what’s the point in that, right?

Source: Caffeine Tempers Taste, Triggering Temptation For Sweets, Scienmag

On July 17th, 2017 we learned about

The mathematical model that describes how body size sets top speeds

If video games have taught me anything, it’s that bigger characters hit harder, but move slower. This always felt pretty intuitive, to the point where giant characters in fantasy stories are depicted as moving in slow motion compared to human-sized folks. The thing is, movement is tied to our muscle strength, and that strength is (at least partially) due to muscle size, which would suggest that bigger creatures should move faster, not slower. Nobody’s seen an elephant run at 373 miles per hour though, so it looks like reality is siding with video games here, and we finally have the math to prove it.

Fighting physics and fatigue

Myriam Hirt, a zoologist from the German Center for Integrative Biodiversity Research, came up a formula to predict how size influences speed. The first factor is the animal’s mass, which not only dictates the amount of muscle available, but also the amount of inertia that animal has to overcome to start moving. So a large elephant may have some impressively large muscles, but it takes a lot more work to get those legs moving. This is different from weight, which is the influence of gravity on the body’s mass. If you moved an elephant to the Moon, it would weigh less, but still have a lot of inertia since the size of its body didn’t change. The upside of this is that if you did get an elephant moving that fast, it’d be remarkably difficult to then get all that mass to stop.

The second factor is the animal’s anaerobic metabolism, which explains why an elephant isn’t about to do that extra work to break into a swift sprint. Most of the time, a body relies on aerobic metabolism, which uses oxygen to provide energy to your cells, and is used in longer, lower-intensity activities like a long walk. For a quick burst of energy, like sprinting at top speed, muscles use anaerobic metabolism, which burns sugars like glucose directly. This allows for fast twitch activity in muscles, but produces byproducts like lactic acid, putting a cap on long muscles can work this hard. Taken together, the fastest elephants have only been observed hitting 25 miles per hour.

Mutual maximums

In the case of our charging elephant, overcoming the inertia of its mass requires too much anaerobic activity to work. The animal’s large muscles may give it a lot of strength and endurance, but not enough to rocket forward like a cheetah. In fact, across animals moving on land, sea and the air, the same size ratios held true 90 percent of the time. Like a bell curve, small bodies have little inertia to overcome, but lack the muscle to give them much power. Large bodies are too big to get moving before the muscles start to burn out. The sweet spot to maximize speed and size is then in the middle, around the size of a cheetah. Cheetahs have other adaptations that make their bodies even more efficient sprinters, like their super-flexible spines, but the size still matters. A double-sized cheetah wouldn’t be nearly as energy efficient and would like be unable to reach the same 74-mile-per-hour speeds.

This formula does more than confirm the speeds of animals we’re all familiar with. Thanks to it’s high accuracy, it can help us estimate the speed of animals we can’t observe, like dinosaurs. We’re estimating body mass in extinct animals as well, but baring other adaptions to improve performance, it’s fair to assume that a Velociraptor could have run at 34 miles per hour, in contrast to a much bulkier Tyrannosaurus would have only hit 17 miles per hour. Big bodies can provide a lot of power, but physics requires that they also take a lot of work to move around.

Source: Why the Biggest Animals Aren't the Fastest by Stephanie Pappas, Live Science

On July 12th, 2017 we learned about

Muscle strength depends on how well you train your motor neurons

To really achieve your athletic potential, you must strengthen your mind and your muscles. As much as that may sound like a platitude from a motivational poster, it’s actually based on a series of experiments comparing how muscle mass may or may not impact physical strength. Muscles are still the key mechanical actors in these emerging model, but it looks like well-trained motor neurons are the anatomy that can give you access to more of your body’s strength.

Now, nobody is debating the idea that, in general, a larger muscle can do more work than a smaller one. More muscles cells can share the stress of a particular contraction, achieving movement without incurring the damage a smaller muscle would. However, bulky muscles aren’t able to do more work just because they’re big. To get bigger, they’ve presumably been trained along the way, which helps the muscle cells activate simultaneously. Untrained muscles will activate asynchronously, which may protect them from overexertion and damage, but also decrease their effectiveness.

