Links for Keyword: Chemical Senses (Smell & Taste)

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By Virginia Morell Dogs, most of us think, have the best noses on the planet. But a new study reveals that this honor actually goes to elephants. The power of a mammal’s sniffer hinges on the number and type of its olfactory receptor genes. These genes are expressed in sensory cells that line the nasal cavity and are specialized for detecting odor molecules. When triggered, they set off a cascade of signals from the nose to the brain, enabling an animal to identify a particular smell. In the new study, scientists identified and examined olfactory receptor genes from 13 mammalian species. The researchers found that every species has a highly unique variety of such genes: Of the 10,000 functioning olfactory receptor genes the team studied, only three are shared among the 13 species. Perhaps not surprisingly, given the length of its trunk, the African elephant has the largest number of such genes—nearly 2000, the scientists report online today in the Genome Research. In contrast, dogs have only 1000, and humans and chimpanzees, less than 400—possibly because higher primates rely more on their vision and less on their sense of smell. The discovery fits with another recent study showing that Asian elephants are as good as mice (which have nearly 1300 olfactory receptor genes) at discriminating between odors; dogs and elephants have yet to be put to a nose-to-trunk sniffer test. Other research has also shown just how important a superior sense of smell is to the behemoths. A slight whiff is all that’s necessary, for instance, for elephants, such as those in the photo above, to distinguish between two Kenyan ethnic groups—the Maasai, who sometimes spear them, and the Kamba, who rarely pose a threat. They can also recognize as many as 30 different family members from cues in their urine. © 2014 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19868 - Posted: 07.23.2014

By PETER ANDREY SMITH Sweet, salty, sour and bitter — every schoolchild knows these are the building blocks of taste. Our delight in every scrumptious bonbon, every sizzling hot dog, derives in part from the tongue’s ability to recognize and signal just four types of taste. But are there really just four? Over the last decade, research challenging the notion has been piling up. Today, savory, also called umami, is widely recognized as a basic taste, the fifth. And now other candidates, perhaps as many as 10 or 20, are jockeying for entry into this exclusive club. “What started off as a challenge to the pantheon of basic tastes has now opened up, so that the whole question is whether taste is even limited to a very small number of primaries,” said Richard D. Mattes, a professor of nutrition science at Purdue University. Taste plays an intrinsic role as a chemical-sensing system for helping us find what is nutritious (stimulatory) and as a defense against what is poison (aversive). When we put food in our mouths, chemicals slip over taste buds planted into the tongue and palate. As they respond, we are thrilled or repulsed by what we’re eating. But the body’s reaction may not always be a conscious one. In the late 1980s, in a windowless laboratory at Brooklyn College, the psychologist Anthony Sclafani was investigating the attractive power of sweets. His lab rats loved Polycose, a maltodextrin powder, even preferring it to sugar. That was puzzling for two reasons: Maltodextrin is rarely found in plants that rats might feed on naturally, and when human subjects tried it, the stuff had no obvious taste. More than a decade later, a team of exercise scientists discovered that maltodextrin improved athletic performance — even when the tasteless additive was swished around in the mouth and spit back out. Our tongues report nothing; our brains, it seems, sense the incoming energy. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19867 - Posted: 07.22.2014

|By Roni Jacobson Last week, nine-year-old Hally Yust died after contracting a rare brain-eating amoeba infection while swimming near her family’s home in Kansas. The organism responsible, Naegleria fowleri, dwells in warm freshwater lakes and rivers and usually targets children and young adults. Once in the brain it causes a swelling called primary meningoencephalitis. The infection is almost universally fatal: it kills more than 97 percent of its victims within days. Although deadly, infections are exceedingly uncommon—there were only 34 reported in the U.S. during the past 10 years—but evidence suggests they may be increasing. Prior to 2010 more than half of cases came from Florida, Texas and other southern states. Since then, however, infections have popped up as far north as Minnesota. “We’re seeing it in states where we hadn’t seen cases before,” says Jennifer Cope, an epidemiologist and expert in amoeba infections at the U.S. Centers for Disease Control and Prevention. The expanding range of Naegleria infections could potentially be related to climate change, she adds, as the organism thrives in warmer temperatures. “It’s something we’re definitely keeping an eye on.” Still, “when it comes to Naegleria there’s a lot we don’t know,” Cope says—including why it chooses its victims. The amoeba has strategies to evade the immune system, and treatment options are meager partly because of how fast the infection progresses. But research suggests that the infectioncan be stopped if it is caught soon enough. So what happens during an N. fowleri infection? © 2014 Scientific American

