By Amber Dance We’ve all heard of the five tastes our tongues can detect — sweet, sour, bitter, savory-umami and salty. But the real number is actually six, because we have two separate salt-taste systems. One of them detects the attractive, relatively low levels of salt that make potato chips taste delicious. The other one registers high levels of salt — enough to make overly salted food offensive and deter overconsumption. Exactly how our taste buds sense the two kinds of saltiness is a mystery that’s taken some 40 years of scientific inquiry to unravel, and researchers haven’t solved all the details yet. In fact, the more they look at salt sensation, the weirder it gets. Many other details of taste have been worked out over the past 25 years. For sweet, bitter and umami, it’s known that molecular receptors on certain taste bud cells recognize the food molecules and, when activated, kick off a series of events that ultimately sends signals to the brain. Sour is slightly different: It is detected by taste bud cells that respond to acidity, researchers recently learned. In the case of salt, scientists understand many details about the low-salt receptor, but a complete description of the high-salt receptor has lagged, as has an understanding of which taste bud cells host each detector. “There are a lot of gaps still in our knowledge — especially salt taste. I would call it one of the biggest gaps,” says Maik Behrens, a taste researcher at the Leibniz Institute for Food Systems Biology in Freising, Germany. “There are always missing pieces in the puzzle.” A fine balance Our dual perception of saltiness helps us to walk a tightrope between the two faces of sodium, an element that’s crucial for the function of muscles and nerves but dangerous in high quantities. To tightly control salt levels, the body manages the amount of sodium it lets out in urine, and controls how much comes in through the mouth. © 2023 Annual Reviews

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28908 - Posted: 09.16.2023

By David Grimm Apart from Garfield’s legendary love of lasagna, perhaps no food is more associated with cats than tuna. The dish is a staple of everything from The New Yorker cartoons to Meow Mix jingles—and more than 6% of all wild-caught fish goes into cat food. Yet tuna (or any seafood for that matter) is an odd favorite for an animal that evolved in the desert. Now, researchers say they have found a biological explanation for this curious craving. In a study published this month in Chemical Senses, scientists report that cat taste buds contain the receptors needed to detect umami—the savory, deep flavor of various meats, and one of the five basic tastes in addition to sweet, sour, salty, and bitter. Indeed, umami appears to be the primary flavor cats seek out. That’s no surprise for an obligate carnivore. But the team also found these cat receptors are uniquely tuned to molecules found at high concentrations in tuna, revealing why our feline friends seem to prefer this delicacy over all others. “This is an important study that will help us better understand the preferences of our familiar pets,” says Yasuka Toda, a molecular biologist at Meiji University and a leader in studying the evolution of umami taste in mammals and birds. The work could help pet food companies develop healthier diets and more palatable medications for cats, says Toda, who was not involved with the industry-funded study. Cats have a unique palate. They can’t taste sugar because they lack a key protein for sensing it. That’s probably because there’s no sugar in meat, says Scott McGrane, a flavor scientist and research manager for the sensory science team at the Waltham Petcare Science Institute, which is owned by pet food–maker Mars Petcare UK. There’s a saying in evolution, he says: “If you don’t use it, you lose it.” Cats also have fewer bitter taste receptors than humans do—a common trait in uber-carnivores. But cats must taste something, McGrane reasoned, and that something is likely the savory flavor of meat. In humans and many other animals, two genes—Tas1r1 and Tas1r3—encode proteins that join together in taste buds to form a receptor that detects umami. Previous work had shown that cats express the Tas1r3 gene in their taste buds, but it was unclear whether they had the other critical puzzle piece.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28885 - Posted: 08.26.2023

