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A neurotransmitter called Nppb, we now know, plays a vital role in the sensation of an itch—and removing it can prevent itchiness entirely. Image via Wikimedia Commons/Orrling

There’s a lot we don’t understand about an itch. Why do itches sometimes pop up for no apparent reason? Why is itching contagious? Why can the very idea of an itch—maybe even the fact that you’re currently reading about itching—cause you to feel the actual physical sensation of one?

Given all this uncertainty, a new discovery reported today in Science should at least scratch the surface of your curiosity and answer a question you’ve been itching to ask (terrible puns intended). A pair of molecular geneticists from the National Institutes of Health, Santosh Mishra and Mark Hoon, isolated a crucial signaling molecule produced by nerve cells that is necessary for passing along the sensation of an itch to the brain.

The pair worked with mice, and started off by examining the neurotransmitter chemicals produced by a type of neuron that runs all the way from the animals’ skin into their spinal columns. These neurons are known to be involved in passing along sensory information about the outer environment, including sensations of heat and pain. They measured that one of the neurotransmitters produced by these nerve cells—a chemical called Nppb (natriuretic polypeptide b)—was secreted in excess when the mice were subjected to a range of itch-inducing substances, such as histamine (the natural compound that triggers the itchiness associated with allergies) and chloroquine (a malaria drug that’s notorious for causing itching as a side-effect).

To test whether Nppd played a role in the itching, they genetically engineered some mice so that they failed to produce the chemical. Initially, they checked to see if these engineered mice were impervious to other types of sensations also conveyed by these neurons (pain, movement and heat), but they seemed to behave just the same as the normal mice, indicating Nppb wasn’t involved in the transmission of those stimuli.

Then, they exposed them once again to the itch-inducing chemicals. The normal mice scratched away, but the genetically engineered mice were another story. “It was amazing to watch,” Mishra said in a press statement. “Nothing happened. The mice wouldn’t scratch.”

Nppb, they determined, plays a key role in passing along the sensation of an itch from these neurons to the brain—especially because, when they injected these same mice with doses of Nppb, they suddenly started scratching just like the others.

To investigate just how Nppb relays this message, they zeroed in on a spot in the mice’s spines called the dorsal horn, in which sensory information from the skin and muscles gets integrated into the spinal column and sent to the brain. In this area, they discovered a high concentration of neurons with a receptor called Npra (natriuretic peptide receptor A) that seemed likely to accept the Nppb molecules secreted when the mice encountered an itch-triggering substance.

Sure enough, when they removed the neurons with the Npra receptor from normal, non-engineered mice that produced Nppb, they too stopped scratching when exposed to the substances. This indicates that Nppb is crucial for passing along the itch sensation from the nerves that reach out into the skin to the spine, and that it fits into the Npra receptor on spinal nerve cells, which then convey the sensation to the brain. But removing these receptors didn’t impact the transmission of pain or touch, indicating that Npra is specifically involved in the itch sensation pathway. This comes as a surprise, as most previous research has indicated that the pain and itching nervous networks are intricately related.

While this chemical pathway explains part of the physical mechanism behind an itch, scientists still don’t fully understand the underlying evolutionary reason for the sensation in the first place. Some have speculated that it serves as a defense measure against insects, parasites and allergens, prompting us to scratch—and, ideally, remove the offending item from our skin—before it causes further damage.

Regardless of the evolutionary reason, our nervous system is similar enough to that of mice that the finding could help us better understand itching patterns in humans—perhaps people who are more prone to itching naturally produce higher levels of Nppb, compared to those who get biten by a mosquito and find the itchiness easy to ignore. On a practical level, the discovery could eventually help us develop anti-itch drugs for people with chronic itching ailments, such as allergic reactions or skin conditions like eczema, which affects an estimated 30 million people.

The problem, though, is that Nppb plays several other important roles in the body (it was originally discovered due to its role in the regulation of blood circulation and pressure) so simply creating a drug that disables Nppb is likely to cause disruptive side-effects that go way beyond itching. But looking more closely into the way the Nppb molecule acts as a “start switch” for itching in humans—and perhaps figuring out a way to safely turn the switch off—could potentially provide relief for itchiness caused by all sorts of triggers, because in the mice, at least, the molecule was found to be involved in the whole range of itch-inducing substances the team tested.

