Links for Keyword: Chemical Senses (Smell & Taste)

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By Michelle Roberts Health editor, BBC News online A loss of smell or taste may be a sign that you have coronavirus, according to UK researchers. A team at King's College London looked at responses from more than 400,000 people reporting suspected Covid-19 symptoms to an app. But loss of smell and taste are also signs of other respiratory infections, such as the common cold. And experts say fever and cough remain the most important symptoms of the virus to look out for and act upon. If you or someone you live with has a new continuous cough or high temperature, the advice is stay at home to stop the risk of spreading coronavirus to others. Coronavirus: What should I do? What did the study find? The King's College researchers wanted to gather information on possible coronavirus symptoms to help experts better understand and fight the disease. Of those reporting one or more symptoms of coronavirus to the Covid Symptom Tracker app: 53% said they had fatigue or tiredness 29% persistent cough 28% shortness of breath 18% loss of sense of smell or taste 10.5% suffered from fever Of these 400,000 people, 1,702 said they had been tested for Covid-19, with 579 receiving a positive result and 1,123 a negative one. Among the ones who had coronavirus infection confirmed by a positive test, three-fifths (59%) reported loss of smell or taste. © 2020 BBC

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27157 - Posted: 04.01.2020

By Erin Garcia de Jesus Myriad microbes dwell on human tongues — and scientists have now gotten a glimpse at the neighborhoods that bacteria build for themselves. Bacteria grow in thick films, with different types of microbes clustered in patches around individual cells on the tongue’s surface, researchers report online March 24 in Cell Reports. This pattern suggests individual bacterial cells first attach to the tongue cell’s surface and then grow in layers as they form larger clusters — creating miniature environments the different species need to thrive. “It’s amazing, the complexity of the community that they build right there on your tongue,” says Jessica Mark Welch, a microbiologist at the Marine Biological Laboratory in Woods Hole, Mass. Methods to identify microbial communities typically hunt for genetic fingerprints from various types of bacteria (SN: 11/05/09). The techniques can reveal what lives on the tongue, but not how the bacterial community is organized in space, Mark Welch says. So she and her colleagues had people scrape the top of their tongues with plastic scrapers. Then the team tagged various types of bacteria in the tongue gunk with differently colored fluorescent markers to see how the microbial community was structured. Bacterial cells, largely grouped by type in a thick, densely packed biofilm, covered each tongue surface cell. While the overall patchwork appearance of the microbial community was consistent among cells from different samples and people, the specific composition of bacteria varied, Mark Welch says. © Society for Science & the Public 2000–2020.

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27141 - Posted: 03.25.2020

By Eva Frederick They’re the undertakers of the bee world: a class of workers that scours hives for dead comrades, finding them in the dark in as little as 30 minutes, despite the fact that the deceased haven’t begun to give off the typical odors of decay. A new study may reveal how they do it. “The task of undertaking is fascinating” and the new work is “pretty cool,” says Jenny Jandt, a behavioral ecologist at the University of Otago, Dunedin, who was not involved with the study. Wen Ping, an ecologist at the Chinese Academy of Sciences’s Xishuangbanna Tropical Botanical Garden, wondered whether a specific type of scent molecule might help undertaker bees find their fallen hive mates. Ants, bees, and other insects are covered in compounds called cuticular hydrocarbons (CHCs), which compose part of the waxy coating on their cuticles (the shiny parts of their exoskeletons) and help prevent them from drying out. While the insects are alive, these molecules are continually released into the air and are used to recognize fellow hive members. Wen speculated that less of the pheromones were being released into the air after a bee died and its body temperature decreased. When he used chemical methods of detecting gases to test this hypothesis, he confirmed that cooled dead bees were indeed emitting fewer volatile CHCs than living bees. © 2020 American Association for the Advancement of Science.