By Aara'L Yarber When the pandemic began, losing your sense of smell was considered a key indicator of covid-19, and the condition affected about half of those who tested positive for the coronavirus. However, a new study reveals that the chance of smell loss from the latest omicron variants has dropped dramatically since the early days of the pandemic. “So now, three people out of 100 getting covid presumably may lose their sense of smell, which is far, far less than it was before,” said study leader Evan Reiter, the medical director of Virginia Commonwealth University Health’s Smell and Taste Disorders Center. The findings, published in the journal Otolaryngology — Head and Neck Surgery, mean that losing smell and, by association, your sense of taste is no longer a reliable sign that someone has a covid infection, Reiter said. Advertisement “Now, the chance of you having [smell loss from] covid as opposed to another virus, like different cold and flu bugs, is about the same,” he said. Although it is unclear why the frequency of smell loss has decreased over time, vaccinations and preexisting immunity could be playing a role, the researchers said. Doctors have had difficulty explaining the cause of smell loss, but some research suggests it is due to covid triggering a prolonged immune assault on olfactory nerve cells. These cells sit at the top of the nasal cavity and help send smell signals from the nose to the brain. It is possible that over time this attack causes a decline in the number of olfactory cells. But if you’ve already been infected or vaccinated, the time the virus has to inflict this kind of damage is dramatically reduced, said Benjamin tenOever, a professor of microbiology and medicine at New York University who was not involved in the study.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28866 - Posted: 08.05.2023

By Wynne Parry For the first time, researchers have determined how a human olfactory receptor captures an airborne scent molecule, the pivotal chemical event that triggers our sense of smell. Whether it evokes roses or vanilla, cigarettes or gasoline, every scent starts with free-floating odor molecules that latch onto receptors in the nose. Multitudes of such unions produce the perception of the smells we love, loathe or tolerate. Researchers therefore want to know in granular detail how smell sensors detect and respond to odor molecules. Yet human smell receptors have resisted attempts to visualize how they work in detail — until now. In a recent paper published in Nature, a team of researchers delineated the elusive three-dimensional structure of one of these receptors in the act of holding its quarry, a compound that contributes to the aroma of Swiss cheese and body odor. “People have been puzzled about the actual structure of olfactory receptors for decades,” said Michael Schmuker, who uses chemical informatics to study olfaction at the University of Hertfordshire in England. Schmuker was not involved in the study, which he describes as “a real breakthrough.” He and others who study our sense of smell say that the reported structure represents a step toward better understanding how the nose and brain jointly wring from airborne chemicals the sensations that warn of rotten food, evoke childhood memories, help us find mates and serve other crucial functions. The complexity of the chemistry that the nose detects has made olfaction particularly difficult to explain. Researchers think that human noses possess about 400 types of olfactory receptors, which are tasked with detecting a vastly larger number of odoriferous “volatiles,” molecules that vaporize readily, from the three-atom, rotten-egg-smelling hydrogen sulfide to the much larger, musky-scented muscone. (One recent estimate put the number of possible odor-bearing compounds at 40 billion or more.) == All Rights Reserved © 2023

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28766 - Posted: 05.03.2023

Sara Reardon Octopuses and squids both use the suckers on their limbs to grapple with their prey and to taste their quarry at the same time. Now, a pair of studies describes how these animals ‘taste by touching’ — and how evolution has equipped them with the perfect sensory ability for their lifestyles1,2. The papers were published in Nature on 12 April. The research details the structure of the receptors that stud the animals’ suckers. These receptors transmit information that enables the creature to taste chemicals on a surface independently from those floating in the water. Armed with brains Cephalopods — the group that includes octopuses and squids — have long fascinated neuroscientists because their brains and sensory systems are unlike those found in any other animals. Octopuses, for instance, have more neurons in their arms than in their central brain: a structure that allows each arm to function independently as if it has its own brain3. And researchers have long known that the hundreds of suckers on each arm can both feel the environment and taste it4. Molecular biologist Nicholas Bellono at Harvard University in Cambridge, Massachusetts, and his group were studying the California two-spot octopus (Octopus bimaculoides) when they came across a distinctive structure on the surface of the animal’s tentacle cells. Bellono suspected that this structure acted as a receptor for chemicals in the octopus’s environment. He contacted neurobiologist Ryan Hibbs at the University of California San Diego, who studies receptors that are architecturally similar to the octopus structures found by Bellono’s team: both types consist of five barrel-like proteins clustered to form a hollow tube. When the researchers looked at the octopus genome, they found 26 genes for these barrel-shaped proteins, which could be shuffled to create millions of distinct five-part combinations that detect various tastes1. The researchers found that the octopus receptors tend to bind to ‘greasy’ molecules that don’t dissolve in water, suggesting that they are optimized for detecting chemicals on surfaces such as a fish’s skin, the sea floor or the octopus’s own eggs. © 2023 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28741 - Posted: 04.15.2023

