On July 24th, 2018 we learned about

Like humans, tree shrews’ taste buds make spicy peppers palatable

Chile peppers are great, if you don’t mind the whole “sensation of pain” thing. By activating the TRPV1 receptor in an animal’s mouth, the capsaicin in the peppers “burns” and scares off most of the creatures that would otherwise enjoy munching on a colorful, crunchy source of vitamin C. Other animals, like birds with diminished TRPV1 receptors, can just eat chiles without knowing what they’re missing. The real weirdos in all this are the mammals that do experience that harmless bit of pain and then actively seek out more of it. While many humans certainly fall into this last category, the more surprising chile lovers were recently realized to be Chinese tree shrews.

Eating more peppers with less pain

Tree shrews (Tupaia belangeri chinensis) don’t normally eat chile peppers, so it’s a bit odd that this connection was ever uncovered. It started when researchers planning to use the shrews in medical experiments were looking for the animals’ preferred foods, apparently “stumbling” upon the fact that the rat-sized mammals would eat a pepper without the slightest hint of discomfort. In fact, when given the option of corn snacks with or without spicy infusions, the shrews actually preferred hotter blends over blander options. This was in direct contrast mice in the same facility who notably recoiled from any food with spicy capsaicinoids in it.

Aside from the shrews’ overall interest in eating peppers, this gap in the two critters’ reactions wasn’t completely surprising. Despite their name, these tree shrews aren’t rodents, being more closely related to primates like us than to mice, which is why they were of interest to the laboratory in the first place. That said, the real difference in how each animal experienced capsaicin came down to only a single amino acid missing from the shrews’ TRPV1 receptors, making it slightly more difficult for the spice-triggering molecule to do its job. Essentially, the shrews could still taste the spiciness, but just less of it per bite.

Partnering with a spicy plant

Of course, this would be of little use if the shrews never needed to eat something spicy. Without peppers in their natural diet, it’s assumed that the shrews evolved their taste for capsaicin by eating Piper boehmeriaefolium. These plants also produce capsaicinoids, and the shrews may be the only creature evolved to eat them. This has essentially forced the two organisms into a partnership, where the shrews have access to a food source nobody else has the tongue to tackle, while the plants rely on the shrews to scatter their seeds. It’s unclear if this leads to the enjoyment capsaicin-loving humans get from eating spicy food, but the shrews did show a preference for foods that burn like their favorite P. boehmeriaefolium plants they grew up with.

Source: Hot Take: Tree Shrews Love Chili Peppers by Mindy Weisberger, Live Science

On June 5th, 2018 we learned about

Sorting out how microbes survive on supposedly sterilized spacecraft

As much as humans want to discover life on other planets, we also want to make sure we didn’t accidentally send it there. Humans have a bad track record with introducing invasive species on to environments on our own planet, and we would really like to avoid doing so as we explore other planets. Allowing for crewed missions to Mars at some point in the future, a lot of effort goes into decontaminating any spacecraft that will be sent to potential ecosystems, like the Curiosity rover on Mars. Since there’s a good chance that some bacteria may be able to survive a trip through space, these spacecraft are assembled so called “clean rooms,” minimizing contact with the multitude of microbes that live in every other environment on Earth. Bunny suits and sterilization procedures have been fairly successful, but it seems that life has found an opportunity in these otherwise unoccupied environments. Not only have some microbes specialized to live in clean rooms around the world, but they’ve done so by evolving to eat our cleaning products.

Scientists have found traces of a variety of microbes on our spacecraft, including bacteria, fungi and single-celled archaea. To investigate the ecology of these unwanted microbiomes, students from Cal Poly Pomona focused on Acinetobacter, the most common genus of would-be astro-bacteria. Samples were collected from the rooms where the Odyssey and Phoenix spacecrafts were built, then analyzed to see how they could survive in supposedly sterile environments. Even if the bacteria were somehow hearty enough to survive contact with a cleaning agent, it wasn’t clear what these microbes could all be eating in these spaces in order to grow and multiply.