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19855 - Posted: 07.21.2014

Nicola Davis The old adage that we eat with our eyes appears to be correct, according to research that suggests diners rate an artistically arranged meal as more tasty – and are prepared to pay more for it. The team at Oxford University tested the idea by gauging the reactions of diners to food presented in different ways. Inspired by Wassily Kandinsky's "Painting Number 201" Franco-Columbian chef and one of the authors of the study, Charles Michel, designed a salad resembling the abstract artwork to explore how the presentation of food affects the dining experience. "A number of chefs now are realising that they are being judged by how their foods photograph – be it in the fancy cookbooks [or], more often than not, when diners instagram their friends," explains Professor Charles Spence, experimental psychologist at the University of Oxford and a co-author of the study. Thirty men and 30 women were each presented with one of three salads containing identical ingredients, arranged either to resemble the Kandinsky painting, a regular tossed salad, or a "neat" formation where each component was spaced away from the others. Seated alone at a table mimicking a restaurant setting, and unaware that other versions of the salad were on offer, each participant was given two questionnaires asking them to rate various aspects of the dish on a 10-point scale, before and after tucking into the salad. Before participants sampled their plateful, the Kandinsky-inspired dish was rated higher for complexity, artistic presentation and general liking. Participants were prepared to pay twice as much for the meal as for either the regular or "neat arrangements". © 2014 Guardian News and Media Limited

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 14: Attention and Consciousness
Link ID: 19759 - Posted: 06.23.2014

By Ian Randall The human tongue may have a sixth sense—and no, it doesn’t have anything to do with seeing ghosts. Researchers have found that in addition to recognizing sweet, sour, salty, savory, and bitter tastes, our tongues can also pick up on carbohydrates, the nutrients that break down into sugar and form our main source of energy. Past studies have shown that some rodents can distinguish between sugars of different energy densities, while others can still tell carbohydrate and protein solutions apart even when their ability to taste sweetness is lost. A similar ability has been proposed in humans, with research showing that merely having carbohydrates in your mouth can improve physical performance. How this works, however, has been unclear. In the new study, to be published in Appetite, the researchers asked participants to squeeze a sensor held between their right index finger and thumb when shown a visual cue. At the same time, the participants’ tongues were rinsed with one of three different fluids. The first two were artificially sweetened—to identical tastes—but with only one containing carbohydrate; the third, a control, was neither sweet nor carb-loaded. When the carbohydrate solution was used, the researchers observed a 30% increase in activity for the brain areas that control movement and vision. This reaction, they propose, is caused by our mouths reporting that additional energy in the form of carbs is coming. The finding may explain both why diet products are often viewed as not being as satisfying as their real counterparts and why carbohydrate-loaded drinks seem to immediately perk up athletes—even before their bodies can convert the carbs to energy. Learning more about how this “carbohydrate sense” works could lead to the development of artificially sweetened foods, the researchers propose, “as hedonistically rewarding as the real thing.” © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19700 - Posted: 06.06.2014