By Bethany Brookshire Cockroaches are changing up their sex lives, and it’s all our fault. Faced with sweet poisoned bait, roaches first ended up with a mutation that made them hate sweets, hindering their mating strategies. Now, more roach mutations are emerging, showing you can’t keep a good pest down. Like many animals, cockroaches have a sweet tooth, and that preference for sugar plays a central role in their reproductive activities. When a male roach targets a female roach, he will back up to her, secreting a solution called a nuptial gift from the tergal gland under his wings. The solution is full of proteins, fats and sugars, what some researchers call the chocolate of roach food. The female cockroach will crawl up on his back to take a sample, and while she is occupied, the male will whip out a hooked penis to latch onto her reproductive tract. They will then turn back to back and do the deed for about 90 minutes. Humans have aimed to exploit this love of sweet stuff to push cockroaches — particularly the German cockroaches that turn up in American homes — out of our spaces. For decades, people used poisoned roach baits baited with solutions containing glucose. Cockroaches took the bait. But some time in the late 20th century, a new mutation arose — glucose aversion. No one knows how many roaches now hate the sweet stuff, but Coby Schal, an evolutionary biologist at North Carolina State University, suspects the mutation is very common. “There are more and more papers being published on the fact that a whole suite of baits don’t work so well,” he said. This lack of a sweet tooth saved cockroaches from death, but it hurt their sex lives. The gift that normal males secrete contains maltose, a sugar that cockroach saliva transforms into glucose. But if females had the glucose averse mutation, they did not find the male secretions sexy and turned away before the male could hook on. © 2023 The New York Times Company

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28722 - Posted: 03.29.2023

Miryam Naddaf It is thanks to proteins in the nose called odour receptors that we find the smell of roses pleasant and that of rotting food foul. But little is known about how these receptors detect molecules and translate them into scents. Now, for the first time, researchers have mapped the precise 3D structure of a human odour receptor, taking a step forwards in understanding the most enigmatic of our senses. The study, published in Nature on 15 March1, describes an olfactory receptor called OR51E2 and shows how it ‘recognizes’ the smell of cheese through specific molecular interactions that switch the receptor on. “It’s basically our first picture of any odour molecule interacting with one of our odour receptors,” says study co-author Aashish Manglik, a pharmaceutical chemist at the University of California, San Francisco. Smell mystery The human genome contains genes encoding 400 olfactory receptors that can detect many odours. Mammalian odour-receptor genes were first discovered in rats by molecular biologist Richard Axel and biologist Linda Buck in 19912. Researchers in the 1920s estimated that the human nose could discern around 10,000 smells3, but a 2014 study suggests that we can distinguish more than one trillion scents4. Each olfactory receptor can interact with only a subset of smelly molecules called odorants — and a single odorant can activate multiple receptors. It is “like hitting a chord on a piano”, says Manglik. “Instead of hitting a single note, it’s a combination of keys that are hit that gives rise to the perception of a distinct odour.” Beyond this, little is known about exactly how olfactory receptors recognize specific odorants and encode different smells in the brain. Technical challenges in producing mammalian olfactory-receptor proteins using standard laboratory methods have made it difficult to study how these receptors bind to odorants. © 2023 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 5: The Sensorimotor System
Link ID: 28710 - Posted: 03.18.2023