Consuming the cleansers

Normally, a cleaning agent like isopropyl alcohol sterilizes a surface by ripping bacterial cells apart. The lipids in the cell membrane basically dissolve in the presence of alcohol, rupturing the organism entirely. Acinetobacter aren’t necessarily immune to this chemistry, but if they aren’t wiped out completely they do use the alcohol to their advantage. As the alcohol biodegrades, the bacteria actually eat its carbon as their primary source of food. They were also able to take on Kleenol 30, another common cleaning agent. If that wasn’t resilient enough, Acinetobacter turned out to be able to survive a fair amount of oxidative stress. This means that they could possibly handle the higher radiation levels of space, as well as the dry conditions on a planet like Mars.

This doesn’t mean that every spacecraft we build will necessarily lead to a bacterial invasion on other planets. Missions that might involve contact with habitable environments, like the surface of Mars or a wet moon like Enceladus, will simply need to be cleaned more rigorously than before. Knowing how bacteria like Acinetobacter live off of our usual cleaning supplies will spur the development of new strategies, keeping spacecraft clean until the next round of bacterial evolution catches up with us.

Source: Team discover how microbes survive clean rooms and contaminate spacecraft by California State Polytechnic University, Phys.org

On January 1st, 2018 we learned about

Scientists find the molecular mechanisms that help flowers survive their own deadly fragrances

Smelling nice is a luxury for humans. Skipping deodorant isn’t really going to hurt us, although it may bother whomever we stand next to on the bus. For flowering plants, emitting a pleasant, or maybe just strong, smell isn’t a choice. Beyond helping to attract pollinators and signal growth cycles, researchers have learned that flowers must get their attractive odors into the air, because holding them inside would be fatal. Now a series of experiments has figured out exactly how flowers keep themselves safe from their own delightful fragrances.

The gases that we usually refer to as a flower’s fragrance are technically known as “volatile organic compounds,” or simply volatiles. While volatiles tickle our smell receptors when they enter our nose, they’re toxic to the plant cells that produce them. The realization of this critical fact forced scientists to rethink their original model of how flowers release volatiles so animals can smell them, which stated that the fragrant molecules passively diffused through cell walls into the atmosphere. However, that process would actually be much to slow for the health of the plant, prompting further investigation into how plant cells send their scents into the air.

Isolating petunias’ volatile pump

The first part of the study looked at petunias, as they release very few volatiles as buds, but really pour them out when the flowers have bloomed. The contrast between these two phases allowed researchers to look for genes that were more or less active at either time, revealing which genes and therefore molecular mechanisms were being cranked up to push more volatiles out of the flower’s cells. The answer was a type of ATP-binding cassette transporter, which flowers use to not only move volatiles, but other compounds like a leaf’s wax coating as well. The volatiles were actually moved out of the cell thanks to combinations of hydrophilic, or water-attracting, and hydrophobic, or water-repelling molecules. The volatiles themselves are also hydrophobic, and so the right combination of similar and contrasting molecules could effectively shove the volatiles out of the cell after they were produced.

To test this hypothesis, researchers manipulated the transporter genes in petunias and other plants. In flowers that presumably relied on these genes to eject volatiles, the genes were suppressed, leading to less fragrant blooms and eventually more dead cells thanks to a build-up of volatiles. On the flip side, the transporter genes were added to non-flowering tobacco plants, then dosed those plants with potentially dangerous volatiles. As expected, tobacco that had the volatile transporter genes could keep its cells alive by pumping out volatiles. Normal tobacco plants that lacked this extra mechanism couldn’t cope, and died like the genetically modified petunias mentioned earlier. Thanks to these experiments, scientists now know exactly how flowers survive their own scents, and may be able to further control volatile output in the future.