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 19: Language and Lateralization
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 15: Brain Asymmetry, Spatial Cognition, and Language
Link ID: 27138 - Posted: 03.24.2020

By Roni Caryn Rabin A mother who was infected with the coronavirus couldn’t smell her baby’s full diaper. Cooks who can usually name every spice in a restaurant dish can’t smell curry or garlic, and food tastes bland. Others say they can’t pick up the sweet scent of shampoo or the foul odor of kitty litter. Anosmia, the loss of sense of smell, and ageusia, an accompanying diminished sense of taste, have emerged as peculiar telltale signs of Covid-19, the disease caused by the coronavirus, and possible markers of infection. On Friday, British ear, nose and throat doctors, citing reports from colleagues around the world, called on adults who lose their senses of smell to isolate themselves for seven days, even if they have no other symptoms, to slow the disease’s spread. The published data is limited, but doctors are concerned enough to raise warnings. “We really want to raise awareness that this is a sign of infection and that anyone who develops loss of sense of smell should self-isolate,” Prof. Claire Hopkins, president of the British Rhinological Society, wrote in an email. “It could contribute to slowing transmission and save lives.” She and Nirmal Kumar, president of ENT UK, a group representing ear, nose and throat doctors in Britain, issued a joint statement urging health care workers to use personal protective equipment when treating any patients who have lost their senses of smell, and advised against performing nonessential sinus endoscopy procedures on anyone, because the virus replicates in the nose and the throat and an exam can prompt coughs or sneezes that expose the doctor to a high level of virus. Two ear, nose and throat specialists in Britain who have been infected with the coronavirus are in critical condition, Dr. Hopkins said. Earlier reports from Wuhan, China, where the coronavirus first emerged, had warned that ear, nose and throat specialists as well as eye doctors were infected and dying in large numbers, Dr. Hopkins said. © 2020 The New York Times Company

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27135 - Posted: 03.23.2020

Amy Schleunes Preti was a leading expert on human odors who sought to understand the chemistry of odor in the underarm and the behavior aspects of human scents, and an ambassador to patients suffering from rare metabolic diseases who provided communities worldwide with knowledge about their condition and how to cope with it. Preti was also dedicated to using odor biomarkers to detect cancer in its early stages, contributing both research and money to the cause, according to a Monell Center press release. Born on October 7, 1944 in Brooklyn, New York, Preti received a bachelor’s degree in chemistry from the Polytechnic Institute of Brooklyn in 1966. He then went on to MIT, where he earned a PhD in chemistry in 1971. His thesis was titled, “A Study of the Organic Compounds in the Lunar Crust and in Terrestrial Model Systems,” according to the Monell Center’s statement. Preti coauthored a paper published in Science on the same topic, and reportedly saved a vial of “moon dust” that he sometimes showed off to visitors to his lab. Upon completing his doctorate in 1971, he immediately accepted a postdoc at Monell and later become a member of the Monell Chemical Senses Center and an adjunct professor at the University of Pennsylvania School of Medicine. While Preti and his colleagues investigated a range of odors in different species—anal sac emissions from dogs, scent marks by marmoset monkeys, urine from guinea pigs and mice—Preti’s main focus was on the meaning of human odors. He studied the scents of human underarms and melanoma cells as well as the odors associated with generalized stress. Along with his collaborator, Charles Wysocki, Preti published papers on how human physiology and behavior are affected by body odor. Preti was skeptical of human pheromones and their associated hype, telling The Scientist in 2018, “I am not compelled by any studies that are out there that say there is an active steroid component from the underarm that causes [sexual attraction].” © 1986–2020 The Scientist

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27133 - Posted: 03.23.2020

By Maria Temming When it comes to identifying scents, a “neuromorphic” artificial intelligence beats other AI by more than a nose. The new AI learns to recognize smells more efficiently and reliably than other algorithms. And unlike other AI, this system can keep learning new aromas without forgetting others, researchers report online March 16 in Nature Machine Intelligence. The key to the program’s success is its neuromorphic structure, which resembles the neural circuitry in mammalian brains more than other AI designs. This kind of algorithm, which excels at detecting faint signals amidst background noise and continually learning on the job, could someday be used for air quality monitoring, toxic waste detection or medical diagnoses. The new AI is an artificial neural network, composed of many computing elements that mimic nerve cells to process scent information (SN: 5/2/19). The AI “sniffs” by taking in electrical voltage readouts from chemical sensors in a wind tunnel that were exposed to plumes of different scents, such as methane or ammonia. When the AI whiffs a new smell, that triggers a cascade of electrical activity among its nerve cells, or neurons, which the system remembers and can recognize in the future. Like the olfactory system in the mammal brain, some of the AI’s neurons are designed to react to chemical sensor inputs by emitting differently timed pulses. Other neurons learn to recognize patterns in those blips that make up the odor’s electrical signature. © Society for Science & the Public 2000–2020