By Dana Mackenzie On October 2, 2022, four days after Hurricane Ian hit Florida, a search-and-rescue Rottweiler named Ares was walking the ravaged streets of Fort Myers when the moment came that he had been training for. Ares picked up a scent within a smashed home and raced upstairs, with his handler trailing behind, picking his way gingerly through the debris. They found a man who had been trapped inside his bathroom for two days after the ceiling caved in. Some 152 people died in Ian, one of Florida’s worst hurricanes, but that lucky man survived thanks to Ares’ ability to follow a scent to its source. We often take for granted the ability of a dog to find a person buried under rubble, a moth to follow a scent plume to its mate or a mosquito to smell the carbon dioxide you exhale. Yet navigating by nose is more difficult than it might appear, and scientists are still working out how animals do it. “What makes it hard is that odors, unlike light and sound, don’t travel in a straight line,” says Gautam Reddy, a biological physicist at Harvard University who coauthored a survey of the way animals locate odor sources in the 2022 Annual Review of Condensed Matter Physics. You can see the problem by looking at a plume of cigarette smoke. At first it rises and travels in a more or less straight path, but very soon it starts to oscillate and finally it starts to tumble chaotically, in a process called turbulent flow. How could an animal follow such a convoluted route back to its origin? Over the last couple of decades, a suite of new high-tech tools, ranging from genetic modification to virtual reality to mathematical models, have made it possible to explore olfactory navigation in radically different ways. The strategies that animals use, as well as their success rates, turn out to depend on a variety of factors, including the animal’s body shape, its cognitive abilities and the amount of turbulence in the odor plume. One day, this growing understanding may help scientists develop robots that can accomplish tasks that we now depend on animals for: dogs to search for missing people, pigs to search for truffles and, sometimes, rats to search for land mines. © 2023 Annual Reviews

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28692 - Posted: 03.08.2023

By Erin Garcia de Jesús A female giraffe has a great Valentine’s Day gift for potential mates: urine. Distinctive anatomy helps male giraffes get a taste for whether a female is ready to mate, animal behaviorists Lynette and Benjamin Hart report January 19 in Animals. A pheromone-detecting organ in giraffes has a stronger connection to the mouth than the nose, the researchers found. That’s why males scope out which females to mate with by sticking their tongues in a urine stream. Animals such as male gazelles will lick fresh urine on the ground to track if females are ready to mate. But giraffes’ long necks and heavy heads make bending over to investigate urine on the ground an unstable and vulnerable position, says Lynette Hart, of the University of California, Davis. The researchers observed giraffes (Giraffa giraffa angolensis) in Etosha National Park in Namibia in 1994, 2002 and 2004. Bull giraffes nudged or kicked the female to ask her to pee. If she was a willing participant, she urinated for a few seconds, while the male took a sip. Then the male curled his lip and inhaled with his mouth, a behavior called a flehmen response, to pull the female’s scent into two openings on the roof of the mouth. From the mouth, the scent travels to the vomeronasal organ, or VNO, which detects pheromones. The Harts say they never saw a giraffe investigate urine on the ground. Unlike many other mammals, giraffes have a stronger oral connection — via a duct — to the VNO, than a nasal one, examinations of preserved giraffe specimens showed. One possible explanation for the difference could be that a VNO-nose link helps animals that breed at specific times of the year detect seasonal plants, says Benjamin Hart, a veterinarian also at the University of California, Davis. But giraffes can mate any time of year, so the nasal connection may not matter as much. © Society for Science & the Public 2000–2023.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 8: Hormones and Sex
Link ID: 28664 - Posted: 02.15.2023

By Chris Gorski At first glance, saliva seems like pretty boring stuff, merely a convenient way to moisten our food. But the reality is quite different, as scientists are beginning to understand. The fluid interacts with everything that enters the mouth, and even though it is 99 percent water, it has a profound influence on the flavors — and our enjoyment — of what we eat and drink. “It is a liquid, but it’s not just a liquid,” says oral biologist Guy Carpenter of King’s College London. Scientists have long understood some of saliva’s functions: It protects the teeth, makes speech easier and establishes a welcoming environment for foods to enter the mouth. But researchers are now finding that saliva is also a mediator and a translator, influencing how food moves through the mouth and how it sparks our senses. Emerging evidence suggests that interactions between saliva and food may even help to shape which foods we like to eat. The substance is not very salty, which allows people to taste the saltiness of a potato chip. It’s not very acidic, which is why a spritz of lemon can be so stimulating. The fluid’s water and salivary proteins lubricate each mouthful of food, and its enzymes such as amylase and lipase kickstart the process of digestion. This wetting also dissolves the chemical components of taste, or tastants, into saliva so they can travel to and interact with the taste buds. Through saliva, says Jianshe Chen, a food scientist at Zhejiang Gongshang University in Hangzhou, China, “we detect chemical information of food: the flavor, the taste.” © 2023 Annual Reviews