by Catherine de Lange Could your ideal diet be written in your genes? That's the promise of nutrigenomics, which looks for genetic differences in the way people's bodies process food so that diets can be tailored accordingly. The field had a rocky start after companies overhyped its potential, but with advances in genetic sequencing, and a slew of new studies, the concept is in for a reboot. Last week, Nicola Pirastu at the University of Trieste, Italy, and his colleagues told the European Society of Human Genetics meeting in Milan that diets tailored to genes that are related to metabolism can help people lose weight. The team used the results of a genetic test to design specific diets for 100 obese people that also provided them with 600 fewer calories than usual. A control group was placed on a 600-calorie deficit, untailored diet. After two years, both groups had lost weight, but those in the nutrigenetic group lost 33 per cent more. They also took only a year to lose as much weight as the group on the untailored diet lost in two years. If this is shown to work in bigger, randomised trials, it would be fantastic, says Ana Valdes, a genetic epidemiologist at the University of Nottingham, UK. Some preliminary information will soon be available from Europe's Food4Me project. It is a study of 1200 people across several countries who were given either standard nutrition advice, or a similarly genetically tailored diet. "It's testing whether we can get bigger changes in diet using a personalised approach, and part of that is using genetic information," says team member John Mathers, director of the Human Nutrition Research Centre at Newcastle University, UK. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, 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: 19690 - Posted: 06.04.2014

Tastes are a privilege. The oral sensations not only satisfy foodies, but also on a primal level, protect animals from toxic substances. Yet cetaceans—whales and dolphins—may lack this crucial ability, according to a new study. Mutations in a cetacean ancestor obliterated their basic machinery for four of the five primary tastes, making them the first group of mammals to have lost the majority of this sensory system. The five primary tastes are sweet, bitter, umami (savory), sour, and salty. These flavors are recognized by taste receptors—proteins that coat neurons embedded in the tongue. For the most part, taste receptor genes present across all vertebrates. Except, it seems, cetaceans. Researchers uncovered a massive loss of taste receptors in these animals by screening the genomes of 15 species. The investigation spanned the two major lineages of cetaceans: Krill-loving baleen whales—such as bowheads and minkes—were surveyed along with those with teeth, like bottlenose dolphins and sperm whales. The taste genes weren’t gone per se, but were irreparably damaged by mutations, the team reports online this month in Genome Biology and Evolution. Genes encode proteins, which in turn execute certain functions in cells. Certain errors in the code can derail protein production—at which point the gene becomes a “pseudogene” or a lingering shell of a trait forgotten. Identical pseudogene corpses were discovered across the different cetacean species for sweet, bitter, umami, and sour taste receptors. Salty tastes were the only exception. © 2014 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19624 - Posted: 05.16.2014

Humans stink, and it’s wonderful. A few whiffs of a pillow in the morning can revive memories of a lover. The sweaty stench of a gym puts us in the mood to exercise. Odors define us, yet the scientific zeitgeist is that we don’t communicate through pheromones—scents that influence behavior. A new study challenges that thinking, finding that scent can change whether we think someone is masculine or feminine. Humans carry more secretion and sweat glands in their skin than any other primate. Yet 70% of people lack a vomeronasal organ, a crescent-shaped bundle of neurons at the base of each nostril that allows a variety of species—from reptiles to nonprimate mammals—to pick up on pheromones. (If you’ve ever seen your cat huff something, he’s using this organ.) Still, scientists have continued to hunt for examples of pheromones that humans might sense. Two strong candidates are androstadienone (andro) and estratetraenol (estra). Men secrete andro in their sweat and semen, while estra is primarily found in female urine. Researchers have found hints that both trigger arousal—by improving moods and switching on the brain’s “urge” center, the hypothalamus—in the opposite sex. Yet to be true pheromones, these chemicals must shape how people view different genders. That’s exactly what they do, researchers from the Chinese Academy of Sciences in Beijing report online today in Current Biology. The team split men and women into groups of 24 and then had them watch virtual simulations of a human figure walking (see video). The head, pelvis, and major joints in each figure were replaced with moving dots. Subjects in prior studies had ranked the videos as being feminine or masculine. For instance, watch the figure on the far left, which was gauged as having a quintessential female strut. Notice a distinctive swagger in the “hip” dots and how they contrast with the flat gait of the “male” prototype all the way to the right. © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, 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: 19565 - Posted: 05.03.2014