Source: Stopping to smell the roses? You’re inhaling flower farts by Abrahim El Gamal, Massive Science

On November 20th, 2017 we learned about

Compounds in broccoli found to help your intestines keep themselves healthy

The trope that broccoli is a burden to eat is just so wrong. Sure it’s can sometimes be bitter, but that’s not really a problem since it plays well with everything from Ranch dressing to Sriracha hot sauce. It looks like little trees, but is actually a flower! And it’s ridiculously healthy, feeding you nutrients while simultaneously saving your intestines from toxins and pathogens that can cause colitis or the ominously vague leaky gut syndrome.

That last benefit may not be terribly appealing to think about, but it’s important enough that researchers have been investigating the exact mechanism that helps broccoli protect our guts. Starting with a confirmation that that mice who ate broccoli suffered less from digestive issues related to intestinal distress, researchers started focusing on a chemical receptor in the gut called the Aryl hydrocarbon receptor, or AHR. This receptor helps regulate intestinal lining, the microbiome, immune system responses, and the “host barrier function.” While nothing in that list should be discounted, the barrier function is known to be critical to various diseases, and basically functions a mechanism that allows nutrients to be digested into the body while trapping potentially dangerous items, like pathogens or toxins, in the intestine for eventual expulsion.

A delicious dose of indole glucosinolate

Broccoli helps activate all this positive activity thanks to compounds called indole glucosinolates. As you digest your food, the indole glucosinolates break down, creating indolocarbazole (ICZ) in the stomach. This can then plug into the AHR receptor, keeping your intestines happy and inflammation-free. To confirm this relationship, mice were bred to be either extra sensitive to ICZ, or to block its interaction. As expected, the mice that couldn’t make use of the broccoli-produced ICZ suffered from more gut problems, indicating that compound’s importance to a healthy digestive tract.

If you’re hoping to someday bypass the broccoli and trigger your AHR receptor through some kind of ICZ-laden medication, prepare to be disappointed. Over-stimulating the AHR through a body-wide trigger has been linked to problems, like toxicity. This research bolsters the idea that local stimulation of the AHR, as when eating some broccoli, is the safest option out there. If you really can’t deal with broccoli though, researchers suspect that other veggies like brussels sprouts and cauliflower may please your intestines as well.

Source: Like it or not: Broccoli may be good for the gut by Matt Swayne, Penn State News

On June 26th, 2017 we learned about

The biological process that enables Burmese pythons regenerate or reduce organs on demand

As a warm-blooded mammal that’s never too far off from your next snack, it’s hard to appreciate what kind of commitment other animals can make to binge eating. Sure, you’ve maybe eaten too many cookies in a single serving, but you probably didn’t follow that infusion of calories with a month or two of fasting. The Burmese python’s dedication to this meal schedule really ratchets things up, as the snake will literally reduce the size of its internal organs when it’s not eating, then regrow them when it’s time to digest something again.

Burmese pythons (Python bivittatus) are large constrictors, capable of growing to 20-feet-long. At that size, their meals are considerably large, and can include pigs, goats, deer, and occasionally alligators. Since crawling around with large but empty stomachs and intestines really offers no benefit to an unfed snake, the snakes basically allow their organs to atrophy to 60 percent of their functional size. This saves energy on a daily basis as well, further extending how long a snake can go between meals. When it is finally time to chow down, the snakes regenerate the missing tissue so that they can process all the nutrition their prey has to offer. The process is fairly quick too, with organs regrowing in 48 hours, then regressing for around four days after a feeding.

Prompted by proteins

Researchers recently dug into the underlying mechanisms that make this repeated series of changes possible. They found that there were a few key proteins that acted as triggers to activate 1,700 genes throughout the snake’s body. Those genes each created tissue-specific commands for either regrowth or regression in a cascade of activity across lots of different anatomy.