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28637 - Posted: 01.25.2023

Miryam Naddaf Researchers have made transgenic ants whose antennae glow green under a microscope, revealing how the insects’ brains process alarming smells. The findings identify three unique brain regions that respond to alarm signals. In these areas, called glomeruli, the ants’ nerve endings intersect. The work was posted on the bioRxiv preprint server on 29 December 20221 and has not yet been peer reviewed. “Ants are like little walking chemical factories,” says study co-author Daniel Kronauer, a biologist at the Rockefeller University in New York City. Previous research has focused on identifying the chemicals that ants release or analysing the insects’ behavioural responses to these odours, but “how ants can actually smell the pheromones is really only now becoming a little bit clearer”, says Kronauer. “This is the first time that, in a social insect, a particular glomerulus has been associated very strongly with a particular behaviour,” he adds. Smelly signals Ants are social animals that communicate with each other by releasing scented chemicals called pheromones. The clonal raider ants (Ooceraea biroi) that the researchers studied are blind. “They basically live in a world of smells,” says Kronauer. “So the vast amount of their social behaviour is regulated by these chemical compounds.” When an ant perceives danger, it releases alarm pheromones from a gland in its head to warn its nestmates. Other ants respond to this signal by picking up their larvae and evacuating the nest. “Instead of having dedicated brain areas for face recognition or language processing, ants have a massively expanded olfactory system,” says Kronauer. The researchers created transgenic clonal raider ants by injecting the insects’ eggs with a vector carrying a gene for a green fluorescent protein combined with one that expresses a molecule that indicates calcium activity in the brain. © 2023 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28632 - Posted: 01.18.2023

By Kelsey Ables Persistent loss of smell has left some covid-19 survivors yearning for the scent of their freshly bathed child or a waft of their once-favorite meal. It’s left others inured to the stink of garbage and accidentally drinking spoiled milk. “Anosmia,” as experts call it, is one of long covid’s strangest symptoms — and researchers may be one step closer to figuring it out what causes it and how to fix it. A small study published online on Wednesday in Science Translational Medicine and led by researchers at Duke University, Harvard and the University of California San Diego offers a theory, and new insight, into lingering smell loss. Scientists analyzed samples of olfactory epithelial tissue — where smell cells live — from 24 biopsies, nine of which were from post-covid patients struggling with persistent loss of smell. Although the sample was small, the results suggest that the sensory deficit is linked to an ongoing immune attack on cells responsible for smell — which endures even after the virus is gone — and a decline in the number of olfactory nerve cells. Bradley Goldstein, associate professor in Duke’s Department of Head and Neck Surgery and Communication Sciences and the Department of Neurobiology, an author on the paper, called the results “striking” and said in a statement, “It’s almost resembling a sort of autoimmune-like process in the nose.” While there has been research that looks at short-term smell loss and uses animal models, the new study is notable because it focuses on persistent smell loss and uses high-tech molecular analysis on human tissue. The study reflects enduring interest in the mysterious symptom. In July, researchers estimated that at least 5.6 percent of covid-19 patients develop chronic smell problems. That study, published in the peer-reviewed medical trade publication BMJ, also suggested that women as well as those who had more severe initial dysfunction were less likely to recover their sense of smell. Seniors are also especially vulnerable, The Post has reported.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28613 - Posted: 12.28.2022