|By Daisy Yuhas Strange as it may sound, some scientists suspect that the humble armpit could be sending all kinds of signals from casual flirtation to sounding the alarm. That’s because the body’s secretions, some stinky and others below the threshold your nose can detect, may be rife with chemical messages called pheromones. Yet despite half a century of research into these subtle cues, we have yet to find direct evidence of their existence in humans. Humans and other animals have an olfactory system designed to detect and discriminate between thousands of chemical compounds. For more than 50 years, scientists have been aware of the fact that certain insects and animals can release chemical compounds—often as oils or sweat—and that other creatures can detect and respond to these compounds, which allows for a form of silent, purely chemical communication. Although the exact definition has been debated and redefined several times, pheromones are generally recognized as single or small sets of compounds that transmit signals between organisms of the same species. They are typically just one part of the larger potpourri of odorants emitted from an insect or animal, and some pheromones do not have a discernable scent. Since pheromones were first defined in 1959, scientists have found many examples of pheromonal communication. The most striking of these signals elicits an immediate behavioral response. For example, the female silk moth releases a trail of the molecule bombykol, which unerringly draws males from the moment they encounter it. Slower-acting pheromones can affect the recipient’s reproductive physiology, as when the alpha-farnesene molecule in male mouse urine accelerates puberty in young female mice. © 2014 Scientific American

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, 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: 19500 - Posted: 04.17.2014

Dr Nicola Davis The electronic nose in an instrument that attempts to mimic the human olfactory system. Humans and animals don't identify specific chemicals within odours; what they do is to recognise a smell based on a response pattern. You, as a human, will smell a strawberry and say "that's a strawberry". If you gave this to a traditional analytical piece of equipment, it might tell you what the 60-odd chemicals in the odour were - but that wouldn't tell you that it was a strawberry. How does it work? A traditional electronic nose has an array of chemical sensors, designed either to detect gases or vapours. These sensors are not tuned to a single chemical, but detect families of chemicals - [for example] alcohols. Each one of these sensors is different, so when they are presented to a complex odour formed of many chemicals, each sensor responds differently to that odour. This creates a pattern of sensor responses, which the machine can be taught [to recognise]. Can't we just use dogs? A dog is very, very sensitive. Special research teams work on training dogs to detect cancers as you would do explosives. What you we are trying to do with the electronic nose is create an artificial means of replicating what the dog does. Such machines have the advantage that they don't get tired, will work all day and you only need to feed them electricity. © 2014 Guardian News and Media Limited

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19441 - Posted: 04.03.2014

Dragonflies are full of surprises. They have six legs, but most can’t walk. Their giant, 30,000-lens eyes can detect ultraviolet light. And though they lack the brain architecture normally required for a sense of smell, a new study finds that dragonflies may use odors to hunt prey. Smelling, as we humans understand it, requires certain hardware. Our noses are packed with olfactory receptors, each of which is tuned to a precise scent molecule. (Indeed, a recent study suggests we can detect a trillion smells.) When one wafts into our nostrils, these receptors send nerve signals to sensory way stations called glomeruli, which pass them along to the brain for interpretation—“Oh, a rose!” Glomeruli are shared by most terrestrial mammals and insects, and until now, scientists believed they represented the only possible route to a sense of smell. Because dragonflies and their close cousins, damselflies, don’t possess glomeruli or any higher order smell centers in their brains, most scientists believed these insects were unable to smell anything at all. Invertebrate biologist Manuela Rebora at the University of Perugia in Italy was not one of them. When her team took a closer look at dragonfly and damselfly antennae with an electron microscope, they spotted tiny bulbs in pits that resembled olfactory sensilla. Like the insect equivalent of a nose, these sensilla house olfactory neurons. When Rebora’s team exposed the suspected sensilla to scents, they emitted nerve pulses, supporting the idea that damselflies and dragonflies perceive odors. © 2014 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19406 - Posted: 03.25.2014