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27126 - Posted: 03.17.2020

By Jonathan Lambert To a sea turtle, plastic debris might smell like dinner. As the plastic detritus of modern human life washes into oceans, marine creatures of all kinds interact with and sometimes eat it (SN: 11/13/19). Recent research suggests that this is no accident. Plastic that’s been stewing in the ocean emits a chemical that, to some seabirds and fish, smells a lot like food (SN: 11/9/16). That chemical gas, dimethyl sulfide, is also produced by phytoplankton, a key food source for many marine animals. Now, scientists have determined that loggerhead sea turtles may also confuse the smell of plastic with food, according to a study published March 9 in Current Biology. Over two weeks in January 2019, 15 captive loggerheads in tanks were exposed at the water surface to a slew of scents, including the largely neutral scent of water as a control, of food such as shrimp and of new and ocean-soaked plastic. The turtles (Caretta caretta) largely ignored smells of water and clean plastic. But when the scientists puffed air containing scents of either food or ocean-stewed plastic, the reptiles increased their sniffing above water — a typical foraging behavior. In fact, those responses to food and ocean-soaked plastic were indistinguishable to the researchers, suggesting that the plastic can induce foraging behavior in sea turtles, the team says. That might explain why sea turtles get entangled in or eat plastic, which can be harmful. Along with previous research, this study expands the breadth of marine life that may confuse plastic with food. © Society for Science & the Public 2000–2020

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 27111 - Posted: 03.12.2020

By Virginia Morell Dogs’ noses just got a bit more amazing. Not only are they up to 100 million times more sensitive than ours, they can sense weak thermal radiation—the body heat of mammalian prey, a new study reveals. The find helps explain how canines with impaired sight, hearing, or smell can still hunt successfully. “It’s a fascinating discovery,” says Marc Bekoff, an ethologist, expert on canine sniffing, and professor emeritus at the University of Colorado, Boulder, who was not involved in the study. “[It] provides yet another window into the sensory worlds of dogs' highly evolved cold noses.” The ability to sense weak, radiating heat is known in only a handful of animals: Black fire beetles, certain snakes, and one species of mammal, the common vampire bat, all of which use it to hunt prey. Most mammals have naked, smooth skin on the tip of their noses around the nostrils, an area called the rhinarium. But dogs’ rhinaria are moist, colder than the ambient temperature, and richly endowed with nerves—all of which suggests an ability to detect not just smell, but heat. To test the idea, researchers at Lund University in Sweden and Eotvos Lorand University in Hungary trained three pet dogs to choose between a warm (31 C degrees) and an ambient-temperature object, each placed 1.6 meters away. The dogs weren’t able to see or smell the difference between these objects. (Scientists could only detect the difference by touching the surfaces.) After training, the dogs were tested on their skill in double-blind experiments; all three successfully detected the objects emitting weak thermal radiation, the scientists reveal today in Scientific Reports. © 2020 American Association for the Advancement of Science

Related chapters from BN8e: 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: 27081 - Posted: 02.28.2020

John Henning Schumann As the owner of a yellow lab named Gus, author Maria Goodavage has had many occasions to bathe her pooch when he rolls around in smelly muck at the park. Nevertheless, her appreciation for his keen sense of smell has inspired her write best-selling books about dogs with special assignments in the military and the U.S. Secret Service. Her latest, Doctor Dogs: How Our Best Friends Are Becoming Our Best Medicine, highlights a vast array of special medical tasks that dogs can perform — from the laboratory to the bedside, and everywhere else a dog can tag along and sniff. Canines' incredible olfactory capacity — they can sniff in parts per trillion — primes them to detect disease, and their genius for observing our behavior helps them guide us physically and emotionally. Goodavage spoke with NPR contributor John Henning Schumann, a doctor and host of Public Radio Tulsa's #MedicalMonday about what she has learned about dogs in medicine What led you to look into dogs in medicine? I've been reading and writing about military dogs and Secret Service dogs for many years now, and it was sort of a natural next step. These are dogs on the cutting edge of medicine. They're either working in research or right beside someone to save their life every day. And really, doctor dogs are, for the most part, using their incredible sense of smell to detect diseases. And if they're paired with a person, they bond with that person to tell them something that will save their life. © 2020 npr