By Diana Kwon A Scottish woman named Joy Milne made headlines in 2015 for an unusual talent: her ability to sniff out people afflicted with Parkinson’s disease, a progressive neurodegenerative illness that is estimated to affect nearly a million people in the U.S. alone. Since then a group of scientists in the U.K. has been working with Milne to pinpoint the molecules that give Parkinson’s its distinct olfactory signature. The team has now zeroed in on a set of molecules specific to the disease—and has created a simple skin-swab-based test to detect them. Milne, a 72-year-old retired nurse from Perth, Scotland, has hereditary hyperosmia, a condition that endows people with a hypersensitivity to smell. She discovered that she could sense Parkinson’s with her nose after noticing her late husband, Les, was emitting a musky odor that she had not detected before. Eventually, she linked this change in scent to Parkinson’s when he was diagnosed with the disease many years later. Les passed away in 2015. In 2012 Milne met Tilo Kunath, a neuroscientist at the University of Edinburgh in Scotland, at an event organized by the research and support charity Parkinson’s UK. Although skeptical at first, Kunath and his colleagues decided to put Milne’s claims to the test. They gave her 12 T-shirts, six from people with Parkinson’s and six from healthy individuals. She correctly identified the disease in all six cases—and the one T-shirt from a healthy person she categorized as having Parkinson’s belonged to someone who went on to be diagnosed with the disease less than a year later. Advertisement Subsequently, Kunath, along with chemist Perdita Barran of the University of Manchester in England and her colleagues, has been searching for the molecules responsible for the change in smell that Milne can detect. The researchers used mass spectrometry to identify types and quantities of molecules in a sample of sebum, an oily substance found on the skin’s surface. They discovered changes to fatty molecules known as lipids in people with Parkinson’s. © 2022 Scientific American

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 5: The Sensorimotor System
Link ID: 28510 - Posted: 10.13.2022

By Erin Garcia de Jesús Some mosquitoes have a near-foolproof thirst for human blood. Previous attempts to prevent the insects from tracking people down by blocking part of mosquitoes’ ability to smell have failed. A new study hints it’s because the bloodsuckers have built-in workarounds to ensure they can always smell us. For most animals, individual nerve cells in the olfactory system can detect just one type of odor. But Aedes aegypti mosquitoes’ nerve cells can each detect many smells, researchers report August 18 in Cell. That means if a cell were to lose the ability to detect one human odor, it still can pick up on other scents. The study provides the most detailed map yet of a mosquito’s sense of smell and suggests that concealing human aromas from the insects could be more complicated than researchers thought. Repellents that block mosquitoes from detecting human-associated scents could be especially tricky to make. “Maybe instead of trying to mask them from finding us, it would be better to find odorants that mosquitoes don’t like to smell,” says Anandasankar Ray, a neuroscientist at the University of California, Riverside who was not involved in the work. Such repellents may confuse or irritate the bloodsuckers and send them flying away (SN: 9/21/11; SN: 3/4/21). Effective repellents are a key tool to prevent mosquitoes from transmitting disease-causing viruses such as dengue and Zika (SN: 7/11/22). “Mosquitoes are responsible for more human deaths than any other creature,” says Olivia Goldman, a neurobiologist at Rockefeller University in New York City. “The better we understand them, the better that we can have these interventions.” © Society for Science & the Public 2000–2022.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28439 - Posted: 08.20.2022

By Stephanie Pappas As familiar to everyone as the COVID-causing coronavirus SARS-CoV-2 has become over the past two years, feverish research is still trying to parse a lingering puzzle. How, in fact, does the pandemic virus that has so changed the world cross over into the brain after entering the respiratory system? An answer is important because neurological complaints are some of the most common in the constellation of symptoms called long COVID. The mystery centers around the fact that brain cells don’t display the receptors, or docking sites, that the virus uses to get into nasal and lung cells. SARS-CoV-2, though, may have come up with an ingenious work-around. It may completely do away with the molecular maneuverings needed to attach to and unlock a cell membrane. Instead it wields a blunt instrument in the form of nanotube “bridges”—cylinders constructed of the common protein actin that are no more than a few tens of nanometers in diameter. These tunneling nanotubes extend across cell-to-cell gaps to penetrate a neighbor and give viral particles a direct route into COVID-impervious tissue. Researchers at the Pasteur Institute in Paris demonstrated the prospects for a nanotube-mediated cell crossing in a study in a lab dish that now needs to be confirmed in infected human patients. Given further proof, the findings could explain why some people who get COVID-19 experience brain fog and other neurological symptoms. Also, if the intercellular conduits could be severed, that might prevent some of these debilitating aftereffects of infection. The nanotube route “is a shortcut that propagates infection fast and between different organs, permissive or not permissive, to the infection,” says Chiara Zurzolo, a cell biologist at the Pasteur Institute, who conducted the study. “And it might be also a way for the virus to hide and escape the immune response.” © 2022 Scientific American

