The latest diagnostic tool for oncology comes on four paws and is defined by its very effective nose. In a small study, Japanese researchers found that a dog could detect cases of colorectal cancer by sniffing patients’ breath or stool samples. Previous experiments have shown that dogs can sniff out cases of skin, lung, bladder, and breast cancers; researchers think the tumors give off chemical signals that the dog can detect in bodily substances.
The cancer expert in this case was an eight-year-old black Labrador named Marine who was trained to search for disease traces at the St. Sugar Cancer Sniffing Dog Training Center in Chiba, Japan. She must have been a good student. The research, published in the journal Gut, showed that she had a high success rate:
The Labrador retriever was at least 95 percent as accurate as colonoscopy when smelling breath samples, and 98 percent correct with stool samples, according to the study…. The dog’s sense of smell was especially effective in early-stage cancer, and could discern polyps from malignancies, which colonoscopy can’t. [Bloomberg]
Lead researcher Hideto Sonoda says it would be impractical to use dogs for routine bowel cancer screenings, but adds that further research into dogs’ diagnostic ability could lead to the development of an electronic nose.
Dr Sonoda told the BBC: “The specific cancer scent indeed exists, but the chemical compounds are not clear. Only the dog knows the true answer. It is therefore necessary to identify the cancer specific volatile organic compounds [smells] detected by dogs and to develop an early cancer detection sensor that can be substituted for canine scent judgement. To complete the sensor useful in clinical practice as a new diagnostic method is still expected to take some time.” [BBC]
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Image: flickr / pmarkham
Researchers have found the secret to improving a robot’s sense of smell: Shove frog eggs up its nose. A team at the University of Tokyo has developed a sensor made from a genetically modified frog egg that can help a robot pick out insect smells and pheromones.
As useful as a moth-smelling robot may seem, researchers believe the study published yesterday in Proceedings of the National Academy of Sciences is just one step towards an inexpensive but sensitive chemical detector. Study coauthor Shoji Takeuchi explains that such a device could pick out gases like carbon dioxide:
“When you think about the mosquito, it is able to find people because of carbon dioxide from the human. So the mosquito has CO2 receptors. When we can (extract) DNA (from the mosquito) we can put this DNA into the frog eggs to detect CO2.” [Reuters]
Here’s how they did it.
Step 1 — Get Some Frog Eggs
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We knew that bacteria could stink, but new research asks if bacteria can smell. A study published today argues that Bacillus licheniformis found in soil can sense ammonia given off by neighboring bacteria. Though we might turn our noses when we smell the gases given off by neighbors, the bacteria respond to ammonia by building a thick biofilm coating.
The research appears today in Biotechnology Journal. Previous studies have shown that bacteria can sense gases such as oxygen, but this is the first study to argue that bacteria can smell, since ammonia has a scent. Lead author Reindert Nijland explains that bacteria break the pungent gas down for its useful nitrogen, so an ammonia-detector and biofilm response might be a useful survival tool. He even suggests that this might be the earliest example of olfaction in evolutionary history.
“Ammonia is the simplest available nitrogen source,” Nijland said. “All organisms need nitrogen to produce their proteins.” The ammonia is thought to signal both the presence of nutrients and the presence of other bacteria, since the biofilms Bacillus species produce in response to ammonia contain antibiotics that can kill competing bacteria. And the ability to “smell” ammonia “gives bacteria a way to sense nutrients where nutrients are and then migrate towards them,” he said. [The Scientist]
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Hounds, pointers, and other dogs bred for their excellent abilities to pick up a scent tend to have longer snouts—but it’s not just that a bigger nose is a better one. Researchers have found that human domestication of dogs has shifted the structure and alignment of some dogs’ brains. And in those varieties with shorter snouts—which humans bred for other reasons, like appearance—the olfactory brain region rotated to a different part of their skull, leaving scientists to question whether we’ve crossed up their smelling abilities (and perhaps more).
Since the first wolf was domesticated an estimated 12,000 years ago, “selective breeding has produced a lot of [anatomical] variation, but probably the most dramatic is in terms of skull shape,” said study co-author Michael Valenzuela [National Geographic].