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26992 - Posted: 01.25.2020

By Tina Hesman Saey Some hairy cells in the nose may trigger sneezing and allergies to dust mites, mold and other substances, new work with mice suggests. When exposed to allergens, these “brush cells” make chemicals that lead to inflammation, researchers report January 17 in Science Immunology. Only immune cells previously were thought to make such inflammatory chemicals — fatty compounds known as lipids. The findings may provide new clues about how people develop allergies. Brush cells are shaped like teardrops topped by tufts of hairlike projections. In people, mice and other animals, these cells are also found in the linings of the trachea and the intestines, where they are known as tuft cells (SN: 4/13/18). However, brush cells are far more common in the nose than in other tissues, and may help the body identify when pathogens or noxious chemicals have been inhaled, says Lora Bankova, an allergist and immunologist at Brigham and Women’s Hospital in Boston. Bankova and her colleagues discovered that, when exposed to certain molds or dust mite proteins, brush cells in mice’s noses churn out inflammation-producing lipids, called cysteinyl leukotrienes. The cells also made the lipids when encountering ATP, a chemical used by cells for energy that also signals when nearby cells are damaged, as in an infection. Mice exposed to allergens or ATP developed swelling of their nasal tissues. But mice that lacked brush cells suffered much less inflammation. Such inflammation may lead to allergies in some cases. The researchers haven’t yet confirmed that brush cells in human noses respond to allergens in the same way as these cells do in mice. © Society for Science & the Public 2000–2020

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 11: Emotions, Aggression, and Stress
Link ID: 26974 - Posted: 01.21.2020

By Neuroskeptic | Many people may be living life without a particular brain region – and not suffering any ill-effects. In a new paper in Neuron, neuroscientists Tali Weiss and colleagues discuss five women who appear to completely lack olfactory bulbs (OB). According to most neuroscience textbooks, no OB should mean no sense of smell, because the OB is believed to be a key relay point for olfactory signals. As Wikipedia puts it: The olfactory bulb transmits smell information from the nose to the brain, and is thus necessary for a proper sense of smell. Scent molecules activate olfactory receptors and signals travel up the olfactory nerves to the olfactory bulb, and then on to the rest of the brain via the olfactory tract. From Wikipedia. However, remarkably, Weiss et al.’s five women seem to have entirely normal sense of smell despite lacking any visible OBs on brain MRI scans. On both subjective and objective measures of olfactory function, these women showed no abnormalities. MRIs showing normal development of olfactory bulbs (A) compared to two women with no visible olfactory bulbs but normal sense of smell (B) & (D) and one woman with no sense of smell (C). From Weiss et al. Fig 1 Weiss et al. came across two of the women serendipitously while carrying out MRI scans for an unrelated project. The other 3 were found among healthy controls in the Human Connectome Project MRI dataset.