More strength from the same muscle

Not all strength training is turning out to be equal. One on hand, many repetitions of lighter weights is being found to be effective as fewer repetitions of heavier weights to build muscle mass. It may take longer, but lifting lighter weights can help you develop larger muscles. The catch is that lifting larger weights seems to not only train muscles, but also motor neurons, which changes how well you can put your quads, biceps or triceps to work.

This relationship was tested in a variety of ways. One test involved electrically stimulating muscles to see if heavy and light weights produced muscles with different limits on their output. Another test asked participants to do a matching task, and found that the muscles trained on heavier weights didn’t need to work as hard to complete it. In every case, matching muscle sizes didn’t matter as much as the way those muscles had been trained. Researchers aren’t sure why heavier weights are more effective at training our motor neurons in this way, but it suggests that lifting weights close to your limit may be more effective at raising what that limit is.

Source: Why Strength Depends On More Than Muscle, Scienmag

On June 21st, 2017 we learned about

How Rebecca Huit heaved a Hummer over her head, plus handled her flaming fingers

Sciencing the Sisters Eight!

Rebecca Huit is one of the younger sisters in The Sisters Eight, but she commands an outsized amount of attention from her siblings, even before gaining her powers. When she does start demonstrating unusual abilities, it’s unclear what’s happening at first, because she manifests both inhuman strength and incendiary fingertips. There’s little reason to suspect these abilities are tied to each other, and so we’ll unpack each power on their own.

More massive muscles

The development of Rebecca’s strength may have two distinct causes. At the opening of Rebecca’s Rashness, we find that Rebecca is vigorously training at all hours of the day, and getting eye-popping results. She’s able to easily support the full weight of her sister, Petal, from one arm with no sign of fatigue, indicating that she’s somehow gotten a lot stronger than the average seven-year-old. The book fails to mention any changes to Rebecca’s appearance, but there’s a chance that she’s suddenly been building muscle mass because her body has stopped blocking its growth.

Many mammals, including humans, cats, cows and dogs, naturally create a protein called myostatin. This protein acts as a regulator on our muscle development, keeping us from building excessive amounts of muscle that might cause a drain on our energy levels without much practical gain from an evolutionary standpoint. When genetic mutations, or a decrease of another protein called follistatin, somehow leave an animal without myostatin, muscles develop to unusual sizes, greatly increasing the creature’s strength. Even newborn babies lacking myostatin will show bulk in their leg muscles, and can lift over six pounds in one hand by the time they’re four and a half. If Rebecca has suddenly dropped her myostatin production, developing enough muscle to lift Petal wouldn’t be a big challenge.

Hoisting the Hummer

Shortly thereafter, Rebecca amazes her family by lifting up an entire Hummer, raising it over her head. Hoisting 6400 pounds into the air is a far cry from supporting an older sister, and even new muscle growth might not account for the amount of strength necessary. Since Rebecca was lifting the Hummer to help her friend Pete, there’s a good chance that she was tapping into what’s known as hysterical strength. This is the strength that people tap into in emergencies to do things like… well, rescuing friends trapped under cars. In real life, these people are usually only lifting a quarter of the car’s weight to free someone, and they’re not actually using more strength than their muscles normally offer— it’s just more strength than the body ever wants to use.

Like the myostatin that keeps our muscle production in check to save resources, our brains normally cap our muscle exertion below their physical limits. This provides a buffer for our safety so that we don’t damage muscles, ligaments, tendons or bone. It also helps us save some calories to get home to recuperate after exertion, rather than leave us completely limp on the ground. Hysterical strength isn’t achieved with boosted muscles then, but by removing the feelings of pain and fatigue that normally keep things in check at around 60% of our potential strength. People who have experienced hysterical strength have sometimes paid a price in self-induced injuries, although they usually don’t notice things like eight cracked teeth until they’ve calmed down after the triggering emergency.

Hot hands

For better or for worse, the flames that later shoot from Rebecca’s fingers aren’t tied to emergency responses, as she can set things ablaze at will. Flames are described as blasting from her fingers, indicating that there’s some sort of pressurized fuel source to push the fire away from her hands, like the pressurized nozzles on a flamethrower. Unlike a flamethrower, we see no sign of a pilot flame though, so some other mechanism must be heating things up enough to burn things down than traditional fuels like propane or butane.