New isotopic analysis of Apollo-era Moon rocks shows that the water locked inside them likely came from our planet . Image via Wikimedia Commons/Gregory H. Revera

In September 2009, after decades of speculation, evidence of water on the surface of the Moon was discovered for the first time. Chandrayaan-1, a lunar probe launched by India’s space agency, had created a detailed map of the minerals that make up the Moon’s surface and analysts determined that, in several places, the characteristics of lunar rocks indicated that they bore as much 600 million metric tonnes of water.

In the years since, we’ve seen further evidence of water both on the surface and within the interior of the Moon, locked within the pore space of rocks and perhaps even frozen in ice sheets. All this has gotten space exploration enthusiasts pretty excited, as the presence of frozen water could someday make permanent human habitation of the Moon much more feasible.

For planetary scientists, though, it’s raised a knotty question: How did water arrive on the Moon in the first place?

A new paper published today in Science suggests that, unlikely as it may seem, the Moon’s water originated from the same source as the water that comes out of the faucet when you open a tap. Just as many scientists believe the Earth’s entire supply of water was initially delivered via water-bearing meteorites that traveled from the asteroid belt billions of years ago, a new analysis of lunar volcanic rocks brought back during the Apollo missions indicates the Moon’s water has its roots in these same meteorites. But there’s a twist: Before reaching the Moon, this lunar water was first on Earth.

A closeup of a melt inclusion inside lunar rocks. These inclusions reveal clues about the water content trapped within the Moon. Image via John Armstrong, Geophysical Laboratory, Carnegie Institution of Washington

The research team, led by Alberto Saal of Brown University, analyzed the isotopic composition of hydrogen found in water within tiny bubbles of volcanic glass (supercooled lava) as well as melt inclusions (blobs of melted material trapped in slowly cooling magma that later solidified) in the Apollo-era rocks, as shown in the image above. Specifically, they looked at the ratio of deuterium isotopes (“heavy” hydrogen atoms that contain an added neutron) to normal hydrogen atoms.

Previously, scientists have found that in water, this ratio changes depending on where in the solar system the water molecules initially formed, as water that originated closer to the Sun has less deuterium than water formed further away. The water locked in the lunar glass and melt inclusions was found to have deuterium levels similar to that found in a class of meteorites called carbonaceous chondrites, which scientists believe to be the most unaltered remnants of the nebula from which the solar system formed. Carbonaceous chondrites that fall to Earth originate in the asteroid belt between Mars and Jupiter.

Higher deuterium levels would have suggested that water was first brought on to the Moon by comets—as many scientists have hypothesized—because comets largely come from the Kuiper belt and Oort Cloud, remote regions far beyond Neptune where deuterium is more plentiful. But if the water in these samples represents lunar water as a whole, the findings indicate that the water came from a much closer source—in fact, the same source as the water on Earth.

The simplest explanation for this similarity would be a scenario in which, when a massive collision between a young Earth and a Mars-sized proto-planet formed the Moon some 4.5 billion years ago, some of the liquid water on our planet was somehow preserved from vaporization and transferred along with the solid material that would become the Moon.

Our current understanding of massive impacts, though, doesn’t allow for this possibility: The heat we believe would be generated by such an enormous collision would theoretically vaporize all lunar water and send it off into space in a gaseous form. But there are a few other scenarios that might explain how water was transferred from our proto-Earth to the Moon in other forms.

One possibility, the researchers speculate, is that the early Moon borrowed a bit of Earth’s high-temperature atmosphere the instant it formed, so any water that had been locked in the chemical composition of Earth rocks pre-impact would have vaporized along with the rock into this shared atmosphere after impact; this vapor would have then coalesced into a solid lunar blob, binding the water into the chemical composition of lunar material. Another possibility is that the rocky chunk of Earth was kicked off to form the Moon retained the water molecules locked inside its chemical composition, and later on, these were released as a result of radioactive heating inside the Moon’s interior.