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28407 - Posted: 07.23.2022

By Laura Sanders A dog’s brain is wired for smell. Now, a new map shows just how extensive that wiring is. Powerful nerve connections link the dog nose to wide swaths of the brain, researchers report July 11 in the Journal of Neuroscience. One of these canine connections, a hefty link between areas that handle smell and vision, hasn’t been seen before in any species, including humans. The results offer a first-of-its-kind anatomical description of how dogs “see” the world with their noses. The new brain map is “awesome, foundational work,” says Eileen Jenkins, a retired army veterinarian and expert on working dogs. “To say that they have all these same connections that we have in humans, and then some more, it’s going to revolutionize how we understand cognition in dogs.” In some ways, the results aren’t surprising, says Pip Johnson, a veterinary radiologist and neuroimaging expert at Cornell University College of Veterinary Medicine. Dogs are superb sniffers. Their noses hold between 200 million and 1 billion odor molecule sensors, compared with the 5 million receptors estimated to dwell in a human nose. And dogs’ olfactory bulbs can be up to 30 times larger than people’s. But Johnson wanted to know how smell information wafts to brain regions beyond the obvious sniffing equipment. To build the map, Johnson and colleagues performed MRI scans on 20 mixed-breed dogs and three beagles. The subjects all had long noses and medium heads, and were all probably decent sniffers. Researchers then identified tracts of white matter fibers that carry signals between brain regions. A method called diffusion tensor imaging, which relies on the movement of water molecules along tissue, revealed the underlying tracts, which Johnson likens to the brain’s “road network.” © Society for Science & the Public 2000–2022.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28405 - Posted: 07.22.2022

By Veronique Greenwood Human beings maintain the polite fiction that we’re not constantly smelling one another. Despite our efforts to the contrary, we all have our own odors, pleasant and less so, and if we are like other land mammals, our particular perfume might mean something to our fellow humans. Some of these, like the reek of someone who hasn’t bathed all month, or the distinctive whiff of a toddler who is pretending they didn’t just fill their diaper, are self-explanatory. But scientists who study human olfaction, or your sense of smell, wonder if the molecules wafting off our skin may be registering at some subconscious level in the noses and brains of people around us. Are they bearing messages that we use in decisions without realizing it? Might they even be shaping whom we do and don’t like to spend time around? Indeed, in a small study published Wednesday in the journal Science Advances, researchers investigating pairs of friends whose friendship “clicked” from the beginning found intriguing evidence that each person’s body odor was closer to their friend’s than expected by chance. And when the researchers got pairs of strangers to play a game together, their body odors predicted whether they felt they had a good connection. There are many factors that shape whom people become friends with, including how, when or where we meet a new person. But perhaps one thing we pick up on, the researchers suggest, is how they smell. Scientists who study friendship have found that friends have more in common than strangers — not just things like age and hobbies, but also genetics, patterns of brain activity and appearance. Inbal Ravreby, a graduate student in the lab of Noam Sobel, an olfaction researcher at the Weizmann Institute of Science in Israel, was curious whether particularly swift friendships, the kind that seem to form in an instant, had an olfactory component — whether people might be picking up on similarities in their smells. © 2022 The New York Times Company

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 8: Hormones and Sex
Link ID: 28382 - Posted: 06.25.2022