A model for spraying flammable fuels is the African bombardier beetle. When threatened, this beetle can spray a mix of hydrogen peroxide and hydroquinones that combine in mid-air to form oxygen, boiling water and benzoquinones. None of these components aren’t literally combusting during this reaction, but the resulting spray can cause chemical burns, clouds of vapor and intense heat, sometimes as high as 200° Fahrenheit. Potential predators hit this cocktail are likely to be burned and incapacitated, allowing the beetle to escape danger. It’s not going to literally set your drapes on fire necessarily, but if Rebecca was spraying anything like this out of her fingers it would still cause plenty of damage.

Overall, this all leaves Rebecca as a very dangerous, volatile girl, and most people wouldn’t want to risk being near these abilities on the best of days. The combination of extra strength operating at its full capacity, even temporarily, while spraying noxious, burning chemicals is so extreme that Rebecca’s eventual imprisonment really seems like the only rational option for the remaining siblings. As well as the surrounding neighborhood.

Source: The Man of Steel, Myostatin, and Super Strength by E. Paul Zehr, Scientific American

On June 14th, 2017 we learned about

Trip to space seems to have spurred a flatworm to regenerate a second head

It may sound like something out of a 1950’s science fiction story, but spending time in space has apparently spurred a flatworm into growing two heads. Flatworms are actually known for their regenerative abilities, and this particular worm was actually cut in half before heading into orbit on the International Space Station (ISS) in the hope that it would regrow its body. However, regenerating with a second head, along with a number of other abnormal developments, isn’t exactly what scientists were expecting when designing the experiment. The second head doesn’t mean we need to fear radioactive space monsters from outer space, but it does raise concerns over long-term health effects of living away from the Earth.

Altered in orbit

Planarian flatworm (Dugesia japonica) regeneration is usually much more predictable. The tiny creatures regularly handle fission without a problem, and can use it to boost populations. A single worm splits in half, and each half regrows whatever pieces are missing. So usually a tail will regrow a head, and a head will regrow a tail. Researchers have known that a two-headed variation was technically possible, but the Tufts University researchers had never encountered a two-headed worm before, even after 18 years of research. What’s more, the underlying change must have been substantial, as that two-headed flatworm returned from space only to continue making two-headed copies of itself.

The other flatworms have also exhibited changes to their physiology and behavior, although they’re understandably less dramatic than growing a second head. They exhibited an reaction to fresh water when first returning home, becoming temporarily paralyzed when first immersed. They also don’t show flatworms’ normal aversion to light, and will not seek out darker portions of their containers when given the chance.

Changes from flying and floating

It’s not clear what is driving these various changes. A change in the worms’ microbiomes may help explain the temporary reaction to fresh water, and other research has already shown that bacteria notice when they’re in microgravity too. Other influences include a diminished pull from the planet’s geomagnetic field, stress from takeoff and landing, or just issues related to floating in microgravity while on board the space station.

At this point, scientists have a good understanding of what chemical changes could change a flatworm, since those things can all be tested here on the ground. Isolating what are likely mechanical influences from traveling to and in space are a new frontier, but they need to be understood if humans hope to export our lifestyles to other planets. Nobody believes that astronauts will sprout second heads after being in space, but animals like flatworms are still a good way to study the importance of gravity on living systems, partially thanks to their dramatic reactions to that environment.

Source: Flatworm Travels to Space With One Head, Comes Back With Two by Nathaniel Scharping, D-brief

On June 13th, 2017 we learned about

The debates and designs that resulted in the humble rubber reflex hammer

Today, while waiting in the doctor’s office for a checkup, my second grader proudly announced that she recognized the reflex hammer sitting on the counter, and that she’d figured out how to replicate its function with both her hand and lunchbox. When the doctor actually tested my daughter’s patellar ligament, there was a little disappointment that the iconic rubber hammer wasn’t used, as the doctor struck her knee with the rubber edge of her stethoscope instead. The stethoscope was effective at triggering the reflex, maybe even better than a well aimed lunchbox, so how did these hammers end up in doctors’ toolkits in the first place?