This isn’t just useful to 20-foot-long pythons though. Some of the key proteins that kick off this activity have been found to also affect mammalian cells. For all the specific tasks needed to double the size of a snake’s stomach, there’s a chance that our bodies might be able to make use of some of this strategy as well. It may therefore be helpful in developing treatments for people with damaged organs, spurring regrowth, even without the need for binge-eating.

Source: How pythons regenerate their organs and other secrets of the snake genome, Science Daily

On April 24th, 2017 we learned about

Naked mole rats survive oxygen deprivation by temporarily giving up glucose

Living underground requires a lot of compromises, but naked mole rats seem to be determined to make it work, even if it means reworking their physiology to do so. On top of their insect-like social order, hormone-manipulating poop, and suppressed pain receptors, the latest compromise discovered for these small mammals’ subterranean lifestyle includes somehow surviving a total lack of oxygen. Unlike marine mammals who can plan their breaths and store extra oxygen in their muscle tissue for long dives, mole rats have a built-in metabolic trick for low-oxygen emergencies, and they seem to have borrowed it from plants of all places.

For the vast majority of animals on the planet, metabolic functions are based around sugars like glucose and oxygen. Food energy is converted to glucose that can be distributed around the body so that cells can make use of it when needed. Mitochondria in each cell then crack open that glucose using inhaled oxygen to make adenosine triphosphate (ATP), a molecule that can be used more directly by the cell as a source of energy to continue functioning. If oxygen isn’t so readily available, because you’re possibly in a stuffy tunnel full of other mammals breathing it as well, your cells can make due for a short time with just the glucose. This is a limited, last-ditch option though, as lactose quickly builds up and puts a stop to the whole system. For most mammals, crossing that point is when you go unconscious and cells get damaged until they die.

Sugar switch-over

Since naked mole rats (Heterocephalus glaber) live in large numbers in tunnels with limited ventilation, dying whenever the oxygen supply got low just wouldn’t work. Rather than break up the family into smaller burrows like other rodents, running out of oxygen just triggers an alternate form of metabolism. Since glucose gets hard to work with without oxygen, mole rats will instead start making and metabolizing fructose, a sugar normally only produced in plants. Fructose was still less efficient than glucose for mole rat cells to use, but it didn’t come with the lactose count-down. Energy levels were lower, but steady. In tunnels with as little as 5% oxygen (versus 20% on the surface) a mole rat could carry on for hours with no harm done. For most other mammals, including a similarly-sized mouse, that lack of O2 would be fatal within ten minutes. Even with no oxygen at all, switching to fructose allowed mole rats to survive in a semi-dormant state for 18 minutes.

If the exact mechanics of this metabolic switch-over can be controlled, it may prove to be helpful to those of us living outside cramped tunnels as well. One of the big problems with heart attacks and strokes is how they end up depriving various tissues, like say, the brain, of oxygen long enough for cells to start dying off. If it were possible to buy some extra time, victims of these serious conditions might be able to mitigate some of the additional harm associated with medical crisis.

My second-grader asked: So the mole rats switch to plant mode? If they breathe out enough oxygen, can they make fresher air again?

The mole rats’ ‘plant mode’ doesn’t seem to extend quite that far. They make an alternate form of sugar to supply cells with energy, but they don’t completely rework their respiratory systems in the process, inhaling carbon dioxide and exhaling oxygen like an actual plant. If they did, it would seem conceivable that a colony underground could recycle the air underground, at least enough to avoid members passing out while going about their business.

Source: Sweet? Naked mole rats can survive without oxygen using plant sugar tactic by Hannah Devlin, The Guardian

On March 22nd, 2017 we learned about

NASA drills the desert to test the tools on the prototype KREX-2 rover

The KREX-2 rover recently spent a month digging through dry, rocky terrain, hunting for microbial life. Under the close supervision of 35 NASA scientists, engineers and other staff, the four-wheeled rover explored the arid soil, digging into the dirt to look for signs of life. While all systems performed well, no Martian life was found, because KREX-2 was cruising through the Atacama Desert in Chile as part of NASA’s Atacama Rover Astrobiology Drilling Studies (ARADS). Even without running into actual alien life, the various instruments are on their way towards inclusion in future uncrewed missions to the Red Planet.