Evidence from recent lunar missions suggests that lunar rocks—not just craters at the poles—indeed contain substantial amounts of water, and this new analysis suggests that water originally came from Earth. So the findings will force scientists to rethink models of how the Moon could have formed, given that it clearly didn’t dry out completely.

The creamy sticks of color seen here are just the latest in a long history of lipsticks—historical records suggest that humans have been artificially coloring their lips since 4,000 B.C. Photo by Flickr user ookikioo

Lipstick has seen a fair share of funky ingredients in its long history of more than 6,000 years, from seaweed and beetles to modern synthetic chemicals and deer fat. In recent years, traces of lead have been found in numerous brands of the popular handbag staple, prompting some manufacturers to go the organic route. This week, more dangerous substances joined the roster.

Researchers at Berkeley’s School of Public Health at the University of California tested 32 different types of lipstick and lip gloss commonly found in the brightly lit aisles of grocery and convenience stores. They detected traces of cadmium, chromium, aluminum, manganese and other metals, which are usually found in industrial workplaces, including make-up factories. The report, published in the journal Environmental Health Perspectives, indicated that some of these metals reached potentially health-hazardous levels.

Lipstick is usually ingested little by little as wearers lick or bite their lips throughout the day. On average, the study found, lipstick-clad women consume 24 milligrams of the stuff a day. Those who reapply several times a day take in 87 milligrams.

The researchers estimated risk by comparing consumers’ daily intake of these metals through lip makeup with health guidelines. They report that an average use of some lipsticks and lip glosses results in “excessive exposure” to chromium, and frequent use can lead to overexposure to aluminum, cadmium and manganese.

Minor exposure to cadmium, which is used in batteries, can result in flu-like symptoms such as fever, chills and achy muscles. In the worst cases, the metal is linked to cancer, attacking the cardiovascular, respiratory and other systems in the body. Chromium is a carcinogen linked to stomach ulcers and lung cancer, and aluminum can be toxic to the lungs. Long-term exposure to manganese in high doses is associated with problems in the nervous system. There are no safe levels of chromium, and federal labor regulations require industrial workers to limit exposure to the metal in the workplace. We naturally inhale tiny levels of aluminum present in the air, and many FDA-approved antacids contain the metal in safe levels.

Despite the presence of these metals in lipstick, there’s no need to start abandoning lipstick altogether—rather, the authors call for more oversight when it comes to cosmetics, for which there are no industry standards regulating their metal content if produced in the United States. 

After all, cadmium and other metals aren’t an intended ingredient in lipstick—they’re considered a contaminant. They seep into lipstick when the machinery or dyes used to create the product contain the metals themselves. This means trace amounts are not listed on the tiny stickers on lipstick tubes, so there’s no way to know which brands might be contaminated.

Concern about metals in cosmetics came to the forefront of American media in 2007, when an analysis of 33 popular brands of lipstick by the Campaign for Safe Cosmetics showed that 61 percent of them contained lead. The report eventually led the Food and Drug Administration (FDA), which doesn’t regulate cosmetics, to look into the issue, and what it found wasn’t any better: it found lead in all of the samples tested, with levels four times higher than the earlier study, ranging from 0.09 parts per million to 3.06 parts per million. According to the Centers for Disease Control and Prevention, there is no safe level of lead for humans.

So we’ve got cadmium, chromium, aluminum, manganese and lead in our lipstick. What else? Today, most lipstick is made with beeswax, which creates a base for pigments, and castor oil, which gives it a shiny, waxy quality. Beeswax has been the base for lipstick for at least 400 years–England’s Queen Elizabeth I popularized a deep lip rouge derived from beeswax and plants.

Lipstick as we know it appeared in 1884 in Paris, wrapped in silk paper and made from beeswax, castor oil and deer tallow, the solid rendered fat of the animal. At the time, lipstick was often colored using carmine dye. The dye combined aluminum and carminic acid, a chemical produced by cochineals–tiny cacti-dwelling insects–to ward off other insect predators.