For this study, which appears in the open-access journal PLoS One, Valenzuela and colleagues examined the brains of 11 dog breeds and found great variation in the size and shape of their skulls. The breeds with shorter snouts had brains that rotated forward by as much as 15 degrees over the generations, the scientists say. That means that the olfactory lobe, as well as other parts of these dogs‘ brains, has shifted position and shape because humans guided their evolution through domestication.
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Sure, the planet’s increasing carbon dioxide levels are making the oceans more acidic, but what does that really mean for sea life? We’ve already heard that the ocean’s changing chemistry is damaging corals and interfering with mussels, but that’s just the beginning. It turns out things could get seriously weird.
In a paper published this week in The Proceedings of the National Academy of Sciences, researchers led by Philip L. Munday of James Cook University have given us a concrete example: the increased CO2-levels make some fish purposely swim towards predators.
As part of his experiment, Munday used a Y-shaped maze to force baby clownfish to choose between two paths. One path reeked of rock cod, a natural predator; the other had no danger scents. Munday’s team compared the choices of fish raised in water of varying carbon dioxide concentrations, from today’s levels of 390 parts per million up to future expected levels of 850 ppm.
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It’s the essence of instinct: If you take a lab mouse who has never caught a glimpse of a cat and waft a little eau de feline towards it, the mouse will freeze in fear, and will then back away from the source of the odor. Now researchers have pinned down the chemical signals the mice are reacting to–and have shown in the process a fascinating new form of inter-species communication.
Mice have a specialized organ in their noses that picks up chemical signals, called the vomeronasal organ, which helps them detect pheromones emitted by other mice. These mice pheromones have a direct effect on behavior–most obviously in the realms of mating and fighting. In this new study, published in the journal Cell, neurobiologist Lisa Stowers decided to investigate whether the vomeronasal organ was capable of picking up signals from other species as well.
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In today’s edition of far-out science, researchers have found evidence that the wafting aroma of food has an effect on an organism’s lifespan–and they’ve demonstrated that interfering with a fruit fly’s sense of smell causes it to live a longer, healthier life. While there’s no guarantee that the trick would work for humans, optimistic researchers suggest that certain odors—or drugs that block us from sensing them—might one day help prevent disease and extend lives [ScienceNOW].
In the past decade, scientists have established a clear connection between extremely low-calorie diets and extended lifespans; studies have demonstrated that yeast, fruit flies, mice, and monkeys on these diets live longer than their peers. While the exact mechanism at work isn’t yet clear, researchers suspect that a near-starvation diet causes an organism’s metabolism to slow down, and triggers other changes that evolved to help organisms survive in times when food was scarce. Now scientists say it may not be just what a creature eats, but also what it smells that has an effect on how long it lives.
In one 2007 study, molecular biologist Scott Pletcher and his colleagues found that completely eliminating fruit flies’ sense of smell caused them to live nearly 20 percent longer than normal flies. They also found that wafting the smell of yeast, a tasty treat for fruit flies, towards flies that were on a low-cal, live-extending diet hastened the death of those flies. This led the scientist to hypothesize that specific odors might be influencing the flies’ lifespans. Luckily, other scientists had identified a receptor in a group of neurons that enable fruit flies to smell carbon dioxide, which signals the presence of a good meal of tasty yeast [ScienceNOW]. So, Pletcher and his team set out to find if the CO2 had anything to do with the duration of the flies’ lives.
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The nose knows when you’ve walked into a library or archive populated by books of a certain age: The distinctive musty smell of the old paper fills the halls and reading rooms. Now, for a study in Analytical Chemistry, a research team has analyzed the chemicals that combine to form the “old book smell,” and says that one day a book’s odor could tell scholars a lot about the tome’s history.
The international research team, led by Matija Strlic from University College London’s Centre for Sustainable Heritage, describes that smell as “a combination of grassy notes with a tang of acids and a hint of vanilla over an underlying mustiness. This unmistakable smell is as much part of the book as its contents,” they wrote in the journal article [BBC News]. The smell is a result of volatile organic compounds that are released as the paper ages.