Jessica Morrison The human nose has roughly 400 types of scent receptors that can detect at least 1 trillion different odours. The human nose can distinguish at least 1 trillion different odours, a resolution orders of magnitude beyond the previous estimate of just 10,000 scents, researchers report today in Science1. Scientists who study smell have suspected a higher number for some time, but few studies have attempted to explore the limits of the human nose’s sensory capacity. “It has just been sitting there for somebody to do,” says study co-author Andreas Keller, an olfactory researcher at the Rockefeller University in New York. To investigate the limits of humans' sense of smell, Keller and his colleagues prepared scent mixtures with 10, 20 or 30 components selected from a collection of 128 odorous molecules. Then they asked 26 study participants to identify the mixture that smelled differently in a sample set where two of three scents were the same. When the two scents contained components that overlapped by more than about 51%, most participants struggled to discriminate between them. The authors then calculated the number of possible mixtures that overlap by less than 51% to arrive at their estimate of how many smells a human nose can detect: at least 1 trillion. Donald Wilson, an olfactory researcher at the New York University School of Medicine, says the findings are “thrilling.” He hopes that the new estimate will help researchers begin to unravel an enduring mystery: how the nose and brain work together to process smells. © 2014 Nature Publishing Group,

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19394 - Posted: 03.21.2014

Brian Owens The distinctive aroma of goats does more than just make barnyards extra fragrant. Male goats can use their heady scent to make female goats ovulate simply by being near them. Researchers had ascribed this 'male effect' to chemicals known as primer pheromones — a chemical signal that can cause long-lasting physiological responses in the recipient. Examples of primer pheromones are rare in mammals; the male effect in goats and sheep, and a similar effect in mice and rats, where the presence of males can speed up puberty in females, are the only known cases. But exactly what substances are at work and how has remained a mystery. Now, reproductive biologist Yukari Takeuchi from the University of Tokyo and her colleagues have identified a single molecule, known as 4-ethyloctanal, in the cocktail of male goat pheromones that activates the neural pathway that regulates reproduction in females1. ”It has long been thought that pheromones have pivotal roles in reproductive success in mammals, but the mechanisms are scarcely known,” says Takeuchi. The researchers found that male goat pheromones are generally synthesized in the animal's head skin, so they designed a hat containing a material that captured their odorous molecules and placed them on the goats for a week to collect the scent. Analysis of the gases collected identified a range of compounds, many of which were unknown and were not present in castrated males. When exposed to a cocktail of 18 of these chemicals, the brains of female goats showed a sudden increase in the activity of the gonadotropin-releasing hormone (GnRH) pulse generator — the neural regulator of reproduction. © 2014 Nature Publishing Group,

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, 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: 19308 - Posted: 03.01.2014

By DEBORAH BLUM Toxicologists have long considered ethylene glycol, the active ingredient in many antifreeze and engine coolant formulas, to be a seductive and uniquely dangerous poison. For one thing, it’s sweet. “We actually had a mechanic who developed a taste for it,” recalled Dr. Marsha Ford, director of the Carolinas Poison Center in Charlotte, N.C. “He’d pour himself a little and sip it. And he kept doing that until he got sick.” And that’s the other danger: Ethylene glycol is a slow-acting poison. Even following a high dose, symptoms can take up to 48 hours to appear. The country’s poison control centers record more than 5,000 ethylene glycol ingestions annually; some 2,000 cases require medical treatment. Most are accidental, but ethylene glycol also figures in hundreds of suicide attempts every year — not to mention the occasional murder. Recently an Ohio woman was convicted of killing her fiancé by spiking raspberry iced tea with antifreeze. The situation for animals has been even more dangerous than for despised spouses. According to the Humane Society of the United States, as many as 90,000 pets and wild animals are poisoned annually by drinking spilled or carelessly stored products containing ethylene glycol. Now the manufacturers of those products have determined to do something about all the carnage. They are making antifreeze taste awful — so very bitter that it will be nigh impossible to drink by accident. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19280 - Posted: 02.22.2014