That early lipstick wasn’t the first attempt at using insects or to stain women’s mouths. Cleopatra’s recipe for homemade lipstick called for red pigments drawn out from mashed-up beetles and ants.

But really, any natural substance with color was fair game for cosmetics, regardless of its health effects: Historians believe women first starting coloring their lips in ancient Mesopotamia, dotting them with dust from crushed semi-precious jewels—these lovely ancients were eating tiny bits of rocks whenever they licked their lips. Ancient Egyptians used lip color too, mixing seaweed, iodine and bromine mannite, a highly toxic plant-derived chemical that sickened its users.

From mannite to heavy metals, humanity’s quest for painted beauty doesn’t seem to have progressed far from toxic roots. The sacrifices we make for fashion!

Swedish researchers are developing a system that tests for 12 different drugs on your breath, including cocaine, marijuana and amphetamines. Image via SensAbues

Your breath says a lot about you. Recent research has found that the chemicals present in each person’s breath can provide a unique “breathprint” that differs from person to person, while other scientists have worked on breathalyzer-like tests that can indicate the presence of a bacterial infection inside someone’s body.

In the decades since the 1960s, though, when the first electronic breathalyzer for blood alcohol content was developed, research has led to relatively little advancement in the use of chemical breath analysis for law enforcement purposes. Police have long been able to instantly test a person’s level of alcoholic intoxication by the side of a road, but testing for other drugs has required blood or saliva—substances that are more invasive acquire and that typically have to be sent to a crime lab for processing. Both factors make it difficult to figure out who’s under the influence at, say, the scene of a car accident right after it occurs.

But new research suggests that the status quo might be changing in a hurry. A study published yesterday in the Journal of Breath Research reveals that scientists can now use breath analysis to test for the presence of 12 different drugs in the body, including cocaine, marijuana and amphetamines. Previous work has shown that such technology can reliably test for several of these drugs, and this new study is the first time the drugs alprazolam (commercially known as Xanax, useful for treating anxiety disorders) and benzoylecgonine (a topical pain killer) have been detected. Members of the research group, from Sweden’s Karolinska Institutet, have already created a commercially-available breath testing system, called SensAbues—and it’s easy to speculate that law enforcement across the U.S. (and around the world) would love to get their hands on such technology as soon as possible.

Tiny amounts of microparticles in your breath reflect the substances in your bloodstream—and can be trapped and preserved for analysis. Image via SensAbues

The research team, led by Olof Beck, conducted the new study by testing the breath of 46 individuals who were checked into a drug addiction emergency clinic, had taken drugs about 24 hours earlier and volunteered to participate in the study. Each participant exhaled about 20 deep breaths into the SensAbues filter (which takes 2-3 minutes), and the solid and liquid microparticles suspended in their breath were trapped on a disk for analysis.

These tiny quantities of microparticles reflect the substances in a person’s bloodstream, because small amounts of the molecules from our blood diffuse into the fluid that lines our lungs’ bronchioles and then into our breath. By isolating these particles and analyzing them with liquid chromatography and mass spectrometry, the research team was able to determine the drugs present in each person’s body with a decent level of accuracy.

They compared the results to blood and urine samples taken from each of the participants, as well as their own reports of what drugs they’d taken in the previous 24 hours, and on the whole, the tests performed pretty well—although some progress clearly still needs to be made. All 46 people had reported taking one of the 12 detectable illegal substances, and drugs were detected in the breath of 40 of them (87 percent). Most of the particular drugs detected matched with self-reports and blood tests, but 23 percent of the time, the breath tests also indicated the presence of a drug that hadn’t actually been taken. This level of accuracy was higher than previous studies the team has done, as they’ve slowly refined the system to cut down on false positives and improve the detection rate.

Currently, using the SensAbues system would only allow officials to collect a sample and send it elsewhere for analysis. But the researchers say that advances in the cost and portability of chemical analysis could eventually allow for the same sort of roadside breath testing for drugs that we currently have for alcohol.