Digging in the driest dirt

Before sending a rover to another planet, it’s obviously a good idea to test it as much as possible. It’s hard to completely simulate Mars, but the Atacama Desert is the best proxy on Earth. Located between two mountain ranges, the high-altitude desert is one of the most arid places on the planet. The overall average rainfall is between one to three millimeters a year, although some weather stations have gone four years between precipitation. There’s probably still more life there than on Mars, but that also makes it easier to confirm that the instrumentation is working.

KREX-2 is equipped with a small suite of life-hunting tools, starting with a six-foot drill. The drill can dig into the soil and help gather samples for the Wet Chemistry Laboratory and the clearly labeled Signs of Life Detector. These instruments analyze soil samples for 512 compounds that are somehow tied to biology, either directly or as a byproduct that would indicate the earlier presence of a living thing. Rounding things out is the Microfluidic Life Analyzer, which can detect tiny quantities of water that may be trapped under or inside rocks, then look for amino acids.

Signs from the soil

The ARADS mission went well, with the drill exceeding expectations. Soil analysis indicated that the Atacama Desert has been home to extremely arid conditions for at least 10 to 15 million years, which may be a handy comparison point for future Mars missions. Since Mars doesn’t seem to have the abundant water and atmosphere it likely used to, the signs of life these sensors may someday detect will likely be remnants of microbes from millions (or billions) of years ago.

Source: NASA Tests Life-Detecting Mars Rover Tech in Brutal Chilean Desert by Nancy Atkinson, Seeker

On March 7th, 2017 we learned about

Isolating the mechanisms that let rays, skates and sharks sense electricity

Rays, skates and sharks have a sense that our ancestors gave up (mostly). These cartilaginous fish generally don’t have great eyesight, but they can make up for it by sensing electric activity in their prey. This ability, known as electrosensory, allows something like a little skate (Leucoraja erinacea) to detect prey buried under a layer of sand, picking up the electrical activity of the animal’s heart beat. The basics of this ability have been known for some time, but researchers now say they’ve figured out the underlying biology that makes it all possible.

To try to trace each step of some skates’ electrosensitivity, researchers modified skate’s genomes to isolate different genes that were thought to play a role in the electrosensory organs. Bit by bit, they put together how electrical activity in prey can somehow be detected and transmitted to the skate’s brain. The process starts with voltage-sensitive calcium in specialized cells, which draws in calcium ions when activated. To boost that signal, the calcium ions also trigger potassium in the cell, which causes an oscillation in the surrounding electrical field. This helps get even a faint amount of electricity up to a threshold that will trigger a nerve signal to the skate’s brain.

Electrosensitivity in our ears?

This bit of biochemistry may seem quite esoteric, but it has connections to our own anatomy. The genes involved in detecting electric perturbations were found to be connected to the genes that our bodies use to build our ears’ sensitivity to sound. Long ago, many organisms probably relied on electrosensitivity to find prey, particularly considering the how well electricity conducts in water. Sharks, rays and skates held onto this ability, but other fish repurposed some of these sensors into a structure called a lateral line, which lets them detect movement in the water around them. Eventually, those genes were modified further, and now play a role in how we detect sound.

In the lab, researchers were able to make similar modifications to ion channels on rat cells (not rats) that they carried out on the skates. This similarity helps support the idea of a common point of origin, and may allow for new avenues for research. It’s possible that insight gained from skates’ and sharks’ electrosensitivity will help inform us about how our inner ears send signals to our brains.