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26825 - Posted: 11.18.2019

Hate eating certain vegetables? It could be down to your genes, say US scientists who have done some new research. Inheriting two copies of the unpleasant taste gene provides a "ruin-your-day level of bitterness" to foods like broccoli and sprouts, they say. It could explain why some people find it difficult to include enough vegetables in their diet, they suggest. The gene may also make beer, coffee and dark chocolate taste unpleasant. In evolutionary terms, being sensitive to bitter taste may be beneficial - protecting humans from eating things that could be poisonous. But Dr Jennifer Smith and colleagues from the University of Kentucky School of Medicine say it can also mean some people struggle to eat their recommended five-a-day of fresh fruit and veg. Everyone inherits two copies of a taste gene called TAS2R38. It encodes for a protein in the taste receptors on the tongue which allows us to taste bitterness. People who inherit two copies of a variant of the gene TAS2R38, called AVI, are not sensitive to bitter tastes from certain chemicals. Those with one copy of AVI and another called PAV perceive bitter tastes of these chemicals, but not to such an extreme degree as individuals with two copies of PAV, often called "super-tasters", who find the same foods exceptionally bitter. The scientists studied 175 people and found those with two copies of the bitter taste PAV version of the gene ate only small amounts of leafy green vegetables, which are good for the heart. Dr Smith told medics at a meeting of the American Heart Association: "You have to consider how things taste if you really want your patient to follow nutrition guidelines." © 2019 BBC.

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26814 - Posted: 11.12.2019

By Veronique Greenwood When a bird preens its feathers, it uses a little of nature’s own pomade: an oil made by glands just above the tail. This oil helps clean and protect the bird’s plumage, but also contains a delicate bouquet of scents. To other birds — potential mates or would-be rivals — these smells carry many messages, not unlike the birdsongs and fancy feathers that are more obvious to human observers. These scents may signal that a bird would be dangerous to encounter or might be ready to mate, or any number of other cues. However, new research using dark-eyed juncos, a common North American bird, suggests that these odoriferous messages may not be entirely of the bird’s own making. In a study published last month in the Journal of Experimental Biology, biologists reported that microbes living peacefully on the birds’ oil glands may play an important role in making the scent molecules involved. That implies that the birds’ microbiomes may influence both the smell and the behavior it provokes in other birds. Birds’ scented messages are the focus of the research of Danielle Whittaker, managing director of the Beacon Center for the Study of Evolution in Action at Michigan State University and an author of the paper. Some years ago, after she gave a talk, Kevin Theis, a colleague who studied scent-producing bacteria living on hyenas and who is a co-author of the new paper, asked her whether she had ever looked at the birds’ microbes. “I had never thought about bacteria at all,” said Dr. Whittaker. “But all the compounds I was describing were known byproducts of bacterial metabolism.” Dr. Whittaker took samples of bacteria living on the oil glands of 10 captive dark-eyed juncos and then injected the glands with an antibiotic. When she compared the microbes before and after the treatment, the results seemed to show that two groups of bacteria in particular had taken a hit from the treatment. Furthermore, when she compared the scent molecules in the oil before and after the treatment, there were significant differences. © 2019 The New York Times Company

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 26812 - Posted: 11.11.2019

By Sofie Bates Some people may be able to smell even without key structures that relay odor information from the nose to the brain. Researchers used brain scans to identify two women who appear to be missing their olfactory bulbs, the only parts of the brain known to receive signals about smell sensations from the nose and send them to other parts of the brain for processing. Both individuals performed similarly to other women with olfactory bulbs on several tests to identify and differentiate odors, the scientists report November 6 in Neuron. The findings challenge conventional views of the olfactory system, and may lead to treatments for people with no sense of smell (SN: 7/2/07). “I’m not sure that our textbook view of how the [olfactory] system works is right,” says Noam Sobel, a neuroscientist at the Weizmann Institute of Science in Rehovot, Israel. MRI scans of the women’s brains revealed that where most people have two olfactory bulbs, these two appeared to have cerebrospinal fluid instead. To the researchers, this indicated that the women didn’t have olfactory bulbs. But Jay Gottfried, a neuroscientist at the University of Pennsylvania who was not involved in the study, says “I am not convinced that the women are indeed missing their bulbs.” Some evidence for olfactory bulbs may be undetectable with MRI, like microscopic structures or olfactory tissue that could be found with antibodies, he says. © Society for Science & the Public 2000–2019