After watching conservators smell the paper while investigating old books, Strlic applied a “sniff test” based on gas chromotography-mass spectrometry to sort out the chemicals mingling in the odors of 72 older documents. The researchers identified 15 organic compounds that made good markers to track the condition of books [Scientific American]. The system isn’t ready for librarians or conservators yet, but Strlic says he envisions a hand-held model they could use to analyze the age of a book, or what materials constitute its pages and binding, in a noninvasive way. Currently, age-testing a book usually requires snipping off pieces for testing.
The sooner the better, because books aren’t forever. Paper produced until about 1850 was made to last for millenniums. The development of new wood-pulping techniques in the middle of the 19th century and the use of rosin sizing reduced the longevity of paper. The acidity of paper made with these techniques causes them to degrade more quickly than the older papers — or newer ones made with different methods after 1990 [Wired.com].
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The Intersection: On Books, in which DISCOVER blogger Sheril Kirshenbaum sings the praises of that old book smell.
Image: flickr / Guldfisken
Curvis Bickham spent eight months in prison for a triple-homicide because a police dog confused his scent with that of the killer. Now Bickham and others who spent months in jail after dogs linked their scents to evidence from crimes they did not commit are filing a lawsuit claiming Texas authorities falsely arrested and imprisoned them, their attorney said Tuesday [AP]. In a scent lineup, dogs sniff items found at a crime scene, and then sniff jars swabbed with the suspects’ scents and the scents of others not involved in the crime. When the dogs link crime scene and suspect, that evidence is often relied on heavily in court by the prosecution. Alaska, Florida, New York and Texas all use scent lineups to link suspects to crimes.
Dogs are used all the time to fight crime—from sniffing out bombs and drugs to locating dead bodies. However, scent lineups have critics barking. They say the lineups are poorly controlled, and argue that avoiding cross-contamination is basically impossible. The main target of the current lawsuit is Fort Bend County Deputy Keith Pikett—whose home-trained bloodhounds identified the suspects. A 2004 F.B.I. report warned that dog scent work “should not be used as primary evidence,” but only to corroborate other evidence. In several of the cases that were based on Deputy Pikett’s dogs, however, the scent lineups appear to have provided the primary evidence, even when contradictory evidence was readily available [The New York Times]. Deputy Pikett, by his own estimation, has conducted thousands of scent lineups.
The three men who filed the lawsuit against Deputy Pickett were all eventually set free after contradictory evidence proved their innocence. The Innocence Project of Texas, a legal defense organization … released a report last month that excoriated dog scent lineups as a “junk science injustice” [The New York Times]. Dog scent lineups bring to mind another high profile forensic science debate in Texas that many believe led to the execution of an innocent man. Now that the science behind dog scent lineups is coming under the same scrutiny, one can’t help but wonder if scent lineups might have led to a similar outcome.
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Image: flickr / contadini
Scientists have found another reason why the fizz in a glass of champagne is so important: Besides tickling the tongue and pleasing the eye, the bubbles also release aromatic compounds that they’ve dragged up from the liquid in the glass. A new study found that concentrations of certain chemical compounds are higher in the air just above the glass than in the actual champagne.
Wine expert Jamie Goode comments: “In the past, we thought that the carbon dioxide in the bubbles just gave the wine an acidic bite and a little tingle on the tongue, but this study shows that it is much more than this” [BBC News]. Smelling the chemical compounds enhances the overall flavor of the champagne, researchers say.
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Each adult Argentine ant has two chemical fragrances that send out critical messages to other ants in its colony, in what is literally a matter of life and death. Normal, still-breathing adult workers carry chemicals signaling “Dead ant — haul to burial pile” on their outer covering, proposes [entomologist] Dong-Hwan Choe…. What prevents awkward mistakes about who’s really dead are two additional compounds also found on the covering of living ants, Choe suggests. These compounds temporarily inhibit responses to the death cues by signaling, “Wait — still alive so far,” Choe and his colleagues report [Science News].