Medical grade rubber hammers were originally designed to look for fluid built up in people’s chest cavities. After seeing innkeepers thump the side of wine casks to hear how full they were, Dr. Leopold Auenbrugger suggested hitting chests with a percussion hammer to see how hollow they sounded. The idea caught on, but the design was criticized and reworked from all corners. Potential replacements looked like everything from a battle axe to a magic wand. Rubber wasn’t locked down as a material either, as doctors considered whacking their patients with ebony, whale bone, brass, lead and velvety yarn.

Knocking knees for nerves

It wasn’t until 1875 that Drs. Heinrich Erb and Carl Friedrich Otto Westphal noticed what’s been fascinating my daughter— tapping a tendon or ligament can cause the associated muscles to automatically flex and relax. The patella ligament under your knee, for instance, sends a signal through your spine to your alpha motor neuron, which then activates your quadriceps in your thigh. This response is normally used by the body to automatically maintain posture and balance without worrying about it, but for doctors it’s a handy way to diagnose an array of possible maladies. When a knee is jerked more or less than expected, it can help reveal where in the body other symptoms might be stemming from.

The iconic triangular, rubber hammer you’re likely to see at the doctor’s office was developed by Dr. John Madison Taylor in 1888. The design hasn’t changed a lot since then, but it’s not the final iteration of reflex hammers at doctors’ disposal. If the nervous response of other parts of the body are to be tested, a variety of more specialized hammers are available, such as the Krauss hammer that was designed by Dr. William Christopher Krauss. Some have large round heads for knees, small balls for biceps, and thinner structures for stimulating the skin. Of course, if all else fails, a good thump from a thumb might still do the trick as well.

Source: Digital Schmigital: After 130 Years, Reflex Hammer Still Going Strong by Bret Stetka, KQED Future of You

On May 30th, 2017 we learned about

Light-licking mice reveal which taste receptors can actually taste water

Lab mice have been trained to drink light. This involved a bit of work, but the motivation wasn’t so hard since the mice were convinced they were drinking water. The trick was just engineering them to have tongues that could mistake a stream of photons for an actual sip of H2O, which is neat since most of us can barely describe what water tastes like in the first place.

Which cells sense water?

Backing up a bit, researchers were looking for the physiological mechanisms that tell an animal when it’s drinking water versus some other, less hydrating liquid like oil. Our sense of taste informs us about most of the food we put in our mouths, although that requires distinct flavors and smells, which isn’t something we associate with (clean) water. Neurological evidence suggested that our brains have a distinct response to water in our mouths, but to figure out what triggers that activity, researchers started messing with mouse tongues.

Mice were bred with various alternations to the genes governing their taste receptors on their tongues. With a type of receptor disabled, the mice were offered water or similarly clear, tasteless silicon oil to see if they noticed any difference. The mice that lacked receptors normally associated with sour, acidic flavors took longer to notice the difference, so researchers targeted those cells for the next phase of experimentation.

Light instead of liquids

The next step was to raise mice with optogenetic taste receptors on their tongues. Optogenetics is a research technique that makes specific types of cells sensitive to light. Often used in studies of the brain, researchers can then target and activate the genetically engineered cells to prove their role in a particular process. In this case, the sour-sensing taste receptors were made sensitive to light, so that light on the mouse’s tongue would be perceived as a normal food or liquid stimulus, like water. Using a water bottle rigged to emit light, the mice lapped away at the light, eagerly attempting to quench their thirst even though no actual liquid was present.

At this point, the sour-sensing taste receptors appear to be central to how mice, and presumably other mammals, taste water on our tongues. Researchers suspect that drinking water normally washes saliva out of our mouths, changing the acid levels on our tongues to activate these cells. However, the light-drinking mice also revealed that further mechanisms must be at play when getting a drink. As much as the mice were convinced they were lapping up water, they never acted sated by the activity. It seems that the tongue may help indicate when we have water in our mouths, but some other mechanisms were waiting for a real liquid to indicate when to stop drinking.

Source: Scientists discover a sixth sense on the tongue—for water by Emily Underwood, Science Magazine