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26800 - Posted: 11.07.2019

By Shraddha Chakradhar, Rockefeller University neuroscientist Vanessa Ruta was just named a member of the latest class of MacArthur “Genius” grant winners. The fellowship offers a five-year grant of $625,000 to individuals “who show exceptional creativity in their work and the prospect for still more in the future,” according to the MacArthur Foundation. Fortuitously, or perhaps by design, creativity has been a guiding principle for Ruta, 45, and her work. Both her parents were visual artists, and Ruta herself grew up as a ballet dancer—and at one point considered it a career path. After making the switch to science, however, she says that creativity—and the freedom that comes with it—still plays a big part in how she goes about her work. Her research now involves better understanding how the nervous system takes in external cues such as smell and processes these stimuli to inspire various behaviors. Advertisement STAT spoke with Ruta to learn more about her life and work. This interview has been lightly edited and condensed. Both your parents were artists. Did they influence how you work? I was strongly influenced by their creative process, which is parallel to how scientists work. There’s a kind of honing in your craft. It’s obvious in the artistic endeavors, whether it’s practicing dancing or something else. But it’s also there in the sciences—you have to be disciplined about pushing through with your experiments. © 2019 Scientific American

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26654 - Posted: 09.28.2019

Emily Makowski When we eat sour food, we instantaneously react due to a taste-sensing circuit between the tongue and the brain. Two papers published today (September 19)—one in Cell and the other in Current Biology—show that the otopetrin-1 proton channel in the tongue’s sour taste receptors is one of the components responsible for sour taste sensing in mice. These findings add to the body of sour taste research “from the molecular level, of how these protons are transported, up to the level of how the mice are able to taste it,” says Lucie Delemotte, a computational biophysicist at KTH Royal Institute of Technology who was not involved with either study. On the tongue, each taste bud contains a cluster of taste receptor cells innervated by a gustatory nerve network. The tips of these cells have a variety of taste molecule-capturing proteins and, in the case of sour detection, proteins that are called proton channels that sense pH. A team led by Charles Zuker at Columbia University Medical Center identified a potential sour taste receptor for the first time in 2006, and he and other researchers have continued to work on clarifying the mechanics and function of that receptor along with other possible sour taste receptors. A breakthrough occurred last year when Emily Liman of the University of Southern California’s lab discovered that otopetrin-1 (also referred to as OTOP1) was a proton channel also implicated in detecting sour tastes. But the researchers stopped short of demonstrating that OTOP1 was required for sour taste sensing in an actual animal—until now. © 1986–2019 The Scientist

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26631 - Posted: 09.21.2019

By Ryan P. Dalton Subject cDa29—well-known yet anonymous—resides somewhere in the north of England. You can almost see it: the peat stacks and old textile mills; the limestone and turf ruins where, on divine calling, Hadrian marked the northernmost reach of the Roman Empire. But even were you there, you wouldn’t see it the way cDa29 does. That’s because cDa29 is tetrachromatic: while most people see their world as a mix of three colors—red, green and blue—cDa29 sees hers in four. Difficult to imagine as that world may be for trichromats, your sense of smell provides access to an even richer world, one painted not in four colors but 400. You can almost smell it: the peat, the mills, the turf. How do your senses build these worlds? They begin with sensory “receptors,” which sit on the surfaces of cells and are activated by specific stimuli. In the case of vision, there are three color photoreceptors in your retina—activated by red, green or blue light. By keeping these receptors separated—such that no two photoreceptors occur together in one cell—your retina can keep track of what colors came from where. As a counterexample, you have a few dozen “bitter receptors” on your tongue, but each bitter taste cell contains several of them. This arrangement allows you to detect many different bitter compounds, but it does not help you distinguish between them. As these examples illustrate, you must both be able to detect a wide range of stimuli and to discriminate between those stimuli—and generally, your senses strike a balance between these two objectives. Ever the romantic, your sense of smell casts aside the suggestion of balance and optimizes for both detection and discrimination. Olfactory neurons in your nose have evolved some 400 odor receptors, and each neuron contains only one. Receptors are tuned to detect a few basic odors apiece: some detect geranium petals or pine needles, while others detect the by-products of putrefaction. To organize all this information, your olfactory neurons wire into an “olfactory map” on your brain’s olfactory bulb. Olfactory neurons are one of the few types of neurons that are born throughout your life, and each of the roughly 10,000 such neurons born each day in your nose subsequently wires into the olfactory map in your brain. © 2019 Scientific American