Choe’s study, which was published in the Proceedings of the National Academy of Sciences, set out to examine the corpse-ridding behavior, or necrophoresis, that is common to many ants and other social insects, and helps maintain good sanitation in the colony…. The prevailing theory of necrophoresis had been that ants were responding to fatty acids and other chemical cues from the decomposing corpse. But the researchers noticed that ants would haul a corpse away within an hour after death — before much decomposition began [The New York Times].
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Researchers may have determined the method by which some animals can literally sniff out a sick individual–and hence avoid it to protect their own health. A team of scientists has identified a type of smell receptor in mice that seems to respond to disease-related molecules produced by bacteria, viruses, or as the result of inflammation [New Scientist].
Scientists have previously identified a number of mouse smell receptors, cell-surface proteins in the animals’ noses that pick up everything from the fragrance of food to the scent of fear…. Neurogeneticist Ivan Rodriguez of the University of Geneva in Switzerland and colleagues wondered whether there might be additional such receptors that respond to a disease “scent,” perhaps by detecting chemicals associated with bacteria and inflammation [ScienceNOW Daily News]. After scanning the mouse genome for genes in the olfactory system, they detected genes for five new smell receptors that seemed to be likely candidates. The receptors are part of a known family of proteins that are involved in immune response; other proteins in the same family detect chemicals given off by pathogens in an animal’s own blood.
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When two people get knocked off their feet by physical chemistry, their friends may offer this standard glib explanation: “It’s all about the pheromones.” But in fact, 50 years after the term “pheromones” was coined by biologists to refer to the chemical messages passed within many insect and mammal species, researchers still haven’t found proof that humans emit or detect such chemicals. In an essay in Nature [subscription required] marking the 50-year milestone, zoologist Tristram Wyatt sums up the state of the research, and reminds the gullible not to buy any love potions that boast of their pheromone content.
The first studies took place in 1959, when German researchers discovered a chemical called bombykol that’s secreted by female silk moths and that immediately sends males into a mating frenzy. Following that Nobel Prize-winning work, biologists proceeded to find pheromones “across the animal kingdom, sending messages between courting lobsters, alarmed aphids, suckling rabbit pups, mound-building termites and trail-following ants. They are also used by algae, yeast, ciliates and bacteria” [Wired News], Wyatt writes. Pheromones have been found to play a part not just in mating rituals, but also battles for dominance, warnings about approaching danger, and cooperative behavior.
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Researchers have used a CT scanner to peer inside the hollow, fossilized skulls of a group of meat-eating dinosaurs that dominated the Jurassic Period, and found that the Tyrannosaurus rex had another advantage besides its size, speed, and pointy teeth–it also had an excellent sense of smell. Study coauthor Darla Zelenitsky says the scans show the impressions left on the skull by different brain regions, and says the T. rex had the biggest olfactory bulb, which regulates the sense of smell.
Zelenitsky says the findings suggest that the T. rex relied on smell extensively. “It’s probably fairly significant, because the sense of smell was likely used for foraging or searching for food,” Zelenitsky said. “And as well, it could have been used for patrolling relatively large home ranges. So, in that respect, it would have been a significant part of the biology and daily activities of the animal” [Calgary Herald].
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A mouse’s nose has a cluster of specialized cells that respond to the chemical signals sent out by fellow mice that are in distress, researchers report, meaning that mice can literally smell fear. A lump of nerve cells in the nose tip called the Grueneberg ganglion responds to the “fear pheromones” of imperiled creatures, sending a signal straight to the brain. As Grueneberg ganglia are known to exist in rodents, cats, apes, and humans, researchers say it’s likely that the cells perform the same function in all mammals.
In a new study, researchers dosed water dishes with mouse alarm pheromones, and put the dishes in cages with both normal mice and mice whose ganglia had been removed. The contrast was very striking, [lead researcher Marie-Christine] Broillet said. “The normal mouse immediately gets scared and goes to the corner of the box and freezes,” she said. But mice without the ganglia carried on as before, seemingly unaware of the danger signals. Both groups were able to sniff out cookies hidden in their cages, however, suggesting the altered group’s sense of smell was otherwise unaffected [National Geographic News].
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