Michael Marshall Researchers are finally making headway in understanding how the SARS-CoV-2 coronavirus causes loss of smell. And a multitude of potential treatments to tackle the condition are undergoing clinical trials, including steroids and blood plasma. Once a tell-tale sign of COVID-19, smell disruption is becoming less common as the virus evolves. “Our inboxes are not as flooded as they used to be,” says Valentina Parma, a psychologist at the Monell Chemical Senses Center in Philadelphia, Pennsylvania, who helped field desperate inquiries from patients throughout the first two years of the pandemic. A study published last month1 surveyed 616,318 people in the United States who have had COVID-19. It found that, compared with those who had been infected with the original virus, people who had contracted the Alpha variant — the first variant of concern to arise — were 50% as likely to have chemosensory disruption. This probability fell to 44% for the later Delta variant, and to 17% for the latest variant, Omicron. But the news is not all good: a significant portion of people infected early in the pandemic still experience chemosensory effects. A 2021 study2 followed 100 people who had had mild cases of COVID-19 and 100 people who repeatedly tested negative. More than a year after their infections, 46% of those who had had COVID-19 still had smell problems; by contrast, just 10% of the control group had developed some smell loss, but for other reasons. Furthermore, 7% of those who had been infected still had total smell loss, or ‘anosmia’, at the end of the year. Given that more than 500 million cases of COVID-19 have been confirmed worldwide, tens of millions of people probably have lingering smell problems. For these people, help can’t come soon enough. Simple activities such as tasting food or smelling flowers are now “really emotionally distressing”, Parma says. © 2022 Springer Nature Limited

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28374 - Posted: 06.15.2022

By Tina Hesman Saey Dogs are as reliable as laboratory tests for detecting COVID-19 cases, and may be even better than PCR tests for identifying infected people who don’t have symptoms. A bonus: The canines are cuter and less invasive than a swab up the nose. In a study involving sweat samples from 335 people, trained dogs sniffed out 97 percent of the coronavirus cases that had been identified by PCR tests, researchers report June 1 in PLOS One. And the dogs found all 31 COVID-19 cases among 192 people who didn’t have symptoms. These findings are evidence that dogs could be effective for mass screening efforts at places such as airports or concerts and may provide friendly alternatives for testing people who balk at nasal swabs, says Dominique Grandjean, a veterinarian at the National School of Veterinary Medicine of Alfort in Maisons-Alfort, France. “The dog doesn’t lie,” but there are many ways PCR tests can go wrong, Grandjean says. The canines’ noses also identified more COVID-19 cases than did antigen tests (SN: 12/17/21), similar to many at-home tests, but sometimes mistook another respiratory virus for the coronavirus, Grandjean and colleagues found. What’s more, anecdotal evidence suggests the dogs can pick up asymptomatic cases as much as 48 hours before people test positive by PCR, he says. In the study, dogs from French fire stations and from the Ministry of the Interior of the United Arab Emirates were trained in coronavirus detection by rewarding them with toys — usually tennis balls. “It’s playtime for them,” Grandjean says. It takes about three to six weeks, depending on the dog’s experience with odor detection, to train a dog to pick out COVID-19 cases from sweat samples. © Society for Science & the Public 2000–2022.

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28349 - Posted: 06.04.2022

Dustin Jones Researchers from Sweden and the United Kingdom teamed up to sniff out the answer to a question practically every person has pondered at one time or another: what is the best smell out there? They found that most people, despite coming from different cultures and backgrounds, find vanilla to be the most pleasant smell on the planet more often than not. Sour, stinky feet? Not so much. The collaborative study between Sweden's Karolinska Institutet and the University of Oxford found that people share similar preferences when it comes to smell, regardless of cultural background. And according to the results, vanilla is the most pleasing smell around, followed by ethyl butyrate, which smells like peaches. Artin Arshamian, researcher at Karolinska and one of the study's authors, said humans may have similar olfactory preferences because it helped early humans survive. Which may very well explain why stinky feet came in dead last as far as appealing odors are concerned. According to the study, the pleasantness of a smell can be attributed to the structure of an edible item's odor molecule 41% of the time. Simply put, humans likely enjoy many of the same smells, more often than not, because of a deep-rooted sense that an item is safe to eat. Sponsor Message "We wanted to examine if people around the world have the same smell perception and like the same types of [odor], or whether this is something that is culturally learned," Arshamian said. "Traditionally it has been seen as cultural, but we can show that culture has very little to do with it." © 2022 npr

Related chapters from BN: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 28268 - Posted: 04.06.2022