By DOUGLAS QUENQUA The smell of a person’s earwax depends partly on his ethnic origin, a new study reports, suggesting that the substance could be an overlooked source of personal information. The earwax of Caucasian men contains more volatile organic compounds than that of East Asian men, researchers at the Monell Chemical Senses Center in Philadelphia found. Twelve such compounds are common to both groups, they said, but 11 of those are more plentiful in Caucasians. Monell researchers have previously found that underarm odor contains clues to a person’s age, health and sex. They suspected that earwax might contain similar markers, since a 2006 study found that a gene related to underarm odor, which also varies by ethnicity, helps determine a person’s type of earwax. (East Asians are more likely to have dry earwax, for example.) "We’re at the beginning of exploring a new and interesting biofluid secretion that has not been looked at in this manner before," said George Preti, an organic chemist at Monell and the senior author of the new study, which was published in The Journal of Chromatography B. Because of the fatty nature of earwax, or cerumen, Dr. Preti says it is a probable repository for odorants produced by diseases and the environment, and hence a potentially valuable diagnostic tool. A 2013 study showed that a whale’s earwax contains evidence of the animal’s exposure to pollutants and stress hormones, and earwax odor in humans is a known indicator of branched-chain ketoaciduria, also known as maple syrup urine disease. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19258 - Posted: 02.18.2014

By SINDYA N. BHANOO Mosquito sperm have a sense of smell, researchers are reporting, in a finding that could suggest ways to help control the spread of disease-carrying insects. The sperm carries a set of chemical sensors identical to the olfactory receptors on the mosquitoes’ antennas, according to a study in Proceedings of the National Academy of Sciences. Mosquitoes mate just once in their lifetime, and the female stores the male’s sperm in an organ called a spermatheca. Before the eggs mature, the female seeks out blood using the receptors on her antennas. Soon after, chemical signals cause the sperm tails to beat rapidly and start the fertilization process. “The sperm may need a chemical signal to become ready for fertilization,” said Jason Pitts, a researcher at Vanderbilt University and an author of the study, which was supported by the Gates Foundation as part of its efforts to improve global health. Another author, Laurence Zwiebel, also a Vanderbilt researcher, called the dual use of the olfactory receptors a clear and clever example of convergent evolution: The mosquitoes, he said, “found something that works and use it in multiple ways.” The scientists think olfactory receptors may exist on the sperm of many other insects, and they are developing chemical compounds that can be applied to breeding grounds to block the receptors. “You can effectively confuse the sperm or make them inactive,” Dr. Zwiebel said. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, 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: 19241 - Posted: 02.12.2014

by Bob Holmes Midnight fridge raids are part and parcel of a late-night marijuana smoking session. A study in mice has provided the most complete explanation yet for why a spliff triggers intense hunger pangs. The findings, which elucidate the role of smell, also suggest that we might eventually be able to treat common disorders such as obesity and loss of appetite with a simple nasal spray. We know that the active ingredient in cannabis, THC, binds to cannabinoid receptors in the brain called CB1s. This binding inhibits chemical signals that tell us not to eat, and so make us feel hungry. But this isn't the end of the story. Since smell plays such a central role in making us feel hungry, it must be part of the explanation - but no one knew exactly how it fit. To find out, Giovanni Marsicano of the French research agency INSERM in Bordeaux and his colleagues genetically modified mice to make it possible to turn on and off the CB1 receptor in particular nerve cells within the smell, or olfactory, system. The key proved to be a group of nerve cells that carry signals from the cerebral cortex down to the olfactory bulb, the primary smell centre of the brain. When the team switched off CB1 on these cells, they found that hungry mice no longer ate more than their well-fed counterparts. Conversely, activating CB1 in the same cells by injecting THC caused hungry mice to eat even more. THC-treated mice also responded to less-concentrated food smells than untreated mice, a sign that the chemical had enhanced their sense of smell. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19230 - Posted: 02.10.2014