Another scientific hurdle is data: Unlike for alcohol, we still don’t know what a given quantity of drug molecules detected on someone’s breath means in terms of how much of the drug is actually in their bloodstream (although an accurate detection of any illegal substance might be all law enforcement officials may be after). We also don’t know how long traces of these drugs remain on a person’s breath, and how quickly they degrade.

If scientists are able to make some progress in figuring this all out, though—and if they can make the testing procedure more accurate—roadside drug tests could become a routine part of law enforcement protocol.

Flamingos depend on plant-derived chemical compounds to color their feathers, legs and beaks. Photo: Flickr user longhorndave

Pop quiz: Why are flamingos pink?

If you answered that it’s because of what they eat—namely shrimp—you’re right. But there’s more to the story than you might think.

Animals naturally synthesize a pigment called melanin, which determines the color of their eyes, fur (or feathers) and skin. Pigments are chemical compounds that create color in animals by absorbing certain wavelengths of light while reflecting others. Many animals can’t create pigments other than melanin on their own. Plant life, on the other hand, can produce a variety of them, and if a large quantity is ingested, those pigments can sometimes mask the melanin produced by the animal. Thus, some animals are often colored by the flowers, roots, seeds and fruits they consume

Flamingos are born with gray plumage. They get their rosy hue pink by ingesting a type of organic pigment called a carotenoid. They obtain this through their main food source, brine shrimp, which feast on microscopic algae that naturally produce carotenoids. Enzymes in the flamingos’ liver break down the compounds into pink and orange pigment molecules, which are then deposited into the birds’ feathers, legs and beaks. If flamingos didn’t feed on brine shrimp, their blushing plumage would eventually fade.

In captivity, the birds’ diets are supplemented with carotenoids such as beta-carotene and and canthaxanthin. Beta-carotene, responsible for the orange of carrots, pumpkins and sweet potatoes, is converted in the body to vitamin A. Canthaxanthin is responsible for the color of apples, peaches, strawberries and many flowers.

Shrimp can’t produce these compounds either, so they too depend on their diet to color their tiny bodies. Flamingos, though, are arguably the best-known examples of animals dyed by what they eat. What others species get pigment from their food? Here’s a quick list:

Northern cardinals and yellow goldfinches: When these birds consume berries from the dogwood tree, they metabolize carotenoids found inside the seeds of the fruit. The red, orange and yellow pigments contribute to the birds’ vibrant red and gold plumage, which would fade in intensity with each molt if cardinals were fed a carotenoid-free diet.

Salmon: Wild salmon consume small fish and crustaceans that feed on carotenoid-producing algae, accumulating enough of the chemical compounds to turn pink. Farmed salmon are fed color additives to achieve a deeper shades of red and pink.

Nudibranchs: These shell-less mollusks absorb the pigments of their food sources into their normally white bodies, reflecting the bright colors of sponges and cnidarians, which include jellyfish and corals.

Canaries: The birds’ normal diet doesn’t alter the color of its yellow feathers, but they can turn a deep orange if they regularly consume paprika, cayenne or red pepper. These spices each contain multiple carotenoids responsible for creating and red and yellow.

Ghost ants: There’s not much more than meets the eye with ghost ants: these tropical insects get their name from their transparent abdomens. Feed them water mixed with food coloring and watch their tiny, translucent lower halves fill up with brilliantly colored liquid.

Ghost ants sip sugar water with food coloring, which is visible in their transparent abdomens. Photo by Mohamed Babu/Solent News/Rex F/AP Images

Humans: Believe it or not, if a person eats large quantities of carrots, pumpkin or anything else with tons of carotenoids, his or her skin will turn yellow-orange. In fact, the help book Baby 411 includes this question and answer:

Q: My six-month-old started solids and now his skin is turning yellow. HELP!

A: You are what you eat! Babies are often first introduced to a series of yellow vegetables (carrots, squash, sweet potatoes). All these vegetables are rich in vitamin A (carotene). This vitamin has a pigment that can collect harmlessly on the skin, producing a condition called carotinemia.

How to tell that yellow-orange skin isn’t an indication of  jaundice? The National Institutes of Health explain that “If the whites of your eyes are not yellow, you may not have jaundice.”