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26492 - Posted: 08.13.2019

Sacha Pfeiffer There's a new smell tingling tourists' noses in the Big Apple, far above the trash bag-lined sidewalks — and this scent is by design. Atop One World Trade Center, New York City's tallest building, a fragrance carrying hints of citrus, beech trees and red maples wafts through the glass-enclosed observatory deck. When the observatory commissioned the custom scent to diffuse through the floor's HVAC system, Managing Director Keith Douglas told the New York Times that he wanted it to elicit a "positive thought," and offer a "a subtle complement to the experience" of visiting the space. But not everyone is keen on the scent. One tourist described the smell as "sickly," according to the Times, which first documented the new aromatic experience in lower Manhattan. It's a marketing strategy businesses are increasingly deploying to lure customers into stores and entice them to stay longer. The smell of cinnamon fills Yankee Candle stores, Subway pumps a doughy bread scent through its vents. International Flavors & Fragrances, the same company that developed clothing chain Abercrombie & Fitch's notoriously pungent "Fierce" cologne, known to linger on clothes long after their purchase, designed One World's scent. "The quickest way to change somebody's mood or behavior is with smell," says Dr. Alan Hirsch, neurological director of the Smell and Taste Treatment and Research Foundation in Chicago. © 2019 npr

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 11: Emotions, Aggression, and Stress
Link ID: 26487 - Posted: 08.12.2019

By Virginia Morell Most of us can look at two meal plates and easily tell which one has more food on it. But if someone turns out the lights, we’re out of luck. Not so for Asian elephants. A new study reveals that the pachyderms can judge food quantity merely by using their sense of smell, the first time an animal has been shown to do this. To conduct the research, scientists presented six Asian elephants (Elephas maximus) at an educational sanctuary in Thailand with two opaque, locked buckets containing 11 different ratios of sunflower seeds, a favorite treat. The elephants could not see how many seeds each bucket contained, but they could smell the contents through small holes in the lids. The animals chose the bucket with the greater quantity of food 59% to 82% of the time, the team reports today in the Proceedings of the National Academy of Sciences. (Even dogs, with their famed sense of smell, fail this test, other research has shown.) The discovery makes sense, the scientists say, because elephants are known to have the highest number of genes associated with olfactory reception of any species (about 2000 versus dogs’ 811). They can distinguish between the scent of Maasai pastoralists and Kamba farmers, and rely on their sense of smell to navigate long distances to find food and water (up to 19.2 kilometers). The researchers hope their findings could help mitigate human-elephant conflicts in Asia and Africa, because wandering herds use odors to decide where to travel; enticing scents might help lure them away from agricultural fields, for instance. © 2019 American Association for the Advancement of Science

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 26293 - Posted: 06.04.2019

Kerry Grens In mice whose sense of smell has been disabled, a squirt of stem cells into the nose can restore olfaction, researchers report today (May 30) in Stem Cell Reports. The introduced “globose basal cells,” which are precursors to smell-sensing neurons, engrafted in the nose, matured into nerve cells, and sent axons to the mice’s olfactory bulbs in the brain. “We were a bit surprised to find that cells could engraft fairly robustly with a simple nose drop delivery,” senior author Bradley Goldstein of the University of Miami Miller School of Medicine says in a press release. “To be potentially useful in humans, the main hurdle would be to identify a source of cells capable of engrafting, differentiating into olfactory neurons, and properly connecting to the olfactory bulbs of the brain. Further, one would need to define what clinical situations might be appropriate, rather than the animal model of acute olfactory injury.” Goldstein and others have independently tried stem cell therapies to restore olfaction in animals previously, but he and his coauthors note in their study that it’s been difficult to determine whether the regained function came from the transplant or from endogenous repair stimulated by the experimental injury to induce a loss of olfaction. So his team developed a mouse whose resident globose basal cells only made nonfunctional neurons, and any restoration of smell would be attributed to the introduced cells. © 1986–2019 The Scientist

Related chapters from BN8e: Chapter 9: Hearing, Balance, Taste, and Smell; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 13: Memory, Learning, and Development
Link ID: 26285 - Posted: 06.01.2019