Source: Study shows how skates, rays and sharks sense electrical fields, Phys.org

On May 26th, 2016 we learned about

Caffeine can counter the effects of an extended workout

It makes sense that a vigorous workout leaves your muscles feeling tired, but why does a few hours of cycling have to take the rest of your body with it? Exercise can leave various motor systems out of whack, right down to the muscles that control your eyes. This phenomenon, called “central fatigue,” is more tied to your nervous system than your muscles though, which means opens the door to some simple manipulation, such as drinking coffee.

Most of the tiredness you notice after exercising is directly tied to muscles’ exertion. Muscle tissue demands a supply of adenosine triphosphate as it works, which is slowly diminished and replaced by lactic acid as the workout continues. This process can leave you feeling sore, but it’s not so demanding that it should necessarily affect less stressed muscles, much less your central nervous system. Those feelings of wear and tear are thanks to your neurology.

Keeping exercise from becoming exhaustion

Central fatigue isn’t completely understood, but it stems from a shift in your neurotransmitters rather than the direct buildup of lactic acid in your bicep. The best guess is that our bodies respond to continued exertion in this way to slow us down before we hit a point of absolute exhaustion. Hitting your limit may be exciting in the safety of a gym, but our ancestors certainly didn’t want to be surprised during a hunt by suddenly collapsing when their body had no strength left to give. A number of neurotransmitters seem to be in on this dynamic, including serotonin and dopamine.

A quick fix, if you’re looking to rebound after a workout that leaves you drowsy, is as simple as some coffee. Moderate doses of caffeine were found to alleviate the measured eight percent drop in test-subjects’ eye movement, helping them feel perkier while the adenosine was blocked in their brains. Since this dynamic takes place outside your exercised muscles, it shouldn’t impact the benefits of the workout, assuming you don’t use the coffee as an excuse to bike another couple of hours and really burn yourself out.

Source: Exercise doesn’t just tire your muscles—it makes your eyes sleepy by Ian Randall, Science Magazine

On May 19th, 2016 we learned about

Chemical emanations may reveal our emotional state

It turns out the idea of “smelling fear” might not be so off the mark. Humans, like all living things, emit various gaseous byproducts all the time, most of which we’re not consciously aware of. However, it seems that the makeup of those gases shifts with our moods, and that some emotional experiences can somehow trigger detectable changes in our collective smell.

Emotionally-oriented odors weren’t discovered thanks to an individual with really strong reactions, but with really big crowds. Over the course 108 screenings, 9,500 test participants’ air supply was monitored for changes in composition. A device called a proton transfer reaction mass spectrometer (PTR-MS) was used to pick detect 100 of the 872 volatiles humans are known to emit, allowing researchers to “smell” changes in the room with great sensitivity. Notable spikes in a single compound were then matched to the content in the movie at that moment, looking for correlations between particular moods and odors.

The chemical traces of tension

The strongest shifts in volatiles came when the audiences were watching something funny, or when there was a scene building tension or depicting injury. For example, a scene in The Hunger Games: Catching Fire that depicts the protagonist struggling with her burning dress matched a spike in isoprene in the theater. Isoprene is generally understood to be tied to muscle activity as well as cholesterol synthesis. Researchers can’t be sure yet if the increased isoprene detected was due to the collective tensing of muscles as viewers worried about their heroine, or if it was tied to the stress hormone cortisol via cholesterol. Another bump in isoprene was detected when audience members left the theater, probably due to muscle activity, but that was a lot more activity than nervous viewers gripping their armrest in excitement, so it’s unclear what the exact cause was.

The other question is if these volatile compounds serve an evolutionary purpose, or if they’re just a byproduct of metabolism. While we don’t consciously notice subtle odors like this, it’s possible they offer a non-verbal form of communication for moments of potential danger, or in the case of comedy, a signal that all’s clear. If it isn’t serving our biological noses, detecting changes in mood with electronic noses may still be of value. At a minimum, it can be used to gauge reaction and mood when test audiences screen next year’s big blockbusters.

Source: The chemicals we off-gas change when we watch something funny or thrilling by Beth Mole, ArsTechnica