Ask a group of people to describe the color of a sheet of paper, a cloud, or a glass of milk, and chances are they’ll all say “white.” But ask the same group to describe the smell of cinnamon, and you’ll likely get a potpourri of answers, ranging from “spicy” to “smoky” to “sweet,” and sometimes all three. When it comes to naming smells, humans struggle to find concise, universal terms. Indeed, scientists have long thought the ability was out of our reach. But a new study indicates that the inhabitants of a remote peninsula in Southeast Asia can depict smells as easily as the rest of us pick colors. The study concerns the Jahai, nomadic hunter-gatherers who live in the mountain rainforests along the border between Malaysia and Thailand. Smell is very important to this society. Odors are often evoked in illness, or medicine, for example, and it is one of the few cultures to have words devoted exclusively to smells. “For example, the term pʔus (pronounced ‘pa-oos’) describes the smell of old huts, day-old food, and cabbage,” says Asifa Majid, a psychologist at the Centre for Language Studies at Radboud University Nijmegen in the Netherlands. This suggests, she says, that the Jahai can isolate basic smell properties, much like we can isolate the color white from milk. To find out if the Jahai are better at naming smells than the rest of us, Majid and colleagues asked native Jahai speakers and native English speakers to describe 12 different odors: cinnamon, turpentine, lemon, smoke, chocolate, rose, paint thinner, banana, pineapple, gasoline, soap, and onion. The Jahai easily and consistently named the odors, whereas English speakers struggled, the team reports in the February issue of Cognition. © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19129 - Posted: 01.14.2014

Brian Owens Fruitflies know exactly how much alcohol will be good for their young. Larvae living on a food source with the right concentration of ethanol will grow into heavy, healthy adults and will be protected against parasites — which explains why the insects are attracted to rotting fruit or the crate of empty beer bottles in your kitchen but not to the vodka or gin. Now researchers have uncovered the neural mechanism that allows the fruitfly Drosophila melanogaster to choose the best place to lay its eggs. The work is published today in Proceedings of the National Academy of Sciences1. A team led by Ulrike Heberlein, a molecular biologist at the Howard Hughes Medical Institute’s Janelia Farm Research Campus in Ashburn, Virginia, found that clusters of neurons, working in opposition to each other, help the flies to choose the place with the most beneficial concentration of ethanol in which to lay their eggs. The neurons all release the neurotransmitter dopamine, a key player in the brain's reward circuitry. Neurons of the PAM and PPM3 clusters encourage the flies to seek out ethanol, whereas PPL1 neurons apply the brakes, preventing the flies from laying their eggs on food containing high levels of ethanol that could harm the larvae. “They can discriminate among ethanol concentrations that are very similar — 3% versus 5% — so the system evolved to have great sensitivity,” says Heberlein. Their favourite booze strength is 5%, similar to that of a typical beer. Heberlein's team also traced the neurons involved in ethanol preference to specific brain regions. Both the pro-ethanol PAM and anti-ethanol PPL1 neurons were active in the mushroom body, whereas the pro-ethanol PPM3 ones were active in the ellipsoid body. Both of these brain structures are involved in decision-making and memory, and mushroom body neurons also play a part in ethanol-reward memory. © 2013 Nature Publishing Group,

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19013 - Posted: 12.10.2013

By Julia Calderone As we sat in my car outside a silent movie theater in Los Angeles, my friend anxiously opened a plastic bag containing a white T-shirt she’d slept in for the past three nights. “Does it smell like me?” she asked nervously, gesturing the open end toward my face. I stuck my nose into the bag and inhaled. We were about to attend a pheromone-based speed dating party with the following rules: 1. Find a clean white T-shirt. 2. Sleep in only that shirt for three consecutive nights. 3. Bring the shirt to the party sealed in a bag. As we walked into the theater, coordinators assigned each of our bags a unique color-coded sticker (pink for female, blue for male), and tossed them into a pile. A pack of hipsters nursing PBRs sat in the wooden theater seats, slightly amused by the bizarre 70s Egyptian-themed silent porn projected onto the screen. In the courtyard, 20-somethings mingled by the outdoor bar. Did they think alcohol would make us okay with sniffing strangers’ dirty laundry? Mounds of bags sat on two long tables – beckoning our nostrils. We were instructed to sniff as many T-shirts of the sex we were attracted to, and select shirts that innately smelled the sexiest. I came across bag number 166, which shockingly smelled exactly like my grandmother’s house – a delightful mix of Christmas and chicken parmesan. The point was to trust our instincts, right? I went with it. © 2013 Scientific American

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, 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: 19005 - Posted: 12.06.2013